Ho and Ti co-doped BiFeO_3 multiferroic ceramics with enhanced magnetization and ultrahigh electrical resistivity

Bi0.9Ho0.1Fe0.95O3 and Bi0.9Ho0.1Fe0.9Ti0.05O3 ceramics were prepared and compared to reveal the effects of Ho and Ti codoping in BiFeO3. X-ray diffraction indicated that both ceramics had a high rhombohedral perovskite phase content, and microstructural analyses showed that the grains of the Bi0.9Ho0.1Fe0.9Ti0.05O3 ceramics were much smaller than those of Bi0.9Ho0.1Fe0.95O3. An electrical resistivity of more than 1 × 1014?·cm at room temperature, and a magnetic hysteresis loop with a remnant magnetization 2Mr of ～ 0.485 emu/g were obtained for Bi0.9Ho0.1Fe0.9Ti0.05O3; both were much higher than those of Bi0.9Ho0.1Fe0.95O3. Changes in the defect subsystem of BiFeO3 induced by Fe-deficiency and(Ho,Ti) codoping are proposed as being responsible for the improvement in the properties.     

氦气实验回路的初步概念设计

为了验证TBM的设计．在氦气实验网路中测试与TBM模块具有相同设计压力和温度的实物模型是非常必要的。本文介绍了该回路的主要特点及初步概念设计。     

Ultrafast Third-Order Nonlinear Optical Response of Organic-Inorganic Hybrid Materials （C19H25N2）7Hn [P2Mo18-n Vn O62]

We have measured the third-order optical nonlinearity of the organic-inorganic hybrid materials of supermolecules (C19H25N2)7Hn [P2Mo18-n Vn O62] (n = 1, 2, 4, 5) and their reactants (C19H25N2) Br and Hn 6[P2Mo18-n Vn O62] by using the ultrafast optical Kerr effect at 830 nm wavelength, with time resolution of 115fs. By comparing the γ values of the supermolecules and their reactants, it is concluded that the charge-transfer eahanced remarkably the third-order optical nonlinearity of the compounds. With the increment of the number of the vanadium atoms,the electron distribution changed strongly and the γ value decreased dramatically.     

2,3,7,8—四氯代—N—乙基吩噻嗪的荧光法研究

本文研究了２，３，７，８－四氯代－Ｎ－乙基吩噻嗪在不同条件下的荧光强度变化规律，为荧光体确定了最佳发光体系，对提高有机光导体的灵敏度具有实际意义。     

基于改进标准加入法的碳酸饮料中防腐剂和甜味剂高通量筛查分析

利用正交设计分别配制含有三种防腐剂、四种甜味剂的模拟水样,采用核独立成分分析（KICA）处理模拟水样与加入不同含量标准品的饮料样品的紫外光谱(UV)数据,得到其中待测添加剂或背景成分的UV轮廓的独立组分(IC)信息,以IC的系数矩阵进行支持向量回归（SVR）分析,建立模拟样品中防腐剂与甜味剂的UV-KICA-SVR预测模型。添加不同含量水平添加剂的碳酸饮料样品,采用KICA处理其测试得到的UV光谱数据,得到与添加剂对应的IC信息及量,加入量与预测量线性回归方程截距即为饮料中添加剂含量。利用化学计量学“盲源信号分离”方法提取饮料样品中的待测添加剂IC信息与样品基质信息,利用SVR对解析得到的IC信号回归分析建模,改进传统单一组分测定的标准加入法,建立了碳酸饮料样品中防腐剂和甜味剂高通量筛查分析的新方法。方法用于测定碳酸饮料中山梨酸钾,苯甲酸钠、对羟基苯甲酸甲酯钠三种防腐剂与糖精钠、安赛蜜,阿斯巴甜和甘草酸铵四种甜味剂含量,检测限(LOD)为0.2～1.0 mg·L-1,测定结果与传统的色谱方法相当。     

关于成像公式精确性的分析

1 透镜、面镜成像与成像公式 图1和图2是经典的面镜成像和透镜成像的光路图.由物求像,由像求物,由物、像求焦点的问题都由光路图得到.     

Properties of Co-Doped 0.92（Na0.5Bi0.5） TiO3-0.08BaTiO3 Lead-Free Ceramics

Lead-free piezoelectric ceramics 0.92（Bi0.5Na0.5）TiO3-0.08BaTiO3 ＋ xmol% Co3＋ （BNBT-Co, x = 0-8） are prepared by the solid state reaction method. Effects of the amount of Co^3＋ on the electrical properties and phase transition are studied. The results indicate that the addition of Co^3＋ enhances the mechanical quality factor Q^3＋ significantly, whereas the dissipation factor tanδ has a minimum value at x = 3.5. Meanwhile, addition of Co^3＋ leads to small decreases of piezoelectric constant d33, and planar electromechanical coupling kp. The present 0.92（Bio.aNao.5） TiO3-0.08BaTiO3＋3.5 moi% Co^3＋ ceramics exhibit good performance with mechanical quality factor Qm = 910, piezoelectric constant d33 = 106pC/N, planar electromechanical coupling kp =10% and dissipation factor tanδ = 1.1% at 1 kHz. Saturated polarization hysteresis loops have been obtained for BNBT-Co ceramics. Two dielectric peaks at depolarization temperature Td and Tm appear in the curves of ε33^T vs temperature for the pure BNBT ceramics. However, the first dielectric peak Td disappears after the addition of Co^3＋, which means that the transition from ferroelectric to antiferroelectric phase has been eliminated.     

VDF/TrFE铁电共聚物极化分布与退极化过程的激光强度调制方法研究

建立起激光强度调制法测量装置及其测量与数据处理方法,研究了VDF/TrFE铁电共聚物的极化分布和退极化过程.发现25μm厚的VDF(80)/TrFE(20)薄膜在距表面8μm左右薄层热电系数显示极大值,而12μm厚的则在中心处,两者的热电系数皆以两表面呈对称分布.在145℃热处理产生退极化.随着时间的增长,热电系数减小,退极化由试样的一面向另一面逐渐进行,2h后由强电场形成的极化基本消失.直流极化30μm厚的VDF(70)/TrFE(30)薄膜,热电系数分别在离两表面6,8μm处达恒定值,基本以两表面呈反 关键词：     

物理学在现代汽车ABS上的应用

随着汽车行驶速度的提高,道路行车密度的增大,对于汽车行驶安全性能的要求也越来越高.汽车的防抱死制动系统(ABS)应运而生,它是以传统制动系统为基础,采用电子控制技术,在制动时防止车轮抱死的一种机电一体化系统.其中应用了许多力学、电学、磁学、液压等物理学理论,通过对ABS的讨论了解物理学在现代技术中的应用.