莫来石-Ti(C,N)复合材料的制备及其力学性能研究

Preparation and Mechanical Properties of Mullite-Ti(C,N) Composites

以TiO_(2)粉、石墨粉、Al/Si/Al_(2)O_(3)复合粉体为原料,在氮气气氛下经1400℃~1600℃保温2 h,采用碳热还原氮化法制备得到莫来石-Ti(C,N)复合材料,研究了烧成温度对复合材料物相组成、微观结构与力学性能的影响。结果表明:经1400℃热处理后,试样的物相组成为Ti(C,N)、SiO_(2)和硅线石。随热处理温度升高至1450℃~1600℃,硅线石消失的同时,试样出现了短柱状莫来石,并与无定形SiO_(2)紧密连接,形成有效的化学结合。当烧成温度为1500℃时,大量开口气孔随颗粒重排、界面移动而消失,材料颗粒间结合较为紧密,气孔数量明显减少,该烧成温度下试样具有最佳综合性能,其体积密度、弹性模量、抗折强度和维氏硬度分别为(3.48±0.02) g·cm-3、(138.5±0.1) GPa、(158.0±0.03) MPa和(21.01±0.01) GPa。

Mullite-Ti(C,N) composites were synthesized using TiO_(2),graphite and Al/Si/Al_(2)O_(3) composite powders as precursors.The samples were subjected to a carbothermal reduction nitridation process at temperatures ranging from 1400 to 1600 ℃ in nitrogen atmosphere for 2 h.The effects of firing temperature on phase composition,microstructure and mechanical properties of the composites were studied.According to X-ray diffraction results,after heat treatment at 1400 ℃,the samples consisted of Ti(C,N),SiO_(2) and cristobalite.With increasing firing temperature to 1450–1600 ℃,cristobalite phase disappeared,while short columnar mullite phase is present,which is intimately bonded to amorphous SiO_(2),resulting in effective chemical bonding.Furthermore,at 1500 ℃,microstructure and mechanical properties of the composites were significantly improved,including a reduction in the number of open pores and an enhancement in particle bonding.The optimized sample had bulk density,elastic modulus,flexural strength and Vickers hardness to be(3.48±0.02) g·cm^(-3),(138.5±0.1) GPa,(158.0±0.03) MPa and(21.01±0.01) GPa,respectively.