Characterization and properties of in situ emulsion polymerized poly(methyl methacrylate) graphene
Materials Characterization
Materials Characterization Materials characterization is a crucial aspect of materials science and engineering. It involves the study of the properties and behavior of materials, including their physical, chemical, mechanical, and thermal properties. The characterization of materials is essential for the development of new materials, as well as for the optimization of existing ones. In this response, I will discuss the importance of materials characterization from various perspectives. From a scientific perspective, materials characterization is essential for understanding the fundamental properties of materials. By studying the properties of materials at the atomic and molecular level, scientists can gain insights into how materials behave and interact with their environment. This knowledge can then be used to develop new materials with specific properties or to optimize existing materials for specific applications. For example, the study of the electronic properties of materials has led to the development of new electronic devices, such astransistors and solar cells. From an engineering perspective, materials characterization is crucial for the design and development of new materials and products. By understanding the properties of materials, engineers can select the most suitable materials for a particular application and design products that are optimized for performance and durability. For example, the development of advanced composites for use in aerospace applications requires a detailed understanding of the mechanical properties of the materials, including their strength, stiffness, and fatigue resistance. From a commercial perspective, materials characterization is essential for the development of new products and technologies that can be brought to market. By understanding the properties of materials, companies can develop products that are optimized for performance, cost, and durability. For example, the development of new materials for use in the automotive industry has led to the development of lightweight, fuel-efficient vehicles that are more environmentally friendly and cost-effective. From an environmental perspective, materials characterization is essential for the development of sustainable materials and technologies. By understanding the properties of materials, researchers can develop materials that are more environmentally friendly and sustainable, reducing the impact of human activities on the environment. Forexample, the development of biodegradable materials for use in packaging and other applications has the potential to reduce the amount of waste generated by human activities. From a societal perspective, materials characterization is essential for the development of new technologies that can improve the quality of life for people around the world. By understanding the properties of materials, researchers can develop new medical devices, renewable energy technologies, and other technologies that can help address some of the world's most pressing problems. For example, the development of new materials for use in medical implants has the potential to improve the quality of life for people with chronic illnesses and injuries. In conclusion, materials characterization is a crucial aspect of materials science and engineering that has implications for science, engineering, commerce, the environment, and society as a whole. By understanding the properties of materials, researchers and engineers can develop new materials and technologies that can improve the quality of life for people around the world. As such, materials characterization will continue to be an essential area of research and development in the years to come.。
Characterization and magnetic properties of Fe70Co30 alloy nanowire
Characterization and magnetic properties of Fe70Co30 alloy nanowire arraysG. H. Yue, L. S. Wang, X. Wang, Y. Z. Chen, and D. L. PengCitation: J. Appl. Phys. 105, 074312 (2009); doi: 10.1063/1.3103775View online: /10.1063/1.3103775View Table of Contents: /resource/1/JAPIAU/v105/i7Published by the American Institute of Physics.Additional information on J. Appl. Phys.Journal Homepage: /Journal Information: /about/about_the_journalTop downloads: /features/most_downloadedInformation for Authors: /authorsCharacterization and magnetic properties of Fe70Co30alloy nanowire arraysG.H.Yue,L.S.Wang,X.Wang,Y.Z.Chen,and D.L.Peng a͒Department of Materials Science and Engineering,Research Center of Materials Design and Applications,Xiamen University,Xiamen361005,People’s Republic of China͑Received6November2008;accepted18February2009;published online7April2009͒Highly ordered arrays of parallel Fe70Co30nanowires with a diameter of about50nm and a lengthup to about several tens of micrometers were synthesized by two electricalfields in an anodizedaluminum oxidefilm.The magnetic properties in the temperature range from5to300K werestudied.When the appliedfield is along the long axis,the temperature dependence of coercivity ofFe70Co30nanowire arrays shows a linear decrease with temperature increasing,which can beunderstood by a phenomenological nucleate model.©2009American Institute of Physics.͓DOI:10.1063/1.3103775͔I.INTRODUCTIONIn recent years,a great deal of progress has been made inthe synthesis of various nanostructures with controllablemorphology and properties,including one dimensional struc-ture such as nanowires and nanorods.1–7Those nanowiresand nanorods can be also used as building blocks in forminganisotropic nanostructured materials and devices such ashigh density data storage devices based on domain-wallmotion.5Morphological control has also been reported fornanowires and nanorods of semiconductors,8metals,9metaloxides,10,11and metal sulfide.2,4,6,12,13However,the synthesisof soft magnetic nanowires and nanorods with required ge-ometry and composition is still a challenge.Recently,different groups have tried to produceFe͑1−x͒Co x nanowires with different stoichiometric propor-tions.Most producing methods used templates such as an-odic aluminum oxide͑AAO͒templates2,4,6,12or metal stepedges.14However,the nanowires generated by these tech-niques exhibit amorphouslike materials on their surface͑e.g.,carbon and oxides͒.15In addition,the nanowires werepolycrystalline.2,12Other approaches such as the thermal de-composition of Fe and Co carbonyls in the presence ofstrong magneticfields resulted in the creation of polycrystal-line FeCo nanowires.16Circumventing these problems,thepulsed electrodeposition was used to promote the formationof single crystalline nanowires.II.EXPERIMENTALThe arrays of Fe70Co30nanowires have been prepared bypulsed electrodepositing Fe and Co into AAO templates.Thepreparation of AAO templates has been described elsewherein detail.2In this experiment,the high pure Al foils ͑99.999%͒were annealed at500°C for about48h,then anodized at40V͑dc͒in0.3M H2C2O4aqueous solution at0°C for1h.After the porous templates were removed,thesecond anodized step was performed under the same condi-tions as above.Mixture aqueous solution which containsFeSO4·7H2O,CoSO4·7H2O,H3BO4,and ascorbic acid was used for electrodeposition,and the Fe2+:Co2+ion ratio was adjusted to7:3in the baths.The p H value of the electrolyte maintained at about3.0.The electrodeposition was com-pletely conducted by a pulsed electrical source at50Hz and 10V͑ac͒,and the electrodeposition time was5min using graphite as the counterelectrode.After deposition,samples were kept in pure alcohol solution to avoid oxidation.For convenience,the nanowire arrays with AAO were removed from residual Al substrate by saturated aqueous solution of HgCl2before x-ray diffraction͑XRD͒and magnetic proper-ties measurement were performed.The nanowires were lib-erated by dissolving AAO templates in NaOH aqueous solu-tion before the observation with a transmission electron microscope͑TEM͒.III.RESULT AND DISCUSSIONThe typical XRD pattern of the sample which was etched for5h is shown in Fig.1.The presence of broad peaks can be ascribed to the Fe70Co30body-centered-cubic ͑bcc͒alloy͑space group Im3m͑229͒and lattice parameter a=2.85Å͒.The peaks at2values of44.658°,66.870°,and98.506°correspond to͑110͒,͑200͒,and͑220͒crystal planes of the crystalline Fe–Co alloy͑JCPDS49-1567͒,respec-tively.The cell constant of Fe70Co30is calculated as a =0.2847nm,which is in agreement with the reported values of a=0.285nm͑Ref.17͒for particles of the same composi-tion.The microstructures of Fe70Co30nanowires are very dif-a͒Author to whom correspondence should be addressed.Electronic mail:dlpeng@.Tel.:86-592-2180155.FAX:86-592-2180155.FIG.1.XRD pattern of the FeCo nanowire arrays after etching time of5h.JOURNAL OF APPLIED PHYSICS105,074312͑2009͒0021-8979/2009/105͑7͒/074312/5/$25.00©2009American Institute of Physics105,074312-1ferent from those of bulk Fe–Co alloy.In the XRD pattern of nanowire arrays,the peak of Fe 70Co 30͑110͒is very strong,which indicates that the nanowires have a bcc structure with ͑110͒preferred orientation rather than bcc-FeCo ͑100͒pre-ferred in the Fe–Co bulk alloy.The sharp and narrow ͑110͒peaks indicate that the nanowires are highly crystalline and consist of only a single compositional phase.Figure 2͑a ͒shows a typical scanning electron micros-copy ͑SEM ͒micrograph of the AAO template,which was anodized in 0.3M H 2C 2O 4aqueous solution at 0°C and a voltage of 40V ͑dc ͒.We can see that the AAO template has almost arranged the pore arrays with the average pore diam-eter about 50nm and the interpore distance about 20nm.Figures 2͑b ͒–2͑d ͒show SEM images of Fe 70Co 30nanowires grown in AAO template.These photographs show that the nanowires are uniformly distributed,highly ordered,and par-allel to each other.Few microscopic defects are found in these wires.Figure 2͑b ͒is a planform,from which we can find several clusters of nanowires.The clusters can result from the situation that the nanowires are uncovered out of the framework of the AAO template freestanding incom-pletely.When the top alumina of the AAO template is dis-solved away,the nanowires embedded in the template are released gradually and incline to agglutinate together.It is conceivable that the surface energy of the nanowires causes this interesting phenomenon.Figure 2͑b ͒also shows that Fe 70Co 30nanowires are uniform,highly ordered,and abun-dant in the large area.Figures 2͑c ͒and 2͑d ͒reveal a cross section where the alumina matrix of the AAO template has been partially dissolved away.It can be seen that the nano-wires that were deposited inside the nanochannel of the AAO template are parallel,uniformly distributed,and tidily aligned.It is correlative to that the AAO template had a series of densely parallel nanoholes arranged in a hexagonal fashion.From these figures it can be estimated that the aver-age length of these nanowires is about 20m.It is corre-sponds with the thickness of the AAO template used.At the same time the outside diameters of these wires are about 50nm,which are equivalent to the pore diameter of the tem-plate membrane.TEM images of Fe 70Co 30nanowires formed in the AAO template are shown in Figs.3͑a ͒and 3͑b ͒.Figure 3͑a ͒shows that the Fe 70Co 30nanowires cross and overlap with each other.Figure 3͑b ͒shows that the diameter of the Fe 70Co 30nanowires is about 40nm;it is approximately equal to the diameter of the nanochannels of the employed AAO tem-plate.These nanowires distribute uniformly,which indicates that the alumina matrix is dissolved completely.The high resolution TEM ͑HRTEM ͒image shows the lattice fringes in Fig.3͑c ͒;the layer spacing obtained from the lattice fringes in the HRTEM image is about 2Å,corresponding to d ͑110͒of the bcc Fe 70Co 30.The HRTEM observation reveals that the Fe 70Co 30nanowire grows along the ͑110͒direction.The selected area electron diffraction ͑SAED ͒pattern of Fig.3͑d ͒shows that the Fe 70Co 30nanowire of our sample is a single crystal nanostructure.It is consistent with our XRD results.Energy dispersive spectrometer analysis reveals that the product is composed of iron and sulfur,and the ratio of co-balt atom and Fe atom is 30.32:69.68which just accords with the stoichiometric ratio of Fe 70Co 30.It indicates that the essential component of the product is Fe 70Co 30,and it corre-sponds to the Fe 2+:Co 2+ion ratio that was adjusted as 7:3in the baths at the experimental process.The magnetic properties are measured with the super-conducting quantum interference device ͑SQUID ͒͑MPMS XL ͒magnetometry.All the magnetic properties were mea-sured with the Fe 70Co 30nanowires in self-assembled arrays with AAO template support.The samples electrodeposited in dc conditions exhibit perpendicular magnetic anisotropy,with saturation fields out-of-plane ͓the applied magnetic field perpendicular to substrate and parallel ͑ʈ͒to the long axis of nanowires ͔orientation much bigger than in the correspond-ing in-plane ͓the applied magnetic field perpendicular ͑Ќ͒to the long axis of nanowires ͔orientation,as can be seen in Fig.4.The perpendicular coercive field is 1584.4Oe at 300K ͓in Fig.4͑a ͔͒which obviously changes compared to the 2054.3Oe at 5K ͓in Fig.4͑b ͔͒of the paring to the magnetization data for the in-plane field orientation,it can be noticed that the in-plane coercive field is 625.7Oe at 300KFIG.2.SEM images of AAO template and Fe 70Co 30nanowire arrays.͑a ͒Typical SEM image of AAO template.͑b ͒The top view in low magnifica-tion.͓͑c ͒and ͑d ͔͒SEM image of a typical crosssection.FIG.3.TEM images of AAO template and Fe 70Co 30nanowire arrays.͑a ͒The sample was etched for 5h.͑b ͒The Fe 70Co 30nanowires with a diameter of about 40nm.͑c ͒The HRTEM image of the Fe 70Co 30nanowires in ͑b ͒.͑d ͒The SAED pattern taken from a single nanowire in ͑b ͒.and 682.1Oe at 5K.It is a great change in the in-plane coercive field of the paring the hysteresis loops between the field being parallel and perpendicular to the long axis for the sample,it was found that the easy axis of nano-wires is parallel to its long axis in spite of their different structures.This is because of the strong shape anisotropy.As expected for the applied field parallel to the long axis of nanowires,the hysteresis loops are relatively square ͑square ratio about 0.9͒,whereas when the applied field is perpen-dicular to the long axis of nanowires,the hysteresis loops are sheared ͑square ratio about 0.1͒.It is evidently seen from the features that the easy magnetization direction of nanowires is along the nanowire axes,which suggests that the overall magnetic anisotropy is dominated by the shape anisotropy in Fe 70Co 30nanowires themselves.Figure 5shows the temperature ͑T ͒dependence of H of the typical Fe 70Co 30samples,with the applied field being out of plane.It can be seen that the H is nearly linear over a temperature range of 5–300K.This tendency is in contrast with a relationship of H c with T 1/2in the models of nucle-ation due to the thermal activation.Therefore,there is a fun-damental problem about how to understand the linear rela-tionship of H c with T .It is well known that changing the intrinsic magnetic parameters usually influences the temperature on the magne-tization reversal,such as the saturated magnetization ͑M s ͒and the magnetocrystalline anisotropy constant.Considering that the accurate mass of nanowires could not be obtained,the temperature dependence of magnetization ͑M ͒with asaturated field is given in Fig.6.In Fig.6,the M decreases with temperature increasing and obeys the T 3/2rule.Since the nanowire mass does not depend on the temperature,the T dependence of M will show the correct temperature depen-dence of M s ,which indicates that M s can be expressed as 18M s ͑T ͒=M s ͑0͒͑1−CT 3/2͒.͑1͒Here M s ͑T ͒and M s ͑0͒are the values at temperatures of T and 0K,respectively.The electron diffraction results show that the nanowire arrays are single crystalline and we thought that the shape anisotropy makes the main contribution;there-fore,a major contribution from the magnetocrystalline aniso-tropy would not be expected.Figure 5shows that,with the temperature increasing from 5to 300K,the coercivity de-creases by about 30%for Fe 70Co 30nanowire arrays,while the saturated magnetization decreases by only about 28%.This indicates that there is another more important factor influencing the temperature dependence of coercivity.Considering the large shape anisotropy and demagneti-zation energy,the magnetic moments for the domains in the nanowires should be parallel or antiparallel to the long axis.Assuming two stable magnetic states,moments “up”and “down,”corresponding to the parallel and antiparallelstates,FIG.4.Normalized SQUID magnetometry data for dc electrodeposited Fe 70Co 30nanowire array samples in both field orientations ͑a ͒at 300K and ͑b ͒at 5K.FIG.5.Temperature dependence of coercivity ͑H ͒of Fe 70Co 30nanowire arrays.Solid stars denote the measured data.Solid lines are linear fitting results of Eq.͑3͒with temperature being independent of M s .The dotted lines are the fitting results of Eq.