• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.1
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• pp.27-34
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• 2001

To investigate the processes governing the distribution of elements in the tidal flat, thirty-eight sediment samples collected from the Saemangeum tidal flat of the Korean west coast were analyzed for their contents of major (Al, Fe, Mg, Ca, Na, K, Ti) and trace (P, Mn, Ba, Sr, V, Cr, Co, Cu, Ni, Zn, Pb) elements. Most elements showed generally lower contents compared to data published for other tidal flats of Korea, and the effect of anthropogenic input could not be recognized in the sediments. The relative abundance and distribution of most of the elements varied significantly with the grain size of sediments. High contents of Al, Fe, Mg, Ti, P, Mn, V, Co, Cr, Cu, Ni and Zn were found in the finer sediments in the upper tidal flat of the study area, suggesting that tidal sedimentation processes play an important role in controlling the distribution of these elements. However, sediment grain size does not impose any significant effect on the abundance and distribution of Ca, Na, K, Ba, Sr and Pb. It appears that the clastic mineralogy in the coarse-grained fractions is the dominant factor determining the distribution of these elements in the study area.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.140-140
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• 2012

최근에 고체산화물 연료전지(SOFC) 연료극 조건에서 우수한 상 안정성, 높은 혼합 전자/이온 전도도 및 황/탄소 저항성 때문에 yttrium-doped strontium titanium oxide (Y-doped SrTiO3)가 대체 연료극 재료로 주목을 받아 왔다. 그러나 Y-doped SrTiO3는 연료 산화에 대해서 기존의 Ni 계열 연료극보다 낮은 전기화학적 활성을 보이는 단점이 있다. 따라서, 효율적인 Y-doped SrTiO3 계열의 연료극 재료를 개발하기 위해서는 Y-doped SrTiO3의 연료극 특성 및 반응성의 이해가 필수적이다. 본 발표에서는 SOFC 연료극에서 수소 산화 반응성을 결정함에 있어 표면 산소 vacancy 형성 에너지의 역할에 대한 spin-polarized DFT (density functional theory) 결과를 발표할 예정이다. 표면 산소 vacancy 형성 에너지는 수소 산화 반응[H2+O (surface) ${\rightarrow}$ OH+OH ${\rightarrow}$ H2O+O (vacancy)]과 밀접한 관계가 있다는 것을 확인하였다. 또한 Y-doped SrTiO3의 표면을 3d-전이금속을(Sc, V, Cr, Fe, Co, Mn, Ni, Cu) 도핑함으로써 표면 산소 vacancy 형성 에너지를 제어할 수 있다는 것을 보였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.207-207
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• 2003

최근 광촉매 재료로 각광받고 있는 TiO$_2$는 band gap 에너지가 3.0-3.2eV로 자외선 영역과 일부 가시광선 영역에서 활성을 갖는 것으로 알려져 있다. 따라서 용액 중에 결정화 및 안정화 되어있는 TiO$_2$의 band gap 에너지를 낮춘다면 가시광 영역의 광반응을 얻을 수 있다. 이에 본 연구는 G. Sato등이 제안한 방법으로 TiO$_2$ sol을 제조할 때 band gap 에너지를 낮추고자 천이 금속원소를 첨가하여 복합 및 담지된 TiO$_2$계 복합 sol을 합성하고자 하였다 출발원료는 TiC1$_4$를 가수분해하여 제조한 TiOCl$_2$에 천이금속원소인 V, Cr, Fe, Ni, Nb 등의 chloride 화합물을 첨가하여 중화 및 세척과정을 거친 후, 과산화수소수에 용해하여 전구체 용액인 titania peroxo용액을 제조하였다 제조된 전구체 용액은 온도와 시간을 변수로 각각 열처리하여 TiO$_2$계 복합 sol을 합성하였다. 제조된 시편은 X-선 회절 분석, 투과전자현미경, particle size analyzer, ζ-potential analyzer 및 UV-VIS Spectrometer 통을 이용하여 천이금속 첨가에 따른 TiO$_2$계 복합 sol의 형성과정과 특성변화를 관찰하였다.

