• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.374-377
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• 2008

High temperature deformation behavior and texture evolution during ECAP(equal channel angular pressing) of Zn-0.3Al alloy were investigated in this study. ECAP was conducted at temperatures from $40^{\circ}C$ to $160^{\circ}C$ on the plate type specimen of 5mm thickness and 20mm width. The specimens obtained by ECAP showed typical texture with basal poles tilted away from the ND toward ED. A series of compression tests was carried out at temperatures from RT to $200^{\circ}C$ under the strain rate from 0.03 to 10/s. With the strain rate increased, serration behavior was observed to be prominent.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.68-70
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• 2006

For the aluminum material of the thick-thickness more than 100mm Penetration depth Electron beam welding is effectively applicable with a characteristic of high energy intensity. But Al 6061 alloy has high crack sensitivity due to minor alloys, which are silicon, magnesium, copper etc. With a sample block of 135mm thickness EBW test was performed in vertical position. As tensile strength has $210{\sim}220N/mm^2$ with weld area broken. Bend test shows low ductility with fracture of partly specimens. Chemical contents of alloys show no difference between weld and base metal. Defect in middle weld area figures out typical hot crack due to low melting materials. Micro structure of weld area has some difference compare to HAZ and base metal. As a result of EBW test for Al 6061 alloy, it shows that weld defect could be occurred even though establishing of optimum weld parameter condition.

• Journal of the Korean institute of surface engineering
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• v.31 no.1
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• pp.3-11
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• 1998

Molten Carbonate Fuel cell is a promising new type electric power generation system which can achieve high efficiency, lower matrrial cost and high operating temperature Making internal reforming possible. Although the development of the MCEC is progressing rapidly toward commercialization, two important tchological problems such as dissolution of NiO cathode and not corrosion of metallic separator plate must be resolved. Because MCFC is operated at $650^{\circ}C$ and the electrolyte is very corrosive, corrosion-resistance of separator plated against oxidation abd molten carbonate is required. Al-coating on separator material for corrosion-resistance was carried out by painting, thermal spraying. hot dipping and vacuum vapour deposition. The corrosion of Al-coated STS 316S and 316L in molten carbonate at $700^{\circ}C$was studied. Vacuum vapour deposition and thermal spraing for Al-coating on STS 310S and 316L were the most effective methods for protecting thestainless steel corrosion in molten carbonate.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.215-215
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• 2014

Composites layer of Al-Cr-Ni-O system was prepared on a steel plate by hydro-thermal process at $700^{\circ}C$ for 12 hours, which phase identification and thermal conductivity were determined. The composites layer consisted of aluminum nitride, alumina, chromium carbide and aluminium, which density was $3.7kg/m^3$. The thermal conductivity of the coating layer determined by thermal data acquisition system was about 98.0 W/m/ which depended on the AlN content. Numerical modelling of the heat transfer behavior of the coating layer was well agreement with the empirical data.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.4
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• pp.154-159
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• 2001

(Li,Al)$MnO_2(OH)_2$:Co compound was synthesized by hydrothermal method. $MnO_2$, LiOH.$H_2$O, $Co_3O_4$ and $Al(OH)_3$ were used as starting materials and the optimum conditions for synthesis of monolithic (Li,Al)$MnO_2(OH)_2$:Co compound were as follows : reaction temperature; $200^{\circ}C$, reaction time; 3 days, hydrothermal solvent; 3M-KOH solution, reaction apparatus; seesaw type, atomic ratio of Li:Al:Mn;Co = 1:2.1:2.5~2:0.5~1. Monolithic(Li,Al)$MnO_2(HO)_2$:Co compound synthesized in this work had a god crystallinity and excellent color forming effect as a blue pigment compatible with natural mineral. The particles of the synthesized (Li,Al)$MnO_2(OH)_2$:Co compound have hexagonal plate shape with the size of 0.5~1 $\mu\textrm{m}$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.185-185
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• 2016