͑4͒with M s ͑T ͒changing with temperature at T 3/2.FIG.6.The temperature ͑T ͒dependence of M with a saturated field parallel to the long axis of the nanowire arrays.the nanowire system could be considered as a bistable system.19The two states are separated by an energy barrier. As the temperature increases,some magnetic moments will overcome the energy barrier and the magnetization reverses. The result is similar to that of an equivalent appliedfield to reverse the magnetization.Of course,the thermalfluctua-tions will also cause the magnetization reversal.The temperature dependence of coercivity can be under-stood based on the above bistable-state thermalfluctuation model.Assume that the magnetization reversal started from a reversal magnetization nucleus with the activation volume v. At the coercivefield,the energy barrier involved in the mag-netization reversal is expressed by20E0+H c ץEץH=25k B T,͑2͒where E0is thefield independent part of E.ץE/ץH is related to the magnetic viscosity coefficient,and k B and T are the Boltzmann constant and temperature,respectively.During the magnetization reversal process,two energy terms are ex-pected to contribute to the energy barrier E0,that is,the domain-wall energy and the magnetostatic energy.Since nucleation of a singledomain wall at the end of the wire leads to a smaller energy barrier,21the domain-wall energy can be derived by E p=␥s,where s is the surface of the acti-vation volume and␥represents the energy density of the domain wall.The magnetostatic energy E d=4␣M s2v,where ␣is a phenomenological parameter and M s is the saturation magnetization.Thus,H c=4␣M s−␥sv M s−25k B Tv M s.͑3͒The activation volume v is proportional toͱA/K eff and␥=4ͱAK eff,22where A is the exchange stiffness constant.The exchange stiffness constant varies with S2in molecularfield theory.S is the spin,and hence A is expected to vary with M s2.The K eff is the effective anisotropy constant.In the Fe70Co30nanowire array system,the shape anisotropy makes the main contribution on K eff.We assume that it is similar to a uniaxial anisotropy and K eff is thus proportional to M s2.19If we assume that M s is a constant at low temperature due to the high Curie temperature,␥and v are independent of the temperature,which means that coercivity is linearly dependent on temperature.Thefitting result for the Fe70Co30 nanowire arrays is shown in Fig.5,with the saturation mag-netization M s derived from the experiment dates of Fe70Co30. It can be found that the experimental results of coercivity agree well with the linear temperature dependence predicted by Eq.͑3͒.Since M s changes by about28%in the temperature range of5–300K,we now consider the influence of M s to Eq.͑3͒.The second term␥s/v M sϰ4sͱAK eff/ͱA/K eff M s =kM s;thus Eq.͑3͒becomesH c=KM s͑T͒−25k B Tv M s͑T͒,͑4͒where K is another phenomenological parameter.M s͑T͒is determined by Eq.͑1͒.Thefitting result by Eq.͑4͒is also shown in Fig.5,in which the M s͑0͒derived from the bulk materials and the parameter C in Eq.͑1͒is derived byfitting the experimental data in Fig.6.It can be found that the fitting result is still perfect with the experimental data.The coercivity is nearly linear with temperature in spite of the T3/2law of saturated magnetization.This result indicates that the temperature dependence of M s has a minor effect on coercivity,and about28%of the changes to M s will not obviously change the linear temperature dependence of the coercivity.The reason for this result is that the decreasing of M s will help more magnetic moments reverse and thus lead to a larger activation volume.It is worth noting that the model predicted by Eq.͑3͒is different from the actual nucle-ation mode.It is only a phenomenological model to interpret the results of hard magnetic materials.20IV.CONCLUSIONIn conclusion,we have developed a novel method to synthesize cobalt disulfide nanowire arrays.The Fe70Co30 nanowires have apparently continuous,parallel,and ordered modality.The diameter of the cobalt disulfide nanowires is about50nm and the SAED pattern shows that the product is single crystalline.The hysteresis loops at various tempera-tures are studied.The coercivity with the appliedfield along the long axis linearly decreases with temperature increasing, which can be interpreted by a phenomenological nucleate model discussed above.ACKNOWLEDGMENTSThis work was partially supported by the National Out-standing Youth Science Foundation of China͑Grant No. 50825101͒and the National Natural Science Foundation of China͑Grant No.50671087͒.One of the authors͑D.L. Peng͒acknowledges the Minjiang Chair Professorship Pro-gram released by Fujian Province of PR China forfinancial support.1A.I.Hochbaum,R.Chen,R.D.Delgado,W.Liang,E.C.Garnett,M. Najarian,A.Majumdar,and P.Yang,Nature͑London͒451,163͑2008͒. 2G.H.Yue,P.X.Yan,J.Z.Liu,X.Y.Fan,and R.F.Zhuo,Appl.Phys. Lett.87,262505͑2005͒.3S.Sun,C.B.Murray,D.Weller,L.Folks,and A.Moser,Science287, 1989͑2000͒.4G.H.Yue,P.X.Yan,X.Y.Fan,M.X.Wang,D.M.Qu,D.Yan,and J.Z. Liu,J.Appl.Phys.100,124313͑2006͒.5L.Thomas,M.Hayashi,X.Jiang,R.Moriya,C.Rettner,and S.S.P. Parkin,Nature͑London͒443,197͑2006͒.6G.H.Yue,P.X.Yan,L.S.Wang,W.Wnag,Y.Z.Chen,and D.L.Peng, Nanotechnology19,195706͑2008͒.7R.P.Cowburn,Nature͑London͒448,544͑2007͒.8K.Yong,Y.Sahoo,M.T.Swihart,and P.N.Prasad,J.Phys.Chem.C111, 2447͑2007͒.9L.Gou and C.J.Murphy,Chem.Mater.17,3668͑2005͒.10G.H.Yue,P.X.Yan,D.Yan,D.M.Qu,X.Y.Fan,M.X.Wang,and H. T.Shang,J.Cryst.Growth294,385͑2006͒.11J.Wu,Y.Lee,H.Chiang,and D.K.Wong,J.Phys.Chem.B110,37͑2006͒.12G.H.Yue,P.X.Yan,X.Y.Fan,M.X.Wang,D.M.Qu,Z.G.Wu,C.Li,and D.Yan,Electrochem.Solid-State Lett.10,D29͑2007͒.13G.H.Yue,P.X.Yan,D.Yan,X.Y.Fan,M.X.Wang,D.M.Qu,and J.Z. Liu,Appl.Phys.A:Mater.Sci.Process.84,409͑2006͒.14J.P.Pierce,E.W.Plummer,and J.Shen,Appl.Phys.Lett.81,1890͑2002͒.15P.S.Fodor,G.M.Tsoi,and L.E.Wenger,J.Appl.Phys.91,8186͑2002͒. 16Q.F.Zhan,Z.Y.Chen,D.S.Xue,F.S.Li,H.Kunkel,X.Z.Zhou,R. Roshko,and G.Williams,Phys.Rev.B66,134436͑2002͒.17Joint Committee on Powder Diffraction Standards Diffraction Data File No.49-1567,1991.18C.Herring and C.Kittel,Phys.Rev.81,869͑1951͒.19B.Giorgio,Hysteresis in Magnetism(For Physics,Materials Scientists, and Engineers)͑Academic,New York,1998͒.20D.Givord,P.Tenaud,and T.Viadieu,IEEE Trans.Magn.24,1921͑1988͒. 21J.E.Knowles,J.Magn.Magn.Mater.61,121͑1986͒.22H.B.Braun,Phys.Rev.B50,16501͑1994͒.。
Advanced Materials Characterization
Advanced Materials CharacterizationAdvanced Materials Characterization is a field that plays a crucial role in the development and understanding of various materials used in industries such as aerospace, automotive, electronics, and healthcare. This discipline involves the use of various techniques and tools to analyze and characterize the properties and behavior of materials at the microscopic and macroscopic levels. In this response, I will discuss the importance of advanced materials characterization from multiple perspectives. From a scientific standpoint, advanced materials characterization provides valuable insights into the structure and properties of materials. By studying the composition, crystal structure, and defects in materials, researchers can gain a deeper understanding of their behavior and performance. This knowledge is essential for designing new materials with enhanced properties or improving the performance of existing materials. For example, by characterizing the microstructure of a metal alloy, scientists can determine its mechanical strength, corrosion resistance, and thermal stability, which are critical factors in industries such as aerospace and automotive. From an industrial perspective, advanced materials characterization is essential for quality control and ensuring the reliability of materials used in various applications. By characterizing the properties of materials, manufacturers can verify if they meet the required specifications and standards. This is particularly important in industries such as healthcare, where the use of substandard materials can have serious consequences for patient safety. By employing advanced characterization techniques such as scanning electron microscopy and X-ray diffraction, manufacturers can detect any defects or impurities in materials and take corrective actions before the final product is released. From an economic point of view, advanced materials characterization can contribute to the growth and competitiveness of industries. By developing new materials with improved properties, companies can gain a competitive edge in the market. For example, the development of lightweight and high-strength materials has revolutionized the aerospace industry, enabling the production of more fuel-efficient aircraft. Furthermore, advanced characterization techniques can help optimize manufacturing processes, leading to cost savings and increased productivity. From an environmental perspective, advanced materialscharacterization can contribute to the development of sustainable materials and technologies. By studying the environmental impact of materials throughout their life cycle, researchers can identify ways to reduce their carbon footprint and enhance their recyclability. For instance, by characterizing the degradation behavior of biodegradable polymers, scientists can design materials that break down more efficiently in composting facilities, reducing the burden on landfills. Additionally, advanced characterization techniques can help identify and mitigate the environmental risks associated with the use of certain materials, such as heavy metals or toxic chemicals. From a societal standpoint, advanced materials characterization has the potential to improve various aspects of our daily lives. For example, in the field of healthcare, the development of advanced materials for medical implants has revolutionized patient care. By characterizing the biocompatibility and mechanical properties of materials, researchers can design implants that are not only safe but also provide better functionality and longevity. Similarly, in the field of electronics, advanced materials characterization has enabled the development of smaller, faster, and more energy-efficient devices, leading to advancements in communication, computing, and entertainment. In conclusion, advanced materials characterization is a multidisciplinary field that is of great importance from scientific, industrial, economic, environmental, and societal perspectives. By providing insights into the structure and properties of materials, it enables the development of new materials with enhanced properties, ensures the quality and reliability of materials used in various applications, contributes to economic growth and competitiveness, promotes the development of sustainable materials and technologies, and improves various aspects of our daily lives. As such, the advancements in materialscharacterization techniques and tools are crucial for the continued progress and innovation in various industries.。
Materials Characterization
Materials Characterization Materials characterization is an essential aspect of scientific research and industrial applications, providing valuable insights into the properties and behavior of various materials. This process involves analyzing the structure, composition, and properties of materials at the micro and nano scales, allowing researchers to understand their performance and potential applications. Byutilizing a range of techniques such as microscopy, spectroscopy, and diffraction, scientists can gain a comprehensive understanding of the materials they are studying. The field of materials characterization has a rich historical background, dating back to the early days of scientific inquiry. In the 17th century, Robert Hooke used a microscope to observe the structure of cork, laying the foundation for the field of microscopy. Over the centuries, advancements in technology have led to the development of a wide range of characterization techniques, from X-ray diffraction to electron microscopy. These tools have revolutionized our understanding of materials and have paved the way for numerous technological innovations. One of the key challenges in materialscharacterization is the interpretation of data and the identification of relevant information. Different researchers may have varying perspectives on how to analyze and interpret results, leading to a diverse range of opinions within thescientific community. For example, some scientists may prioritize certain properties of a material over others, depending on their specific research goals. By considering multiple perspectives, researchers can gain a more comprehensive understanding of the materials they are studying. Case studies and examples play a crucial role in illustrating key points in materials characterization. For instance, researchers studying the mechanical properties of a new composite material may use scanning electron microscopy to analyze its microstructure and identify potential weaknesses. By correlating these findings with mechanical testing data, scientists can gain valuable insights into the performance of the material and make informed decisions about its future applications. Case studies provide real-world examples of how materials characterization can impactscientific research and technological development. Despite its numerous benefits, materials characterization also has its drawbacks. One of the main challenges isthe high cost associated with advanced characterization techniques, which canlimit access for researchers with limited funding. Additionally, the complexity of some characterization methods may require specialized training, making itdifficult for researchers to effectively utilize these tools. By addressing these challenges and investing in training and infrastructure, the scientific community can overcome these limitations and continue to advance the field of materials characterization. In conclusion, materials characterization plays a vital role in scientific research and technological development, providing valuable insightsinto the properties and behavior of materials. By analyzing the historical background, different perspectives, case studies, benefits, and drawbacks of materials characterization, we can gain a comprehensive understanding of this field. Moving forward, it is essential to invest in training and infrastructure to overcome the challenges associated with materials characterization and ensure continued progress in this important area of study.。
Postsynthesis, Characterization, and Catalytic Properties
Postsynthesis,Characterization,and Catalytic Properties in Alkene Epoxidation of HydrothermallyStable Mesoporous Ti-SBA-15Peng Wu and Takashi Tatsumi*Division of Materials Science&Chemical Engineering,Graduate School of Engineering, Yokohama National University,79-5Tokiwadai,Hodogaya-ku,Yokohama240-8501,JapanTakayuki Komatsu and Tatsuaki YashimaDepartment of Chemistry,Tokyo Institute of Technology,2-12-1Ookayama,Meguro-ku,Tokyo152-8551,JapanReceived September25,2001.Revised Manuscript Received January11,2002Mesoporous Ti-SBA-15has been postsynthesized by the titanation of pure silica SBA-15 in glycerol with the assistance of quaternary organic ammonium hydroxides,and has been extensively characterized by various techniques to investigate the mesostructural and catalytic properties,and the chemical nature of the incorporated Ti species,in comparison with those of Ti-MCM-41.To incorporate tetrahedral Ti species into the silica walls of SAB-15,the titanation needs to be carried out at elevated temperature and using an optimum amount of organic ammonium hydroxide.Ti-SBA-15samples with a Si/Ti ratio ranging from 376to16are successfully prepared with the retention of hexagonal mesostructure by elaborately conducting the titanation.The nature of the Ti species depends greatly on the Ti loading.At Si/Ti ratios higher than50,the Ti species are mainly tetrahedrally coordinated in isolated states,while poorly dispersed Ti species of octahedral coordination are formed at higher Ti incorporation levels;however,no anatase phase is formed in all cases.The IR band at948cm-1due to Si-O-Ti bonds can be used to characterize the tetrahedral Ti species in mesoporous materials,but the techniques of dehydration or trimethylsilylation should be adopted to get rid of the influence of silanol groups.In an actual catalytic reaction, Ti-SBA-15exhibits not only extremely high thermal stability but also outstanding endurance against Ti leaching not observed for Ti-MCM-41.Ti-SBA-15is thus presumed to be a promising liquid-phase oxidation catalyst.IntroductionMesoporous materials,having uniform mesopores and an extremely high specific surface area,have received extensive attention from researchers in the past decade because of their potential applications as catalysts, adsorbents for large organic molecules,and guest-host chemical supporters.1-4From the viewpoint of catalysis, many efforts have been made to introduce metal ions into the most representative mesoporous silica,MCM-41,by direct synthesis or postsynthesis methods.5-10Compared to the crystalline microporous materials,the mesoporous catalysts suffer two major disadvantages, that is,low intrinsic catalytic activity due to the amorphous nature of the pore walls and poor hydro-thermal and mechanical stability due to the high hydrophilicity derived from abundant surface silanol groups.11To overcome the former weakness,efforts have been made to introduce zeolite-like crystalline orders into the mesoporous materials.For example,with the aid of tetrapropylammonium ions,Al-containing MCM-41is reported to partially crystallize to form ZSM-5precur-sors within the mesopore walls,and then exhibits an enhanced catalytic activity for cumene cracking.12Par-tially dissolving zeolite in carefully controlled basic media and then assembling this zeolite source into mesostructures or pillaring lamellar zeolite with sur-factant to construct a micro-mesoporous hybrid struc-ture is an alternative way.13-15However,it seems that*To whom correspondence should be addressed.Phone:+81-45-339-3943.Fax:+81-45-339-3941.E-mail:ttatsumi@ynu.ac.jp.