Non hydrolizable aluminum nitride powders surface modified by silicic acids

Abstract

Aluminum nitride (AlN) ceramic is a material with many excellent properties, such as high thermal conductivity and outstanding electrical insulation, but the required raw powders are easily hydrolyzed that affects the performance after sintering. Therefore, surface modification of AlN powder is essential. In this study, the raw AlN powders were treated in an ethanol with silicic acid (H2SiO3) by heating and stirring at 80 °C. The treated powders will not be hydrolyzed under high temperature and stirring, which was confirmed by pH measurement (pH), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Transmission Electron Microscope (TEM) etc. methods. The XRD spectra proves that the characteristic crystalline peaks of the treated AlN powders after impregnating warm aqueous solution over twenty days are still the same as those of the raw AlN powders. The pH value of the suspension with treated AlN powders remains constant at 7.0–8.0 in 80 °C/90 °C water for 72 h. FTIR and TEM analysis shows that a 3–18 nm protective layer of Si–O–Si wrapped on the surface of the AlN powders. These results directly indicate that the AlN powders treated with H2SiO3 have good hydrolysis resistance. Moreover, the relative density and thermal conductivity of the ceramics sintered by the treated AlN powders can reach 97.21% and 144.505 w/(m· K), respectively.