Papers by Keyword: Cordierite Ceramic

Abstract: Cordierite ceramic of chemical composition 2MgO-2Al2O3-5SiO2 has low value of thermal expansion, excellent thermal shock resistance, high porosity and high strength. The exhibited properties resulted wide range of industrial applications, especially in the catalytic converter, kiln furniture, diesel particulate filter and high frequency insulator. It occurs rarely in nature and its formulation from the indigenous raw materials is sensitive to the peak sintering temperature and holding time. Both the parameters are again affected on the source of raw materials. Hence optimization of peak temperature and holding time is crucial for each source of raw materials. In this paper three indigenous raw materials, clay, kaolin and talc were taken and mixed with different dopants. The prepared powder batch was sintered at different peak temperature and holding time. Among the three indigenous raw materials kaolin was found to be most suitable to formulate cordierite. The peak temperature was varied within the range of 1340°C -1400°C and the holding time was considered from 30 minutes to 90 minutes. Both the parameters had significant influence on the production of cordierite. The percent of cordierite formation was affected with both the variation of holding time and peak temperature. Tough thermal shock resistance was not influenced by any of the parameters, but the influence on the porosity was quite significant. The green body was also prepared from calcined powder batch and was sintered at different peak temperature. Calcination did not exhibit any affect on cordierite formulation.

Abstract: The present work aims to develop porous ceramic plates based on cordierite, using the polymer foam replication method, to be used for gas burners. Ceramic foams were produced by coating polyurethane foams of different pore sizes with ceramic powders dispersed in aqueous slurries. The final porous structures were shown to depend on the structure of the original polymer sponge and on the details of the fabrication procedure. However, a suitable process control enabled to obtain a close relation between the final properties and the template polymer characteristics. The performance of the porous cordierite plates, with different pore size distributions, as medium burners was tested and compared by measuring the pressure drop in the burner against the air flow rate. It could be concluded that good performance is achieved with the higher porous materials due to its higher porosity fraction, and more suitable pore size range.

Abstract: The high dense pure cordierite ceramics and liquid-phase-sintering cordierite ceramics were prepared with the starting powder made by sol-gel progress. The porosities of them are less than 6.21%, and some can be up to 1.0% especially. The flexural strength of the sample can get to 167 MPa, which is greater than that of 103 MPa of pure cordierite ceramics. The composition, fracture behavior and microstructure of the liquid-phase-sintering cordierite ceramics are investigated. The result shows that the increased flexural strength is mainly attributed to the change in cell parameters of cordierite and the small grain size.

Abstract: Nanocrystalline cordierite powders were prepared by the polymerized complex method. The synthesized precursor was calcined in air at 600-1200 oC for 1h, and the calcined powders were fully characterized by TG/DTA, BET, XRD, SEM, and TEM. The XRD and selected-area electron diffraction (SAED) analysis confirmed the development of the phase composition of cordierite powders showing amorphous phase after calcination at temperature below 800oC, mixed phases of spinel and μ-cordierite phase after calcination at 800oC and 900oC, and mixed phases of spinel, μ- cordierite and α-cordierite phases after calcination at above 900oC. The BET specific surface areas of the calcined powders varied from 3 to 107 m2/g, depending on calcination temperature. The highest specific surface area of 107 m2/g was found in the powders calcined at 800oC. The average particle sizes evaluated by BET were less than 60 nm, depending on calcination temperature. The powders calcined at 800oC and 1000oC were uniaxially pressed and pressureless-sintered in air at 1250-1350oC for 2h. Densities of the sintered samples evaluated by Archimedes’s method were 87- 91 % of theoretical value. The crystal structure of all the sintered samples, determined by XRD, was mainly α-cordierite, having a small amount of spinel as second phase.