Preparation of V-LiFePO4 cathode material for Li-ion batteries

The preparation of vanadium-modified olivine LiFePO₄ was attempted using vanadium-modified FePO₄ precursor which was synthesized by controlled crystallization. The structure and electrochemical behavior of V-LiFePO₄ with different vanadium contents were investigated. The electrochemical behavior of V-LiFePO₄ materials at high rate and low temperature was compared with that of the LiFePO₄ material. Incorporation of vanadium improved the electrochemical performance of LiFePO₄. The investigation showed that the 3%V-modified LiFePO₄ presented the best electrochemical performance.     

Electrochemical characteristics of sulfur composite cathode for reversible lithium storage

The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated. The sulfur composites showed novel electrochemical characteristics as well as high specific capacity and good cycleability. The sulfur composite presented the average discharge voltage of 1.9 V, which was just the half of conventional LiCoO₂ cathode materials, indicating that the double cells in series presented the same working voltage as conventional LiCoO₂ cells and meaning that the sulfur composite cells will have good interchangeability with conventional LiCoO₂ cells. The overcharge test showed that the sulfur composite cell cannot be charged over 5.0 V, indicating that the sulfur composite cell presented the intrinsic safety for overcharge. Overcharge can cause serious problems for the conventional Li ion cells. The overcharge test also showed that the sulfur composite cell was destroyed when the cell was charged over 4.0 V, resulting in that the cell cannot normally be discharged again. It is found, however, that the sulfur composite cell can be discharged again at very low current density of a 0.002-C rate after the cell was overcharged. Being much safer than lithium metal anode, the graphite anode was used to fabricate sulfur composite/graphite lithium ion cells with a prelithiated sulfur composite cathode, which was produced by electrochemical lithiation. The charge/discharge and cycling characteristics of the sulfur composite/graphite cell was investigated. The result showed that the sulfur composite/graphite cells can be normally cycled and showed the different voltages from that of the cell with the lithium metal anode. This paves the effective way to fabricate safer sulfur composite/graphite lithium ion cells.     

ZrO2 coating of LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

ZrO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ materials were prepared by hydroxide precipitation. The structure and electrochemical properties of the ZrO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ were investigated using X-ray diffraction, scanning electron microscope, and charge–discharge tests, indicating that the lattice structure of LiNi_1/3Co_1/3Mn_1/3O₂ were unchanged after the coating but the cycling stability was improved. As the coating amount increased from 0.0 to 0.5 mol.%, the initial capacity of the coated LiNi_1/3Co_1/3Mn_1/3O₂ decreased slightly; however, the cycling stability increased remarkably over the cut-off voltages of 2.5~4.3 V and the capacity retention reached 99.5% after 30 cycles at the coating amount of 0.5 mol.%. ZrO₂ coating also improved the cycling stability of LiNi_1/3Co_1/3Mn_1/3O₂ over wider cut-off voltage of 2.5~4.6 V.     

超高效液相色谱-电喷雾串联质谱法测定生活饮用水中49种药物及5种代谢物

建立了超高效液相色谱-电喷雾串联质谱(UPLC-ESI MS/MS)分析生活饮用水中54种药物的方法。采用HLB固相萃取柱对水样中的目标化合物进行富集净化,以5 mL甲醇洗脱;洗脱液用氮气吹至近干,用0.4 mL 0.1%甲酸水溶液定容,上机分析;ACQUITY UPLC^TMBEH C₁₈柱用作色谱分离,以0.1%甲酸水溶液-甲醇为流动相进行梯度洗脱;多反应监测(MRM)模式进行检测;目标药物使用基质外标法定量。54种药物在自备井水、市政末梢水和地表水中的加标回收率分别为58.7%~104.4%、53.1%~109.5%和50.7%~118.8%,相对标准偏差(n=6)分别为0.3%~12.8%、1.0%~15.5%和0.4%~19.3%;方法定量限为0.002~5.000 ng/L。将建立的方法应用于北京部分自备井水、市政末梢水和地表水样品的分析,结果在自备井水样中检出26种药物。     

波纹通道换热特性的三维数值研究和场协同分析

应用计算流体力学CFD(Computational Fluid Dynamics)方法,对顺人字组合及软硬板组合波纹通道内三维稳态湍流流场进行了数值模拟,定量计算了不同流动速度和不同结构参数下波纹通道的传热因子j和摩擦系数f,得到了波纹通道换热与流动阻力随波纹夹角β及波纹密度λ/h的变化规律,进而对波纹通道进行了整体性能评价,并从场协同理论角度,分析了波纹通道强化换热的机理。     

Designing cancer nanodrugs that are highly loaded,pH-responsive,photothermal, and possess a favored morphology: A hierarchical assembly of DOX and layer-by-layer modified rGO

A facile strategy to construct the multifunctional rGO-DOX nanodrugs by hydrogen bonding was reported. The nanodrugs were highly loaded, pH-responsive, photothermal, and possess a favored morphology.     

Nonvolatile two-color holographic recording in near-stoichiometric lithium niobate crystals gated by incoherent ultraviolet light

Nonvolatile two-color holographic recording gated by incoherent ultraviolet （UV） light centered at 365 nm is investigated in near-stoichiometric lithium niobate crystals. The influence of thermal treatment on the two-color recording is studied. The results show that thermal reduction tends to improve the two-color recording performance, whereas thermal oxidation degrades the two-color recording. With an incoherent 0.2-W/cm2 UV gating light and a 0.25-W/cm2 semiconductor recording laser at 780 nm, a two-color recording sensitivity of 4 × 10^-3 cm/J and a recording dynamic range characterized by M/# of 0.12 are achieved in a 2.2-mm thermally reduced near-stoichiometric lithium niobate crystal. We attribute the improvement to the prolonged lifetime of small polarons and the increased absorption at the gating wavelength due to thermal reduction.     

约束阻尼层合板的稳态响应

基于Reddy分层理论推导出约束阻尼层合板的稳态振动方程,得到了约束阻尼层合板的振动频率和损耗因子;分别分析了约束阻尼层合板的粘弹性夹层厚度、模量对固有频率和损耗因子的影响;得到了稳态振动时振幅和频率曲线以及横向应力与面内应力。数值计算结果表明所采用的算法是可靠的。     

A novel synthesis of acrylic acid containing polymers

A novel synthesis of linear acrylic acid containing polymers, poly(styrene-co-acrylic acid) and poly(acrylic acid), was accomplished through hydrolysis of the respective parent polymers, i.e. poly(styrene-co-methyl acrylate) and poly(methyl acrylate), with trimethylsilyl iodide under mild conditions. Combination of ¹H NMR, ¹³C NMR, FTIR, DSC and chemical titration confirms that the conversion from methoxycarbonyl to carboxyl is almost complete. This method is further successfully applied to synthesize poly-(ethyl methacrylate-co-acrylic acid) through selective hydrolysis of the methyl acrylate units in poly(ethyl methacrylate-co-methyl acrylate).     

论可微函数的共单调逼近和共凸逼近

对有限区间上可微函数借助于代数多项式的共单调逼近和共凸逼近的逼近度估计建立了更为精确的Jackson型不等式,扩充和改进了近期的一些结果。