摘要:
Al粒子作为铝热剂中的主要金属还原剂,通常会自发氧化而在表面形成Al2O3钝化层.Al和O原子的扩散渗透将使Al2O3壳层的结构和热力学性质发生变化进而对铝热剂的点火过程产生影响.采用基于密度泛函理论的第一性原理方法,结合准简谐德拜模型和晶格动力学理论,计算并比较了α-Al2O3,Al原子掺杂α-Al2O3以及O原子掺杂α-Al2O3在高温高压下的相关热力学性质,讨论了Al和O原子掺杂对其热力学性质的影响.结果表明:在研究的温度和压力范围内,Al和O间隙原子的掺杂将使α-Al2O3的体模量减小,热容和热膨胀系数增大.这一结果意味着对于外表面包覆Al2O3的纳米Al粒子而言,高温高压下Al和O原子在Al2O3壳层中的扩散将使得Al2O3更具延展性而不利于发生剧烈散裂.
Abstract:
Al particles are widely used as a metal reductant in the thermite,and a native Al2O3 film always forms on the particle surface as a passivating oxide shell.The diffusions of Al and O atom through the oxide shell will influence the structure and thermodynamic properties of Al2O3,and thus the ignition process of the thermite.In this work,the thermodynamics properties of α-Al2O3,α-Al2O3 doped by Al iuterstitial atom and α-Al2O3 doped by O interstitial atom under high pressure and temperature are comparatively investigated by the first-principles calculations based on density-functional theory and quasi-harhmonic Debye model.The effects of the doping of Al and O interstitial atoms on the thermodynamic properties of α-Al2O3 are discussed.The results indicate that the doping of the Al and O interstitial atoms will reduce the bulk modulus,and increase the volume thermal expansion coefficient and constant volume heat capacity of α-Al2O3.Therefore,the diffusions of Al and O atom will make the oxide shell more ductile,and adverse to the spallation during the ignition of Al particles.
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