Fabrication of titanium carbide / carbon functionally gradient materials by chemical vapor deposition

本文尝试用化学气相沉积法设计和制备TiC/C功能梯度材料（FGM），该材料具有从C到TiC的成分梯度。在制备TiC/C FGM之前，我们进行了以下几个方面的基础研究：(1)碳化硅和碳的制备，(2)SiC/C功能梯度材料的制备，(3)碳化钛-碳复合材料的制备，(4)TiC/C功能梯度材料的制备。通过控制沉积过程中气相Si/C的比值，在衬底上获得了由C到SiC组成梯度的片状沉积。很明显，这些材料具有良好的热障特性和抗热震性。采用TiCl_4-CH_4-H_2气体体系，在沉积温度为1573 ~ 1773K，总气压为1.3 ~ 6.5 kPa的条件下制备了不同碳含量的TiC-C复合材料。通过x射线衍射（XRD）测试表明，复合材料由非晶碳和化学计量TiC组成。在40 mol%C范围内，TiC-C复合材料的孔隙率低于SiC-C复合材料。多孔TiC-40mol%C复合材料具有低导热系数和低杨氏模量。因此，TiC-40mol%C涂层后具有优异的热障和残余热应力松弛特性。在沉积温度为1673K，总气压为1.3kPa的条件下，通过改变输入气体中的C/Ti比，在石墨衬底上获得了TiC/C FGM。

Design and preparation of TiC/C Functionally Gradient Materials (FGM) by chemical vapor deposition having a compositional gradient from C to TiC, have been attempted. Before fabricating TiC/C FGM, we have some fundamental researches, as follows: (1)Preparation of Silicon carbide and Carbon, (2)Fabrication of SiC/C Functionally Gradient Materials, (3)Preparation of Titanium carbide-carbon composites, (4)Fabrication of TiC/C Functionally Gradient Materials.Plate-like deposits having a compositional gradient from C to SiC was obtained on a substrate by controlling the Si/C ratio in the gas phase during deposition. It was clean that these materials had a good thermal barrier characteristics and thermal shock resistance.TiC-C composites having various carbon content were prepared at deposition temperature of 1573 to 1773K, total gas pressure of 1.3 to 6.5 kPa using TiCl_4-CH_4-H_2 gas system. It was clear that the composites were composed of amorphous carbon and stoichiometric TiC by XRD measurement. Porosity of TiC-C composites in the range of 40 mol%C are lower than that of SiC-C composites.TiC-40mol%C composite having a few amount of pore has a low thermal conductivity and low young's modulus. Therefore TiC-40mol%C has a superior thermal barrier and residual thermal-stress relaxation characteristics after coating.TiC/C FGM was obtained on a graphite substrate by changing C/Ti ratio in input gas at deposition temperature of 1673K, total gas pressure of 1.3kPa.