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针对两种新型稀土型储氢合金La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2的储氢特性进行研究分析。实验表明,相同温度下,La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2合金的PCT曲线基本重合,且都具有优良的吸氢动力学性能;相比之下,后者的滞后系数要小于前者,吸氢量较大,吸氢速率也较快,故其储氢性能较优。300次吸放氢循环实验结果表明,La0.5Y0.5Ni4.8Al0.2合金的吸氢动力学性能虽然略有下降,但抗粉化性能较好。 相似文献
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用X射线衍射方法(XRD)研究了Mg3Pr合金吸放氢前后的结构变化。Mg3Pr合金在吸/放氢过程中的压力.组成.等温曲线(PcI)和吸氢动力学曲线表明合金能在室温下吸氢,并且具有良好的吸氢动力学特性,能在4min之内达到饱和吸氢量的90%;其最大吸氢量分别为2.57%(质量分数)。Mg3Pr合金的吸氢动力学曲线可用Avrami-Erofeev方程拟合,说明吸氢过程符合形核长大机制。同时,也计算了Mg3Pr-H氢化反应的熵和焓。 相似文献
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研究了Ti/Zr比变化对Ti Mn基Laves相贮氢合金贮氢性能的影响,发现随Ti/Zr、Mn/Cr比降低,合金放氢压降低,贮氢量略微增加,平台坡度变陡。 相似文献
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AB5型储氢合金在气固储氢、氢压缩、镍氢电池等领域具有广阔的应用前景,其循环稳定性是人们的一个关注点.本实验通过电弧熔炼的冶金方法,结合长时间退火的热处理工艺,制备了以CaCu5相为主相,以富Ni/Sn相为次要相,以及少量C相和Si相弥散分布的LaNi5.5 Sn1.5-C-Si合金,并结合LaNi5基础合金,研究了LaNi5.5 Sn1.5-C-Si合金在1000周吸/放氢循环过程中的储氢性能变化规律.结果表明,随着吸/放氢循环,合金的储氢容量略有降低,吸/放氢平台发生细微的倾斜,但以上变化远远小于LaNi5合金循环1000周的变化.LaNi5.5 Sn1.5-C-Si合金循环1000周的容量保持率高达98%,这可能是由于C和Si相的弥散分布对合金颗粒的粉化起到了缓冲作用.此外,LaNi5.5 Sn1.5-C-Si合金具有良好的吸氢动力学性能,在383~423 K、2 MPa氢压下200 s内即可完全吸氢,合金良好的吸氢动力学性能可能与富Ni/Sn相的催化作用有关. 相似文献
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烧结工艺对贮氢合金La0.67Mg0.33Ni2.5Co0.5的微观组织结构及电化学性能影响的研究 总被引:1,自引:0,他引:1
系统研究了固相反应烧结方法制备La0.67Mg0.33Ni2.5Co0.5贮氢合金的烧结工艺对该合金的微观组织结构及电化学性能的影响规律.分析和研究了合金的微观组织结构、电化学放电性能及Mg含量的挥发损失问题.XRD和SEM及EPMA分析结果表明,在不同烧结条件下合金均由不合Mg的LaNi5相、富Mg的LaNi3相及一个贫Mg的LaNix(x=3.0~3.8)相三相组成.当烧结温度不超过1203k时合金主相为LaNi3相,当烧结温度超过1203K,LaNi5相逐步成为主相.原子吸收光谱分析结果表明,烧结温度不超过1203K,Mg元素没有明显损失;当烧结温度超过1203K,会引起Mg的大量挥发损失.电化学性能分析结果表明,烧结温度不超过1203K,合金放电能力主要受合金组织形成与均匀性影响;而烧结温度超过1203K,Mg元素挥发损失成为影响合金放电能力的决定因素.烧结条件为873~1123k保持24h、1203k保持2h,是制备La0.67Mg0.33Ni2
5Co0.5贮氢合金的适宜工艺.用该工艺制备的La0 67Mg0.33Ni2.5Co0.5贮氢合金Mg含量稳定(2.92%质量分数)、微观组织均匀、放电容量高(395mAh/g)、活化性能好(2个循环). 相似文献
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介绍了两个先进的二元合金有序化反应动力学模型、以及利用计算机对此类合金组织演化模拟取得的进展。先进的模型可成功地描述原子有序化及相分离 ,并将形核、长大和粗化在同一物理模型内加以考虑。利用此模型已对许多重要新型合金的相变动力学进行了模拟研究 相似文献
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La0.67Ca0.33MnO3 (LCMO)/La0.67Sr0.33CoO3 (LSCO)/LCMO trilayer films are fabricated on single-crystal substrates NdGaO3 (110) and the interlayer coupling are investigated. Compared with LCMO single layer, sandwiches showed the enhanced metal-insulator transition temperature of LCMO layers. The magnetoresistance is dependent on spacer thickness and the peak value dramatically decreases when LSCO layer is thick enough because of shorting by the LSCO layer. The magnetic coercivity HC shows a nonmonotonic behavior with changing spacer layer thickness and the waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom LCMO layers across the spacer layer. 相似文献
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Choon-W. Nahm 《Materials Letters》2011,65(9):1299-1301
The varistor properties of the ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics were investigated for different concentrations of In2O3. The increase of In2O3 concentration slightly increased the sintered density (5.60-5.63 g/cm3) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In2O3. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In2O3 acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 1017 to 0.24 × 1017/cm3 with increasing concentration of In2O3. 相似文献
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Transparent glasses in the system (100−x)Li2B4O7–x(SrO---Bi2O3---Nb2O5) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi2Nb2O9 (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (r) and the loss factor (D) for the lithium borate, Li2B4O7 (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix. 相似文献
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G. R. Gurbanov 《Inorganic Materials》2012,48(9):888-890
