Synthesis of Ultra-fine ZrB_2-ZrC Composite Powders by Inorganic Sol-gel Method

Based on the basic principle of carbothermal reduction reactions in the ZrO_2-B_2O_3-C system,ultra-fine ZrB_2-ZrC composite powders were synthesized by sol-gel method using zirconium oxychloride,boric acid and phenolic resin as sources of zirconia,boron oxide and carbon,respectively. Thermodynamic change process,phase compositions,crystallite size and morphology of the synthe- sized powders were characterized by thermogravimetry-differential thermal analysis,X-ray diffraction and scanning electron microscope.The results show that ZrB_2 and ZrC phases form at 1300℃.The carbothermal reduction reactions are completely finished when calcined at 1500℃for 1h.The average crystallite size and specific surface area are about 200nm and 87m~2/g,respectively.The agglomeration phenomenon is improved by adding 1.0wt% polyethylene glycol.