Papers by Author: Dan Bo Lin

Abstract: In this paper, highly porous Si3N4 ceramics with high strength, homogeneous microstructure were fabricated by introducing a proper amount of nanometer carbon in the Si3N4 slurry by gel-casting. Scanning electron microscopy, X-ray diffraction, Archimedes water-displacement method and three-point bending tests were employed to analyze the microstructures and mechanical properties of the sintered bodies. It was shown by the XRD analysis that SiC particles were formed in the sintered bodies. The pillar β- Si3N4 morphology, homogeneous microstructure and the SiC particles as a reinforcement phase are the contributing factors for high porosity and good mechanical behavior.

Abstract: Porous Si3N4 ceramics by gel casting preparation has received considerable attention because of its excellent performance. In the paper, orthogonal experimental design L16(45) was used to investigate the preparation of porous Si3N4 ceramics by gel casting preparation. Three variables including solid loading, monomer content and the ratio of crosslinking agent to monomer were studied. Through range analysis and variance analysis, the results suggest that the ratio of crosslinking agent to monomer has significant influences on both the flexural strength and porosity of Si3N4 sintering body. For the flexural strength of Si3N4 sintering body, the order of significance levels was as follows: the ratio of crosslinking agent to monomer, solid loading and monomer content. For the porosity of Si3N4 sintering body, the order of significance levels was as follows: the ratio of crosslinking agent to monomer , monomer content and solid loading.

Abstract: Highly porous Si3N4 ceramics in service are usually subjected to continuous impact of solid particles which may give rise to localized damage and consequently to strength degradation. Hertzian indentation and three-point bending tests were conducted to investigate the contact damage behavior of highly porous Si3N4 ceramics in this paper. The Hertzian indentation damage morphologies were examined by using a bonded-interface technique. As a result of intragranular microfracture under Hertzian indentation, a distributed subsurface damage region is developed beneath the indenter. It was shown that, with increasing indentation load, the damage region extends progressively and a quasi-plastic stress-strain response exhibits. Failure sources were observed to be Hertzian indentation sites in three-point bending tests, leading to a gradual strength degradation.