An electrochemical impedance spectroscopic study of the electronic and ionic transport properties of LiCoO2 cathode

The storage behavior and process of the first delithiation-lithiation of LiCoO2 cathode were investigated by electrochemical impedance spectroscopy(EIS). The electronic and ionic transport properties of LiCoO2 cathode along with variation of electrode potential were obtained in 1 mol·L?1 LiPF6-EC:DMC:DEC electrolyte solution. It was found that after 9 h storage of the LiCoO2 cathode in electrolyte solu-tions,a new arc appears in the medium frequency range in Nyquist plots of EIS,which increases with increasing the storage time. In the charge/discharge processes,the diameter of the new arc is reversi-bly changed with electrode potential. Such variation coincides well with the electrode potential de-pendence of electronic conductivity of the LiCoO2. Thus this new EIS feature is attributed to the change of electronic conductivity of LixCoO2 during storage of the LiCoO2 cathode in electrolyte solutions,as well as in processes of intercalation-deintercalationtion of lithium ions. It has been revealed that the reversible increase and decrease of the resistance of SEI film in charge-discharge processes can be also ascribed to the variation of electronic conductance of active materials of the LiCoO2 cathode.     

Low-field positive and high-field negative magnetoresistances in multiphase Fe-oxide thin films at room temperature

Multiphase Fe-oxide thin films are fabricated on glass substrates by a facing-target sputtering tech- nique. X-ray diffraction and X-ray photoelectron spectroscopy reveal that Fe, Fe3BO4, γ -Fe2BO3B and FeO coexist in the films. High resolution transmission electron microscopy shows the well-defined colum- nar grain structure with the unoxidized Fe as the core and iron-oxide as the shell. The low-field positive and high-field negative magnetoresistances coexist in such a system at room temperature, which can be explained by considering a shell/core model. Nonlinear current-voltage curve and photovoltaic effect further confirm the tunneling-type conduction.     

SiC薄膜的制备及其光敏特性

采用热丝化学气相沉积(HFCVD)方法,以甲烷、硅烷和氢气为反应气体在单晶硅衬底上沉积碳化硅(SiC)薄膜材料.通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)对SiC薄膜的晶体结构进行测试分析.利用原子力显微镜(AFM)对SiC薄膜的表面形貌进行分析.对该薄膜在室温和较高温度(410℃)下进行光敏特性测试,结果表明:该薄膜为SiC薄膜且对不同波长、不同功率的光有一定的敏感特性,较高温度下其敏感特性和室温下测试的结果大体一致,在高温光敏器件领域具有很大的应用潜力.     

铕离子掺杂普鲁士蓝复合汞膜电极上替硝唑的方波伏安法测定

采用电化学沉积法制备了新型铕离子掺杂普鲁士蓝复合汞膜电极(PB-Eu composite mercury fil melectrode),建立了在该电极上应用方波伏安法测定实际样品中替硝唑(Tinidazole,简称TNZ)含量的方法.结果表明,在BR(pH=6.0)缓冲溶液中,TNZ在-0.558 V(vs.SCE)产生一个清晰的还原峰,且具有明显的吸附波特性.在最佳实验条件,恒电位富集1.5 min时,其还原峰电流与TNZ的浓度在2.5×10-6~5.0×10-4mol/L(r=0.999 2)和2.5×10-8~7.5×10-7mol/L(r=0.999 4)两段浓度区间内有良好的线性关系,最低检测下限为2.0×10-9mol/L(S/N=3),相对标准偏差为2.2%(n=10).该法用于片剂和注射液中替硝唑含量测定的稳定性和重现性好,线性范围较宽.     

光存储中固体浸没透镜的透射率计算

从矢量衍射理论出发,将入射到固体浸没透镜(SIL)底面的光场看成角谱积分形式,并将角谱分量分解为TE波和TM波,从而用隧道薄膜的特性矩阵方法求出相应的反射角谱分量。在稳相近似下得到入射到SIL底面以及反射的光能积分表达式,从而求出SIL的透过率。据此计算分析了SIL的透射率与薄膜厚度的关系。结果表明:随着厚度的增加,SIL透射率开始有一个很明显下降阶段,然后趋于稳定;而且超半球齐明SIL的透射率一般优于半球同心SIL的透射率。     

顶板式低温辐射电热膜在住宅取暖应用中的利与弊

介绍了低温辐射电热膜供暖系统的构成和工作原理,对电热膜供暖系统进行了经济分析,讨论了电热膜供暖系统在住宅取暖应用中的利与弊。     

铝诱导晶化非晶硅薄膜研究

应用晶化非晶硅（a—Si）薄膜铝诱导方法，采用X射线衍射（X-ray diffraction，XRD）、光学显微镜（Optical Microscopy，OM）和原子力显微镜（Atomic Force Microscopy，AFM）等测试手段，研究了退火条件对样品晶化的影响．结果表明，样品在300℃下退火后仍为非晶态；退火温度为400℃时，样品开始晶化．随着退火时间的增加，薄膜晶化程度越来越高，晶粒越来越大，同时薄膜表面粗糙度增加．     

脉冲激光沉积类金刚石薄膜的厚度均匀性建模

在脉冲激光沉积类金刚石薄膜过程中,针对薄膜均匀性差的问题,提出偏轴沉积、脉冲激光扫描沉积、双光束沉积和多光束沉积等模式来改善薄膜的均匀性。初步建立了脉冲激光沉积类金刚石薄膜厚度均匀性模型,并分别进行了薄膜厚度分布的模拟,在模拟过程中,强调了在不影响薄膜性能的基础上改善薄膜均匀性,并讨论了沉积模式对薄膜颗粒物问题的影响。结果表明,采用多光束沉积薄膜,厚度均匀性得到极大改善,而且颗粒物问题也得到了改善。最后提出模型改良意见。     

MgB_2超导材料的薄膜制备及其超导器件的实现

报道了采用电子束蒸发技术实现MgB2薄膜制备的实验工作。通过蒸镀B膜和Mg/B多层膜两种前驱体,分别经高温区(~900℃)和中温区(~700℃)退火处理后成功获得了高质量的MgB2薄膜样品。对样品的超导性能、晶体结构和表面形貌进行了详细的测量和表征,并对两类样品性质上所表现出的差异进行了分析。此外,还报道了在薄膜制备基础上利用微加工技术实现的超导微波谐振器的结果。     

Influences of Copolymer Composition upon the Behaviors of Poly（vinyl acetate-co-acrylamide） Sizing Agents

A series of poly(vinyl acetate-co-acrylamide)copolymers with different mole ratios of vinyl acetateto acrylamide units were synthesized by emulsionpolymerization for investigating the influences of copolymercompostion upon the performance such as apparentviscosity, film behaviors, and adhesion capacity to fibers forwarp sizing operation. The mole ratios of vinyl acetate toacrylamide were varied from 0 to 4. By using animpregnated roving method, the adhesion was evaluated interms of the maximal strength and work to break of aslightly sized roving. The film behaviors included breakingstrength, breaking elongation, solution time and hygroscopiccapacity. It was found that the viscosity, adhesioncapability, glass transition temperature and film behaviorsof the copolymeric sizing agent strongly depended on themole ratio. Excessively increasing the amounts of vinylacetate or acrylamide units incorporated into the copolymericchains damages much of the performance. A favorable moleratio of vinyl acetate or acrylamide was found to be 45 : 55.Based on this mole ratio, the adhesion capability and filmbehaviors of the sizing agent reach their maximal valuessimultaneously. This demonstrates that the sizing agentshould be synthesized under this copolymer composition fromthe viewpoint of adhesion and film behaviors.