Kunio Kimura

A new approach to anorthite porcelain bodies using nonplastic raw materials

Abstract New anorthite porcelain bodies using only nonplastic raw materials, such as feldspar, quartz, and aluminous cement, without using a binder were fabricated, and their properties were investigated. The green strength was relatively high due to hardening by the hydration reaction of the aluminous cement with the feldspar in a moist atmosphere. The phases found in the green body were feldspar, CaAl 2 O 4 , CaAl 4 O 7 , α-quartz and a small amount of CaAl 2 Si 2 O 8 ·4H 2 O. The phases in the fired body were α-quartz, anorthite, glass and a small amount of α-Al 2 O 3 ; cristobalite formed only at a quartz content of 60 wt.%. Higher flexural strength at a composition containing 30 wt.% feldspar is attributed both to fewer crack origins as a result of appropriate vitrification and to greater residual stress caused by the larger difference in the thermal expansion coefficient between the glass matrix and the quartz and anorthite grains.

Fabrication of new porcelain body using nonplastic raw materials by slip casting

New porcelain bodies using only nonplastic raw materials, such as volcanic glass, quartz, alumina and aluminous cement, were fabricated, and their properties were investigated. Green strength increased with increasing Al2O3 content at the constant amount of volcanic glass and aluminous cement, caused by the increase of green bulk density with small sized Al2O3 addition. The phases in the fired body were glass, α-quartz, cristobalite, anorthite and α-Al2O3. High flexural strength with 10 wt% Al2O3 addition was attributed to a strong residual stress induced by the large difference in the thermal expansion coefficient between the glass matrix and the quartz grains, and an additional prestress was induced by Al2O3 grains. Higher density and fewer fracture origin were also indicated as potential factors leading to the strengthening effect.

The effect of the reaction conditions on the morphology of coating layers of alumina hydrate on silicon carbide whiskers

Alumina hydrate-coated silicon carbide whiskers were prepared by a raw material injection method. which has already prepared several kinds of composite particles in an aqueous media by a similar manner with the fluidized bed coating method. This method injects the raw material for the coating layers into a precipitant solution in which the core particles are already dispersed to obtain the objective composite particles. In this study, the effect of the reaction conditions on the morphology of the coating layers was investigated. From the results, the surfaces were smoother under the following reaction conditions: higher silicon carbide whisker concentration, lower aluminum nitrate concentration, lower aluminum nitrate solution injection rate, higher partial pressure of carbon dioxide and lower reaction temperature. The coating process was considered to include a homogeneous nucleation and coalescence process, which had a significant effect on the surface morphology of the coating layer. From these conditions, a lower probability of collision between the particles grown from the homogeneous nuclei and a higher probability of collision between the particle from the homogeneous nuclei and the whiskers were considered to produce a smoother coating layer on the whiskers