Mn掺杂Ca0.16Sr0.04Li0.4Nd0.4TiO3微波介质陶瓷介电性能的研究

采用传统固相法制备了MnO2掺杂Ca0.16Sr0.04Li04Nd04TiO3微波介质陶瓷,并借助X射线衍射仪、扫描电子显微镜、网络矢量分析仪和精密阻抗分析仪对微波陶瓷的物相结构、表面形貌、介电性能和电学微结构进行了分析.结果表明掺杂MnO2部分进入Ca0.16Sr0.04Li0.4Nd04TiO3陶瓷晶格Ti4位中并导致衍射主峰衍射角向高角度轻微偏移,所得陶瓷晶粒大小约5 μm.随着MnO2含量的增加,观察到显著的Mn-Li氧化物杂相,过高的MnO2掺杂使得Ca0.16Sr0.04Li04Nd04TiO3陶瓷晶粒的主要生长方向由(200)变为(220).MnO2含量的增加使得陶瓷介电常数εr从140降至122,品质因子Qf从1450显著升至1960 GHz,谐振温度系数Τf较为稳定且均为40 ppm/℃左右.陶瓷内部由Li+陶瓷表面电学阻抗、晶界阻抗、晶壳和晶核形成的晶粒阻抗构成,其中晶界的电阻贡献主要来自于Li+挥发或析出形成的阳离子空位电导;晶壳和晶核电阻为电子-空穴与氧空位相互耦合形成的电导.微波陶瓷的介质损耗主要来自于晶粒区域晶核的高度半导化各构成电学微结构部件载流子束缚能力大小与活化能规律趋于一致.     

单分散球状纳米金颗粒的合成*

综述了近年来单分散球状金纳米颗粒的合成研究进展。分析了球状单分散金纳米颗粒的应用前景,介绍了单分散球状金纳米颗粒的主要合成方法如种子生长、回流熟化、尺寸选择沉淀分级以及电泳法等,评述了各种方法的优缺点。最后提出了单分散球状金纳米颗粒合成的一些问题,并展望了单分散球状金纳米颗粒的研究和发展方向。     

吡唑啉-β-二酮类分子设计合成和抑菌活性

利用系统搜索和模拟退火程序对1－苯基－3－甲基－4－（4－氯苯甲酰基）－吡唑啉－5－酮和1－苯基－3－甲基－4－（4－硝基苯甲酰基）－吡唑啉－5－酮两个吡唑啉β－二酮分子进行分子力学计算和分子动力学研究。采用纸碟法测定它们的广谱抗菌活性。利用Gaussian94程序进行量子化学从头算，计算结果与抑菌活性测定结果相吻合。     

SiO2气凝胶分子动力学模拟研究进展

二氧化硅(SiO₂)气凝胶是一种拥有三维骨架网络结构的纳米多孔材料,具有高孔隙率、低密度和低热导率等许多独特的性能。但是由于二氧化硅气凝胶本身的脆性及高温稳定性差等原因,限制了其大规模应用。二氧化硅气凝胶的热力学性能与其内部的三维骨架和孔结构紧密相关,掌握二氧化硅气凝胶内部微结构演化规律与宏观性能的关联,是改善其热力学性能的前提。分子动力学模拟可以从原子层面分析和探索气凝胶的结构并预测其热力学性能。本文对分子动力学模拟下二氧化硅气凝胶势函数、多孔结构建模、结构表征、力学性能和热性能方面进行了详细总结,有助于从原子层面解释二氧化硅气凝胶结构与性能之间的关系,为从成分和结构方面设计气凝胶提供一种理论指导方法。     

boldmath Characterization of the BaBiO3-doped BaTiO3 positive temperature coefficient of a resistivity ceramic using impedance spectroscopy with Tc=155℃

