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

为了获得下地壳和上地幔区域岩浆和陨石撞击玻璃材料结构变化的信息，对高压条件下硅酸盐玻璃的纳米结构变化进行了如下研究1。SiO_2玻璃在15gpa的静态高压下压缩，密度提高28%左右。结果表明，非桥氧SiO_4四面体的3,4元环的形成是导致密度增加的原因。SiO_2-GeO_2玻璃也进行了冲击压缩实验。GeO_2组分的增加加速了其结构的变化。通过x射线衍射测量、拉曼光谱和分子动力学计算，研究了静态压缩和激波压缩后CaSiO_3-MgSiO_3玻璃的结构变化。静压7.5 GPa可使密度提高5%左右。认为这种密度的增加是由SiO_4四面体形成3,4元环引起的。另一方面，冲击压缩CaSiO_3-MgSiO_3玻璃的密度几乎没有增加。这说明SiO_4四面体的3,4元环可能不是通过激波压缩形成的，压缩结构是通过释放压力和随后的温度升高而松弛的。研究了冲击压缩对蛋白石纳米结构的影响。在20 ~ 30 GPa温度下，蛋白石的密度增加约10%，而在更高的压力下密度降低。通过x射线衍射测量，发现蛋白石的结晶部分在激波作用下变为非晶态。通过红外光谱研究了蛋白石的OH降低和OH波段频率向高波方向变化。这些研究的结果在诸如IMA之类的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.