硅酸盐瓷石中氧化钙的直接快速测定

测定硅酸盐陶瓷原料中的氧化钙,历来都必须把其中的硅首先分离除去方能进行,常用有盐酸蒸发脱水和动物胶沉淀等方法,使硅成为不溶物而滤去,这样既费时又烦琐。但若不分离硅,当络合滴定测定氧化钙时,硅部分成白色凝胶片状物析出,严重地干扰氧化钙的滴定终点。我们在实际工作中要求单独测定钙时,常须化费大量的时间和精力分离硅。为解决这一难题,我们通过了反复实验,初步得出了不分离硅直接滴定钙的新方法。实验研究了我们制瓷的一种主要原料瓷     

Synthesis of hexagonal boron nitride films by dual temperature zone low-pressure chemical vapor deposition

Hexagonal boron nitride (h-BN) films are synthesized by dual temperature zone low-pressure chemical vapor deposition (LPCVD) through using a single ammonia borane precursor on non-catalytic c-plane Al₂O₃ substrates. The grown films are confirmed to be h-BN films by various characterization methods. Meanwhile, the growth rates and crystal quality of h-BN films at different positions in the dual temperature zone are studied. It is found that the growth rates and crystal quality of the h-BN films at different positions on the substrate are significantly different. The growth rates of the h-BN thin films show their decreasing trends with the rearward position, while the crystal quality is improved. This work provides an experimental basis for the preparation of large area wafer thick h-BN films by LPCVD.