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排序方式: 共有559条查询结果,搜索用时 15 毫秒
21.
Dr. Xiaoxiao Wang Dr. Nanping Deng Dr. Liying Wei Dr. Qi Yang Dr. Hengying Xiang Dr. Meng Wang Prof. Bowen Cheng Prof. Weimin Kang 《化学:亚洲杂志》2021,16(19):2852-2870
Lithium-sulfur (Li−S) batteries, possessing excellent theoretical capacities, low cost and nontoxicity, are one of the most promising energy storage battery systems. However, poor conductivity of elemental S and the “shuttle effect” of lithium polysulfides hinder the commercialization of Li−S batteries. These problems are closely related to the interface problems between the cathodes, separators/electrolytes and anodes. The review focuses on interface issues for advanced separators/electrolytes based on nanomaterials in Li−S batteries. In the liquid electrolyte systems, electrolytes/separators and electrodes system can be decorated by nano materials coating for separators and electrospinning nanofiber separators. And, interface of anodes and electrolytes/separators can be modified by nano surface coating, nano composite metal lithium and lithium nano alloy, while the interface between cathodes and electrolytes/separators is designed by nano metal sulfide, nanocarbon-based and other nano materials. In all solid-state electrolyte systems, the focus is to increase the ionic conductivity of the solid electrolytes and reduce the resistance in the cathode/polymer electrolyte and Li/electrolyte interfaces through using nanomaterials. The basic mechanism of these interface problems and the corresponding electrochemical performance are discussed. Based on the most critical factors of the interfaces, we provide some insights on nanomaterials in high-performance liquid or state Li−S batteries in the future. 相似文献
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23.
Bulent E. Yoldas 《Journal of Sol-Gel Science and Technology》1993,1(1):65-77
A significant aspect of sol-gel technology is the capability it provides to affect the substructure of materials by controlling the nature and the kinetics of chemical reactions. This capability allows us to produce novel materials, design unique molecular and pore morphologies, circumvent high-temperature reactions, and modify material properties. The modifications include strongly thermodynamic-dependent high-temperature properties such as sintering, crystallization, and viscosity in glass and ceramic materials. A particularly exciting area for investigation is the optical-electronic field, where a significant dependence of electro-optical properties and photosensitivity on process-induced molecular-structural variations occurs. Understanding the basis for the creation of structural variations in sol-gel processes should have significant impact on the technologies and systems that use these materials. In this article, some fundamental aspects of alkoxide-based, sol-gel processes and thermochemical bases for process-induced structural variates are discussed. 相似文献
24.
25.
Novel self activated green phosphors; K2ZnV2O7 (KZV) and K2MgV2O7 (KMV) have been prepared and characterized in details. Both KZV and KMV were prepared by solid state reaction and systematically characterized by a number of techniques like X-ray diffraction (XRD), Fourier transformed Infrared (FTIR), Raman spectroscopy, Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), diffuse reflectance spectroscopy (DRS) and time resolved photoluminescence spectroscopy (TRPLS). XRD studies confirm tetragonal melilite type layered phase for both of them. The presence of pyrovanadate group in both is supported by FTIR and Raman spectroscopic investigations. Raman bands of KMV are blue shifted w.r.t to KZV which may be due to shorter bond lengths of MgO compared to ZnO and lower atomic weight of magnesium compared to zinc. DRS measurements indicated the optical band gap of KMV and KZV are 3.14 and 3.12 eV, respectively. Optical measurements on these samples show the emission of green color on ultra violet light irradiation. The origin of such emission is attributed to electronic transition (charge transfer) from filled 2p orbital of oxygen ion (O2−) to vacant 3d orbital of vanadium ion (V5+). In KZV there are dual emission band (PL1 and PL2) which are respectively attributed to 3T2 → 1A1 and 3T1 → 1A1transition, and the emission zone varies slightly compared to KMV. KZV emits bluish green (cool green) where KMV emits in yellowish green (warm green) region. This is indeed an important step towards realization of cost effective rare earth free luminescence material. It is also oberved that PL intensity of KZV is very high compared to KMV which is supported by the lifetime measurements. 相似文献
26.
Summary The effect of weight loss on the dimensional stability of some addition-polysiloxanes used as impression materials in dentistry
is studied. We show that polymerization is not the only factor affecting the shrinkage of these materials. An explanation
for the time-dependent weight function is given. 相似文献
27.
泡沫塑料吸附—石墨炉原子吸收光谱法测定地质物料中痕量铊 总被引:10,自引:0,他引:10
本文研制定了一种泡沫塑料吸附-石墨炉原子吸收光谱法测定地质物料中痕量铊的分析,在所先定的实验条件下,方法检出限为0.05μg/g、样准曲线范围为10-300ng/mL,Tl含量水平为0.71μg/g时的测定精度为6.0%,方法回收率99.0%-100.0%。经标样及大量样品分析验证,分析方法准确可靠。 相似文献
28.
Rudolf Merten 《Angewandte Chemie (International ed. in English)》1971,10(5):294-301
Investigations on space flight and rockets carried out in particular in the United States have aroused great interest in plastics with enhanced thermal stability. It has become possible to pass far beyond the expected limits of thermal stability with organic plastics, and to synthesize plastics and polymers that can be used at temperatures between about 200 and about 500 °C, a range that formerly appeared to be the exclusive province of inorganic materials. 相似文献
29.
The influence exerted by the specimen proportions on the measured performance of angle-ply [+45°/–45°]s composite laminates is studied. Three kinds of specimens are considered, having different length-to-width ratios, made with glass/epoxy unidirectional or fabric laminae. The static tensile characteristics are measured by means of load cells, electric strain gauges and through the Moiré fringes method. The strain fields are analysed and the effects of stress concentration at the laminate-free edges are evaluated, as well as their influence on the strain distribution and the measured strength and stiffness. The results are summarized as diagrams of ultimate load and elastic modulus versus length-to-width ratio of the different specimens investigated. These diagrams allow the designer to evaluate the influence exerted by specimen proportions on the measured performance, as well as to compare characteristics which are heterogeneous, as obtained with different kinds of specimen. 相似文献
30.
Nanoscopic scale studies of LiFePO4 as cathode material in lithium-ion batteries for HEV application
We present a review of the structural properties of LiFePO4. Depending on the mode of preparation, different impurities can poison this material. These impurities are identified and
a quantitative estimate of their concentrations is deduced from the combination of X-ray diffraction analysis, Fourier transform
infrared spectroscopy, Raman spectroscopy, and magnetic measurements. An optimized preparation provides samples with carbon-coated
particles free of any impurity phase, insuring structural stability and electrochemical performance that justify the use of
this material as a cathode element a new generation of lithium secondary batteries. 相似文献