Effect of rotating speed during foaming procedure on the pore size distribution and property of silicon nitride foam prepared by using protein foaming method

Silicon nitride (Si3N4) foams were prepared by using protein foaming method with varying rotating speed during the foaming process. The pore sizes of these as-fabricated Si3N4 foams were measured by means of the Image Pro Plus software and the as-measured pore size date was analyzed statistically by using the SPSS Statistics software. It was indicated that the pore size data of the as-prepared Si3N4 foams abided by the logarithmic normal distribution. With the increase of rotating speed, the pore structure of Si3N4 foam became more uniform. This was because of the enhancing shear stress at higher rotating speed, which increased frequency of collision between bubbles in foamed slurry and hence improved the uniformity of bubble size distribution. The porosity, density and flexural strength of these as-prepared Si3N4 foams fluctuated in a small range, indicating that the rotating speed had limited influence on these properties.