材料科学与工程专业课程总结

Process of inorganic materialsInorganic materials are the general name of all the materials except polymers materials. In this course we have mainly learned two kinds of materials, they are pottery and cement.1. Pottery is a kind of inorganic materials, it is fired of natural or synthetical powder materials under high temperature. It can be divided into common pottery like our cup, plate and bowl, and special pottery, they have a number of special functions, like wear resistance, heat resistance and corrosion resistance.In our daily life, we can see a glaze whether in the surface of a bowl, or in the surface of a flower vase. This glaze can isolate gas and liquid, can make the surface easily wash and increase the sense of beauty. The body of pottery can't be without the glaze, but we must be careful, when we choose the materials of glaze. In theory the glaze is the most safe when the thermal expansion coefficient of body and glaze is equal (shows the change ability of volume and length when the materials is heated or cooled). Actually it is impossible. (because the component of body and glaze are different, then the thermal expansion coefficient are different). When the thermal expansion coefficient of glaze is bigger than body, in the cooling process after firing, the glaze shrink more and exist tensile stress, it reduces the strength of pottery and make the glaze breach. But when the thermal expansion coefficient of glaze is smaller than the body, in the cooling process after firing, the glaze shrink less and exist compressive stress, this even distributed compressive stress can increase the strength, but if the thermal expansion coefficient of glaze is too much smaller than the body, the glaze will peel off.2.Cement is also a kind of common materials, it is used for roads, houses and so on. It is a powder materials, and have a strength and hardness after stiffen in the water or in the air, thus satisfy the requirements of people.Here I want to mainly introduce the primary components of silicate cement, they are C3S, C2S, C3A, C4AF.C3S is the maximal component of silicate cement. The content is the most and thestrength is the highest, but the water resistance is not good. Its establishment is as follows:② the earlier strength of C2S is low, but it can continual increase later, and it has good water resistance. Its establishment is as follows③C3A can stiffen in a short time, its earlier strength is high but it will not increase later and it is easily corroded. Its establishment is as follows.④the earlier strength of C4AF is high and it will increase later and is not easily corroded. Its establishment is as follows:Other components: f-CaO, MgO, glassAdvanced technologies for materials characterizationThis course is an experiment methods course and it is about of analysis of structures and components of materials. We have learned the analysis method by X-ray diffractometer and electron microscope.1.Engineering materials are used mostly in polycrystal, so I will mainly introduce the analysis method of polycrystal, the most convenient and exact method is X-ray diffractometer.The sample D is on the test beds H, it can move, S is the X-ray source. When a bunch of emanative X-ray shine on the sample, the reflected ray of crystal face, who meets the Bragg equation, will become a convergent light beam. There is a receive crack in F, C is a counter tube, it can also move, when it goes to a suitable place, it will receive a reflected ray, the position of counter tube can we read from the degree scale. When the sample and the counter tube continual move, the diffractometer will draw the change of diffracted intensity with the change of angle. Then by means of analysis of phase can we get the crystal lattice parameters of the phase.Bragg equation: 2dsinθ=λd is the distance of crystal face, θ is the angle of incident ray and crystal face, λ is the wavelength of X-ray.2.The qualitative analysis①get the diffraction pattern from the X-ray diffractometer, the computer will output dand I of every diffraction maximum automatically.②size the price of d down, choose the 3 biggest .③find the corresponding d1 in the index book, then find the approximate lines according to d2, then according to d3. If d1,d2,d3 of a line are within in the error and the other price of d are also within in the error, then we can make sure this phase is the one we find, record the number of this phase.④find the corresponding card of this number, on which there is the parameters of this phase.3.The quantitative analysisThe diffraction intensity in the pattern increase with the content of the phase, if we want to know the content of one phase, we can use the K value method.I A,I S are the diffracted intensity of phase A and S, w A ,w S are the mass fraction of phase A and S.Add the known content w S of phase S into the sample, get the pattern from the diffractometer, we can read the I A and I S from the pattern, then we can calculate w A . We can get the value of K by means of experiment: mix the same quantity of phase A and phase S, that is to say, m A=m S, here K =Other method: internal standard method, external standard method4.In the analysis method by electron microscope we have learned transmission electron microscope. Its core is imaging system in lens cone. It consists of objective lens, intermediate lens and projective lens. The diffraction pattern is firstly magnified by objective lens, if the magnification factor of intermediate lens is greater than 1, then the pattern will be magnified again, if the magnification factor of intermediate lens is less than 1, the pattern will be shrank. The function of projective lens is to magnify the pattern in the intermediate lens and cast its shadow on the negative picture.Physical chemistry of silicate1.Silicate materials is mainly made up of pottery, cement and glass. In this course we have mainly learned glass. The