烷烃电离能和生成焓的相关性

根据化合物形成过程中价电子能量变化与生成焓之间的关系, 推导出烷烃的生成焓和电离能之间的关系. 以21个烷烃化合物为模型将实验测定的电离能与标准生成焓进行直接关联, 证实了模型方程的适用性, 所得回归方程的相关系数达到0.9999, 估算值与实验值之间的标准偏差仅为0.03 eV. 同时还利用实验测定的标准生成焓对一系列烷烃的电离能作了预测.     

醇系溶剂中冠醚与碱金属离子的配位反应

The enthalpy changes, entropy changes and equilibrium constants of coordination reactions of 18-crown-6 with the alkali ions Na+ and K+ at 298.15K were measured by using RD-496 microcalorimeter with methanol, ethanol, n-propanol and n-butanol as solvents respectively. The results indicated that the enthalpy changes △rHm, entropy changes △rSm, and the stability of the complexes are closely related with the polarity of the solvents, and the order of the stability is ethanol>methanol>n-propanol>n-butanol>H2O for the same complex in the solvents investigated. The stability order was reasonably explained by relating the stability constants of the complexes with the dielectric constants of these solvents, and by using the model of solvated-desolvated ions and ion pair in the coordination reactions.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

Two-dimensional TiO2 (001) nanosheets as an effective photo-assisted recyclable sensor for the electrochemical detection of bisphenol A

Electrochemical detection is an efficient method for the detection of Bisphenol A (BPA). Herein, a sensitive photo-electrochemical sensor based on two-dimensional (2D) TiO₂ (001) nanosheets was fabricated and then used for BPA electrochemical detection. Upon light irradiation, the 2D TiO₂ (001) nanosheets electrode provided a lower detection limit of BPA detection compared with an ambient electrochemical determination. The low detection limit is ∼5.37 nmol/L (S/N = 3). Furthermore, profiting from the photoelectric characteristics, the 2D TiO₂ (001) nanosheets electrode exhibits a nice regeneration property. After 45 min of light irradiation, the electrochemical signal was regenerated from 14.7% to 82.9% of the original signal at the 6^th cycle. This is attributed to the non-selective OH mediation produced by the 2D TiO₂ (001) nanosheets mineralizing anodic polymeric products and resuming surface reactive sites. This investigation indicates that photo-assistance is an efficient method to improve the electrochemical sensor for detecting BPA in water environments.     

MORPHOLOGICAL STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE POLYESTER——MORPHOLOGY OF SHEAR ORIENTED FILMS

The morphology of shear-oriented films of a thermotropic liquid crystalline polyester containing a triad ester mesogenic unit and a flexible spacer has been investigated in details. The formation conditions and process, the fine structures and the relaxation process of mat structure in the oriented films have been observed and discussed.     

Synthesis and electrical properties of Vanadyl(V)chloride complexes of N-2(4,5,6-monosubstituted pyridyl)-N′-aryl substituted thioureas

VOCl₃ formed six-coordinated complexes with N-aryl-N′-2(4,5,6-mono-substituted pyridyl)thioureas of the general formula [VOCl₃(RNHCSNHR′)], where R = pyridyl, 5-nitropyridyl, 4-methylpyridyl, 6-methylpyridyl groups and R′ = —C₆H₅, o-C₆H₅(CH₃) and p-C₆H₄(CH₃). The complexes have been characterized by means of elemental analysis, molar conductance, magnetic susceptibility, IR, UV—VIS, and ¹H NMR spectral data. The thermally stimulated depolarization effect was studied in samples polarized under different conditions. The results indicate two distinct transitions in the temperature range 92–100°C and 120–125°C for the ligands, whereas the VOCl₃-complexes show no breaks. The polarization—depolarization phenomena were correlated with the physicochemical changes occurring in the matrix. Depolarization kinetic data such as activation energy (E_a) and relaxation time (τ) of the electrets are reported.     

Raman and infrared studies of NaLa(MoO4)2:Nd3+

The polarized Raman and i.r. (powder) spectra of 0.5 mole % neodymium doped NaLa(MoO₄)₂ have been analysed on the basis of C_4h crystal symmetry. Group theoretically predicted fundamentals have been observed. The frequencies and intensities are not altered due to doping.     

Linear micromagnetics in thin films: I. Basic equations in the case of in-plane and of perpendicular uniaxial anisotropies

Within the framework of a linearized micromagnetic approach we calculate the formal solutions of the basic equations describing the position dependence of the vector of magnetization in a thin magnetic film. Thereby various cases of mutual orientation of the easy axis of the uniaxial anisotropy, of the external field and of the plane of the film are considered including the situation where the magnetization is perpendicular to the plane of the film. As the origin of local deviations of the direction of magnetization from its mean direction (magnetization ripple) we assume not only random fluctuations of the anisotropy but also a position dependence of the saturation magnetization and of the exchange energy. The stochastic fluctuations of these parameters are known to be closely related to the defect structure of the magnetic material. Furthermore, we derive the relation between correlation functions of the defect structure and the resulting magnetization correlations. This relation serves as the starting point for a full discussion of the statistical properties of the ripple. In part II of this paper we shall give such a discussion in detail for the case of polycrystalline films.     

Oxidation of chromium carbide

The oxidation of chromium carbide has been studied gravimetrically. Products of reaction have been examined by gas sorption analysis and X-ray diffraction. Changes in phase composition, crystallinity and crystallite size are correlated with the reaction conditions.Chromium carbide, Cr₃C₂, differs from most of the transitional metal carbides in that it forms stable films of metal oxide (Cr₂O₃) around the remaining carbide particles, inhibiting further oxidation. Thus chromium carbide additive inhibits oxidation of interstitial zirconium carbide, ZrC, by forming some chromic oxide which stabilises the zirconia (ZrO₂) layer around the remaining carbide crystallites.