Thermal and Dielectric Characteristics of Aluminum Nitride/HTV Silicone Composites

The study describes the use of nano aluminum nitride (AlN) in developing thermally conductive and electrically insulating materials. An experimental approach is followed, starting with the hydrophobic surface treatment of nanofillers using hexamethyldisilazane (HMDS). Transmission electron microscope (TEM) and X-ray diffraction analysis (XRD) are used to confirm the nanofiller presence and gain insight regarding the filler shape, dimensions, and phase. Energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), and XRD analyses revealed the coexistence of aluminum oxide in traces along with AlN. XRD patterns revealed no change after surface modification and confirmed the presence of an amorphous functionalized layer. The protocol for composite compounding is described in detail. SEM analysis of composites revealed a moderate degree of dispersion with localized pockets of agglomeration. Furthermore, the TEM analysis performed gave insight into the dispersion of nanofillers. Finally, differential scanning calorimetry (DSC) analysis is performed to understand the effects of nano AlN on glass transition, melting point, and crystallization temperatures. An interesting pattern of increase in glass transition temperatures with nanofiller loading levels is discussed, drawing attention to the aggregated filler effect and the disentangling of silicone chains with increasing interfacial interaction. Thermogravimetric analysis (TGA) revealed an early onset of degradation with an increase in nano AlN loading levels. Thermal conductivity increased with nanofiller loading levels, peaking at 3 phr by weight. Dielectric studies of breakdown strength and frequency-domain spectroscopy from 1 MHz to 1 kHz are studied under different thermal points. The results are presented and discussed here.