硼-碳热还原法合成纳米SiC-ZrB2复合陶瓷粉体

Synthesis of nano-sized SiC-ZrB_2 ceramic powder mixture by boro-carbothermal reduction method

以ZrSi_2、B_4C和炭黑为原料,采取硼-碳热还原法,分别在1000、1200及1400℃温度下反应,合成纳米SiC-ZrB_2复合陶瓷粉体。采用扫描电镜(SEM)、能谱仪(EDS)及X射线衍射(XRD)对复合粉体的显微形貌、物相组成及晶粒尺寸进行表征;利用热力学计算分析合成过程的反应机理。结果表明:当温度为1000℃时,硼-碳热还原反应并不彻底,粉体中仍存在ZrSi_2未参与反应;当温度升高到1200℃时,反应可完全进行,合成的纳米SiC-ZrB_2复合陶瓷粉体颗粒分布均匀,SiC粒子尺寸约为40 nm,ZrB_2颗粒尺寸约为300 nm;当温度进一步升高到1400℃后,SiC-ZrB_2复合粉体中晶粒长大明显,SiC颗粒附着在ZrB_2颗粒表面,并且复合粉体出现烧结引起的密实现象。

Nano-sized SiC-ZrB2 ceramic powder mixture was synthesized at temperatures of 1000,1200 and 1400℃ by boro-carbothermal reduction method with ZrSi2,B4C and C as raw materials.The morphology,phase composition and crystallite size of the synthesized powder mixtures were characterized by scanning electron microscopy（SEM） with energy dispersive spectrometer（EDS） and X-ray diffractometry（XRD）.Thermo kinetics calculation was also carried out to analyze the synthesis mechanism.The results show that the synthesis reaction can not be completed thoroughly,and unreacted ZrSi2 can be detected in the powder mixtures.At 1200℃,the reaction occurs completely,and both produced particles,SiC and ZrB2,distribute homogeneously in the powder mixtures.The mean sizes of SiC and ZrB2 particles in the powder mixture synthesized at 1200℃ are 40 nm and 300 nm,respectively.At 1400℃,the agglomeration phenomenon of the ceramic powder mixture appears due to the sintering at high temperature.