Phase equilibria along the PbSbBiS4-Sb2S3 and PbSbBiS4-Bi2S3 joins of the PbS-Sb2S3-Bi2S3 system have been studied for the first time using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and the phase diagrams of the joins have been mapped out. The joins are shown to be pseudobinary with limited series of terminal solid solutions. The solid solutions are p-type semiconductors. 相似文献
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Hollandite-type compounds, Rb2Cr8O16, K2Cr2V6O16 and K2V8O16, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb2Cr8O16 confirms that the structure is similar to that of K2Cr8O16. Magnetic measurements indicate that Rb2Cr8O16 is ferromagnetic below 295K, K2Cr2V6O16 paramagnetic down to 77K and K2V8O16 has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies. 相似文献
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Epitaxial YBa2Cu3O7/La0.7Ca0.3MnO3 (YBCO/LCMO) bi-layers and La0.7Ca0.3MnO3/YBa2Cu3O7 (LCMO/YBCO) bi-layers were grown on (001)LaAlO3 by pulsed laser deposition, and their microstructures were compared by transmission electron microscopy investigation. In the YBCO(100 nm)/LCMO(150 nm) bi-layers, the LCMO layer consists of columnar grains of ~ 17 nm in diameter and contains mixed orientation domains of [100]c, [010]c and [001]c. The YBCO layer is totally c-axis oriented and the YBCO lattices are tilted − 2.5° to + 2.5° as they grew on the rough surfaces of LCMO columnar grains. For the LCMO(140 nm)/YBCO(140 nm) bi-layers, the LCMO/YBCO interface is sharp and flat. The initial 12-nm thickness of the YBCO layer is composed of c-axis oriented domains, and the upper part of YBCO layer is [100] oriented. The LCMO layer was predominantly [001]c oriented while [100]c-oriented domains were occasionally observed. 相似文献
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A systematic study was performed with mixtures consisting of N2, CH4, C2H6 and C3H8, to investigate experimentally phase equilibria and caloric properties and to test the accuracy of thermodynamic correlations. The first part of this Paper reports results of T---p---x---y measurements on ternary systems in the range 20 < p < 120 bar and 140 < T < 220 K. The results are compared with data calculated by generalized equations of state. 相似文献
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We investigated the structural and superconducting properties ofc-axis oriented (YBa2Cu3O7)
nY
/(PrBa2Cu3O7)
npr
superlattices with thicknesses of the individual layers down to one unit cell (10nY1; 18>nPr 1). By transmission electron microscopy and X-ray diffraction we find an excellent structural quality of the samples, though the quantitative analysis shows the existence of defects. In superlattices with decoupled YBa2Cu3O7 layers of two unit cell thickness we find a highT
c
value of 75 K. We probed the flux line structure in the superlattices by measurements of the critical current density in magnetic fields. The experiments show that the flux-line dynamics is dominated by the movement of pancake vortices. 相似文献
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J.A. Luna-Lpez J. Portelles O. Raymond J.M. Siqueiros 《Materials Chemistry and Physics》2009,118(2-3):341-348
Sr0.3Ba0.7Nb2O6 (SBN) and La0.030Sr0.255Ba0.700Nb2O6 (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 °C) and later sintered both at 1400 °C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A1 site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra. 相似文献
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Xiaohua Sun Ying YangQiaoling Zhang Zhimeng LuoShuang Hou Caihua HuangJun Zou 《Materials Science and Engineering: B》2013,178(18):1244-1248
Bi1.5Zn0.5Nb0.5Ti1.5O7 (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba0.6Sr0.4TiO3 (BST) thin films on the Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces. 相似文献