production of glass is a conversion process of melts and vitreum. Melts and vitreum are the two state of aggregation of substance except solid, gas and liquid.The conversion process of melts and vitreum is a gradual change, it finishes in a temperature range, so the glass have no fixed melting point. For example in this picture, the ordinate is the internal energy and the volume, the horizontal ordinate is the temperature, when the melts is cooled down, when it meets point f, this moment the temperature is T g and have finished the transmission to the solid glass, the dynamic viscosity is 1012pas, usually we defined the temperature as T f when the dynamic viscosity is 108 pas, with the increase of temperature, the dynamic viscosity decrease, so the T f is on the right. When the temperature is higher than T f, all is melts, that is to say, when it meets point b, it begin to turn to the solid glass. The conversion process takes place in the temperature range between T g and T f, so the glass have no fixed melting point. (dynamic viscosity shows the obstruction when the fluid flows, the fluid is a substance that change its shape under a surface paralleled force).2.Diffusion is a common phenomenon in our daily life, the diffusion of solids is the foundation of reactions between solids. For example there is a pile of coal in the corner, after long time, the corner will become black like the color of coal, that is the diffusion of solids, this process is very slow and the path of the particle have no rule, for example like this.When we want to know how many particles take part in this diffusion, then we can use the first law of Fick, J is the quantity of atoms when they pass the cross section in unit time, D is a coefficient, ** is the change of concentration in unit length, the minus sign represent the particle spread along the direction of decrease of concentration.For a solid, its concentration is not uniform, like this, on the left the concentration of a substance is higher than on the right, then this substance will spread from left to right, at last the concentration will be equal , for example in this chart, this is the originalconcentration of left and right, after the diffusion process, the last concentration is between C1 and C2.Fundamentals of metallic materials engineeringIn this course we have learned shaping method. There are many metal products in our daily life, like metal buckets, metal hammers, they are made of raw materials through a certain shaping method. Actually in the production, the most common method is liquid forming. That is to say, melt the metal from solid to liquid , then pour the liquid metal into a mould with a certain shape and size, after the cooling and solidification process we get the product we need. For example, we want to produce a batch of art works with a shape of gourds. Firstly just like I said, melt the metal from solid to liquid, then put the liquid metal into a mould, after cooling and solidification, open the mould and get the work with a shape and size we need.This method is low cost, many obsoleting elements can be used again. On the other word we can get all kinds of shape and size of elements by this method. But the production maybe have a few holes on the surface or inside, it will affect the use and properties of the products, the technology is old and the efficiency is low.2.We have learned another method, for example there is a metal rod, we want to turn it into a shape of cup or U-shape. We put the metal rod on the machine and open the switch, the roller on the machine will bring to bear on the metal rod, then the metal will be out of shape. When we control the height that the roller drop and choose a suitable radius of the roller, then we can get the product with a shape and size we need.3.Actually in the daily life there are many elements, they must bear torsion, bending and changing current and voltage, for example the roller, its surface withstand greater force than the core, if there is a friction force, the surface will gradually wear away. It causes a great damage to the element and decrease the useful life. So we must have a series of treatments on the surface, make it has a higher hardness and strength, but theinside materials keep the original toughness. The toughness is the ability to not to break off, when the element bear the applied force. That is the surface modification of materials.The most common method of surface modification is as follows, put the element into a heating stove and inlet carbon included gas, such as coal gas, liquefied petroleum gas, the gas will conduct a series of reactions such as A and B, and gain carbon atoms. These free carbon atoms spread from surface of the element to inside, thus change the component and the properties of surface.Physical metallurgy1.In this course, I think the most important part is the iron-carbon phase diagram, it is the most primary knowledge of iron-carbon-alloy. It is like that, the ordinate is the temperature, the horizontal ordinate is the content of carbon, this line is the liquidus, this line is the solidus, that is to say, when the liquid with a high temperature cool down and meets the liquidus, it will begin to grow solid, when it meets the solidus, the liquid will disappear. Firstly appear the austenite, because in a high temperature, the inner structure of iron is γ-Fe(gama phase iron), austenite is solid solution of iron, that is to say, carbon enter the structure of iron. Can I use an example to explain the phase diagram? There is a steel, its carbon content is 0.77%, correspond to here in the horizontal ordinate, just like I said, when the steel cool down and meets the liquidus, the liquid begin to appear austenite, when it meets the solidus, there is no liquid and all is austenite, when the temperature continue to fall and meet the point P, the austenite will become to pearlite, it is a mixture of