AlN single crystal was thermally treated at 1200oC and 1500oC in the ambient gas of nitrogen. AlN single crystal was obtained by sublimation growth process using by a facility having a growth part which was heated by RF (Radio Frequency) induction heating. In this report, the optical microscopic results taken from thermally treated AlN single crystal and FWHM (Full width of half maximum) measured by DCXRD (Double crystal X-ray Diffractometry) were reported.
NiO/NiCo2O4 nanocubes were successfully synthesized via the calcination process of Ni3[Co(CN)6]2 PBAs. The prepared monodispersed Ni3[Co(CN)6]2 PBAs were aggregated by ‘self-assembly’ of the nuclei generated during the synthesis reaction. The self-assembly rate of the particles is affected by the temperature and the amount of surfactant SDBS (sodium dodecylbenzenesulfonate). FESEM analysis shows that monodispersed 200 nm PBA nanocubes are obtained at 0.25 g SDBS and 60 o C temperature. Thermal behavior was confirmed by thermogravimetric-differential thermal analysis (TG-DTA) to determine optimal calcination conditions. Then, field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analyzes were performed to investigate the morphology and crystallinity of the particles precursors and NiO/ NiCo2O4 nanocubes.
The degradation of the concrete due to deterioration factors, such as corrosion of steel bars, cracks and structural strength of reinforced concrete structures, is a social problem. Especially, concrete structures constructed in seawater, underground water, waste water treatment facilities and sewerage are subject to chemical attack by acid and sulphate. Therefore, this study was conducted to compare sulfated glass and fine aggregate of slag using waste glass fine powder and meta kaolin. The results showed that the slag fine aggregate showed better sulfate resistance than the river sand, and the fine powder of waste glass showed the best performance at 3 % displacement.
For the production of a high-density ITO target, In2O3 powders with a small particle size and low agglomeration should be synthesized. The purpose of this study is to control the size and shape of the Indium hydroxide precursor which affects the properties of the In2O3 powder. As a starting raw material, Indium metal was dissolved in a Nitric acid (HNO3) solution. The effect of concentration, pH, and temperature on the properties of Indium hydroxide was investigated using ammonium hydroxide as a precipitant. Crystallite size of each sample was analyzed by X-ray diffraction and the shape and the size of the powder was analyzed by transmission electron microscopy. As a result, the particle size of Indium hydroxide was increased with increase in the concentration of In(NO3)3 and the particle size and shape of the Indium hydroxide remained unchanged with increase in the pH of the solution. The particle size increased with increase in the precipitation temperature during precipitation.
In this study, numerical simulation was performed to focus on optimized process condition for obtaining a longterm growth and high quality SiC crystal. It could be optimized by considering the change of fluid and a carbon flow in the Si melt added with 40 % Cr. The Crystal Growth Simulator (CGSim TM , STR Group Ltd.) was used as a numerical simulation. It was confirmed that many parameters such as temperature, rotation speed of seed crystal and crucible, and seed position during the crystal growth step had a strong influence on the speed and direction of solution flow for uniform temperature gradient and stable crystal growth. The optimized process condition for the solution growth of SiC crystal was successfully exhibited by adjusting various process parameters in the numerical simulation, which would be helpful for real crystal growth.
In this study, we prepared the board of vermiculite materials utilizing coal bottom ash from the Western thermal power stations in Korea and obtained experimental data in applications for building interior materials with the characteristics of sound absorption. To produce the mixture materials of vermiculite and coal bottom ash, we used a microwave drying process. In addition, a ball milling process was used to produce particles of coal bottom ash with a uniform size of 65 μm. When the board made from mixture materials of vermiculite and coal bottom ash were produced with bottom ash sulfur concentrations of 5, 10 wt%, maximum bending loads were analyzed. These experimental results would contribute much to fundamental data essential to the recycling technology of coal bottom ash.
To evaluate surface characteristics and improve crystalline quality of AlN single crystal grown by physical vapor transport (PVT) method, wet chemical etching process using KOH/H2O2 mixture in a low temperature condition and thermal annealing process was proceeded respectively. Conventional etching process using strong base etchant at a high temperature (above 300 o C) had formed over etching phenomenon according to crystalline quality of materials. When it occurred to over etching phenomenon, it had a low reliability of dislocation density because it cannot show correct number of etch pits per estimated area. Therefore, it was proceeded to etching process in a low temperature (below 100 o C) using H2O2 as an oxidizer in KOH aqueous solution and to be determined optimum etching condition and dislocation density via scanning electron microscope (SEM). For improving crystalline quality of AlN single crystal, thermal annealing process was proceeded. When compared with specimens as-prepared and as-annealed, full width at half maximum (FWHM) of the specimen as-annealed was decreased exponentially, and we analyzed the mechanism of this process via double crystal X-ray diffraction (DC-XRD).