• Journal of Korea Foundry Society
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• v.11 no.6
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• pp.491-497
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• 1991

Vanadium은 비중이 6.09로써 비교적 무거운 금속에 속하나 Al을 30wt% 이내로 첨가하여 $Ni_3Al$ 및 TiAl와 유사한 비강도가 크며 내열성을 지니는 V-Al합금을 얻을 가능성을 지니고 있다. 본 연구에서는 V-Al합금에 Si, Y, Ti, B등 제3원소를 첨가함에 따르는 미세 응고조직의 거동과 기계적 성질을 조사하였다. 알곤 분위기에서 제조된 V-30%Al합금은 상온에서 고용체와 취성이 큰 금속간 화합물인 $VAl_3$등 2상으로 존재하므로 용체화 처리 과정이 요구되며 24시간 이상 장시간 열처리에 의하여 단일 고용상을 이룰 수 있었다. 규소의 첨가는 금속간 화합물의 형성과 아울러 합금의 경도를 크게 증가시키는 경향을 나타내며 B을 0.3%정도가지 첨가할 때 경도가 낮아지는 현상이 관찰되었다. �c칭된 V-30%Al 합금은 입계면을 따라 decohesive rupture 현상을 나타내며 입자간 파괴 현상도 일부 관찰되었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.834-838
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• 2002

In this paper, we have fabricated 4H-SiC schottky diodes utilizing a metal-oxide overlap structure for electric filed termination. The barrier height and Ideality factor were measured by current-voltage, capacitance-voltage characteristics. Schottky barrier height(SBH) were 1.41ev for Ni and 1.35eV for Pt, 1.52eV for Pt/Ti at room temperature and Pt/Ti Schottky diode exhibited Ideality factor was 1.06 to 1.4 in the range of $25^{\circ}C{\sim}200^{\circ}C$. To improve the reverse bias characteristics, an edge termination technique is employed for Pt/Ti/4H-SiC Schottky rectifiers and the device show excellent characteristics with higher blocking voltage up to 780V compared with unterminated devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.222-227
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• 2006

RAINBOW(Reduced And Internally Biased Oxide Wafers) are a new class of high-displacement, piezoelectric actuator produced by selectively removing oxygen from one surface of ceramic using a high-temperature chemical reduction process. In this paper, RAINBOW actuator materials of $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_{x}Ti_{1-x})O_3$ ceramics were prepared. Its dielectric and piezoelectric properties were investigated in the vicinity of MPB. The piezoelectric properties showed the maximum value of ${\epsilon}r$ = 4871, $d_{33}$ = 610 ($10^{-12}$ m/V), $d_{31}$ = -299 ($10^{-12}$ m/V), $k_{33}$ = $71\%$, Qm = 70, in $0.4Pb(Ni_{1/3}Nb_{2/3})O_{3}-0.6Pb(Zr_{405}Ti_{595})O_3$ composition sintered at $1250^{\circ}C$. The strain - electric field characteristics of RAINBOW actuator were significantly improved comparison with the conventional bulk actuator. The prepared RAINBOW actuator showed about $390\;{\mu}m/100\;V$ displacement.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1574-1576
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• 2003

Carbon nanotubes (CNTs) were grown on the TiN-coated silicon substrate with different thickness of Ni and Co catalysts layer at $600^{\circ}C$ using inductively coupled plasma-chemical vapor deposition (ICP-CVD). The Ni and Co catalysts were formed using the RF magnetron sputtering system with various deposition times. It was found that the growth of CNTs was strongly influenced by the surface morphology of Ni and Co catalysts. With increasing deposition time, the thickness of catalysts increased and the grain boundary size of catalysts increased. The surface morphology of catalysts and CNTs were elucidated by SEM. The Raman spectrum further confirmed the graphitic structure of the CNTs. The turn-on field of CNTs grown on Ni and Co catalysts was about 2.7V/pm and 1.9V/pm respectively. Field emission current density of CNTs grown on Ni and Co catalysts was measured as $11.67mA/cm^2$ at $5.5V/{\mu}m$ and $1.5mA/cm^2$ at $5.5V/{\mu}m$ respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.8-8
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• 2002

