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61.
文章主要介绍了运用回归分析方法建立氢化锂车削表面粗糙度预测模型的方法。通过所建立的粗糙度预测模型,研究了车削过程中切削速度、进给量、切削深度对表面粗糙度的影响。经加工试验证明了该表面粗糙度预测模型的有效性,从而实现加工前在确定切削条件下预测和控制表面粗糙度的目的。 相似文献
62.
基于SOC的串联锂离子电池组均衡策略研究 总被引:1,自引:0,他引:1
由于一致性问题的存在,成组电池在可用容量、使用寿命等方面远不及单体电池,电池组的均衡管理对电池的成组使用者有着重要的实际意义.论文就针对锂离子串联电池组的均衡技术进行了研究,首先介绍了电池组一致性问题产生的原因,指出均衡管理的重要意义,分析了锂离子电池组SOC的一致性和基于SOC的均衡策略,详细阐述了基于SOC的均衡技术实现,最终搭建实验平台进行测试,验证了所使用的均衡策略和硬件电路的有效性. 相似文献
63.
《材料科学技术学报》2019,35(9):1977-1981
Titanium oxide (TiO2), with excellent cycling stability and low volume expansion, is a promising anode material for lithium-ion battery (LIB), which suffers from low electrical conductivity and poor rate capability. Combining nano-sized TiO2 with conductive materials is proved an efficient method to improve its electrochemical properties. Here, rutile TiO2/carbon nanosheet was obtained by calcinating MAX (Ti3AlC2) and Na2CO3 together and water-bathing with HCl. The lamellar carbon atoms in MAX are converted to 2D carbon nanosheets with urchin-like rutile TiO2 anchored on. The unique architecture can offer plentiful active sites, shorten the ion diffusion distance and improve the conductivity. The composite exhibits a high reversible capacity of 247 mA h g−1, excellent rate performance (38 mA h g−1 at 50 C) and stable cycling performance (0.014% decay per cycle during 2000 cycles) for lithium storage. 相似文献
64.
Potentiometric cell, Au/LiCoO2 5 m/o Co3O4/Li2.88PO3.73N0.14/Li2CO3/Au, has been fabricated and investigated for monitoring CO2 gas. A LiCoO2–Co3O4 mixture was used as the solid-state reference electrode instead of a reference gas. The idea is to keep the lithium activity constant on the reference side using thermodynamic equilibrium at a given temperature. The thermodynamic stability of the reference electrode was studied from the phase stability diagram of Li–Co–C–O system. The Gibb’s free energy of formation of LiCoO2 was estimated at 500°C from the measured value of the cell emf. The sensors showed good reversibility and fast response toward changing CO2 concentrations from 200 to 3000 ppm. The emf values were found to follow a logarithmic Nernstian behavior in the 400–500°C temperature range. CH4 gas did not show any interference effect. Humidity and CO gas decreased the emf values of the sensor slightly. NO and NO2 gases affect this sensor significantly at low temperatures. However, increased operating temperature seems to reduce the interference. 相似文献
65.
将嗜热菌Geobacillus Kaustophilus HTA426中的磷酸三酯酶基因转入毕赤酵母GS115中,整合到染色体DNA基因组上,并进行诱导表达.SDS-PAGE和Western-blot试验结果显示,重组蛋白是一个分子量约为50KD的磷酸三酯酶二聚体.酶活检测证明重组蛋白具有较高的磷酸三酯酶活性,其最适温度为70℃,最适pH为10.0. 相似文献
66.