(1)Kresge C.T.;Leonowicz,M.E.;Roth,W.J.;Vartuli,J.C.;Beck, J.S.Nature1992,359,710.(2)Beck,J.S.;Vartuli,J.C.;Roth,W.J.;Leonowicz,M.E.;KresgeC.T.;Schmitt,K.D.;Chu,C.T-W.;Olson,D.H.;Sheppard,E.W.; McCullen,S.B.;Higgins,J.B.;Schlenker,J.L.J.Am.Chem.Soc. 1992,114,10834.(3)Sayari,A.Chem.Mater.1996,8,1840.(4)Corma,A.Chem.Rev.1997,97,2373.(5)Maschmeyer,T.;Rey,F.;Sanker,G.;Thomas,J.M.Nature 1995,378,159.(6)Corma,A.;Forne´s,V.;Navarro,M.T.;Pe´rez-Pariente,J.J. Catal.1994,148,569.(7)Blasco,T.;Corma,A.;Navarro,M.T.;Pe´rez-Pariente,J.J. Catal.1995,156,65.(8)Koyano,K.A.;Tatsumi,T.Microporous Mater.1997,10,259.(9)Mokoya,R.;Jones,mun.1997,2185.(10)Ryoo,R.;Jun,S.J.;Kim,J.M.;Kim,mun. 1997,2225.(11)Tatsumi,T.;Koyano,K.A.;Tanaka,Y.;Nakata,S.Chem.Lett. 1997,469.(12)Kloetstra,K.R.;van Bekkum,H.;Jansen,J. C.Chem. Commun.1997,2281.1657Chem.Mater.2002,14,1657-166410.1021/cm010910v CCC:$22.00©2002American Chemical SocietyPublished on Web03/12/2002many technical difficulties and limitations still remain in the above approaches.To increase the stability of mesoporous materials, postmodification and a search for more stable structures have been carried out.Trimethylsilylation effectively removes the surface silanols to greatly enhance the hydrophobicity.This enhances the hydrothermal stabil-ity and the catalytic activity especially for Ti-MCM-41-catalyzed liquid-phase oxidation involving water.16,17It is easy to consider the improvement of the stability through controlling the synthesis conditions to achieve an extensive condensation of the silica walls or by discovering new materials that are intrinsically stable. In this meaning,SBA-15,synthesized with triblock copolymer,has thicker walls and uniform mesopores ranging from5to30nm,and then reasonably shows a higher hydrothermal stability than conventional MCM-41.18,19Mesoporous pure silica MSU-G thereafter syn-thesized with novel gemini surfactants is reported to be more hydrothermally stable even than SBA-15 because of a high degree of SiO4unit cross-linking.20 However,to the best of our knowledge,the isomorphous substitution of heteroatoms into MSU-G has not been reported in the open literature so far.On the other hand,several papers concerning the incorporation of Al,Ti,or V into SBA-15have been reported.21-23In the case of Ti-SBA-15,although it can be synthesized directly under microwave hydrothermal conditions,24the postsynthesis method is still over-whelming mainly because SBA-15needs strongly acidic synthesis conditions.To apply Ti-SBA-15to a versatile catalyst in the selective oxidation with peroxide oxidants to produce fine chemicals and pharmaceutical sub-stances,Ti should be incorporated essentially as a tetrahedral species but not as a catalytically inactive anatase phase.Unfortunately,the catalytic data are still not available for the Ti-SBA-15samples either directly synthesized or prepared simply by the incipient-wetness impregnation.Nevertheless,they do not seem to serve as effective epoxidation catalysts because they contain a large amount of anatase especially at high levels of Ti incorporation as evidenced by UV-vis spectra.22,24 Thus,there is still high potential to prepare Ti-SBA-15 with highly qualitative Ti species applicable to liquid-phase oxidation.In the present study,we have postsynthesized hy-drothermally stable Ti-SBA-15of various Ti contents with the assistance of quaternary organic ammonium hydroxide.Various techniques have been used to char-acterize extensively both the pore properties and the Ti states of Ti-SBA-15.The stability against hydrothermal treatment and Ti leaching has been compared between Ti-SBA-15and Ti-MCM-41in the actual catalytic ep-oxidation of alkenes.Experimental SectionSample Preparation.Mesoporous silica SBA-15was hy-drothermally synthesized according to the procedures reported previously.18Triblock copolymer,poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)(PEG-PPG-PEG;average molecular weight5800,Aldrich),was dissolved in deionized water.Tetraethyl orthosilicate(TEOS;Wako)and hydrochloric acid(36wt%,Wako)were then added to the copolymer solution to obtain a homogeneous solution with a molar composition of SiO2/0.017PEG-PPG-PEG/6.55HCl/169 H2O.The resultant solution was heated at308K with stirring for20h and further aged statically at373K for24h.The white solid product(SBA-15)was filtered,washed with deion-ized water,dried,and then calcined at773K for10h.Ti-incorporated SBA-15,designated Ti-SBA,was prepared by the postsynthesis method using tetrabuthyl orthotitanate (95wt%,Wako)as a Ti source.In a typical preparation,a certain amount of TBOT was hydrolyzed in20mL of glycerol (99wt%,Wako)containing0-5mL of quaternary ammonium hydroxide to obtain a homogeneous solution.To the above solution was added1g of SBA-15without any pretreatment, and the mixture was heated statically to induce titanation at 303-393K for20-220h.The amount of TBOT added was varied to give Si/Ti atomic ratios of5.7-200.The quaternary ammonium hydroxides used were tetrapropylammonium hy-droxide(TPAOH;25wt%,TCI),tetraethylammonium hy-droxide(TEAOH;35wt%,Aldrich),and tetrabutylammonium hydroxide(TBAOH;45wt%,TCI).After the titanation,Ti-SBA was filtered and washed with deionized water,and the organic species were burned off at773K for4h.For control experiments,Ti-MCM-41samples,denoted Ti-MCM,with Si/Ti ratios of37-320were hydrothermally synthesized.7The trimethylsilylation of mesoporous materials was carried out using hexamethyldisilazane(HMDS).25After evacuation at473K for2h,1g of powder was added to20mL of anhydrous toluene and1g of HMDS in a flask equipped with a cooling condenser,and the mixture was refluxed for2h to induce the silylation of surface silanols.The silylated product, Ti-SBA-sil or Ti-MCM-sil,was then filtered,washed with acetone,and dried at373K for5h.Characterization Methods.Powder X-ray diffraction (XRD)patterns were recorded on a Rigaku Rint2000diffrac-tometer using Cu K R radiation,and UV-vis spectra were collected on a Shimadzu UV-2400PC spectrophotometer.The amount of Ti was quantified by inductively coupled plasma emission spectrometry(ICP;Rigaku JY38S).N2adsorption measurements at77K were carried out on a Coulter SA3100 volumetric adsorption analyzer after the samples were out-gassed for2h at473K.IR spectra were recorded on a Shimadzu FTIR-8100spectrophotometer using a KBr pellet technique.26Sample diluted in KBr(3wt%)was pressed into a wafer(31.9mg cm-2thickness).The wafer was evacuated at373-773K in a quartz cell sealed with KBr windows.The spectra were collected in absorbance mode after the cell was cooled to room temperature.Catalytic Reaction.The epoxidation of cyclohexene was carried out under vigorous stirring in a50mL glass flask which was heated with an oil bath.In a typical run,10mmol(13)Liu,Y.;Zhang,W.;Pinnavaia,T.J.Am.Chem.Soc.2000,122, 8791.(14)Zhang,Z.;Han,Y.;Zhu,L.;Wang,R.;Yu,Y.;Qiu,S.;Zhao,D.;Xiao,F.S.Angew.Chem.,Int.Ed.2001,40,1258.(15)Cheng,J. C.;Degnan,T. F.;Beck,J.S.;Huang,Y.Y.; Kalyanaraman,M.;Kowalski,J.A.;Loehr,C.A.;Mazzone,D.N.Stud. Surf.Sci.Catal.1999,121,53.(16)Tatsumi,T.;Koyano,K.A.;Igarashi,mun.1998, 325.(17)Koyano,K.A.;Tatsumi,T.;Tanaka,Y.;Nakata,S.J.Phys. Chem.B1997,101,9436.(18)Zhao,D.;Feng,J.;Huo,Q.;Melosh,N.;Fredrickson,G.H.; Chmelka,B.F.;Stucky,G.D.Science1998,279,548.(19)Zhao,D.;Feng,J.;Huo,Q.;Melosh,N.;Chmelka,B.F.;Stucky,G.D.J.Am.Chem.Soc.1998,120,6024.(20)Kim,S.S.;Zhang,W.;Pinnavaia,T.J.Science1998,282,1302.(21)Cheng,M.;Wang,Z.;Sakurai,K.;Kumata, F.;Saito,T.; Komatsu,T.;Yashima,T.Chem.Lett.1999,131.(22)Luan,Z.;Maes,E.M.;van der Heide,P.A.W.;Zhao,D.;Czernuszewicz,R.S.;Kevan,L.Chem.Mater.1999,11,3680.(23)Luan,Z.;Bae,J.Y.;Kevan,L.Chem.Mater.2000,12,3202.(24)Newalkar,B.L.;Olanrewaju,J.;Komarneni,S.Chem.Mater. 2000,13,552.(25)Vansant,E.F.;Van Der Voort,P.;Vroancken,K.C.Stud.Surf. Sci.Catal.1995,93,83.(26)Wu,P.;Tatsumi,T.;Komatsu,T.;Yashima,T.J.Phys.Chem. B2001,105,2897.1658Chem.Mater.,Vol.14,No.4,2002Wu et al.of cyclohexene (99wt %,TCI),10mL of acetonitrile (99.5wt %,Wako)solvent,and 0.05g of catalyst were mixed in the flask and heated to 333K under agitation.The desirable amount of oxidant,TBHP (70wt %,Aldrich)or H 2O 2(30wt %,Wako),was then added to the mixture to start the reaction.After the catalyst powder was removed from the reaction mixture by centrifugal separation,the products were analyzed on a gas chromatograph (Shimadzu GC-14B)with an FID detector.Results and DiscussionPostsynthesis of Ti-SBA-15.Glycerol was chosen as the solvent for introducing Ti into pure silica SBA-15by the postsynthesis method,because it exhibits the advantage of serving as a stabilizing guest molecule due to its high viscosity,12,27and is considered to exert a less destructive effect than water solvent on the hydrother-mally unstable mesoporous structure.Table 1shows the influence of various titanation conditions on the Ti incorporation and the physicochem-ical properties of SAB-15.The effect of the treatment temperature was investigated at a treatment time of 70h,TPAOH/SBA-15liquid-to-solid ratio of 3mL g -1,and Si/Ti atomic ratio of 60(Table 1,nos.1-4).The amount of Ti incorporated into SBA-15was about half of that initially added,and did not change significantly in the range from 303to 393K.On the other hand,the amount of Ti incorporated at 373K increased with increasing treatment time to 70h and showed negligible change after 70h (Table 1,nos.3and 5-7),indicating the Ti incorporation took place slowly only to a low level within 20h.When the treatment temperature and the time were fixed at 373K and 70h,respectively,the relative amount of TPAOH aqueous solution to SBA-15solid was found to significantly influence the absolute amount of Ti incorporated;that is,a lower amount of TPAOH solution resulted in higher Ti incorporation (Table 1,nos.8-11).The use of TEAOH and TBAOH for the titanation resulted in no obvious difference in the Ti amount from that of TPAOH (Table 1,nos.3,12,and 13).Figure 1shows the XRD patterns of the parent SBA-15and three representative Ti-SBA-15samples.All the SBA-15and Ti-SBA-15samples exhibited very similar patterns where three well-resolved diffraction peaks dueto 100,110,and 200reflections were observed.Although a slightly lower intensity of the 100peak was observed for Ti-SBA-15prepared under serious conditions (Figure 1d),the well-retained 110and 200peaks strongly verified that the characteristic hexagonal features were maintained in Ti-SBA-15.N 2adsorption measurements were conducted to fur-ther investigate the structural change upon titanation because the XRD patterns may not be so sensitive as to show a slight textural change.Figure 2A shows N 2adsorption/desorption isotherms for SBA-15and various Ti-SBA-15samples.SBA-15showed a hysteresis loop which typically featured this kind of mesoporous mate-rial.The step of increase in the N 2adsorption amount due to multilayer absorption in the mesopores was observed in a higher pressure region than that of MCM-(27)Doughetry,J.;Iton,L.E.;White,J.W.Zeolites 1995,15,640.Table 1.Effect of Treatment Conditions on Ti Incorporation into SBA-15atitanation condit ionsSi/Ti rationo.sampl e temp (K)time (h)TPAOH/SBA-15(mL g -1)added incorporated BET (m 2g -1)micropore vol b(mL g -1)pore size (nm)1SBA-156830.152 5.82Ti-SBA1303703601016530.085 5.83Ti-SBA2373703601165610.020 5.84Ti-SBA3393703601105130.014 5.85Ti-SBA4373203602696130.031 5.86Ti-SBA53731203601205230.005 5.87Ti-SBA63732203601145050.001 5.88Ti-SBA737370022256540.056 5.89Ti-SBA8373701223410Ti-SBA937370322725540.015 5.811Ti-SBA10373705221264840.003 5.812Ti-SBA11373703c 60955840.016 5.813Ti-SBA12373703d601055420.0135.8a Other conditions:parent SBA-15,1g;glycerol,20mL;25wt %TPAOH,3mL;time,70h.b Calculated from t -plots.c 35wt %TEAOH.d45wt %TBAOH.Figure 1.X-ray diffraction patterns of pure silica SBA-15(a)and Ti-incorporated samples of Ti-SBA2(b),Ti-SBA4(c),and Ti-SBA6(d).For Ti-SBA samples,see Table1.Figure 2.N 2adsorption/desorption isotherms (A)and pore size distributions (B)for pure silica SBA-15(a)and Ti-incorporated samples of Ti-SBA2(b),Ti-SBA3(c),Ti-SBA4(d),and Ti-SBA6(e).For Ti-SBA samples,see Table 1.Alkene Epoxidation of Mesoporous Ti-SBA-15Chem.Mater.,Vol.14,No.4,2002165941,suggesting SBA-15has a larger pore size.24,28The sharpness of the hysteresis loop was maintained for Ti-SBA-15samples (Figure 2,curves b -d).Nevertheless,the sample prepared under severe conditions slightly lost the sharpness of the hysteresis loop (Figure 2,curve e),probably due to partial collapse of the mesostructure.The specific area (BET)and the BJH pore size distribution calculated from the desorption isotherms are summarized in Table 1and Figure 2B,respectively.The BET surface area of SBA-15is generally reported to vary in the range of 500-1000m 2g -1since the porous properties of this kind of mesoporous material are greatly dependent on the synthesis conditions.18,19,29The present SBA-15fell within the surface area range reported in the literature and was thus considered to be qualitatively good.The specific area was lowered by about 30m 2g -1after mild titanation,and further decreased gradually with increasing treatment temper-ature,treatment time,and relative amount of TPAOH solution (Table 1,nos.1-11).This can be reasonably explained in terms of a reduced order of the mesostruc-ture,because SBA-15,although consisting of thick silica walls,is still not hydrothermally stable enough to withstand the titanation treatment.Nevertheless,the average pore size was almost the same and the distri-bution was generally very narrow except for Ti-SBA-15prepared under severe conditions (Figure 2,curve e).Different from mesoporous MCM-41,SBA-15shows both mesoporous and microporous properties which greatly depend on the aging temperature.The presence of micropores has been confirmed either by the carbon replica method or by N 2adsorption measurement using R s -plot and t -plot methods.29-33The t -plot analysis was thus used to estimate the micropore volume in the mesoporous materials.The t -plots were obtained by using a reference isotherm of a nonporous silica as described previously.34As shown in Figure 3a,b,the extrapolation lines of the t -plots passed through the origin for MCM-41and Ti-MCM-41,indicating theylacked micropores.In contrast,SBA-15gave a straight line not passing through the origin (Figure 3c),which was indicative of distinct microporosity.The micropore volume of SBA-15obtained from the intercept of the y -axis accounted for about 15%of its total volume.Ti-SBA-15samples showed t -plots similar in shape to that of SBA-15,but the intercepts approached the origin (Figure 3d,e),indicating gradual disappearance of the micropores.The micropore volumes obtained from the t -plots are listed in Table bining these with the above BET analysis,we would propose that the decrease in the surface area during titanation is principally due to the loss of micropores.Since the micropores are probably generated by penetration of hydrophilic poly(ethylene oxide)chains of triblock copolymer into its thick silica walls,29-33a hydrothermal heating would shrink the silica walls to mend “holes”therein which are mi-cropores.Incorporation of Ti species into the micropores to remove this wall defect may also partially account for the reduced surface area.Both reasons would make Ti-SBA-15mesoporous but lack the bimodal porosity of SBA-15.However,very severe titanation at higher temperatures,for a longer time,and by using a larger amount of TAPOH would not only remove the mi-cropores but also destroy the mesopores as evidenced by a broader pore size distribution (Figure 2,curve e)and greatly reduced BET areas (Table 1,nos.4,7,11).UV -vis spectroscopy was used to characterize the effectiveness of the titanation conditions on the chemical nature and coordination states of the Ti species incor-porated.The bands at 200-230,330,and 260-290nm are usually taken as clear evidence for the isolated framework Ti,anatase Ti(IV)particles,and octahedrally coordinated Ti species with low dispersion,respec-tively.35The band position is thus indicative of the nature of the Ti species.Figure 4depicts the UV spectra of Ti-SBA-15samples prepared under various conditions.Ti-SBA-15obtained by titanation at 303K (Table 1,no.2)showed a main band at 260nm besides the 220nm band,and those prepared at higher temperatures (Table 1,nos.3and 4)exhibited essentially the 220nm band (Figure 4A),although the Ti contents were very similar to those described above.The reaction of the Ti species with the surface silanol groups is suggested to be requisite for Ti incorporation.A certain temperature is presumed to be necessary in crossing the activation energy barrier to cause this reaction to result in isolated Ti species.Titanation at an optimum temperature of 373K re-sulted in incorporation of Ti species almost tetrahedrally coordinated,increasing gradually with time (Figure 4B).The addition of TPAOH retarded the Ti introduction (Table 1,nos.8-11),but effectively controlled the nature of the Ti species as shown by the gradual blue shift of the band from 260to 220nm with increasing TPAOH/solid ratio (Figure 4C).The basic aqueous solution of TPAOH would promote the hydrolysis of TBOT,which then prevents the Ti species from ag-gregating to particles.Nevertheless,too much TPAOH solution added caused structural collapse.Other qua-ternary organic ammonium hydroxides,TEAOH and(28)Gregg,S.J.;Sing,K.S.Adsorption,Surface Area and Porosity ;Academic Press:London,1982.