ferrite and cementite, because in a low temperature, the inner structure of iron is α-Fe, cementite is a compound of carbon, the point E is the maximal solubility of carbon in austenite, the point B is the maximal solubility of carbon in ferrite, the solubility of point E is greater, so when the austenite turn to the ferrite, when the austenite turn to the ferrite, there is a small surplus of carbon, then the rest of carbon exist in the state of cementite, the ultima component is pearlite.Through the phase diagram we know the change of component during the coolingprocess and the ultima component of an alloy, we can also see that, if the carbon content is different, the component of steel is different, then the properties is different. So we must choose materials with a suitable carbon content according to the requirement.2.In our daily life, we find that the useful life of many things is shorter than in theory, in contrast the properties is not so good. Because there are defects in the inner structure of materials. In theory, we think the atomic arrangement in the crystal is regular, but under the influence of outside factors, such as radiation, the atomic arrangement in the crystal is not regular, this is defect. The crystal is a solid whose inner particles repeated arrange in the space. For example point defect, the theoretical arrangement is like this, the atom 1 transfer to this state, then the atomic arrangement is disarranged. Other defects like line defect, there are three atomic planes, they arrange regularly, if between these two planes grow a new plane ABCD, result in the atom next to ABCD plane deviate the original state.Properties of materials1.In the engineering there are many elements, they must bear changing applied force, such as gear and bridge. According to statistics, there are 80% of elements and installations lose effectiveness because of fatigue. When the elements work under changing force both in direction and magnitude of force, such as the parts of cars, tractors and airplanes, the force will change as follows when they work. In this situation the inner structure of materials will change and emerge cracks, as time goes on, the cracks will spread and grow up, to a certain extent the elements will break off. That is fatigue failure. The temperature and the magnitude of the force will effect the time, that the fatigue failure emerge. Generally higher temperature and force advanced the emergency of fatigue failure.The materials have many properties such as fatigue properties, wear properties and thermal properties. The wear properties is that, when the machine work, the elements will be worn because of the friction, that is wear-out failure. The thermal properties isthat, the volume and length will change when heated, for example the choose of glaze in process of inorganic materials.2.Many materials have electric conductivity, such as the tungsten wire in the lamp bulb, but these materials have a resistance when they conduct electricity, that is to say, they will have a fever when a current pass through it, then a part of energy will lose. But there is a materials, whose electric resistance will be so low that can't be measured when the temperature is low enough, for example around 0 kelvin, this material is called superconductor. Can I use an example to explain this process? Firstly make a superconductor into a ring and put in a magnetic field at room temperature, just like this, coll off to around 0 kelvin, then take the magnetic field away, because of the magnetic induction, along the ring emerge a current, the electric resistance of the ring is 0, so the energy is not consumed and exist forever. Magnetic induction can be explained as follows, in a closed circuit will produce a induction electromotive force when the quantity of magnetic line of force change, the electromotive force will produce a current.Fundamentals of inorganic materials engineering1.The two objects with different temperatures in contract with each other, or the different parts of one object have different temperatures, then there is a heat transfer, the heat flows from the warmer to the cooler body, this is the heat conduction. It is an important heat transfer mode. All objects have a heat transfer ability, but the quantity is different, the quantity of heat transfer can be calculated according to this formular:*** Q is the quantity of heat transfer, k shows the ability of heat transfer, A is the contract area, the minus sign represent the heat flows from the warmer to the colder body. Can I use an example to explain the process of conduction of heat? I believe all of us have aired quilts, we find that the aired quilts are very warm, because a great deal of air will enter the gap of cotton, in the narrow space the way of heat transfer mainly is the heat conduction , the ability of heat transfer of air namely k air is low, so the quantity of heat transfer is low, thus the insolating effect is good, if thequilt is beaten, more air enters and the effect is better.2.Another important heat transfer mode is heat radiation, it is a process, that the object transfer the heat through the electromagnetic wave. The quantity of heat transfer can be calculated according to this formular:*** Q is the quantity of heat transfer, A is the contract area, εshows the ability to radiate, T1and T2are the temperatures. Can I use an example to explain the process of heat radiation? On the winter evening, the upper surface of the leaves have a sheet of frost, not the under surface. Because the under surface have a heat radiation with ground, the upper surface with space, the temperature of ground is higher and is similar with the temperature of leaves, but the temperature of space is low. So Q upper is more than the Q under, it will frost when the temperature is minus 0 centigrade.3.Fluid is a substance that change its shape under a surface paralleled force, it