• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.385-386
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• 2006

For attaining optimum fatigue resistance of PM steels, high density levels are necessary. In this work, sintered steels Fe-1.5%Mo-0.6%C and Fe-1.5%Cr-0.2%Mo-0.6%C were produced with density levels of 7.1 to $7.6\;g.cm^{-3}$. Ultrasonic fatigue testing with 20 kHz was performed in push-pull mode up to 10E9 cycles. It was shown that the fatigue endurance strength is strongly improved by higher density levels, but also higher sintering temperatures are beneficial. The Cr-Mo steels proved to be superior to the plain Mo alloyed, due to a more favourable as-sintered matrix microstructure.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.351-351
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• 2003

• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 춘계 학술발표강연 및 논문개요집
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• pp.92-92
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• 2002

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 하계학술연구발표회 논문개요집
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• pp.28-29
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• 2004

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1998년도 추계학술발표회 초록집
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• pp.51-52
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• 1998

• 한국분말재료학회지
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• 제8권3호
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• pp.207-209
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• 2001

Nano particles have recently been a major research interest, motivated by their unusual physical and chemical properties. Such particles can be synthesized using physical and chemical methods. The physical methods need expensive installation like vacuum induction furnace, whereas in chemical methods the process in generally very simple and low cost. In this study, simple and new fabrication process by using ultrasound was investigated to prepare the nano-sized metal particles on various powders at room temperature.

• Carbon letters
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• 제24권
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• pp.97-102
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• 2017

Graphite fibers are materials with a high specific modulus that have attracted much interest in the aerospace industry, but their high manufacturing cost and low yield are still problems that prevent their wide applications in practice. This paper presents a laser-based process for graphitization of carbon fiber (CF) and explores the effect of laser radiation on the microstructure of CF. The obtained Raman spectra indicate that the outer surface of CF evolves from turbostratic structures into a three-dimensional ordered state after being irradiated by a laser. The X-ray diffraction data revealed that the growth of crystallite was parallel to the fiber axis, and the interlayer spacing $d_{002}$ decreased from 0.353 to 0.345 nm. The results of scanning electron microscopy revealed that the surface of irradiated CFs was rougher than that of the unirradiated ones and there were scale-like small fragments that had peeled off from the fibers. The tensile modulus increased by 17.51% and the Weibull average tensile strength decreased by 30.53% after being irradiated by a laser. These results demonstrate that the laser irradiation was able to increase the graphitization degree of the CFs, which showed some properties comparable to graphite fibers.

• 폴리머
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• 제31권4호
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• pp.343-348
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• 2007

이 논문에서는 vinylidene fluoride(VDF), trifluoroethylene(TrFE), chlorotrifluoroethylene(CTFE)을 사용하여 3성분계 고분자를 합성하였으며, 저온 개시제 di-tertiary-butylperoxide(DTBP)를 사용하여 현탁중합하였다. NMR, FT-IR을 통해 3성분계 고분자 사슬의 미세구조, 사슬형태의 변화에 대해 알 수 있었다. CTFE mol%가 증가할수록 $\beta$ 상태는 점차적으로 감소하고 $\gamma$ 상태는 증가하는 것을 알 수 있었다. DSC 분석결과, CTFE mol%가 증가할수록 상전이 온도($T_c$)는 상온으로 낮아지며 그 곡선은 점차 작아지고 넓게 퍼지는 현상을 확인하였다. 활성화 에너지는 Freeman-Carroll법에 의해 계산되었다.

• 한국세라믹학회지
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• 제31권7호
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• pp.731-738
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• 1994

TiN films were deposited on high speed steels by plasma assisted chemical vapor deposition (PACVD), cathode arc ion plating (CAIP) and reactive magnetron sputtering (RMS). The properties of the films deposited by the three different methods were compared. The preferred oriented plane of PACVD-TiN is (200) and those of CAIP-TiN and RMS-TiN are (111). PACVD-TiN shows a dome surface and a microstructure having small grains. CAIP-TiN shows the highest microhardness and the best adhesion strength of the three because it has a dense microstructure and an ill-defined interface. But is shows the greatest surface roughness due to the Ti droplet created by the arc. RMS-TiN shows a microstructure having large voids so that its properties in microhardness and adhesion are the worst of the three.

• Corrosion Science and Technology
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• 제2권1호
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• pp.30-35
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• 2003

In this study, sand cast AZ91E and zirconium grain refined MEZ are representative of two typical groups of magnesium alloys: those containing aluminium and those containing no aluminium but with zirconium as a grain refiner. The corrosion performance of these two alloys was evaluated and compared in 5%wt NaCI solution through measurements of weight loss and polarisation curves and examination of microstructure. Corrosion damage of AZ91E was deeper and more localised than that of MEZ, while MEZ had a lower rate of cathodic hydrogen evolution and a higher rate of anodic dissolution than AZ91E. These differences in behaviour can be related to the differences in microstructure and chemical composition between the two alloys.