아크릴계 수지(resin)에 인조 흑연과 탄소나노튜브(carbon nanotube)를 1:1 비율로 혼합한 충전제(filler)와 용제(solvent) 및 기타 첨가제(additives)를 혼합하여 방열도료를 제조하여 수직방향 열전도도를 상온에서 평가하였다. 충전제의 함량을 1, 2, 5 중량 %로 변화시키며 원료들을 준비하여 교반기로 혼합한 뒤 3단 롤 밀(three roll mill)로 분산공정을 진행하여 3 종류의 도료를 제조하였다. 제조한 도료를 가로 11 mm, 세로 11 mm, 두께 0.4 mm의 Al 5052 알루미늄 기판에 스프레이 코팅 방식으로 도포한 후 $150^{\circ}C$에서 30분 동안 열경화 건조 과정을 거쳐 샘플을 제작하였다. 측정 시료의 형상은 대략적으로 Fig. 1과 같다. 열전도도는 식 $k={\alpha}{\cdot}C_p{\cdot}{\rho}$를 사용해서 계산된다. 여기서 k는 열전도도($W/m{\cdot}K$), ${\alpha}$는 열확산계수($mm^2/s$), $C_p$는 비열($J/kg{\cdot}K$), ${\rho}$는 밀도($g/cm^3$)를 나타낸다. 열확산계수는 독일 NETZSCH 사의 Laser Flash Analysis 장비(모델명 LFA 457)를 사용하여 측정하였는데, 기판 뒤쪽에서 레이저를 조사하고 도료층 전면에서 적외선 온도센서를 통해 시간에 따른 온도 상승곡선을 구한 후, 두 물체의 계면에서의 접촉 열저항(contact thermal resistance)을 감안하여 장비에 내장되어 있는 소프트웨어로 열확산계수가 계산된다. 비열은 같은 회사의 DSC(Differential Scanning Calorimetry) 200 F3 장비를 사용해 측정했으며, 밀도는 부피와 질량을 측정한 값을 이용하여 계산하였다. 도료를 도포하지 않은 bare Al plate에 대해서는 쉽게 열확산계수, 비열, 밀도를 측정하여 열전도도를 구할 수 있다. 도료가 코팅된 샘플에 대해서는 도료층을 일부 떼어내 비열을 측정하고, 밀도를 구한 후, 도료층의 열전도도가 2-layer 법으로 장비 내장 소프트웨어로 계산된다, 이때 Al 기판의 열확산계수, 비열, 밀도는 미리 측정한 bare Al plate의 값을 적용하였다. 실험 결과를 Table 1에 정리하였다. 흑연과 탄소나노튜브를 혼합한 충전제를 함유한 아크릴 복합체 박막에서 측정된 열전도도는 보통 고분자 재료의 열전도도 값의 상한 영역에 육박하는 값이며, 충전제 함량이 증가할수록 열전도도가 증가하는 경향을 보이고 있다.

• Composites Research
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• v.12 no.3
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• pp.1-7
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• 1999

New hybrid composite material CPAL(Carbon Patched ALuminum alloy), an Al2024-T3 plate doubleside reinforced with carbon/epoxy laminates were made. Fatigue crack growth tests were carried out at R=0.2, 0.5 in the CPAL specimens. The retardation mechanism and behavior of fatigue crack growth were examined basing on investigation of the crack and the delamination using a X-Ray and a ultrasonic C-Scan. The fatigue crack growth rates of CPAL specimens were remarkedly retarded compared to that of the Al2024-T3 specimen. The retardations amounts of the fatigue crack growth rates get higher in $0^{\circ}$/$90^{\circ}$ CPAL specimen than in $\pm$$45^{\circ}$ CPAL specimen, and get higher at R=0.2 than at R=0.5. The retardation of fatigue crack growth rates in CPAL specimen was generated by the crack bridging mechanism, that is the behavior that the fibers in CFRP layers decrease the COD in the Al2024-T3 plate.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.134-143
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• 1997

The formation of thick alloyed layer with high Si content have been investigated on the surface of Al alloy (A5083) plate by PTA process with Si powder. Hardening characteristics and wear resistance of alloyed layer was examined in relation to the microstructure of alloyed layer. Thick hardened layer in mm-order thickness on the surface of A5083 plate can be formed by PTA process with wide range of process condition by using Si powder as alloying element because of eutectic reaction of Al-Si binary alloy. High temperature and rapid solidification rate of molten pool, which are features of PTA process, enable the formation of high Si content alloyed layer with uniform distribution of fine primary Si paticle. High plasma arc current was beneficial to make the alloyed layer with smooth surface appearance in wide range of powder feeding rate, because enough volume of molten pool was necessary make alloyed layer. Uniform dispersion of fine primary Si particle with about 30${\mu}{\textrm}{m}$ in particle size can be obtained in layer with Si content ranging from 30 to 50 mass %. Hardness of alloyed layer increased with increasing Si content, but increasing rate of hardness differed with macrostructure of alloyed layer. Wear resistance of alloyed layer depended on $V_{si}$(volume fraction of primary Si) and was remarkably improved to two times of base metal at 20-30% $V_{si}$ without cracking, but no more improvement was obtained at larger $V_{si}$.

• Journal of Powder Materials
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• v.17 no.1
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• pp.13-22
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• 2010

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. $\beta$-SiC powder with 0, 2, 6, 10 wt% of $\alpha$-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at $1700-1850^{\circ}C$ for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at $100^{\circ}C/min$, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to $1700^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at $1750^{\circ}C$ and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of $\alpha$-SiC seeds into $\beta$-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the $\alpha$-SiC seeds added in $\beta$-SiC, the rate of grain growth decreased with $\alpha$-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.

• Journal of radiological science and technology
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• v.14 no.1
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• pp.49-60
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• 1991

Thermoluminescent phosphors, which are now being used widely in radiation dosimetry, have an excellent sensitivity to ionizing radiation. In this study, thermoluminescent phosphors of $CaSO_4$ : Mn, $CaSO_4$ : Dy and $CaSO_4$ : Tm are prepared and their physical properties are investigated by measuring the trapping parameters and their luminescent spectra. By considering the sensitivity to X-ray and fading characteristics, $CaSO_4$ : Dy is most adequate to imaging plate. The imaging plate are prepared by coating the $CaSO_4$ : Dy powder on the Al substrate and its dose dependence is linear within the range of 40 mGy-20 Gy X-ray. The sensitivity of imaging plate depends linearly on the thickness of coated phosphor layer up to $35\;mg/cm^2$ and is independent on the grain size of the phosphor in the range of $70{\sim}250\;{\mu}m$. By photographing the imaging plate, X-ray images of the test object are obtained and better than those of X-ray films.