scholarly journals Effect of Al2O3 with Different Nanostructures on the Insulating Properties of Epoxy-Based Composites

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4235
Author(s):  
Yongzhe Tang ◽  
Guanghui Ge ◽  
Yuxia Li ◽  
Liangsong Huang
Keyword(s):  
Thermal Conductivity ◽  
Power Systems ◽  
Mass Fraction ◽  
Breakdown Strength ◽  
Filler Particle ◽  
Volume Resistivity ◽  
Dielectric Constants ◽  
Filler Particle Size ◽  
Mass Fractions ◽  
Insulating Properties

High thermal conductivity insulating dielectrics with good electrical properties have received widespread attention due to the continuous development of power systems and power electronic technologies. In this paper, the effects of differently structured nano alumina fillers on the thermal conductivity and insulating properties of polymer-based composites were studied. It was found that all three types of Al2O3 nano-fillers enhanced the thermal conductivity of the composites, and the thermal conductivity increased more dramatically with increasing filler particle size. It is worth noting that Al2O3 nanowires (NWs) exhibited the most significant improvement in thermal conductivity. The volume resistivity of the composites first increased and then decreased with increasing mass fraction of fillers, and Al2O3 nanoplates (NPLs) showed the most significant improvement in the insulation performance of the composites. The dielectric constants of the composites increased with increasing mass fraction of fillers, while the dielectric losses first decreased and then increased with the same trend, yet the mass fractions of fillers for the three materials were different when the dielectric loss reached a minimum. In addition, all three types of filler increased the AC breakdown strength of the composites, but Al2O3-NPLs showed the most significant improvement on the breakdown performance of the composites.

scholarly journals Variations of thermophysical properties and heat transfer performance of nanoparticle-enhanced ionic liquids

2019 ◽  
Vol 6 (4) ◽  
pp. 182040 ◽  
Author(s):  
Fang-Fang Zhang ◽  
Fei-Fei Zheng ◽  
Xue-Hong Wu ◽  
Ya-Ling Yin ◽  
Geng Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Fraction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Measurement Range ◽  
Maximum Enhancement ◽  
Wide Range ◽  
Mass Fractions ◽  
Classical Models

The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) was investigated as a promising absorbent for absorption refrigeration. To improve the thermal conductivity of pure [EMIm]Ac, IL-based nanofluids (ionanofluids, INFs) were prepared by adding graphene nanoplatelets (GNPs). The thermal stability of the IL and INFs was analysed. The variations of the thermal conductivity, viscosity and specific heat capacity resulting from the addition of the GNPs were then measured over a wide range of temperatures and mass fractions. The measured data were fitted with appropriate equations and compared with the corresponding classical models. The results revealed that the IL and INFs were thermally stable over the measurement range. The thermal conductivity greatly increased with increasing mass fraction, while only slightly changed with increasing temperature. A maximum enhancement in thermal conductivity of 43.2% was observed at a temperature of 373.15 K for the INF with a mass fraction of 5%. The numerical results revealed that the dispersion of the GNPs in the pure IL effectively improved the local heat transfer coefficient by up to 28.6%.

scholarly journals The Effects of Filler Shape, Type, and Size on the Properties of Encapsulation Molding Components

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 98
Author(s):  
Shouyen Chao ◽  
Yowching Liaw ◽  
Jung-Hua Chou
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Coefficient Of Thermal Expansion ◽  
Filler Particle ◽  
Fused Silica ◽  
Molding Compound ◽  
Spherical Silica ◽  
Filler Particle Size ◽  
Size Type ◽  
Better Than

Fillers are essential in the encapsulation molding compound. For three fillers of crystal, spherical, and fused silica, the effects of their size, type, and shape on the viscosity, flow spiral length, thermal conductivity, and coefficient of thermal expansion (CTE) of the compound were explored in this study. The results show that fillers with a larger particle size have a smaller viscosity and flow better; spherical fillers are better than the polygonal ones in this respect. In contrast, both thermal conductivity and CTE increase as the filler particle size increases; the values of these two properties of crystal silica are about twice those of fused silica; the thermal conductivity of polygonal silica is larger than that of spherical silica. On the other hand, the dependence of CTE on the filler shape is insignificant, but is significant to the filler type. The degree of curing of the compound with polygonal silica is also higher than that with either spherical or crystal silica. Namely, curing is affected by both filler type and shape, and can be tuned accordingly to suit specific needs.

