Variations of nano-structure and physical properties of silicate glasses by static and shock compressions

为了获得下地壳上地幔岩浆和陨石撞击引起的玻璃材料结构变化的信息，开展了以下高压条件下硅酸盐玻璃纳米结构变化的研究. SiO_2玻璃在15 GPa的静高压下压缩，密度增加了28%。结果表明，SiO_4四面体与非桥氧形成3，4元环是导致密度增加的主要原因。对SiO_2-GeO_2玻璃进行了冲击压缩实验。GeO_2组分的增加加速了它们的结构变化.利用X射线衍射、拉曼光谱和分子动力学计算研究了CaSiO_3-MgSiO_3玻璃在静态和冲击压缩下的结构变化。在7.5GPa的静态压缩下，密度增加了约5%。这种密度的增加是由于SiO_4四面体的3、4元环的形成。而冲击压缩后的CaSiO_3-MgSiO_3玻璃的密度几乎没有增加。这一事实可能表明，冲击压缩不会形成SiO_4四面体的3，4元环，而压力释放和随后的温度升高会使压缩结构松弛.研究了蛋白石纳米结构在冲击压缩过程中的结构变化。在20-30 GPa压力范围内，蛋白石的密度增加约10%，压力越高，密度越小。X射线衍射分析表明，冲击使蛋白石的结晶部分转变为非晶态。红外光谱分析表明，蛋白石的OH减少，OH带频率向高波数方向变化.这些研究的结果在IMA等国家和国际会议上发表，并作为科学论文发表。

In order to obtain information for magma at lower crust and upper mantle regions and structural changes of glass materials by meteorite impacts, the following studies for the nano-structure change of silicate glass under high pressure condition were carried out.1. SiO_2 glass was compressed under static high pressure up 15 GPa, about 28% of density increase was observed. It was concluded that formations of 3,4 membered rings of SiO_4 tetrahedrons with non bridging oxygen are responsible for the density increase. SiO_2-GeO_2 glasses were also compressed by shock experiments. Increase of GeO_2 component accelerates their structure change.2. The structures changes of CaSiO_3-MgSiO_3 glasses compressed by static and shock compression were investigated by X-ray diffraction measurements, Raman spectroscopy and Molecular dynamics calculations. About 5% of density increase by static compression of 7.5 GPa was observed. Ii is suggested that this density increase caused by the formations of 3,4 membered rings of SiO_4 tetrahedrons. On the other hand, Almost no density increases were observed for shock compressed CaSiO_3-MgSiO_3 glasses. This fact may indicate that 3,4 membered rings of SiO_4 tetrahedrons may not be formed by shock compression and compressed structure was relaxed by pressure release and subsequent temperature increase.3. Structural change of opal nano-structure by shock compression was investigated. About 10% of density increase of opal at 20-30 GPa and density decrease at higher pressure. By X-ray diffraction measurements, the crystalline part of opal was change to amorphous state by shock. By IR spectroscopy, OH of opal decrease and frequency of OH band changed toward higher wavenumver were investigated.4. The results of these studies were presented at National and International Meetings such as IMA and also published as scientific papers.