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Synthesis and Characterization of Desified Amorphous Phasee

精细化非晶相的合成与表征

基本信息

批准号：
09640569
负责人：
OHTAKA Osamu
金额：
$ 1.79万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640569/
关键词：
glass high pressure synthesis densified amorphous GeO2 EXAFS melting

项目摘要

According to the present research project, we have pefformed following three studies.1) Glasses of composition GeO_2 and Li_2O-3GeO_2 were compressed up to 30 GPa at temperatures from 27 to 500^oC where sixfold coordination of Ge is stable. Densification of 10 and 15% was achieved for GeO_2 and Li_2O-3GeO_2 glasses, respectively. Ge EXAFS measurements of Li_2O-3GeO_2 glasses retrieved from high pressure indicated that the coordination number of Ge is 4. The second and third neighbor distances (Ge-Gel and Ge-Ge2) determined by EXAFS show that the densification mechanism is explained by more distorted packing of GeO_4 tetrahedra than that in ambient glass. Coordination change by compression in the present Li_2O-3GeO_2 and GeO_2 glasses is reversible. The quenchability of the sixfold coordination of Ge in germanate glass is discussed.2) Using High-Pressure Differential Thermal Analysis (HP-DTA) system with a cubic multi-anvil high pressure apparatus, we measured the melting points of port … More landite, Ca(OH) _<nu> up to 6GPa and 1000ﾟC.We detected endothermic due to meeting peaks at the temperature and pressure conditions of 800ﾟC and 2.5GPa, 769ﾟC and 3.5GPa, 752ﾟC and 4.0GPa, 686ﾟC and 5.0GPa, and 596ﾟC and 6.0GPa. By in-situ x-ray studies under pressure, the melting of portlandite was observed at 730ﾟC and 4.32GPa and at 640ﾟC and 5.81GPa. Results of both HP-DTA and x-ray studies were harmonious within their experimental errors. The melting curve has a negative gradient indicating the higher density of liquid Ca(OH)_2 than that of portlandite in this pressure range.3) EXAFS spectra near the Ge K-edge in diamond and white-tin type Ge under high temperature and pressure were measured using a cubic anvil type high pressure device with synchrotron radiation from thr Photon Factory. Pressure values up to 10.6GPa were estimated on the basis of the isothermal equation of state of the-diamond type Ge within an accuracy of 0.4GPa. Pressures in the sample cell assembly were also determined by X-ray diffraction experiment using the NaCl scale. The diamond type Ge is of great advantage to the pressure calibrant of EXAFS measurements at elevated temperature because a harmonic approximation can be applied up to 700ﾟC. Less

1)在27~500℃温度范围内，将GeO_2和Li_2O-3GeO_2组成的玻璃压缩到30 Gpa，其中Ge的六重配位稳定。GeO_2和Li_2O-3GeO_2玻璃的致密化程度分别为10%和15%。从高压下回收的Li_2O-3GeO_2玻璃的Ge EXAFS测量表明，Ge的配位数为4。EXAFS测定的第二和第三邻间距(Ge-Gel和Ge-Ge_2)表明，致密化机制是由GeO_4四面体的扭曲堆积引起的。在现今的Li_2O-3GeO_2和GeO_2玻璃中，受压缩的配位变化是可逆的。讨论了锗玻璃中Ge的六配位猝灭的可能性。2)利用高压差热分析系统，结合立方多砧座高压装置，测量了…口的熔点在800ﾟC和2.5 Gpa，769ﾟC和3.5 Gpa，752ﾟC和4.0 Gpa，686ﾟC和5.0 Gpa，596ﾟC和6.0 Gpa的温度和压力条件下，我们发现了吸热峰。通过现场加压X射线研究，在730ﾟC和4.32 GPa和640ﾟC和5.81 GPa下观察到了紫柱石的熔融过程。HP-DTA和X射线研究的结果在实验误差范围内是一致的。熔化曲线呈负梯度，表明在该压力范围内，液态Ca(OH)_2的密度高于紫柱石。3)在高温高压下测量了金刚石和白锡型Ge中Ge K边附近的EXAFS谱。根据钻石型Ge的等温状态方程，在0.4 Gpa的精度内估算了高达10.6 Gpa的压力值。样品池组件中的压力也是通过使用氯化钠刻度的X射线衍射实验来确定的。钻石型Ge对于高温EXAFS测量的压力校准是非常有利的，因为谐波近似可以应用到700ﾟC以下。