BaBiO₃-doped BaTiO₃ (BB-BT) ceramic, as a candidate for lead-free positive temperature coefficient of resistivity (PTCR) materials with a higher Curie temperature, has been synthesized in air by a conventional sintering technique. The temperature dependence of resistivity shows that the phase transition of the PTC thermistor ceramic occurs at the Curie temperature, T_c=155 ℃, which is higher than that of BaTiO₃ ( ≤ 130 ℃). Analysis of ac impedance data using complex impedance spectroscopy gives the alternate current (AC) resistance of the PTCR ceramic. By additional use of the complex electric modulus formalism to analyse the same data, the inhomogeneous nature of the ceramic may be unveiled. The impedance spectra reveal that the grain resistance of the BB-BT sample is slightly influenced by the increase of temperature, indicating that the increase in overall resistivity is entirely due to a grain-boundary effect. Based on the dependence of the extent to which the peaks of the imaginary part of electric modulus and impedance are matched on frequency, the conduction mechanism is also discussed for a BB-BT ceramic system.     

Characterization of the BaBiO3-doped BaTiO3 positive temperature coefficient of a resistivity ceramic using impedance spectroscopy with Tc=155℃

BaBiO 3-doped BaTiO3(BB-BT) ceramic,as a candidate for lead-free positive temperature coefficient of resistivity (PTCR) materials with a higher Curie temperature,has been synthesized in air by a conventional sintering technique. The temperature dependence of resistivity shows that the phase transition of the PTC thermistor ceramic occurs at the Curie temperature,Tc=155℃,which is higher than that of BaTiO3(≤130℃). Analysis of ac impedance data using complex impedance spectroscopy gives the alternate current (AC) resistance of the PTCR ceramic. By additional use of the complex electric modulus formalism to analyse the same data,the inhomogeneous nature of the ceramic may be unveiled. The impedance spectra reveal that the grain resistance of the BB-BT sample is slightly influenced by the increase of temperature,indicating that the increase in overall resistivity is entirely due to a grain-boundary effect. Based on the dependence of the extent to which the peaks of the imaginary part of electric modulus and impedance are matched on frequency,the conduction mechanism is also discussed for a BB-BT ceramic system.     

GC法同时测定酚氨咖敏片中4种组分

建立了同时测定酚氨咖敏片中对乙酰氨基酚、氨基比林、咖啡因和马来酸氯苯那敏4组分含量的毛细管气相色谱法。采用SE-30大口径毛细管色谱柱(30 m×0.53 mm,1.0μm),柱温190℃,汽化室温度220℃,检测器为FID,检测温度250℃,载气为高纯N2,分流比为1∶6,内标为盐酸麻黄碱,以无水乙醇为溶剂,样品无需衍生化处理,直接进样测定。样品中各组分完全分离,辅料无干扰,对乙酰氨基酚、氨基比林、咖啡因和马来酸氯苯那敏分别在20~2000μg/mL、15~1500μg/mL、10~500μg/mL和20~100μg/mL范围内线性关系良好(r0.999),各组分的平均回收率在99.6%~101.2%范围内,RSD2%。     

BaFe0.4Sn0.6O3/BaBiO3负温度系数复合热敏陶瓷阻抗分析

以BaBiO₃为导电相,BaFe_0.4Sn_0.6O₃为高阻相,采用固态反应法制备了不同BaBiO₃含量的BaFe_0.4Sn_0.6O₃/BaBiO₃负温度系数(NTC)热敏复合陶瓷.为获得在渗流阈值(即BaBiO₃含量为12 mol%)前后复合陶瓷的内部导电机理,对复合陶瓷进行了阻抗分析.分     

Hausdorff型测度的性质

本文研究维纹(Dimension Print)所对应的Hausdorff型测度ξα(·),α=(α₁,α₂,…α_n)∈Rⁿ⁺ ,得到它与Hausdorff测度的一些关系,利用这些关系我们给出Rⁿ中一个集合E的Hausdorff型测度ξ^α(E)是正有限值的若干判定条件.     

装备可靠性增长率确定方法研究

从介绍装备可靠性门限值要求入手 ,提出了装备可靠性增长率的确定问题 .充分考虑各种因素对装备外场可靠性增长率影响 ,利用层次分析原理确定了这些因素对装备可靠性增长的影响权重 ,将此权重用于模糊综合评判 ,得到了 Duane模型中增长率的确定方法 .