Preparation of Hollow ZrB_2 Spheres by a Combined Sol-gel and Boro/carbothermal Reduction Method

Carbon microspheres were firstly prepared using glucose （C6H12O6 ） as the starting materials by hydrotherreal carbonization. Then hollow ZrB2 spheres were successfully synthesized using zirconium oxychloride （ ZrClO2 · 8H2O）, boric acid （ H3BO3 ） by a combined solgel and boro/carbothermal reduction method, and the prepared carbon microspheres as the template. The effects of the reaction temperatures （1 200, 1 300, 1 400 and 1 500 ℃, respectively） and contents of carbon microspheres （ n （ C ） ： n （ ZrO2 ＋ B2O3） is 5. 0, 5. 5, 6. 0 and 6. 5, respectively） on the synthesis of hollow ZrB2 spheres were studied. The prepared carbon microspheres have smooth sugrace and good hollow structure by hydrothermal nitridation. Increase of reaction temperature and excessive carbon microspheres can greatly promote the formation of hollow ZrB2 spheres. The optimized reaction temperature and molar ratio of n （C）/ n （ ZrO2 ＋ B2O3 ） were 1 500 ℃ and 6.5, respectively.