Fabrication of Al2O3/ZnO and Al2O3/Cu Reinforced Silicone Rubber Composite Pads for Thermal Interface Materials

Thermal interface materials (also known as thermal pads) are widely used as a crucial part to dissipate heat generated in miniaturized and integrated electronic components. Here, we systematically investigated the effects of small ceramic and metallic powders in rubbery thermal composite pads with a high content of aluminum oxide filler on the thermal conductivity of the composite pads. We optimized the compositions of aluminum oxide fillers with two different sizes in a polydimethylsiloxane (PDMS) matrix for rubbery composite pads with a high thermal conductivity. Based on the optimized compositions, zinc oxide powder or copper powder with an average size of 1 μm was used to replace 5 μm-sized aluminum oxide filler to examine the effects of the small ceramic and metallic powders, respectively, on the thermal conductivity of the composite pads. When zinc oxide powder was used as the replacement, the thermal conductivity of the rubbery composite pads decreased because more air bubbles were generated during the processing of the mixed paste with increased viscosity. On the other hand, when the copper powder was used as a replacement, a thermal conductivity of up to 2.466 W/m·K was achieved for the rubbery composite pads by optimizing the mixing composition. SEM images and EDS mapping confirmed that all fillers were evenly distributed in the rubbery composite pads.

Bentonite-based composites with ceramic and metallic powders additions for use as filters

This paper represents the study of bentonite matrix composite reinforced with ceramic (Al2O3 and SiC) and metallic (Al and Fe) particles for the production of filters. Ceramic powders were used to generate pores and metallic particles to control the pore size (to finish them). These materials were added to composites in two stages. In the first stage, the ceramic particles (Al2O3 and SiC) were added to the bentonite matrix, thus obtaining two types of composites. In the second stage, for each type of composite, metallic powders of Al and Fe were added. The composites was prepared by mixing the components, cold pressing for compaction in cylindrical samples and, at the end, sintering at 1250°C. The samples thus produced underwent studies by optical and electron microscopy, diffractometry, dilatometry and thermal analysis and tests to determine the compressive strength and the porosity. Thus, there was obtained useful information regarding the behaviour and impact of the reinforcing materials in the process of producing the composites, and on their impact on the final properties of the composites produced.

Development of Cu Coating on Ceramic Substrates by Low Pressure Cold Spray and its Deposition Mechanism Analysis

Cold spray (CS) is a solid-state deposition technique of micron-sized metallic powder in an ultra-high velocity gas using a de Laval nozzle. CS is a unique deposition technique due to its use of relatively lower gas temperatures in comparison to other thermal processes. Consequently, high-temperature oxidation and phase transformations of deposited powders are largely restricted while the operating cost of CS is much lower than that of other thermal processes. Generally, the low pressure cold spray (LPCS) technique is used for the deposition of metallic powders on metallic substrates, while only a few studies of metallic particle deposition on ceramic substrates have been conducted, and it was found that the deposition of metallic powders on ceramic substrates was quite difficult. In this study, improved LPCS deposition of copper coatings on zirconia substrates was investigated. It is known that deposition of a metallic powder on a ceramic substrate is difficult due to the differences in material bonding and several properties of the two materials. These difficulties in LPCS deposition were solved using three different approaches, namely 1) use of copper and aluminum composite powders and 2) laser pre-treatment and 3) laser texturing of zirconia substrates. It was found that pure copper powder coatings on the as-received and various treated substrates were delaminated in the interface as expected. However, the deposition was improved for all substrates by using the copper and aluminum composite powder. While the laser pre-treated substrate was not effective for the deposition of the copper and aluminum composite powder, thick coatings were obtained for the deposition on the laser pre-treated with heat treatment substrate and the laser-textured substrate.

Metal fuels production through the solar carbothermal reduction of magnesia: Effect of the reducing agent

The use of metallic powders as substitute combustion fuels for transportation gains much interest due to their high energetic value, the absence of greenhouse gas emissions, and the ability to...