Glass fiber reinforced bismaleimide/epoxy BaTiO3 nano composites for high voltage applications

BaTiO₃/bismaleimide/epoxy/glass fiber reinforced composites were prepared using E-glass fiber (E-GF) and silane coated E-glass fiber (SC-EGF) separately as reinforcement. BaTiO₃ nanoparticles were prepared by hydrothermal method. Results show that the addition of BaTiO₃ nanoparticles has significant effects on the mechanical and dielectric properties of the composite. Both E-GF and SC-EGF reinforced BaTiO₃/bismaleimide/epoxy composites with 2 wt percentages of BaTiO₃ nanoparticles showed improved tensile strength, flexural strength and dielectric constant and those with 3% showed high dielectric strength indicating this composition is more adaptable for high voltage insulating applications. Dielectric constants and dielectric loss of the fabricated nanocomposites have been obtained at higher frequencies (in GHz) by using Vector Network Analyser at room temperature and was found to be highest for the BMI-Epoxy nanocomposite with 1% weight nanofiller.     

Fabrication of exfoliated graphite reinforced silicone rubber composites - Mechanical,tribological and dielectric properties

The effect of exfoliated graphite (EG) on the mechanical, tribological and dielectric properties of the silicone rubber (QM) composites has been systematically investigated and analysed. Morphological analysis of the composites helps to understand the interfacial interaction between the filler and the rubber matrix as well as wear mechanism respectively. An enhancement in the mechanical, tribological and dielectric properties was observed with an increase in filler loading and better performance was observed at 7 phr of filler loading. The improvement in performance is attributed to the better interaction between the QM chains and the EG layers as evident from the AFM and TEM analysis. It is also evident from the Kraus plot which supports the reinforcing effect of EG in QM matrix.     

Nanocomposites induced by two-dimensional titanium carbide nanosheets for highly efficient energy storage

Surface group-rich titanium carbide nanosheets (TCNSs) were successfully fabricated by simply etching Ti₃AlC₂ powders and used as dielectric fillers to promote the dielectric and energy storage performances of poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-based composites. The PVDF-HFP/TCNS composites realize a high dielectric constant and low dielectric loss of 16.3 and 0.034 at 10² Hz, respectively. Importantly, a high energy storage density (U_e) of 0.367 J cm⁻³ at 900 kV cm⁻¹ and a high energy storage efficiency (η ≥ 78.9%) at a TCNS content of only 0.5 wt% are obtained, which indicates that incorporating TCNS is an efficient route in enhancing U_e while maintaining a high level η of the PVDF-HFP-based composites. According to detailed characterization results, a mechanism related to the reduction of lamellar crystals in the PVDF-HFP matrix is suggested. The above mechanism restricts the movement of polymer chains near the filler-matrix interface and is proposed to be responsible for the outstanding dielectric and energy storage performances. Consequently, this work provides a simple and effective method for fabricating highly efficient energy storage nanocomposites.     

Parallel single-cell optical transit dielectrophoresis cytometer

In this work, we present an optical transit DEP flow cytometer for parallel single-cell analysis. Each cell's dielectric property is inferred from velocity perturbations due to DEP actuation in a microfluidic channel. Dual LED sources facilitate velocity measurement by producing two transit shadows for each cell passing through the channel. These shadows are detected using a 256-pixel linear optical array detector. Massively parallel analysis is possible as each pixel of the detector can independently analyze the passing cells. A wide channel (∼18 mm) was employed to carry many particles simultaneously, and the system was capable of detecting the velocity of over 200 cells simultaneously. We have achieved analysis rates for 10 µm diameter polystyrene spheres response exceeding 250 per second. With appropriate calibration, this DEP cytometer can quantitatively measure the dielectric response. The dielectric response (Clausius–Mossotti factor) of viable CHO cells was measured over the frequency range of 100 kHz to 6 MHz, and the obtained response matches the previously measured values by our group. The DEP cytometer uses simple modular components to achieve high throughput label-free single-cell dielectric analysis and can begin analyzing particles within 10 s after starting to pump the sample into the channel.     

Principles of Surface Potential Estimation in Mixed Electrolyte Solutions:Taking into Account Dielectric Saturation

The dielectric properties between in-particle/water interface and bulk solution are significantly different, which are ignored in the theories of surface potential estimation. The analytical expressions of surface potential considering the dielectric saturation were derived in mixed electrolytes based on the nonlinear Poisson-Boltzmann equation. The surface potentials calculated from the approximate analytical and exact numerical solutions agreed with each other for a wide range of surface charge densities and ion concentrations. The effects of dielectric saturation became important for surface charge densities larger than 0.30 C/m\begin{document}$ ^2 $\end{document}. The analytical models of surface potential in different mixed electrolytes were valid based on original Poisson-Boltzmann equation for surface charge densities smaller than 0.30 C/m\begin{document}$ ^2 $\end{document}. The analytical model of surface potential considering the dielectric saturation for low surface charge density can return to the result of classical Poisson-Boltzmann theory. The obtained surface potential in this study can correctly predict the adsorption selectivity between monovalent and bivalent counterions.     