TiC core/(Ti,Mo)C rim structure in TiC-$Mo_2C$-Ni base cermet which is generally prepared by sintering below 145$0^{\circ}C$ had been believed to be generated by the solid diffusion of Mo atoms 1 into TiC grains (D. Moskowitz and M.Humenik, 1r.:1966). Afterward, it was clarified that the c core/rim structure is generated by solution/re-precipitation mechanism : (1) $Mo_2C$ grains and s small TiC grains dissolve into the Ni liquid, (2) the dissolved Mo, Ti and C atoms migrate to the s surface of TiC coarse grains, (3) the Mo, Ti and C precipitate on the surface of TiC coarse g grains and form (Ti,Mo)C solid solution rim, and (4) the Ostwald ripening (grain growth by s solution/re-precipitation mechanism) of TiC-core/(Ti,Mo)-rim grains continues, and thus the w width of (Ti,Mo)C rim (at the same time, the grain size) increases with sintering time, etc. ( (H.Suzuki, K.Hayashi and O.Terada: 1973). The TiC-core was found not to disappear even by s sintering at 190$0^{\circ}C$ (ibid.: 1974) Recently, FeSi core/$Fe_2Si_5$-rim structure in Fe-66.7at%Si thermoelectric aIloy was found to also h hardly shrink and disappear by long heating at an appropriate temperature (1999: M.Tajima and K K.hayashD. Then, the authors considered its cause, and clarified experimentaIly that the disappearance of FeSi-core/$Fe_2Ski_5$-rim structure could be attributed to the exhaustion of diffusion-contributable vacancies in core/rim structure (N.Taniguchi and K.Hayashi:2001). At p present, the authors and my coworker are investigating whether the non-disappearance of TiC c core can be explained also from the new hypothesis "Exhaustion of diffusion-contributable v vacancies in corelrim structure".ure".uot;.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.157-163
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• 2004

Nitrogen ion implantation and ion plating techniques were applied for improvement of the wear resistance of metallic implant materials. In this work, the wear dissolution behaviour of a nitrogen ion implanted super stainless steel (S.S.S, 22Cr-20Ni-6Mo-0.25N) was compared with those of S.S.S, 316L SS and TiN coated 316L SS. The amounts of Cr and Ni ions worn-out from the specimens were Investigated using an electrothermal atomic absorption spectrometry. Furthermore, the Ti(Grade 2) disks were coated with TiN, ZrN and TiCN by use of low temperature arc vapor deposition and the wear resistance of the coating layers was compared with that of titanium. The chemical compositions of the nitrogen ion implanted and nitride coated layers were examined with a scanting auger electron spectroscopy. It wat observed that the metal ions released from the nitrogen ion implanted S.S.S surface were significantly reduced. From the results obtained, it was shown that the nitrogen ion implanted zone obtained with 100 KeV ion energy was easily removed within 200,000 revolutions from a wear dissolution testing under a similar load condition when applied to artificial hip joint. The remarkable improvement in wear resistance weir confirmed by the nitrides coated Ti materials and the wear properties differ greatly according to the chemical composition of the coating layers. for specimens with the same coating thickness of about 3$\mu\textrm{m}$, TiCN coated Ti showed the highest wear resistance. However, after removing the coating layers, the wear rates of all nitrides coated Ti reverted to their normal rates of below 10,000 revolutions from Ti-disk-on-disk wear testing under the same load condition. From the results obtained, it is suggested that the insufficient depth of the 100 Kel N$\^$＋/ ion implanted zone and of the nitrides coated layers of 3$\mu\textrm{m}$ are subject to restriction when used as frictional parts of load bearing implants.

• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1301-1307
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• 1995

Pitting corrosion of TiN film deposited on Inconel 600 by plasma assisted chemical vapor deposition (PACVD) was investigated. Cyclic potentiodynamic polarization (CPP) tests were conducted in order to determine the pit nucleation potentials, Enp, of the TiN-deposited sample and the bare Inconel 600 in deaerated NaCl solution at 25, 135 and 20$0^{\circ}C$. The effects of the TiN film thickness, the solution temperature and the Cl- concentration on Enp were studied. Enp of the TiN-deposited sample which had the film thickness above 1${\mu}{\textrm}{m}$ were higher than those of the bare Inconel 600 by 300~600mV at all the solution temperatures, implying the pitting resistance improvement of the TiN film. The morphologies of the pits generated after immersion test were examined with a scaning electron microscopy. The higher was the solution temperature, the more corrosion products, mainly composed of Cr and Ni oxides, were formed.