• Journal of the Korean Ceramic Society
• /
• v.35 no.3
• /
• pp.303-309
• /
• 1998

The fabrication of Al2O3/Al composite by pressureless infiltration was investigated by the change of Mg and Si content in Al alloy infiltration process and infiltration atmosphere. The effect of alloying elements infiltration atmosphere and interfacial reactants between Al alloy matrix and Al2O3 particles were in-vestigated in terms of bendingstrength and harness test,. The fabrication of Al2O3/Al composite by the vestigated in terms of bending strength and hardness test. The fabrication of Al2O3/Al composite by the pressureless infiltration was done in nitrogen atmosphere with Mg in Al alloy. It was successfully fabricated at $700^{\circ}C$ according to Mg contents in Al alloy and infiltration condition. Because Mg in the Al alloy and ni-trogen atmosphere of infiltratio condition produced Mg-N compound(Mg3N2) it decreased the wetting an-gle between molten Al alloy and Al2O3 particles by coating on surface of Al2O3 particles. The fracture strength of Al2O3/Al-Mg composite was 800MPa and Al2O3/Al-Si-Mg composite was 400MPa. Si in Al alloy decreased the interfacial strength between Al alloy matrix and Al2O3 particles.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.260-266
• /
• 2012

Syngas and hydrogen from the $CeO_2/ZrO_2$ coated foam devices were investigated under simulated solar radiation. The $CeO_2/ZrO_2$ coated SiC, Ni and Cu foam device were prepared using drop-coating method. Syngas production step was performed at $900^{\circ}C$, and hydrogen production process was performed for ten repeated cycles to compare the CeO2 conversion in syngas production step, $H_2$ yield in hydrogen production step and cycle reproducibility. The produced syngas had the $H_2$/CO ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. In addition, syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. After ten cycles of redox reaction, the $CeO_2/ZrO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.

• Proceedings of the KWS Conference
• /
• 2004.05a
• /
• pp.324-326
• /
• 2004

l2wt%Cr Steel has been applied on turbine bucket and nozzle partition material of power plant. Turbine bucket and nozzle get damaged by solid particle within steam, therefore they are protected by surface treatments such as ion nitriding, boriding and chrome carbide HVOF spray coating. In this study, solid particle erosion(SPE) characteristics after these surface treatments are examined at operating temperature 540$^{\circ}C$ and 590$^{\circ}C$ of fossil power plant and the mechanism of damage was studied. Erosion of 12wt%Cr steel is originated by micro cutting and that of boriding and chrome carbide HVOF spray is originated by these mechanism - repeating collision, crack initiation and propagation. As the results of SPE test at 540$^{\circ}C$ and 30$^{\circ}$ impact angle that is the most commonly occurred in power plant, Boriding had the best SPE -resistance property, Cr$_2$C$_3$-25(Ni20Cr) HVOF spayed and ion nitrided samples were also better than bare metals(l2wt%Cr Steels). At 590$^{\circ}C$ and 30$^{\circ}$ impact angle, Boriding had also the most superior characteristic and HVOF spay sample was better than bare metal.

• Journal of the Korean Ceramic Society
• /
• v.49 no.2
• /
• pp.167-172
• /
• 2012

Fine diamond powders are synthesized with a 420 ${\phi}$ cubic press and stack-cell composed of Kovar ($Fe_{54}Ni_{29}Co_{17}$) (or Kovar+7 ${\mu}m$-thick Zn electroplated) alloy and graphite disks. The high pressure high temperature (HPHT) process condition was executed at $1500^{\circ}C$ for 280 seconds by varying the nominal pressure of 5.7~10.6 GPa. The density of formation, size, shape, and phase of diamonds are determined by optical microscopy, field emission scanning electron microscopy, thermal gravimetric analysis-differential thermal ammnlysis (TGA-DTA), X-ray diffraction (XRD), and micro-Raman spectroscopy. Through the microscopy analyses, we found that 1.5 ${\mu}m$ super-fine tetrahedral diamonds were synthesized for Zn coated Kovar cell with whole range of pressure while ~3 ${\mu}m$ super-fine diamond for conventional Kovar cell with < 10.6 GPa. Based on $750^{\circ}C$ exothermic reaction of diamonds in TGA-DTA, and characteristic peaks of the diamonds in XRD and micro-Raman analysis, we could confirm that the diamonds were successfully formed with the whole pressure range in this research. Finally, we propose a new process for super-fine diamonds by lowering the pressure condition and employing Zn electroplated Kovar disks.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.188-193
• /
• 2000

A more accurate life prediction for gas turbine blade takes into account the material behavior under the complex thermo-mechanical fatigue(TMF) cycles normally encountered in turbine operation. An experimental program has been carried out to address the thermo-mechanical fatigue life of the IN738LC nickel-base superalloy. In the first phase of the study, out-of-phase and in-phase TMF experiments have been performed on uncoated and coated materials. In the temperature range investigated. the deposition of NiCrAlY air plasma sprayed coating did not affect the fatigue resistance. In the second phase of the study, a physically-base life prediction model that takes into account of the contribution of different damage mechanisms has been applied. This model was able to reflect the temperature and strain rate dependences of isothermal cycling fatigue lives, and the strain-temperature history effect on the thermo-mechanical fatigue lives.

