高温高压下钠长石熔体结构及水的溶解机理实验研究

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	高温高压下钠长石熔体结构及水的溶解机理实验研究
	孙樯
	2000
学位授予单位	中国科学院地球化学研究所
学位授予地点	中国科学院地球化学研究所
学位名称	博士
学位专业	地球化学
关键词	高温高压钠长石熔体结构溶解机制
摘要	通过对高温高压下钠长石熔体结构及水在钠长石熔体中溶解机制的Raman和FTIR光谱实验研究，可以得出以下结论：（1）随着压力升高（1bar-2.0GPa）NaAlSi_3O_8熔体玻璃Raman光谱的低频区（50-650cm~(-1)）不断变窄并向高频方向移动，同时高频区（850-1300cm~(-1)）不断变窄且向低频区方向移动，这表明随着压力升高T-O-T为（T = Si, Al）键角（0）不断减小，并且分布范围变窄，T－O－T键角这种变化从而可使T－O键的力常数减小，导致键强减弱，另外，580cm~(-1)谱峰强度随着压力升高不断减弱，并在0.8-1.0GPa时最为显著，这是由于在0.8-1.0GPa时包含（Si, Al）的平面三元环结构的“垮塌“造成的。此外，钠长石熔体结构随压力升高的这种变化特征与对其粘度的研究是相符的；（2）水在钠长石熔体中同时以OH和H_2O形式存在，这分别对应于FTIR光谱中的4500cm~(-1)及5200cm~(-1)谱峰。根据对水在钠长石熔体中溶解类型的红外光谱研究以及热力学计算都表明，在溶解初期水主要以OH存在于熔体中，此时H_2O含量相对较低；随着熔体中水含量的升高，OH所占比例越来越低，而H_2O分子则成为主要的溶解类型；（3）根据对含水钠长石玻璃的Raman和FTIR光谱研究，并结合Kohn等的MAS NMR结果，认为H_2O在NaAlSi_3O_8熔体中的溶解作用同时存在两种机制：一方面H_2O与Al-O°-Al 结构单元反应发生解聚作用而生成Q~3 Al-OH，并造成Raman光谱中900cm~(-1)谱峰的出现；另一方面水中的H~+与钠长石熔体中的Na~+发生转换作用成为电荷平衡离子。水在钠长石熔体中的溶解作用可表示为：H_2O + 3NaAlSi_3O_8 = 2NaAl(OH)Si_3O_(7.5) + HAlSi_3O_8 + NaOH 考虑到水在熔体中的溶解类型与水含量的关系以及熔体粘度的变化，在溶解初期水的溶解机制以生成Al-OH为主，随着水含量的升高，H~+与Na~+之间的置换作用变得愈加重要。
其他摘要	On the basis of Raman and FTIR spectra research on melt structure and water solubility mechanism in albite glasses, we can make the following conclusions: (1) Higher pressure (1bar-2.0GPa) can lead to below frequency region (50-650cm~(-1)) shift to higher frequency and become narrower, and result in high frequency region (850-1300cm~(-1)) move to lower wave number and become narrower at the same time. These are consistent with the decrease of average T-O-T (T=Si, Al) angle and distribution scope of bond angles (0). In addition, the intensity of 580cm~(-1) band decrease with increase of pressure and the changes are obvious while pressure is in the range of 0.8-1.0GPa. And these result from the "collapse" of the planar three-membered (T=Si, Al) -containing rings within the glass structure. And the changes of melt structure of NaAlSi_3O_8 melt are in accordance with the dependence of viscosity of albite melt on pressure; (2) Water dissolves into NaAlSi_3O_8 melt as OH and H_2O simultaneously, and these are in agreement with the 4500cm~(-1) and 5200cm~(-1) bands in FTIR spectra. On the basis of FTIR spectra calculation and thermodynamic study, those all show that OH is dominant and H_2O is relatively secondary in the initial dissolution stage, and higher water contents can enhance the proportion of H_2O and lower the relative content of OH; (3) On the basis of Raman, FTIR spectra and MAS NMR (Kohn et al, 1989, 1998), we conclude that the dissolution of H_2O in NaAlSi_3O_8 melts occurs by two solubility mechanisms simultaneously: I H_2O interacts with Al-O-Al groups to produce Al_OH and causes the appearance of 900cm~(-1) band in Raman and FTIR spectra: II H~+ exchanges for Na~+ to be charge-balancing cation at the same time. And the dissolution of water in NaAlSi_3O_8 melt can be expressed: H_2O + 3NaAlSi_3O_8 = 2NaAl(OH)Si_3O_(7.5) + HAlSi_3O_8 + NaOH On the base of the dependency of water speciation and melt viscosity on water content, we think that the mechanism I is dominant in the initial dissolution and with the increase of water content, the II becomes important solubility mechanism. However, the dissolution of H_2O in NaAlSi_3O_8 melts does not change abruptly at 30mol% H_2O.
页数	46
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3538
专题	研究生_研究生_学位论文
推荐引用方式 GB/T 7714	孙樯. 高温高压下钠长石熔体结构及水的溶解机理实验研究[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,2000.

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