Nanosized α-Fe2O3 (ca. 50 nm) and Li-Fe composite oxides (ca. 29 nm) powders were synthesized via gel polymer route. The gels were obtained with thermal polymerization of acrylic acid solutions of iron and lithium nitrates. The calcination of these gels at temperatures from 300 °C to 500 °C results in α-Fe2O3 from Fe(NO3)3 precursor and Li-Fe composite oxides Li2O-Fe3O4-LiFeO2 from a mixed precursors of Fe(NO3)3 and LiNO3. Thermal gravimetric analysis, X-ray diffraction and transmission electron microscopy were used to investigate the precursors and products. The electrochemical performance of the Fe-based oxides was also evaluated. After 200 cycles, their capacity can be as high as 1300 mAh/g for α-Fe2O3 and 1400 mAh/g for Li-Fe oxide while the initial capacity loss is as low as 21.8%. The Li-Fe oxide electrodes exhibit better capacity retention than the α-Fe2O3 electrodes. They are interesting negative electrodes for high energy density lithium-ion batteries. 相似文献
67.
Compounds of the formula LiCo1−yCryO2 (0.0≤y≤0.20 and y=1.0) have been synthesized by high temperature solid-state reaction and were characterized by XRD and FT-IR. Hexagonal a and c lattice parameters increase with increasing y as expected from ionic size effects. Cyclic voltammograms reveal that the phase transformation occurring at x=0.5 in Li1−x(Co1−yCry)O2 is suppressed for y=0.05 and 0.10. Low-current (0.01 C; 1 C=140 mA g−1) galvanostatic charging curves show that the deintercalation voltage for y=0.05 and 0.10 decrease for a given x as compared to LiCoO2. Galvanostatic charge-discharge cycling of the Li(Co1−yCry)O2 cathodes at 0.14 C and 2.7-4.3 V (vs. Li) show that increasing amount of chromium content in the LiCoO2 lattice drastically reduces the amount of Li that can be reversibly cycled. Ex-situ XRD of the cycled cathodes show that slight cation-mixing occurs in the layered structure for y=0.05 and 0.10 and could be the reason for their poor electrochemical performance. Reversible Li intercalation/deintercalation is not possible in LiCrO2 in the voltage range 2.7-4.3 V. 相似文献
68.
Lithium niobate thin films have been deposited on Pt/Ti/SiO2/Si(100) substrates by Pechini method. Characterization of the initial precursor solutions containing citric acid (CA), niobium and lithium ions has been performed by Fourier transform infrared spectroscopy, Raman spectroscopy and carbon nuclear magnetic resonance spectroscopy. The results indicate that citric acid coordinate to niobium ions to form a niobium-CA complex through one terminal carboxyl group, the hydroxyl group and the central carboxyl group as a tridentate ligand. The thermal decomposition of the Li-Nb precursors gel powder has been studied and the results show that LiNbO3 phase is formed directly from the thermal decomposition of the precursor gel. By heat-treatment at 600 °C for 2 h, polycrystalline LiNbO3 thin films with smooth and crack-free surface could be achieved. 相似文献
69.
Hydrogen storage: The major technological barrier to the development of hydrogen fuel cell cars 总被引:2,自引:0,他引:2
In this paper, we review the current technology for the storage of hydrogen on board a fuel cell-propelled vehicle. Having outlined the technical specifications necessary to match the performance of hydrocarbon. fue1, we first outline the inherent difficulties with gas pressure and liquid hydrogen storage. We then outline the history of transition metal hydride storage, leading to the development of metal hydride batteries. A viable system, however, must involve lighter elements and be vacuum-tight. The first new system to get serious consideration is titanium-activated sodium alanate, followed by the lithium amide and borohydride systems that potentially overcome several of the disadvantages of alanates. Borohydrides can alternatively produce hydrogen by reaction with water in the presence of a catalyst but the product would have to be recycled via a chemical plant. Finally various possible ways of making magnesium hydride decompose and reform more readily are discussed. The alternative to lighter hydrides is the development of physisorption of molecular hydrogen on high surface area materials such as carbons, metal oxide frameworks, zeolites. Here the problem is that the surface binding energy is too low to work at anything above liquid nitrogen temperature. Recent investigations of the interaction mechanism are discussed which show that systems with stronger interactions will inevitably require a surface interaction that increases the molecular hydrogen-hydrogen distance. 相似文献
70.