• Resources Recycling
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• v.24 no.1
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• pp.21-27
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• 2015

The present study describes the process of producing low oxygen content alloy powder from Ti-6Al-4V and Ti-8Al-1Mo-1V (AMS 4972) alloy scraps using hydrogenation-dehydrogenation (HDH) and deoxidation in solid state (DOSS) processes. Each prepared powder was deoxidized with Ca contact and non-contact method to compare the deoxidation capability. It is known that the non-contact deoxidation method, using Ca vapor above the melting temperature $T_m$ of Ca, has greater deoxidation capability. However, Oxygen contents in Ti-6Al-4V and Ti-8Al-1Mo-1V powder after non-contact deoxidation method were higher than those after contact deoxidation method. Therefore, we investigate the effect of Al - the richest alloy element in theses Ti based metals - on the deoxidation processes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.266-267
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• 2011

질화갈륨(GaN)은 높은 전자이동도 및 높은 항복전계를 가지며 낮은 온저항으로 인하여 에너지효율이 우수하기 때문에 고출력 전력소자 분야에서 많은 관심을 받고 있다. GaN을 이용한 고출력 전력소자의 경우 상용화 수준에 근접할 만한 기술적 진보가 있었으나, 페르미 레벨 고정(Fermi-level pinning) 현상, 소자의 누설전류 등 아직 해결되어야 할 문제를 갖고 있다. 본 연구에서는 실리콘 기판 위에 성장된 GaN 에피탁시를 활용한 고출력 전력소자의 누설전류를 억제시키기 위해 오믹 접합 중 Au의 상호확산을 억제하는 중간층 금속(Mo or Ni)을 변화시켰으며 오믹 열처리 온도에 따른 특성을 비교 연구하였다. $Cl_2$와 $BCl_3$를 이용하여 0.6 ${\mu}m$ 깊이의 메사 구조가 활성영역을 형성하였고, Si 도핑된 n-GaN 위에 Ti/Al/Mo/Au (20/100/25/200 nm) 와 Ti/Al/Ni/Au (20/100/25/200 nm) 오믹 접합을 각각 설계, 제작하였다. 오믹 열처리시의 GaN 표면오염을 방지하기 위해 $SiO_2$ 희생층을 증착하였다. 오믹 접합 형성을 위해 각 750$^{\circ}C$, 800$^{\circ}C$, 850$^{\circ}C$에서 30초간 열처리를 진행 하였으며, 이후 6 : 1 BOE 용액으로 $SiO_2$ 희생층을 제거하였다. 750, 800, 850$^{\circ}C$에서 Ti/Al/Mo/Au 구조의 오믹 접합 저항은 각 2.56, 2.34, 2.22 ${\Omega}$-mm 이었으며, Ti/Al/Ni/Au 구조의 오믹 접합 저항은 각 43.72, 2.64, 1.86 ${\Omega}$-mm이었다. Isolation 누설전류를 측정하기 위해서 두 개의 오믹 접합 사이에 메사 구조가 있는 테스트 구조를 제안하였다. Isolation 누설전류는 Ti/Al/Mo/Au 구조에서 두 오믹 접합 사이의 거리가 25 ${\mu}m$이고 100 V일 때 750, 800, 850 $^{\circ}C$의 열처리 온도에서 각 1.25 nA/${\mu}m$, 2.48 nA/${\mu}m$, 8.76 nA/${\mu}m$이었으며, Ti/Al/Ni/Au 구조에서는 각 1.58 nA/${\mu}m$, 2.13 nA/${\mu}m$, 96.36 nA/${\mu}m$이었다. 열처리 온도가 증가하며 오믹 접합 저항은 감소하였으나 isolation 누설전류는 증가하였다. 750$^{\circ}C$ 열처리에서 오믹 접합 저항은Ti/Al/Mo/Au 구조가 Ti/Al/Ni/Au 구조보다 약 17배 우수하였고, 850$^{\circ}C$ 고온의 열처리 경우 Ti/Al/Mo/Au 구조의 isolation 누설전류는 8.76 nA/${\mu}m$로 Ti/Al/Ni/Au의 누설전류 96.36 nA/${\mu}m$보다 약 11배 우수하였다. Ti/Al/Mo/Au가 Ti/Al/Ni/Au 보다 오믹 접합 저항과 isolation 누설전류 측면에서 전력용 GaN 소자에 적합함을 확인하였다.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.279-284
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• 2017

Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.181-189
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• 2002

