Study on network structure of hydrogen bonding for supercritical and subcritical aqueous solutions.

小角x射线散射（SAXS）的实验数据为我们提供了亚临界和超临界水溶液结构波动的大部分信息。扩展x射线吸收精细结构（EXAFS）实验适用于获得微观尺度的结构信息。我们开发了一种适用于SAXS和EXAFS实验的样品架。我们对超临界溶液的浓度波动进行了实验，得到了溶液混合方案的信息。在这个项目中，我们研究了以下三个系统。(1)亚临界ch_3oh - h_2o与环境条件的比较结果表明，随着温度和压力的升高，密度波动显著增大，而浓度波动不变。也就是说，在混合物的环境状态和亚临界状态下，氢键网络是相似的。2)超临界Xe-Kr3)超临界co_2 - chf_33在研究2)和3)中，我们发展了获得超临界溶液的偏摩尔体积和等温压缩率的方法。利用这些数据和SAXS数据，我们可以得到溶液的浓度波动。我们还开发了一种近红外吸收光谱仪，它适合于阐明氢键的形式。我们已将该仪器应用于一些环境水溶液和亚临界水。

Experimental data by small-angle X-ray scattering (SAXS) give us the most information on the structural fluctuation of sub-critical and supercritical aqueous solutions. Extended X-ray absorption fine structure (EXAFS) experiments are suitable to obtain the information of structure in microscopic scale. We developed a sample holder applicable to both SAXS and EXAFS experiments.We have started the experiments to elucidate the concentration fluctuations of supercritical solutions, which give us information on mixing scheme of the solutions. In this project, we studied the following three systems.1) Sub-critical CH_3OH-H_2OComparing the results with those of ambient conditions, it has been shown that the density fluctuation increases significantly with the rise in temperature and pressure, whereas concentration fluctuation remains unchanged. Namely, it is concluded that the hydrogen bonding networks are similar in ambient and sub-critical state of the mixture.2) Supercritical Xe-Kr3) Supercritical CO_2-CHF_3In studies 2) and 3), we developed the methodology to obtain partial molar volumes and isothermal compressibility of supercritical solutions. Using these data in addition to the SAXS data, we can obtain the concentration fluctuation of the solutions.We have also developed a spectrometer for near infra-red absorption, which is suitable to elucidate the forms of hydrogen bonding. We have applied this apparatuse to some ambient aqueous solutions and sub-critical water.