Room temperature solid surface water with tetrahedral jumps of 2H nuclei detected in 2H2O-hydrated porous silicates
Room temperature solid surface water with tetrahedral jumps of 2H nuclei detected in 2H2O-hydrated porous silicates
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DOI：
10.1021/jp048047k
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发表时间：
2004-11-18
影响因子：
3.3
通讯作者：
Phair, JW
中科院分区：
文献类型：
--
作者：
Benesi, AJ;Grutzeck, MW;Phair, JW
本文用H-2NMR技术和量热法研究了钾镁石、再水化沸石A、再水化多孔玻璃、再水化高比表面积硅溶胶和硅酸三钙水化产物中固体硅酸盐表面附近水的性质。所有样品的室温H-2 NMR四极子回波光谱显示对应于（H2O）-H-2的尖锐中心共振。的kanemite，多孔玻璃，和硅胶光谱显示，此外，粉末图案被分配，根据先前的研究结果kanemite，硅烷醇-OH基团经历快速的3倍跳跃或旋转扩散的Si-O键。水合硅酸三钙的光谱除水峰外，还显示了一种刚性粉末图案，归属于Ca（（OH）-H-2）（2）。在-120 ℃和-150 ℃下获得的卡涅姆石样品的光谱表明，含水氘核的qcc值在180至210 kHz的范围内，这与在卡涅姆石的X射线结构中观察到的不同水环境所预期的一样。在两个磁场下获得的钾镁矾室温H-2 T-1数据与理论计算完全匹配，理论计算假设固态晶格中H-2核的快速四面体跳跃（2.0 x 10（8）s（-1））与冰点以下（H2O）-H-2冰中观察到的相似。T-1数据不能与各向同性旋转扩散相匹配，这是对液态水的预期。在沸石A中低负载（H2O）-H-2的T-1数据也与四面体跳跃模型相匹配。其他样品的T-1数据与经历快速四面体跳跃的固态表面水和更靠近表面的液态水之间的H-2核或（H2O）-H-2分子的快速交换一致。在所有样品的水合过程中观察到的放热与地表水的液相向固相转变的预期熔化热一致。
The nature of water adjacent to solid silicate surfaces in kanemite, rehydrated zeolite A, rehydrated highly porous glass, rehydrated high surface area silica get, and the hydration products of tricalcium silicate has been investigated with H-2 NMR techniques and calorimetry. The room temperature H-2 NMR quadrupole echo spectra of all samples show a sharp central resonance that corresponds to (H2O)-H-2. The kanemite, porous glass, and silica gel spectra show in addition powder patterns that were assigned, based on previous findings for kanemite, to silanol -OH groups experiencing rapid 3-fold jumps or rotational diffusion about the Si-O bond. The spectrum of hydrated tricalcium silicate shows in addition to the aqueous peak a rigid powder pattern that is assigned to Ca((OH)-H-2)(2). Spectra obtained at - 120 and - 150 degreesC for the kanemite sample show that the qcc values for the aqueous deuterons range from 180 to 210 kHz, as would be expected for the different water environments observed in the X-ray structure of kanemite. Room temperature H-2 T-1 data obtained at two magnetic fields for kanemite are exactly matched with theoretical calculations that assume rapid tetrahedral jumps of the H-2 nuclei (2.0 x 10(8) s(-1)) in a solid-state lattice similar to those observed in (H2O)-H-2 ice below the freezing point. The T-1 data cannot be matched with isotropic rotational diffusion as would be expected for liquid water. The T-1 data for low loadings of (H2O)-H-2 in zeolite A are also matched with the tetrahedral jump model. T-1 data for the other samples are consistent with rapid exchange of H-2 nuclei or (H2O)-H-2 molecules between solid-state surface water experiencing rapid tetrahedral jumps and liquid-state water farther front the surface. Heat evolution observed during hydration of all samples is consistent with the heat of fusion expected for a liquid to solid phase transition for the surface water.