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- Al2O3-Y2O3-ZrO2 (1)
- Crystallization behavior (1)
- Emissivity (1)
- Eutectic ceramics (1)
- Infrared optical properties (1)
- Laser processing (1)
- Mean pore diameter (1)
- Microstructure (1)
- Oxide ceramic (1)
- Porosity (1)
The infrared-optical properties and particularly the emissivity of sintered ceramics depend on the material's bulk properties and structural properties such as porosity, pore size distribution and pore diameter. The infrared-optical properties can be varied across a wide range by specifically selecting the material's bulk and structural properties. A major concern of the present study is the development of a ceramic coating material with a total emissivity below 0.2 at a temperature of 800 °C. For this purpose, various samples of a TiO2-Y2O3 (TY) ceramic composite were produced with different properties. On variation in the Y2O3 content from 5 to 60 wt%, the porosity of the ceramic composites varies from 3 % to 47 % with the mean pore diameter lying in a range from 0.3 µm to 1.7 µm. The addition of graphitic pore builders increases the porosity up to 60 % and the mean pore diameter to a maximum of 15 µm. By optimizing the total porosity and the pore size of the TY ceramics, a total emissivity as low as 0.17 at 800 °C could be achieved.
Transparent microspheres with the eutectic composition 65 Al2O3-16 Y2O3-19 ZrO2 (mol%) have been produced by laser fusing with a CO2 laser. The influence of the starting material – not pre-calcined and pre-calcined – as well as the laser power on the resulting microspheres – was investigated. After fabrication, the microspheres were analyzed by means of XRD to quantify the amorphous content of the spheres as well as to identify the residual crystalline phases, with a laser granulometer to measure the particle sizes of the starting material and the resulting microspheres, with DSC to characterize the glass transition temperature and crystallization behavior, and with SEM to investigate the microstructure of the microspheres. The laser-treated materials consist of transparent and opaque beads as well as sintered particles. The amorphous amount in the samples was detected to be ~ 85 %. Based on these results transparent beads were collected and annealed over a range of temperatures to analyze the crystallization behavior.