| In this paper, Al2O3-C unfired slide plate materials with different kind additives such as Sialon powder, Al powder, Si powder and Sialon+ Al mixed powder were studied. After heating treatment at 200℃×24h, 800℃×3h, 1200℃×3h and 1450℃×3h, their typical physical properties such as apparent porosity, bulk density, cold modulus of rupture, hot modulus of rupture, thermal expansion, thermal shock resistance and oxidation resistance were examined. Microstructure was analyzed by SEM. EDAX and XRD were carried out to study the phase transformation and microstructure characteristics of the materials.The effects of Sialon containing on physical properties and microstructure of material were studied. With the increase of Sialon addition, the properties of cold modulus of rupture, hot modulus of rupture and thermal shock resistance have all been improved, the thermal expansion does not change significantly, and the oxidation resistance has been improved slightly. The result of microstructure characteristics and phase analysis study shows that at 200℃~800℃, the phases do not change significantly; at 800℃~1200℃, both SiO2 and SiC whiskers are observed; at 1200℃~1450℃, all residual Si reacted with SiO2 and converted into SiC, these floccose and net-shaped SiC whiskers filled in the pores;β-Sialon grains arrange regularly.The effects of metallic Al addition on physical properties and microstructure characteristics of material were studied. With the increase of metallic Al addition, the cold modulus of rupture and hot modulus of rupture were increased substantially, the thermal shock resistance retained at the low level, the volume expansion rate was increased significantly after 800℃, the oxidation resistance was improved dramatically. The microstructure characteristics and phase analysis indicated that at 800℃, the metallic Al was changed into liquid phase and this liquid phase will fill in the pores; at 800℃~1200℃, the new phases both hexagonal Al3C4 whiskers and fibrous, and short-clavate AlN whiskers are observed growing in the pores between alumina particles and graphite; at 1200℃~1450℃, Si3N4 whiskers are observed andβ-Sialon crystals with different shape appear around it, and the Al3C4 disappeared at this temperature. At this stage the AlN whiskers were developed further, Al3CON peaks appear in XRD pattern, but has not been observed by SEM.The effects of Sialon+Al mixed power and particle size of metallic Al powder on physical properties and microstructure of material were studied. The cold modulus of rupture and hot modulus of rupture of samples with mixed power addition is lower than that with Al addition, but much higher than that with Sialon addition. Thermal shock resistance retains at same level as the samples with Sialon addition. The good oxidation resistance resulted as Al addition. The effect of particle size of metallic Al on the sample properties is not significant. The result of whiskers and microstructure characteristics and phase analysis shows that at 1200℃, both SiC and AlN peaks appear in XRD patterns, the columnar AlN whiskers, and fibrous and plate-like Al4C3 crystals are observed. In the surface of Al4C3 crystals, the columnar crystals of Al3CON with very small size were observed by EDAX technique; at 1450℃, both AlN andβ-Sialon peaks appear in XRD pattern. The morphology ofβ-Sialon has been investigated by SEM technique.Overall, the addition of mixed additives is more efficient in the improvement of the properties Al2O3-C slide plate material than that of single additive. The particle size of metallic Al has no significantly effect on the material properties. |
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