scholarly journals Analysis of the Electrical and Thermal Properties for Magnetic Fe3O4-Coated SiC-Filled Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3028
Author(s):  
Jiale Wu ◽  
Yiran Zhang ◽  
Yangzhi Gong ◽  
Kun Wang ◽  
Yun Chen ◽  
...  
Keyword(s):  
Electronic Device ◽  
Breakdown Strength ◽  
Favorable Effect ◽  
Maximum Enhancement ◽  
Improvement Rate ◽  
Treatment Methods ◽  
Heat Transfer Efficiency ◽  
Comprehensive Properties ◽  
Polar Groups ◽  
Maximum Improvement

Orderly arranged Silicon carbide (SiC)/epoxy (EP) composites were fabricated. SiC was made magnetically responsive by decorating the surface with iron oxide (Fe3O4) nanoparticles. Three treatment methods, including without magnetization, pre-magnetization and curing magnetization, were used to prepare SiC/EP composites with different filler distributions. Compared with unmodified SiC, magnetic SiC with core-shell structure was conducive to improve the breakdown strength of SiC/EP composites and the maximum enhancement rate was 20.86%. Among the three treatment methods, SiC/EP composites prepared in the curing-magnetization case had better comprehensive properties. Under the action of magnetic field, magnetic SiC were orderly oriented along the direction of an external field, thereby forming SiC chains. The magnetic alignment of SiC restricted the movement of EP macromolecules or polar groups to some extent, resulting in the decrease in the dielectric constant and dielectric loss. The SiC chains are equivalent to heat flow channels, which can improve the heat transfer efficiency, and the maximum improvement rate was 23.6%. The results prove that the orderly arrangement of SiC had a favorable effect on dielectric properties and thermal conductivity of SiC/EP composites. For future applications, the orderly arranged SiC/EP composites have potential for fabricating insulation materials in the power electronic device packaging field.

scholarly journals Lower periorbital area treatment with Restylane Vital Skinbooster

2016 ◽  
Vol 1 (3) ◽  
Author(s):  
Denis Souto Valente ◽  
Rafaela Koehler Zanella ◽  
Ângelo Syrillo Preto Neto ◽  
Sibelie Souto Valente ◽  
Felipe Laranjeira
Keyword(s):  
Superficial Layer ◽  
Self Assessment ◽  
Maximum Enhancement ◽  
Improvement Rate ◽  
High Satisfaction ◽  
Mild Improvement ◽  
Before And After ◽  
High Satisfaction Rate ◽  
Maximum Improvement ◽  
Autonomous Observers

<p>Facial aging along the periocular area has led to the development of new non-surgical therapies. The lower periorbital area is a vital region for facial rejuvenation and several procedures have been studied to treat it, especially procedures with dermal fillers for volume rebuilding. This manuscript aims to describe a filling technique with hyaluronic acid (HA) along the superficial layer of the lower periorbital area, presenting its effectiveness and safety. Our assessment was made by autonomous observers with pictures of before and after treatment, rated from 0 (no enhancement) to 100 (maximum enhancement). Patients’ self-assessment was also performed using a visual analog scale (VAS) based on a 100-mm ruler affording a 0–100 rating. Thirty patients were enrolled in this study. The autonomous observers’ evaluation presented a 78.4 mean improvement rate. Patients’ self-assessments after the treatment were 0% reporting no improvement, 6.7% mild improvement, 23.3% moderate improvement, 66.7% great improvement, and 3.3% maximum improvement. Restylane Vital Skinbooster infiltration at the lower periorbital area proved to be a safe treatment. The described technique is also simple to execute, has a low rate of complications, and produces a high satisfaction rate.</p>

scholarly journals RETROFITTING OF SELF COMPACTING RC HALF JOINTS WITH INTERNAL DEFICIENCIES BY CFRP FABRICS

2020 ◽  
Vol 82 (6) ◽  
pp. 49-62
Author(s):  
Qasim M. Shakir ◽  
Baneen B. Abd
Keyword(s):  
Shear Failure ◽  
Load Capacity ◽  
Slenderness Ratio ◽  
Relative Displacement ◽  
Dissipated Energy ◽  
Maximum Enhancement ◽  
Maximum Improvement ◽  
Overall Performance ◽  
Reference Specimens ◽  
Ductility Ratio

An experimental study has been conducted to scrutinize the response of reinforced self-compacting concrete half joints upgraded with CFRP strips. Fourteen RC half joints have been tested. Two values of shear slenderness ratio were considered, namely 1.5 and 1.0. Two beams have been treated as reference specimens (with the design steel), and the twelve other beams were casted with deficiency in steel of the hanger and the extended end regions relative to the control beams. Eight of these beams have been strengthened with different arrangements to discuss the influence of shear slenderness ratio and strengthening arrangement on the overall performance of such joint elements. It is found that the reduction in nib-main steel by about 50% results in decreasing load capacity by about 36% and 15% for shear slenderness ratio of 1.5 and 1.0 respectively. Also, it is found that the orthogonal arrangement combined with inclined strips yielded the best results in terms of preventing the diagonal shear failure at the re-entrant corner with maximum enhancement in load capacity by 18%. In addition, the maximum improvement in failure load when strengthening hanger region by such alignment was about 23%. Results also revealed that the effective stiffness and ductility ratio enhanced with reducing shear span of a half joint and may be adopted as a good indicator to evaluate the suitable strengthening scheme. Moreover, it is concluded that the relative displacement method for predicting the ductility ratio is more applicable than that based on the dissipated energy.

