Dielectric properties of tetragonal tungsten bronze films deposited by RF magnetron sputtering

Tetragonal tungsten bronze (TTB) films have been synthesised on Pt(111)/TiO₂/SiO₂/Si substrates from Ba₂LnFeNb₄O₁₅ ceramics (Ln = La, Nd, Eu) by RF magnetron sputtering. X-ray diffraction measurements evidenced the multi-oriented nature of films with some degrees of preferential orientation along (111). The dependence of the dielectric properties on temperature and frequency has been investigated. The dielectric properties of the films are similar to those of the bulk, i.e., ε ∼150 and σ ∼10⁻⁶ Ω⁻¹ cm⁻¹ at 1 MHz and room temperature. The films exhibit two dielectric anomalies which are attributed to Maxwell Wagner polarization mechanism and relaxor behaviour. Both anomalies are sensitive to post-annealing under oxygen atmosphere and their activation energies are similar E_a ∼0.30 eV. They are explained in terms of electrically heterogeneous contributions in the films.     

Discrete element simulation of effects of multicontact loading on single particle crushing

Particle crushing commonly occurs in granular materials and affects their structures and mechanical properties. Unlike idealized particles in experimental single particle crushing tests with two loading points, natural particles are crushed under multicontact loading. To date, the criteria and patterns of particle crushing under multicontact conditions are not fully understood. By using the three-dimensional discrete element method, this report explores the effect of multicontact loading on the crushing criterion of a single particle, the crushing pattern, and the relationship between the particle crushing strength and loading distribution. The particles are modelled as aggregates of glued Voronoi polyhedra. The numerical results indicate that the logarithm of the mean principal stress has a good linear correlation with the coordination number. For a specific coordination number, the number of child particles presents a significant normal distribution. For a specific number of child particles, the volumes of child particles can be statistically described as normal or gamma distribution. Three typical models are proposed to qualitatively analyse the relationship between the loading distribution and crushing strength. The relevant conclusions can be helpful in engineering practice and in further studies on crushable granular materials via the discrete element method.     

Ni2P-NiS双助剂促进g-C3N4光催化产氢动力学

本文通过简单的一步水热法得到Ni₂P-NiS双助催化剂,之后采用溶剂蒸发法将Ni₂P-NiS与g-C₃N₄纳米片结合构建获得无贵金属的Ni₂P-NiS/g-C₃N₄异质结。研究结果表明,优化后的复合材料具有良好的光催化产氢活性,其产氢速率最高可到6892.7 μmol·g^-1·h^-1,分别为g-C₃N₄ (150 μmol·g^-1·h^-1)、15%NiS/g-C₃N₄ (914.5 μmol·g^-1·h^-1)和15%Ni₂P/g-C₃N₄ (1565.9 μmol·g^-1·h^-1)的46.1、7.5和4.4倍。这主要归因于Ni₂P-NiS相比Ni₂P和NiS单体具有更好的载流子转移能力,其与g-C₃N₄形成的肖特基势垒能有效促进光生载流子在二者界面上的分离,同时Ni₂P-NiS能进一步降低析氢过电势,进而显著增强了表面析氢反应动力学。本研究为开发稳定、高效的非贵金属产氢助剂提供了实验基础。     

表面凹槽对流体动压润滑油膜厚度的影响

利用自行研发的面接触光干涉油膜厚度测量系统,对表面凹槽滑块的流体动压润滑油膜厚度进行了试验测量,试验中以静止的微型凹槽滑块平面和旋转的光学透明圆盘平面构成润滑副,且两润滑平面始终保持平行;在固定的载荷(速度)条件下,对油膜厚度-速度(载荷)曲线进行测量.结果表明：凹槽的宽度,深度,方向和位置等因素对油膜厚度有着重要影响.同时采用经典Reynolds方程对油膜厚度进行了理论计算,结果表明理论值在某些条件下并不能解释试验结果.     

