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Pseudo Phase Transition of Molecular Assembly in a Structure- Controlled Subnanospace Having Enhanced Potential.

结构控制的亚纳米空间中分子组装的伪相变具有增强的潜力。

基本信息

批准号：
04453004
负责人：
KANEKO Katsumi
金额：
$ 4.1万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Molecular states of SO_2, NO, N_2, CH_4, and H_2O in carbon subnanospaces of slit shape were studied by heat of adsorption, in situ X-ray diffraction, high pressure adsorption, and ordinary molecular adsorption. Supercritical NO gas was changed into quasi-vapor through formation of (NO)_2 due to strong molecular field of the subnanospace with the aid of magnetic perturbation. Also supercritical CH_4 and N_2 was transformed to their quasi-vapor due to the subnanospace field and application of high pressure of adsorptives. The structural change of H_2O molecular assembly in the subnanospace was examined by high resolution X-ray diffraction anaysis, indicating presence of a distorted two-dimensional ice like structure.New phase transition of molecular assembly in the carbon nanospace was shown in the system of SO_2 and carbon slit pore of 0.8 nm width. The heat of SO_2 adsorption in the carbon subnanospace was divided into the constant region of enhanced potential field below phi=0.6 and an steep increase region above phi=0.6. The constant region was ascribed to enhanced SO_2-slit pore interactions (about 10 KJ/mol) including the induced dipole-permanent dipole interaction ; this indicated the parallel arrangement of dipoles of adsorbed SO_2 molecules. The steep increase was caused by the inter SO_2 molecular interaction which gives rise to conversion of the dipoles, forming the anti-parallel arrangement. The molecular potential calculation using the Lennard-Jones potential, the image potential approximation, and the Stockmayr potential supported this model. This orientation structure of the SO_2 dipoles in the carbon subnanospace depended on the micropore width ; in the greater carbon nanospace the above-mentioned steep transition was not observed. This research showed a new possibility of molecular chemistry controlled by the subnanospace field.

用吸附热法、原位X射线衍射法、高压吸附和普通分子吸附等方法研究了SO2、NO、N2、CH4和H2O在狭缝状碳亚纳米空间中的分子状态。在磁微扰作用下，由于亚纳米空间的强分子场，超临界NO气体通过生成(NO)_2转变为准蒸汽。超临界甲烷和超临界氮气由于亚纳米空间场和高压吸附作用而转化为准蒸气。用高分辨X射线衍射仪研究了亚纳米空间中H2O分子组装的结构变化，表明存在扭曲的二维冰状结构；在SO2和0.8 nm宽的碳缝孔体系中，碳纳米空间中分子组装发生了新的相变。碳亚纳米空间中SO2的吸附热被划分为Phi=0.6以下的增强势场恒定区和Phi=0.6以上的陡增区。这一恒定区的形成归因于SO2与缝隙孔相互作用的增强(约10kJ/mol)，包括诱导的偶极-永久偶极相互作用，这表明吸附的SO2分子的偶极平行排列。这种急剧增加是由于SO2分子间的相互作用引起偶极转换，形成反平行排列。使用Lennard-Jones势、映像势近似和斯托克迈尔势计算的分子势支持这一模型。SO2偶极子在碳亚纳米空间中的这种取向结构依赖于微孔宽度；在更大的碳纳米空间中，没有观察到上述陡峭的转变。这项研究为亚纳米空间场控制分子化学提供了新的可能性。