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Ceramic Parts (ceramic + part)
Selected AbstractsRapid Prototyping of Piezoelectric Ceramics via Selective Laser Sintering and GelcastingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Dong Guo This article presents a new lost mold rapid prototyping method which combines selective laser sintering (SLS) and gelcasting techniques for fabricating piezoelectric ceramics. SLS was used to fabricate sacrificial molds of the desired structure of the ceramic part. Then aqueous PZT (lead zirconate titanate) suspension was cast in the mold and solidified in situ through formation of a three-dimensional network gel. Because the polymer mold can be easily removed at the initial stage of sintering and the gelcast PZT body has a high green strength, the desired geometry of the PZT part can be completely retained after sintering of the ceramics. Complex-shaped PZT parts were successfully fabricated after using concentrated PZT suspension with low viscosity. Densities and electrical properties, such as the d33, the relative permittivity ,, the dielectric loss tg, and the electromechanical coupling factor Kp of the gelcast PZT parts were also compared with those of the die-pressed PZT samples. The results indicated that the gel-forming process did not deteriorate the electrical properties of the samples, if proper dispersant was selected in developing concentrated ceramic slurry. [source] Strength estimation of ceramic,metal joints with various interlayer thicknessFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2003M. TAKAHASHI ABSTRACT Residual stresses generated by the mismatch of thermal expansion coefficients of ceramics and metals affect the strength of ceramic,metal joints. An interlayer metal can be inserted between the ceramic and metal in order to relax this stress. An analysis was carried out of the residual stresses produced during joint-cooling and in 4-point bending tests. The effects of interlayer thickness on ceramic,metal joint strength were then studied by considering a superimposed stress distribution of the residual stress and the bending stress. Finally, joint strength was estimated from fracture mechanics and strength probability analysis by considering the residual stress distribution, defect size and position of pre-existing defects in the ceramic parts. As a result of this study, we suggest an optimum material selection and interlayer thickness for ceramic,metal joint structures. This approach is generally suitable for the design of electrical and mechanical structures. [source] Direct Laser Sintering of Al2O3,SiO2 Dental Ceramic Components by Layer-Wise Slurry DepositionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006André Gahler This publication presents a solid freeform fabrication technique for ceramics in the alumina,silica system by layering binder-free, high-loaded ceramic slurries, followed by selective laser sintering. The low melting silica phase and the reaction sintering between silica and alumina favor the rapid prototyping of pure ceramic parts. On the basis of electroacoustic and viscosity measurements, stable slurries from Al2O3/SiO2 powder mixtures and water with a high fluidity have been prepared for the layer deposition with a doctor blade like in tape casting. Layers with a thickness of about 100 ,m were processed. It was found in laser parameter studies that ceramic parts can only be obtained using special alumina contents and laser parameters. But the biphasic approach may allow greater flexibility in the processing regime than is afforded by the use of just one material. The microstructure of these parts depends mainly on the temperature gradient induced by the laser absorption and thermal conduction. The wet shaping facilitates laser-sintered parts with a relatively high density, which could be increased by a thermal post-treatment. [source] | ||||||||||