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Zirconia Materials (zirconia + material)

Distribution by Scientific Domains
Polymers and Materials Science75%

Selected Abstracts

Preparation of a Nanoscale/SOFC-Grade Yttria-Stabilized Zirconia Material: A Quasi-Optimization of the Hydrothermal Coprecipitation Process

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2008
Yang-Chuang Chang
Yttria-stabilized zirconia (YSZ) is the key material for an electrolyte of a solid oxide fuel cell (SOFC). In order to prepare a nanoscale/SOFC-grade 8YSZ material, the hydrothermal coprecipitation process is intensively investigated for process improvement and product identification. From the characterization results of the 8YSZ product, the operation conditions were selected for process optimization. The criteria used in optimization condition determination were the reproducibility of the 8YSZ product and the particle size, the crystallinity, as well as the operation simplicity. Experimental results showed that a nanoscale/SOFC-grade 8YSZ powder was directly prepared. The quasi-optimum conditions of the process are proposed. [source]

Clinical fit of four-unit zirconia posterior fixed dental prostheses

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2008
Sven Reich
The objective of this clinical study was to assess the internal and marginal accuracy of computer-aided design/computer-aided manufacturing (CAD/CAM)-generated four-unit all-ceramic posterior fixed dental prostheses (FDPs). The data were compared with the results of three-unit metal-ceramic and all-ceramic FDPs that were obtained in a previous study. Twenty-four patients were provided with all-ceramic posterior four-unit FDPs made from semisintered blank zirconia material. Prior to definitive insertion the accuracy was evaluated using a replica technique with a light body silicone that was stabilized with a heavy body material. The replica samples were examined using microscopy. The median marginal gap of the 24 four-unit FDPs was 77 ,m. The median gap widths were 87 ,m at the midaxial wall, 167 ,m at the axio-occlusal transition of the abutments, and 170 ,m at centro-occlusal location. Although the marginal accuracy of the four-unit FDPs differed significantly from that of the three-unit metal-ceramic FDPs (median 54 ,m), the values obtained were clinically satisfactory and showed that semisintered zirconia blanks could be used for the fabrication of four-unit FDPs. [source]

Cosintering Simulation and Experimentation: Case Study of Nanocrystalline Zirconia

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2001
Johannes Kanters
Laminates consisting of two different nanocrystalline zirconia materials (undoped and 3Y-TZP doped) were sintered, and their densification and curvature were quantified using optical dilatometry. The experimental results agreed well with a continuum-mechanical description for the cosintering of laminates with diffusion coefficients and activation energies determined using densification of the free-sintering materials. The comparison covered various relative layer thicknesses and heating rates, but was developed only for the intermediate and late stages of sintering. Sintering stresses and compatibility stresses also were determined from the model. [source]

Morphology and Phase Stability of Nitrogen,Partially Stabilized Zirconia (N-PSZ)

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2001
Tai-Joo Chung
The surface layer of yttria-doped tetragonal zirconia materials that have been heat-treated with zirconium nitride was observed to consist of a nitrogen-rich cubic matrix with nitrogen-poor tetragonal precipitates. The precipitates had a thin, oblate-lens shape, similar to those observed in magnesia,partially stabilized zirconia. Because of the fast diffusion of N4, ions, the precipitates grew rather large, up to ,5 ,m in length, and remained stabilized in the tetragonal form at room temperature. Because the nitrided layer grew in the two-phase field, the size and distribution of the precipitates each was very irregular. The nitrogen content was observed to determine the proportion of cubic and tetragonal phases in the same way as in conventional cation-stabilized partially stabilized zirconia. A ternary phase diagram for the zirconium(yttrium),nitrogen,oxygen system was suggested to explain the concentration gradient in the cubic matrix and the phase distribution of the nitrided layer. [source]