共查询到10条相似文献,搜索用时 234 毫秒
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The transport properties of ionic liquids (ILs) are crucial properties in view of their applications in electrochem-ical devices. One of the most important advantages of ILs is that their chemical–physical properties and conse-quently their bulk performances can be well tuned by optimizing the chemical structures of their ions. This will require elucidating the structural features of the ions that fundamentally determine the characteristics of the nanostructures and the viscosities of ILs. Here we showed for the first time that the“rigidity”, the order, and the compactness of the three-dimensional ionic networks generated by the anions and the cation head groups determine the formation and the sizes of the nanostructures in the apolar domains of ILs. We also found that the properties of ionic networks are governed by the conformational flexibility and the symmetry of the anion and/or the cation head group. The thermal stability of the nanostructures of ILs was shown to be con-trolled by the sensitivity of the conformational equilibrium of the anion to the change of temperature. We showed that the viscosity of ILs is strongly related to the symmetry and the flexibility of the constitute ions rather than to the size of the nanostructures of ILs. Therefore, the characteristics of the nanostructures and the viscosities of ILs, especially the thermal stability of the nanostructures, can be fine-tuned by tailoring the symmetry and the conformational flexibility of the anion. 相似文献
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In spinning basalt fibres, the drafting force is in the same range as in spinning of glass fibres. The effect of the drafting
force can not be considered in the calculation for the strength and rigidity of the bottom of the spinneret.
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Translated from Khimicheskie Volokna, No. 5, pp. 47–50, September–October, 2007. 相似文献
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Investigation of the effects of fatty acids on the compressive strength of the concrete and the grindability of the cement 总被引:1,自引:0,他引:1
In cement industry, a great energy consumption has been observed during grinding of clinker. To reduce this consumption, some waste products have been used as grinding aids.In this investigation, the effects of sunflower oil (SO), oleic acid (OA), stearic acid (SA), myristic acid (MA) and lauric acid (LA) on the fineness and strength of the cement have been examined. These aids were added into clinker in certain ratios based on the cement clinker weight and the grinding has been done for a definite time at the same condition.All of the fatty acids used increased the fineness as compared with the cement without the grinding additives. SO and OA decreased the strength significantly, LA decreased it to a lesser extent and SA increased it definitely according to the common cement. But MA did not alter the strength of the cement as much as SA. In addition, the covering of the balls influences the grinding of cement clinker unfavourably. 相似文献
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Igor G. Medvedev 《Electrochimica acta》2008,53(22):6545-6558
Effect of the density of the electronic states at the valence orbital of the bridge redox molecule on the dependence of the tunnel current on the overvoltage and on the width at half maximum of the current-overvoltage curve is studied. A number of the approximate expressions for the density of states, the tunnel current and the width are obtained in the fully adiabatic limit for different particular cases. It is shown that at small values of the coupling of the electronic levels of the electrodes with the valence orbital of the redox molecule and the small values of the bias voltage two regions of the reorganization Gibbs energy exist with different dependence of the width on the reorganization Gibbs energy. The results of calculations of the density of states, the tunnel current and the width are presented and used for the interpretation of the experimental data [N.G. Tao, Phys. Rev. Lett. 76 (1996) 4066, I. Visoly-Fisher, K. Daie, Y. Terazono, C. Herrero, F. Fungo, L. Otero, E. Durantini, J.J. Silber, L. Sereno, D. Gust, T.A. Moore, A.L. Moore, S.M. Lindsay, PNAS 103 (2006) 8686]. 相似文献
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Cotton cellulose was chemically modified by introducing acrylamide, acrylonitrile and carboxyalkyl moieties in the form of groups or polymers. In carbamylethylated, cyanoethylated and carboxymethylated cotton, these moieties are in monomeric groups, whereas, in graft copolymers of cotton cellulose with acrylamide, acrylonitrile or acrylic acid, the moieties are in polymeric forms. These substrates were dyed independently using direct, acid, basic or reactive dyes. Results showed that at roughly equal nitrogen content, polyacrylamide–cotton graft copolymer exhibited a much higher colour strength than carbamylethylated cotton when the two substrates were dyed using basic dye. The opposite is the case for direct and reactive dyes. The acid dye produced comparable colour strengths. Similar trends were observed when the other samples were dyed with these four dyes. The results were explained in terms of microstructural changes in the physical and chemical structure of cotton caused by the etherification and grafting reactions. 相似文献
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The effect of the hugh-temperature (800–1000°C) treatment in air of the Cr2O3/Al2O3 catalyst, which contained 18Cr2O3 + 0.4Na+, wt % and was prepared under laboratory conditions with the use of Pural SB1 grade high-purity pseudoboehmite, on the variation in the phase composition of the catalyst, specific surface, and catalytic characteristics in the dehydrogenation reaction of n-butane (yield and selectivity by ΣC4 olefins and 1,3-butadiene, conversion of n-butane) was investigated depending on the calcination temperature of the catalyst. It is shown that thermal stability depends on the following main factors: the method preparation of catalysts, the phase composition of the starting aluminum hydroxide, carrier texture, and the presence of modifying additions and impurities of other metals. In the case of the same chemical composition of the catalyst, the samples obtained by the wet mixing of pseudoboehmite with an aqueous solution of chromic anhydride are most thermally stable compared with the impregnation samples. It is established that the addition of cerium improves the thermal stability and activity of the impregnation Al-Cr catalyst, while the impurity of the Fe3+ ions (up to 0.1 wt %) does not worsen these characteristics. The investigated samples of the catalyst are more thermally stable than the imported industrial catalyst, which loses activity and specific surface after calcination at 900–1000°C. The determination of the thermal stability of fresh catalysts and the factors affecting it can be used as the preliminary evaluation of the future lifetime of catalysts. 相似文献
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以气煤、肥煤、焦煤、瘦煤为样煤,进行了样煤的粉碎、有机溶剂溶胀和硝酸氧化处理,考察了处理后煤样中的药用腐植酸得率。结果表明,吡啶和N,N-二甲基吡咯烷酮是溶胀较好的溶剂;样煤粉碎后,随着粒度的减小,煤的溶胀率增加;粒度粉碎至200目的气、肥煤经吡啶溶胀和硝酸氧化后,煤样的药用腐植酸得率可达到73.0%和71.4%,而经甲醇溶胀和硝酸氧化的200目气煤药用腐植酸得率为56.4%和58.4%。实验结果表明,煤样经过溶胀和硝酸氧化处理,对药用腐植酸的提取有促进作用。 相似文献