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방전플라즈마 소결법에 의해 제조된 다공질 타이타늄 임플란트의 평가
오익현 ( Ik Hyun Oh ),손현택 ( Hyeon Taek Son ),장세훈 ( Se Hun Chang ),김형모 ( Hyung Mo Kim ),이기용 ( Ki Yong Lee ),박순섭 ( Sun Sub Park ),송호연 ( Ho Yeon Song ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.6
Porous Ti compacts were fabricated by spark plasma sintering (SPS) method and their Young`s modulus and biocompatibility were investigated in this study. Ti powders were made from commercially available pure Ti electrode (grade 2) using the plasma rotating electrode process (PREP) in an Ar atmosphere. Porous Ti compacts for biomedical applications were successfully fabricated in the porosity range from 5 to 36 vol%. Young`s modulus of porous Ti compacts having porosity from 31 to 36 vol % is almost the same as that of human cortical bone. To investigate the biocompatibility of pure Ti, fibroblast-like L-929 and osteoblast-like MG-63 cells were cultured with the presence of the extract solution from pure Ti powder and porous body. The viabilities of cells cultured with the diluted extract solutions were almost the same compared to that of the control. Also, porous Ti compacts did not induce any morphologic damage of cell.
니켈수소전지용 수산화니켈 입자의 표면처리와 전해액 첨가제 LiOH의 전기화학적 거동
김호성,오익현,Kim, Ho-Sung,Oh, Ik-Hyun 한국전기화학회 2008 한국전기화학회지 Vol.11 No.2
본 논문은 니켈수소전지의 양극 재료인 수산화니켈의 단일 입자 및 코발트 금속산화물에 의해 표면처리 된 수산화니켈 단일 입자에 대해 각각 알카리 전해액 중의 LiOH 첨가 효과를 마이크로전극 측정시스템을 사용하여 평가하였다. 전위 주사법에 의해 실험한 결과, 수산화니켈 입자에 대한 산화환원 반응과 산소발생 반응에 대한 전기화학적 거동을 보다 명확히 확인 할 수 있었다. 특히, LiOH 첨가에 의해 관찰되는 특징적인 변화는 환원전류 피크가 매우 낮고 브로드하게 반응하는 것으로서, LiOH가 수산화니켈 입자의 격정 구조에 영향을 주어 전기화학적 반응특성에 관여함을 알 수 있다. 그러나 표면 개질 하지 않는 수산화니켈 입자에 LiOH를 첨가 할 경우 용량 및 사이클 특성이 동시에 저하하는 경향을 의였다. 그러나 코발트 금속 산화물로 표면 개질 한 수산화니켈 입자의 경우, LiOH 첨가에 의해 용량 및 싸이클 특성이 향상되는 현상이 관찰 되었다. Single particle of nickel hydroxide and the surface-treated one with cobalt element were performed to review the effect of LiOH additive in alkaline electrolyte for Ni-MH batteries using microelectrode test system. As a result of cyclic voltammetry, the electrochemical behaviors such as the oxidation/reduction and oxygen evolution reaction are clearly observed for a single particle of nickel hydroxide, respectively. Furthermore, the reduction current peak of nickel hydroxide added with LiOH in electrolyte was very low and broad compared with the normal nickel hydroxide without an additive LiOH, which had a bad effect to the crystallization structure of nickel hydroxide. However, it was found that capacity and cycle properties of the nickel hydroxide treated with cobalt greatly increased by the addition of LiOH.
마이크로전극에 의한 니켈수소전지용 수산화니켈 입자의 전기화학적 거동
김호성,오익현,이종호,Kim, Ho-Sung,Oh, Ik-Hyun,Lee, Jong-Ho 한국전기화학회 2007 한국전기화학회지 Vol.10 No.2
본 논문은 마이크로전극 측정시스템을 사용하여 니켈수소전지의 전극 소재로 사용되고 있는 수산화니켈의 단일 입자에 대해 전기화학적 평가를 수행 하였다. 즉 Carbon fiber 마이크로전극을 수산화니켈 입자 한개 위에 전기적인 접촉을 이루도록 조정하고 전기화학적 평가를 수행하였다. Cyclic Voltammetry 실험 결과 수산화니켈의 산화 환원 반응과 산소 발생 반응(OER)이 명확하게 분리 되고 있음을 확인하였으며, 전위주사속도를 증가 시킬 경우 환원 전하량은 주사 속도에 의존하지 않고 거의 일정한 수치를 보여 주고 있으나, 산화 전하량은 환원 전하량 보다 크고 주사속도 구간에서 부반응인 산소발생이 증가하고 있음을 확인했다. 그리고 Calvanostat에 의한 정전류 충방전 실험의 결과 수산화니켈 단일 입자의 방전용량은 이론용량 289 mAh/g에 근접한 수치(약 250 mAh/g)를 보여 주었으며 또한 Potential Step에 의해 단일 입자내의 수소이온 확산계수($D_{app}=3{\sim}4{\times}10^{-9}\;cm^2/s$)가 얻어졌다. Electrochemical studies were performed for a single particle of nickel hydroxide for the cathode of Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and electrochemical experiments were performed. As a result of cyclic voltammetry, the oxidation/reduction and oxygen evolution reaction (OER) are clearly separated for a single particle. The total cathodic charge (Qred) is practically constant for the scan rate investigated, indicating that the whole particle has reacted. The total anodic charge(Qox) was larger than that of reduction reaction, and the magnitude of oxygen evolution taking place as a side reaction was enhanced at lower scan rates. As a result of galvanostatic charge and discharge measurement, the discharge capacity of single particle was found to be 250 mAh/g, value being very close to the theoretical capacity (289 mAh/g). The apparent proton diffusion coefficient(Dapp) using potential step method inside the nickel hydroxide was found to range within $3{\sim}4{\times}10^{-9}\;cm^2/s$.
