Thermal Conductivity Enhancement of Polyimide Film Induced from Exfoliated Graphene Prepared by Electrostatic Discharge Method

Dynamic intelligent risk assessment of hazardous chemical warehouse fire based on electrostatic discharge method and improved support vector machine

The paper describes the problem of electromagnetic compatibility for electrostatic discharge (ESD), which is most actual for ships where all systems are highly automated and susceptible to ESD digital technology. The results of electromagnetic compatibility tests of ship systems after their installation on the vessel allow to conclude that it is not enough to fulfill only the existing ESD immunity requirements of the Russian Maritime register of shipping which are currently confirmed by ESD tests in the laboratory. ESD methods and reasons have been analyzed. The possible accumulated potentials and parameters of currents, voltages and field strengths during discharge are presented. The existing ESD immunity standards are being considered. The scheme of the developed and certified generator of electrostatic discharges ESD – 25000 is presented. The most frequent defects under the influence of ESD are given. There have been formulated the equivalent schemes of the electric equipment housing at different lengths of grounding of the housing and the methods of connecting the cover with the housing. The results of measurements of electric field and magnetic field parameters are presented. The results of modeling and experiments are compared. The developed sensors, methods of their calibration and obtained technical characteristics are being tested. There are given the parameters and forms of ESD voltage and current, experimental data of ESD secondary effects in the EE hull and adjacent equipment, results of discharges in the ship's cable, interference in the supply network through secondary power sources. The most effective design and ESD protection methods have been analyzed

Since the usage of microelectronic components and IC's in electronic systems is growing year by year and reliability is always an issue, the designer has to be aware of possible failures of the components. The ESD (electrostatic discharge) phenomenon arouses more and more interest as these parts are sensitive to short time over voltages. Simulations to predict the effect of ESD in the actual power electronics circuitry are not possible as sufficient models for the components and the complete circuit configuration are not available. Experiments with ESD in conjunction with power electronic devices should make students aware of possible impacts of ESD pulses and methods to protect devices and circuitry. In this paper four experiments together with simple test circuits are presented, which show different aspects of ESD stress like the typical current and voltage wave forms of ESD pulses, system malfunction, pre deterioration and total damage of components

A fully integrated LC-type ESD/EMI filter was developed by the integrated passive devices (IPD) technology. Unique TVS diodes are employed to enhance its performance while maintaining robust ESD characteristics. The reliability and performance of ESD/EMI filter are confirmed based on both attenuation and electrostatic discharge (ESD) strength which could be evaluated by insertion loss (S parameter), ESD and transmission line pulse (TLP) testing method. As the results, the device shows very low leakage current less than 1nA. Its ESD protection and attenuation could be robustness exceed 28 A TLP and ±17 kV IEC 61000-4-2 and achieved as >;35 dB at 800 MHz ~3 GHz, respectively. The cut off frequency obtained of 160 MHz that can ensure high-speed data communication applications.

Chapter 7 - Immunity tests

Electrostatic discharge methods of zone location for paper chromatographs: Rapid approximate estimations of zone content by static discharge currents

Enhancement of thermal conductivity and kinematic viscosity in magnetically controllable maghemite (γ-Fe2O3) nanofluids

Changes in the thermal conductivities of paraffin and mono ethylene glycol (MEG) as a function of β-SiC nanoparticle concentration and size was studied. An enhancement in the effective thermal conductivity was found for both fluids (i.e., both paraffin and MEG) upon the addition of nanoparticles. Although an enhancement in thermal conductivity was found, the degree of enhancement depended on the nanoparticle concentration in a complex way. An increase in particle-to-particle interactions is thought to be the cause of the enhancement. However, the enhancement became muted at higher particle concentrations compared to lower ones. This phenomenon can be related to nanoparticles interactions. An improvement in the thermal conductivities for both fluids was also found as the nanoparticle size shrank. It is believed that the larger Brownian motion for smaller particles causes more particle-to-particle interactions, which, in turn, improves the thermal conductivity. The role that the base-fluid plays in the enhancement is complex. Lower fluid viscosities are believed to contribute to greater enhancement, but a second effect, the interaction of the fluid with the nanoparticle surface, can be even more important. Nanoparticle-liquid suspensions generate a shell of organized liquid molecules on the particle surface. These organized molecules more efficiently transmit energy, via phonons, to the bulk of the fluid. The efficient energy transmission results in enhanced thermal conductivity. The experimentally measured thermal conductivities of the suspensions were compared to a variety of models. None of the models proved to adequately predict the thermal conductivities of the nanoparticle suspensions.

Experimental study of thermal conductivity and convective heat transfer enhancement using CuO and TiO2 nanoparticles

To improve the perfection of a three-dimensional thermally conductive network in polyimide (PI) composite film and with respect to the economy and simplicity of processing, a strategy of the two-step synergism of Al2O3 microspheres and hexagonal boron nitride (BN) nanosheets was proposed. First, BN nanosheet-coated Al2O3 microspheres (Al2O3@BN) were prepared by electrostatic self-assembly method for the first step of the synergism. Then, the Al2O3@BN&BN/PI composite film containing Al2O3@BN and BN was fabricated by a two-step method for the second step of the synergism, and was systematically characterized. With an optimized mass ratio of 2 : 1 of Al2O3@BN to BN, the thermal conductivity of the 35 wt% Al2O3@BN&BN/PI composite film reached 3.35 W m−1 K−1, and was increased by 1664% compared to that of pure PI. The synergism of the Al2O3 and BN was the most significant in the Al2O3@BN&BN/PI composite film with the thermal conductivity, which was 36.6%, 23% and 22% higher than that of the Al2O3/PI, BN/PI and Al2O3@BN/PI composite films, respectively. The enhancement mechanism of heat conduction was clearly demonstrated. The BN coated on the surface of Al2O3 mainly played a bridging role between the Al2O3 and the BN network, which improved the perfection of the thermally conductive network. The Al2O3@BN segregated the PI matrix to construct the BN network with the typical segregated structure in the composite film, resulting in an efficient thermally conductive network. This work provided a novel strategy for the preparation of conductive polymer composites.