Study on High Thermal Conductive BN/Epoxy Resin Composites

2011 ◽  
Vol 105-107 ◽  
pp. 1751-1754 ◽  
Author(s):  
Hui Wang ◽  
Peng Chen ◽  
Jian Sun ◽  
Xiao Jun Kuang ◽  
Zhen Kun Yao
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Dissipation ◽  
Printed Circuit Board ◽  
Filler Particle ◽  
Linear Increase ◽  
Circuit Board ◽  
Composite Matrix ◽  
Sem Image ◽  
Filler Particle Size

In contemporary electronic technology era, the volume of electronic equipment and printed circuit board reduced so dramatically that the requirements of heat dissipation and insulation increase thereafter. In this research, γ-aminopropyltriethoxysilane (KH550)-treated boron nitride (BN) powder was used as a filler to modify epoxy composites. Effects of the BN particle size and concentration on the thermal conductivity of composites were investigated. SEM image showed the treated BN filler dispersed well in the composite matrix. Moreover, the thermal conductivity was enhanced as the BN concentration was increased. Similar phenomenon was also observed when the filler particle size was reduced. Results indicated that with increasing amount of BN addition, the composites’ thermal conductivity showed a nearly linear increase. When the mass fraction of BN was 30% and its particle size was 220 nm, the thermal conductivity reached 3.4 W/(m•k), which was 17 times as high as that of pure EP resin.

scholarly journals Effect of Environmental Temperature on the Insulating Performance of Epoxy/MgO Nanocomposites

2020 ◽  
Vol 10 (20) ◽  
pp. 7018
Author(s):  
Guanghui Ge ◽  
Yongzhe Tang ◽  
Yuxia Li ◽  
Liangsong Huang
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Thermal Properties ◽  
Dielectric Loss ◽  
Epoxy Resin ◽  
Environmental Temperature ◽  
Breakdown Strength ◽  
Volume Resistivity ◽  
Mgo Nanoparticles ◽  
Pure Epoxy

This article reports on the development of nano-MgO/epoxy resin composites with various mass ratios via a solution blending method. The influence of MgO nanofillers on the thermal properties and the effect of environmental temperature on the insulating properties of the composite material were analyzed. The results show that the thermal conductivity of the composites increased with an increasing MgO nanofiller content. Compared with the pure epoxy resin, the thermal conductivity increased by 75% when the content of MgO nanoparticles was 7%. The volume resistivity first increased and then decreased with an increasing doping concentration. The volume resistivity increased by 26.8% in comparison with the pure epoxy resin when the content of MgO nanoparticles was 1%, while its dielectric constant and dielectric loss increased with temperature. In addition, the dielectric constant increased and the dielectric loss first decreased and then increased with an increasing MgO nanoparticle content. Moreover, the MgO composites changed from a glassy to a rubbery state, and the breakdown strength was significantly reduced with an increased temperature. When the temperature was higher than the glass transition temperature, the breakdown strength decreased by 51.3% compared with the maximum breakdown strength at 20 °C. As the content of MgO nanoparticles increased, the breakdown strength of the composite first increased and then decreased. The highest breakdown strength was achieved when the content of MgO nanoparticles was 1%, which was 11.1% higher than that of the pure epoxy resin. It was concluded that the MgO nanofillers can significantly improve the thermal properties of epoxy composites and their insulation performance at high temperatures.

scholarly journals Temperature Effects on the Dielectric Properties and Breakdown Performance of h-BN/Epoxy Composites

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4112 ◽  
Author(s):  
Yongzhe Tang ◽  
Peng Zhang ◽  
Mingxiao Zhu ◽  
Jiacai Li ◽  
Yuxia Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Boron Nitride ◽  
Mass Fraction ◽  
Breakdown Strength ◽  
Hexagonal Boron Nitride ◽  
Glassy State ◽  
Internal Heat ◽  
Heat Accumulation ◽  
Different Temperatures

Epoxy–boron nitride composites are promising insulating materials, and it is highly important to understand their insulating performances at different temperatures with different nano-doping amounts. In this study, we investigated the effects of different mass fractions of epoxy–micron hexagonal boron nitride composites on their thermal conductivity, as well as the effects of temperature and mass fraction on their insulating performances. The results demonstrated that the thermal conductivity of epoxy–micron hexagonal boron nitride composites was superior to that of neat epoxy. The thermal conductivity of epoxy–micron hexagonal boron nitride composites increased with the mass fraction of hexagonal boron nitride, and their dielectric constant and dielectric loss increased with temperature. The dielectric constant of epoxy–micron hexagonal boron nitride composites decreased as the mass fraction of hexagonal boron nitride increased, while their dielectric losses decreased and then increased as the mass fraction of hexagonal boron nitride increased. Due to internal heat accumulation, the alternating current breakdown strength of epoxy–micron hexagonal boron nitride composites increased and then decreased as the mass fraction of hexagonal boron nitride increased. Additionally, as the temperature increased, the composites transitioned from the glassy state to the rubbery or viscous state, and the breakdown strength significantly degraded.

