• 한국재료학회지
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• 제11권12호
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• pp.1035-1041
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• 2001

The refining process and solubility of Ti in Al matrix during mechanical alloying (MA) were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) as functions of alloy composition, milling time and ball to powder ratio (BPR). Mechanical alloyed samples were annealed for investigating their stability and the formation behavior of$Al_3Ti$in the temperature range from$200{\circ}C$to$600{\circ}C$. It is observed from present experimental that disappearance of Ti peaks in mechanically alloyed Al-10wt%Ti is not simply attributable to the dissolution of Ti into Al, but associated mainly with extreme refining and/or heavy straining of Ti particles The annealing of the mechanically alloyed Al-Ti powders show differences in aluminide formation behavior when Ti content in Al is equal to or less than l0wt% and higher than l5wt%Ti. When Ti-content in Al is equal to or less than l0wt%, the MA powders transform directly to a global equilibrium state forming $DO_{22}- type\;Al_3$Ti above$400{\circ}C$. In the Al-Ti samples with equal to or higher than l5wt%Ti, transitional phases of cubic$Al_3Ti$and tetragonal $Al_{24}Ti_8$ are formed above$400{\circ}C$. They are stable only below$500{\circ}C$, and, $DO_{22}-type\;Al_3Ti$ becomes dominant aluminide at temperature higher than$ 600{\circ}C$.

• 전기화학회지
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• 제13권4호
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• pp.270-276
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• 2010

기공 경사화된 마이크론 단위의 구조 틀 및 나노 수지상 구조 벽을 가지는 니켈-구리 거품 전극을 전기화학적인 방법으로 합성하였다. 전해 도금 시 순수한 니켈은 치밀한 층으로 성장하는 양상을 보였으나, 구리와 함께 도금시키는 경우 그 성장 양상이 순수한 니켈과는 매우 다르게 관찰되었다. 특히, 첨가제로써 염소 이온의 농도가 증가함에 따라 니켈-구리 도금 층의 수지상 성장이 뚜렷해지는 모습을 보였다. 또한, 기재와 먼 부분일수록 도금 층 내 구리 대비 니켈의 상대적인 양이 감소하였으며, 염소 이온 농도가 높아짐에 따라 전 도금 층에 걸쳐 니켈의 양이 증가하였다. 수지상 구조 벽의 가지 내부 조성을 분석한 결과, 중심부로 갈수록 구리 함량이 점차 높아지는 조성 구배를 확인하였으며, 적절한 열처리를 통해 상호 확산을 유도하여 균일한 조성의 니켈-구리 합금을 얻어낼 수 있었다. 본 연구를 통해 제작된 재료는 기능성 전기 화학 장치용 고성능 전극에 활용될 수 있을 것으로 기대된다.

• 한국결정성장학회지
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• 제8권3호
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• pp.463-467
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• 1998

조성이 $Nb_3Sn$인 Nb와 Sn 혼합분말에 대해 기계적 합금화 과정중의 미세구조 변화를 X선회절실험으로 관찰하였다. 분쇄시간에 따른 결정구조 변화는 볼/분말미와 볼의 크기에 따라 변하였다. 지름이 9.5mm인 볼을 사용한 경우, 각 분말들이 초기에는 기계적으로 합금되어 A15구조를 갖는 상을 형성하였고, 그 이후에는 비정질화가 이루어졌다. 지름이 작은 3.968mm인 볼을 사용한 경우 초기에 비정질화하였다. 이들 결과들은 볼크기에 따라 분쇄에너지 효과가 다르기 때문이라고 생각될 수 있다. 순수한 $Nb_3Sn$ 화학양론조성의 상이 기계적 합금화 방법으로 제조된 과포화 고용체를 열처리하여 쉽게 얻어졌다. 기계적 합금화로 비정질화된 분말을 열처리한 경우, Nb3Sn과 Nb6Sn5상의 혼합물이 얻어졌다.

