Preparation of Si₃N₄ Foam Ceramics with Nest‐Like Cell Structure by Particle‐Stabilized Foams

Abstract

Silicon nitride, Si 3 N 4 foam ceramics were prepared by particlestabilized foams, and the stabilization of Si 3 N 4 foams and the performance of Si 3 N 4 foam ceramics were investigated. The Si 3 N 4 particle-stabilized foams had high stabilization, the dried green bodies had little shrinkage, and the structure of dried green body surface had no macro-pores and cracks. The Si 3 N 4 foam ceramics with nest-like cell structure were obtained, nest pores were jointed by elongated rod-shaped b-Si 3 N 4 grains with aspect ratio of 30 or so, pore distribution was uniform, the average pore size was about 16 lm, and the flexural strength was in the range of 3.8 to 77.2 MPa when porosity varied from 82.1% to 60.6%.

Catalytic reduction of nitric oxide by carbon monoxide over coal gangue hollow ball

“…The preparation process of coal gangue hollow ball with open pores includes the following steps: coal gangue is smashed into 0.1-10 μm; the powders are mixed with water, Y 2 O 3 sintering additive and carboxymethyl cellulose dispersing agent (CMC) to make slurry by mechanical stirring for 12 h, followed by the gradual addition of dissolved propyl gallate/TritonX-114 in the surry, and the suspension foam surry is prepared [14]; the stable foam slurry is rapidly atomized and dried, and then dry coal gangue hollow balls are prepared; the dry sphere is sintered at 1223 K under oxidizing condition for 2 h, and the microstructures are shown in Fig. 1.…”

Preparation of porous Si3N4 ceramics via tailoring solid loading of Si3N4 slurry and Si3N4 poly-hollow microsphere content

“…), which is attributed to their unique properties such as low density, high porosity, acceptable dielectric properties, high specific surface area, high hardness, high fracture toughness, and so on [1][2][3][4]. Up to now, many researches have focused on the preparation of porous Si 3 N 4 ceramics using various methods [5][6][7][8][9][10][11][12][13][14][15][16]. Compared with other preparation methods, adding pore-forming agent is more feasible due to its simple preparation process and low cost.…”

“…Solid loadings of Si 3 N 4 slurry were 15-25 vol%. Strong aqua ammonia was used to adjust the pH value of the slurry at about 10 [7]. After ball milling for 12 h, the slurry was degassed for 10 min under vacuum gauge pressure of 0.1 MPa.…”

Phase evolution and properties of novel Al2O3-based poly-hollow microsphere (PHM) ceramics

“…[1][2][3][4]. At present, lots of processing routes have been used to prepare porous ceramics, such as direct foaming [5][6][7][8], freeze casting [9][10][11][12], replication of polymer sponge [13][14][15], and adding pore-forming agent [16][17][18], etc. Among all these methods, adding pore-forming agent has been extensively used to prepare porous ceramics due to its simple preparation process and low cost.…”