In order to avoid un-uniform crystallization on the surface of a quartz glass crucible that is known to affect the production yield of the single crystal silicon, Ba (barium) was selected as a crystallization promotor and the inner surface of the crucible was coated using Ba (barium hydroxide octahydrate)-solution by the spray pyrolysis method. For un-coated crucible, it was found that the crystallization of its surface started at 1350 o C, and at 1450 o C the surface was uniformly crystallized with β-cristobalite phase. It was found that the crucible coated with Ba began to be crystallized from 1000 o C and was uniformly crystallized on the crucible surface at 1300 o C. In this case, α-cristobalite and needle-shaped BaSi2O5 phase were created and disappeared as a crystal phase, and the β-cristobalite phase was eventually evenly distributed over the Ba-coated crucible surface.
Halide perovskite nanocrystals have become attractive for LED applications due to their high color purity and excellent luminescent properties. CsPbX3 (X = I, Br, and Cl) nanocrystals were synthesized by hot-injection method and the emission wavelength was controlled by changing the composition of halide ion. Green- and red-emitting films were fabricated using a polymer binder. The outstanding optical properties of the synthesized nanocrystals and fabricated films were confirmed.
The wLED designed by green- and red-emitting perovskite nanocrystal films on blue InGaN LED was characterized.
The metal alkoxide, CuCo-glycerate nanospheres (NSs), were successfully synthesized as Cu-Co bimetallic sulfides hierarchical multi-shelled hollow nanospheres (CuCo2S4 HMHNSs) through solvothermal synthesis. In this reaction mechanism, the solvothermal temperature and the amount of glycerol as a cosurfactant play significant role to optimize the morphology of CuCo-glycerate NSs. Furthermore, CuCo2S4 HMHNSs were obtained under optimized sulfurization reaction time of 10 h via anion exchange reaction between glycerate and sulfur ions. Finally, the structural and chemical compositions of CuCoglycerate NSs and CuCo2S4 HMHNSs were confirmed through field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and electrochemical performances.
Ceria (CeO2) is a rare earth oxide, which has been widely investigated to improve the property. It is important to increase the surface area of CeO2, because high surface area of CeO2 can improve the catalytic ability. CeO2 nanoparticles were synthesized by a solvothermal process. A discussion on the influence of solvent ratio and precursors on CeO2 nanoparticles was performed. The size and degree of the agglomeration of the synthesized CeO2 could be tuned by controlling those parameters. The average size and distribution of prepared CeO2 powders was in the range of 3 to 13 nm and narrow, respectively. The XRD pattern showed that the synthesized CeO2 powders were crystalline with cubic phase of CeO2. The average particle size was calculated by Scherrer equation and FE-TEM images. The morphology of the synthesized CeO2 particle was objected using FE-TEM and FE-SEM. Specific surface area of the synthesized CeO2 was determined using BET (Brunauer-Emmett-Teller) equation.
Ink-jet printing technology with ceramic ink of the four digital primary colors (cyan, magenta, yellow, and black; CMYK) can provide stable coloration even in the high-temperature firing process. Ceramic ink-jet printing can be widely applied in construction and ceramic industries due to the advantages of accurate and fast printing process of digital images for various products. Generally, organic solvent with proper viscosity and surface tension has been used in digital ink-jet printing process. However, the needs of ceramic ink without VOCs emission is increasing. In the present study, eco-friendly ceramic ink was synthesized by combining alumino boro-silicate glass frit and CoAl2O4 inorganic pigment based on an aqueous solvent that does not generate VOCs. The rheological properties and dispersion stability of aqueous ceramic ink were optimized.
Jetting behavior and printing characteristics of the ceramic ink were also investigated in detail. As a result, the formulated aqueous ceramic complex ink showed a suitable jetting behavior without satellite drop by adjusting viscosity and surface tension. The ceramic ink can be printed on glass substrate with minimized spreading phenomena duo to high contact angle.
In the past few years, various solder compositions have been a representative material to electronic packages and surface mount technology industries as a replacement of Pb-base solder alloy. Therefore, extensive studies on process and/or reliability related with the low Ag composition have been reported because of recent rapid rise in Ag price. In this study, Sn-3.0Ag-0.5Cu, Sn-0.7Cu and Sn-0.3Ag-0.5Cu solder bar samples were fabricated by melting of Sn, Ag and Cu metal powders. Crystal structure and element concentration were analyzed by XRD, XRF, optical microscope, FE-SEM and EDS. The fabricated solder samples were composed of β-Sn, ε-Ag3Sn and η-Cu6Sn5 phases.
In this study, we report the effect of VI/III ratio on α-Ga2O3 epilayer on sapphire substrate by halide vapor phase epitaxy. The surface of α-Ga2O3 epilayer grown with various VI/III ratios was flat and crack-free. To analyze the optical properties of the α-Ga2O3 epilayers, the transmittance and an optical band gap were measured. The optical band gap was shown to be around 5 eV and showed a proportional increase in VI/III ratios. To determine the crystal quality of alpha gallium oxide grown with a ratio of 23, closed to the theoretical optical band gap, the FWHM was measured by HR-XRD.
The calculated dislocation density of screw and edge were 1.5 × 10 7 cm−2 and 5.4 × 10 9 cm−2 , respectively