Mechanistic model for the dielectric spectrum of a simple dielectric material

ABSTRACT

In this paper, we perform molecular dynamics simulations of a dielectric fluidic material composed of permanent molecular dipoles. The dielectric spectrum features two peaks at lower frequencies than the system phonon frequency. The primary peak is observed at all temperatures studied and shifts toward lower frequencies as the temperature decreases. During this shift, the secondary peak emerges with a higher peak frequency than the primary peak. The secondary peak amplitude increases as the temperature decreases. Both peaks are dependent on the wavevector; in the small wavevector regime, the primary peak is shifted to higher frequencies as the wavevector squared and the secondary peak amplitude increases as the wavevector increases, but shows no shift in frequency. From the polarisation balance equation, we propose a model for the dielectric spectrum. This captures the spectrum features, and we conjecture that the primary peak is due to dipole moment correlations (Debye-type) and the secondary peak is due to the correlation between the dipole moment and a microscopic local field.     

Electrical properties of interdigitated partially bent like shaped liquid crystalline compound

This article represents the electrical studies of an interdigitated highly skewed N(4-n-pentyloxybenzylidene) 4-n-alkylaniline (5O.16) compound. Interestingly the compound is partially bent like and unsymmetrical in alkyl chain length. Dielectric and impedance spectroscopy studies indicate the coupling between the liquid crystal and the electrical field. Studies were carried out as a function of temperature as well as frequency. Semicircular nature of the Cole–Cole plots indicates the reorientation of the molecule with the applied field. Using the experimental data and the theoretically fitted results the effective equivalent model circuit was designed. Which used to explain the behavior of the compound under the external electric effect and the influence of the electrodes with different variable represent the resistor circuit. However, the effect of the conductivity of temperature and frequency are also reported.     

介质阻挡放电甲醇脱氢偶联一步合成乙二醇反应中氢气的催化作用

利用原位发射光谱表征和在线色谱分析,研究了甲醇介质阻挡放电脱氢偶联一步合成乙二醇反应中氢气的催化作用,考察了放电频率、甲醇和氢气进料量以及反应压力的影响.结果表明,在介质阻挡放电产生的非平衡等离子体中,H2不但能显著提高甲醇转化率,而且能显著提高乙二醇的选择性.在300°C,0.1 MPa,反应器注入功率为11 W,放电频率为12.0 k Hz,甲醇气体进料量为11.1 m L/min,氢气进料量为80–180 m L/min的条件下,甲醇转化率接近30%,乙二醇选择性大于75%.乙二醇收率与激发态氢原子的Hα谱线强度之间存在同增同减关系.由此推测,氢原子是起催化作用的活性氢物种.活性氢物种的生成途径是:基态氢分子通过与电子碰撞变成激发态,激发态氢分子通过第一激发态氢自动解离为基态氢原子.放电反应条件通过影响氢分子解离来影响氢气的催化作用.氢气在非平衡等离子体中显示的催化作用有可能为开辟新的化学合成途径提供重要机遇.     

微波场对SrTiO3化学合成中热过程的影响

在分析微波场中SrTiO3化学合成体系与电磁场相互作用的基础上,探讨合成体系在微波场中的加热机制和影响升温的主要因素（如合成体系的介电性质、保温材料的结构、生还的致密度等）,结果表明,TiO2和SrCO3在低温阶段对体系的升温速率的贡献相接近;高温阶段体系升温主要是TiO2的贡献,同时产物对升温有较大的影响。微波合成与常规合成再加热方式上的明显不同,对合成过程、合成时间等影响较大。     

TSC defect level in silicon produced by irradiation with muons of GeV-energy

Deep level transient spectroscopy has been used to observe the reduced concentrations of vacancy-related defects in γ-irradiated n-type Si containing hydrogen atoms. Data are presented on the efficiency and depth of this damage reduction as a function of the duration and temperature of the exposure to the plasma used to introduce the atomic hydrogen. A 3-hour exposure in an H plasma at 300°C prior to irradiation reduced the concentrations of the O-V, V-V and P-V centres by half or more to a depth of ～20 μm, compared to the control samples.