Good dielectric performance and broadband dielectric polarization in Ag,Nb co-doped TiO2

Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO₂-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag⁺/Nb⁵⁺ co-doped (Ag_1/4Nb_3/4)_xTi_1−xO₂ (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 10³ and 1.6 × 10⁴ at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics.     

Nitrogen-doped hierarchically porous carbon obtained via single step method for high performance supercapacitors

In the present work, nitrogen doped hierarchically activated porous carbon (APC) samples have been synthesized via single step scalable method using ethylene di-amine tetra acetic acid (EDTA) as precursor and KOH as activating agent. Activated porous carbons with different pore sizes have been developed by varying the activation temperature. SEM, TEM and SAXS analysis suggest that with variation of activation temperature, a hierarchical porous structure with interconnected meso-pore and micro pores has been achieved. The sufficiently high surface area of the synthesized materials provides active sites to enhance the diffusion of ions between the electrolyte and the carbon electrodes. The electrode prepared at 800 °C activated sample exhibited highest specific capacitance of 274 Fg^-1 in two electrode setup, at a current density of 0.1 Ag^-1 in 1 M aqueous H₂SO₄. Along with this, it showed maximum energy density of 9.5 Whkg^?1 at a power density of 64.5 Wkg^-1. The remarkable electrochemical performance reveals that the synthesized nitrogen doped activated carbon electrodes derived from EDTA can be tuned to have optimum pore structure and pore size distribution for better electrochemical performance, so it can be considered as a potential electrode material for applications in electrochemical energy storage.     

Increasing Volumetric CO2 Uptake of Hypercrosslinked Polymers through Composite Formation

To overcome the drawbacks of solid microporous materials for CO₂ capture, this proof‐of‐concept study demonstrates a low‐cost and rapid method for producing composites consisting of hypercrosslinked polymers (HCP) with a polyethyleneimine (PEI) binder. The resulting materials capture CO₂ through physical and chemical absorption simultaneously. Compared with HCP, the composites exhibit higher CO₂ uptake, higher volumetric density, and improved tolerance to water which is attributed to the PEI binder.     

Modeling the effect of deep traps on the capacitance–voltage characteristics of p-type Si-doped GaAs Schottky diodes grown on high index GaAs substrates

Numerical simulation, using SILVACO-TCAD, is carried out to explain experimentally observed effects of different types of deep levels on the capacitance–voltage characteristics of p-type Si-doped GaAs Schottky diodes grown on high index GaAs substrates. Two diodes were grown on (311)A and (211)A oriented GaAs substrates using Molecular Beam Epitaxy (MBE). Although, deep levels were observed in both structures, the measured capacitance–voltage characteristics show a negative differential capacitance (NDC) for the (311)A diodes, while the (211)A devices display a usual behaviour. The NDC is related to the nature and spatial distribution of the deep levels, which are characterized by the Deep Level Transient Spectroscopy (DLTS) technique. In the (311)A structure only majority deep levels (hole traps) were observed while both majority and minority deep levels were present in the (211)A diodes. The simulation, which calculates the capacitance–voltage characteristics in the absence and presence of different types of deep levels, agrees well with the experimentally observed behaviour.     

超高压大容量铝电解电容器的研制

分析了大功率设备用超高压大容量铝电解电容器的特点,通过研制工作电解液、制订制作工艺及零部件设计方案,研制出的超高压大容量铝电解电容器具有损耗角正切小(tgδ为0.25)、承受纹波电流能力强(100 Hz,2.12～27.8 A)及寿命长的特点,耐久性达到85℃,5 000 h。     

Volumetric Change and Surface Properties of Temperature-Sensitive Polyvinylalcohol (PVA) Hydrogel

Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H₂O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel.     

新型毫米波微带带通滤波器

介绍了一种新型的加载电容型毫米波微带带通滤波器。对这种滤波器进行了分析,推导出了滤波器中所用谐振单元间的耦合系数。该滤波器通过加载电容而出现慢波效应,使得在不改变电路性能的情况下,减小了电路尺寸。同时由于电路中加载电容形成的慢波效应而出现了带阻效应,因此对谐波有很好的抑制作用。利用高频分析软件CST仿真分析并设计了这种新型的加载电容型毫米波微带带通滤波器,实验结果与设计曲线结果相符。     

罗茨真空泵机组抽气速率分析

罗茨真空泵机组因配用前级泵不同和所处工作压力范围的差异，相应其抽气速率变化较大，设计中应根据具体工况条件及真空系统使用要求，力求使罗茨真空泵机组体现好的适用性和经济性。     

基于充放电原理实现的微电容测量电路

具有抗分布电容以及简单实用等特性的充放电电路是目前微电容测量中广泛采用的一种测量电路。本文对基于充放电原理的微电容测量电路进行了深入研究，并介绍一种基于充放电原理的实用电路。     

电容传感器在使用中存在的几个问题及处理方法

随着电容测量技术的迅速发展，电容传感器在非电量测量和自动检测中得到广泛应用，但它在使用过程中也存在一些问题，针对在使用电容传感器过程中存在的几个问题，从电容传感器的原理和工作过程两个方面进行了讨论，并提出行之有效的处理方法。