• Economic and Environmental Geology
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• v.45 no.2
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• pp.79-88
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• 2012

The increased brightness and focused X-ray beams now available from laboratory X-ray sources facilitates a variety of powder diffraction experiments not practical using conventional in-house sources. Furthermore, the increased availability of 2-dimensional area detectors, along with implementation of improved software and customized sample environmental cells, makes possible new classes of in-situ and time-resolved diffraction experiments. These include phase transitions under variable pressure- and temperature conditions and ion-exchange reactions. Examples of in-situ and time-resolved studies which are presented here include: (1) time-resolved data to evaluate the kinetics and mechanism of ion exchange in mineral natrolite; (2) in-situ dehydration and thermal expansion behaviors of ion-exchanged natrolite; and (3) observations of the phases forming under controlled hydrostatic pressure conditions in ion-exchanged natrolite. Both the quantity and quality of the in-situ diffraction data are such to allow evaluation of the reaction pathway and Rietveld analysis on selected dataset. These laboratory-based in-situ studies will increase the predictability of the follow-up experiments at more specialized beamlines at the synchrotron.

• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.147-152
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• 2005

The structural evolution of $Ni(400\;\AA)/Au(400\;\AA)$ films on p-type GaN during thermal oxidation in ai. was investigated by in situ x-ray scattering experiments. These results indicate that Ni layer and Au layer intermix during thermal oxidation. Au-rich solid solutions containing the different amount of Ni atoms are formed during oxidation. The Ni atoms in Au-rich solid solution out-diffuse as the oxidation proceeds resulting in the formation of NiO(111) phase. Despite of the complete oxidation at $650^{\circ}C$, the position of bulk Au(111) diffraction profile indicates that small amount of Wi atoms are still incorporated in the Au phase.

• Polymer(Korea)
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• v.36 no.1
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• pp.88-92
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• 2012

Long-term performance of polymer under constant sustained load has been the main research focus, which created a need for the accelerated test method providing proper lifetime assessment. Cycling fatigue loading is one of the accelerated test method and has been of great interest. Microstructure change of high density polyethylene under cyclic fatigue loading and creep was examined utilizing a tensile device specially designed for creep and fatigue test and also can be attachable to the X-ray diffractometer. In this way, the crystal morphology change of polyethylene under creep and cyclic fatigue load was successfully monitored and compared. Despite the marked differences in macroscopic deformation between the creep and cyclic fatigue tests, crystal morphology such as crystallinity, crystal size, and $d$-spacing was as nearly identical between the two test cases. Specimens pre-deformed to different strains, i.e., before yield point (BYP), at yield point (YP) and after yield point (AYP), however, showed markedly different changes in crystal morphology, especially between AYP and the other two specimens.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.61-67
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• 2003

The interfacial reaction between ultra-small 58Bi-42Sn solder and Au/Ni/Ti under bump metallurgy (UBM) for ultra-fine flip chip application was investigated. The ultra-small 58Bi-42Sn solder bump, about $46{\mu}m$ in diameter, was fabricated by using the lift-off method and reflowed using the rapid thermal annealing (RTA) system. The intermetallic compounds were characterized using a secondary electron microscopy (SEM), an energy dispersive spectroscopy (EDS), and an x-ray diffractometer (XRD). The faceted and polygonal intermetallic compounds were found in the Bi-Sn solder bumps on $Au(0.1{\mu}m)/Ni/Ti$ UBM and they were indentified as $(Au_xBi_yNi_{1-x-y})Sn_2$ Phase. The intermetallic compounds grown from the $Au(0.1{\mu}m)/Ni/Ti$ UBMinterface were dispersed in the solder bump.

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.121-126
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• 2000

The effect of electroless Ni and Cu plating on $LaNi_5$, $AB_5$ type hydrogen storage alloy was investigated by the various electrochemical techniques such as constant current charge-discharge test, cyclic voltammeoy, and a.c. impedance spectroscopy. Scanning electron microscopy and X-ray diffraction test were conducted for phenomenological logical analyses. Cyclic Voltammetry results show that activation characteristics, cycle life and reaction ,rate were improved through electroless Ni and Cu plating. Compared with bare $LaNi_5$ the charge transfer resistance of electrode was greatly reduced as charge-discharge cycle increases. Therefore, electroless Ni and Cu plating on $LaNi_5$ alloy tends to accelerate the early activation, increasing the cyclic lift of electrode.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.23-30
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• 2016

Powder samples of natural lawsonite (Ca-lawsonite, $CaAl_2Si_2O_7(OH)_2{\cdot}H_2O$) was studied structurally up to 8 GPa at room temperature using monochromatic synchrotron X-ray powder diffraction and a diamond anvil cell (DAC) with a methanol : ethanol : water (16 : 3 : 1 by volume) mixture solution as a penetrating pressure transmitting medium (PTM). Upon pressure increase, lawsonite does not show any apparent pressure induced expansion (PIE) or phase transition. Pressure-volume data were fitted to a second-order Birch-Murnaghan equation of state using a fixed pressure derivative of 4 leading to a bulk modulus ($B_0$) of 146(6) GPa. This compression is further characterized to be isotropic with calculated linear compressibilities of ${\beta}^a=0.0022GPa^{-1}$, ${\beta}^b=0.0024GPa^{-1}$, and ${\beta}^c=0.0020GPa^{-1}$.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.302-302
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• 2012

