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1.
To improve the cycle performance of eco-friendly and cost-effective spinel LiMN2O4 as the Li secondary batteries, the Th-doped LiThxMn1-xO4 spinel powers were synthesized by solid-state method. The starting materials, Li2CO3,MnO2 and Th(NO3)4·4H2O, were mixed uniformly using a traditional ball milling, which resulted in a uniform particle size distribution in the mixed powers. Tests of X-ray diffraction, SEM, impedance spectra and charge-discharge were carried out for LiThxMn1-xO4 cathode materials. Results show that the synthesized LiTh0.01Mn1.99O4 material exhibits standard spinel structure, regular particle morphology and excellent property of charge-discharge for big current. The capacity retention of the material modified by doping Th is more than 85.1% of the first discharge specific capacity of 111.5 mAh·g -1 after 20 cycles at the current rate 1C, while the pristine LiMN2O4 is only 57% of the first discharge specific capacity of 110.2 mAh·g-1 after the same cycles at the same current rate. 相似文献
2.
在50℃下,以异丙醇为反应溶剂,研究了N-甲基咪唑与卤代烷的反应动力学,得到反应总级数为二级,分反应级数各为一级;测得N-甲基咪唑与溴丁烷在50℃、55℃和60℃时的反应速率常数分别为0.092 4 L.mol-1.h-1、0.169 2 L.mol-1.h-1和0.322 8 L.mol-1.h-1,进而计算出反应的活化能为2.18×105J.mol-1;同时,测得N-甲基咪唑与溴乙烷、溴丁烷的反应速率常数分别为0.292 6 L.mol-1.h-1和0.169 2 L.mol-1.h-1,说明溴乙烷与N-甲基咪唑的季铵化较溴丁烷易于进行。 相似文献
3.
采用熔融共混法制备了纳米锡酸锌/丙烯腈-丁二烯-苯乙烯共聚物(ABS)/聚氯乙烯(PVC)复合材料。并对复合材料的冲击强度、阻燃性能进行了测试。结果表明,纳米锡酸锌不但可以提高复合材料的缺口冲击强度,还可以改善复合材料的抑烟阻燃性能。特别是当纳米锡酸锌添加量为6份时,复合材料的阻燃抑烟性能最佳。与未添加纳米填料时相比,纳米锡酸锌/ABS/PVC复合材料的缺口冲击强度达到69.93 kJ/m~2,提高幅度达49.71%。扫描电镜(SEM)分析表明,当纳米锡酸锌在6份时,其在复合材料中呈纳米级分散,且与塑料基体结合良好。 相似文献
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Hengrui Wang Yue Jiang Zhewen Ma Yongqian Shi Yanjun Zhu Ruizhe Huang Yuezhan Feng Zubin Wang Min Hong Jiefeng Gao Long-Cheng Tang Pingan Song 《Advanced functional materials》2023,33(49):2306884
MXene aerogels have shown great potential for many important functional applications, in particular electromagnetic interference (EMI) shielding. However, it has been a grand challenge to create mechanically hyperelastic, air-stable, and durable MXene aerogels for enabling effective EMI protection at low concentrations due to the difficulties in achieving tailorable porous structures, excellent mechanical elasticity, and desired antioxidation capabilities of MXene in air. Here, a facile strategy for fabricating MXene composite aerogels by co-assembling MXene and cellulose nanofibers during freeze-drying followed by surface encapsulation with fire-retardant thermoplastic polyurethane (TPU) is reported. Because of the maximum utilization of pore structures of MXene, and conductive loss enhanced by multiple internal reflections, as-prepared aerogel with 3.14 wt% of MXene exhibits an exceptionally high EMI shielding effectiveness of 93.5 dB, and an ultra-high MXene utilization efficiency of 2977.71 dB g g−1, tripling the values in previous works. Owing to the presence of multiple hydrogen bonding and the TPU elastomer, the aerogel exhibits a hyperelastic feature with additional strength, excellent stability, superior durability, and high fire safety. This study provides a facile strategy for creating multifunctional aerogels with great potential for applications in EMI protection, wearable devices, thermal management, pressure sensing, and intelligent fire monitoring. 相似文献
7.
《材料科学技术学报》2019,35(10):2345-2356
The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6SO4 are identified as the main stable composition and exhibit an increasing relative amount; while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops. 相似文献
8.
《International Journal of Hydrogen Energy》2019,44(31):16110-16119
The activity of transition metal dichalcogenides (TMD) toward hydrogen evolution reaction (HER) derives from the active sites at the edges, but the basal surface still remain catalytic insert. Herein, ultrathin MoSSe alloy nanosheets array on multiwalled carbon nanotubes (MWCNTs) to form a core shell structure via a simple solvothermal process. These three-dimensional (3D) MoSSe hybrids show a high activity in hydrogen evolution reaction (HER) with a small Tafel slope of 38 mV dec−1 and a low overpotential of 102 mV at 10 mA cm−2. In addition, their HER activity remains remarkably stable without significant decay after 100 h polarization. Such superior catalytic HER activity springs from the 3D hierarchical heterostructure, which is abundant of catalytic edge sites, and the alloy effect between S and Se, which will create huge defects and strain to form vacancy sites on the basal plane. This strategy may open a new avenue toward the development of nonprecious high-performance HER catalysts. 相似文献
9.
《Carbon》2014
The characteristics of network formation of multiwall carbon nanotubes (MWCNTs) inside ethylene–octene copolymer (EOC) melts under an alternating current (AC) electric field and the resulting electrical conductivity improvements are studied by combining dynamic and steady state resistivity measurements. Fine MWCNT dispersion during melt compounding of the samples is accomplished by means of a novel non-specific, non-covalent functionalization method. It is found that the electrified composite films exhibit nanotube assembly into columnar structures parallel to the electric field, accompanied by dramatic increases in electrical conductivity up to eight orders of magnitude. Experimentally acquired resistivity data are used to derive correlations between the characteristic insulator-to-conductor transition times of the composites and process parameters, such as electric field strength (E), polymer viscosity (η) and nanotube volume fraction (ϕ). Finally, a criterion for the selection of (η, E, C) conditions that enable MWCNT assembly under an electric field controlled regime (i.e., minimal Brownian motion-driven aggregation effects) is developed. The correlations presented herein not only provide insights in the MWCNT assembly process, but can also guide the experimental design in future studies on electrified composites or assist in the selection of process parameters in composites manufacturing. 相似文献
10.
S. Kaprzyk 《Computer Physics Communications》2012,183(1):20-25
We present the systematic treatment of multiple integrals over a simplex of the dimensionality d (d-simplex). The integrand is an analytical function in a suitable domain, and the linear form was employed as an argument. Using the elements obtained from the values of the integrand at the vertices of the d-simplex, integral can be evaluated analytically and expressed as the quotient of two determinants. Potential applications of the results described in the present study include numerical computations of Green?s function (GF), and the response of quantum systems in terms of complex susceptibilities in multidimensional space. 相似文献