scholarly journals Improvement of Dielectric Breakdown Performance by Surface Modification in Polyethylene/TiO2 Nanocomposites

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3346 ◽  
Author(s):  
Weiwang Wang ◽  
Shengtao Li
Keyword(s):  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Interface Region ◽  
Insulation System ◽  
Polar Groups ◽  
Deep Traps ◽  
Relaxation Polarization ◽  
Surface Modified ◽  
Shallow Traps ◽  
Surface Chemical Modification

Dielectric breakdown is a significant property for the insulation system in high voltage power equipment. This paper is dedicated to the improvement of dielectric breakdown by surface-functionalized nanoparticles in low-density polyethylene (LDPE). Prior to the preparation of LDPE/TiO2 nanocomposites, the nanoparticles were surface modified by the silane coupling followed by the chemical reaction process. Results of Fourier transform infrared spectroscopy (FTIR) indicated that some polar groups and chemical bonding were introduced on the surface of TiO2 nanoparticles. A reduction of dielectric permittivity was observed at low nanoparticle loading (<2 wt%) samples, which responded to the restriction of the molecular chain in the interface region. High nanoparticle loadings (2 wt%, 5 wt%, 10 wt%) introduced an obvious relaxation polarization. The trap parameters detected by the thermally stimulated current (TSC) method indicated that the deep traps were introduced by small amounts of nanoparticles (≤2 wt%), while more shallow traps occurred in high loading (5 wt%, 10 wt%) samples. Meanwhile, the increase of breakdown strength at low loading samples were closely related to the deep traps, which was ascribed to the interface region by surface chemical modification.

Nanofluids for Thermal Performance Improvement in Cooling of Electronic Device

2013 ◽  
Vol 832 ◽  
pp. 218-223 ◽  
Author(s):  
S.S. Khaleduzzaman ◽  
Saidur Rahman ◽  
Jeyraj Selvaraj ◽  
I.M. Mahbubul ◽  
M.R. Sohel ◽  
...  
Keyword(s):  
Heat Flux ◽  
Performance Improvement ◽  
Heat Dissipation ◽  
Electronic Device ◽  
High Heat ◽  
Constant Heat Flux ◽  
Microchannel Heat Sink ◽  
Conductivity Enhancement ◽  
Maximum Improvement ◽  
Steady Laminar

Nanofluid is a promising coolant for high-heat dissipation electronics device or system. The effect of nanofluids as thermal performances on a rectangular shape microchannel heat sink (MCHS) is analytically studied. Al2O3, SiC, and CuO nanoparticles dispersing in water were considered for analysis. A steady, laminar, and incompressible flow with constant heat flux was assumed in the channel. Nanofluids with concentrations of 0.5 to 4.0 vol. % were analyzed at two different inlet velocities of 0.5 m/s and 3.0 m/s. The results showed that highest thermal conductivity enhancement was 12.45% by using SiC-water nanofluids. In the case of Al2O3-water and CuO-water nanofluids maximum improvement were 11.98% and 11.36%, respectively for 4.0 vol. % of nanoparticle concentration. Furthermore, nanofluids as a coolant instead of water showed a highest improve of heat flux 8.51% for water-CuO, and 6.44% and 5.60% increase for Al2O3-water and SiC-water, respectively. The maximum pumping power found 0.33 W at 3 m/s and 0.0091 W at 0.5 m/s for the same concentration of 4.0 vol. % for all of these nanofluids.

scholarly journals Significantly Improved Electrical Properties of Photo-Initiated Auxiliary Crosslinking EPDM Used for Cable Termination

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2083 ◽  
Author(s):  
Zhong-Yuan Li ◽  
Wei-Feng Sun ◽  
Hong Zhao
Keyword(s):  
Electric Field ◽  
First Principles ◽  
Electric Field Distribution ◽  
Breakdown Strength ◽  
First Principles Calculations ◽  
Carbonyl Groups ◽  
Trapping Mechanism ◽  
Polar Groups ◽  
Lower Temperature ◽  
Electrical Materials

