• Title, Summary, Keyword: Oxidized powder

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The Study on the Production of Reaction Bonded Aluminum Oxide by Using Microwave Energy (마이크로파 에너지를 이용한 저수축 반응소결 알루미나의 제조에 관한 연구)

  • 박정현;안주삼
    • 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.

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Influence of MAO Conditions on TiO2 Microstructure and Its Photocatalytic Activity (MAO 공정 변수가 TiO2 산화피막의 구조 및 광촉매 특성에 미치는 영향)

  • Kim, Jeong-Gon;Kang, In-Cheol
    • Journal of Korean Powder Metallurgy Institute
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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.

$Ga_2O_3$ synthesis using GaN mono-crystal powder and its structural properties (GaN 단결정 분말을 이용한 $Ga_2O_3$ 합성 및 구조 특성)

  • Pang, Jin-Hyun;Ko, Jung-Eun;So, Dae-Young;Kim, Young-Soo;Kim, Chong-Don
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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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 $1124^{\circ}C{\sim}1300^{\circ}C$.

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Effect of Partially Oxidized Ti Powder on Electrical Properties and Microstructures of $BaTiO_3$-based Ceramics ($BaTiO_3$계 세라믹스의 전기적 성질과 미세조직에 미치는 부분산화 Ti 분말 첨가의 영향)

  • Kim, Jun-Gyu;Jo, Won-Seung;Park, Gyeong-Sun
    • Korean Journal of Materials Research
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    • v.10 no.10
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    • pp.671-676
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    • 2000
  • $BaTiO_3$-based ceramics with partially oxidized Ti powders were prepared by sintering at $1350^{\circ}C$ for 1 h in v vacuum, and then heated in air. In this study, the effect of partially oxidized Ti powders on electrical properties and microstructures of $BaTiO_3$-based ceramics was investigated. It was found out that the semiconductive $BaTiO_3$-based ceramics beζame to show excellent PTCR (more than $10^5$) characteristic by adding 5~7 vol% of partially oxidized Ti powder. Also, it was found out that the sintered compact had extremely porous and fine-grained microstructure. The relative density and grain size of sintered compact with 5 vol% of partially oxidized Ti powders were 54% and $1.3\;{\mu\textrm{m}}$, respectively. The mechanism for the development of PTCR characteristic in $BaTiO_3$-based ceramics with partially oxidized Ti powders due to the adsorption of oxygen at grain boundaries, and could be explained, based on Heywang model.

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Effect of UO2+x Powders Produced at Different Oxidation Temperatures on the Properties of Pellet

  • Yoo, Ho-Sik;Lee, Seung-Jae;Kim, Jae-Ik;Song, Kun-Woo
    • 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.

High-temperature Oxidation of Fe-2%Ni Alloys (Fe-2%Ni 합금의 고온 산화)

  • Lee, Dong Bok;Jung, Jae Ok;Park, Soon Yong;Cho, Gyu Chul;Xiao, Xiao;Kim, Min Jung
    • 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.

Oxidation Behavior of WC-TiC-TaC Binderless Cemented Carbide under Low Partial Pressure of Oxygen

  • Uchiyama, Yasuo;Ueno, Shuji;Sano, Hideaki;Tanaka, Hiroki;Nakahara, Kenji;Sakaguchi, Shigeya;Nakano, Osamu
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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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.

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Investigation About Surface Microstructure of Aluminum with Change of Voltage, a Period of Treatment and Density of Electrolyte in Micro-Arc Oxidation Treatment (MAO(Micro-Arc Oxidation) 공정 중 인가 전압, 반응 시간, 전해액 농도에 따른 알루미늄의 표면 미세조직 평가)

  • Yeo, In-Chul;Kang, In-Cheol
    • Journal of Korean Powder Metallurgy Institute
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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.

EffEct of vacuum annealing on an oxidation of milled WC-Co powder (분쇄된 초경합금 분말의 산화에 미치는 진공열처리 효과)

  • 김소나
    • Journal of Korean Powder Metallurgy Institute
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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.

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The Oxidation Behavior of Sintered STS 316L at High-Temperature in the Air (STS 316L 소결체의 대기중 고온산화 거동)

  • Kim, Hye Seong;Lee, Jong Pil;Park, Dong Kyu;Ahn, In Shup
    • Journal of Korean Powder Metallurgy Institute
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    • v.20 no.6
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    • pp.432-438
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    • 2013
  • In this study, analysis on the oxidation behavior was conducted by a series of high-temperature oxidation tests at both $800^{\circ}C$, $900^{\circ}C$ and 1000 in the air with sintered STS 316L. The weight gain of each oxidized specimen was measured, the oxidized surface morphologies and composition of oxidation layer were analyzed with Scanning Electron Microscope-Energy Dispersive x-ray Spectroscopy (SEM-EDS), finally, the phase change and composition of the oxidized specimen were shown by X-Ray Diffraction (XRD). As a result, the weight gain increased sharply at $1000^{\circ}C$ when oxidation test was conducted for 210 hours. Also, a plentiful of pores were observed in the surface oxidation layers at $900^{\circ}C$ for 210 hours. In addition, the following conclusions on oxidation behavior of sintered STS 316L can be obtained: $Cr_2O_3$ can be formed on pores by influxing oxygen through open-pores, $(Fe_{0.6}Cr_{0.4})_2O_3$ can be generated on the inner oxidation layer, and $Fe_2O_3$ was on the outer oxidation layer. Also, $NiFe_2O_4$ could be precipitated if the oxidation time was kept longer.