纳米材料和纳米结构第五讲PPT课件
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Final size determination of spherical silica particles
➢ Initial concentration of water ➢ Type and concentration of catalyst ➢ Types of silicon alkoxide (methyl 甲基, ethyl 乙基, butyl丁基,
纳米材料和纳米结构
溶胶-凝胶法 Sol-gel Processing
第1五讲
第一部分
整体概述
THE FIRST PART OF THE OVERALL OVERVIEW, PLEASE SUMMARIZE THE CONTENT
2
1 General Introduction
Based on inorganic polymerization reactions（无机聚合反应） Used to prepare inorganic oxides, such as glasses or ceramics, especially multicomponent systems（多组分体
系） Be able to control the structure on nanoscale from the earliest stages of processing Easy to obtain nanostructured grains with compositional homogeneity（组分均匀性）, higher purity, lower
3
Principles
The sol-gel technique to material synthesis is based on some organic precursors（先驱物）, and the gels may form by network growth from an array of discrete particles or by formation of an interconnected 3-D net work by the simultaneous hydrolysis and polycondensation（缩聚作用） of organometallic（有机金属） precursors. The size of the sol particles depend upon some variable factors such as pH, solution composition, and temperature etc.. By controlling the experimental conditions, one can obtain the nanostructured target materials in the form of powder or thin film.
Step 1 Hydrolysis and Polycondensation Liquid alkoxide precursor and Si(OR)4 is mixed with water and acid or ammonia, where R represents CH3, C2H5, or C3H7 and acid or ammonia acts as catalyst. The following hydrolysis reaction will take place:
6
The hydrated silica tetrahedra（水合硅氧四面体）interact in a condensation reaction（缩合反
应）, forming
bonds:
Linkage of additional tetrehedra occurs as a polycondensation reaction and eventually results in a SiO2 network, while the water and alcohol expelled from the reaction remain in the pores of the net work.
processing temperatures over both conventional ceramic processing and traditional glass melting by controlling the chemical additives（添加剂） and processing, but without adopting vacuum conditions
4
2 Experimental Approach
Based on the difference of the precursors used, the sol-gel processing is roughly divided into three groups: Silica （二氧化硅）sol-gel processing Metal alkoxide （金属醇盐）processing Pechini-type processing
5
2.1 Silica Sol-Gel Processing
The whole silica sol-gel processing could be divided into three steps: hydrolysis and polycondensation, gelation and drying.
7
8
The hydrolysis and polycondensation reactions initiate at numerous sites within the TMOS +
H2O solution as mixing occurs. When sufficient interconnected region, they respond cooperatively as colloidal particles or a sol.
Final size determination of spherical silica particles
➢ Initial concentration of water ➢ Type and concentration of catalyst ➢ Types of silicon alkoxide (methyl 甲基, ethyl 乙基, butyl丁基,
纳米材料和纳米结构
溶胶-凝胶法 Sol-gel Processing
第1五讲
第一部分
整体概述
THE FIRST PART OF THE OVERALL OVERVIEW, PLEASE SUMMARIZE THE CONTENT
2
1 General Introduction
Based on inorganic polymerization reactions（无机聚合反应） Used to prepare inorganic oxides, such as glasses or ceramics, especially multicomponent systems（多组分体
系） Be able to control the structure on nanoscale from the earliest stages of processing Easy to obtain nanostructured grains with compositional homogeneity（组分均匀性）, higher purity, lower
3
Principles
The sol-gel technique to material synthesis is based on some organic precursors（先驱物）, and the gels may form by network growth from an array of discrete particles or by formation of an interconnected 3-D net work by the simultaneous hydrolysis and polycondensation（缩聚作用） of organometallic（有机金属） precursors. The size of the sol particles depend upon some variable factors such as pH, solution composition, and temperature etc.. By controlling the experimental conditions, one can obtain the nanostructured target materials in the form of powder or thin film.
Step 1 Hydrolysis and Polycondensation Liquid alkoxide precursor and Si(OR)4 is mixed with water and acid or ammonia, where R represents CH3, C2H5, or C3H7 and acid or ammonia acts as catalyst. The following hydrolysis reaction will take place:
6
The hydrated silica tetrahedra（水合硅氧四面体）interact in a condensation reaction（缩合反
应）, forming
bonds:
Linkage of additional tetrehedra occurs as a polycondensation reaction and eventually results in a SiO2 network, while the water and alcohol expelled from the reaction remain in the pores of the net work.
processing temperatures over both conventional ceramic processing and traditional glass melting by controlling the chemical additives（添加剂） and processing, but without adopting vacuum conditions
4
2 Experimental Approach
Based on the difference of the precursors used, the sol-gel processing is roughly divided into three groups: Silica （二氧化硅）sol-gel processing Metal alkoxide （金属醇盐）processing Pechini-type processing
5
2.1 Silica Sol-Gel Processing
The whole silica sol-gel processing could be divided into three steps: hydrolysis and polycondensation, gelation and drying.
7
8
The hydrolysis and polycondensation reactions initiate at numerous sites within the TMOS +
H2O solution as mixing occurs. When sufficient interconnected region, they respond cooperatively as colloidal particles or a sol.