• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.227-233
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• 1995

By using homestyle microwave oven, Al-Al2O3 powder mixture could be oxidized and sintered into Al2O3 body. The differences in powder characteristics among the differently processed raw materials affect the oxidation and sintering behaviours, and these effects were more pronounced in case of microwave oven than of conventional furnace. Al-Al2O3 powder mixture was oxidized and sintered within 2hrs, which could save both processing time and energy.

• Journal of Powder Materials
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• v.19 no.3
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• pp.196-203
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• 2012

$TiO_2$ was successfully formed on a Ti specimen by MAO (Micro-Arc-Oxidation) method treated in $Na_3PO_4$ electrolyte. This study deals with the influence of voltage and working time on the change of surface microstructure and phase composition. Voltage affected the forming rate of the oxidized layer and surface microstructure where, a low voltage led to a high surface roughness, more holes and a thin oxidized layer. On the other hand, a high voltage led to more dense surface structure, wider surface holes, a thick layer and fewer holes. Higher voltage increases photocatalytic activity because of better crystallization of the oxidized layer and good phase composition with anatase and rutile $TiO_2$, which is able to effectively separate excited electrons and holes at the surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.12-13
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• 2006

$Ga_2O_3$ is associated with the fabrication of thin window layer of solar cell. Usually, $Ga_2O_3$ is synthesized from Ga-metal oxidation method and GaN mono-crystal heat treatment method. We synthesized $Ga_2O_3$ powder using two methods and analyzed powder using latter method compared with powder by former method. XPS, XRD, IR analysis are conducted. XPS result, surface of GaN powder is almost oxidized to $Ga_2O_3$ at $1124^{\circ}C$ heat treatment and XRD and IR result, the inside of GaN powder is dramatically oxidized at $1124^{\circ}C{\sim}1300^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.410-414
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• 2003

Characteristics of $UO_{2+x}$ powders oxidized at different temperatures were examined. Pellets were fabricated by adding these oxidation powders and their properties were also investigated. Particle size of the $UO_{2+x}$ powders decreased with increasing oxidation temperature while surface area increased. Only the powders oxidized at 35$0^{\circ}C$ enhanced the strength of green pellet. However, 35$0^{\circ}C$ oxidized powders added pellet had many surface defects. The difference of shrinkage rate between the oxidized and UO$_2$ powders was thought to be the cause of them.

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.547-558
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• 2023

This research delves into the fabrication of an ultra-high-strength concrete, enriched with oxidized graphene nanoplatelet(GO) and hollow glass powder(HGP), notably eschewing the conventional inclusion of silica fume(SF). The primary objective was to scrutinize the autogenous shrinkage characteristics of this innovative formulation. It was discerned that the NewMix specimen, which incorporated the cGO(sourced from Company C) and HGP, and intentionally bypassed SF, showcased a commendable 13% reduction in autogenous shrinkage relative to the benchmark(Ref) specimenthat incorporated SF. Moreover, the proclivity for crack formation owing to autogenous shrinkage in the NewMix was observed to manifested by NewMix at the juncture of cracking emerged as the apex value. Attributed to the expansive specific surface area and exemplary dispersibility of cGO, it was postulated that the concrete's pore structure benefitted from enhanced infill, leading to a reduction in autogenous shrinkage. Additionally, the cGO integration fortified the concrete's resistance to crack initiation. Consequently, such an enhancement is posied to be pivotal in mitigating crack propagation resulting from autogenous shrinkage in ultra-high-strength concrete.

• Journal of the Korean institute of surface engineering
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• v.51 no.2
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• pp.104-109
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• 2018

Fe-2 wt.%Ni alloys were fabricated by metal powder injection molding, and their oxidation behavior at $600-700^{\circ}C$ for 30 h in air was studied in order to find the effect of the small addition of Ni in the iron matrix on the high-temperature oxidation. Oxide scales that formed after oxidation consisted primarily of $Fe_2O_3$, where microscopic voids were scattered. Nickel was segregated initially at the scale/matrix interface, and later at the lower part of the $Fe_2O_3$ scale. At $600^{\circ}C$, Fe-2wt.%Ni alloys oxidized parabolically initially, and linearly after 15 h. At $650-700^{\circ}C$, they oxidized linearly from the initial period. Although Fe-2wt.%Ni alloys oxidized slower than pure iron, their oxidation rates were relatively fast.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.481-485
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• 2001

Laser cladding processing allows rapid transfer of heat to the material being processed with minimum conduction into base metal. The effect of $CO_2$ laser cladding with high viscosity mixed powders was investigated. High viscosity mixed powder consists of bronze powder and flux that is used at a high temperature condition. The mixed powder has a high viscosity that it can be easily pasted over a curved or slope substrate. The device for mixed powder was designed and manufactured. It consists of the high viscosity mixed powder feeding system, the preheating system and the shielding gas system which prevents the clad layer from being oxidized. The results of experiment indicated that the feed rate of high viscosity mixed powder was important for later cladding with mixed powder feeding. The high viscosity mixed powder and substrate must be preheated to prevent porosity from breaking at the clad layer. The experimental result shows that the high viscosity mixed can be applied for laser cladding process.

• Journal of Powder Materials
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• v.3 no.2
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• pp.91-96
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• 1996

The effect of vacuum annealing on the oxidation behavior of milled WC-15%Co powder mixture has been studied. A cobalt component in the milled powder mixture was oxidized preferentially above 175$^{\circ}C$ in air. The specimens showed a steady increase in weight at 175$^{\circ}C$ but did constant weight followed by rapid increase in specimen weight at the beginning above 20$0^{\circ}C$. Oxidation of the milled powder mixture was significantly suppressed by vacuum annealing at 30$0^{\circ}C$ for 10 h. Suppression of oxidation by vacuum annealing and different oxidation behaviors of the milled powder mixture between 175$^{\circ}C$ and 20$0^{\circ}C$, were attributed to removal of strain energy stored in the cobalt powder during vacuum annealing or oxidation treatment above 20$0^{\circ}C$. The role of stored strain energy on oxidation of milled WC-15%Co powder mixture was proved by X-ray diffraction method and differential thermal analysis.

• Journal of Powder Materials
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• v.18 no.6
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• pp.575-582
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• 2011

MAO(Micro-Arc Oxidation) method was used to make $Al_2O_3$ surface on 6063 Al specimen. This study was focused on an influence of voltage, density of electrolyte and a period of treatment on the change of surface microstructure by using SEM(Scanning Electron Microscope), EDS(Energy Dispersive X-ray Spectroscopy). The microstructure shows higher roughness and thicker oxidized layer with increase of voltage and maintaining period of treatment. The density of electrolyte affected a formation of more dense surface and increase of a oxidized layer.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.355-356
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• 2006

WC-TiC-TaC binderless cemented carbide was oxidized under low partial pressure of oxygen (50ppm) at 873K for 1 to 20 h. Surface roughness was measured using atomic force microscope, and effect of TiC amount on oxidation behavior of the carbide was investigated. WC phase was oxidized more easily than WC-TiC-TaC solid solution phase. With an increase in TiC amount, WC-TiC-TaC phase increased and the oxidation resistance of the carbide increased.