• Gao Jiqiang

      Articles written in Bulletin of Materials Science

    • Effects of talc and clay addition on pressureless sintering of porous Si3N4 ceramics

      Yu Fangli Yang Jianfeng Xue Yaohui Du Jun Lu Yuan Gao Jiqiang

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      Porous Si3N4 ceramics were successfully synthesized using cheaper talc and clay as sintering additives by pressureless sintering technology and the microstructure and mechanical properties of the ceramics were also investigated. The results indicated that the ceramics consisted of elongated 𝛽-Si3N4 and small Si2N2O grains. Fibrous 𝛽-Si3N4 grains developed in the porous microstructure, and the grain morphology and size were affected by different sintering conditions. Adding 20% talc and clay sintered at 1700°C for 2 h, the porous Si3N4 ceramics were obtained with excellent properties. The final mechanical properties of the Si3N4 ceramics were as follows: porosity, 𝑃0 = 45.39%; density, ρ = 1.663.g.cm-3; flexural strength, 𝜎b (average) = 131.59 MPa; Weibull modulus, 𝑚 = 16.20.

    • Effects of organic additives on microstructure and mechanical properties of porous Si3N4 ceramics

      Yu Fangli Wang Huanrui Yang Jianfeng Gao Jiqiang

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      Green bodies of porous Si3N4 ceramics were shaped by extrusion technique using different organic additives as binder during extrusion molding. Different porosity, microstructures and mechanical properties after the extrusion, drying, debinding and sintering stages were investigated. The solid slurry content of 70–75% and extrusion pressure of 0.5–1.0 MPa had played a decisive role in the smooth realization of extrusion molding. The porous Si3N4 ceramics were obtained with excellent properties using 4% hydroxypropyl methyl cellulose (HPMC) as binder and polyethylene glycol (PEG) of molecular weight, 1000, as plasticizer with a density of 1.91 g cm-3, porosity of 41.70%, three-point bending strength of 166.53 ± 20 MPa, fracture toughness of 2.45 ± 0.2 MPa m1/2 and Weibull modulus (m) of 20.75.

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