has no fixed shape and can flow. Gases and liquids are all called fluid. The most important properties of fluid is the thermal expansion, that is to say when the temperature change, the volume and density will change. The most common example is the hot balloon, when the air in the balloon is heated, because of the thermal expansion the volume will increase and the density will decrease,(the mass of the air is fixed, when the volume increase, then the density will decrease. ) when the density is smaller than the density of air in surroundings, the balloon will float. Just like put an object on the surface of the water, whose density is smaller than the water, it floats.Principle and process of heat treatment1.Heat treatment is that, heat the steel to a certain temperature as it is solid, keep warm for a time, then cool off to the room temperature. Its principle is the change of component in the steel. In order to have the properties and component we need after the heat treatment, we usually firstly gain the austenite, then cool off in an appropriate way to get the needed component.The establishment of austenite is as follows, the original component of steel is acombination of ferrite and cementite, the white represents ferrite and the black represent the cementite, when heated, on the edge of cementite grows several austenites, continue to be heated, the austenite will grow up and the cementite will gradual dissolve, after a while the ferrite disappear and the austenite is mature, but there is a small surplus of cementite, because its dissolution is a process of diffusion, it's slow, the dissolution of ferrite is a transformation between ferrite and austenite, both of them are inner structures of iron in different temperatures. With the increase of temperature the cementite will disappear and the austenite become uniform.2.Another technologies of heat treatment are surface modification in fundamentals of metallic materials engineering, and annealing. Annealing is that, heat the metal to a certain temperature, keep warm for a time, cool off slowly to get the component close to equilibrium. By this means make the component of the steel uniform and reduce the force between the different parts, and then improve the functional performance. The windows of cars after heat treatment become to an orbicular piece when break off, they are safe to the human body, but the general glass become to a pointed piece, because the force centralized parts firstly break.Petrography of silicate1.We can observe many properties of crystal under single polarizing microscope, for example at the contract of two objects with different refractive indexes we can see a dark edge, near the dark edge is a bright line, when rise and fall the lens core, the bright line will move. The emergency of this line is attributed to the differences of refractive index of the contiguous objects. Just like this, the refractive index of right is greater, when the light shine on the contract surface, from optically thinner medium to optically denser medium, according to the refraction law, the light will be partial to normal, result in more light at one side, less light at another side, thus emerge the dark edge and bright line. n=c/v, c is the speed of light in space, n is the refractive index, v is the speed of light in the crystal, when the n is smaller, then the v is greater, that is the optically thinner medium. The refraction law: sini/sinr=n r/n i2.In this course we have also learned portland clinker as in process of inorganic materials. Except use microscope to analysis the structure of crystal, we can measure the physical and chemical process by means of differential thermal analysis. Firstly heat the sample and reference material under the same condition, measure the range of temperature between sample and reference material and the relationship with temperature, then make a diagram, that is DTA curve. The ordinate is range of temperature, this part represent the exothermic reaction, the area of this peak represent the quantity of the energy.Mechanics of silicate industry1.The developmental level and the efficiency of a factory to a great extent depend on the integrity and progressiveness of the equipments. Every production line must be finished by mechanical equipments. In the production, massive materials and supplies must be broken to pieces in various degree, then put into the production. The needed equipment is the size reduction machinery, it is the most elementary in the production line, so I want to show you one kind of the size reduction machinery. When the radius of the materials and supplies is required to be between 30-100 millimeter, we usually use jaw crasher. Can I use a picture to explain the principle? 1 and 2 are two boards, 1 is fixed and 2 can move, this is an axel, when it revolves the rod 3 will move up and down like this, the rod and the board 2 are connected at this point, when the rod move, this angle will change and then move the board. When the board 2 is close to the board 1, the materials are squeezed and broken, when the board 2 is away, the broken materials will drop by gravity.2.Sometimes the raw materials is distant from the workshop, so we need transport machineries, such as horizontal and oblique conveyer band. This is a horizontal conveyer band, the principle is the friction force between the materials and the band. This one is oblique, when the materials is transported, different sizes and kinds ofmaterials have a maximal angleβ, if this angle exceedβ,then the materials will slip and leads to decreased efficiency.Thermodynamics of materials1.In this course we have mainly learned the first law and the second law of thermodynamics.The first law can be described by this formular:U=Q+W, the system absorb heat from surroundings, the amount is Q, Q>0, at the same time the system do work on the surroundings, the amount is W, W<0, U shows the