Papers by Author: Sorapong Pongkrapan

Abstract: Ecological crystal glass with no toxic compounds, especially lead, was based on soda-lime-silica glass that fabricated mainly from 50 wt% local dressing sand, 22 wt% barium carbonate and doped with various concentrations of zirconium dioxide. Density (ρ), refractive index (RI), thermal expansion coefficient (CoE) and hardness (HV) were measured. It was found that the values of ρ, RI and HV increased linearly as the increasing of zirconium dioxide contents, whereas the CoE was decreased. This type of glass was ecologically friendly material.

Abstract: Ecological glass with non-toxic was fabricated in bismuth-bearing glass using mainly local quartz sands and various concentration of bismuth oxide. The specific gravity (SG), refractive index (RI), thermal expansion coefficient (CoE) and hardness (HV) were determined. It was found that the values of SG, RI and HV were increased linearly as the increasing of bismuth oxide, whiles that of CoE was decreased. This glass is environmentally friendly materials.

Abstract: Barium-bearing glass samples were fabricated in a laboratory scale using quartz sands that was a by-product of feldspar floatation in Tak Province, northern Thailand, and 30-wt% barite from Loei Province, northeastern Thailand, as the main compositions. Cr2O3 of concentrations ranging from 0.01 to 5.0 wt% was doped into the glass mixture. The dried powders were wellmixed in a ceramic crucible and melted in an electric furnace at 1250°C for 6 hr. Bubble-free glass samples were yielded after cooling down. The glass colors were changed from colorless to green by the addition of Cr2O3. Dielectric property, color, specific gravity, and refractive index of the glass samples were analyzed. It was found that dielectric constant, specific gravity, and refractive index increased with increasing amount of Cr2O3 dopant. Measurements of UV-VIS-NIR spectra and microstuctural analysis using scanning electron microscope were also carried out and discussed.

Abstract: Soda-based glass samples were fabricated in a laboratory scale using quartz sands that was a by-product of feldspar floatation in Tak Province, northern Thailand, and 25-wt% commercial-grade Na2CO3 as the main compositions. Fe2O3 of 0.1 to 10.0 wt% concentrations was doped into the glass mixture. Well-mixed and dried powders were melted in a ceramic crucible for 6 h at 1250°C using an electric furnace. Transparent and bubble-free glass samples were obtained as results. It was found that Fe2O3 dopant turned the otherwise colorless glass to dark brown. Dielectric property and physical properties, such as, color, specific gravity, and refractive index of the glass samples were studied. The samples’ dielectric constant, specific gravity, and refractive index increased with increasing Fe2O3 doping concentration. UV-VIS-NIR and synchrotron-based X-ray absorption spectra were measured and discussed.

Abstract: Lead-based glass samples were fabricated in a laboratory scale using quartz sands that was a by-product of feldspar floatation in Tak Province, northern Thailand, and 20-wt% commercial-grade PbO as the main compositions. A CdS/Se compound of ratios ranging from 1:1 to 1:10 was doped into the glass mixture. The dried powders were well mixed in a ceramic crucible before being melted in an electric furnace at a maximum temperature of 1100°C for 4 hours. Transparent and bubble-free glass samples were resulted after cooling down to room temperature. It was found that the glass colors were changed from colorless to reddish brown by the addition of CdS/Se compound. Physical properties of the samples, such as, color, specific gravity, and refractive index were studied. Specific gravity and refractive index increased with increasing ratio of CdS/Se. UV-VIS-NIR spectra were measured and discussed.

Abstract: The dielectric constant values of a set of synthetic alpha alumina samples doped with Cr and Be were determined using parallel plate method. The voltage frequency was selected at 1 MHz. When Cr was doped to the sample, the dielectric constant was increased due to the increase in polarizations of the sample, whereas the Be-doped one showed the decrease in dielectric constant cf. the undoped synthetic alpha alumina (reference sample). Experiments on doping alpha alumina with both elements showed increasing in dielectric constant compared to the undoped reference sample, i.e., Cr has more influence to the dielectric constant value. Dielectric constants of a set of natural sapphires were also measured and compared to those obtained from the synthetic ones. The results of both natural and synthetic samples varied in the same direction. It suggests, however, that the geological origins of the samples are needed to be considered. This is due to the differences in physico-chemical conditions of their formations that would have influenced partitioning of trace elements as well as evolving of defects in natural samples. Increasing of the R1 and R2 photoluminescence wavelengths and decreasing of refractive indices of the doped samples cf. those of the reference sample were obtained from the experiments.