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The viscoelastic properties of the suspension of monodisperse spherical silica produced by hydrolysis of tetraethoxysilane in alcohol solvent with ammonia as a catalyst in polyethylene glycol (PEG) were studied. The results show that the SiO2/PEG suspension possesses the reversible shear thinning and shear thickening behaviors. In the shear thinning region, the loss modulus (G″) almost remains unchanged, whereas the storage modulus (G′) decreases. In the shear thickening region, G″ and G′ increase for the formation of the "clusters". The larger G″ over G′ in all the stress studied shows that the system mainly possesses the viscous property, and that the energy dissipated(Ed) is larger than that stored. Ed of this suspension is proportional to the maximum strain (γmax) rising with the exponent of 1.92 under low shear stress; however, in the shear thickening region, Ed is proportional to γmax rising with the exponent of 5.00. 相似文献
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用浸渍法制备了磷酸锆(ZrP)/PE01复合膜.SEM、电子显微探针分析(EMPA)测试表明:复合膜的表面和内部都有α-ZrP沉积.在0.05 mol/L H2SO4中静态的质子导电性测试证实,复合膜/溶液界面双电层对质子传导具有重要影响.几种价态钒离子渗透率P的大小为:PE01> ZrP6/PE01> ZrP12/PE01> ZrP24/PE01.以PE01膜和ZrP24/PE01膜作为隔膜的全钒液流电池,在电流密度为30 mA/cm2、40 mA/cm2和50 mA/cm2时,库仑效率分别由90.19%、93.09%和94.06%提高到92.42%、94.35%和95.12%,能量效率分别由66.68%、66.09%和61.85%提高到68.01%、67.77%和64.01%. 相似文献
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在AR2000ex型流变仪上对沉淀碳酸钙(Precipitated calcium carbonate,PCC)在PEG(聚乙二醇)悬浮体系进行稳态剪切流变实验。通过2种方法来改变分散体系黏度:1)以PEG200(相对分子质量为200)为连续相,分散体系以10℃为间隔从10℃上升至50℃;2)在30℃用相同的聚合物3种不同相对分子质量的PEG(PEG200、PEG400和PEG600)。结果表明随着温度升高,PCC/PEG200分散体系的临界剪切速率越来越大。在剪切增稠区内流动指数N随温度升高而降低,稠度系数K随着温度升高而升高。临界剪切速率以及临界剪切黏度与温度严格满足Arrhenius关系:η=A exp[Ea/(RT)]。研究发现随温度的变化临界剪切应力不变。随着PEG的相对分子质量增加,分散体系的黏度增加,临界剪切增稠速率减小。PCC粉末的分形结构以及聚集体的形貌使得体系的相对黏度远大于硬球体系的相对黏度。 相似文献
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Magneli phase titanium sub-oxide conductive ceramic Tin O2n-1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/Tin O2n-1 composites were prepared by the impregnation-reduction method. The electrochemical stability of Tin O2n-1 was investigated and the results show almost no change in the redox region after oxidation for 20 h at 1.2 V(vs NHE) in 0.5 mol/L H2SO4 aqueous solution. The catalytic activity and stability of the Pt/Tin O2n-1 toward the oxygen reduction reaction(ORR) in 0.5 mol/L H2SO4 solution were investigated through the accelerated aging tests(AAT), and the morphology of the catalysts before and after the AAT was observed by transmission electron microscopy. At the potential of 0.55 V(vs SCE), the specific kinetic current density of the ORR on the Pt/Tin O2n-1 is about 1.5 times that of the Pt/C. The LSV curves for the Pt/C shift negatively obviously with the half-wave potential shifting about 0.02 V after 8000 cycles AAT, while no obvious change takes place for the LSV curves for the Pt/Tin O2n-1. The Pt particles supported on the carbon aggregate obviously, while the morphology of the Pt supported on Tin O2n-1 remains almost unchanged, which contributes to the electrochemical surface area loss of Pt/C being about 2times that of the Pt/Tin O2n-1. The superior catalytic stability of Pt/Tin O2n-1 toward the ORR could be attributed to the excellent stability of the Tin O2n-1 and the electronic interaction between the metals and the support. 相似文献
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以六水合硝酸钴(Co(NO3)2·6H2O)和硫脲为原料,采用混合溶剂热法制备硫化钴(COS)纳米晶.利用X射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)对硫化钴纳米晶的组成、粒径及表面形貌进行表征.结果表明,在180℃恒温条件下所得粉末样品为六方相CoS纳米粉末,粉末粒径在40nim左右.粉末的产率随温度... 相似文献
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The rheological behavior of fumed silica suspensions in polyethylene glycol(PEG) was studied at steady and oscillatory shear stress using AR 2000 stress controlled rheometer. The systems show reversible shear thickening behavior and the shear-thickening behavior can be explained by the clustering mechanism. The viscosity and the degree of shear-thickening of the systems strongly depend on the mass fraction of the silica, the molecular weigh of PEG and the frequency used in the rheological measurement. The silica volume fraction of the systems is 1.16%- 3. 62%, corresponding to the mass fraction of 4%- 9%. The shear-thickening taking place in the low volume fraction may contribute to the fractal nature of the silica. At oscillatory shear stress, when the shear stress is less than the critical stress, the storage modulus decreases significantly, meanwhile the loss modulus and the complex viscosity almost remain unchanged; when the shear stress is larger than the critical stress, the storage modulus, the loss modulus and the complex viscosity increase with the increase of shear stress. The loss modulus is larger than the storage modulus in the range of stress studied and both moduli depend on frequency. 相似文献
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通过X射线衍射、X射线光电子能谱、透射电镜、扫描电镜以及能谱分析和电化学方法考察制备路线对氧还原反应(ORR)电催化剂Ag-MnOx/C物理性能及其催化活性的影响。结果表明:通过两步法制得的催化剂(Ag-MnOx/C-2)的表面Ag和Mn含量比一步法制备样品(Ag-MnOx/C-1)的高,这使得Ag-MnOx/C-2具有更高的催化活性。Ag-MnOx/C-2表面ORR的电子转移数高于Ag-MnOx/C-1的电子转移数,且在-0.60 V(相对于Hg/HgO)处的比质量动力学电流为46 mA/μg,为Ag/C的23倍。以Ag-MnOx/C-2为阴极催化剂组装的锌-空气电池的最高能量密度高达117 m W/cm2。 相似文献
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全钒液流电池用聚丙烯腈石墨毡电极研究 总被引:8,自引:0,他引:8
利用循环伏安法研究了聚丙烯腈石墨毡在经浓硫酸处理5h后又在450℃条件下恒温2h的电化学性能。结果表明,在硫酸氧钒的酸性溶液中,处理后的电极具有较好的电化学性能。对于负电对V2 /V3 ,△Ep从0.31V降为0.11V,表明处理后的聚丙烯腈石墨毡电极对于负电对具有电化学可逆性,而对于正电对VO2 /VO2 在该电极上却是电化学不可逆的。通过扫描电镜(SEM)图可以看出石墨毡电极表面在处理后除去了表面污染物和一些可能抑制反应的限制层,使表面变得光滑。在不同VOSO4及H2SO4浓度的试验中发现处理后的电极在高浓度的电解液中具有良好的性能。 相似文献
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