Hydrolysis Behavior And Anti-hydrolysis Properties Of AlN Powders

AIN ceramic has high thermal conductivity, small dielectric constant and dielectric loss, good mechanical properties, non-toxic, and can bear high temperature and corrosion, and it is a new generation of ideal material for semiconductor packaging substrates and electronic devices. But the performances of AIN ceramic are affected by the hydrolysis of AIN powders in moist air. To improve the hydrolysis behavior of sub-micron and nano-AIN powders, the hydrolysis of behavior of sub-micron and nano-AIN powder was researched in this paper.By studying the hydrolysis behavior of the 500nm and 40nm AIN powders at different temperatures, it is found that the hydrolysis rate relates with the particle size of AIN powders and temperature. The hydrolysis rate is increased with the increase of temperature and the decrease of particle size. X-ray diffraction analysis showed that the hydrolysis products were Al(OH)3 and AlOOH. Al(OH)3 dominants at room temperature, but AlOOH dominants at high-temperature. TEM showed that the hydrolysis occurs on the steps of the AIN powders surface and forms amorphous phase at step edges.It is found that the anti-hydrolysis performance of AIN powders can be improved by phosphoric acid pickling. The AlN powders after phosphoric acid pickling can not occur hydrolysis for at least 230h at room temperature. The protection of phosphoric acid affects the surface of AIN powders. The phosphoric acid passivates the surface of AIN powders and then improves the anti-hydrolysis ability. The protection relates with particle size, and the protection for nano-particle AIN powders is more effective. XRD showed that no new phase produces after phosphoric acid pickling.It is shown that AIN starts to be oxidized at 750℃and the oxidation degree increases with increasing temperature on the range of 750-1050℃. The improvement of anti-hydrolysis ability by heat treatment at different temperatures for AIN powders is different with particle size. For 40nm AIN powders heat treated at 850-1050℃, the hydrolysis would be inhibited because of the formation of the compact Al2O3 film. 850-950℃is most appropriate heat treatment temperature for 40nm AIN powders because 1050℃is too high to form too much Al2O3 film. Heat treatment at 850℃is more suitable for 500nm AIN powder.