摘要
本文以镁热自蔓延过程中的反应动力学因素作为基础,探究了不同镁粉粒径及制样压力对自蔓延过程的影响,考察了不同镁粉粒径及制样压力对产物碳化硼的物相组成、微观形貌及晶体结构发育的影响规律.结果表明:自蔓延过程会显著受到动力学因素的影响,当镁粉粒径大于96μm时,反应物接触面过小,反应无法启动并维持.随着镁粉粒径的减小,氧化硼的还原反应加快,硼酸镁的形成被有效抑制,浸出产物中的镁残留量从0.38％降至0.29％;但过快的还原反应使得体系温度迅速升高,致使部分硼镁挥发,浸出产物的的C/B质量比从0.52升至0.65;制样压力的增大能够限制晶体生长空间,从而削弱硼酸镁的晶须化过程,浸出产物中的镁残留量从0.18％降至0.08％;当制样压力从0增至30 MPa时,能够缩短原料颗粒间的间距,在一定程度上促进还原反应的进行,但同时也促进了硼镁的蒸发耗散,而压力的进一步增加则能够在空间上限制硼镁的挥发,提高原料利用率.浸出产物的C/B质量比在30 MPa时达到峰值0.74,并随着压力的进一步升高而下降至0.66.
Abstract
The adiabatic temperature is an accepted thermodynamic criterion for the occurrence of the magnesiothermic self-propagation synthesis (SHS) reaction, but the actual experimental situation is often more complicated. In this paper, the influence of kinetic factors was investigated in the SHS process by varying the experimental conditions of Mg powder particle size and sample pressure. The results show that even if the experimental raw materials were the same, the different physical states of the raw materials could lead to completely different reaction endpoints. It was found that the reaction could not be initiated when the particle size of Mg powder was larger than 96 μm. The finer magnesium powder and higher sample pressure would accelerate the reaction and reduce by-products, but also increase the evaporation and dissipation of the raw material. The results show that the size of magnesium powder near 58 μm and the sample pressure of 30 MPa were suitable experimental conditions.
基金项目
Fundamental Research Funds for Central Universities,China(N2225012)
Fundamental Research Funds for Central Universities,China(N2224001-9)
National Natural Science Foundation of China(U1908225)
National Natural Science Foundation of China(52174333)
Key R&D Project of Liaoning Province,China(2020JH2/10700004)
NETL
NSTL
维普
万方数据