Compound To Add The Preparation Of Si <sub> 3 </ Sub> N <sub> 4 </ Sub> Porous Ceramic Materials

The paper discussed that Silicon-nitride based porous ceramic was prepared by reaction-sintering and pressless-sintering with the powder of Si as raw material, Al2O3,Y2O3 Fe and Al as sintering aids, carbon and urea as pore-forming agent. In the paper, the effect of some important factors including pore-forming material, sintering aids, forming pressure on XRD and the pore properties (including apparent porosity, pore size, pore structure) of Silicon-nitride based porous ceramics were researched and analyzed systematically. Moreover, some effective methods in accurately controlling pore properties of porous ceramics were proposed. In order that pore properties of Silicon-nitride based porous ceramics are controlled accurately and excellent functions were obtained.The result showed that Silicon-nitride based porous ceramic was fabricated by the complex technology. The samples of Al2O3 and Y2O3 as sintering aids and the samples of Al2O3, Y2O3 Fe and Al as sintering aids are composed of β- Si3N4 and a-Si3N4 . The effect of adding Al2O3, Y2O3 Fe and Al as sintering aids were obvious.With the content of pore-forming agent increasing, apparent porosity and average pore size were increased. Si3N4 porous ceramics with average pore size from 16μm to 22μm were obtained by adding pore-forming agent (carbon and urea) in 25%. The pore of samples adding carbon distributed uniform, which apparent porosity changed sharper than apparent porosity adding urea and average pore size smaller than that adding urea.With the condition of only adding oxidization as sintering aids and the content of Al2O3, Y2O3 in 20%, average pore size change from 14.87μm to 16.53μm. The pore of samples adding Y2O3 distributed uniform.With the condition of the content of Al2O3(2%), Y2O3(8%), Fe(1%), Al(1%), apparent porosity increased and pressing strength decreased with the content of carbon increasing. With the same of apparent porosity, increasing forming pressure can increase pressing strength.In addition, the hardness and flexural strength of Si3N4 porous ceramics were tentatively discussed.