活化熔渗法制备结构功能一体化MSix-RSiC复合材料及其电热传输机理研究

Metal silicide MSix, such as MoSi2, Ti5Si3, etc., exhibits high melting point, excellent electrical and thermal conductivity as well as high temperature oxidation resistance properties, etc.. It reveals broad application prospects in the field of aerospace and high temperature heating resource, when works as high temperature structural and heating element materials. While the poor low temperature brittleness and high temperature creep resistance is a block restricting its application in the abovementioned fields. Recrystallized silicon carbide (RSiC) possesses excellent high temperature mechanical and thermal properties. The project intends to combine the excellent properties of MSix with that of RSiC to design and prepare an excellent performance MSix-RSiC composite integrated with structure and function. Research thought of this project is that RSiC is used as matrix, which possesses a typical three-dimensional communicating hole structure, the organic resin impregnation-pyrolysis (PIP) and MSix-N-Si(N= Ti, Cr, ect.) active-infiltration (MI) composite technology are employed to prepare a three-dimensional interpenetrating network structure MSix-RSiC composite. Analysing the influence of matrix hole characteristic on the interface combination of matrix and impregnation (melting) phase, searching the evolution mechanism of alloy composition optimization and active-infiltration process, clarifying the interaction law of composition design, microstructure regulation with the electric and thermal conductivity mechanism of MSix-RSiC composite, establishing the electric and thermal conductivity conductivity model based on the three-dimensional interpenetrating network structure. The results can be used as theoretic base and experimental guide for MSix-RSiC composite integrated with structure and function at high temperature application.

MSix类金属硅化物(如MoSi2、Ti5Si3等)熔点高，导电、导热和高温抗氧化等性能优异，作为高温结构和电热元件材料在航空航天、高温热源等领域具有广泛的应用前景，但低温脆性和高温抗蠕变性差是制约其应用的瓶颈。本项目拟将其与高温力学和热学性能优异的再结晶碳化硅(RSiC)进行复合，设计并制备一种综合性能优异的结构功能一体化MSix-RSiC复合材料。研究思路为：以具有三维连通孔结构的RSiC为基体，通过有机树脂浸渍裂解和MSix-N-Si(N=Ti，Cr等)合金活化熔渗工艺制备具有三维互穿网络结构的MSix-RSiC复合材料。分析基体孔特性对基体浸(熔)渗相界面结合性的影响规律；探讨合金组成优化与活化熔渗的演变机理；阐明MSix-RSiC复合材料组成设计、微观结构调控和电热传输机理的相互作用规律，建立基于三维互穿网络结构复合材料的电热传输模型，为其在高温领域的应用奠定理论基础和实验依据。

MSix类金属硅化物(如MoSi2、Ti5Si3等)熔点高，导电、导热和高温抗氧化等性能优异，作为高温结构和电热元件材料在航空航天、高温热源等领域具有广泛的应用前景，但低温脆性、高温力学和抗蠕变性差是制约其应用的瓶颈。将其与高温力学和热学性能优异的再结晶碳化硅(RSiC)进行复合，设计并制备一种综合性能优异的结构功能一体化MSix-RSiC复合材料，可望解决这类材料存在的上述问题。.研究主要以具有三维连通孔结构的RSiC为基体，通过酚醛树脂浸渍-裂解和MSix- Si - X (X = Ti，Cr、Al等)合金活化熔渗工艺制备具有三维互穿网络结构的MSix-RSiC复合材料。研究了基体密度、浸渍-裂解工艺、合金组成和熔渗工艺等对复合材料组成、微观结构、力学和抗氧化、导热和导电等性能的影响，并利用有限元等探讨了材料的电热传输机理。.结果表明：高密度的基体有利于获得综合性能优异的复合材料；浸渍-裂解法可在RSiC材料的孔表面沉积均匀的C层，该层在熔渗过程可与熔渗相生成界面过渡层，有利于获得界面结合性良好的复合材料，进一步提高材料的综合性能；合金活化熔渗能显著降低MSix的熔渗温度，复合材料中少量Si并不影响其高温性能；所得(Ti0.8Mo0.2)Si2-RSiC复合材料的室温强度为136.84 MPa，较基体提高约44%，1400 oC强度为161.3MPa，较基体提高约46 %；体积电阻率为0.34•cm，约为基体的1/14；1300 oC的导热系数为43.12 W•(m•oC)-1，约为基体的2倍。.复合材料的电热传输机理主要受三维互穿网络结构和界面结合性的影响，当材料中基体相和熔渗相的界面结合性较差时，相界面不存在电和热载流子的“渗滤”行为，载流子在两相中分别传输；当复合材料中界面结合性较好时，界面处产生“渗滤”电流，存在从基体的“载流子导电”到熔渗相的“电子导电”的复合导电机理，界面结合性对材料导电性能的影响较小，互穿网络结构的影响因子约为0.4-0.6；基体SiC材料的导热载流子-声子与熔渗相的导热载流子-电子在界面处产生“协同效应”，从而提高复合材料的导热性能，增幅受界面层组成、厚度、缺陷等因素影响。.研究结果可为这类材料在高温领域的应用奠定理论基础并提供实验依据。