A series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22, and 0.30) alloys are prepared and their oystal structure and P-C-T curves are examined. The electrochemical properties of these allqys such as activation conditions, discharge capacity, cycling performance are also investigated. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hot-charging treatment. The best activation conditions were the current density 120 mA/g and the hot-charging time 12h at $80^{\circ}C$ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacily just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 mAh/g at the current density 120 mA/g. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Fe_{0.15}$ is a good composition with a medium quantity of discharge capacities and a good cycling performance. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. Another series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}M_{0.15}$ (M = Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M = Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M = Al and Cu. They are 212 and 170 mAh/g, respectivety, at the current density 120mA/g. The $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Co_{0.15}$ alloy is the best one with a relatively large discharge capacity and a good cycling performance.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.679-684
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• 1997

The major constituents in spent FCC catalysts are Si, Al, Fe, Ti, alkali metals and some others. The spent catalyst is also composed small amounts of rare metals such as Ce, Nd, Ni and V. The selective adsorption and concentration of Ce and Nd from the leaching solution of spent FCC catalysts with sulfuric acid($0.25mol/dm^3$) were carried out by the column method with a chelate resin having a functional group of aminophosphoric acid type. Ce and Nd were separated from eluate liquor containing Al, Nd and V by the precipitation process with oxalic acid. Vanadium is purified from chloride ion coexistance by solvent extraction, employing tri-n-octyl phosphine oxide as extractant with Al in the raffinate solution. Rare metals with the purity of 99 percent were obtained from the spent FCC catalyst.

• Journal of Powder Materials
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• v.20 no.5
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• pp.323-331
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• 2013

In this paper, two kinds of advanced powder processing techniques Metal Injection Molding (MIM) and Direct Laser Forming (DLF) are introduced to fabricate complex shaped Ti alloy parts which are widely used for medical and aerospace applications. The MIM process is used to strengthen Ti-6Al-4V alloy compacts by addition of fine Mo, Fe or Cr powders. Enhanced tensile strength of 1030 MPa with 15.1% elongation was obtained by an addition of 4 mass%Cr because of the microstructural modification and also the solution strengthening in beta phase. However, their fatigue strength was lower compared to wrought materials, but was improved by HIP. Subsequently, the effect of feeding layer height (FLH) on the characteristics of the DLF compacts was investigated. In the case of 100 ${\mu}m$ FLH, surface roughness was improved and nearly full density (99.8%) was obtained. Also, tensile strength of 1080 MPa was obtained, which is higher than the ASTM value.

• Economic and Environmental Geology
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• v.30 no.3
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• pp.209-222
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• 1997

The Hoenam area, up the Taecheong lake, composed mainly of low grade coal-bearing metapelites within the Ogcheon Supergroup. These coal formations are developed discontinuously several hundred meters and swelling from 10 to 300 cm along the host metapelites. Although the formations have been mined for coal, but already mined out, and the formations were higher content (mean value of 42 samples) of environmental toxic elements as As (13 ppm). Ba (1.81 wt. %), Cd (2 ppm), Cr (188 ppm), Cu (87 ppm), Mo (214 ppm), Pb (25 ppm), Sb (3 ppm), Se (12 ppm), U (55 ppm), V (2124 ppm) and Zn (234 ppm) than the host metapelites and the NASC. The Al, Ti, Mg, K and Na contents in stream sediments derived from the Hando and Bugook mine area were highly concentrations than the samples from the Samseongjeil mine area. The mean value (wt. %) of Fe (10.07), Mn (0.15), Ca (0.84), P (0.18) and Ba (0.77) influenced by the Samseongjeil mine were higher than the other mine drainage sediments. The mean content (ppm) of environmental toxic elements in drainage sediments from the Samseongjeil mine were taken As (2083), Cu (447), Mo (202), Ni (720), Pb (42), U (250), V (1070) and Zn (2632), which are extremely high concentrations against NASC and EPA. Characteristics of elemental behavior and dispersion of the all toxic elements are the same as increased with increasing U, V, and Cu. Rare earth elements in the sediments are enriched with LREE (La, Ce and Nd) from the drainage on strong concentration of toxic elements. The pH of stream water is neutral, but pH of the sediments ranged from 4.92 to 6.93 (mean 6.22), those are slightly acid in the Hando mine area. Major elements in the host rocks at the Hoenam area are mostly depleted especially Ca, excepting Ti and Ba, normalized with NASC. The sediments were highly enriched of Ti, Fe, Mg, Mn and Ba, but depleted of Al, K, Ca, Na and P on the basis of host rocks and NASC. Minor and environmental toxic elements in the host rocks were strongly enriched all elements (As, Cd, Mo, Se, D, V and Zn), excepting Co, Ni and Sr. Enrichment index (mean value) about toxic elements (As, Cr, Cu, Fe, Ni, Pb and Zn) of the sediments in this area have taken 41.35 (Hando mine drainage; 2.73, Samseongjeil mine drainage; 113.14 and Bugook mine drainage; 8.19), those are seriously contaminated by environmental toxic elements.

