Thermal properties of alumina–MWCNTs composites

Alumina–multi-wall carbon nanotubes composites were prepared using a new approach. This process comprises functionalization MWCNTs by acid treatment, stabilization of alumina–MWCNT dispersion with subsequent freezing was used, which resulted in formation of granulated powder with homogeneous distribution of MWCNTs. The ceramic composites were prepared by hot pressing and rapid hot pressing at 1550 °C using these granulated powders. Relative densities, microstructural analysis, Raman spectroscopy, heat capacity as well as thermal diffusivity measurements of composite prepared by hot press and rapid hot press has been studied. Our results show that sintering alumina–MWCNT granulated powder by rapid hot press is effective way how to reach nearly fully dense composite up to 12.5 vol.% of MWCNTs. Relative density of alumina–MWCNT composite with 10 vol.% of MWCNTs in case of composite prepared by rapid hot press was 97.3% of theoretical density whereas in case of composite with same content of MWCNTs prepared by hot press relative density was 79.5%. Thermal diffusivity of composite sintered by rapid hot press and hot press decrease with increasing content of MWCNTs and increasing measuring temperature up to 400 °C. Thermal diffusivity of composites prepared by rapid hot press, which have higher density than composite prepared by hot press, is slightly higher. Thermal conductivity of composites prepared by rapid hot press decrease with increasing content of MWCNTs from 27.8 to 16.7 W/m K and in case of composite prepared by hot press from 24.6 to 7.8 W/m K. This is probably due to the phonon scattering of incorporated MWCNTs in alumina matrix and their intrinsic defects.