网络法制备氮化硼（BN）粉体的研究

发布时间：2018-05-25 07:06

  本文选题：BN材料 + 高分子网络法　； 参考：《沈阳大学》2011年硕士论文

【摘要】：BN材料具有机械性能好、导热性能高、化学性质稳定、抗氧化能力强等一系列优异性能,在储氢材料、催化剂载体等领域有着潜在的应用价值。但到目前为止,BN在这些领域中并没有得到广泛应用,主要原因是至今还没有一种合适的方法合成出高产率、高纯度、高比表面的BN材料。目前合成BN的方法有电弧放电法、化学气相沉积法、球磨退火法、前驱体高温热解法和C模板法等。在这些方法中,电弧放电法、化学气相沉积法操作复杂、成本高且产率低。前驱体高温热解法和C模板法常用于高比表面的BN合成,但前驱体高温热解法涉及的有效前驱体难于合成,同样产量低下,而C模板法则由于反应后的残余C杂质难于去除导致所得BN粉体纯度不高,且操作繁杂。因此,寻找一种简便经济的方法来合成出高产率、高纯度、高比表面的BN粉体将是非常重要的工作。 本文以廉价的硼砂和尿素为主要原料,采用网络法制备BN前驱体并通过反应合成出高纯度、高比表面的BN粉体。并对高分子网络形成机理,前驱体成分配比和网络溶胶凝胶进行了研究。探讨了碳源的选择对于网络凝胶的影响,研究了反应温度对BN粉体比表面、孔隙度、形貌的影响。还研究了BN粉体的合成工艺、反应机理和微观形貌。使用XRD、SEM、EDS、TEM和低温N2吸附-脱附等检测手段对BN粉体进行表征,优化反应条件。取得以下研究结果： 基于网络法合成出硼元素和氮元素分布均匀的高分子网络干凝胶。得出网络剂最佳成分配比为：丙烯酰胺：N,N-亚甲基双丙烯酰胺：过硫酸铵=140：4：25。利用网络法对于粉体分散性的提高促进,得到分散性良好的BN前驱体,通过调节反应时间,反应温度,成功的合成出颗粒粒度低、分散性好的高比表面BN粉体。明确网络法制备BN粉体的最佳合成工艺为：在NH3气氛中,300℃保温2小时,675℃保温2小时反应,产品经过清洗除碳处理,最终可得到BN粉体。合成BN粉体平均孔径在5.16nm左右,比表面为288.57m2/g,比现有资料报道的比表面有明显提高。本合成方法简单,易操作,合成温度低,且产率高。
[Abstract]:BN has a series of excellent properties such as good mechanical properties, high thermal conductivity, stable chemical properties, strong oxidation resistance and so on. It has potential application value in hydrogen storage materials, catalyst support and other fields. But so far it has not been widely used in these fields. The main reason is that there is no suitable method to synthesize BN materials with high yield, high purity and high surface area. At present, the methods of BN synthesis include arc discharge, chemical vapor deposition, ball milling annealing, pyrolysis of precursor at high temperature and C template. Among these methods, arc discharge method and chemical vapor deposition method are complex, high cost and low yield. The precursor pyrolysis and C template method are often used in the synthesis of BN with high specific surface, but the effective precursor involved in the high-temperature pyrolysis of the precursor is difficult to synthesize, and the yield is also low. However, the C template rule is difficult to remove the residual C impurities after the reaction, which leads to the low purity and complicated operation of the BN powder. Therefore, it is very important to find a simple and economical method to synthesize BN powder with high yield, high purity and high specific surface. In this paper, borax and urea were used as the main raw materials, BN precursor was prepared by network method and BN powder with high purity and high specific surface was synthesized by reaction. The formation mechanism of polymer network, precursor composition ratio and network sol gel were studied. The influence of carbon source selection on the network gel and the effect of reaction temperature on the specific surface porosity and morphology of BN powder were studied. The synthesis process, reaction mechanism and microstructure of BN powder were also studied. The BN powder was characterized by TEM and N2 adsorption-desorption at low temperature, and the reaction conditions were optimized. The following findings were obtained: Polymer network xerogels with uniform distribution of boron and nitrogen elements were synthesized by network method. The optimum composition of the network agent is as follows: acrylamide: N- N- methylene bisacrylamide: ammonium persulfate 140: 4: 25. The BN precursor with good dispersity was obtained by using the network method to improve the dispersity of the powder. By adjusting the reaction time and reaction temperature, the low particle size and high specific surface BN powder with good dispersibility were successfully synthesized. It is determined that the optimum synthesis process of BN powder by network method is that the BN powder can be obtained by cleaning and decarbonization in the atmosphere of NH3 at 300 鈩，

本文编号：1932544