Abdul Rashid Jamaludin

The effect of CaCO3 addition on the crystallization behavior of ZnO crystal glaze fired at different gloss firing and crystallization temperatures

A glazed ceramic product with crystalline structure gives an artistic effect. In this study, the effects of calcium carbonate (CaCO3) addition into glaze batches on the crystallization behavior of crystal glaze were studied. Samples were fired at different gloss firing temperatures ranging from 1000-1200 o C with 1060 o C crystallization temperature. Xray diffraction (XRD) and energy dispersive X-ray spectrometer (EDX) analysis of the phases identified these crystals as willemite (Zn2SiO4) in the form of spherulites. Scanning electron microscope (SEM) analysis indicated that willemite crystals are in the acicular needle like shape. XRD result showed that the intensities of crystal peaks decreased with the addition of CaCO3 up to 3.0 wt%. However, there was no willemite crystals formation as the amount of CaCO3 raised to 5.0 wt%. Besides that, the results also indicated that willemite growth occurs during isothermal holding at crystallization temperature instead of during cooling from gloss firing temperature.

Effects of Different Gloss Firing Temperature on the Crystallization of Zinc-Based Crystal Glaze

Ceramic products with crystalline structure on its body give an artistic effect. The usage of zinc oxide which acts as a flux material has a beneficial effect in many colored glazes amongst which is crystalline glaze. Samples are fired at different gloss firing temperature of 1200oC to 1250oC for half an hour and hold for five hours at crystal growth temperature. After firing, the morphology of crystalline structure on the ceramic substrate body was identified using visual observation. The result show crystals start to develop at 1230oC of gloss firing temperature. Scanning Electron Microscope (SEM) analysis shows that these crystals are made of acicular needle shape crystals. X-ray Diffraction (XRD) and Energy Dispersive X-ray Spectrometer (EDX) analysis of the phases identified these crystals as willemite, Zn2SiO4 which formed spherulites. The results also show obvious growth and distance distribution between each of spherulites as the gloss firing temperatures increase to 1250oC.

Improvement of Porous Porcelain through Glaze Coating

The dip coating procedure led to accumulation of coating particles at the coating solution and substrate interface. After sintered, frit dissolution implied an occurrence of liquid phase sintering. Simultaneous improvement of surface morphology and bulk density was evident. The significant appearance of cracks and roughed surface of plain porcelain was revolved into crack free and smoother exterior following the dip-coating and sintering process. The surface was properly glazed. This led to enhanced body densification, and sealing of apparent micropores. At the same time, the deposited coating reduced the amounts of open cells and surface defects, which caused reduction in porosity and increment of bulk density.

The Effect of CaCO3 Addition on Physical Properties of ZnO-Based Crystal Glaze

The effects of calcium carbonate (CaCO3) addition on the physical properties of ZnO-based crystal glaze batches were investigated. Samples were fired at different gloss firing temperatures ranging from 1180-1220°C with 3 hours soaking at 1060°C crystallization temperature. X-ray diffraction (XRD) analysis identifiedthe crystal phase occurred as willemite (Zn2SiO4) and the scanning electron microscope (SEM) analysis indicated that willemite crystals are in the acicular needle like shape that formed spherulite. The intensities of willemite peaks decreased with CaCO3 addition and completely vanished at 5.0 wt% CaCO3. Varied formation of spherulites developed of the surface of crystal glaze as the flows of the glaze stretched further as the amount of CaCO3 increased.