Strength and hydration products of reactive MgO-silica pastes

The reaction between MgO and microsilica has been studied by many researchers, who confirmed the formation of magnesium silicate hydrate. The blend was reported to have the potential as a novel material for construction and environment purposes. However, the characteristics of MgO vary significantly, e.g., reactivity and purity, which would have an effect on the hydration process of MgO-silica blend. This paper investigated the strength and hydration products of reactive MgO and silica blend at room temperature up to 90 days. The existence of magnesium silicate hydrate after 7 days' curing was confirmed with the help of infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. The microstructural and elemental analysis of the resulting magnesium silicate hydrate was conducted using scanning electron microscopy and energy dispersive spectroscopy. In addition, the effect of characteristics of MgO on the hydration process was discussed. It was found that the synthesis of magnesium silicate hydrate was highly dependent on the reactivity of the precursors. MgO and silica with higher reactivity resulted in higher formation rate of magnesium silicate hydrate. In addition, the impurity in the MgO affects the pH value of the blends, which in turn determines the solubility of silica and the formation of magnesium silicate hydrate. © 2014 Elsevier Ltd. All rights reserved.

超声波对HCFC-141b水合物形成过程的影响研究

针对水合物形成过程中存在成核诱导期长、过冷度大，形成速度慢的问题，本文以HCFC-141b（1，1-dichloro-1-flooroethane）作为研究工质，将超声波引入水合物形成过程中，研究超声波对水合物形成的影响。建立了包括超声波水合反应系统、数据采集和图像采集系统的可视化低温实验系统。利用这套实验系统，分别实验研究了频率为20kHz和15kHz，功率为0-1000w的超声波对HCFC-141b水合物的形成影响。实验结果表明，超声波对水合物的形成有明显的影响。水合物形成过程主要分为三阶段：冷却期、

水合物及其在多孔介质中导热性能的研究

气体水合物是一种笼形混合物，它是水分子形成的主体框架包裹其他客体分子形成的一种非化学计量的冰状物质。在海底和大陆的永冻区有大量的天然气水合物，由于天然气水合物富含天然气资源（约2x1016时），并且其稳定性关系到全球气候和海洋地质结构的变化，因而受到广泛的关注。所以在考虑对该资源进行热开采和考察地球温压变化对含水合物层的影响时，有必要掌握水合物的热物性和含水合物层的有效导热系数（ETC）。另一方面，水合物虽然具有明确的晶体结构，但研究表明n型水合物具有玻璃体的导热特性，即其具有低导热系数和导热系数随温度变

海底沉积层中水合物成藏过程模拟

水合物成藏是一种动态演变过程，从生成和分解速度相对大小角度提出了天然气水合物的动态成藏理论；分析指出天然气水合物储层状态主要存在三种类型：成长型（包括渗透型与扩散型）、成熟型和消退型，必须结合经济型指标对这三种类型水合物藏进行开采可行性研究。 通过在自制的透明鼓泡反应釜内模拟气体迁移与水合物形成实验，解释了气体迁移对体系内传热与传质、溶解性质、过压等的影响因，进一步指出需要研究新的水合物相图。 从传热角度建立了水合物生长模型，计算并比较了南海北部陆坡琼东南盆地里甲烷水合物在渗漏系统和扩散系统下的生长速度，指出前者比后者快约20-40倍。 建立了水-气（游离气）-水合物-盐反应的多相流模型，演绎了在四个不同时刻随着水合物的形成，溶解度、渗透率、毛细压力、饱和度及盐度等的联动演变关系，并分析和比较了在沉积层水合物稳定区域内不同游离气饱和度和甲烷渗漏通量情况下水合物的形成过程和三种成藏类别。 反演了神狐海域水合物的形成，指出该区很可能是属于发育阶段的成长型渗漏系统水合物储藏，按照甲烷渗漏通量为0.5kg/m2·a计算，该地区已演化了约4800a，还需要约2700ka孔隙中水合物可到最大体积饱和度，达约75%，并在此后游离气将溢出沉积层进入海水中；计算得最终的甲烷水合物储量约为1.47×109m3，即该区最终将储存着约2200亿立方米甲烷气，是现在预测的约13倍！