Electrical characteristics of Pd Schottky contacts on ZnO films

The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φ_b) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements.     

Electrical and interfacial properties of Au/P3HT:PCBM/n-Si Schottky barrier diodes at room temperature

In this study, a gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/n-type silicon (Au/P3HT:PCBM/n-Si) metal-polymer-semiconductor (MPS) Schottky barrier diode (SBD) was fabricated. To accomplish this, a spin-coating system and a thermal evaporation were used for preparation of a P3HT/PCBM layer system and for deposition of metal contacts, respectively. The forward- and reverse-bias current–voltage (I–V) characteristics of the MPS SBD at room temperature were studied to investigate its main electrical parameters such as ideality factor (n), barrier height (Φ_B), series resistance (R_s), shunt resistance (R_sh), and density of interface states (N_ss). The I–V characteristics have nonlinear behavior due to the effect of R_s, resulting in an n value (3.09) larger than unity. Additionally, it was found that n, Φ_B, R_s, R_sh, and N_ss have strong correlation with the applied bias. All results suggest that the P3HT/PCBM interfacial organic layer affects the Au/P3HT:PCBM/n-Si MPS SBD, and that R_s and N_ss are the main electrical parameters that affect the Au/P3HT:PCBM/n-Si MPS SBD. Furthermore, a lower N_ss compared with that of other types of MPS SBDs in the literature was achieved by using the P3HT/PCBM layer. This lowering shows that high-quality electronic and optoelectronic devices may be fabricated by using the Au/P3HT:PCBM/n-Si MPS SBD.     

浅谈变频器专用接触器的设计思路

从目前变频器行业在接触器使用方面存在的问题出发，本文介绍了变频器专用接触器的设计思路，并对几种方案进行了分析对比，从而得出了专用接触器安全、可靠、先进的特点。     

The effects of thermal annealing on the electrical characteristics of Au/n–InP/In diode

An Au/n–InP/In diode has been fabricated in the laboratory conditions and the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the diode have been measured in room temperature. In order to observe the effect of the thermal annealing, this diode has been annealed at temperatures 100 and 200 °C for 3 min in N₂ atmosphere. The characteristic parameters such as leakage current, barrier height and ideality factor of this diode have been calculated from the forward bias I–V and reverse bias C–V characteristics as a function of annealing temperature. Also the rectifying ratio of the diode is evaluated for as-deposited and annealed diode.     

肖特基结的制备与势垒测量

采用磁控溅射方法在Nb07％-SrTiO3基片上制作Au薄膜接触,并在氧气气氛下750℃退火30 min,在室温环境下测量电流电压和电容电压等特性曲线,观测整流特性,根据相应实验数据采用饱和电流法、电容C-2与反偏电压V成线性关系计算肖特基势垒的大小.     

Theoretical voltammetric response of electrodes coated by solid polymer electrolyte membranes

A model for the differential capacitance of metal electrodes coated by solid polymer electrolyte membranes, with acid/base groups attached to the membrane backbone, and in contact with an electrolyte solution is developed. With proper model parameters, the model is able to predict a limit response, given by Mott–Schottky or Gouy–Chapman–Stern theories depending on the dissociation degree and the density of ionizable acid/base groups. The model is also valid for other ionic membranes with proton donor/acceptor molecules as membrane counterions. Results are discussed in light of the electron transfer rate at membrane-coated electrodes for electrochemical reactions that strongly depend on the double layer structure. In this sense, the model provides a tool towards the understanding of the electro-catalytic activity on modified electrodes. It is shown that local maxima and minima in the differential capacitance as a function of the electrode potential may occur as consequence of the dissociation of acid/base molecular species, in absence of specific adsorption of immobile polymer anions on the electrode surface. Although the model extends the conceptual framework for the interpretation of cyclic voltammograms for these systems and the general theory about electrified interfaces, structural features of real systems are more complex and so, presented results only are qualitatively compared with experiments.