• Corrosion Science and Technology
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• 제6권3호
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• pp.128-132
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• 2007

For a quantitative inspection on the performance of weathering steel bridges, we have investigated the relationship between the corrosion rate and the composition of the rust layers formed on weathering steel bridges located in various environments in Japan and applied a protective ability index (PAI) to the bridges. The corrosion rates were clearly classified by the PAI, ${\alpha}/{\gamma}*$ and sub index of $({\beta}+s)/{\gamma}*$, where $\alpha$, \gamma*, $\beta$ and s are the mass ratio of crystalline $\alpha-FeOOH$, the total of $\gamma$-FeOOH+ $\beta$-FeOOH + the spinel-type iron oxide (mainly $Fe_3O_4$), $\beta-FeOOH$ and spinel-type iron oxide, analyzed by powder X-ray diffraction, respectively. In the case of ${\alpha}/{\gamma}$*>1, the rust layer works protective enough to reduce the corrosion rate less than 0.01 mm/y. The sub index $({\beta}+s)/{\gamma}*$<0.5 or >0.5 classifies the corrosion rate of the non-protective rust layers, therefore the former state of the rust layer terms inactive and the latter terms active. The quantitative inspection of a weathering steel bridge requires a performance-inspection (PI) and periodical deteriorationinspections (DI). The PI can be completed by checking of the PAI, ${\alpha}/{\gamma}*$. The DI on the weathering steel bridges where deicing salt is sprinkled can be performed by checking the PAI, $({\beta}+s)/{\gamma}*$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.436-439
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• 2002

Recently, It has performed that the basic research of the photoconductive material and the development and application of the digital radiograph detector which is divided into the direct and indirect method. The objective of this study investigate the effect of the electric characteristic about changing the composition of Arsenic in hybrid detector system for compensating a defect of conventional. We fabricated samples using the amorphous Selenium and Arsenic alloy with various concentrations of the Arsenic{seven step 0.1%, 0.3%, 0.5%, 1%, 1.5%, 3%, 5%). And using EFIRON optical adhesives the formed multi-layer$(Gd_{2}O_{2}S(Eu^{2+}))$ composed phosphor layer. X-ray and light sensitivity was measured to study x-ray response characteritics. As results, highest value was measured as output net charge and SNR were $315.7pC/cm^2/mR$ and 99.4 at 0.3%As doping ratio.

• 한국자기학회지
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• 제15권6호
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• pp.311-314
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• 2005

본 연구에서는 Al-Oxide(AIOx) 에 Ti를 첨가하여. Ti 함량에 따라 자기터널접합의 자기터널링 현상 변화 및 TiA l합금박막의 미세구조, 표면거칠기 변화를 관찰하였다. Ti를 첨가한 TiAlOx 절연층을 사용하여 기존 AlOx를 사용한 경우 보다 높은 터널링 자기저항(Tunneling Magnetoresistance, TMR) 비를 가지는 자기터널접합을 제작하였다. TMR 비의 증가 요인은 Ti를 첨가함에 따라, TiAl 합금박막의 입계가 작아지고, 치밀한 구조를 가져, 우수한 계면평활도를 가지는 균일한 TiAlOx 절연층이 형성되어, 소자의 구조적 안정성이 향상되었기 때문으로 분석하였다. 또한 향상된 구조적 안정성으로 인해 소자의 열적, 전기적 안정성도 크게 증가하였다.

• 대한금속재료학회지
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• 제48권4호
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• pp.357-362
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• 2010

Ferromagnetic Mn-Al nanoparticles were prepared using a plasma arc discharge method. The influence of the process parameters on the vaporization rate, composition, particle size, and magnetic properties of the as-produced nanoparticles was investigated. The Mn content was found to be higher in the nanoparticles than in the corresponding mother materials, although the difference diminished with the reaction time. As the $H_2$ content in the reaction gas increased, both the vaporization rate and the particle size increased. With 30 at.% Mn, the average particle diameter was 35.2 nm under a pure Ar gas condition, whereas it was 95.4 nm at a Ar:$H_2$ ratio of 60:40. With the addition of a small amount of carbon, ${\varepsilon}$-phase nanoparticles were successfully synthesized. After a heat treatment in a vacuum for 30 min at $500^{\circ}C$, the nonmagnetic ${\varepsilon}$-phase was transformed into the ferromagnetic ${\tau}$-phase, and a very high coercivity of nearly 5.6 kOe was achieved.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1340-1345
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• 2018

