2016, Vol.26, No.3

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

In this study, the crystalline property of a-plane GaN epitaxial layer grown on r-plane sapphire by a HVPE method has been investigated according to the V/III ratio and the growth time of multi-step growth. Furthermore, these results were compared with the previous result obtained from the single-step growth of a-plane GaN on r-plane sapphire substrate. In the multi-step growth for a-plane GaN epitaxial layer on r-plane sapphire, the FWHM values of rocking curve in GaN epitaxial layer were decreased as the HCl source flow rate and the growth time were increased. The void formed in epitaxial layer was continuously decreased as the growth time in first step and second step using a higher HCl flow rate was increased. As a result, the GaN layer obtained with the longest growth time on the first step and second step exhibited the lowest FWHM values of 584 arcsec and the smallest dependence of azimuth angle.

In this work, tin oxides were obtained by the liquid reduction precipitation method and hydrothermal process using SnCl2 · 2H2O, N2H4, and NaOH. Tin oxide crystals having different sizes and morphologies could be achieved. The powders were characterized by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). Depending on the molar ratio of the raw materials, tin oxide crystalline with the spherical and rectangular plate-like shape could be obtained, the crystal phase was SnO and Sn6O4(OH)4. And the obtained SnO crystals by a hydrothermal reaction showed various shapes, such as, spherical, plate-like and flower-like architectures depending on the temperature conditions.

Each year, more than seven hundred thousand tons of copper slag are generated in Korea as a byproduct during the production of copper. Due to the large amount of copper slag produced, there has been increased interest in the use of copper slag as a construction material. To evaluate the potential of copper slag as a construction material, laboratory evaluations were conducted in this study, and three particle shapes and replacement rates of river sand were selected as experimental variables. Strength, air-void characteristics, and sulfuric acid resistance were the three properties evaluated to assess whether copper slag can be used as a construction material. Test results indicate that the gradation of copper slag has an effect on strength, and the maximum strength was achieved when 60 % of river sand was replaced with copper slag. In addition, when compared with ordinary Portland cement mortar, replacing river sand with copper slag reduced air void size and increased sulfuric acid resistance.