• Korean Journal of Plant Resources
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• v.3 no.2
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• pp.107-114
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• 1990

In view of the results to have measured metallic elements which is included in 45 sorts of herb medicines and surveyed their distribution, 8 kinds ofmetals including Co, Ge, Ga, TL, Cd, As, 8i, Pb, are never or little includedin almost herb medicines . Other twenty-five sorts of elements (Mo, Sc, Be, V,Ni, Sn, Se, Ba, Cr, Sb, Si, Ti, B, Li, Mg, Ca, Cr, Mn, Fe, Cu, Zn, p, Al, Na,K) are more or Less included in all herb Bedicines ana Na, Ca, p and K aremetals that are included in Large quentities in comrarison with others . Patri-uiae Radix Contains 7 kinds of metal lic elements more than other herb medicinesdoes .

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.211-212
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• 2010

GaN 기반의 상부발광형 LED는 동작되는 동안 생기는 전기적 단락, 그리고 칩 위의 p-형 전극과 n-형 전극 사이에 생기는 누설전류 및 신뢰성 확보를 위하여 칩 표면에 passivation 층을 형성하게 된다. SiO2, Si3N4와 같은 passivation layers는 일반적으로 PECVD (Plasma Enhanced Chemical Vapor Deposition)공정을 이용한다, 하지만 이는 공정 특성상 plasma로 인한 damage가 유발되기 때문에 표면 누설 전류가 증가 한다. 이로 인해 forward voltage와 reverse leakage current의 특성이 저하된다. 본 실험에서는 원자층 단위의 박막 증착으로 인해 PECVD보다 단차 피복성이 매우 우수한 PEALD(Plasma Enhanced Atomic Layer Deposition)공정을 이용하여 Al2O3 passivation layer를 증착한 후, 표면 누설전류와 빛의 출력 특성에 대해서 조사해 보았다. PSS (patterned sapphire substrate) 위에 성장된 LED 에피구조를 사용하였고, TCP(Trancformer Copled Plasma)장비를 사용하여 에칭 공정을 진행하였다. 이때 투명전극을 증착하기 위해 e-beam evaporator를 사용하여 Ni/Au를 각각 $50\;{\AA}$씩 증착한 후 오믹 특성을 향상시키기 위하여 $500^{\circ}C$에서 열처리를 해주었다. 그리고 Ti/Au($300/4000{\AA}$) 메탈을 사용하여 p-전극과 n-전극을 형성하였다. Passivation을 하지 않은 경우에는 reverse leakage current가 -5V 에서 $-1.9{\times}10-8$ A 로 측정되었고, SiO2와 Si3N4을 passivation으로 이용한 경우에는 각각 $8.7{\times}10-9$과 $-2.2{\times}10-9$로 측정되었다. Fig. 1 에서 보면 알 수 있듯이 5 nm의 Al2O3 film을 passivation layer로 이용할 경우 passivation을 하지 않은 경우를 제외한 다른 passivation 경우보다 reverse leakage current가 약 2 order ($-3.46{\times}10-11$ A) 정도 낮게 측정되었다. 그 이유는 CVD 공정보다 짧은 ALD의 공정시간과 더 낮은 RF Power로 인해 plasma damage를 덜 입게 되어 나타난 것으로 생각된다. Fig. 2 에서는 Al2O3로 passivation을 한 소자의 forward voltage가 SiO2와 Si3N4로 passivation을 한 소자보다 각각 0.07 V와 0.25 V씩 낮아지는 것을 확인할 수 있었다. 또한 Fig. 3 에서는 Al2O3로 passivation을 한 소자의 output power가 SiO2와 Si3N4로 passivation을 한 소자보다 각각 2.7%와 24.6%씩 증가한 것을 볼 수 있다. Output power가 증가된 원인으로는 향상된 forward voltage 및 reverse에서의 leakage 특성과 공기보다 높은 Al2O3의 굴절률이 광출력 효율을 증가시켰기 때문인 것으로 판단된다.

• Economic and Environmental Geology
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• v.22 no.1
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• pp.35-63
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• 1989

Geochemical characteristics of the Guryongsan (Ogcheon) uraniferous black slate show that this is an analogue to the conventional Chattanooga and Alum shales in occurrences. Whereas, its highest enrichment ratio in metals including uranium, among others, is explained by the cyclic sedimentation of the black muds and quartz-rich silts, and the uniform depositional condition with some what higher pH condition compared to the conditions of the known occurrences. The cyclic sedimentation, caused by the periodic open and close of the silled basin, has brought about the flush-out) of the uranium depleted water and the recharge with the new metal-rich sea water, which consequently contributed to the high concentration of metals in mud. The metal-rich marine black muds, which mostly occur in the early to middle Palaeozoic times, is attributed by the geologic conditions which related to the atmospheric oxygen contents, and these are scarcely met in the late Precambrian and/or with the onset of Palaeozoic era in the geologic evolution of the earth.