二氧化钛包覆微细金刚石的制备及表征

Preparing and characterizing ultrafine diamond coated with titanium dioxide

以聚乙烯吡咯烷酮(PVP)为偶联剂,钛酸四丁酯(TBOT)为TiO_2前驱体,氨水为催化剂,通过Stber法制备核–壳结构的二氧化钛包覆微细金刚石(UFD@TiO_2),研究溶液pH值、氨水及去离子水的加入量对UFD@TiO_2的影响。采用XRD、SEM及DSC–TG等手段对UFD@TiO_2进行表征,利用三点弯曲法测定添加UFD或UFD@TiO_2的陶瓷结合剂试样的抗折强度,通过SEM观察陶瓷结合剂试样断口的微观形貌。实验结果表明:当溶液pH值约为8,氨水体积分数为0.8%,去离子水体积分数为0.8%时,TBOT水解生成的TiO_2易在金刚石表面异质形核,可获得致密均匀的TiO_2膜层;UFD@TiO_2的起始氧化温度为650℃,比UFD的起始氧化温度583℃提高了67℃;UFD@TiO_2–陶瓷结合剂试样的抗折强度比UFD–陶瓷结合剂试样的抗折强度提高了20.9%。

Using polyvinylpyrrolidone(PVP)as a coupling agent,tetrabutyl orthotitanate(TBOT)as the precursor of titanium dioxide,and ammonia as catalyst,the ultrafine diamond coated with titanium dioxide(UFD@TiO2)with core-shell structure was prepared by St ber method.The influences of the pH value of the solution and the additions of ammonia and deionized water on the formation of UFD@TiO2 were studied.The phase composition,microphotograph and oxidation resistance of UFD@TiO2 were characterized by XRD,SEM and DSC-TG.The flexural strength of specimens of UFD-vitrified bond and UFD@TiO2-vitrified bond was tested by three point bending method.The fracture micro-morphologies of vitrified bond specimens were observed by SEM.Results showed that when the pH value was approximately 8 and the volume fractions of ammonia and deionized water were both 0.8%,TiO2 was heterogeneously nucleated on the surface of diamond with TBOT hydrolysis,evenly forming a dense layer of TiO2 film.The initial oxidation temperature of UFD@TiO2 was 650℃,which was 67℃ higher than that of the UFD.The flexural strength of UFD@TiO2-vitrified bond specimen was 20.9% higher than that of UFD-vitrified bond specimens.