• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.74-74
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• 2018

Ti-6Al-4V alloys have been widely used as orthopedic materials because of their excellent corrosion resistance and mechanical properties. However, it does not bind directly to the bone, so it requires a surface modification. This problem can be solved by nanotube and micropore formation. Plasma electrolytic oxidation (PEO) treatment for micropore, which combines high-voltage spark and electrochemical oxidation, is a new way of forming a ceramic coating on light metals such as titanium and its alloys. This method has excellent reproducibility and can easily control the shape and size of the Ti alloy. In this study, formation of bioactive surface by PEO-treatment after $2^{nd}$ ATO technique of Ti-6Al-4V alloy was invesgated by various instrument. Nanotube oxide surface structure was formed on the surface by anodic oxidation treatment in 0.8 wt.% NaF and 1M $H_3PO_4$ electrolytes. After nanotube formation, nanotube layer was removed by ultrasonic cleaning. PEO-treatment was carried out at 280V for 3 minutes in the electrolytic solution containing the bioactive substance (Mg, Zn, Mn, Sr, and Si). The surface of Ti-6Al-4V alloy was observed by field emission scanning electron microscopy (FE-SEM, S-4800 Hitachi, Japan). An energy dispersive X-ray spectrometer (EDS, Inca program, Oxford, UK) was used to analyze the spectra of physiologically active Si, Mn, Mg, Zn, and Sr ions. The PEO film formed on the Ti-6Al-4V alloy surface was characterized using an X-ray diffractometer (TF-XRD, X'pert Philips, Netherlands). It is confirmed that bioactive ions play an essential role in the normal bone growth and metabolism of the human skeletal tissues.

• 한국재료학회지
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• 제28권1호
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• pp.68-74
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• 2018

Cobalt-incorporated zeolitic imidazolate framework ZIF-8 was synthesized by a simple one-pot synthesis method at room temperature. Powder X-ray diffraction patterns and energy dispersive X-ray spectrum confirmed the formation of the bimetallic Co/Zn-ZIF structure. UV-Vis diffuse reflectance spectra revealed that the bimetallic ZIF had a lower HOMO-LUMO gap compared with ZIF-8 due to the charge transfer process from organic ligands to cobalt centers. A hydrolytic stability test showed that Co/Zn-ZIF is very robust in aqueous solution - the most important criterion for any material to be applied in photodegradation. The photocatalytic efficiency of the synthesized samples was investigated over the Indigo Carmine (IC) dye degradation under solar simulated irradiation. Cobalt incorporated ZIF-8 exhibited high efficiency over a wide range of pH and initial concentration. The degradation followed through three distinct stages: a slow initial stage, followed by an accelerated stage and completed with a decelerated stage. Moreover, the photocatalytic performance of the synthesized samples was highly improved in alkaline environment rather than in acidic or neutral environments, which may have been because in high pH medium, the increased concentration of hydroxyl ion facilitated the formation of hydroxyl radicals, a reactive species responsible for the breaking of the Indigo Carmine structure. Thus, Co/Zn-ZIF is a promising and green material for solving the environmental pollution caused by textile industries.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3761-3766
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• 2012

$Ag_2Se$-Graphene/$TiO_2$ composite was synthesized by a facile sonochemical method. The as-prepared products were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectrophotometer. During the reaction, both of the reduction of graphene oxide and loading of $Ag_2Se$ and $TiO_2$ particles were achieved. The as-prepared $Ag_2Se$-Graphene/$TiO_2$ composites possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously. Hence, in the photodegradation of rhodamine B (Rh.B), a significant enhancement in the reaction rate was observed with $Ag_2Se$-Graphene/$TiO_2$ composites, compared to the pure $TiO_2$. The high activity can be attributed to the synergetic effects of high charge mobility, and red shift in absorption edge of $Ag_2Se$-Graphene/$TiO_2$ composites.

