• Korean Journal of Materials Research
• /
• v.21 no.11
• /
• pp.604-610
• /
• 2011

The effect of $BaF_2$ flux in $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) formation was investigated. Phase transformation of $Y_3Al_5O_{12}$(YAG) was characterized by using XRD, SEM, and TEM-EDS, and it was revealed that the sequential formation of the $Y_4Al_2O_9$(YAM), $YAlO_3$(YAP) and $Y_3Al_5O_{12}$(YAG) in the temperature range of 1000-1500$^{\circ}C$. Single phase of YAG was revealed from 1300$^{\circ}C$. In order to find out the effect of $BaF_2$ flux, three modeling experiments between starting materials (1.5$Al_2O_3$-2.5$Y_2O_3$, $Y_2O_3$-$BaF_2$, and $Al_2O_3$-$BaF_2$) were done. These modeling experiments showed that the nucleation process occurs via the dissolution-precipitation mechanism, whereas the grain growth process is controlled via the liquid-phase diffusion route. YAG:Ce phosphor particles prepared using a proposed technique exhibit a spherical shape, high crystallinity, and an emission intensity. According to the experimental results conducted in this investigation, 5% of $BaF_2$ was the best concentration for physical, chemical and optical properties of $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) that is approximately 10-15% greater than that of commercial phosphor powder.

• Food Science and Preservation
• /
• v.22 no.6
• /
• pp.915-919
• /
• 2015

This study was performed in order to provide basic data for predicting the usefulness of Jicama (Pachyrhizus erosus) as a food raw material. The changes in the physicochemical properties of freeze-dried and hot air-dried Jicama were investigated and analyzed. The moisture content of raw Jicama was 81.84%. The crude protein, crude fat, crude ash and carbohydrate content of hot air-dried Jicama powder were 2.85, 0.79, 7.93 and 88.44%, while those of freeze-dried Jicama powder were 3.93, 0.83, 7.92 and 87.32%, respectively on dry basis. Regarding the color values, the lightness of freeze-dried Jicama (92.86) was higher than that of the hot air-dried Jicama (88.01), whereas the redness (-0.67) and yellowness (3.21) of freeze-dried Jicama were lower than those of the hot air-dried Jicama (0.43) and (11.96), respectively. The brown index was lower in the freeze-dried Jicama (0.029) than in hot air-dried Jicama (0.107). The total sugar content showed no significant differences between freeze (46.49 mg/g) and hot air-dried Jicama (45.11 mg/g). Finally, the amylose content was higher in freeze-dried Jicama (5.66%) than in hot air-dried Jicama (6.63%).