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161.
Jordi Ibez Lluís Artús Ramon Cusc ngel Lpez Esperanza Menndez María C. Andrade 《Journal of Raman spectroscopy : JRS》2007,38(1):61-67
We present a micro‐Raman study on the hydration and carbonation of the main silicate phases of Portland cement, i.e. monoclinic dicalcium silicate (C2S) and monoclinic tricalcium silicate (C3S). We investigate the reaction products and the loss of crystallinity induced by hydration on these two compounds. In the CO2‐contaminated pastes we find that calcite, aragonite, and vaterite are inhomogeneously formed. We study sample cross sections to evaluate the maximum depth at which CaCO3 is formed. We find that carbonation is limited to the first 500–1000 µm from the surface in the C3S pastes, while in C2S pastes CaCO3 is formed well beyond this depth. Our results show the great potential of Raman spectroscopy in the study of the chemistry of cements. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
162.
Some possibilities of NMR spectroscopy (mainly spin-spin relaxation) in investigations of hydration and other polymer-solvent interactions during the temperature-induced phase separation in aqueous polymer solutions are described. A certain portion of water molecules bound in phase-separated mesoglobules was revealed. The residence time of the bound HDO for poly(vinyl methyl ether) (PVME)/D2O solution (c = 6 wt%) is 1.2 ms. With time a slow release of originally bound water from the respective mesoglobules was observed. For highly concentrated PVME/D2O solutions (c = 20–60 wt%), the residence time of bound HDO ≫ 2.7 ms and fractions of bound water unchanged even for 70 h were found. A similar behaviour as described above for water (HDO) was also found for EtOH molecules in PVME/D2O/EtOH solutions. 相似文献
163.
Dr. Masafumi Ueda Akimi Tahara Dr. Masashi Hasegawa Dr. Takashi Shirahata Prof. Dr. Yasuhiro Mazaki Prof. Dr. Yohji Misaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4984-4991
[5]Radialene with quintuple 4,5-benzo-1,3-dithiol-2-ylidenes (DTs) easily forms a stable polycationic salt ( 1 )4+(BF4−)4 owing to its aromatic character in the central cyclopentadienide ring. In this work, it was found that the polycationic salt ( 1 )4+ underwent a hydration reaction in moist polar solvent to give several unexpected products, namely, an oxygen adduct dicationic salt ( 2 )2+, a tetrathiafulvalene (TTF) vinylogue ( 3 ) with 1,4-dithiine-2(3H)-one moieties, and an oxygen adduct of π-extended TTF with a cyclopentenone core ( 4 ). Their molecular structures were fully determined by X-ray crystal-structure analysis. In this reaction, irreversible hydration to the polycationic salt might either initiate the ring expansion and lead to the successive hydration at the specific cationic DT ring (for 3 ), or promote the transannular reactions to the next DT ring followed by elimination of the DT ring (for 4 ). Cyclic voltammetry and differential pulse voltammetry measurements for compound 3 indicated the occurrence of multi redox process resulting from electronic delocalization on the vinylogous TTF moiety. The electronic structures of the cationic species of 3 were also investigated by electronic spectra. 相似文献
164.
Dr. M. Bokor Dr. Á. Tantos A. Mészáros B. Jenei R. Haminda P. Tompa Prof. K. Tompa 《Chemphyschem》2020,21(13):1420-1428
Wide-line 1H NMR measurements were extended and all results were interpreted in a thermodynamics-based new approach on aqueous solutions of thymosin-β4 (Tβ4), stabilin cytoplasmic domain (CTD), and their 1 : 1 complex. Energy distributions of potential barriers controlling the motion of protein-bound water molecules were determined. Heterogeneous and homogeneous regions were found in the protein-water interface. The measure of heterogeneity of this interface gives quantitative value for the portion of disordered parts in the protein. Ordered structural elements were found extending up to ∼20 % of the individual whole proteins. About 40 % of the binding sites of free Tβ4 get involved in bonds holding the complex together. The complex has the most heterogeneous solvent accessible surface (SAS) in terms of protein-water interactions. The complex is more disordered than Tβ4 or stabilin CTD. The greater SAS area of the complex is interpreted as a clear sign of its open structure. 相似文献
165.
