橄榄石成核动力学方程的修正及其对动力学数据的约束

摘要

本文从成核动力学理论出发,考虑新相晶核的表面能对其形状的影响,修正了晶面成核情形的成核动力学方程.新的成核率方程还原了传统成核率方程中通常简化为常数的指前系数.结合修正的相变体积分数计算公式,新的成核率方程可以确定出成核过程中的两个物理参量:新相晶粒与反应相晶粒的接触角度及新相物质与反应相物质之间的表面能.分析结果表明,Ni2 SiO4的接触角度和表面能分别为0.57°,32.33 J·m-2,而Mg2 SiO4和( Mg,Fe)2SiO4的数据质量不足以确定表面能与形状因子.结合对加温加载路径在高温高压试验中影响的研究,我们认为亟需补充高质量的成核率数据来确定橄榄石的成核率参数.%The traditional incoherent grain boundary nucleation rate equation is modified to incorporate the effect of interfacial energy on the shape of product nuclei. The modified equation recovers the pre-exponential factor to its original form, which is currently set as constant and determined by fitting to experimental data. Combined with the modified volume fraction calculation equation, the modified nucleation equation can refine two nucleation quantities, i. e. , contact angle and interfacial energy between the reactant nuclei and product nuclei. Meanwhile the refinement can be employed to constrain the quality of experimental data. Further analyses of Ni2SiO4, Mg2SiO4 ,(Mg, Fe)2 SiO4 kinetic data show that the contact angle and interfacial energy of Ni2SiO4 are respectively 0. 57°, 32. 33 J ? m~2, while the data quality of Mg2SiO4 and (Mg, Fe)2SiO4 is not good enough to extract such information. Both present study and the study on the effects of nucleation in heating and loading path suggest that the high quality experiments are needed to derive the correct nucleation parameters of mantle olivine.