Papers by Author: Shu Qiang Ding

Abstract: An oxidation bonding process was developed to fabricate oxidation-bonded porous silicon nitride (Si3N4) ceramics from α-Si3N4 powder in air at 1100-1400oC. Si3N4 particles are bonded by the oxidation-derived silica (SiO2) and the pores derive from the stack of Si3N4 particles and the release of N2 and SiO gas during the sintering. The microstructure of oxidation-bonded porous Si3N4 ceramics was observed. Moreover, the fracture mechanism was analyzed. Effects of the bonding phases and pores on the flexural strength were investigated. Oxidation-bonded porous Si3N4 ceramics with high flexural strength was obtained by restraining the crystallization of amorphous silica and forming the well-developed necks between Si3N4 particles.

Abstract: Porous silicon carbide (SiC) ceramics were fabricated by a polycarbosilane (PCS) conversion bonding technique, in which PCS was used as a binder to bond SiC particles with each other. In the preparing process, SiC particles were first coated with PCS, and then the powder compacts were heat-treated in an inert atmosphere. During the heat-treatment, the PCS decomposed and gradually converted to inorganic covalent solids composed mainly of Si-C networks. The pyrolysis process of PCS, the pore structures and flexural strength of the as-prepared specimens were analyzed and discussed. Preparing temperature as low as 1100°C was adopted in this process and the porous SiC ceramics with a flexural strength of 20 MPa at an open porosity of 43% was obtained. Since PCS was used as a binder, the critical feature of this technique was that the preparation of porous SiC body was achieved at a low temperature.

Abstract: A novel technique was developed to synthesize porous silica–matrix ceramics from silicon carbide and alumina with an Y2O3 addition, using pine sawdust as a pore former. The porous ceramics were fabricated at temperatures of 1300–1500 oC in air by a reaction–bonding process based on two reactions: (1)SiC+2O2→SiO2+CO2 (Oxidation) and (2)2SiO2+3Al2O3→3Al2O3·2SiO2 (Mullitization). Reaction–bonding behavior, mechanical property and open porosity were investigated as a function of Y2O3 content as well as sintering temperature and holding time. Moreover, phase composition and microstructure of the porous silica–matrix ceramics were studied by X–ray diffraction (XRD) and scanning electron microscopy (SEM).