scholarly journals Effect of Alumina Nanowires on the Thermal Conductivity and Electrical Performance of Epoxy Composites

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2126
Author(s):  
Liangsong Huang ◽  
Xitao Lv ◽  
Yongzhe Tang ◽  
Guanghui Ge ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Epoxy Resin ◽  
Mass Fraction ◽  
Breakdown Strength ◽  
Epoxy Composites ◽  
Electrical Performance ◽  
Resin Matrix ◽  
Resin Composites ◽  
Dielectric Performance ◽  
Epoxy Resin Composites

Alumina nanowires (Al2O3-NWs)/epoxy resin composites have been thoroughly studied due to their excellent insulating and dielectric performance. In particular, understanding the effect of nano-alumina with different morphologies on the dielectric performance of composites is of great significance. In this study, Al2O3-NWs with lengths of approximately 100 nm and diameters of approximately 5 nm were prepared and blended with anepoxy resin to form composites, and the effect of the mass fraction of fillers on the thermal conductivity of the composites was investigated. Specifically, the effect of alumina fillers with ananowire structure on the insulating and dielectric performance and breakdown strength of the epoxy composites were analyzed. The influence principle of the interfacial effect and heat accumulation on the dielectric and insulating properties of the composites were described. The results demonstrated that the thermal conductivity of Al2O3-NWs/epoxy resin composites was higher than that of the bare epoxy resin. The thermal conductivity of Al2O3-NWs/epoxy resin composites increased with increasing mass fraction of fillers. When the mass fraction of fillers was 10%, the thermal conductivity of the composite was 134% higher than that of the epoxy resin matrix. The volume resistivity of the composites first increased and then decreased as the mass fraction of fillers increased, while the dielectric constant of the composites increased with increasing mass fraction of fillers and decreasing frequency. The dielectric loss of the composites decreased and then increased as the mass fraction of fillers increased, and it increased with increasing frequency. Additionally, the alternating current breakdown strength of the composites first increased and then decreased withincreasingmass fraction of fillers.

A technique for uranium and plutonium determination using coulometric potentiostatic facility UPK-19 for analysis of mixed-oxide fuel

2020 ◽  
Vol 86 (12) ◽  
pp. 15-22
Author(s):  
N. A. Bulayev ◽  
E. V. Chukhlantseva ◽  
O. V. Starovoytova ◽  
A. A. Tarasenko
Keyword(s):  
Acid Solution ◽  
Mass Fraction ◽  
Background Electrolyte ◽  
Stable State ◽  
Sulfamic Acid ◽  
Oxide Fuel ◽  
Oxidation Current ◽  
Mox Fuel ◽  
Mass Fractions ◽  
Uranium Plutonium

The content of uranium and plutonium is the main characteristic of mixed uranium-plutonium oxide fuel, which is strictly controlled and has a very narrow range of the permissible values. We focused on developing a technique for measuring mass fractions of uranium and plutonium by controlled potential coulometry using a coulometric unit UPK-19 in set with a R-40Kh potentiostat-galvanostat. Under conditions of sealed enclosures, a special design of the support stand which minimized the effect of fluctuations in ambient conditions on the signal stability was developed. Optimal conditions for coulometric determination of plutonium and uranium mass fractions were specified. The sulfuric acid solution with a molar concentration of 0.5 mol/dm3 was used as a medium. Lead ions were introduced into the background electrolyte to decrease the minimum voltage of hydrogen reduction to –190 mV. The addition of aluminum nitride reduced the effect of fluoride ions participating as a catalyst in dissolving MOX fuel samples, and the interfering effect of nitrite ions was eliminated by introducing a sulfamic acid solution into the cell. The total content of uranium and plutonium was determined by evaluation of the amount of electricity consumed at the stage of uranium and plutonium co-oxidation. Plutonium content was measured at the potentials, at which uranium remains in the stable state, which makes it possible to subtract the contribution of plutonium oxidation current from the total oxidation current. The error characteristics of the developed measurement technique were evaluated using the standard sample method and the real MOX fuel pellets. The error limits match the requirements set out in the specifications for MOX fuel. The technique for measuring mass fractions of uranium and plutonium in uranium-plutonium oxide nuclear fuel was certified. The relative measurement error of the mass fraction of plutonium and uranium was ±0.0070 and ±0.0095, respectively. The relative error of the ratio of the plutonium mass fraction to the sum of mass fractions of uranium and plutonium was ±0.0085.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

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