金刚石/纳米氧化铝陶瓷复合材料高温高压合成物相结构分析

Phase Structure Analysis of Diamond/Nano-alumina Ceramic Composite Synthesized at High Temperature and High Pressure

以正硅酸乙酯(TEOS)为反应前驱体,采用溶胶-凝胶法在金刚石微粉(粒度0.1~4μm)表面包覆一层非晶纳米氧化硅膜层,同时在覆膜层中加入纳米Si粉和纳米Al_(2)O_(3)粉,制备出金刚石/纳米SiO_(2)/纳米Al_(2)O_(3)复合包覆体。采用高温高压(HTHP)技术,将复合包覆材料置于六面顶压机中,以压力5 GPa、温度1100℃~1700℃、保温20 min的条件制备了金刚石-氧化铝陶瓷烧结体。在高温高压合成过程中,纳米SiO_(2)从非晶态转变为晶态,原料纳米Al_(2)O_(3)中的γ-相、θ-相转变为稳定的α-相,同时,SiO_(2)和Al_(2)O_(3)之间形成了Al_(2)SiO_(5)(莫来石)相,由此,通过高温高压下反应原料的结构转变与复合,可以获得致密度良好的金刚石-氧化铝复合材料。

Tetraethyl orthosilicate(TEOS)was used as a precursor to coat an amorphous nano-SiO_(2)film on the surface of the fine-grained diamond powders(0.1-4μm)by sol-gel method,meanwhile,some nanoparticales of silicon and alumina were also added to the coated film to form diamond composite particles.Using high temperature and high pressure(HTHP)technique,The sintered body was obtained by placing the as-prepared diamond composite in a cubic press under conditions of pressure 5 GPa,holding for 20 minutes at different temperatures ranging from 1100℃to 1700℃.During the HTHP process,nano-SiO_(2)phase in the coated film transforms from an amorphous state to a crystalline state,and the raw powders of nano-Al_(2)O_(3)transformes fromγ-phase andθ-phase to the stableα-phase,furthermore,an Al_(2)SiO_(5)(mullite)phase was formed between SiO_(2)and Al_(2)O_(3).Finally,through the structural transformation and combination of reaction materials under HTHP conditions,a kind of diamond-alumina composite with good density can be obtained.