In order to achieve high quality electrical materials for cable terminations, the crosslinked ethylene-propylene-diene monomer (EPDM) materials, with adequate breakdown strength, appropriately increased conductivity and are developed by employing auxiliary crosslinker and ultraviolet (UV) photoinitiated crosslinking technique. The characteristic cyclic anhydrides with coupled carbonyl groups are utilized as auxiliary crosslinkers to promote crosslinking efficiency and provide polar-groups to EPDM molecules in UV-initiated crosslinking processes, which can be effectively fulfilled in industrial cable production. The results of infrared spectroscopy show that the auxiliary crosslinkers have been successfully grated to EPDM molecules through UV initiation process. The conductivity of EPDM increases after individually utilizing three auxiliary crosslinkers to EPDM at various temperatures of cable operations, by which the highest conductivity has been acquired by grafting N.N-m-phenylene dimaleimide. The first-principles calculations demonstrate that some occupied local electronic-states have been introduced in the band-gap of the EPDM crosslinked by N.N-m-phenylene dimaleimide (EPDM-HAV2), which can be thermally excited from valence band to conduction band at lower temperature or in higher density, leading to augmentation in electrical conductivity. Meanwhile, the breakdown strength achieves a significant improvement in consistency with the theoretical estimation that deeper hole-traps can be introduced by auxiliary-crosslinking modification, and will consequently increase breakdown strength through the trapping mechanism of space charge suppression. in relation to the appropriately increased conductivity, in combination with persistent breakdown strength, the finite element simulations of the electric field distribution in EPDM cable terminations suggest that the effectively homogenized electric field at the root of stress cone will be realized for EPDM-HAV2. The present study offers a fundamental strategy to ameliorate EPDM materials in the application of insulated cable accessories.

Impact of Stabilizer on In Situ Formation of Ag Nanoparticles in Polyvinylidene Fluoride (PVDF) Matrix

MRS Advances ◽  
2019 ◽  
Vol 4 (38-39) ◽  
pp. 2103-2108 ◽  
Author(s):  
Maryam Sarkarat ◽  
Amira B. Meddeb ◽  
Sridhar Komarneni ◽  
Zoubeida Ounaies
Keyword(s):  
Ag Nanoparticles ◽  
Polyvinylidene Fluoride ◽  
Breakdown Strength ◽  
Dimethyl Formamide ◽  
Transition Electron Microscopy ◽  
No Formation ◽  
Polar Groups ◽  
Vis Spectroscopy ◽  
Pvdf Matrix

Abstract:In situ synthesis of Ag nanoparticles in polyvinylidene fluoride (PVDF) was investigated using different stabilizers such as 3-aminopropyltrimethoxysilane (APS) and 1-dodecanethiol (thiol). Although PVDF is a matrix, it also functions as a stabilizer. Results of UV-vis spectroscopy showed that when APS or PVDF was used, Ag nanoparticles were formed. Yet no formation occurred when thiol was used due to the complexation of Ag+ ions by thiol. Polar groups on stabilizers has an important effect on complexation process. APS, a nitrogen-based ligand, has hard base character inhibiting the complexation between Ag+ and APS. Consequently, Ag+ ions are reduced to Ag nanoparticles in N,N dimethyl formamide (DMF), which acts as a solvent and reducing agent. Transition Electron Microscopy (TEM) image showed a uniform distribution of spherical Ag nanoparticles in PVDF matrix in the presence of APS. The electrical properties of flexible nano-metal polymer were tested and the highest improvements in breakdown strength and energy density of 33 and 58 %, respectively were measured with 0.05 wt.% Ag content and APS as a stabilizer.

Influence of Nanoparticle Surfaces on the Electrical Breakdown Strength of Nanoparticle-Filled Low-Density Polyethylene

2004 ◽  
Vol 19 (3) ◽  
pp. 857-863 ◽  
Author(s):  
Dongling Ma ◽  
Richard W. Siegel ◽  
Jung-Il Hong ◽  
Linda S. Schadler ◽  
Eva Mårtensson ◽  
...  
Keyword(s):  
Surface Modification ◽  
Surface Water ◽  
Electron Scattering ◽  
Breakdown Strength ◽  
Electrical Breakdown ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Polar Groups ◽  
The Matrix ◽  
Electrical Breakdown Strength

The electrical breakdown strength of TiO2nanoparticle-filled low-density polyethylene (LDPE) nanocomposites was investigated. It was found that the surface water on the nanoparticles played a very important role in determining the breakdown strength. The breakdown strength at 63.2% cumulative failure probability (E0) for the composites filled with dried nanoscale TiO2was similar to that of neat LDPE and 50% higher than that for the samples filled with as-received nanoscale TiO2. This increase was due to a better dispersion, a better interface, and a morphology change of the matrix. It was also found that surface modification of nanoscale TiO2had a significant influence on the breakdown strength.N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS)-coated TiO2-filled samples showed about 40% higherE0than that of uncoated, as-received TiO2-filled samples. This was mainly due to enhanced electron scattering because of the presence of polar groups in AEAPS.

Electronic Cone Illumination with the Conventional Transmission Electron Microscope

1977 ◽  
Vol 35 ◽  
pp. 72-73
Author(s):  
William Krakow
Keyword(s):  
Electronic Device ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Hollow Cone ◽  
Transmission Electron ◽  
Lissajous Figures ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Diffraction Patterns ◽  
Transmission Microscope

An electronic device has been constructed which manipulates the primary beam in the conventional transmission microscope to illuminate a specimen under a variety of virtual condenser aperture conditions. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. The device has been utilized mainly for the hollow cone imaging mode where the device provides a microscope transfer function without zeros in all spatial directions and has produced high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens.

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