• Title/Summary/Keyword: Materials science and engineering

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Effect of Carbon on Wear Resistance in Self-lubricating Fe-Cr-C-Mn-Cu Alloys

  • Kim, Ki Nam;Shin, Gyeong Su;Park, Myung Chul;Lee, Sung Yong;Yun, Jae Yong;Kim, Seon Jin
    • Korean Journal of Metals and Materials
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    • v.50 no.9
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    • pp.637-643
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    • 2012
  • Recently, because of safety and environmental concerns, there has been a tendency to introduce solid self-lubricating composites for bearing materials. In this paper, we developed Fe-Cr-C-Mn-Cu cast composite alloys as a self-lubricating composite and investigated the effect of carbon on the formation of protective tribofilms during sliding. The wear resistance of these materials was mainly affected by carbon concentrations due to the fact that in particular wear passed from delamination to tribo-oxidation, reducing the wear rate. The improved wear resistance likely resulted from protective tribofilms that formed on the surface during sliding.

Use of copper tungsten oxide as a liquid phase sintering aid for barium hexaferrite

  • Fisher, John G.;Le, Phan Gia;Meng, Meng;Heo, Sang-Hyeon;Bak, Tae-Jin;Moon, Byeol-Lee;Park, In-San;Lee, Dong-Kyu;Lee, Wu-Hui
    • Journal of Ceramic Processing Research
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    • v.19 no.5
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    • pp.434-438
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    • 2018
  • The sintering behavior of $BaFe_{12}O_{19}$ with the addition of one and three weight % of $CuWO_4$ as a liquid phase sintering aid is studied. Samples are sintered in the temperature range $900-1250^{\circ}C$ and the effect of $CuWO_4$ addition on density, microstructure, phase composition and magnetic properties is examined. Compared to $BaFe_{12}O_{19}$ with no sintering aid addition, addition of 1 wt % $CuWO_4$ retards densification. Addition of 3 wt % $CuWO_4$ promotes densification at lower sintering temperatures but retards densification at temperatures > $1050^{\circ}C$. Three wt % $CuWO_4$ addition induces the formation of $BaWO_4$ and $Ba_3WFe_2O_9$ secondary phases at temperatures ${\geq}1100^{\circ}C$. Addition of $CuWO_4$ causes a decrease in saturation magnetization, remanent magnetization and coercivity.

Highly transparent Pt ohmic contact to InGaN/GaN blue light-emitting diodes

  • Chul Huh;Kim, Hyun-Soo;Kim, Sang-Woo;Lee, Ji-Myon;Kim, Dong-Joon;Kim, Hyun-Min;Park, Seon-Ju
    • Journal of Korean Vacuum Science & Technology
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    • v.4 no.2
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    • pp.47-49
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    • 2000
  • We report on the fabrication and characterization of InGaN/GaN multiple quantum well light emitting diode (LED) with a highly transparent Pt ohmic contact as a current spreading layer. The value of light transmittance of a Pt thin film with a thickness of 8 m on p-GaN was measured to be 85% at 450nm. The peak wavelength and the full-width at half-maximum (FWHM) of the emission spectrum of the LED at 20 mA were 453 m and 23 m, respectively. Pt-contacted LEDs show good electrical properties and high light-output efficiency compared to Ni/Au-contacted ones. These results suggest that a Pt thin film can be used as an effective current spreading layer with high light-transparency.

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Highly transparent Pt ohmic contact to InGaN / GaN blue light - emitting diodes

  • Huh, Chul;Kim, Hyun-Soo;Kim, Sang-Woo;Lee, Ji-Myon;Kim, Dong-Joon;Kim, Hyun-Min;Park, Seong-Ju
    • Journal of Korean Vacuum Science & Technology
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    • v.4 no.3
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    • pp.78-80
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    • 2000
  • We reprot on the fabrication and characterization of InGaN/GaN multiple quantum well light-emitting diode (LED) with a highly transparent Pt ohmic contact as a current spreading layer. The value of light transmittance of a Pt thin film with a thickness of 8 nm on-GaN was measured to be 85% at 450 nm. The peak wavelength and the full-width at half-maximum (FWHM) of the emission spectrum of the LED at 20 mA were 453 nm and 23 nm, respectively. Pt-contacted LEDs show good electrical properties and high light-output efficiency compared to Ni/Au-contacted ones. These results suggest that a Pt thin film can be used as an effective current spreading layer with high light-transparency.

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