IN-SITU SOLID-STATE NMR-STUDIES OF CA3SIO5 - HYDRATION AT ROOM-TEMPERATURE AND AT ELEVATED-TEMPERATURES USING SI-29 ENRICHMENT
IN-SITU SOLID-STATE NMR-STUDIES OF CA3SIO5 - HYDRATION AT ROOM-TEMPERATURE AND AT ELEVATED-TEMPERATURES USING SI-29 ENRICHMENT
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DOI：
10.1007/bf00355951
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发表时间：
1994-08-01
影响因子：
4.5
通讯作者：
GROVES, GW
中科院分区：
文献类型：
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作者：
BROUGH, AR;DOBSON, CM;GROVES, GW
Si-29同位素富集用于在NMR探针中原位从水合Ca 3SiO 5（C3 S）的单个样品中获取多个Si-29魔角旋转（MAS）和交叉极化魔角旋转（CPMAS）核磁共振（NMR）谱。在20、50和75 ℃下获得了具有优异信噪比的数据，所用的光谱仪时间最少，并且不需要多个样品的淬灭。光谱线宽和聚合物链的长度来自光谱没有检测到的差异，从实验中，其中进行的淬火与丙-2-醇。此外，MAS技术对水化反应的影响似乎是最小的。在20 ℃时，最初产生的大量水合物是二聚的;在反应的后期，发生聚合。计算了这两个反应的Arrhenius能量分别为35和100 kJ mol-1。在整个水合过程中获得的交叉极化（CP）光谱表明，在20 ℃下，2%的水合单体Q（O）（H）物种从诱导期之后持续到水合反应的后期阶段;这表明该物种不太可能由C3 S的表面羟基化产生;随着水合作用的增加，这种物质发生了高场位移，这表明硅酸盐物质的环境可能发生了变化。发现产生的Q（O）（H）的量在较高温度下增加。聚合的潜在机制进行了评估，并发现一个模型，其中二聚硅酸盐单元连接在一起的插入单体（二聚体-->五聚体-->八聚体），以给出最佳的拟合观察到的数据，这些结果支持dreierketten模型的水合物的结构。
Si-29 isotopic enrichment was used for acquisition of multiple Si-29 magic-angle spinning (MAS) and cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra, in situ in an NMR probe, from a single sample of hydrating Ca3SiO5 (C3S). Data with excellent signal-to-noise ratios were obtained at 20, 50 and 75-degrees-C, with minimal use of spectrometer time, and without the need for the quenching of multiple samples. Spectral line widths and polymer-chain lengths derived from the spectra had no detectable differences from experiments in which the quenching was carried out with propan-2-ol. Furthermore, the effects of the MAS technique on the hydration reaction appeared to be minimal. At 20-degrees-C, the bulk hydrate initially produced was dimeric; at later stages of the reaction, polymerization occurred. Arrhenius energies of 35 and 100 kJ mol-1, respectively, were calculated for these two reactions. The cross-polarization (CP) spectra acquired throughout the hydration showed that at 20-degrees-C, 2% of the hydrated monomeric Q(O)(H) Species persisted from after the induction period through to the late stages of the hydration reaction; this indicates that this species is unlikely to result from surface hydroxylation of C3S; an upfield shift of this species occurred with increasing hydration, indicating a possible change of environment for the silicate species. The amount of Q(O)(H) produced was found to increase at higher temperatures. Potential mechanisms for polymerization were assessed and a model in which dimeric-silicate units are linked together by insertion of monomers (dimer --> pentamer --> octomer) was found to give the best fit to the observed data; these results support a dreierketten model for the structure of the hydrate.