纳米流体中HFC134a水合物的生成过程

提出制冷剂气体水合物在纳米流体中快速生成的设想，通过HFC134a气体水合物在纳米铜流体（由0．04％的十二烷基苯磺酸钠（SDBS）水溶液和名义直径为25nm的纳米铜粒子组成）中的生成实验验证了此设想．实验结果表明，与去离子水中HFC134a气体水合物的生成过程相比，纳米铜流体中SDBS是造成HFC134a气体水合物诱导时问明显缩短的主要原因，而纳米铜粒子对诱导时间的影响不大；纳米铜流体中SDBS的乳化作用和纳米铜粒子大比表面积大大促进了HFC134a在水中的溶解；纳米铜粒子的加入明显加强了HFC134a气体水合物生成过程中的传热传质，随着纳米铜粒子数的增加，HFC134a气体水合物生成过程明显缩短．

用分子动力学模拟甲烷水合物热激法分解

用分子动力学模拟方法研究甲烷水合物热激法分解，系统地研究注入340 K液态水的结构Ⅰ型甲烷水合物的分解机理.模拟显示水合物表层水分子与高温液态水分子接触获得热能，分子运动激烈，摆脱水分子间的氢键束缚，笼状结构被破坏.甲烷分子获得热能从笼中挣脱，向外体系扩散.热能通过分子碰撞从外层传递给内层水分子，水合物逐层分解.对比注入277K液态水体系模拟结果，得出热激法促进水合物分解.

用分子动力学模拟水合物储氢

用分子动力学（MD）模拟方法系统研究了结构Ⅰ型（SⅠ）和结构H型（SH）氢气水合物中氢气的占据情况并确定了氢气水合物的稳定结构：SⅠ水合物氢气分子数小胞中为2，大胞中为3；SH水合物氢气分子数小胞中为2，中胞中为2，大胞中为11．分析了稳定情况下水合物各胞腔内氢气分子之间的径向分布函数（RDF），得出了氢气分子在各胞腔内的稳定位置．由稳定位置得到了稳定结构下氢气水合物的储氢质量分数：SⅠ为5．085％，SH为6．467％．与实验对比得出结论：SH水合物稳定结构下的储氢能力最强．

气体水合物生成特性实验研究

实验研究了添加剂对甲烷气体水合物形成过程的影响。发现微量的表面活性剂降低了甲烷气体水合物在静止反应器中形成的诱导时间，并使水合物快速形成和生长，提高了水合物形成过程中的填充密度。阴离子表面活性剂（十二烷基硫酸钠）对水合物生长的促进作用比非离子表面活性剂（烷基多糖苷）强。液态烃环戊烷降低了水合物形成的诱导时间，但环戊烷不能提高水合物的填充密度。

二氧化碳收集利用与处置技术分析

化石燃料的燃烧是百余年来大气中二氧化碳（CO2）浓度增加的主要原因。CO2的收集和处置则是抑制这一趋势的有效途径。本文通过对现有收集利用和处置技术的分析，认为火电厂是收集CO2的重点考虑对象；CO2用于三次采油及天然气回收在技术上和经济上比较可行；蓄水层储气前景广阔值得研究；深海处置有待进一步探索；CO2用于置换开采天然气水合物也是很有前景的方案。

CO2置换开采天然气水合物研究进展

介绍了近年来CO2置换开采天然气水合物技术的研究进展；论述了CO2与天然气水合物中CH4置换反应在热力学上的可能性；认为正确理解置换反应机理、探索新的反应技术并提高反应速率是置换开采技术走向产业化的关键。

Clathrate Dissociation Conditions for Methane + Tetra-n-butyl Ammonium Bromide (TBAB) + Water

Hydrate equilibrium data of the CH4 + tetra-n-butyl ammonium bromide (TBAB) + water have been measured by using the isothermal pressure search method for four components of TBAB aqueous solutions. The three-phase equilibrium lines obtained in the present study are shifted to the low-temperature or high-pressure side from that of the stoichiometric TBAB solution. Moreover, methane uptake into semi-clathrates is confirmed by a shift in the clathrate regions when methane is present. The experiments are carried out in the pressure range of (0.5 to 11) MPa and in the temperature range of (281.15 to 295.15) K.