(29)Miyazawa,K.;Inagaki,mun.2000,2121.(30)Kruk,M.;Jaroniec,M.;Ko,C.H.;Ryoo,R.Chem.Mater.2000,12,1961.(31)Jun,S.;Joo,S.H.;Ryoo,R.;Kruk,M.;Jaroniec,M.;Liu,Z.;Ohsuna,T.;Terasaki,O.J.Am.Chem.Soc.2000,122,10712.(32)Ryoo,R.;Hyun,K.C.;Kruk,M.;Antochshuk,V.;Jaroniec,M.J.Phys.Chem.B 2000,104,11465.(33)Imperor-Clere,M.;Davidson,P.;Davidson,A.J.Am.Chem.Soc.2000,122,11925.(34)Bhambhani,M.R.;Cutting,P.A.;Sing,K.S.W.;Turk,D.H.J.Colloid Interface Sci.1972,38,109.(35)Vayssilov,G.N.Catal.Rev.Sci.Eng.1997,39,209.Figure 3.t -plots of N 2adsorption for pure silica MCM-41(a),Ti-MCM-41(b),pure silica SBA-15(c),Ti-SBA2(d),and Ti-SBA3(e).For Ti-SBA samples,see Table 1.1660Chem.Mater.,Vol.14,No.4,2002Wu et al.TBAOH,showed basically the same effectiveness as TPAOH in forming highly dispersed Ti species (Figure 4D).Therefore,perusal of XRD,ICP,N 2adsorption,and UV -vis data leads to the conclusion that Ti-SBA-15containing the tetrahedral Ti species can be optimally postsynthesized by titanation in gycerol at an elevated temperature with organic ammonium hydroxide as a promoting agent for Ti dispersion.A series of Ti-SBA-15samples were thus prepared by varying the Ti content in the starting reaction mixture at the optimum conditions as described above.Table 2shows their physicochemical properties together with those of directly synthesized Ti-MCM-41samples.The amount of Ti incorporated into SBA-15silica decreased from about half to one-fourth of the amount initially added when the Si/Ti ratio of the starting mixture decreased,indicating a decreasing efficiency for Ti incorporation.The absorption band maximum was observed at 220nm in the UV -vis spectra for both Ti-SBA-15and Ti-MCM-41(Figure 5).The band gradually red-shifted to the longer wavelength region with increasing Ti content to result in a new shoulder band around 260nm especially when the Si/Ti ratio was lower than 50.This means octahedral Ti species formed partially within the mesoporous materials at high Ti levels irrespective of the Ti incorporation method (direct or postsynthesis).Nevertheless,no Ti-SBA-15sample showed the band around 330nm due to the anatase phase.The present postsynthesis method is presumed to be effective in achieving high Ti dispersion.IR Spectroscopy Study on Ti-SBA-15and Ti-MCM-41.IR spectroscopy is a useful technique for characterizing the framework Ti species in microporous crystalline titanosilicates such as TS-136and Ti-MOR.37Nevertheless,this method is not so useful for Ti meso-porous materials containing silanols groups or defect sites,7,26because those silanol groups or water molecules adsorbed therein also give a similar band.However,we have recently solved this problem by measuring IR spectra after evacuating the samples in situ at elevated temperatures.26This new technique was applied here to the characterization of Ti-SBA-15with IR spectros-copy.Figure 6shows the IR spectra of pure silica SBA-15and Ti-SBA-15recorded after evacuation at various temperatures.The sample was diluted in KBr pellets (15wt %)to obtain well-resolved and noncutoff bands in the region lower than 1000cm -1.SBA-15showed a band at 968cm -1before evacuation despite the absence of Ti (Figure 6B).However,the band gradually de-creased in intensity with increasing evacuation tem-perature,and was hardly observed after evacuation at 773K.This is a result of removal of adsorbed water and dehydroxylation of silanols as evidenced by the disap-pearance of the broad band at 3200-3600cm -1(Figure 6A).The same 968cm -1band was observed for Ti-SBA-15before evacuation,but the band split into two bands after evacuation at 573K and turned out to be a new band with a maximum adsorption at 948cm -1when evacuation was done at 773K (Figure 6D).These results suggest the 948cm -1band could be assigned to the tetrahedral Ti species in Ti-SBA-15.(36)Bellussi,G.;Rigguto,M.S.Stud.Surf.Sci.Catal.1994,85,177.(37)Wu,P.;Komatsu,T.;Yashima,T.J.Phys.Chem.1996,100,10316.Figure 4.UV -vis spectra for Ti-SBA-15samples prepared by titanation for 70h at different temperatures (A),at 373K for different periods of time (B),with different TPAOH/SBA-15ratios (C),and in various quaternary ammonium hydroxides (D).For detailed titanation conditions,see Table 1.Table 2.Postsynthesized Ti-SBA-15a andHydrothermally Synthesized Ti-MCM-41b with Various TiContents Si/Ti rationo.sample added incorporated BET (m 2g -1)pore size (nm)1Ti-SBA12003762Ti-SBA260116561 5.83Ti-SBA32280524 5.84Ti-SBA417575Ti-SBA51436542 5.86Ti-SBA610277Ti-SBA7720536 5.28Ti-SBA8 5.716515 5.29MCM-411158 2.710Ti-MCM12833201115 3.011Ti-MCM211013012Ti-MCM380761115 3.013Ti-MCM460581060 2.614Ti-MCM5353710412.6aPostsynthesis conditions:parent SBA-15,1g;glycerol,20mL;25wt %TPAOH,3mL;temperature,373K;time,70h.b Hydro-thermal synthesis conditions:see ref7.Figure 5.UV -vis spectra for postsynthesized Ti-SBA-15samples (A)and hydrothermally synthesized Ti-MCM-41samples (B)both with various Si/Ti ratios.For detailed preparation conditions,see Table 2.Alkene Epoxidation of Mesoporous Ti-SBA-15Chem.Mater.,Vol.14,No.4,20021661This assignment was further verified by the IR spectra of SBA-15and Ti-SBA-15after the trimethyl-silylation treatment.The silylation consumes the silanol groups effectively and greatly enhances the hydropho-bicity of mesoporous materials.17As shown in Figure 7,the silylation developed a band at 2975cm -1at-tributed to the C -H stretching vibration of methyl groups,25and greatly decreased the intensity of the terminal and hydrogen-bonded silanol bands at 3745and around 3500cm -1,respectively.Following the silylation,only a negligible band at 968cm -1was observed for pure silica SBA-15even before evacuation (Figure 7B).Silylated Ti-SBA-15,on the other hand,showed the tetrahedral Ti band at 948cm -1,whose intensity hardly changed with the evacuation temper-ature (Figure 7D).Combining the results of Figures 6and 7,we hypothesize that the presence of the tetra-hedral Ti species can be confirmed by IR spectroscopyonly either after the dehydroxylation at elevated tem-peratures or after the hydrophobic treatment by sily-lation.These new techniques would be effectively ap-plicable to the characterization of Ti-containing meso-porous materials.Figure 8shows the IR spectra of Ti-SBA-15and Ti-MCM-41samples with various Ti contents after elimi-nation of the influence of adsorbed water and silanols by evacuation at 773K.The 948cm -1band gradually increased in intensity with increasing Ti content.The intensity was proportional to the Ti content in the region lower than 0.35mmol g -1corresponding to a Si/Ti ratio of ca.50,and deviated from the linearity in the higher Ti content region (Figure 9).This is consistent with the findings obtained from UV -vis spectra that Ti species are incorporated into the silica framework of SBA-15to occupy initially the tetrahedral sites and then par-tially the octahedral sites with a gradual increase in Ti incorporation.A Comparison of Catalytic Properties and Sta-bility between Ti-SBA-15and Ti-MCM-41.Ti-MCM-41and Ti-MCM-48have been well-known to be prom-ising catalysts for the liquid-phase oxidation of bulky molecules.7,8,38Thus,postsynthesized Ti-SBA-15samples have been tested for the epoxidation of cyclohexene with tert -butyl hydroperoxide (TBHP).The products obtained were cyclohexene oxide,1,2-cyclohexanediols formed by a successive solvolysis of the oxide by water on acid sites such as surface silanol groups,and 2-cyclohexen-1-ol and 2-cyclohexen-1-one both due to allylic oxidation.The efficiency of TBHP calculated on the basis of the amount of tert -butyl alcohol was at least over 90mol %in all cases.As shown in Table 3,the main product was cyclohexene oxide,and its selectivity was comparable(38)Koyano,K.A.;Tatsumi,mun.1996,145.Figure 6.IR spectra for pure silica SBA-15(A,B)and Ti-SBA-15(Si/Ti )36)(C,D)without evacuation (a)and after evacuation at 373K (b),473K (c),573K (d),673K (e),and 773K (f)each for 1h.Figure 7.IR spectra for pure silica SBA-15-sil (A,B)and Ti-SBA-15-sil (Si/Ti )36)(C,D)without evacuation (a)and after evacuation at 373K (b),473K (c),573K (d),673K (e),and 773K (f)each for 1h.Both samples were obtained bytrimethylsilylation.Figure 8.IR spectra for Ti-SBA-15samples (A)with Si/Ti ratios of ∞(a),376(b),116(c),80(d),57(e),36(f),27(g),20(h),and 16(i)together with those of Ti-MCM-41samples (B)with Si/Ti ratios of ∞(a),320(b),76(c),58(d),and 37(e).All the spectra were recorded after evacuation at 773K for 2h.Figure 9.Dependence of the intensity of the 948cm -1band on the Ti content of Ti-SBA-15and Ti-MCM-41.1662Chem.Mater.,Vol.14,No.4,2002Wu et al.。
Materials Characterization
Materials Characterization Materials characterization is a fundamental aspect of materials science and engineering, providing a comprehensive understanding of the structure, properties, and performance of materials. Through a myriad of techniques, scientists can probe the intricate details of materials at various length scales, ranging from the macroscopic to the atomic level. This knowledge is crucial for designing and developing new materials with tailored properties for specific applications, as well as optimizing existing materials for improved performance. One of the primary goals of materials characterization is to determine the composition of a material. Techniques such as X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS) allow researchers to identify the elemental constituents of a sample and their relative concentrations. This information is vital for understanding the material's behavior and predicting its interactions with other materials. For instance, in the development of corrosion-resistant alloys, knowing the precise composition is essential for optimizing the alloy's performance in harsh environments. Another crucial aspect of materials characterization is the analysis of the material's microstructure. Techniques like optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) enable researchers to visualize the arrangement of grains, phases, and defects within a material. This microstructural information is directly related to the material's mechanical, electrical, and optical properties. For example, the size and distribution of grains in a metal alloy can significantly influence its strength and ductility. Furthermore, materials characterization encompasses the measurement of various physical and chemical properties. Techniques like tensile testing, hardness testing, and thermal analysis provide insights into thematerial's mechanical strength, hardness, and thermal stability, respectively. These properties are crucial for determining the suitability of a material for specific applications, such as structural components, electronic devices, or high-temperature applications. In recent years, advanced characterization techniques have emerged, pushing the boundaries of materials analysis. Techniques like atom probe tomography (APT) and synchrotron-based X-ray techniques provide unprecedented insights into the three-dimensional atomic structure and chemicalcomposition of materials. These advanced techniques are instrumental in understanding the fundamental mechanisms governing material behavior and driving innovation in materials design. In conclusion, materials characterization plays a pivotal role in advancing our understanding of materials and their properties. From determining the composition and microstructure to measuring various physical and chemical properties, these techniques provide a comprehensive toolbox for probing the intricate details of materials. As our understanding of materials deepens, so too does our ability to design and develop innovative materials with tailored properties for a wide range of applications, ultimately shaping thefuture of technology and engineering.。
常见材料表征技术
常见材料表征技术Materials characterization refers to the techniques and methods used to study and analyze the structure, properties, and composition of materials. Understanding the characteristics of materials is essential for various fields such as chemistry, physics, engineering, and materials science.材料表征是指用于研究和分析材料结构、性质和成分的技术和方法。
了解材料的特性对于化学、物理、工程和材料科学等各个领域都是至关重要的。
One common technique for materials characterization is microscopy, which allows researchers to visualize materials on a microscopic scale. This includes techniques such as optical microscopy, electron microscopy, and scanning probe microscopy. Microscopy provides valuable insights into the morphology, crystal structure, and defects of materials.一种常见的材料表征技术是显微镜技术，这使得研究人员能够在微观尺度上观察材料。
这包括光学显微镜、电子显微镜和扫描探针显微镜等技术。
显微镜技术为材料的形貌、晶体结构和缺陷提供了宝贵的见解。
Spectroscopy is another important technique for materials characterization. It involves the interaction of materials with different forms of radiation, such as light or X-rays, to study their chemical composition and electronic structure. Spectroscopic techniques, including infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, provide valuable information about the molecular and electronic properties of materials.光谱学是材料表征的另一个重要技术。
Materials Characterization
Materials CharacterizationMaterials characterization is a fundamental aspect of materials science and engineering that involves the study of the properties and behavior of materials. It is a critical step in the development of new materials and the improvement of existing ones. The characterization of materials involves the use of various techniques and methods to determine their physical, chemical, mechanical, and thermal properties. These properties help to understand the behavior of materials under different conditions and their suitability for various applications.One of the most common techniques used in materials characterization is microscopy. Microscopy involves the use of microscopes to study the structure and morphology of materials at different scales. Electron microscopy, for example, is used to study the microstructure of materials at the nanoscale. This technique provides high-resolution images of the materials, allowing researchers to study their morphology, crystal structure, and defects. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are two common types of electron microscopy used in materials characterization.Another technique used in materials characterization is spectroscopy. Spectroscopy involves the use of light to study the properties of materials. Different types of spectroscopy techniques are used to study different properties of materials. For example, infrared spectroscopy is used to study the vibrational modes of molecules in materials, while X-ray photoelectron spectroscopy (XPS) is used to study the chemical composition of materials.Mechanical testing is another important aspect of materials characterization. Mechanical testing involves the measurement of the mechanical properties of materials, such as their strength, elasticity, and toughness. These properties are essential for the design and development of materials for specific applications. Tensile testing, hardness testing, and impact testing are common types of mechanical testing used in materials characterization.Thermal analysis is also an important aspect of materials characterization. Thermal analysis involves the study of the thermal properties of materials, such as their meltingpoint, thermal conductivity, and specific heat capacity. These properties are important for understanding the behavior of materials under different temperature conditions and for the design of materials for high-temperature applications.In addition to these techniques, there are many other methods used in materials characterization, such as surface analysis, chromatography, and rheology. Each of these techniques provides valuable information about the properties and behavior of materials.In conclusion, materials characterization is a critical step in the development and improvement of materials for various applications. It involves the use of various techniques and methods to determine the physical, chemical, mechanical, and thermal properties of materials. These properties are essential for understanding the behavior of materials under different conditions and for the design and development of materials for specific applications. The use of advanced characterization techniques is essential for the development of new materials with unique properties and for the improvement of existing materials.。
materials characterization审稿意见