펄스전류활성소결법을 이용한 스퍼터링 타겟용 Cu-Mn 소결체 제조 및 특성평가
장준호,오익현,임재원,박현국,Jang, Jun-Ho,Oh, Ik-Hyun,Lim, Jae-Won,Park, Hyun-Kuk 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.1
Cu-Mn compacts are fabricated by the pulsed current activated sintering method (PCAS) for sputtering target application. For fabricating the compacts, optimized sintering conditions such as the temperature, pulse ratio, pressure, and heating rate are controlled during the sintering process. The final sintering temperature and heating rate required to fabricate the target materials having high density are $700^{\circ}C$ and $80^{\circ}C/min$, respectively. The heating directly progresses up to $700^{\circ}C$ with a 3 min holding time. The sputtering target materials having high relative density of 100% are fabricated by employing a uniaxial pressure of 60 MPa and a sintering temperature of $700^{\circ}C$ without any significant change in the grain size. Also, the shrinkage displacement of the Cu-Mn target materials considerably increases with an increase in the pressure at sintering temperatures up to $700^{\circ}C$.
김주훈,오익현,이정한,홍성길,박현국,Kim, Ju-Hun,Oh, Ik-Hyun,Lee, Jeong-Han,Hong, Sung-Kil,Park, Hyun-Kuk 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2
Tungsten carbide (WC) hard materials are used in various industries and possess a superior hardness compared to other hard materials. They have particularly high melting points, high strength, and abrasion resistance. Accordingly, tungsten carbide hard materials are used for wear-resistant tools, cutting tools, machining tools, and other tooling materials. In this study, the WC-5wt.%Co, Fe, Ni hard materials are densified using the horizontal ball milled WC-Co, WC-Fe, and WC-Ni powders by a spark plasma sintering process. The WC-5Co, WC-5Fe, and WC-5Ni hard materials are almost completely densified with a relative density of up to 99.6% after simultaneous application of a pressure of 60 MPa and an electric current for about 15 min without any significant change in the grain size. The average grain size of WC-5Co, WC-5Fe, and WC-5Ni that was produced through SPS was about 0.421, 0.779, and $0.429{\mu}m$, respectively. The hardness and fracture toughness of the dense WC-5Co, WC-5Fe, WC-5Ni hard materials were also investigated.
저온 분사 공정으로 제조된 Ti 코팅층의 미세조직 및 물성에 미치는 송급 가스의 영향
이명주,김형준,오익현,이기안,Lee, Myeong-Ju,Kim, Hyung-Jun,Oh, Ik-Hyun,Lee, Kee-Ahn 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.1
The effect of carrier gases (He, $N_2$) on the properties of Ti coating layers were investigated to manufacture high-density Ti coating layers. Cold spray coating layers manufactured using He gas had denser and more homogenous structures than those using $N_2$ gas. The He gas coating layers showed porosity value of 0.02% and hardness value of Hv 229.1, indicating more excellent properties than the porosity and hardness of $N_2$ gas coating layers. Bond strengths were examined, and coating layers manufactured using He recorded a value of 74.3 MPa; those manufactured using $N_2$ gas had a value of 64.6 MPa. The aforementioned results were associated with the fact that, when coating layers were manufactured using He gas, the powder could be easily deposited because of its high particle impact velocity. When Ti coating layers were manufactured by the cold spray process, He carrier gas was more suitable than $N_2$ gas for manufacturing excellent coating layers.
대식세포가 β-tricalcium Phosphate 뼈이식제의 생분해에 미치는 영향
김영희,변인선,오익현,민영기,양훈모,이병택,송호연,Kim, Young-Hee,Jyoti, Anirban,Byun, In-Sun,Oh, Ik-Hyun,Min, Young-Ki,Yang, Hun-Mo,Lee, Byong-Taek,Song, Ho-Yeon 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.10
Various calcium phosphate bioceramics are distinguished by their excellent biocompatibility and osteoconductivity. Especially, the exceptional biodegradability of $\beta$-TCP makes it a bone graft substitute of choice in many clinical applications. The activation of osteoclasts, differentiated from macrophage precursor cells, trigger a cell-mediated resorption mechanism that renders $\beta$-TCP biodegradable. Based on this evidence, we studied the biodegradation process of granular-type $\beta$-TCP bone graft substitute through in vitro and in vivo studies. Raw 264.7 cells treated with RANKL and M-CSF differentiated into osteoclasts with macrophage-like properties, as observed with TRAP stain. These osteoclasts were cultured with $\beta$-TCP nano powders synthesized by microwave-assisted process. We confirmed the phagocytosis of osteoclasts by observing $\beta$-TCP particles in their phagosomes via electron microscopy. No damage to the osteoclasts during phagocytosis was observed, nor did the $\beta$-TCP powders show any sign of cytotoxicity. We also observed the histological changes in subcutaneous tissues of rats implanted with granule-type $\beta$-TCP synthesized by fibrous monolithic process. The $\beta$-TCP bone graft substitute was well surrounded with fibrous tissue, and 4 months after implantation, 60% of its mass had been biodegraded. Also, histological findings via H&E stain showed a higher level of infiltration of lymphocytes as well as macrophages around the granule-type $\beta$-TCP. From the results, we have concluded that macrophages play an important role in the biodegradation process of $\beta$-TCP bone graft substitutes.