利用水热合成方法制备正交氮化硼微晶

利用水热方法制备了正交氮化硼微晶, 于400 ℃时制备的氮化硼结晶质量较高, 主要物相为正交氮化硼(oBN). 在反应原料中加入水合肼和氯化铵都有利于样品结晶质量的改善和产率的提高. 在合成氮化硼反应过程中, 适当减慢反应体系的升温速率有利于提高oBN的结晶质量和产率, 但是当升温速率过慢时, oBN的稳定性有所降低, 立方氮化硼(cBN)的稳定性则在一定程度上得到提高. 此外, 反应过程中的原料配比对样品的物相及其结晶质量也有很大影响.

Preparation of Orthorhombic Boron Nitride by Hydrothermal Synthesis Method

High crystalline orthorhombic boron nitride(oBN) crystallites were prepared by hydrothermal synthesis method. Powder X-ray diffraction(XRD) and high resolution transmission electron microscopy(HRTEM) were used to investigate the phases and crystalline perfection of the BN samples. It is found that the samples are of high crystalline and the dominating phase is oBN when the reaction temperature is 400 ℃. Furthermore, the crystalline perfection and yield of the samples can be improved by adding hydrazine hydrate(N2H4·H2O) and ammonium chloride(NH4Cl) to the solution of reaction reagents. In order to obtain oBN crystallites with high crystalline perfection and high yield, the temperature rising speed should be decreased appropriately during the reaction process. However, oBN becomes less stable, and at the same time, the stability of cBN is improved if the temperature rising speed is slow enough. In addition, the molar ratio of the reactants also has important effects on the phases and the crystalline perfection of the BN samples. These results will be of great significance for controlling the phases of BN and preparing pure cBN.