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41.
以生石膏为原料,六水氯化镁为形貌控制剂,采用水热法一步合成了无水硫酸钙晶须.借助SEM、TEM、XRD和XPS等测试手段考察了水热条件对无水硫酸钙晶须的影响,研究了无水硫酸钙晶须的生长过程.结果表明:镁/钙摩尔比n(MgCl2·6H2O)/n(CaSO4· 2H2O)=2.5,反应温度180℃,反应时间2h,可生长出长度为20 ~ 40 μm,直径0.5~2 μm的无水硫酸钙晶须.无水硫酸钙晶须生长过程为:片状CaSO4·2H2O-纤维状CaSO4·0.5H2O-纤维状CaSO4. 相似文献
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Anhydrous Amorphous Calcium Oxalate Nanoparticles from Ionic Liquids: Stable Crystallization Intermediates in the Formation of Whewellite 下载免费PDF全文
Aaron Gehl Dr. Michael Dietzsch Dr. Mihail Mondeshki Sven Bach Dr. Tobias Häger Dr. Martin Panthöfer Dr. Bastian Barton Dr. Ute Kolb Prof. Dr. Wolfgang Tremel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18192-18201
The mechanisms by which amorphous intermediates transform into crystalline materials are not well understood. To test the viability and the limits of the classical crystallization, new model systems for crystallization are needed. With a view to elucidating the formation of an amorphous precursor and its subsequent crystallization, the crystallization of calcium oxalate, a biomineral widely occurring in plants, is investigated. Amorphous calcium oxalate (ACO) precipitated from an aqueous solution is described as a hydrated metastable phase, as often observed during low‐temperature inorganic synthesis and biomineralization. In the presence of water, ACO rapidly transforms into hydrated whewellite (monohydrate, CaC2O4 ? H2O, COM). The problem of fast crystallization kinetics is circumvented by synthesizing anhydrous ACO from a pure ionic liquid (IL‐ACO) for the first time. IL‐ACO is stable in the absence of water at ambient temperature. It is obtained as well‐defined, non‐agglomerated particles with diameters of 15–20 nm. When exposed to water, it crystallizes to give (hydrated) COM through a dissolution/recrystallization mechanism. 相似文献
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Hydrolysis and condensation reactions in an anhydrous sol-gel system comprising tetraethyl orthosilicate (TEOS, Si(OC2H5)4), boric acid (H3BO3) and ethanol have been studied using X-ray diffraction and NMR spectroscopy, and similarities and differences with the more traditional aqueous system are discussed. Boric acid is able to hydrolyse TEOS directly, and subsequent condensation reactions form borosiloxane (=B–O–Si) and siloxane (Si–O–Si) linkages. In an aqueous system, borosiloxanes are unstable to hydrolysis and are formed only upon heat treatment of the gel, a restriction avoided with anhydrous conditions. The anhydrous mixture is stable indefinitely against gelation, but can be readily gelled by addition of NaOH in ethanol. This system may be useful for preparing borosilicate glasses at lower temperatures with good homogeneity. 相似文献
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无水CaCl2和FeCl3·6H2O都是良好的酯化反应催化剂.Fe3+是较强的路易斯酸,无水CaCl2是好的吸水、脱水剂,将二者协同应用于酯化反应中,有效地提高了酯化反应的产率 相似文献
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Raman spectroscopic measurements were carried out for the anhydrous LnCl3·20ROH·XLiCl solutions (Ln3+ = La3+− Lu3+, X = 0–3; ROH = MeOH, EtOH, n‐PrOH) in the liquid state. The salt concentration (X) dependence of the wavenumber for the Ln–Cl stretching Raman band (νLn–Cl) is examined in conjunction with the formation of chloro‐rare‐earth complexes. We have obtained very intriguing results including the fact that the chloro complexations of the middle rare‐earth ions (e.g. gadolinium, holmium ions, etc.) in the MeOH and EtOH solutions show peculiar behavior with regard to the salt concentration dependence: the νLn–Cl wavenumber increases with the increasing chloride concentration. However, the νLn–Cl wavenumbers of the light and heavy rare‐earth (e.g. lanthanum, lutetium, etc.) salt solutions show normal behavior; i.e. νLn–Cl decreases with the increasing chloride concentration. On the other hand, in the n‐PrOH solutions, the νLn–Cl frequency in the solutions of all the rare‐earth elements exhibits a normal behavior. We now present a possible mechanism for this anomalous concentration dependence of coordination of Cl− ions to Ln3+ ions in anhydrous LnCl3 alcohol solutions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
47.
LaCl3:Ce3+晶体生长用无水氯化镧的制备 总被引:1,自引:0,他引:1
本文报道了LaCl3:Ce3+晶体生长用无水氯化镧的氯化焙烧脱水制备方法.应用差热/热重分析研究了LaCl3·7H2O的脱水过程,以寻求避免发生水解反应的有效途径;以LaCl3·7H2O为初始原料,采用氯化氢保护下的焙烧脱水处理进行无水氯化镧的制备,通过系列实验掌握了氯化焙烧脱水处理的最佳工艺条件;为验证所制备无水氯化镧的纯度,采用该原料进行了LaCl3:Ce3+单晶生长.结果表明,在氯化焙烧脱水处理过程中,保持通入足量干燥氯化氢气体,控制焙烧温度于220~230℃,经过6~7h焙烧处理,能够制备出较高纯度的无水氯化镧,所获原料可成功地用于生长无色透明的LaCl3:Ce3+单晶. 相似文献
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Salem Saïd Noureddine Mhadhbi Fadhel Hajlaoui Samia Yahyaoui Alexander J. Norquist Tahar Mhiri 《Phase Transitions》2013,86(1):71-84
Single crystals of [(R)-C5H14N2][Cu(SO4)2(H2O)4]·2H2O (1) were grown through the slow evaporation of a solution containing H2SO4, (R)-C5H12N2 and CuSO4·5H2O. These crystals spontaneously transform to [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) over the course of four days at room temperature. The same single crystal on the same mounting was used for the determination of the structure of (1) and the unit cell determination of (2). A second single crystal of the transformed batch has served for the structural determination of (2). Compound 1 crystallizes in the noncentrosymmetric space group P21 (No. 4) and consists of trimeric [Cu(SO4)2(H2O)4]2? anions, [(R)-C5H14N2]2+ cations and occluded water molecules. Compound 2 crystallizes in P21212 (No. 18) and contains [Cu(H2O)6]2+ cations, [SO4]2? anions and occluded water molecules. The thermal decompositions of compounds 1 and 2 were studied by thermogravimetric analyses and temperature-dependent X-ray diffraction. 相似文献
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Pharmaceutical interaction of the most frequently used substances with fats: lanolin, white soft paraffin and vitamin A palmitate was studied. The mixtures were examined by TLC with different ratios of lanolin and vitamin A palmitate, and white soft paraffin and vitamin A palmitate. Vitamin A in the mixtures was determined by the UV spectrophotometric method according to BP 93. It was established that the rise of lanolin concentration resulted in an increased apparent content of vitamin A in fats as a consequence of lanolin absorption at the wave length of maximum absorption of vitamin A. By an increase of white soft paraffin concentration, an apparent decreased in the content of vitamin A in fats was obtained. Therefore, the suggested UV spectrophotometric method for vitamin A determination has a limited application on fats with high content of lanolin and white soft paraffin. 相似文献
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Zinc chloride anhydrous has been used as an efficient and new catalyst for conversion of ketones and aldehydes to corresponding gem‐dihydroperoxides by aqueous hydrogen peroxide (30%) in room temperature with excellent yields and notable reaction times. 相似文献