Silicon nitride foams with uniform pore structure prepared by using protein foaming method with a planetary ball-milling foaming route

A planetary ball-milling foaming route was employed by the protein foaming method for preparing silicon nitride (Si 3 N 4 ) foams. In comparison with the commonly used tumbling foaming route of protein foaming method, pores of the Si 3 N 4 foams fabricated by this new foaming route are more uniform in size distribution and the pores pack more compact. Furthermore, effects of the rotating speed on the structure and the property of the Si 3 N 4 foams fabricated by this new foaming route were investigated. It was indicated that the average pore size decreased with the rotating speed, whereas the count of windows on the walls increased with the rotating speed. Moreover, the windows were found to have a negative influence on the phase transformation of Si 3 N 4 from α phase to β phase.