Material science
Sajede Aghasi; Seyed Hassan Jafari; Mahdi Golriz
Abstract
One of the methods for improving thermal conductivity of epoxy adhesives is the incorporating of conductive ceramic, metal or carbon fillers. As the main goal of this research, is to improve thermal conductivity of epoxy resin and keep its electrically insulating property, Alumina (Al2O3) ceramic filler, ...
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One of the methods for improving thermal conductivity of epoxy adhesives is the incorporating of conductive ceramic, metal or carbon fillers. As the main goal of this research, is to improve thermal conductivity of epoxy resin and keep its electrically insulating property, Alumina (Al2O3) ceramic filler, individually and in combination with Boron Nitride (BN) ceramic filler with high thermal conductivity and electrical resistivity. Scanning Electron Microscopy (SEM) observations showed a good dispersion and an acceptable connection between fillers. Thermal diffusivity measurements revealed that by incorporating conductive ceramic fillers, either individually or in combination with each other, regardless of the type of the hardener, thermal diffusivity would increase as a result of the formation of thermal conductive networks. Although, in hybrid system, because of bridging effect between particles, thermal diffusivity will notably increase. Therefore, using hybrid system of Alumina/BN along with long chain polyamine curing agent is a suitable choice for the preparation of thermally conductive yet electrically insulating epoxy adhesives in space industries. The results show that the thermal conductivity of hybrid system of Alumina/BN have been raised to 1.7 (W/mK) instead of 0.4 (W/mK) which is belong to pure epoxy system. The most important point of this work is that the good thermal conductivity obtained by kept of mechanical properties, dielectric constant, as well as lap shear strength of Alumina/BN hybrid system meet all acceptable range of thermal conductive adhesive for space application.
Material science
shahab khameneh asl; reza golzarian; behnam salahimehr; ali fardi
Abstract
Platinum nanoparticles are widely used in the oil and gas industries, electronics, space tools, pharmaceutical industries, biomaterials and etc.Platinum catalysts are more active and selective than the other catalysts. In this regard, the preparation of a suitable alumina catalyst base and more effective ...
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Platinum nanoparticles are widely used in the oil and gas industries, electronics, space tools, pharmaceutical industries, biomaterials and etc.Platinum catalysts are more active and selective than the other catalysts. In this regard, the preparation of a suitable alumina catalyst base and more effective coating of platinum particles are presenting an important role in increasing the quality and efficiency of the catalyst. The purpose of this research is to prepare a high Specific surface area alumina base via aluminum anodizing and coating them with platinum particles. As a result, two steps of the work have been carried out, which are as follows: anodizing aluminum in an oxalic acid solution and optimizing its parameters to reach alumina nanotubes with controlled diameter, thickness and height. Subsequently, the research is resumed using scanning electron microscopy and data related to the special surface.In the next step, different amounts of platinum coatings using a suitable metal salt and solvent is deposited via an optimized electrochemical method.Finally, nanotubes with a diameter, thickness, height of about 60 nm, 20 nm, 15 μm, respectively were produced as the catalyst base.The optimized parameters include: applied voltage of 40 v DC and temperature range of 0-4 °C and the duration of anodizing for 7 h.The platinum coat array is masked on the substrate lithographically. The Samples are prepared using H2PtCl6.6H2O under an electrochemical 12V AC of 200 Hz with a sinusoidal waveform in a solution at a concentration of 8 mM in 150 seconds.The specific surface area was 3.16 m2/g and the absorbed gas volume was 0.728 cm3/g, absorption and desorption isotherm had a hysteresis suitable for catalytic activity.This knowledge was acquired in order to optimize the synthesis and coating conditions of the substrate with a suitable coating for catalytic applications and thermal knives.