• 한국정보통신학회논문지
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• 제7권4호
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• pp.712-718
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• 2003

진공 증착한 CdS 박막의 질소 이온 주입 효과를 X-선 회절 검사, 광 투과율, 라만 산란 특성을 통하여 조사하였다. 질소 이온 주입하지 않은 CdS 박막은 (0 0 2)면으로의 우선 방위를 가지고 성장하였다. 질소 이온 주입한 시편의 경우 metallic Cd가 형성됨을 XRD 분석 결과 알 수 있었다. 가시광 영역에서의 광투과율은 질소 이온 주입 양이 많아짐에 따라 크게 감소하였다. 또한 질소 이온 주입 양에 따라 CdS 박막의 흡수 계수는 지수 함수적으로 증가하였고, 밴드 갭은 감소하였다 CdS 박막의 라만 peak 위치는 질소 이온 주입 양에 관계없이 299 cm-1로 거의 일정하지만, peak의 FWHM은 이온 주입 양이 증가함에 따라 커졌고, peak 면적은 감소하였다.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2531-2536
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• 2011

Ethanol is a prototype molecule used in probing catalytic reactivity of oxide catalysts such as $TiO_2$. In the present study, we adsorbed ethanol on $TiO_2$(001) at room temperature (RT) and the corresponding bonding state of ethanol was systematically studied by x-ray photoemission spectroscopy (XPS) using synchrotron radiation. Especially, we compared $TiO_2$(001) surfaces prepared in ultra-high vacuum (UHV) with different surface treatments such as $Ar^+$-sputtering and oxidation with molecular $O_2$, respectively. We find that the saturation coverage of ethanol at RT varies depending on the amount of reduced surface defects (e.g., $Ti^{3+}$) which are introduced by $Ar^+$-sputtering. We also find that the oxidized $TiO_2$(001) surface has other type of surface defects (not related to Ti 3d state) which can dissociate ethanol for further reaction above 600 K. Our C 1s core level spectra indicate clearly resolved features for the two chemically distinct carbon atoms from ethanol adsorbed on $TiO_2$(001), showing the adsorption of ethanol proceeds without C-C bond dissociation. No other C 1s feature for a possible oxidized intermediate was observed up to the substrate temperature of 650 K.

• 분석과학
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• 제10권3호
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• pp.209-215
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• 1997

2차 전지의 양극(anode)으로 사용되는 Li-AGICs를 혼합가압법에 의하여 Li의 함유량에 따라 합성하였다. 이들 합성된 화합물을 X-선회절법, UV/VIS 분광학적 분석법 및 DSC 열분석법을 이용하여 특성화하였다. X-선회절분석 결과에 의하면 리튬의 함유량이 증가함에 따라 낮은 stage가 관찰되었으나, 각각의 화합물들은 혼재된 stage를 가지고 있음이 나타났다. $Li_{30wt%}$-AGIC의 경우 지배적으로 1 stage의 구조가 나타났지만 순수한 1 stage의 화합물은 얻을 수가 없었는데, 이것은 인조 흑연의 구조적 특성 때문에 예상할 수 있다. UV/VIS 분광학적 특성에 의하면 Li-AGIC의 흡수 spectra가 활성적으로 나타나지는 않았지만, $Li_{30wt%}$-AGIC의 경우 뚜렷한 $R(%)_{min}$의 형성과 함께 특징적인 흡수영역을 나타내고 있다. DSC에 의한 열역학적 결과로부터 화합물에 대하여 엔탈피의 변화량(${\Delta}H$)과 엔트로피의 변화량(${\Delta}S$)을 구하였다. 이들로부터 Li-AGIC의 발열반응과 흡열반응의 결과들은 인조 흑연 사이에 존재하던 리튬이 열에 의해 deintercalation이 일어날 때의 열적 안정성과 관련이 있음을 알 수 있다. 또한 열적 변이가 일어나는 동안 $Li_{30wt%}$-AGIC의 구조 변화에 대하여 토론하였다.

