• Korean Journal of Materials Research
• /
• v.5 no.7
• /
• pp.888-896
• /
• 1995

In this paper the manufacture of shrinkage-free in situ Mullite-ZrO$_2$ceramics through the addition of Al base metal powder to the mixture of ZrSiO$_4$and A1$_2$O$_3$was attempt. The ZrO$_2$-strengthened mullite ceramics was prepared after the following reaction form, 3(Al+Al$_2$O$_3$)+2ZrSiO$_4$longrightarrow3A1$_2$O$_3$.2SiO$_2$+2ZrO$_2$Al metal powder was added from none to 30 weight percent to the A1$_2$O$_3$. The powders were mechanically mixed, isostatically pressed and reaction sintered at 1450-1$600^{\circ}C$ for 3hours. The specimens were sintered with and without intrim soaking time for 5 hours at 125$0^{\circ}C$ for the oxidation of Al-powder The addition of aluminium accelerates the reaction and compensate the shrinkage during the sintering through an increase in volume of oxidized Al. Because coarse flake type Al metal powders were not effectively milled, oxidized Al resulted in the relative large pore in the specimen.

• Journal of the Korean Ceramic Society
• /
• v.35 no.4
• /
• pp.311-318
• /
• 1998

The reaction bonded alumina ceramics with reinforced particles which have low shrinkage were pro-duced by blending of SiC or TiC or ZrO2 powders to the mixture of Al metal and Al2O3 powder. The powd-ers were attrition milled isostantically pressed and preheated tio 110$0^{\circ}C$ with a heating rate of $1.5^{\circ}C$/min The specimens were then sintered at the temperature range 1500 to 1$600^{\circ}C$ for 5 hours with a heating rate of 5$^{\circ}C$/min. The specimens showed 5-9% weight gain and 2-9% dimensional expansion through the complete oxidation of Al after preheating up to 11--$^{\circ}C$ the overall dimensional change of the specimens after the reaction sintering at 1500-1$600^{\circ}C$ was 6-12% The maximum densities were 92% theoretical. The fine grain-ed(average grain size :0.4 ${\mu}{\textrm}{m}$) microstructure were observed in the specimen with ZrO2 and SiC. But the microstructure of specimen with TiC was relatively coarse.(average grain size : 2.1 ${\mu}{\textrm}{m}$) The mullite phase was formed by the reaction of Al2O3 and SiO2 in a specimen with SiC. In the TiC contained specimen TiC was oxidized into TiO2 and finally reacted with Al2O3 to form Al2TiO5 during sintering.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.40 no.9
• /
• pp.1285-1291
• /
• 2011

This study was conducted to evaluate the effect of lotus leaf and lotus root powder on the quality characteristics of sponge cake. Percentages of 4, 8 and 12% of two kinds of lotus powder were added to the batter based on flour content. Baking and cooling loss rate, volume and specific loaf volume, crumb color, texture, scanning electron microscopy (SEM) and sensory evaluation of the products were analyzed. The baking and cooling loss rate of the control was lower than cakes with added lotus leaf and lotus root powder. The volume of the control was the largest, and as the amount of lotus leaf and lotus root powder increased, volume and specific loaf volume became smaller. The lightness and yellowness values of the control were higher than those of the experimental cakes, and the loaves with 12% added lotus root powder showed the lowest value. Redness of the experimental cakes increased. In the textual property evaluation, hardness of the control and sponge cakes containing 4% lotus leaf, and lotus root powder appeared to have the lowest value. As the amount of lotus leaf and lotus root powder increased, hardness increased. Springiness showed the same tendency, but cohesiveness of the control revealed the lowest value. The structure of the cake crumb by SEM, revealed that the crumb cells and grains of the experimental cakes were opened and coarse, as the amount of lotus leaf and lotus root powders increased. In a sensory evaluation, sponge cakes containing lotus root powder were preferred rather than those with lotus leaf powder. As a result, good sponge cakes were prepared by adding 4% lotus leaf powder or 8% lotus root powder.