Thermal conductivity enhancement of AlN/PDMS composites using atmospheric plasma modification techniques

In this study, the atmospheric plasma process (APP) was used to modify the surface of aluminum nitride (AlN) powder with different particle sizes and morphologies (non-spherical and spherical), using modified AlN powder as fillers for polydimethylsiloxane (PDMS) to form AlN/PDMS composites. The functional groups on the surface of the AlN powder, before and after APP modification of the AlN powder, were examined using a Fourier transform infrared spectrometer (FTIR). The thermal conductivity (k) of the sample was measured using a k measurement apparatus that conformed to the ASTM D5470-06 standard. In addition, the k of the sample with the highest k was further increased by the semi-curing technique. Finally, the applicable temperature range of the semi-cured sample was measured by thermogravimetric analysis (TGA). The results show that APP-modified AlN powder can be combined with a C–H functional group to make an APP-modified AlN powder with better adhesion to increase the k of the samples. The filling weight percentage of AlN powder had a nonlinear proportional relationship with k, and the spherical particles enhanced the k of the sample better than the non-spherical particles. The k values of 75 wt% APP-modified non-spherical AlN/PDMS composites and 80 wt% APP-modified spherical AlN/PDMS composites were 1.60 times and 1.48 times higher than unmodified AlN/PDMS composites, respectively. Semi-cured 80 wt% APP-modified spherical AlN/PDMS composites had a k of 4.19 W/mK and an enhancement of 1.4 times that compared with fully cured composites. Furthermore, semi-cured 80 wt% APP-modified spherical AlN/PDMS worked safely within the range of 200 °C and had a superior k.