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为了在较低温度和较短时间内合成h-BN 粉体，以硼砂和镁粉为原料，以n（NaCl）n（MgCl2）分别为13、11和31的3种NaCl－MgCl2和n（KCl）n（MgCl2）为11的KCl－MgCl2为熔盐介质，在氮气气氛中分别于800、1000和1200℃保温3 h，采用镁热还原法合成h-BN，经5％（w）的盐酸溶液浸泡、抽滤、洗涤、干燥、研磨后得到产物粉体，并进行XRD和SEM分析，研究了不同种类和配比的熔盐介质及合成温度对合成产物的物相组成和显微结构的影响。结果表明：1）在本试验的不同熔盐介质和不同温度下合成的产物粉体均由纯相h-BN组成，但h-BN的结晶度随合成温度的升高而逐渐提高：在NaCl－MgCl2熔盐介质中于1000℃制备的产物中有片状h-BN，在1200℃出现层叠层片状h-BN，而在KCl－MgCl2熔盐介质中于1200℃才有片状h-BN。2）在NaCl－MgCl2熔盐中通过镁热还原法合成h-BN粉体，不仅克服了其他方法合成温度高的缺陷，同时还有效地控制了h-BN晶粒的尺寸和形貌。

In order to synthesize h-BN powder in short time at low temperature,the specimens were pre-pared using sodium borate and magnesium powder as raw materials,using NaCl-MgCl2 (molar ratio of NaCl to MgCl2 is 1 3,1 1 and 3 1,respectively)and KCl-MgCl2(molar ratio of KCl to MgCl2 is 1 1)as the molten salts,heated at 800,1 000 and 1 200 ℃ for 3 h under nitrogen atmosphere by magnesiothermic reduction method.Then the specimens were dipped in the HCl solution (5 mass%),filtrated,washed, dried,ground,and the final powders were obtained.Effects of different molten salts and temperatures on the phase composition and microstructure of the final powders were analyzed using XRD and SEM.The re-sults show that:(1)all the final products synthesized at different temperatures using different molten salts are composed of pure h-BN phase,but with the synthesis temperature rising,the crystallinity of h-BN grad-ually improves:using the NaCl-MgCl2,the final product fired at 1 000 ℃contains flake h-BN,and that fired at 1 200 ℃ contains stromatolite h-BN,however flake h-BN forms at 1 200 ℃ when using the KCl-MgCl2 molten salt.(2)Synthesis of h-BN powders by magnesiothermic reduction in NaCl-MgCl2 molten salt not only overcomes the disadvantage of high synthesis temperature of other methods,but also controls the grain size and morphology of h-BN crystals effectively.