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

已经尝试通过化学气相沉积的方法设计和制备具有从C到TiC的组成梯度的TiC/C功能梯度材料(FGM)。在制备TiC/C功能梯度材料之前，我们进行了如下的基础性研究：(1)碳化硅和碳的制备；(2)碳化硅/碳化硅梯度功能材料的制备；(3)碳化钛-碳复合材料的制备；(4)碳化钛/碳化硅梯度功能材料的制备。在TiCl4-CH4-H2气体体系中，沉积温度为1573~1773K，总气压为1.3~6.5kPa时，制备了不同碳含量的TiC-C复合材料。X射线衍射分析表明，复合材料由无定形碳和化学计量比的TiC组成。在40mol%C范围内，TiC-C复合材料的孔隙率低于碳化硅复合材料，具有少量气孔的TiC-40mol%C复合材料具有低的导热系数和较低的杨氏模数。因此，TiC-40mol%C具有良好的热障性能和涂层后的残余热应力松弛特性。在沉积温度为1673K、总气压为1.3kPa时，通过改变进气中的C/Ti比，在石墨衬底上制备了TiC/C功能梯度材料。

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.