Materials Characterization审稿意见IntroductionMaterials characterization is an essential aspect of scientific research and industrial applications. In this article, we will discuss the importance of materials characterization and explore various techniques used in the field. Additionally, we will address the key considerations for reviewers when evaluating materials characterization studies.Importance of Materials CharacterizationMaterials characterization plays a crucial role in understanding the properties and behavior of various materials. It involves the analysis and evaluation of the structure, composition, and physical properties of materials. By characterizing materials, scientists and engineers can make informed decisions about their applications and optimize their performance.Techniques used in Materials Characterization1. Scanning Electron Microscopy (SEM)SEM is a widely used technique for characterizing materials at high resolution. It uses a focused beam of electrons to scan the surface of a sample, providing detailed information about its topography, composition, and elemental analysis. SEM is particularly useful for studying microstructures, surface morphology, and particle distribution.2. X-ray Diffraction (XRD)XRD is a technique that analyzes the crystal structure of materials. It works by shining X-rays onto a sample and measuring the diffraction pattern produced. This pattern contains information about the arrangement of atoms in the material, allowing researchers to determineits crystal structure, lattice parameters, and phase composition. XRD is commonly used to identify crystalline phases and study phase transformations in materials.3. Fourier Transform Infrared Spectroscopy (FTIR)FTIR is a spectroscopic technique used to identify functional groups and chemical bonds in organic and inorganic materials. It measures the absorption of infrared radiation by the sample, providing a unique fingerprint that can be used for identification. FTIR is widely used in materials characterization to determine the presence of specificchemical groups, analyze molecular structures, and investigate surface properties.4. Thermal AnalysisThermal analysis techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are used to study thethermal behavior of materials. DSC measures the heat flow in a sample as a function of temperature, providing information about phase transitions, thermal stability, and thermal properties. TGA measures the weight loss of a sample as it is heated, allowing for the analysis of composition, decomposition, and moisture content.Key Considerations for ReviewersWhen evaluating materials characterization studies, reviewers should consider several key aspects to assess the quality and significance of the research. These considerations include:1.Sample Preparation: Reviewers should evaluate the adequacy of thesample preparation techniques used in the study. Proper samplepreparation is vital to obtain accurate and representative results.2.Characterization Techniques: Reviewers should assess thesuitability and reliability of the characterization techniquesemployed. The chosen techniques should be appropriate for theresearch objectives and should provide sufficient evidence tosupport the conclusions.3.Data Analysis: Thorough data analysis is essential for materialscharacterization studies. Reviewers should evaluate thestatistical methods, data interpretation, and conclusions drawnfrom the analysis. It is important to ensure that the conclusions are supported by the data presented.4.Reproducibility: Reviewers should consider the reproducibility ofthe results presented in the study. Materials characterizationstudies should provide sufficient information to allow otherresearchers to reproduce the experiments and obtain similarresults.5.Limitations and Future Directions: It is important for authors toacknowledge the limitations of their study and propose futuredirections for research. Reviewers should assess whether theseaspects are adequately addressed and if the study contributes tothe existing knowledge in the field.ConclusionMaterials characterization is an integral part of scientific research and technological advancements. By employing various characterization techniques, researchers gain insights into the properties and behavior of materials, leading to the development of new materials with enhanced functionalities. Reviewers play a crucial role in ensuring the quality and validity of materials characterization studies by thoroughly evaluating the sample preparation, characterization techniques, data analysis, reproducibility, and future directions of the research.。
Materials Characterization
Materials Characterization Materials characterization is a crucial aspect of scientific research and industrial development. It involves the analysis and understanding of the physical, chemical, mechanical, and microstructural properties of materials. Bycharacterizing materials, scientists and engineers can gain valuable insights into their behavior, performance, and potential applications. This process plays a pivotal role in various fields, including metallurgy, nanotechnology, biomaterials, and semiconductor manufacturing. In this discussion, we will explore the significance of materials characterization from different perspectives,highlighting its impact on research, innovation, and technological advancements. From a scientific standpoint, materials characterization serves as a fundamental tool for investigating the structure-property relationships of different substances. By employing advanced techniques such as electron microscopy, X-ray diffraction, and spectroscopy, researchers can elucidate the atomic and molecular composition of materials, as well as their crystalline structure and surface morphology. This in-depth understanding enables scientists to tailor materialswith specific properties, leading to the development of innovative technologiesand novel materials with enhanced performance and functionality. Moreover, materials characterization plays a vital role in advancing our knowledge of fundamental scientific principles, contributing to the broader scientific community's understanding of material behavior and properties. In the realm of industrial applications, materials characterization is indispensable for quality control, process optimization, and product development. By accurately assessingthe mechanical, thermal, and electrical properties of materials, manufacturers can ensure the reliability and performance of their products. For instance, in the automotive industry, materials characterization is used to evaluate the strength and durability of components, leading to the production of safer and moreefficient vehicles. Similarly, in the electronics industry, the characterizationof semiconductors and electronic materials is critical for enhancing device performance and reliability. Furthermore, in the field of nanotechnology, the precise characterization of nanomaterials is essential for enabling their integration into various commercial products, ranging from consumer electronics tomedical devices. Beyond its scientific and industrial implications, materials characterization also holds significant importance in the context of environmental sustainability and resource conservation. By understanding the environmental impact of different materials and manufacturing processes, researchers andindustry professionals can work towards developing eco-friendly materials and sustainable production methods. For example, the characterization of recyclable and biodegradable materials is essential for promoting a circular economy and reducing the environmental footprint of various industries. Additionally, the analysis of materials for energy storage and conversion technologies, such as batteries and solar cells, is crucial for advancing renewable energy solutions and mitigating the impact of climate change. From a broader societal perspective, the advancements in materials characterization have the potential to drive economic growth, innovation, and job creation. By fostering collaboration between academia, industry, and government agencies, the development of new materials and technologies can lead to the emergence of high-tech industries and the generation of skilled employment opportunities. Furthermore, the commercialization of novel materials and products resulting from materials characterization research can have far-reaching implications for various sectors, including healthcare, transportation, and telecommunications. Ultimately, the societal benefits of materials characterization extend beyond technical advancements, influencing the overall well-being and prosperity of communities and economies. In conclusion, materials characterization is a multifaceted discipline with far-reaching implications for scientific research, industrial development, environmental sustainability, and societal progress. Its significance lies in its ability to unravel the intrinsic properties of materials, driving innovation and technological advancements across diverse fields. By leveraging advanced characterization techniques, researchers and industry professionals can unlock new opportunities for material design, performance optimization, and sustainable development. As we continue to push the boundaries of materials science, the impact of materials characterization will undoubtedly shape the future of technology, industry, and society as a whole.。
(NEW)胡壮麟《语言学教程》(第5版)配套题库【考研真题精选+章节题库】
7. One of the important distinctions in linguistics is _____ and performance. （人大2006研） 【答案】competence 【解析】语言能力指理想的语言使用者关于语言规则的语言知识，语言 应用指语言交际中关于语言规则知识的实际使用。
因为大多数动物的“语言”需要“即时刺激控制”。
18. The most serious defect concerns the use of semantic markers like (Human) and (Male), which, more usually called semantic components are elements of an artificial _____.（北京邮电大学2014研） 【答案】metalanguage 【解析】本题考查成分分析的弊端。通过语义特征来进行成分分析的一 大弊端是这些意义特征使用的是人工化的元语言，元语言本身的含义也 需进一步解释。
20.Chinese Characters
01
Chapter 1: The History of Chinese Characters
Chapter 1: The History of Chinese Characters
• Chinese characters, also known as Hanzi, are logograms developed for the writing of the Chinese language. The history of Chinese characters can be traced back over 3,000 years to the Shang dynasty. The development of Chinese characters has been a reflection of the cultural and technological advancements of ancient China.
• Origin and Evolution • Cultural Significance • Influence Beyond Language
Origin and Evolution
• The origins of Chinese characters can be found in ancient inscriptions on oracle bones and bronze ware. These early forms of writing consisted of simple pictograms and ideograms representing objects and ideas. Over time, the characters evolved into more intricate forms, incorporating phonetic elements and semantic radicals.
formal
FormalismFormalism is primarily a view about what it takes to determine the aesthetic characteristics or features or properties of things. Which characteristics are aesthetic? ‘Aesthetic’ is an elastic term. One approach to giving it a sense is simply to give a list of examples of the kind of features that are aesthetic: beauty, ugliness, daintiness, dumpiness, elegance, and so on. A more ambitious approach is to say that the list of aesthetic characteristics is non-arbitrary in virtue of a crucial role that beauty and ugliness play: other characteristics, such as, elegance, are ways of being beautiful or ugly. Either way, it is clear that works of art have many non-aesthetic characteristics, and nature has many aesthetic characteristics. (Formalism is sometimes thought of as a view of the nature of art, but that is probably because a view about aesthetic characteristics is conjoined with an aesthetic view of the nature of art.)Formal and Non-formal PropertiesNow, what of formal aesthetic characteristics? These are sub-class of the aesthetic ones. Rather than offering a definition, we can gain an indication of which aesthetic properties they are by considering debates over various artforms.Clive Bell (1914) and Roger Fry (1920) thought that formal aesthetic features of paintings are those that are determined by the lines, shapes and colours that are within the frame. By contrast, the meaning and representational characteristics of paintings are not entirely determined by what is in the frame but also by the work’s history of production. What a painting means or represents is determined in part by the intentions of the person who made it (Wollheim 1980, 1987). Such intentions are not sufficient, but they are necessary for the meanings or representational properties of paintings. Thus meaning and representation are not formally relevant. The aesthetic formalist about paintings believes that all their aesthetic properties are formal; they are all determined solely by what is in the frame and not at all by their history of production. By contrast, the anti-formalist about paintings believes that all their aesthetic properties are determined in part by their history of production. Sometimes anti-formalists appeal to the context of interpretive practices in which works are embedded, instead of their history of production, or they invoke some combination of interpretive practices and history of production, or some other extrinsic factor. I shall assume, however, that anti-formalists insist on the aesthetic importance of the history of production of works.Eduard Hanslick claimed that musical beauty was determined by structures of sound (1986, chapter 3). On this view, even if music sometimes has meanings, they are of no relevance to its formal aesthetic properties. The emotions leading a musician or composer to make music, and the emotions generated in listeners are formally irrelevant. In a performance of a piece of classical music, for example, the ‘frame’around the sounds that determines formal aesthetic properties is the tapping of the conductor’s baton and the applause (see Cone 1968). That structure of sounds determines the formal properties of the music. Anything outside that, such as the history of production of the sounds or their emotional causes or effects, is aesthetically irrelevant.Form as StructureThere is another sense of form and formal properties that has currency especially in reflections on literature, but also in music, architecture and painting and that is of form as structure. This is a matter of the arrangement of the elements of a work with respect to each other. Consider three cards arranged in a line: the 6 of hearts, the 6 of spades and the 7 of hearts. There is a sense in which they have an ABA structure, and another in which they have and AAB structure. Perhaps they have both. Now consider a painting with three human figures in a line: king in a red cloak, a bishop in a red cloak, and a king in a blue cloak. There is a sense in which it has an ABA structure and a sense in which it has an ABA structure. But note that the AAB structure is formal in the previous sense that it is determined by what is in the frame by the lines, shapes and colours on the surface while the ABA ‘structural form’ is determined by what they represent (king or bishop), and on most plausible views that structure is not determined just by the lines, shapes and colours that are in the frame, but is determined in part by the artist’s intention. So the sense of form as structure does not overlap with the sense of form as the determination of aesthetic features by what is in the frame. Let us put structural form to one side here, interesting though it is.Formalism vs anti-formalismAnti-formalists say that in order to appreciate a work of art aesthetically we must always see that work as historically situated. Aesthetic anti-formalism, with its emphasis on historical determination, has its roots in Hegelian history and philosophy of culture (Kulturgeschichte) that was popular in prewar Germany and Austria. This was imported to English-speaking countries by refugees from Naziism, becoming very influential in English-speaking art-history, and beyond. Consider Earnst Gombrich’s multi-million selling The Story of Art (Gombrich 1950). The anti-formalism is right there in the title! The idea became commonplace that the aesthetic value and even the identity of a work of art depend on its place in the story of art. Contrast Bell, the formalist, who writes ‘…what does it matter whether the forms that move [us] were created in Paris the day before yesterday or in Babylon fifty centuries ago?’ (1914: 45-6).Gotlob Frege famously said that a word only has meaning in the context of a sentence (1967), and similarly most aestheticians would assert that the elements of a work only have significance in the context of the whole work. W. V. O. Quine equally famously said that a sentence only has meaning in the context ofother sentences of the language (1951), and similarly aesthetic anti-formalists assert that a work only has aesthetic significance in the context of other works in the tradition in which the work is located. Aesthetic formalists deny this and insist that works sustain their aesthetic properties by themselves. (There was a similar debate, conducted in different terms, in the Renaissance; see Mitrovic 2004.)Anti-formalists believe that all aesthetic properties are historically determined and that aesthetic judgements should always be made, and experiences always had, in the light of appropriate historical categories (Walton 1970). Formalists deny this. Anti-formalists charge formalists with a naïve belief in the ‘innocent eye’ according to which knowledge of history is irrelevant to the aesthetic appreciation. Formalists celebrate the innocent eye, preferring it to one cluttered with irrelevances. Innocence is sometimes a good thing, they say.Arguments?What can be said in favour of either view? In favour of anti-formalism, Gombrich put forward an imaginary example of physically identical works by different artists and invited us to judge that they are aesthetically different (Gombrich 1959: 313). Philosophers like Danto (1964) and Walton (1970) followed suit. Such arguments are supposed to show that a work’s physical nature does not suffice for its aesthetic properties and that history also plays a role. But the appeal to imaginary examples has limited dialectical efficacy. Fanciful thought experiments sometimes involving Martians are supposed to generate possible examples of physically identical artworks with different aesthetic properties; but whether such cases are really possible is far from uncontroversial. The dialectical pressure exerted by such examples is minimal since formalists and anti-formalists will simply interpret the examples differently. Physically identical cases with different histories may have other interesting differences. For example, they might differ in originality; but that difference may not contribute to a difference in their beauty, elegance or delicacy that is, it may make no aesthetic difference. Or so the formalist will say, and merely imaginary examples will not sway them. Similarly, it is controversial whether being a fake makes an aesthetic difference.Arguments for or against formalism should probably be less purely philosophical and involve more attention to actual cases. The apparently abstract metaphysical issue about what it takes to determine aesthetic properties is probably not answerable without practical critical engagement with works of art in various art forms. Here it is worth transgressing disciplinary boundaries. This need not mean the vacuous kind of ‘inter-disciplinarity’ that is mere deference to the apparent authority of another discipline (so as to avoid the authority of ones own!). It can be an active engagement with the subject matter of both disciplines with whatever genres of intellectual thought are available (so long as the disciplines really do engage with the subject-matter, rather than being an excuse for undisciplined philosophy).It is likely that the issue or issues over formalism needs to be discussed artform by artform; there may be no one correct view that applies universally. And even within artforms, it may be that no general theory is right.Moderate FormalismBoth formalism and anti-formalism have something to be said for them, and yet both also seem too extreme.A possible middle course is what we might call ‘moderate formalism’ (Zangwill 2001). On this view, many aesthetic properties are formal and many are not; and many works have only formal properties and many do not have only formal properties. Moderate formalism admits some, and indeed many non-formal properties of works. For example, marching music or religious music is music with a non-musical function; it is music for marching or praying; but the way it realizes that extra-musical function may be part of its aesthetic excellence. This is unlike music that is for shopping: there the question is simply: ‘Does it make people buy more?’, or perhaps: ‘Does it make shopping more pleasant?’ Shopping music is not the aesthetically appropriate expression of the activity of shopping in the way that music may be the appropriate aesthetic expression of marching or praying. Sometimes musical beauty arises when music serves some non-musical function or purpose in a musically appropriate way. The music has a certain non-musical function and the aesthetic qualities of the music are not separate from that function but are an expression, articulation or realization of it. This is what Kant calls ‘dependent’ beauty (1928, section 16). Similarly, there can be a representation which is beautiful, elegant or delicate as a representation, and a building may be beautiful as a mosque, station or library.So non-formal aesthetic properties are important. Bell, Fry and Hanslick overshot in denying that. However, there are many aesthetic properties that are purely formal, and there are many purely formal works. Some paintings are entirely abstract and quite a lot of music is ‘absolute’. Moreover, most representational paintings have formal aesthetic features among their other aesthetic features. Extreme anti-formalism, which denies the existence of formal aesthetic properties and purely formal works, goes too far. Moderate formalism insists on the importance of both formal and non-formal properties.See also AESTHETICISM, ART AND THE SENSES, BELL, DANTO, FORGERY, GOMBRICH, HANSLICK, REPRESENTATION, WALTONBIBLIOGRAPHYClive Bell 1914. Art. London: Chatto and Windus.Edward Cone 1968. Musical Form and Musical Performance. New York: Norton.Arthur Danto 1964. ‘The Artword’. Journal of Philosophy 61: 571-584.Gotlob Frege 1967. ‘The Thought: a Logical Inquiry.’ In Philosophical Logic (ed.) P. F. Strawson.Oxford: Oxford University Press: 17–38.Roger Fry 1920. Vision and Design. London: Chatto and Windus.Ernst Gombrich 1950. The Story of Art. London: Phaidon.Ernst Gombrich 1959. Art and Illusion. London: Phaidon.Eduard Handslick 1986. On the Musically Beautiful. Indianapolis: Hackett.Immanuel Kant 1928. Critique of Judgment, transl. Meredith. Oxford: Oxford University Press. Branko Mitrovic 2004. Learnng From Palladio. New York: Norton.W.V.O. Quine 1951. ‘Two Dogmas of Empiricism’. In From and Logical Point of View. Cambridge Mass.: Harvard University Press: 20-46.Frank Sibley 1959. ‘Aesthetic Concepts’. Philosophical Review LXVII: 421-450Kendall Walton 1970. ‘Categories of Art’. Philosophical Review LXXIX: 334-367.Richard Wollheim 1980. ‘Seeing-In, Seeing-As and Pictorial Representation’. In Art and Its Objects.Cambridge: Cambridge University Press, second edition: 205-226.Richard Wollheim 1987. Painting as an Art. London: Thames and Hudson.Nick Zangwill 2001. The Metaphysics of Beauty. Ithaca: Cornell University Press.。
专八英语阅读
英语专业八级考试TEM-8阅读理解练习册（1）(英语专业2012级)UNIT 1Text AEvery minute of every day, what ecologist生态学家James Carlton calls a global ―conveyor belt‖, redistributes ocean organisms生物.It’s planetwide biological disruption生物的破坏that scientists have barely begun to understand.Dr. Carlton —an oceanographer at Williams College in Williamstown,Mass.—explains that, at any given moment, ―There are several thousand marine species traveling… in the ballast water of ships.‖ These creatures move from coastal waters where they fit into the local web of life to places where some of them could tear that web apart. This is the larger dimension of the infamous无耻的，邪恶的invasion of fish-destroying, pipe-clogging zebra mussels有斑马纹的贻贝.Such voracious贪婪的invaders at least make their presence known. What concerns Carlton and his fellow marine ecologists is the lack of knowledge about the hundreds of alien invaders that quietly enter coastal waters around the world every day. Many of them probably just die out. Some benignly亲切地，仁慈地—or even beneficially — join the local scene. But some will make trouble.In one sense, this is an old story. Organisms have ridden ships for centuries. They have clung to hulls and come along with cargo. What’s new is the scale and speed of the migrations made possible by the massive volume of ship-ballast water压载水— taken in to provide ship stability—continuously moving around the world…Ships load up with ballast water and its inhabitants in coastal waters of one port and dump the ballast in another port that may be thousands of kilometers away. A single load can run to hundreds of gallons. Some larger ships take on as much as 40 million gallons. The creatures that come along tend to be in their larva free-floating stage. When discharged排出in alien waters they can mature into crabs, jellyfish水母, slugs鼻涕虫，蛞蝓, and many other forms.Since the problem involves coastal species, simply banning ballast dumps in coastal waters would, in theory, solve it. Coastal organisms in ballast water that is flushed into midocean would not survive. Such a ban has worked for North American Inland Waterway. But it would be hard to enforce it worldwide. Heating ballast water or straining it should also halt the species spread. But before any such worldwide regulations were imposed, scientists would need a clearer view of what is going on.The continuous shuffling洗牌of marine organisms has changed the biology of the sea on a global scale. It can have devastating effects as in the case of the American comb jellyfish that recently invaded the Black Sea. It has destroyed that sea’s anchovy鳀鱼fishery by eating anchovy eggs. It may soon spread to western and northern European waters.The maritime nations that created the biological ―conveyor belt‖ should support a coordinated international effort to find out what is going on and what should be done about it. (456 words)1.According to Dr. Carlton, ocean organism‟s are_______.A.being moved to new environmentsB.destroying the planetC.succumbing to the zebra musselD.developing alien characteristics2.Oceanographers海洋学家are concerned because_________.A.their knowledge of this phenomenon is limitedB.they believe the oceans are dyingC.they fear an invasion from outer-spaceD.they have identified thousands of alien webs3.According to marine ecologists, transplanted marinespecies____________.A.may upset the ecosystems of coastal watersB.are all compatible with one anotherC.can only survive in their home watersD.sometimes disrupt shipping lanes4.The identified cause of the problem is_______.A.the rapidity with which larvae matureB. a common practice of the shipping industryC. a centuries old speciesD.the world wide movement of ocean currents5.The article suggests that a solution to the problem__________.A.is unlikely to be identifiedB.must precede further researchC.is hypothetically假设地，假想地easyD.will limit global shippingText BNew …Endangered‟ List Targets Many US RiversIt is hard to think of a major natural resource or pollution issue in North America today that does not affect rivers.Farm chemical runoff残渣, industrial waste, urban storm sewers, sewage treatment, mining, logging, grazing放牧,military bases, residential and business development, hydropower水力发电,loss of wetlands. The list goes on.Legislation like the Clean Water Act and Wild and Scenic Rivers Act have provided some protection, but threats continue.The Environmental Protection Agency (EPA) reported yesterday that an assessment of 642,000 miles of rivers and streams showed 34 percent in less than good condition. In a major study of the Clean Water Act, the Natural Resources Defense Council last fall reported that poison runoff impairs损害more than 125,000 miles of rivers.More recently, the NRDC and Izaak Walton League warned that pollution and loss of wetlands—made worse by last year’s flooding—is degrading恶化the Mississippi River ecosystem.On Tuesday, the conservation group保护组织American Rivers issued its annual list of 10 ―endangered‖ and 20 ―threatened‖ rivers in 32 states, the District of Colombia, and Canada.At the top of the list is the Clarks Fork of the Yellowstone River, whereCanadian mining firms plan to build a 74-acre英亩reservoir水库，蓄水池as part of a gold mine less than three miles from Yellowstone National Park. The reservoir would hold the runoff from the sulfuric acid 硫酸used to extract gold from crushed rock.―In the event this tailings pond failed, the impact to th e greater Yellowstone ecosystem would be cataclysmic大变动的，灾难性的and the damage irreversible不可逆转的.‖ Sen. Max Baucus of Montana, chairman of the Environment and Public Works Committee, wrote to Noranda Minerals Inc., an owner of the ― New World Mine‖.Last fall, an EPA official expressed concern about the mine and its potential impact, especially the plastic-lined storage reservoir. ― I am unaware of any studies evaluating how a tailings pond尾矿池，残渣池could be maintained to ensure its structural integrity forev er,‖ said Stephen Hoffman, chief of the EPA’s Mining Waste Section. ―It is my opinion that underwater disposal of tailings at New World may present a potentially significant threat to human health and the environment.‖The results of an environmental-impact statement, now being drafted by the Forest Service and Montana Department of State Lands, could determine the mine’s future…In its recent proposal to reauthorize the Clean Water Act, the Clinton administration noted ―dramatically improved water quality since 1972,‖ when the act was passed. But it also reported that 30 percent of riverscontinue to be degraded, mainly by silt泥沙and nutrients from farm and urban runoff, combined sewer overflows, and municipal sewage城市污水. Bottom sediments沉积物are contaminated污染in more than 1,000 waterways, the administration reported in releasing its proposal in January. Between 60 and 80 percent of riparian corridors (riverbank lands) have been degraded.As with endangered species and their habitats in forests and deserts, the complexity of ecosystems is seen in rivers and the effects of development----beyond the obvious threats of industrial pollution, municipal waste, and in-stream diversions改道to slake消除the thirst of new communities in dry regions like the Southwes t…While there are many political hurdles障碍ahead, reauthorization of the Clean Water Act this year holds promise for US rivers. Rep. Norm Mineta of California, who chairs the House Committee overseeing the bill, calls it ―probably the most important env ironmental legislation this Congress will enact.‖ (553 words)6.According to the passage, the Clean Water Act______.A.has been ineffectiveB.will definitely be renewedC.has never been evaluatedD.was enacted some 30 years ago7.“Endangered” rivers are _________.A.catalogued annuallyB.less polluted than ―threatened rivers‖C.caused by floodingD.adjacent to large cities8.The “cataclysmic” event referred to in paragraph eight would be__________.A. fortuitous偶然的，意外的B. adventitious外加的，偶然的C. catastrophicD. precarious不稳定的，危险的9. The owners of the New World Mine appear to be______.A. ecologically aware of the impact of miningB. determined to construct a safe tailings pondC. indifferent to the concerns voiced by the EPAD. willing to relocate operations10. The passage conveys the impression that_______.A. Canadians are disinterested in natural resourcesB. private and public environmental groups aboundC. river banks are erodingD. the majority of US rivers are in poor conditionText CA classic series of experiments to determine the effects ofoverpopulation on communities of rats was reported in February of 1962 in an article in Scientific American. The experiments were conducted by a psychologist, John B. Calhoun and his associates. In each of these experiments, an equal number of male and female adult rats were placed in an enclosure and given an adequate supply of food, water, and other necessities. The rat populations were allowed to increase. Calhoun knew from experience approximately how many rats could live in the enclosures without experiencing stress due to overcrowding. He allowed the population to increase to approximately twice this number. Then he stabilized the population by removing offspring that were not dependent on their mothers. He and his associates then carefully observed and recorded behavior in these overpopulated communities. At the end of their experiments, Calhoun and his associates were able to conclude that overcrowding causes a breakdown in the normal social relationships among rats, a kind of social disease. The rats in the experiments did not follow the same patterns of behavior as rats would in a community without overcrowding.The females in the rat population were the most seriously affected by the high population density: They showed deviant异常的maternal behavior; they did not behave as mother rats normally do. In fact, many of the pups幼兽，幼崽, as rat babies are called, died as a result of poor maternal care. For example, mothers sometimes abandoned their pups,and, without their mothers' care, the pups died. Under normal conditions, a mother rat would not leave her pups alone to die. However, the experiments verified that in overpopulated communities, mother rats do not behave normally. Their behavior may be considered pathologically 病理上，病理学地diseased.The dominant males in the rat population were the least affected by overpopulation. Each of these strong males claimed an area of the enclosure as his own. Therefore, these individuals did not experience the overcrowding in the same way as the other rats did. The fact that the dominant males had adequate space in which to live may explain why they were not as seriously affected by overpopulation as the other rats. However, dominant males did behave pathologically at times. Their antisocial behavior consisted of attacks on weaker male,female, and immature rats. This deviant behavior showed that even though the dominant males had enough living space, they too were affected by the general overcrowding in the enclosure.Non-dominant males in the experimental rat communities also exhibited deviant social behavior. Some withdrew completely; they moved very little and ate and drank at times when the other rats were sleeping in order to avoid contact with them. Other non-dominant males were hyperactive; they were much more active than is normal, chasing other rats and fighting each other. This segment of the rat population, likeall the other parts, was affected by the overpopulation.The behavior of the non-dominant males and of the other components of the rat population has parallels in human behavior. People in densely populated areas exhibit deviant behavior similar to that of the rats in Calhoun's experiments. In large urban areas such as New York City, London, Mexican City, and Cairo, there are abandoned children. There are cruel, powerful individuals, both men and women. There are also people who withdraw and people who become hyperactive. The quantity of other forms of social pathology such as murder, rape, and robbery also frequently occur in densely populated human communities. Is the principal cause of these disorders overpopulation? Calhoun’s experiments suggest that it might be. In any case, social scientists and city planners have been influenced by the results of this series of experiments.11. Paragraph l is organized according to__________.A. reasonsB. descriptionC. examplesD. definition12．