Mo-10 at.% Cu nanocomposite powders were fabricated by using planetary ball-milling (PBM), a mechanical alloying technique for preparing nanocomposite alloy powders of metals with mutual insolubility, and the variations in the physical and the chemical characteristics with the process conditions were investigated. We observed that Mo-10 at.% Cu was an appropriate composition to ensure a good alloying grade and minimal welding between particles. The influences of the temperature and the milling conditions on the mechanical alloying process and the phase change of Mo-10 at.% Cu composite powders were investigated, and the particle and the grain sizes of the powders after mechanical alloying were confirmed. The Mo-10 at.% Cu powders showed homogeneous elemental distributions and no phase changes up to $1200^{\circ}C$; their compositions were retained after the mechanical alloying process. The finest grain size obtained was about 5 nm for powders processed using optimum PBM processing conditions: ball-to-powder weight ratio of 5 : 1, ambient air atmosphere, a milling time of 20 h, a rotation speed of 200 rpm, and a stearic acid content of 4 wt.% produced superfine-grained Mo-10 at.% Cu nanocomposite powders with an average grain size of 5 nm (which is smaller than that of other similar materials reported in the literature). The analytical results confirmed that the PBM technique presented here is a promising method for preparing superfine-grained Mo-10 at.% Cu powders with improved properties.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.328-331
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• 2012

With the recent development of super-precision optical instruments, camera modules for devices, such as portable terminals and digital camera lenses, are increasingly being used. Since an optical lens is usually produced by high-temperature compression molding methods using tungsten carbide (WC) alloy molding cores, it is necessary to develop and study technology for super-precision processing of molding cores and coatings for the core surface. In this study, Rhenium-Iridium (Re-Ir) thin films were deposited onto a WC molding core using a sputtering system. The Re-Ir thin films were prepared by a multi-target sputtering technique, using iridium, rhenium, and chromium as the sources. Argon and nitrogen were introduced through an inlet into the chamber to be the plasma and reactive gases. The Re-Ir thin films were prepared with targets having a composition ratio of 30 : 70, and the Re-Ir thin films were formed with a 240 nm thickness. Re-Ir thin films on WC molding core were analyzed by scanning electron microscope (SEM), atomic force microscope (AFM), and Ra (the arithmetical average surface roughness). Also, adhesion strength and coefficient friction of Re-Ir thin films were examined. The Re-Ir coating technique has received intensive attention in the coating processes field because of promising features, such as hardness, high elasticity, abrasion resistance and mechanical stability that result from the process. Re-Ir coating technique has also been applied widely in industrial and biomedical applications. In this study, WC molding core was manufactured, using high-performance precision machining and the effects of the Re-Ir coating on the surface roughness.

• 한국재료학회지
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• 제14권9호
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• pp.607-613
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• 2004

This study was to investigate the surface properties of electrochemically oxidized Ti-6Al-7Nb alloy by anodic spark discharge technique. Anodizing was performed at current density 30 $mA/cm^2$ up to 300 V in electrolyte solutions containing $DL-{\alpha}$-glycerophosphate disodium salt hydrate($DL-{\alpha}$-GP) and calcium acetate (CA). Hydrothermal treatment was done at $300^{\circ}C$ for 2 hrs to produce a thin outermost layer of hydroxyapatite (HA). The bioactivity was evaluated from HA formation on the surfaces in a Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. The size of micropores and the thickness of oxide film increased and complicated multilayer by increasing the spark forming voltage. Needle-like HA crystals were observed on anodic oxide film after the hydrothermal treatment at $300^{\circ}C$ for 2 hrs. When increasing $DL-{\alpha}$-GP in electrolyte composition, the precipitated HA crystals showed the shape of thick and shorter rod. However, when increasing CA, the more fine needle shape HA crystals were appeared. The bioactivity in Hanks' solution was accelerated when the oxide films composed with strong anatase peak with presence of rutile peak. The increase of amount of Ca and P was observed in groups having bioactivity in Hanks' solution. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal and it was closer to 1.67 as increasing the immersion time in Hanks' solution.