Papers by Keyword: Mullite Ceramics

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Authors: Ludmila Mahnicka-Goremikina, Ruta Svinka, Visvaldis Svinka
Abstract: The porous mullite ceramics doped with such metal oxides as ZrO2, WO3 and MgO in quantity of 5 wt% were prepared by slip casting method. The mullite phase was the main and dominant phase of ZrO2-, WO3- and MgO-doped samples, which were sintered at the temperatures of 1650°C, 1500°C, respectively. The ZrO2, WO3 and MgO had the positive effect on the increase of porosity and decrease of thermal conductivity of porous mullite ceramics and the degree of this effect was in the order of ZrO2<MgO<WO3.
Authors: Jin Hong Li, Ling Xin Tong, Lei Hou, Jie Shen
Abstract: The effects of MgO and temperature on the properties and microstructure of mullite ceramics synthesized from high-aluminium coal fly ash and bauxite are investigated in this paper. The results show that when the batch containing 4 wt% MgO is heated from 1100 °C to 1500 °C, the bulk density and flexural strength increase obviously with the sintering temperature rising, mullite ceramics with flexural strength as high as 169 MPa can be obtained at 1500 °C with the addition of 2 wt% MgO. According to the XRD results, the corundum, cordierite and cristobalite phases disappear completely upon 1400 °C, it indicates that MgO addition may effectively promote sintering process. The results of SEM indicate that the prepared ceramics mainly exist in the shape of long parallelepipeds with the aspect ratio of about 7-10.
Authors: Zahra Negahdari, M. Solati, A. Saberi
Abstract: Increased processing pressure has resulted in need for the industry to optimize mechanical properties of ceramic foam filters used for molten metal processing. This paper will summarize the effect of ceramic slurry formulation on mechanical properties of reticulated porous ceramics processed by replica method. Commercial polyurethane sponge materials were chosen as a template to produce the RPC (reticulated porous ceramic) from a shear thinning multi component aqueous slurry composed of alumina, SiC, colloidal silica and some different additives. Thermal transformation sequence of the mixtures, resultant macrostructure and microstructure, relative density, grain morphology, phase composition, and mechanical strength of the sintered porous ceramics were investigated. Mechanical properties of struts were investigated by a theoretical model. The RPC had its maximum strength when Alumina/SiC weight ratio was 4.4. Such materials sintered at 1650° C in air, due to their excellent functional properties, are suitable for application as molten metal filter.
Authors: You Fen Li, Qing Liu, Wei Wei Liu, Min Li
Abstract: Dense Mullite/Al2O3 ceramics with a thermal conductivity of 45 W/m.K were obtained at the sintering temperature of 1500°C using Li2O, CaO and Y2O3 as additives. At temperature below 1500°C, the shrinkage of Mullite/Al2O3 ceramics is promoted by liquid LiAlSi2O6 and Al2Y4O9. Liquid LiAlSi2O6 mainly improves the densification of the sample when the sintering temperature increases to 1500°C. The formation of liquid phase at a relatively low temperature results in homogeneous Al2Y4O9 and Ca(Al2Si2O8) distributed around the Mullite/Al2O3 particles, which benefits the thermal conductivity improved.
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