Calhoun stabilized the rat population_________.A. when it was double the number that could live in the enclosure without stressB. by removing young ratsC. at a constant number of adult rats in the enclosureD. all of the above are correct13.W hich of the following inferences CANNOT be made from theinformation inPara. 1?A. Calhoun's experiment is still considered important today.B. Overpopulation causes pathological behavior in rat populations.C. Stress does not occur in rat communities unless there is overcrowding.D. Calhoun had experimented with rats before.14. Which of the following behavior didn‟t happen in this experiment?A. All the male rats exhibited pathological behavior.B. Mother rats abandoned their pups.C. Female rats showed deviant maternal behavior.D. Mother rats left their rat babies alone.15. The main idea of the paragraph three is that __________.A. dominant males had adequate living spaceB. dominant males were not as seriously affected by overcrowding as the otherratsC. dominant males attacked weaker ratsD. the strongest males are always able to adapt to bad conditionsText DThe first mention of slavery in the statutes法令，法规of the English colonies of North America does not occur until after 1660—some forty years after the importation of the first Black people. Lest we think that existed in fact before it did in law, Oscar and Mary Handlin assure us, that the status of B lack people down to the 1660’s was that of servants. A critique批判of the Handlins’ interpretation of why legal slavery did not appear until the 1660’s suggests that assumptions about the relation between slavery and racial prejudice should be reexamined, and that explanation for the different treatment of Black slaves in North and South America should be expanded.The Handlins explain the appearance of legal slavery by arguing that, during the 1660’s, the position of white servants was improving relative to that of black servants. Thus, the Handlins contend, Black and White servants, heretofore treated alike, each attained a different status. There are, however, important objections to this argument. First, the Handlins cannot adequately demonstrate that t he White servant’s position was improving, during and after the 1660’s; several acts of the Maryland and Virginia legislatures indicate otherwise. Another flaw in the Handlins’ interpretation is their assumption that prior to the establishment of legal slavery there was no discrimination against Black people. It is true that before the 1660’s Black people were rarely called slaves. But this shouldnot overshadow evidence from the 1630’s on that points to racial discrimination without using the term slavery. Such discrimination sometimes stopped short of lifetime servitude or inherited status—the two attributes of true slavery—yet in other cases it included both. The Handlins’ argument excludes the real possibility that Black people in the English colonies were never treated as the equals of White people.The possibility has important ramifications后果，影响.If from the outset Black people were discriminated against, then legal slavery should be viewed as a reflection and an extension of racial prejudice rather than, as many historians including the Handlins have argued, the cause of prejudice. In addition, the existence of discrimination before the advent of legal slavery offers a further explanation for the harsher treatment of Black slaves in North than in South America. Freyre and Tannenbaum have rightly argued that the lack of certain traditions in North America—such as a Roman conception of slavery and a Roman Catholic emphasis on equality— explains why the treatment of Black slaves was more severe there than in the Spanish and Portuguese colonies of South America. But this cannot be the whole explanation since it is merely negative, based only on a lack of something. A more compelling令人信服的explanation is that the early and sometimes extreme racial discrimination in the English colonies helped determine the particular nature of the slavery that followed. (462 words)16. Which of the following is the most logical inference to be drawn from the passage about the effects of “several acts of the Maryland and Virginia legislatures” (Para.2) passed during and after the 1660‟s?A. The acts negatively affected the pre-1660’s position of Black as wellas of White servants.B. The acts had the effect of impairing rather than improving theposition of White servants relative to what it had been before the 1660’s.C. The acts had a different effect on the position of white servants thandid many of the acts passed during this time by the legislatures of other colonies.D. The acts, at the very least, caused the position of White servants toremain no better than it had been before the 1660’s.17. With which of the following statements regarding the status ofBlack people in the English colonies of North America before the 1660‟s would the author be LEAST likely to agree?A. Although black people were not legally considered to be slaves,they were often called slaves.B. Although subject to some discrimination, black people had a higherlegal status than they did after the 1660’s.C. Although sometimes subject to lifetime servitude, black peoplewere not legally considered to be slaves.D. Although often not treated the same as White people, black people,like many white people, possessed the legal status of servants.18. According to the passage, the Handlins have argued which of thefollowing about the relationship between racial prejudice and the institution of legal slavery in the English colonies of North America?A. Racial prejudice and the institution of slavery arose simultaneously.B. Racial prejudice most often the form of the imposition of inheritedstatus, one of the attributes of slavery.C. The source of racial prejudice was the institution of slavery.D. Because of the influence of the Roman Catholic Church, racialprejudice sometimes did not result in slavery.19. The passage suggests that the existence of a Roman conception ofslavery in Spanish and Portuguese colonies had the effect of _________.A. extending rather than causing racial prejudice in these coloniesB. hastening the legalization of slavery in these colonies.C. mitigating some of the conditions of slavery for black people in these coloniesD. delaying the introduction of slavery into the English colonies20. The author considers the explanation put forward by Freyre andTannenbaum for the treatment accorded B lack slaves in the English colonies of North America to be _____________.A. ambitious but misguidedB. valid有根据的but limitedC. popular but suspectD. anachronistic过时的，时代错误的and controversialUNIT 2Text AThe sea lay like an unbroken mirror all around the pine-girt, lonely shores of Orr’s Island. Tall, kingly spruce s wore their regal王室的crowns of cones high in air, sparkling with diamonds of clear exuded gum流出的树胶; vast old hemlocks铁杉of primeval原始的growth stood darkling in their forest shadows, their branches hung with long hoary moss久远的青苔;while feathery larches羽毛般的落叶松,turned to brilliant gold by autumn frosts, lighted up the darker shadows of the evergreens. It was one of those hazy朦胧的, calm, dissolving days of Indian summer, when everything is so quiet that the fainest kiss of the wave on the beach can be heard, and white clouds seem to faint into the blue of the sky, and soft swathing一长条bands of violet vapor make all earth look dreamy, and give to the sharp, clear-cut outlines of the northern landscape all those mysteries of light and shade which impart such tenderness to Italian scenery.The funeral was over,--- the tread鞋底的花纹/ 踏of many feet, bearing the heavy burden of two broken lives, had been to the lonely graveyard, and had come back again,--- each footstep lighter and more unconstrained不受拘束的as each one went his way from the great old tragedy of Death to the common cheerful of Life.The solemn black clock stood swaying with its eternal ―tick-tock, tick-tock,‖ in the kitchen of the brown house on Orr’s Island. There was there that sense of a stillness that can be felt,---such as settles down on a dwelling住处when any of its inmates have passed through its doors for the last time, to go whence they shall not return. The best room was shut up and darkened, with only so much light as could fall through a little heart-shaped hole in the window-shutter,---for except on solemn visits, or prayer-meetings or weddings, or funerals, that room formed no part of the daily family scenery.The kitchen was clean and ample, hearth灶台, and oven on one side, and rows of old-fashioned splint-bottomed chairs against the wall. A table scoured to snowy whiteness, and a little work-stand whereon lay the Bible, the Missionary Herald, and the Weekly Christian Mirror, before named, formed the principal furniture. One feature, however, must not be forgotten, ---a great sea-chest水手用的储物箱,which had been the companion of Zephaniah through all the countries of the earth. Old, and battered破旧的，磨损的, and unsightly难看的it looked, yet report said that there was good store within which men for the most part respect more than anything else; and, indeed it proved often when a deed of grace was to be done--- when a woman was suddenly made a widow in a coast gale大风，狂风, or a fishing-smack小渔船was run down in the fogs off the banks, leaving in some neighboring cottage a family of orphans,---in all such cases, the opening of this sea-chest was an event of good omen 预兆to the bereaved丧亲者;for Zephaniah had a large heart and a large hand, and was apt有…的倾向to take it out full of silver dollars when once it went in. So the ark of the covenant约柜could not have been looked on with more reverence崇敬than the neighbours usually showed to Captain Pennel’s sea-chest.1. The author describes Orr‟s Island in a(n)______way.A.emotionally appealing, imaginativeB.rational, logically preciseC.factually detailed, objectiveD.vague, uncertain2.According to the passage, the “best room”_____.A.has its many windows boarded upB.has had the furniture removedC.is used only on formal and ceremonious occasionsD.is the busiest room in the house3.From the description of the kitchen we can infer that thehouse belongs to people who_____.A.never have guestsB.like modern appliancesC.are probably religiousD.dislike housework4.The passage implies that_______.A.few people attended the funeralB.fishing is a secure vocationC.the island is densely populatedD.the house belonged to the deceased5.From the description of Zephaniah we can see thathe_________.A.was physically a very big manB.preferred the lonely life of a sailorC.always stayed at homeD.was frugal and saved a lotText BBasic to any understanding of Canada in the 20 years after the Second World War is the country' s impressive population growth. For every three Canadians in 1945, there were over five in 1966. In September 1966 Canada's population passed the 20 million mark. Most of this surging growth came from natural increase. The depression of the 1930s and the war had held back marriages, and the catching-up process began after 1945. The baby boom continued through the decade of the 1950s, producing a population increase of nearly fifteen percent in the five years from 1951 to 1956. This rate of increase had been exceeded only once before in Canada's history, in the decade before 1911 when the prairies were being settled. Undoubtedly, the good economic conditions of the 1950s supported a growth in the population, but the expansion also derived from a trend toward earlier marriages and an increase in the average size of families; In 1957 the Canadian birth rate stood at 28 per thousand, one of the highest in the world. After the peak year of 1957, thebirth rate in Canada began to decline. It continued falling until in 1966 it stood at the lowest level in 25 years. Partly this decline reflected the low level of births during the depression and the war, but it was also caused by changes in Canadian society. Young people were staying at school longer, more women were working; young married couples were buying automobiles or houses before starting families; rising living standards were cutting down the size of families. It appeared that Canada was once more falling in step with the trend toward smaller families that had occurred all through theWestern world since the time of the Industrial Revolution. Although the growth in Canada’s population had slowed down by 1966 (the cent), another increase in the first half of the 1960s was only nine percent), another large population wave was coming over the horizon. It would be composed of the children of the children who were born during the period of the high birth rate prior to 1957.6. What does the passage mainly discuss?A. Educational changes in Canadian society.B. Canada during the Second World War.C. Population trends in postwar Canada.D. Standards of living in Canada.7. According to the passage, when did Canada's baby boom begin?A. In the decade after 1911.B. After 1945.C. During the depression of the 1930s.D. In 1966.8. The author suggests that in Canada during the 1950s____________.A. the urban population decreased rapidlyB. fewer people marriedC. economic conditions were poorD. the birth rate was very high9. When was the birth rate in Canada at its lowest postwar level?A. 1966.B. 1957.C. 1956.D. 1951.10. The author mentions all of the following as causes of declines inpopulation growth after 1957 EXCEPT_________________.A. people being better educatedB. people getting married earlierC. better standards of livingD. couples buying houses11.I t can be inferred from the passage that before the IndustrialRevolution_______________.A. families were largerB. population statistics were unreliableC. the population grew steadilyD. economic conditions were badText CI was just a boy when my father brought me to Harlem for the first time, almost 50 years ago. We stayed at the hotel Theresa, a grand brick structure at 125th Street and Seventh avenue. Once, in the hotel restaurant, my father pointed out Joe Louis. He even got Mr. Brown, the hotel manager, to introduce me to him, a bit punchy强力的but still champ焦急as fast as I was concerned.Much has changed since then. Business and real estate are booming. Some say a new renaissance is under way. Others decry责难what they see as outside forces running roughshod肆意践踏over the old Harlem. New York meant Harlem to me, and as a young man I visited it whenever I could. But many of my old haunts are gone. The Theresa shut down in 1966. National chains that once ignored Harlem now anticipate yuppie money and want pieces of this prime Manhattan real estate. So here I am on a hot August afternoon, sitting in a Starbucks that two years ago opened a block away from the Theresa, snatching抓取，攫取at memories between sips of high-priced coffee. I am about to open up a piece of the old Harlem---the New York Amsterdam News---when a tourist。
Materials Characterization
Materials Characterization Materials characterization is a crucial aspect of scientific research and industrial development. It involves the study and analysis of the properties and structure of materials at a microscopic and macroscopic level. This process helpsin understanding the behavior and performance of materials in various applications, such as in the development of new products, improvement of existing materials, and quality control in manufacturing processes. One of the key techniques used in materials characterization is microscopy, which allows researchers to examine the microstructure of materials and observe features such as grain boundaries, defects, and phase composition. Scanning electron microscopy (SEM) and transmissionelectron microscopy (TEM) are commonly used to obtain high-resolution images of materials, providing valuable information about their morphology and crystal structure. Another important aspect of materials characterization is the analysis of chemical composition. Techniques such as X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) are used to determine the elementalcomposition of materials and identify the presence of impurities or phases. This information is crucial for understanding the chemical properties of materials and their suitability for specific applications. In addition to microscopy and chemical analysis, mechanical testing is also an essential part of materials characterization. Tensile testing, hardness testing, and impact testing are someof the common methods used to evaluate the mechanical properties of materials, including their strength, ductility, and toughness. This data is crucial for assessing the performance of materials under different loading conditions and for ensuring their reliability in practical applications. Furthermore, thermal analysis is another important aspect of materials characterization, as it provides valuable insights into the thermal properties of materials, such as their melting point, thermal conductivity, and specific heat capacity. Techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are used to study the behavior of materials under different temperature conditions, which is essential for understanding their thermal stability and performance in high-temperature applications. Moreover, the characterization of electronic and magnetic properties is also crucial for materials used in electronic devices,magnetic storage media, and sensor applications. Techniques such as electrical conductivity measurements, magnetization measurements, and Hall effect measurements are used to evaluate the electrical and magnetic behavior of materials, providing valuable information for the development of advanced electronic and magnetic materials. Overall, materials characterization plays a vital role in advancing scientific knowledge and technological innovation. By understanding the properties and behavior of materials at a fundamental level, researchers and engineers can develop new materials with tailored properties and improved performance, leading to the development of advanced technologies and products that benefit society as a whole. Therefore, continued research and development in materials characterization are essential for driving progress in various fields, from materials science and engineering to electronics, energy, healthcare, and beyond.。
