직접 메탄올 연료전지를 이용한 휴머노이드 로봇의 전원시스템 개발

조한익(Joh, Han-Ik),하태정(Ha, Tae-Jung),조재형(Cho, Jae-Hyung),김종호(Kim, Jong-Ho),채승훈(Chae, Seung-Hoon),황상엽(Whang, Sang-Youp),문상흡(Moon, Sang-Heup),하흥용(Ha, Heung-Yong),조백규(Cho, Baek-Kyu),오준호(Oh, Jun-Ho) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11

전극 전해질 복합체가 하나로 구성된 단위전지는 전기출력이 낮아 원하는 전기출력을 얻기 위하여 단위전지를 여러 장 직렬로 쌓아 스택을 구성하여야 한다. 본 연구에서는 400W급 직접메탄을 연료전지 스택을 제조하여, 운전 조건의 최적화를 위한 실험을 수행하였고, 한국형 휴머노이드 로봇인 Hubo에 적용하여 그 동특성을 평가하였다. 0.8M 메탄을 용액은 260 ml/min의 유량을, 공기는 42LPM을 스택에 주입하여 400W의 성능을 나타내었다. 연료전지 스택의 온도와 전압의 편차는 작았으며 정상 운전시스템의 온도는 약 70?C를 유지하였다. 로봇의 필요 전력이 높을 경우, 배터리와 연료전지가 동시에 부하 변동에 대응하였다 방전된 배터리는 로봇의 필요 전력이 낮아질 경우, 충전되어 이후의 방전 상황에 대비하였다. 연료전지 시스템 적용 결과 로봇의 성공적인 운전을 확인할 수 있었다.

단섬유 인장시험을 이용한 상용 탄소섬유의 기계적 물성

조한익 ( Han Ik Joh ),송해경 ( Hae Kyung Song ),김기영 ( Ki Young Kim ),구본철 ( Bon Cheol Ku1 ),강필현 ( Phil Hyun Kang ),이성호 ( Sung Ho Lee ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.12

Abstract: In this study, mechanical properties of commercial carbon fibers were evaluated using a single filament tensile test with various fiber gauge lengths. Tensile strength increased significantly with a decreasing length of the test specimens possibly due to small defect sites. The compliance method provided more accurate moduli of the carbon fibers, removing system errors during the single filament tensile test. The Weibull modulus revealed that shorter specimens had an inhomogeneous defect distribution, leading to a higher tensile strength and its standard deviation. X-ray diffractograms of carbon fibers showed a similar crystallinity and orientation in spite of significant differences in the fiber modulus and strength, indicating that crystalline structure of the commercial carbon fibers used in the study was not attributable to the difference in their tensile properties.

탄소섬유 전구체를 이용한 투명 전극 및 고전도성 도선 구현 연구

조한익(Han-Ik Joh) 한국고분자학회 2020 한국고분자학회 학술대회 연구논문 초록집 Vol.45 No.2

Effect of Fe content on nonprecious cathodic catalysts derived from a metal–organic framework for direct ammonia fuel cells

Han‑Wool Jang,Seon Yeong Lee,Jong Yoon Lee,Han‑Ik Joh 한국탄소학회 2023 Carbon Letters Vol.33 No.1

Ammonia is considered a promising hydrogen carrier due to its high hydrogen density and liquefaction temperature. Considering that the energy efficiency generally decreases as chemical conversion is repeated, it is more efficient to directly use ammonia as a fuel for fuel cells. However, catalysts in direct ammonia fuel cells have the critical issues of sluggish ammonia oxidation reaction (AOR) rate and poisoning of reaction intermediates. In particular, the use of precious metal as cathodic catalysts has been limited due to ammonia crossover and poisoning. In this study, we introduce Fe-based single-atom catalysts with selective activity for the oxygen reduction reaction (ORR) even in the presence of ammonia. As the Fe content increased, the single-atom structure of the catalysts changed into Fe nanoparticles or carbides. Among our Fe–N–C catalysts, FeNC-50 with a Fe loading amount of 0.34 wt% showed the highest ORR performance regardless of the ammonia concentration. In particular, the difference in activity between the catalysts increased as the concentration increased. The FeNC-50 catalyst showed remarkable stability after 1000 cycles. Therefore, we believe that single-atom dispersion is an important factor in the development of stable non-precious catalysts with high activity and inactivity for the ORR and AOR, respectively.