• Journal of Electrochemical Science and Technology
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• 제5권4호
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• pp.109-114
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• 2014

The $Li_3V_2(PO_4)_3$/graphene nano-particles composite was successfully synthesized by a facile sol-gel method. The addition of a graphene in $Li_3V_2(PO_4)_3(LVP)$(LVP) showed the high crystallinity and influenced the morphology of the $Li_3V_2(PO_4)_3$ particles observed in X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LVP/graphene samples were well connected, resulting in fast charge transfer. The effect of the addition graphene nano-particles on electrochemical performance of the materials was investigated. Compared with the pristine LVP, the LVP/graphene composite delivered a higher discharge capacity of $122mAh\;g^{-1}$ at 0.1 C-rate, better rate capability and cyclability in the potential range of 3.0-4.3 V. The electrochemical impedance spectra (EIS) measurement showed the improved electronic conductivity for the LVP/graphene composite, which can ensure the high specific capacity and rate capability.

• Advances in materials Research
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• 제5권3호
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• pp.181-192
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• 2016

In this work effect of high energy milling on the structural and electrical properties of $Ba(Fe_{1/2}Ta_{1/2})O_3$ (BFT) ceramic synthesized using standard solid-state reaction method were investigated. X-ray diffraction studies indicated that the unit cell structure for all the samples to be hexagonal (space group: P3m1). FTIR spectra also confirmed the formation of BFT without any new phase. The milled (10 h) BFT ceramic showed the formation of small grain sizes (<$2{\mu}m$) which is beneficial for dielectric applications in high density integrated devices. Besides, the milled (10 h) BFT ceramic sample exhibited superior dielectric properties (enhancement in ${\varepsilon}^{\prime}-value$ and reduction in $tg{\delta}-value$) compared to un-milled one. Impedance analysis indicated the negative temperature coefficient of resistance (NTCR) character. The correlated barrier hopping model (jump relaxation type) is found to successfully explain the mechanism of charge transport in present ceramic samples.

• 한국재료학회지
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• 제8권4호
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• pp.328-336
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• 1998

본 연구에서는 기지금속과의 고상이나 액상의 고용한이 거의 없는 금속-카본(carbon)계에서 고에너지 볼밀공정을 이용하여 고체 윤활 청동베어링용 Cu-C-X계 나노복합금속분말을 제조하고자 하였다. Cu-10wt.%C-5wt.%AI과 Cu-10wt.%C-5wt.%Fe의 혼합분말을 이르곤 분위기의 attritor내에서 기계적 합금화한 후 Cu-C-X의 나노복합금속분말의 미세조직 특성을 조사하였다. AI, Fe를 첨가하였을 때 10시간 이상의 MA공정에서부터 약 $10\mu\textrm{m}$이하의 미세한 Cu-C-X나노복합금속분말을 얻을 수 있었으며, MA 시간에 따른 분말의 형상과 미세구조 변화는 금속-금속계의 MA 과정과 유사하게 진행되는 것을 알 수 있었다. Cu-C-X 나노복합금속분말의 X-선 회절시험 결과, MA 시간에 따라 Cu와 C분말의 회절피크의 폭은 넓어지고 회절강도는 감소하였으며, 특히 흑연피크의 MA시간에 따른 소멸은 흑연의 낮은 원자산란계수 때문에 의한 X-선 흡수 영향으로 고찰하였다. Williamson-Hall식으로 계산된 Cu-C-X 나노복합금속분말내의 Cu의 결정립은 15시간 이상의 MA공정에서부터 약 10nm이하의 크기를 가졌으며, TEM 분석결과로는 불규칙한 형상의 약 10-30nm 크기로 복합화된 Cu결정립을 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.25-30
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• 2002

The ternary semiconducting compounds of the $A_{4}BX_{6}$(A=Cd, Zn, Hg; B=Si, Sn, Ge; X=S, Se, Te) type exhibit strong fluorescence and high photosensitivity in the visible and near infrared ranges, so these are supposed to be materials applicable to photoelectrical devices. These materials were synthesized and single crystals were first grown by Nitsche, who identified the crystal structure of the single crystals. In this paper. author describe the undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ single crystals were grown by the chemical transport reaction(CTR) method using iodine of $6mg/cm^{3}$ as a transport agent. For the crystal. growth, the temperature gradient of the CTR furnace was kep at $700^{\circ}C$ for the source aone and at $820^{\circ}C$ for the growth zone for 7-days. It was found from the analysis of x-ray diffraction that undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ compounds have a monoclinic structure. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy gaps. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]