Graphitic carbon nitride (g-C3N4) is an attractive photocatalyst, however, its practical photocatalytic applications are still faced with huge challenges. The aim of this research is to identify the correlation between synthetic conditions and properties of the g-C3N4 and derive an optimum synthesis condition for improving photocatalytic activities of the g-C3N4. In this study, novel and versatile g-C3N4 nanosheets were synthesized by the simple thermal pyrolysis of urea. In the synthesis process, the pyrolysis temperature and the heating rate, which can have the most significant influence on the structures and properties of g-C3N4, were set as variables, and the effects were systematically investigated. When synthesized at a relatively high temperature, the amount of material being synthesized is reduced, however it has been found to represent optical properties suitable for highly efficient photocatalyst by the increase in the thickness and defects formed in the g-C3N4 nanosheets. The photocatalytic degradation experiment of MB dyes indicated that the highest degradation of 95.2% after the reaction for 120 min was achieved on the g-C3N4 nanosheets synthesized at 650oC.
The sintering behavior of p-type bismuth telluride powder is investigated by means of dilatometric analysis. The alloy powders, prepared by ball milling of melt-spun ribbons, exhibit refined and flake shape. Differential thermal analysis reveals that the endothermic peak at about 280oC corresponds to the melting of bismuth, and peaks existing between 410oC and 510oC are presumably due to the oxidation and crystallization of the powder. The shrinkage behavior of ball-milled powders was strongly dependent of heating rate by the thermal effect exerted on specimens. In the case of 2oC/min, the peak temperature for the densification is measured at 406oC, while the peak temperature at a heating rate of 20oC/min is approximately 443oC. The relative density of specimen pressureless-sintered at 500oC exhibited relatively low value, and thus further study is required in order to increase the density of sintered body.