聚乙烯吡咯烷酮分子量对LiFePO4/C形貌及电化学性能的影响

以价廉、低毒的无机盐为原料、去离子水为溶剂,通过简易可行的络合溶胶-凝胶法合成了LiFePO4/C复合正极材料.利用XRD、SEM、EIS及恒流充放电测试考察了聚乙烯吡咯烷酮(PVP)分子量对试样的形貌及电化学性能的影响.结果表明,以PVP-k30为表面活性剂所合成的试样颗粒均匀细小、形貌较规则且单分散性良好;该试样具有优良的电化学性能,0.1C的放电比容量为155.7 mAh/g,3C倍率下放电比容量依然能保持112.4 mAh/g,明显优于其它分子量PVP所制备的试样.     

真空退火处理对纳米氮化硅电子自旋共振谱的影响

用微米级SiO2、Si和碳黑混合粉末为原料, 以氮气为反应气,采用碳热还原法合成了氮化硅纳米粉体.测量了300～1273K退火温度下纳米氮化硅的电子自旋共振(ESR)谱,研究了测量温度、纳米氮化硅退火温度对ESR谱线型、g因子、线宽的影响.结果证实退火影响纳米氮化硅的磁性.     

溶胶-凝胶软模板法合成锂钛离子筛

以乙酸锂和钛酸丁酯为锂源和钛源,十六烷基三甲基溴化铵(CTAB)为软模板,采用溶胶-凝胶法,通过焙烧得到添加CTAB的锂钛化合物(Li₄Ti₅O₁₂),经过盐酸酸洗,制备出锂钛离子筛(H₄Ti₅O₁₂, HTO)。经过热重分析(TG-DTG)、X射线(XRD)、扫描电镜(SEM)、接触角及性能测试,考察了锂钛离子筛的晶相、形貌及时间对吸附容量的影响。对比CTAB的加入量,0.1 g的CTAB的离子筛前驱体杂质更少,晶相比较纯。HTO准二级动力学相关系数R²(0.997 24)大于准一级动力学相关系数R²(0.984 35),该吸附过程符合化学吸附。HTO在Li⁺溶液中24 h的吸附容量达到24.44 mg/g,经过8次吸附脱附后,吸附容量仍保持在23.68 mg/g,仅降低3.1%。因此,HTO有良好的循环吸附性能和稳定性,具有很广阔的市场前景。     

正常人与肝气郁结证人指甲中无机元素的比较分析

为探讨正常人与肝气郁结证指甲中特殊无机元素谱的差别,进而为人指甲的临床诊断及药效物质基础的探讨提供实验依据,采用扫描电子探针法测定了正常人与肝气郁结证患者指甲中炭化灰中无机元素。结果表明,正常人指甲炭化灰无机元素特征谱,有Ca和S两个呈正态分布趋势的特征性高峰;肝气郁结证指甲炭化无机元素特征谱只有一个Ca呈正态分布趋势的高峰。提示正常人与肝气郁结证具有不同的无机元素谱,肝气郁结证与体内无机元素发生代谢紊乱有关。     

An Unusual Organometallic Supramolecule Composed of Chiral Dirhodium Units and Sulfato Bridging Ligands

A chiral supramolecular compound (H3O){[cis-Rh2((C6H5)2P(C6H4))2(SO4)- (DMF)]2(μ- OC2H5)}·6C2H5OH (1) has been synthesized and characterized by X-ray single-crystal analysis. Compound 1 crystallizes in monoclinic, space group C2/c with a = 26.752(3), b = 13.5868(16), c = 26.611(3) , β = 103.891(2)°, V = 9389.5(19) 3, Z = 4, C92H114N2O18P4Rh4, Mr = 2135.49, Dc = 1.511 g/cm3, F(000) = 4384 and μ(MoKα) = 0.870 mm-1. The final R = 0.0441 and wR = 0.1186 for 8283 observed reflections with I > 2σ(I) and R = 0.0567 and wR = 0.1290 for all data. The structure of the compound is unique. It contains two inherent chiral {cis-Rh2[(C6H5)2P(C6H4)]2}2+ units which are connected not only in the equatorial positions by two sulfato ligands, but also in two of their axial positions by a μ2 ethoxide anion. The remaining axial positions of Rh24+ units in 1 are occupied by the DMF molecules. The sulfato ligands act as μ4 tridentate bridges to connect the Rh24+ units. The Rh-Rh metal-metal bond distances are comparable to those in analogous dirhodium compounds.     

Elastic behavior of comb-like polymer chains

<正>Three-dimensional Monte Carlo simulations of comb-like polymer chains with various backbone lengths N_b,arm lengths N_a and arm densities m are carried out to study the elastic behavior of comb-like polymer chains.The radius of gyration,the shape factors and bond length in different cases during elastic process are calculated,and it is found that the comb-like polymer molecules with longer backbone or shorter arm are more close to linear chains.But the arm density m affects the chain conformation non-monotonously.Some thermodynamic properties are also studied.Average Helmholtz free energy and elastic force f all increase with elongation ratioλfor all chains.     

Study of RPC gas composition using Daya Bay RPCs

This study uses Daya Bay RPCs operating in streamer mode to investigate gas mixtures of at least 50% argon, at most 6% isobutane, and with small amounts of SF6. Isobutane is reduced to 2% without degradation of performance, and SF6 reduces the noise rate and current, as well as the signal size. This study provides quantitative relationships between basic RPC operating parameters and various gas compositions.     

BESⅢ RPC宇宙线测试系统

北京谱仪(BESⅢ)采用阻性板室(Resistive Plate Chambers)作为其muon探测器, 总使用面积达1200m². 为保证探测器的质量, 每一块阻性板室都要求通过宇宙线测试. 宇宙线测试系统使用3个流光管室作为其触发和寻迹系统, 其空间分辨可达2—3mm, 覆盖面积约4m², 测试系统可同时测量8块RPCs. 最后, 还报道了RPC的初次测试结果.     

基于总体最小二乘算法的平稳声信号二阶盲分离方法

利用声源信号相互独立的已知条件,提出分离平稳声信号的总体最小二乘二阶盲分离算法,该算法在联合近似对角化相关函数矩阵的约束下估计分离矩阵,在同时考虑估计矩阵与观测信号误差的情况下给出修正模型,在修正模型总体误差最小时分离源信号。提出的算法具有无需选择非线性函数,不存在收敛到局部最小值与计算速度快的特点,分离的声源信号具有较小的失真。半消音室电机噪声分离实验验证了上述算法的有效性。     

简易溶液法快速制备Cu2ZnSnS4纳米晶工艺研究

采用一种简易溶液法成功快速制备出低成本薄膜太阳能电池用Cu2ZnSnS4(CZTS)纳米晶.探讨合成温度和时间对CZTS纳米晶的结构、形貌、元素比例及光学特性的影响,实现可控的CZTS纳米晶合成.以上特性分别采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能量色散谱仪(EDX)、紫外-可见光谱仪(UV-vis)进行表征.结果表明:温度为250℃,时间为1h时可获得锌黄锡矿结构,团聚颗粒约为200～500 nm,化学计量比约为Cu∶ Zn∶ Sn∶S=2.17∶ 1∶1.23∶4.69,禁带宽度为1.5 eV的纳米晶,适合印刷法制备CZTS薄膜太阳能电池吸收层.