Experimental study on kinetics of the olivine-spinel phase transition.

橄榄石-尖晶石相变动力学的实验研究。

• 批准号: 08640605
• 负责人: SHIMOBAYASHI Norimasa
• 金额: $ 0.45万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640605/
• 关键词: olivine-spinel transition; hydrothermal experiments; kinetics; Mg_2GeO_4; 水熱法; カイネティックス実験

In the present study, we aimed to propose the preliminary kinetics data for the olivine*spinel transition by using the Mg_2GeO_4 analogue, Isothermal experiments had already been carried out as a function of H_2O content at 0.07GPa to examine the effect of the amount of H_2O on the Mg_2GeO_4 olivine-spinel transition. In the present study, the additional kinetic experiments were also tried to carry out at the higher pressure(0.15GPa)by using a newly-introduced high-pressure type reactor, but the most of these runs met with failure simply because of the machine trouble (mainly a pressure leak). In a series of these experiments, small amounts of Mg(OH)_2 was enclosed to control the content of H_2O (X) by varying its amount, and was heated hydrothermally as a function of time. By fitting the experimental data at each set of temperatures and X's to the Avrami equation, a specific time (ts) was derived at which the olivine-spinel phase transition is first detectable. The ts had been obtained at each set of temperatures and X's at 0.07GPa. However, since only a few runs were successfully performed in each set of temperatures and X's at 0.15GPa, the specific times could not be determined. Consequently, the effect of the pressure (between at 0.07GPa and 0.15GPa) on the kinetics of the Mg_2GeO_4 olivine*spinel transition could not be systematically discussed. However, it may safely be said that the effect of the pressure seems to be considerably smaller than the effect of the amount of H_2O on the transition by considering the fact that even a small amount of H_2O drastically activates the nucleation rate in the Mg_2GeO_4 olivine*spinel transition.

本文利用Mg_2GeO_4类似物，对Mg_2GeO_4的橄榄石-尖晶石转变进行了初步的动力学研究，并在0.07GPa下进行了等温实验，考察了H_2O含量对Mg_2GeO_4橄榄石-尖晶石转变的影响。在本研究中，还尝试使用新引入的高压型反应器在较高压力（0.15GPa）下进行额外的动力学实验，但大多数这些实验仅仅因为机器故障（主要是压力泄漏）而失败。在一系列的实验中，少量的Mg（OH）_2被封闭以通过改变其量来控制H_2O（X）的含量，并且作为时间的函数被水热加热。通过将每组温度和X的实验数据拟合到Avrami方程，导出了橄榄石-尖晶石相变首次可检测的特定时间（ts）。在每一组温度和0.07GPa的X下获得了ts。然而，由于在0.15GPa的每组温度和X下仅成功进行了几次运行，因此无法确定具体时间。因此，压力（在0.07GPa和0.15GPa之间）对Mg_2GeO_4橄榄石 * 尖晶石转变动力学的影响不能被系统地讨论。然而，考虑到即使少量的H_2O也能显著地激活Mg_2GeO_4橄榄石→尖晶石转变的成核速率，可以有把握地说，压力对转变的影响似乎比H_2O量的影响小得多。