Study on methane hydration process in a semi-continuous stirred tank reactor

The methane hydration process is investigated in a semi-continuous stirred tank reactor. Liquid temperatures and reaction rates without stirrer are compared with those occurring with stirrer, while at the same time better stirring conditions of the methane hydration process are given by the experiments. Some basic data of fluid mechanics, for example, stirring Reynolds number, Froucle number and stirrer power, are calculated during the methane hydration process, which can be applied to evaluate stirrer capacity and provide some basic data for a scaled up reactor. Based on experiment and calculations in this work, some conclusions are drawn. First, the stirrer has great influence on the methane hydration process. Batch stirring is helpful to improve the mass transfer and heat transfer performances of the methane hydration process. Second, induction time can be shortened effectively by use of the stirrer. Third, in this paper, the appropriate stirring velocity and stirring time were 320 rpm and 30 min, respectively, at 5.0 MPa, for which the storage capacity and reaction time were 159.1 V/V and 370 min, respectively. Under the condition of the on-flow state, the initial stirring Reynolds number of the fluid and the stirring power were 12,150 and 0.54 W, respectively. Fourth, some suggestions, for example, the use of another type of stirrer or some baffles, are proposed to accelerate the methane hydration process. Comparing with literature data, higher storage capacity and hydration rate are achieved in this work. Moreover, some fluid mechanics parameters are calculated, which can provide some references to engineering application.

Dual-wavelength photochromic fulgides for parallel recording memory

Two photochromic fulgides, 2-{2-[4-(N,N-dimethylnilino)-5-methyl-4-oxazoly]}ethylidene-4-(1-methylethylidene) tetrahydrofuran-2,5-dione (A) and 3-(1,2-dimethyl-5-phenyl-3-pyrolloethylidene)-4-(1-methylethylidene)tetrahydrofuran-2,5-dione (B), doped in PMMA as candidates of dual-wavelength optical memory for parallel recording has been investigated. With 488 nm-laser and 650 nm-laser, both "cross" and "star" images are recorded on the fulgides-PMMA film and read out clearly, respectively. Crosstalk between two fulgides in PMMA matrix and nondestructive readout has also been explored. The results show that no significant cross-talk is detected between them, and nondestructive readout is up to 201 times. (C) 2005 Elsevier B.V. All rights reserved.

天然气水合物沉积物力学性质的试验研究

利用研制的天然气水合物沉积物合成及力学性质一体化试验设备,以粉细砂土作为土骨架,分别对冰沉积物以及对四氢呋喃(THF)、二氧化碳(CO_2)和甲烷3种水合物沉积物进行了室内合成和三轴剪切试验,分析和比较了这4种沉积物样品的应力-应变和强度特性,初步探究了冰和不同气体在水合物沉积物强度中所起的作用. 试验结果表明:4种沉积物均表现为塑性破坏;围压越大,水合物沉积物强度越高;在水合物含量相同条件下,不同气体水合物会使水合物沉积物的强度不同

沉积物中导热体周围水合物分解范围研究

沉积物水合物在热源周围的分解范围是水合物热开采以及相关灾害分析的重要基础数据.该文针对平面内边界有恒温热源的水合物热分解范围问题进行了理论分析和四氢呋喃水合物沉积物模型实验,并将两者结果进行了对比.结果表明:沉积物水合物最大分解范围主要取决于热源与环境温度的温差;热源周围水合物热分解最大范围的理论值与实验值接近,误差小于5%