• Korean Journal of Materials Research
• /
• v.13 no.6
• /
• pp.404-408
• /
• 2003

SiC nanorods have been grown on Si (100) substrate directly. Tetramethylsilane and Ni were used for SiC nanorod growth. After 3minute, SiC nanorod had grown by CVD. Growth regions ware divided by two regions with diameter. The First region consisted of thin SiC nanorods having below 10 nm diameter, but second region's diameter was 10∼50 nm. This appearance shows by reduction of growth rate. The effect of temperature and growth time was investigated by scanning electron microscopy. Growth temperature and time affected nanorod's diameter and morphology. With increasing growth time, nanorod's diameter increased because of the deactivation effect. But growth temperatures affected little. By TEM characterization, grown SiC nanorods consisted of the polycrystalline grain.

• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.2
• /
• pp.182-188
• /
• 2007

[ $Zr_{50}-Ni_{27}-Nb_{18}-Co_5$ ] amorphous alloys ribbon was prepared by a single-roller melt-spinning technique. In order to improve the hydrogen kinetics Pd-coating were carried out on each side of the amorphous ribbon. Pd prevents oxidation of Zr and catalyses the dissociation of molecular hydrogen to atomic hydrogen. In this work, the hydrogen embrittlement and surface properties on Zr-based amorphous alloys were investigated. The Zr-based amorphous alloys were characterized by X-ray diffractometry(XRD) and differential scanning calorimetry(DSC). The morphology of surface and roughness was observed by using scanning electron microscopy(SEM) and atomic force microscopy (AFM). A lattice parameter of both Pd and Zr-based amorphous alloy was increased after hydrogen permeation at 473 K. After hydrogen permeation at 473 K, some cracks were observed on the surface of Pd, which was the cause for the hydrogen embrittlement. The crystallization temperature of Zr-based amorphous alloy was decreased due to the permeated hydrogen.

• Journal of Adhesion and Interface
• /
• v.18 no.4
• /
• pp.159-165
• /
• 2017

In this study, we synthesized UV-curable urethane acrylates with different contents of BA, reactive diluent and characterized their physical properties such as thermal, mechanical properties, adhesive strength and flexibility resistance. From a result of DSC, Tg of polyol and acrylate resin were separated as the BA content increased more than 40%. Also, tensile strength, elongation and adhesive strength decreased with increasing the BA content. The UV-curable urethane acrylate with 40% BA has shown good flexibility resistance compared to other resin due to poor hardness and Tm of acrylate resin.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.11
• /
• pp.3093-3098
• /
• 2010

The core-shell $SnO_2$@AO (A=Ni, Cu, Zn and Mg) films were prepared and the effects of coatings on photovoltaic properties were investigated. Studies on X-ray photoelectron spectroscopy, energy dispersive X-ray analysis and transmission electron microscopy showed the formation of divalent oxides on the surface of $SnO_2$ nanoparticles. It was commonly observed that all the dye-sensitized core-shell films exhibited higher photovoltage than the bare $SnO_2$ film. Transient photovoltage measurements confirmed that the improved photovoltages were related to the decreased time constants for electron recombination.

• Korean Journal of Veterinary Research
• /
• v.49 no.1
• /
• pp.39-44
• /
• 2009

Transmission of avian viruses both bird-to-bird and from birds to non-avian species is a major health concern. Newcastle disease virus (NDV) is an economically important avian virus that poses substantial risks to the poultry industry. Rapid and sensitive diagnostic methods, such as the enzymelinked immunosorbent assay (ELISA), are required to track such infections. To develop an ELISA for detecting anti-NDV antibody in avian sera, the nucleocapsid protein (NCP) gene of the NDV La Sota strain was cloned and expressed in Escherichia coli and the 513-amino acid recombinant NCP was purified by Ni-NTA affinity chromatography. To evaluate its ability to replace NDV whole virus antigen as a coating antigen, NCP-coated and whole NDV-coated ELISAs were tested and compared using a panel of NDV positive antisera from chickens. Results using purified NCP were highly correlated with those obtained using whole NDV (r= 0.927), demonstrating that recombinant NCP expressed in Escherichia coli is a suitable substitute antigen for whole NDV in a diagnostic ELISA.