본 연구에서는 아크 소스를 이용하여 TiAlN을 코팅하였으며 공정 변수 중 질소 유량에 다른 TiAlN 박막의 물성 변화를 관찰하였다. TiAlN은 고경도 난삭재의 고능률 절삭 분야에 사용되어 공구의 수명을 향상하기 위한 표면처리 소재로 각광을 받고 있다. TiAlN 박막은 아크 소스에 장착된 TiAlN 타겟(Ti-50 at %Al)을 사용하여 스테인리스 강판 위에 코팅 하였으며 이 때 기판과 타겟 간의 거리는 약 30 cm이었다. 기판을 진공용기에 장착하고 ${\sim}10^{-6}$ torr까지 진공배기를 실시한 후 아르곤 가스를 진공용기 내로 공급하여 공정 압력인 $7{\times}10^{-4}$ torr로 제어한다. 공정 압력에서 아크 소스에 약 70 A의 전류를 인가하여 아크를 발생시키고 기판 홀더에 약 -400 V의 직류전압을 인가하여 약 5분간 청정을 실시하였다. 기판의 청정이 끝나면 기판에 인가된 전압을 차단하고 질소 가스를 진공용기에 공급하여 TiAlN을 코팅하였다. 질소 유량이 30 sccm일 경우 TiAlN 박막의 경도가 약 2510 Hv로 가장 높았으며, 질소의 유량이 40 sccm 이상으로 증가할 경우 TiAlN 박막의 경도는 1500 Hv로 주목할 만한 변화는 없었다. 질소 유량이 증가하면 TiAlN 박막의 색상은 회색에서 어두운 보라색으로 변화하였고 주사전자현미경 분석을 통해서 거대 입자(macro particle)가 감소하는 경향을 확인할 수 있었으며 이는 질소 유량이 증가할수록 TiAlN 박막의 표면조도 또한 증가하는 분석결과와 일치하였다. X-선 회절 분석을 통해 질소 유량이 30 sccm 이상에서 박막의 질화가 일어나고 2500 Hv 이상의 경도를 가지는 최적 조건임을 확인하였으며, 이는 절삭 공구 등과 같이 고경도 유지를 위한 코팅 분야에 적용이 가능할 것으로 판단된다. 본 연구에서 얻어진 결과를 바탕으로 질소 유량 외에 다른 공정 조건을 변화시켜 TiAlN 코팅을 실시한다면 다양한 색상 구현, 고경도, 내마모성 등 TiAlN 박막의 기능성을 향상할 수 있을 것으로 예상된다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.1
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• pp.33-38
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• 2009

An experiment for uranium sorption onto fresh and weathered biotites was performed. After centrifugation, concentrations of uranium in the supernatants were analyzed using ICP-MS, and biotite samples were investigated using XRD and SEM. With powdered biotites (<3 mm in size), we have conducted uranium sorption experiments about fresh and weathered biotites to obtain uranium sorption amounts in various pH conditions. The uranium sorption was not high at a low pH (e.g., pH 3), but increased with increasing pH. There were lower uranium sorption by the weathered biotites than by the fresh ones, and the difference was much larger at higher pH (e.g., pH 11). The lower sorption values of uranium by the weathered biotites may be caused by a change of mineral surfaces and a chemical behavior of surrounding dissolved elements. It seems that the uranium-mineral interaction has been diminished, especially, in the weathered biotite by a destruction and dissolution of preferential sorption sites on the mineral surfaces and by the colloidal formation from dissolved elements.

• Polymer(Korea)
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• v.28 no.4
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• pp.344-351
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• 2004

Poly(ethylene glycol)-based diblock and triblock polyester copolymers stimulating to temperature were studied as injectable biomaterials in drug delivery system because of their nontoxicity, biocompatibility and biodegradability. We synthesized the diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) (M$_{n}$=750 g/mole) and poly($\varepsilon$-caprolactone) (PCL) by ring opening polymerization of $\varepsilon$-CL with MPEG as an initiator in the presence of HCl . Et$_2$O. The aqueous solution of synthesized diblock copolymers represented sol phase at room temperature and a sol to gel phase transition as the temperature increased from room temperature to body temperature. To confirm the in vivo gel formation, we observed the formation of gel in the mice body after injection of 20 wt% aqueous solution of each block copolymer. After 2 months, we observed the maintenance of gel without dispersion in mice. In this study, we synthesized diblock copolymers exhibiting sol-gel phase transition and confirmed the feasibility as biomaterials of injectable implantation.n.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.204-211
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• 2020

The high-velocity oxy-fuel (HVOF) thermal spraying coating technique has been considered a promising replacement for traditional electrolytic hard chrome plating (EHC), which caused environmental pollution and lung cancer due to toxic Cr⁶⁺. In this paper, two types of cermet coatings were prepared by HVOF spraying: WC-CoCr and WC-CrC-Ni coatings. The produced coatings were analyzed extensively in terms of the micro-hardness, porosity, crystalline phase and microstructure using a hardness tester, optical microscopy, X-ray diffraction, and scanning electron microscopy (including energy dispersed spectroscopy (EDS)), respectively. The wear and friction behaviors of the coatings were evaluated comparatively by reciprocating sliding wear tests at 25 ℃, 250 ℃, and 450 ℃. The results revealed correlations among the microstructures, metallic binder matrixes, porosities, and wear performance of the coatings. For example, WC-CoCr coatings showed better sliding wear resistance than WC-CrC-Ni coatings, regardless of the test temperature due to the more homogeneous microstructure, Co-rich, Cr-rich metallic binder matrix, and lower porosity.