This paper presents experimental and theoretical determination of the effective thermal conductivity of various base fluids and nano TiO2 composition. Ultrasonically assisted sol–gel method was used for synthesising anatase TiO2 nanoparticles and dispersing them into base fluids using sonication for the synthesis of nanofluids. It is observed that thermal conductivity enhancement is significantly higher than that of base fluid. The thermal conductivity shows an increment with the addition of nanoparticles and confirms a 22% enhancement achievable in base fluids. The effect of base fluids is a complex idea and difficult to understand; lower base fluid viscosities were supposed to contribute higher in enhancement of thermal conductivity, but another important factor; i.e. fluid nanoparticles surface interaction, nanoparticles crystal type also contributes in enhancement. In the further study, as the sonication time increases; an improvement in the thermal conductivity of nanofluids is also observed. Except water-based nanofluids, all others show reasonably good agreement with the data predicted by Bruggeman model and the prediction is in the range of 5%. This study is important since it covers base fluids with a wide range of thermal conductivity and viscosity.

In this paper, an experimental investigaitons were made to analyze the thermal conductivity and viscosity of non-polar magnetic nanofluids with and without influence of magnetic field. Magnetic Fe3O4 nanoparticles were synthesized by chemical coprecipitation method and stable nanofluids were prepared by dispersing them into vacuum pump oil using sonicator without adding any surfactant. Both thermal conductivity and viscosity experiments were conducted in the volume concentrations from 0.05% to 1.0% and in the temperatures from 20 � C to 60 � C. Based on the results, without magnetic field, thermal conductivity and viscosity enhancements are 6.20% and 66%, respectively and with magnetic field of 900 G, thermal conductivity enhancement is 69%, with magnetic field of 1300 G, viscosity enhancement is 256% was observed for 1.0% of nanofluid at a temperature of 20 � C. The viscosity enhancement is more compared to thermal conductivity enhancement at same particle concentration and temperature and magnetic field. The chain-like structure of magnetic nanoparticles aggregates under magnetic field caused the enhancement in both thermal conductivity and viscosity.

The electrostatic adsorption method can fabricate composite materials with an arbitrary structure. Changing a parameter such as the size of an individual component, which alters the composition, can adjust the composite material's characteristics. To develop a thermally conductive and electrically insulating composite material with a high thermal conductivity and an acceptable breakdown strength, a polymethyl methacrylate (PMMA)/hexagonal boron nitride (h-BN) composite material was produced by changing the h-BN filler size or the PMMA particle size using the electrostatic adsorption method. Regardless of the h-BN size, the DC breakdown strength and the thermal conductivity of the composite increased and decreased, respectively, as the PMMA size increased. For composites with the same sized PMMA particles, the breakdown strength of the composite with a larger h-BN particle size was smaller than that of the composite with a smaller h-BN particle size. The thermal conductivity between these composites showed an inverse trend to the DC breakdown strength. These characteristics are attributed to the length of the h-BN, the filler orientation, and the change in the distance between fillers.

The electrostatic adsorption method can be used to produce composite materials with an arbitrary structure, and their properties may be tuned by changing the size of the individual components, which in turn alters the composition of the material. To develop a thermally conductive and electrically insulating composite material with high thermal conductivity and an acceptable breakdown strength, polymethylmethacrylate (PMMA)/hexagonal boron nitride (h-BN) composite materials were produced by electrostatic adsorption method. The breakdown strength decreases as the molding temperature increases. On the other hand, thermal conductivity increases as the molding temperature increases. In particular, the thermal conductivity of the composite molded at 250 °C drastically increases. It was suggested that the short distance among h-BN and the contact among h-BN led to these properties.

Vegetable oils (Ground nut) are being investigated to serve as a possible substitute for non-biodegradable mineral oils, which are currently being used as metal-cutting fluids in machining processes. In this study, thermophysical properties of hybrid nanofluids (vegetable oil) to be used as metalworking cutting fluids are investigated. In-situ synthesis of copper (Cu) and zinc (Zn) combined hybrid particles is performed by mechanical alloying with compositions of 50:50, 75:25, and 25:75 by weight. Characterizations of the synthesized powder were carried out using X-ray diffraction, a particle size analyzer, FE-SEM, and TEM. Hybrid nanofluids with all the three combinations of hybrid nanoparticles were prepared by dispersing them into a base fluid (vegetable oil). The thermophysical properties, such as thermal conductivity and viscosity, were studied for various volume concentrations and at a range of temperatures. Experimental results have shown enhancement in thermal conductivity in all cases and also an increase in viscosity. The enhancement in viscosity is similar in all three combinations, as the particle size and shape are almost identical. The enhancement in thermal conductivity is higher in Cu–Zn (50:50), resulting in better enhancement in thermal conductivity due to the Brownian motion of the particles and higher thermal conductivity of the nanoparticles incorporated.