Replacement effect of fresh electrolyte on the accelerated deactivation test and recovery process of Pt/C catalysts in a half-cell system

Kim Han Young,Im Dae Soon,Son U.-Hyeok,Lee Hae Ri,Joh Han-Ik 한국탄소학회 2022 Carbon Letters Vol.32 No.1

The poor durability issue of polymer electrolyte membrane fuel cells is a major concern in terms of their commercialization. To understand the degradation mechanism of the catalysts, an accelerated durability test (ADT) was conducted according to the protocol established by internationally accredited organizations. However, reversible and irreversible factors contributing to the loss of activity have not yet been practically segregated because of the limitations of a batch-type three-electrode system, leading to the misunderstanding of the deactivation mechanism. In this study, we investigated the effect of a fresh electrolyte on the ADT and recovery process. When the fresh electrolyte was used at every range of the cycle, the chances of incorrect detection of dissolved CO and Pt ions in the electrolyte were very low. When the same electrolyte was used throughout the test, the accumulated Pt ions were deposited on the surface of the Pt nanoparticles or carbon support, affording an increased electrochemical surface area (ECSA) of Pt. Therefore, we believe that periodic replacement by a fresh electrolyte or a continuous-flow electrolyte is essential for the precise determination of the structural and electrochemical changes in Pt/C catalysts.

Glucose oxidase and polyacrylic acid based water swellable enzyme-polymer conjugates for promoting glucose detection

Ji, Jungyeon,Joh, Han-Ik,Chung, Yongjin,Kwon, Yongchai The Royal Society of Chemistry 2017 Nanoscale Vol.9 No.41

<P>Glucose oxidase (GOx) and polyacrylic acid (PAA) based water swellable non-toxic enzyme-polymer conjugate (PAA-GOx) was immobilized on a substrate consisting of graphene oxide (GO) and polyethyleneimine (PEI) (GO-PEI) and the electrochemical performances of the new catalyst were investigated. According to the measurements, although the amount of GOx immobilized on PAA-GOx was lower than that on glutaraldehyde (GA)-GOx, which is a conventionally used conjugate, its catalytic activity was 9.6 times higher than that of GA-GOx. The superior catalytic activity (102.0 μA cm<SUP>−2</SUP>, 20 mM of glucose) and glucose sensitivity (6.9 μA cm<SUP>−2</SUP>mM<SUP>−1</SUP>) were due to its high swellability in water. Due to this, the PAA-GOx absorbs a large amount of aqueous glucose molecules and rapidly transfers them to the active site of GOx. Desirable hydrogen peroxide and glucose oxidation reactions are accordingly promoted. In addition, since PAA has abundant free carboxylic acid groups, the PAA-GOx forms covalent bonds with the GO-PEI to curtail the leaching-out of GOx molecules.</P>

폴리아크릴로니트릴 기반 탄소섬유의 기계적 특성에 미치는 탄화공정 연구

장다원(Dawon Jang),조한익(Han-Ik Joh),구본철(Bon-Cheol Ku),김성룡(SeoungRyoung Kim),방윤혁(YunHyuk Bang),이성호(Sungho Lee) 한국고분자학회 2017 폴리머 Vol.41 No.2

세 종류의 상용 폴리아크릴로니트릴(PAN) 섬유인 효성(HS), Blue star(BS) 그리고 Jilin(JL) 섬유를 연속식 안정화를 거쳐 안정화 섬유를 제조한 후 튜브형로 내에서 2 및 10 ℃/min의 탄화 속도로 1050 ℃에서 탄화하였다. 제조된 탄소섬유의 구조분석을 위하여, X-ray diffraction(XRD) 및 Raman 분광기를 실행하였다. 승온속도와 PAN 섬유의 종류에 관계없이 구조 특성은 크게 다르지 않았다. 그러나 승온속도가 낮을 때 세 종류의 섬유 모두 인장강도가 증가하는 경향을 보였다. 효성 섬유로 제조된 탄소섬유는 승온속도가 2와 10 ℃/min일 때 각각 ~4.1와 ~2.6 GPa의 인장강도를 나타내었다. 인장 탄성률은 또한 낮은 승온속도로 탄화한 섬유가 더 높은 값을 가졌고, 효성 탄소섬유의 값은 ~253(2 ℃/min)와 ~196 GPa(10 ℃/min)이었다. X-ray photoelectron spectroscopy(XPS) 분석을 통하여 승온속도에 따라 탄소함량의 큰 차이는 없었으나 낮은 승온속도로 처리한 탄소섬유가 더 높은 sp3 구조 함량을 갖는 것을 확인하였다. 이는 탄소섬유의 화학적 구조가 기계적 물성에 중요한 역할을 한다는 것을 보여준다. Three types of commercially available polyacrylonitrile (PAN) fibers such as Hyosung (HS), Blue star (BS), and Jilin (JL) fibers were stabilized by continuous system and followed by carbonization at 1050 ℃ with heating rates of 2 and 10 ℃/min in a tubular furnace. To investigate structures of resulting carbon fibers (CFs), X-ray diffraction (XRD) and Raman spectroscopy were performed. Without regarding heating rate in carbonization and types of PAN fibers, structural properties were not significantly different. However, a lower heating rate resulted in higher tensile strength with all types of PAN fibers. CFs based on HS PAN fibers showed tensile strength of ~4.1 and ~2.6 GPa with heating rates of 2 and 10 ℃/min, respectively. Tensile modulus also increased with a lower heating rate, and the values of HS CFs are ~253 (2 ℃/min) to ~196 GPa (10 ℃/min). X-ray photoelectron spectroscopy (XPS) revealed that CFs prepared with slow heating contained higher content of sp3 even though there was no significant different in carbon content. These suggest that chemical structure play an important role in mechanical properties of CFs.

