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121.
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Eslami Farnaz Pourayoubi Mehrdad Sabbaghi Fahimeh Dušek Michal Baniyaghoob Sahar Skořepová Eliška 《Crystallography Reports》2022,67(2):218-223
Crystallography Reports - For structures with a C2PO2 skeleton, a comparison of “single-and-half” phosphorus–oxygen bonds with single and double phosphorus–oxygen bonds is... 相似文献
123.
A modified polystyrene, poly(styrene-co-p-(hexafluoro-2-hydroxy-2-propyl)styrene) (FPS), was blended with syndiotactic and/or isotactic poly(methyl methacrylate) (PMMA) in toluene. Blends were prepared under different conditions to control the self-aggregation of the PMMA segments. The formation of hydrogen bonding and the attendant changes in the aggregation or crystallization of PMMA segments were determined in the solid state by means of FTIR and DSC. The results indicate that for the binary blends, the aggregation of PMMA segments is diminished by hydrogen bonding interaction with either s-PMMA or i-PMMA, and that the interaction is stronger with the s-PMMA blends. For the ternary blends, FPS/s-PMMA/i-PMMA, the preference for stereocomplexation in the system with hydrogen bonding may be attributed to the “kink-nucleated” mechanism, which needs relatively short chain lengths of PMMA segments. Regardless of the order of addition of the components, the formation of crystalline stereocomplexes of s- and i-PMMA could be readily detected. Therefore, the miscibility of the polymer blends is dependent on the competition between the self-aggregation of the s- or i-PMMA segments, stereocomplexation and the hydrogen bonding interaction of PMMA segments with FPS. 相似文献
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The lattice constants of the compound Ca2NaK(PO4)2 have been studied at room temperature using an X-ray powder diffractometer and also in the temperature range from 20 up to 1000 °C by Guinier-Lenné-technology. A hexagonal lattice with the parameters a0 = 5.4367 Å and c0 = 7.3125 Å and a cell volume of 187.18 Å3 has been determined for the high temperature phase, existing from 670 °C upward. At temperatures below 670 °C a superlattice structure is formed by tripling the axis a, a ′, and c so that it results in a hexagonal superlattice structure cell with the lattice constants of a0 = 16.311 Å and c0 = 21.939 Å and a cell volume of 5054 Å3. 相似文献
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The influence of the orientation and dopant on the dissolution of GaAs surfaces in H2–HCl gas mixtures has been investigated. For this purpose the etch rates, temperature regions of different etching behaviour and the corresponding activation energies were determined for temperatures ranging from 540 °C to 945 °C. The etch rate anisotropy is correlated with the three existing temperature regions of different dissolution mechanisms. The orientation-dependent transition temperatures are influenced by the dopant and can be related to the thermodynamic data of the dopant. 相似文献
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Cobalt‐Embedded Nitrogen‐Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values 下载免费PDF全文
Dr. Xiaoxin Zou Xiaoxi Huang Dr. Anandarup Goswami Dr. Rafael Silva Dr. Bhaskar R. Sathe Eliška Mikmeková Prof. Tewodros Asefa 《Angewandte Chemie (International ed. in English)》2014,53(17):4372-4376
Despite being technically possible, splitting water to generate hydrogen is still practically unfeasible due mainly to the lack of sustainable and efficient catalysts for the half reactions involved. Herein we report the synthesis of cobalt‐embedded nitrogen‐rich carbon nanotubes (NRCNTs) that 1) can efficiently electrocatalyze the hydrogen evolution reaction (HER) with activities close to that of Pt and 2) function well under acidic, neutral or basic media alike, allowing them to be coupled with the best available oxygen‐evolving catalysts—which also play crucial roles in the overall water‐splitting reaction. The materials are synthesized by a simple, easily scalable synthetic route involving thermal treatment of Co2+‐embedded graphitic carbon nitride derived from inexpensive starting materials (dicyandiamide and CoCl2). The materials’ efficient catalytic activity is mainly attributed to their nitrogen dopants and concomitant structural defects. 相似文献
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Sodium silicate-aluminate aqueous systems with various contents of Na2O and SiO2 containing triethanolamine were crystallized. Optimum Na2O and SiO2 contents have been observed to give NaA and NaX zeolite crystals with dimensions up to 80 μm. For NaA crystals the values are: ∼ 3.5 mass% Na2O, ∼ 1.65 mass% SiO2; for NaX crystals ∼ 2.5 mass% Na2O, ∼ 1.5 mass% SiO2. – The effect of other additives on crystal size is proved. – The results are discussed in terms of nucleation and growth, reaction rate, and supersaturation. Supposition are made to gain larger crystals by maintaining the excess of solute over a longer period of time. 相似文献