Combustion synthesis of boron nitride via magnesium reduction using additives
Combustion synthesis of boron nitride via magnesium reduction using additives
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DOI：
10.1016/j.ceramint.2014.09.080
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发表时间：
2015-01-01
影响因子：
5.2
通讯作者：
Hsu, Yu-Hsiang
中科院分区：
文献类型：
--
作者：
Chung, Shyan-Lung;Hsu, Yu-Hsiang
本研究的目的是提高在燃烧合成h-BN的产品收率使用Mg还原B2O3作为硼源在低的N2-压力下，通过添加剂。将反应物粉末和添加剂放置在穿孔的铝容器中而不压制。由于粉末堆的松散和高度多孔的结构，周围的N-2可以容易地渗透到其中，并且由NaN3或C3H6N6产生的N-2容易逃逸，添加这两种添加剂仅略微增加低含量区域中的产物产率，但是由于降低温度而降低高含量区域中的产物产率。加入惰性颗粒（即，MgO或BN）仅当温度高于硼的熔点时才增加产物产率，在该温度下，熔融硼的聚结由于熔融硼在颗粒上的毛细扩散而受到抑制。当温度低于硼的熔点时，由于惰性颗粒的冷却作用，惰性颗粒的加入降低了产物产率。发现NH4X（X = Cl或Br）在提高产物产率方面最有效，因为它通过首先将硼转化为BXx，然后在H-2的还原下与N-2反应，为硼的氮化创造了更容易的途径。当NH_4Cl和BN同时加入时，在1.6MPa的N_2压力下，产物收率可达67%。(C)2014 Elsevier Ltd和Techna Group S.r.l. All rights reserved.
This study is aimed at enhancing the product yield in combustion synthesis of h-BN using Mg reduction of B2O3 as the boron source under a low N-2 pressure by using additives. The reactant powders and the additives were placed in perforated aluminum containers without pressing. Due to a loose and highly porous structure of the powder stack, the surrounding N-2 can penetrate easily into it and the N-2 generated by NaN3 or C3H6N6 escapes easily, addition of these two additives only increases slightly the product yield in the low content region but decreases the product yield in the high content region due to decreasing temperature. Addition of inert particles (i.e., MgO or BN) increases the product yield only when the temperature is higher than the melting point of boron, under which coalescence of molten boron is suppressed due to capillary spreading of the molten boron on the particles. When the temperature is lower than the melting Point of boron, addition of the inert particles decreases the product yield because of their cooling effect. NH4X (X= Cl or Br) was found the most effective in enhancing the product yield because it creates an easier route for the nitridation of boron by first converting boron to BXx, which then reacts with N-2 under the reduction of H-2. A product yield of 67% was achieved by simultaneous addition of NH4Cl and BN under a N-2 pres ure of 1.6 MPa. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.