Materials Characterization
Materials Characterization Materials characterization is a crucial aspect of materials science and engineering. It involves the study of the physical, chemical, and mechanical properties of materials to understand their behavior, performance, and suitability for various applications. The characterization process involves a range of techniques and methods, including microscopy, spectroscopy, thermal analysis, and mechanical testing, among others. In this response, I will discuss the importance of materials characterization, the different techniques used, and their applications.Materials characterization is essential for understanding the properties of materials, which is critical for their selection and design for specific applications. For instance, in the aerospace industry, materials characterization is essential for selecting materials that can withstand high temperatures, pressures, and corrosive environments. In the medical field, materials characterization is crucial for designing implantable devices that are biocompatible and can withstand the harsh physiological environment. In the electronics industry, materials characterization is essential for developing materials with specific electrical properties, such as conductivity, resistivity, and dielectric constant.There are various techniques used in materials characterization, each with unique advantages and limitations. Microscopy techniques, such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), are used to study the microstructure of materials at high magnification. These techniques provide information on the size, shape, and distribution of particles, grain boundaries, and defects in materials. Spectroscopy techniques, such as Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy, are used to study the chemical composition and molecular structure of materials. These techniques provide information on the functional groups, chemical bonds, and molecular vibrations in materials.Thermal analysis techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are used to study the thermal behavior of materials. These techniques provide information on the melting point,crystallization, decomposition, and thermal stability of materials. Mechanical testing techniques, such as tensile testing and hardness testing, are used to study the mechanical properties of materials. These techniques provide information on the strength, ductility, toughness, and elasticity of materials.The applications of materials characterization are diverse and span across various industries. In the automotive industry, materials characterization is essential for selecting materials that are lightweight, strong, and corrosion-resistant. In the construction industry, materials characterization is crucial for selecting materials that are durable, weather-resistant, and fire-resistant. In the energy industry, materials characterization is essential for developing materials that can withstand high temperatures and pressures in power generation and transmission systems. In the food industry, materials characterization is crucial for developing packaging materials that can preserve the quality and freshness of food products.In conclusion, materials characterization is a critical aspect of materials science and engineering. It involves the study of the physical, chemical, and mechanical properties of materials to understand their behavior, performance, and suitability for various applications. The characterization process involves a range of techniques and methods, including microscopy, spectroscopy, thermal analysis, and mechanical testing, among others. The importance of materials characterization cannot be overstated, as it is essential for selecting and designing materials for specific applications in various industries.。
in-depth characterization 表征
in-depth characterization 表征1. 什么是表征？表征是文学、影视、艺术等文化产品中的一个重要概念，它指的是通过文字、形象、情节等手段来描绘一个人物、事件或者场景的特征和性格。
在文学中，表征是通过人物的言行举止、外貌、性格等方面来描写人物形象的，这些描写能够使读者更好地理解人物的内心世界和行为动机；在影视中，表征则是通过演员的表演、画面的构图、音乐等方面来展现电影中的人物、情节和场景。
2. 表征的作用表征在文化产品中扮演着重要的角色，它不仅能够帮助读者或者观众更好地理解作品中的人物、事件和情节，还能够让作品更加生动、有趣。
通过表征，读者或观众能够更加深入地了解人物的性格和特征，从而更好地理解和感受故事情节的发展和人物之间的互动关系。
此外，表征还能够让作品更加生动，有趣，让读者或观众更容易投入到作品的世界中，感受其中的情感和故事。
3. 表征的类型表征有多种类型，包括直接表征、间接表征等。
直接表征指的是通过文字或者画面直接描写人物的特征和性格，例如描述一个人物的外貌、言行举止等方面。
而间接表征则是通过人物的行为、对话等来描写人物的性格和特征，让读者或观众通过人物的行为来推测人物的性格和特征。
4. 表征的例子在《红楼梦》中，贾宝玉的表征就体现了直接表征和间接表征的特点。
在小说中，作者通过描写贾宝玉的外貌、性格等方面来直接表征他的个性；同时，通过他的行为、与其他人物的互动等方面来间接表征他的性格和特征。
在电影《阿甘正传》中，主角阿甘的表征也非常典型。
影片通过演员的表演、画面的构图等方式来表征阿甘的特征和性格，例如他的傻气、善良等，这些表征让观众更好地了解阿甘的内心世界和性格特征，从而更好地感受故事情节的发展。
5. 总结表征是文化产品中一个非常重要的概念，通过表征，作品能够更好地描绘人物、情节和场景的特征和性格，让读者或观众更好地理解和感受作品中的情感和故事。
同时，表征也有多种类型，包括直接表征、间接表征等，这些类型的表征都能够为作品增添生动、有趣的元素。
in-depth characterization 表征
in-depth characterization 表征“深度描写角色人物”的表征法是一种通过对人物的言行、思想、性格等方面的刻画，使人物形象得以深入而细致地展现出来的一种写作手法。
这样的“表征法”，在文学作品中已经得到广泛应用，在剧本、小说、散文等文学形式中都可见其踪影。
下面我们将以小说人物为例，探讨一下如何通过深度描写角色人物实现优秀文学作品中人物形象的丰满与柔和。
一、言行记载角色的动作和行为，而情感和人物关系的反应则能更准确地表征角色。
如同在罗曼·罗兰的《江苏]中，尼奥和萨玛伊尔之间的会话，从中我们可以看到尼奥极度紧张和不安，这是因为他一直在为他在萨玛伊尔身上所看到的症状苦恼，并且他也明白这可能意味着一个最终的结局，这让我们能够更加深入地了解角色，并且通过与其他角色的交互作用，我们能够更加深刻地了解这个角色。
二、语言独白以及对话这类的话语，在文学作品中被大量运用，通过这些语言的互动，我们可以更加明确地了解角色，甚至进一步挖掘角色的个性特征和性格。
例如，在约翰·切瑞的《2013》中，主人公直接地与读者交流，通过机智的幽默和诙谐的形式，我们可以深入了解这个人物的性格和为人处事的方式，并随之体会到这个角色的喜怒哀乐。
三、心理深度这里所说的“心理深度”，即是对角色内心世界的刻画。
在文学作品中，通过对角色的思考、反思、内心独白等手法进行描写，让我们产生对于角色的共鸣，并帮助我们更好地理解这个角色。
如在陀思妥耶夫斯基的《罪与罚》中，主人公拉斯科尔尼科夫的内心世界的抉择、挣扎和翻盘，构成了一个鲜活的角色形象，也让这个角色更加生动鲜活。
总之，深度描写角色人物能够让我们更好地了解角色的个性特征和个性化表现，便于我们更加真实地表达文化的深邃内涵，同时也在文学作品中，增强了别样的审美体验。
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Characterization and properties of in situ emulsion polymerized poly(methyl methacrylate)/graphene nanocompositesTapas Kuila a ,Saswata Bose a ,Partha Khanra a ,Nam Hoon Kim b ,Kyong Yop Rhee a ,b ,c ,Joong Hee Lee a ,b ,d ,⇑aDepartment of BIN Fusion Technology,Chonbuk National University,Jeonju,Jeonbuk 561-756,Republic of KoreabDepartment of Hydrogen and Fuel Cell Engineering,Chonbuk National University,Jeonju,Jeonbuk 561-756,Republic of Korea cSchool of Mechanical Engineering,Kyung Hee University,Yongin 446-701,Republic of Korea dBIN Fusion Center,Department of Polymer and Nano Engineering,Chonbuk National University,Jeonju,Jeonbuk 561-756,Republic of Koreaa r t i c l e i n f o Article history:Received 12March 2011Received in revised form 18August 2011Accepted 19August 2011Available online 27August 2011Keywords:GrapheneB.Mechanical properties D.Thermal analysis B.Electrical propertiesa b s t r a c tPoly(methyl methacrylate)(PMMA)/graphene nanocomposites were prepared by in situ emulsion poly-merization.Raman and Fourier transform infrared spectra showed that PMMA polymer contained par-tially reduced graphite oxide.Dynamic mechanical analysis and differential scanning calorimetry analysis showed that graphene in the PMMA matrix acted as reinforcing filler;it enhanced the storage moduli and glass transition temperatures of the nanocomposites.Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased by ca .35°C.The electrical conductivity of nanocomposite with 3wt.%graphite oxide was 1.5S m À1at room temperature.Ó2011Elsevier Ltd.All rights reserved.1.IntroductionThe use of graphene as nanofiller in polymer nanocomposites has attracted significant research interest.The addition of very small amounts of graphene has been found to improve the mechan-ical,thermal,and electrical properties of the nanocomposites [1,2].Kotov reported graphene as being the most suitable filler,better than carbon nanotubes and other conventional nanofillers [3].However,the degree of dispersion of pure graphene is very poor in polymer matrices.Surface-modified graphene can more easily disperse in an organic polymer matrix to form polymer anic functionality in the modified graphene makes it more compatible with the organic polymer.With a suitable distri-bution of graphene in the polymer matrix,nanocomposites can ex-hibit improved mechanical,thermal,electrical,and gas barrier properties [4–8].The distribution of graphene depends on factors such as the type of modification,the technique of composite prep-aration,and the presence of polar groups in the polymer matrix or in the filler [2].Organic isocyanate-modified graphene,dodecyl amine-modified graphene and ionic liquid-modified graphene have been used to prepare polymer/graphene nanocomposites [9–11].In these nanocomposites,solution mixing was used to aid the disper-sion of graphene.Zhang et al.and Kim and Macosko prepared poly-ethylene terephthalate/graphene and polycarbonate/functionalized graphene nanocomposites by melt mixing [12,13].Functionalized graphene can enhance thermal and mechanical properties of the nanocomposites,but it is not considered a good conducting filler due to the presence of insulating surface-modifying agents.To avoid the use of surface-modified graphene,Hu et al.employed in situ emulsion polymerization for the preparation of polysty-rene/graphene nanocomposites from styrene monomer and pure graphene oxide nanofiller [1].The use of unmodified graphene was shown to improve the thermal stability and electrical conduc-tivity of the nanocomposites.Poly(methyl methacrylate)(PMMA)is an important colorless polymer with high light transmittance,and resistance to chemical and weathering corrosion.These properties give it applicability in additives,coatings and polishing agents,binders,sealers,transpar-ent neutron stoppers,optical fibers,high-voltage applications,and outdoor electrical applications [14].However,bulk PMMA often lacks suitable thermal stability and mechanical properties.Thus,to improve these,different nanomaterials have been used as fillers.Carbon-based nanofillers such as exfoliated graphite (EG),graphite nanoplatelets (GNP),carbon nanofibers (CNF)and carbon nano-tubes (CNT)are well used in making PMMA nanocomposites [15–18].Graphene is another alternative nanomaterial that is much cheaper and more easily synthesized than CNT [3]and its use as conducting filler in PMMA nanocomposites has attracted strong research interest [19–21].The presence of unmodified graphene,compared with functionalized graphene,is anticipated to enhance the thermal and electrical properties of the nano-1359-835X/$-see front matter Ó2011Elsevier Ltd.All rights reserved.doi:10.1016/positesa.2011.08.014⇑Corresponding author at:Department of BIN Fusion Technology,Chonbuk National University,Jeonju,Jeonbuk 561-756,Republic of Korea.Tel.:+82632702342;fax:+82632702341.E-mail address:jhl@chonbuk.ac.kr (J.H.Lee).composites.Therefore,this work reports the preparation of PMMA/unmodified graphene nanocomposites through the emulsion polymerization of methyl methacrylate monomer in graphite oxide dispersions.It provides a path to obtain a new class of graphene-based PMMA nanocomposites.The present study also discusses the characterization of the resulting nanocomposites by different physicochemical methods.2.Experimental 2.1.MaterialsNatural flake graphite was purchased from Sigma Aldrich (Steinheim,Germany).Sulfuric acid,hydrochloric acid,and hydro-gen peroxide were purchased from Samchun Pure Chemical Co.Ltd.,(Pyeongtaek-si,Korea).Oxidizing agent,potassium permanga-nate,was purchased from Junsei Chemical Co.Ltd.,Japan.Sodium dodecyl sulfate (SDS)was used as an emulsifier (Showa Chemical Co.Ltd.,Tokyo,Japan).Azobisisobutyronitrile (AIBN)(Junsei Chem-ical Co.Ltd.,Tokyo,Japan)was used as the initiator.The monomer,methyl methacrylate (MMA)(TCI,Tokyo,Japan),was washed with dilute alkali and distilled water,dried over calcium chloride,and distilled under reduced pressure.The reducing agent,hydrazine monohydrate (TCI,Tokyo,Japan),was used as received.2.2.Synthesis of polymethyl methacrylate/graphene nanocomposites Graphite oxide was prepared by a modified Hummers method [22].For the preparation of nanocomposites,0.1g graphite oxide was ultrasonically dispersed in 100mL water for 1h.In a 500mL Wits apparatus,2.0g SDS was dissolved in 100mL distilled water,to which the graphite oxide dispersion was added and stirred forusing a Nicolet 6700spectrometer over a wave number range of 4000–400cm À1.X-ray diffraction (XRD)studies were carried out at room temperature on a D/Max 2500V/PC,Rigaku Corporation,Japan.All TEM images were recorded on an H-7650(Hitachi-Japan)with an acceleration voltage of 100kV.Field emission scanning elec-tron microscopy (FE-SEM)was carried out with a JSM-6701F (JEOL,Japan).Dynamic mechanical analysis (DMA)of neat PMMA and its nanocomposites (PMG)was carried out with a Q 800DMA (TA instruments,USA).Differential scanning calorimetry (DSC)of the nanocomposites was performed with a TA instruments Q-20be-tween 60and 200°C (5°C/min).The thermal stabilities of the result-ing nanocomposites were measured on a Q50TGA (TA instruments,New Castle DE,USA)at a heating rate of 5°C/min between 60and 600°C in a nitrogen atmosphere.The electrical conductivity of the nanocomposites were measured with Keithley 2000apparatus (Keithley Instruments Inc.,Cleveland,Ohio,USA).The powder samples were compacted into disks of 12.6mm diameter under a pressure of 10tons.Each presented data is an average of measure-ments from five samples.3.Results and discussion 3.1.Raman spectra analysisFig.1shows the Raman spectra of graphite oxide,CR-GO,and PMG1nanocomposites.Two intense peaks are present in the graph-ite oxide:the D band at 1344cm À1and the G band at 1589cm À1.The G band peak was assigned to the first order scattering of E 2g phonons by sp 2C atoms.It was found that the G band of graphite oxide was shifted to 1583cm À1and 1575cm À1in CR-GO and PMG1,respectively.On the contrary,the D band was shifted to 1336cm À1and 1320cm À1,respectively.Moreover,the ratio of T.Kuila et al./Composites:Part A 42(2011)1856–18611857PMG1(a)at lower and(b)higher magnification showing the homogeneous dispersion of graphene in the PMMA matrix.figure legend,the reader is referred to the web version of this article.)It is also evident that the TEM images are almost entirely filled with the graphene sheets,even though the concentration of poly-mer is very high [9].Fig.5a–d shows FESEM images of nanocom-posites PMG1and PMG2at low and high magnification.TheyThe measurement of storage moduli at different temperatures (Table 2)shows that E 0generally increased as the content of filler increased.This was due to the reinforcing effect of graphene.The presence of graphene in the PMG nanocomposites restricted the Fig.7.Variation of tan d of PMMA,PMG1and PMG2with temperature.(For interpretation of the references to color in this figure legend,the reader is referred the web version of this article.)Thermogravimetric analysis assessed the thermal stabilities of PMMA,PMG1and PMG2.Fig.9shows that the onset degradation initial thermal degradation and observed weight loss.However,the final degradation temperature of PMG2was significantly raised.The TGA plots show that the char residue contents in PMG1and PMG2were ca .1.07and 8.6%,respectively.The graph-ene content of PMG1was consistent with the experimental data.However,the PMG2had a char residue >8wt.%,attributable to the presence of charred graphene layers inhibiting further thermal degradation of the PMMA molecules.The electrical conductivities of the PMG nanocomposites were measured by four-point probe using pressed disk-type specimens at room temperature.They were 0.99and 1.50S m À1,respectively,for PMG1and PMG2.The conductivity of pure PMMA is approxi-mately 10À14S m À1,as reported in previous work [18].Therefore,the addition of low levels of graphene to PMMA matrices could sig-nificantly increase electrical conductivity by forming the conduct-ing networks in the composites.4.ConclusionsPMMA/graphene nanocomposites were synthesized via in situ emulsion polymerization.Raman and FTIR analyses showed that PMMA has some graphite oxide or possibly graphene in it.XRD and TEM images of the nanocomposites showed nano-level disper-sions of graphene throughout the polymer matrices.The homoge-neous coating of the polymer matrix on the graphene surfaces was studied by FE-SEM.DMA showed that the storage moduli of the nanocomposites were higher than that of neat PMMA.T g of the nanocomposites found by DMA and DSC were show to be 12°C higher than that of PMMA.The enhancements of E 0and T g was due to the strong interactions between the polar groups of PMMA and remaining oxygen functionality of the graphene.Thermal and electrical properties of the nanocomposites also increased significantly 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