Water absorbed by nylons appears to be partitioned into interlamellar and interfibrillar spaces. The amount of water in the interfibrillar region remains essentially unchanged with increasing draw ratio, whereas that in the interlamellar regions decreases with draw ratio; the latter accounts for the decrease in the water uptake in the drawn fibers. These results suggest that the amount of the amorphous material in the interfibrillar regions remains unchanged during drawing, and the increase in the crystallinity during drawing results from the incorporation of the amorphous chain segments in the interlamellar regions into the crystalline lamellae. Further, the interfibrillar water is more tightly bound than the interlamellar water. The length of the longitudinal channels into which water diffuses is about the same as that of the fibrils, and increases from ca. 1500 to 2000 Å upon drawing. The longitudinal channels are highly oriented even in undrawn fibers, and their misorientation increases from 5° to 15° upon drawing. These channels can be described as surface fractals of dimension 3.4–3.6. © 1994 John Wiley & Sons, Inc. 相似文献
166.
This paper presents results of thermokinetic studies on the early stages of hydration of some slag minerals, slag alkaline binders of traditional and new-generation compounds. A possibility of adjustment and control of hardening processes through thermokinetic indices of hydration (intensity and completeness of heat evolution) for various compounds, types and quantities of the alkaline components and temperatures is proved. 相似文献
167.
The belite material produced from limestone and waste silica was the subject of numerous investigations. In order to improve the hydraulic activity, some amount of barite was added to the raw mixture. The properties of belite phase were studied by use of differential thermal analysis, calorimetry and other methods. The influence of barium on the hydraulic activity of belite has been thus confirmed. The hydraulic activity increase in the presence of barium depends on the stabilizing action of additive accompanied by the proper thermal treatment in the α′-Ca2SiO4 stability range. 相似文献
168.
On the Hydration and Dehydration Behaviour of Magnesium Hydrogensulfate Mg(HSO4)2 · H2O has been prepared by crystallization from diluted sulfuric acid. The thermal destruction leads to the formation of siccative Mg(HSO4)2. This process is reversible, i. e., Mg(HSO4)2 rehydrates during cooling under formation of Mg(HSO4)2. H2O. Due to further water reception Mg(HSO4)2 · H2O decomposes at a temperature of 50°C forming Kieserite (MgSO4 · H2), MgSO4 · 1,25H2O, sulfuric acid, and water. During gentle warming of this heterogenous phase mixture it reacts under reconstruction of Mg(HSO4)2 · H2O. The thermal measurements have been carried out in dynamic as well as in static gas atmosphere. The strong dependence of the decomposition temperatures from the partial pressure of the gaseous products could be demonstrated by in situ X-ray measurements. 相似文献
169.
Journal of Thermal Analysis and Calorimetry - The hydration of C3A, C3S and C3A+C3S mixtures was examined by thermogravimetry, differential thermogravimetry and calorimetry. The results showed the... 相似文献
170.
钾促进型Co-Mo系耐硫变换催化剂性能研究 总被引:4,自引:0,他引:4
采用常压微反色谱评价装置,TPR,XRD和SEM等技术,考察了钾对Co-Mo系耐硫变换催化剂活性及抗水合性能的影响.结果表明:在原料气中H2S含量大于0.05%的条件下,钾的加入量存在一个最佳范围;在原料气中H2S含量小于0.05%的条件下,增加催化剂中的钾含量,可以提高催化剂“捕硫”的能力,从而能提高催化剂耐“低硫”的能力.在高于露点温度18~20℃的苛刻条件下,钾的加入能促进γ-Al2O3载体与水蒸气的水合反应,使催化剂的抗水合性变差.还探讨了催化剂发生水合反应后对其活性的影响.结果表明,γ-Al2O3载体发生水合相变后能引起催化剂活性大幅度下降,而钾的加入加剧了催化剂发生水合反应的程度,导致其催化活性进一步下降. 相似文献