유리피판술을 이용한 구축성 화상반흔의 교정

임 풍,허 진,조성필,장익수,한기택 大韓成形外科學會 1996 Archives of Plastic Surgery Vol.23 No.3

Burn scar contractures of the various joint areas including anterior cervical region, popliteal region, ankle, antecubital region and wrist accompanied with severe functional limitations and esthetic problems. Many authors recommended full-thickness, split-thickness skin graft, local skin flap, or distant skin flap. But the recurrence of the contracture and many following procedures have been troublesome after these surgeries. Recent progress in the field of microvascular surgery has opened the way for various types of free transfer. The microvascular surgery enabled the various joint regions to be resurfaced with free flap and so the recurrence of contracture was prevented. Authors treated 20 patients with severe and recurrent burn scar contracture of the various joint regions using various microvascular free flap transfer. We obtained satisfactory functional results without late recurrence of the contracture of the transferred flaps.

Effect of pre-annealing on chemical configuration and heteroatom doping of highly active carbon catalysts for the oxygen reduction reaction

Hae Ri Lee,Seunggyun Han,Jong Yoon Lee,Gwanwon Lee,Sungho Lee,Han-Ik Joh 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

Heteroatom-doped carbon catalysts are promising alternatives to platinum group metal-free catalysts foroxygen reduction reaction (ORR). To enhance the ORR activity of carbon-based catalysts, the break ofelectroneutrality and number of active sites must be maximized. In this study, an annealing process ata mild temperature was introduced before heteroatom doping to control the content and configurationof the oxygen functional groups on the graphene oxide (GO). Pre-annealing affects the chemical configurationand the porosity of GO such that the epoxy groups are converted into carbonyl groups accompanyingthe defect formation. Interestingly, The carbonyl-enriched environment allowed ammonia borane,as a dopant with nitrogen and boron atoms, the enhanced doping performance, inducing the formation ofhigher number of heteroatom doping sites and additional defects in the graphene lattice. The aBNG-150catalyst demonstrated outstanding ORR activity in both half- and single-cell evaluations because it hadthe highest heteroatom content and meso/macropores derived from the elimination of oxygen functionalgroups, which can facilitate ORR catalytic activity and O2 diffusion pathway. Therefore, we believe thatthis approach provides an effective route for synthesizing carbon-based catalysts with remarkable ORRperformances.

Synthesis of porous carbon nanofiber with bamboo-like carbon nanofiber branches by one-step carbonization process

Yoo, Seung Hwa,Joh, Han-Ik,Lee, Sungho Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.402 No.-

<P><B>Abstract</B></P> <P>Porous carbon nanofibers (PCNFs) with CNF branches (PCNF/bCNF) were synthesized by a simple heat treatment method. Conventional methods to synthesize this unique structure usually follow a typical route, which consists of CNF preparation, catalyst deposition, and secondary CNF growth. In contrast, our method utilized a one-step carbonization process of polymer nanofibers, which were electrospun from a one-pot solution consisted of polyacrylonitrile, polystyrene (PS), and iron acetylacetonate. Various structures of PCNF/CNF were synthesized by changing the solution composition and molecular weight of PS. It was verified that the content and molecular weight of PS were critical for the growth of catalyst particles and subsequent growth of CNF branches. The morphology, phase of catalyst, and carbon structure of PCNF/bCNF were analyzed at different temperature steps during carbonization. It was found that pores were generated by the evaporation of PS and the catalyst particles were formed on the surface of PCNF at 700°C. The gases originated from the evaporation of PS acted as a carbon source for the growth of CNF branches that started at 900°C. Finally, when the carbonization process was finished at 1200°C, uniform and abundant CNF branches were formed on the surface of PCNF.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous carbon nanofiber with bamboo-like carbon nanofiber branches (PCNF/bCNF) was synthesized by electrospinning and heat treatments. </LI> <LI> Unlike the conventional methods, PCNF/bCNF was readily synthesized by a one-step carbonization process. </LI> <LI> The morphology of PCNF/bCNF was easily controlled by changing the polystyrene amount, molecular weight and amount of iron precursor of the spinning solution. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>