Papers by Keyword: Porous Silicon Nitride

Abstract: The porous ceramic filter material is the most effective filter materials in the integrated gasification combined cycle. The porous silicon nitride due to its higher mechanical strength, as well as good corrosion resistance, is considered as a promising material in the integrated gasification combined cycle, and it were prepared directly though the SiO₂ and α-Si₃N₄ through carbothermal reduction - pressureless sintering in nitrogen. There was a great lot weight loss in this reaction, so it was expected to create the high porosity materials. The rod-like β-Si₃N₄ grains and uniform pores were formed through changing the content of α-Si₃N₄, SiO₂ and C. So high-performance and porosity controlled porous silicon nitride filter material was obtained. With an increasing in the α-Si₃N₄ content, the weight loss, the linear shrinkage, and the porosity decreased, the flexural strength increased accordingly. The porous silicon nitride filter material with addition of 50wt% α-Si₃N₄ showed a higher aspect ratio β-Si₃N₄ grains and better mechanical properties .

Abstract: Porous silicon nitride (Si₃N₄) ceramics green were prepared by sol-gel and freeze drying processing. Al₂O₃ and MgO were selected as sintering additives. Porous Si₃N₄ ceramics were sintered at 1200~1300 °C. The porosity of porous Si₃N₄ ceramics reached 60~80%, the pore size of porous Si₃N₄ ceramics dried by freeze drying is less than 5μm. Two kinds of pores were formed, including open pores with pore size of 1~5μm and closed pores pore size with the nanometer level. The compression strength of porous Si₃N₄ ceramics was 15~25MPa. Thermal conductivity of porous Si₃N₄ ceramics was 0.08-0.1 W/m·K.

Abstract: The powder of 3molY₂O₃-ZrO₂ as the coating material sprayed on the surface of porous silicon nitride which porosity is more than 50% by Plasma Sprayed. The microstructure of the coating and the matrix was analysised. The performance change of porosity, strength and insulation, before and after spray, were researched.

Abstract: Hole-sealing coating was fabricated on the porous silicon nitridesubstrate by sol-gel method, with Li2O-Al2O3-SiO2 as the basic materials and other additives were added. The morphology of the coating was tested by scanning electron microscope(SEM). The density,water absorption and porosity of porous silicon nitride before and after coating were tested by Archimedes method.The bending strength was tested by universal testing machine．The results indicated that the water absorption of porous silicon nitride was decreaced by 93.73% to 96.74%, the bending strength of porous silicon nitride was increaced by 8.21％ to 15.56％.

Abstract: Porous silicon nitride ceramics with high-porosity were fabricated by carbothermal reduction reaction between silicon dioxide and carbon. The influences of carbon sources on microstructure and phase composition of the samples were studied. The result showed that the resultant porous silicon nitride ceramics using nano-meter carbon powder (C(n)) had finer microstructure, more uniform pore structure than those using activated carbon powder (C(a)). In order to illuminate the reaction and growth mechanism of b-Si3N4 grains, a series of intermediate sintering processes were investigated. X-ray diffractometry showed a difference in phase composition for the samples using the different carbon sources.

Abstract: In this study, the porous silicon nitride ceramics with low permittivity was prepared by decomposition reaction of Si2N2O. The effect of sintering temperature on the properties of composites was investigated. The results show that the sintering process of porous silicon nitride ceramics is liquid crease-densititive-crease gas in high temperature-forming close pore-break of close pores and crease open pores. The density is 0.9-2.44 g/cm3, the porosity of sample varies from 0-47%, and the permittivity can be well controlled from 2.2 to 4.8.