Oxidation characteristics of boron particles

作     者：YU Dan KONG ChengDong ZHUO JianKun LI ShuiQing YAO Qiang 

作者机构：Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Thermal EngineeringTsinghua University 

出 版 物：《Science China(Technological Sciences)》 (中国科学（技术科学英文版）)

年 卷 期：2015年第58卷第12期

页      面：2016-2024页

核心收录：

学科分类：081702[工学-化学工艺] 08[工学] 0817[工学-化学工程与技术] 

基　　金：supported by the National Natural Science Foundation of China(Grant No.51206089) Postdoctoral Science Foundation of China(Grant No.2012M510438) the National Basic Research Program of China("973"Project)(Grant No.2013CB228502) 

主　　题：boron particles oxidation activation energy saturation effect 

摘      要：The oxidation characteristics of boron particles, boron-A with the diameter of 2.545 μm and boron-B with the diameter of 10.638 μm, at low temperature（1500 K） have been investigated by thermogravimetry（TG） coupled with simultaneous differential scanning calorimetry（DSC）, infrared and mass spectra. A rapid oxidation stage of boron particles, followed by a slow oxidation stage of sintered particles, is found from the TG and DSC curves. The onset temperatures of the oxidation process of boron-A particles are in the range of 806–889 K, which are at least 105 K lower than those of boron-B at the same condition. As the partial pressure of oxygen increases from 5% to 35%, the onset temperature of boron-A or boron-B particles decreases. However, when the partial pressure of oxygen is above 35%, the onset temperature becomes constant, implying a saturation effect of oxygen on the reaction rate. It indicates that the chemical adsorption of oxygen, i.e. chemical reaction, on the particle surface is the rate-limited step at the beginning of the rapid oxidation stage. Therefore, the first-order chemical reaction model is used to simulate the oxidation of boron particles, even that of the sinter. The average activation energies of the particles are 291.3 kJ/mol for boron-A and 338.4 k J/mol for boron-B. While the average activation energies of the sintered particles are 36.35 k J/mol for boron-A and 31.87 kJ/mol for boron-B. The pre-exponential factor of the particles is -10^4, while that of the sinter is 10^-1. The oxidation rate constant of boron is qualitatively mainly affected by the specific surface of the sample and the thickness of the oxide layer.