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In this article, silicone rubber (SiR) is filled with industry preferred micro-silica and specialty hexagonal boron nitride (h-BN) nanosheets, by varying the ratio between the two fillers, while keeping the filler to matrix ratio the same in all three composites. The fillers are added to SiR using an electrostatic disperser which aids in homogenizing the filler-polymer mixture by means of shearing force along with elongation. The performance of synthesized silicone composites are evaluated using thermal, erosion resistance, morphological, mechanical, and high-temperature dielectric properties. Addition of as low as 5 wt% h-BN fillers significantly improved the thermal properties; 6%–20% improvement in thermal conductivity and in less than half the weight loss compared to only silica filled composites with laser erosion. The morphological and mechanical analyses showed improved filler dispersion and filler to silicone matrix interaction owing to good filler dispersion achieved through the electrostatic dispersing method. The dielectric properties measured in wide frequency range, between 10−4 and 103 Hz and at elevated temperatures (up to 175 °C) showed a negligible effect of increase in h-BN content. Thus, this article implies that low amounts of h-BN in silica-silicone composites improve thermal conductivity and erosion resistance significantly and not altering the dielectric responses of these hybrid composites even at elevated temperatures. Hence these composites can find applications both in the high voltage industry and as electronic packaging materials. [ABSTRACT FROM AUTHOR]

Nanocrystalline soft magnetic alloy powders produced by heat treating amorphous powders are expected to improve properties and miniaturize dust cores because of their low coercive force H_c and high saturation magnetic flux density B_s. By water atomization process, we successfully obtained quenched Fe-Si-B-P-Cu alloy powders with spherical particle shape. The obtained powders have different average particle sizes of 2.0, 3.0, 5.0, and 8.5 \mum. After annealing at 723 K, the as-quenched alloy powders are crystallized and B_s of the nanocrystalline alloy powders with Fe83.3Si4B8P4Cu0.7 and Fe84.8Si2B10P2Cu1.2 exhibit high B_s of 1.72 and 1.76 T, respectively. Core loss characteristics of the dust cores are found to be dependent on amorphous stability of the as-quenched powders. Thus, the Fe83.3Si4B8P4Cu0.7 nanocrystalline alloy powder with an average particle size of 3.0 \mum exhibits the best core loss of 1461 kW/m^3 (B_m=50\ mT, f=300\ kHz). [ABSTRACT FROM AUTHOR]