change of internal energy, it depends on the original and the ultima conditions, it has nothing to do with the process. But Q and W have a close relationship with the process of the reaction. Can I use an example to explain the first law of thermodynamics? A system change from state 1 to state 2 through the line 1-a-2, it observes 314 Joule heat from the surroundings, and simultaneously do 117 Joule work on the surroundings. If the system reacts through the line 1-b-2, it do 44 Joule work on the surroundings, how much heat it observes from the surroundings? We can use the formular of the first law of the thermodynamics to calculate, the general internal energy is fixed whatever the process is, from the 1-a-2 line, we can know that U equals Q1 adds W1, then in the process 1-b-2, we can calculate Q2. That tis the first law of thermodynamics.2.In nature we find that, the amount of heat will transmit from the warmer to the cooler body automatically, until the temperature of the two objects is unanimous. When different gases meet each other, they usually tend to intermingle with each other, until the gases is totally uniform. These processes are spontaneous, but they can't recover the original state spontaneously.For example the vacuum expansion of ideal gas in adiabatic condition, it is a spontaneous process, Q=0, W=0, so *U=0, then the range of temperature is 0, because the temperature is the only influencing factor of internal energy. If we want to recover the expanded gas to the original state, we must through an isothermal compression, but in the process of compression the surroundings have to do work on the system, theamount is W, at the same time, the system will give out a part of heat, the amount is Q, and Q=W, only in this way can the system recover. If the amount of heat that the system give out can translate into the work completely and lead to no other changes, that is to say Q equals to W, then we can say that is a reversible process. Actually that is impossible. That is the second law of the thermodynamics.The internal energy is the combination of molecular kinetic and potential energy, with regard to ideal gas, the molecular potential energy is too small that is ignored, because the distance between the two molecules is greater than tenfold of the atomic radius. Then the internal energy of ideal gas is the molecular kinetic energy, it depends on temperature.Physical chemistryIn this course we have also learned the first and the second law of thermodynamics, in addition we have learned the electric chemistry, such as primary battery. For example there is a Cu-Zn(copper-zinc) primary battery, its structure is like this. The ammeter is to measure the size of the current. The reactions of poles are like this, zinc lose two electron and become to zinc ion, copper ion gain the two electrons and become to copper, electrons are delivered from the zinc pole to the copper pole, the direction of current is opposite, then the zinc pole is negative electrode, the copper pole is the positive electrode. The electromotive force of this primary battery can be calculated by Nernst equation, for the negative pole, the electromotive force is that, this is the electromotive force of standard state, R and F are constants, n is the amount of the translated electrons, T is the temperature, this is the concentration of zinc ions. The general electromotive force equals E positive minus E negative. When the reactants are solids, they are not involved in the Nernst equation.Fundamentals of materials science1.All substances are formed by countless particles, these particles can be atoms, molecules and ions, when they combine to solids, what kind of combining power make them gathered together? For metals, the atoms interact depends on the freeelectrons and metallic positive ions in the metal, these free electrons are common to all positive ions, they make the metal have good electrical and thermal conductivity. The heat is delivered through the movement of free electrons, and the electrons have a weak resistance to the current. When the metal is under the applied force, the position of atoms will change, but the inner structure will not be destroyed, this make the metal bar can be processed into thin slices without the changing of structure and properties.2.Diffusion and defectPhysics1.In this course we have learned Gauss theorem, it is that, in an electrostatic field in vacuum, the electric flux through any closed surface equals the general charge number surrounded by this surface multiply 1/ε0. Electric flux is the number of electric field line. The formula is as follows:*** E multiply ds is the electric flux, E is the electric field intensity, S is the area, this is the general charge number, ε0 is a constant. Can I use an example to explain the Gauss theorem? There is a uniformly charged straight line, the line density is +λ, the electric field around the line is symmetrical, we find a point P, the distance between the line and the point is r, the direction of electric field of point P can only along the radial direction, other points on the same cylindrical surface with P have a equal electric field strength both in quantity and direction. Then we suppose a cylindrical surface, the electric flux is the product of E and S, S consists of the side, upper surface and under surface, we usually think that, the electric flux is negative when the electric field line through the surface from the outside in, it is positive when the electric field line through the surface from the inside out, then the summation of the electric flux of upper and under surfaces is 0, then the general electric flux depends on the side, the area of the side is 2πrl, E can be regarded as a constant here, so we can write it out of the integral. The general charge number of the closed surface is λl. From the Gauss theorem we can say that.Probability and mathematical statistics。