아민 기능화된 탄소나노튜브의 분산상태 및 표면자유 에너지 변화가 탄소나노튜브/탄소섬유강화 복합소재의 기계적 특성에 미치는 영향

최웅기,박길영,신홍석,국윤수,김병석,서민강,Choi, Woong-Ki,Park, Gil-Young,Shin, Hong-Suk,Kuk, Yun-Su,Kim, Byung-Shuk,Seo, Min-Kang 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.3

In this work, the effects of the dispersive condition and surface energy change of multi-walled carbon nanotube (MWCNT) on the mechanical properties of amino-functionalized MWCNT containing carbon fibers-reinforced epoxy composites were studied. Amino-functionalization of MWCNT was carried out by grafting spermidine and p-phenylenediamine onto the surfaces of MWCNT through amidation. The surface properties of the MWCNT before and after amidation were observed using scanning electron microscope (SEM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscope (XPS), microscope, and contact angle measurements. Theoretical interfacial adhesions between the MWCNT and the epoxy resins were studied by calculating the work of adhesion and demonstrated by interlaminar shear strength (ILSS). From the experimental results, it was found that amino-functionalized MWCNT showed quite a homogeneous dispersion state in epoxy matrix resins. Additionally, the interfacial adhesions could be improved by amino-functionalizing MWCNTs surfaces. Consequently, the introduction of an amino-functional group on MWCNT surfaces positively affected the dispersibility of MWCNT, which resulted in improving the mechanical properties of the carbon fibers-reinforced epoxy composites.

탄소섬유기반 고성능 열가소성 복합재료 개발을 위한 표면처리 연구

최웅기(Woong-Ki Choi),길다림(Da-Lim Kil),오상엽(Sang-Yup Oh),서민강(Min-Kang Seo) 한국자동차공학회 2016 한국자동차공학회 부문종합 학술대회 Vol.2016 No.5

A Study on Oxidation Behaviors of IG and NBG Nuclear Graphites

최웅기(Choi, Woong-Ki),김병주(Kim, Byung-Joo),지세환(Chi, Se-Hwan),박수진(Park, Soo-Jin) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.11

In this work, the oxidation-induced characteristics of five nuclear graphites (NBG-17, NBG-18, NBG-25, IG-110, and IG-430) were studied. The oxidation characteristics of nuclear graphites were measured at the three temperature areas (300, 600, and 900?C). As experimental results, the pore size of oxidized graphite was increased with increasing of oxidation time. It was also found that the oxdation rate was propotional to the oxidation temperature and time. This was probably due to the oxidation was occurred on the surface and inner bulk phase of nuclear graphites at the same time by the socalled chemical regime.

흰쥐에서 저주파소음에 의한 스트레스 반응

최웅기 ( Woong Ki Choi ),이규섭 ( Kyu Sop Lee ),정혜영 ( Hye Young Joung ),이영창 ( Young Chang Lee ),손진훈 ( Jin Hun Sohn ),이배환 ( Bae Hwan Lee ),변광호 ( Kwang Ho Pyun ),심인섭 ( In Sop Shim ) 한국감성과학회 2007 감성과학 Vol.10 No.3

저주파소음(low frequency noise; LFN)은 인체의 다양한 기관과 정신적 상태에 영향을 미치며, 진동음향질환(vibroacoustic disease; VAD)같은 질병들을 야기 시킨다. 이전의 연구에서는 인간 또는 설치류에서 VAD는 우울증 또는 불안장애와 같은 만성적인 정신 건강에 위험을 미친다고 보고되고 있다. 본 연구에서는 LFN이 스트레스의 신경생리적 반응에 미치는 영향을 규명하고자 하였다. 이를 위하여, LFN에 노출된 흰쥐에서 스트레스 반응에 중요한 역할을 하는 paraventricular nucleus of the hypothalamus(PVN)에서 초기발현유전자인 c-fos 양성세포 발현, locus coeruleus(LC)에서 NE 생성 효소인 tyrosine hydroxylase(TH) 양성세포 발현과 스트레스 호르몬의 농도를 측정하였다. LFN 집단은 각각 32.5Hz 와 125Hz를 하루에 4시간씩 이틀 동안 소음에 노출 하였으며, 정상집단은 소음에 노출되지 않도록 하였다. 저주파소음에 노출 후 집단 간 혈액내 코르티코스테론 분석과, 면역조직염색법을 이용하여 스트레스에 반응하는 PVN에서 c-fos발현과, LC에서 TH를 분석한 결과, PVN에서는 c-fos의 발현과 LC에서 TH의 발현이 증가됨을 관찰할 수 있었으며, 그리고 혈중 코르티코스테론의 농도 또한 LFN집단에서 높게 발현됨을 확인 하였다. 그리고 32.5Hz 보다 125Hz의 소음에서 면역염색반응과 코르티코스테론의 결과가 다소 높게 나타남을 알 수 있었다. 이러한 결과는 저주파소음에 의해 스트레스와 연관된 뇌의 부위에서 c-Fos와 TH의 발현이 증가됨을 증명하고 있다. 따라서 저주파소음은 일반적인 스트레스에 의한 반응과 비슷한 신경적 특징들을 보여주고 있다. 그리고 저주파소음에 의한 중추, 말초신경계의 활성화는 아마도 진동음향질환과 같은 행동장애 질병과 관련이 있을 것임을 시사한다. Exposure to low frequency noise(LFN) can lead to vibroacoustic diseases(VADs), which include a systemic disease with lesions in a broad spectrum of organs and a psychiatric condition. It is known that VAD is an established risk factor for the development of many psychological conditions in humans and rodents, including major depression and anxiety disorder. The present study investigated the effects of LFN on neuronal stress responses in the rat brain. The neuronal expression of the proto-oncogene c-fos in the paraventricular nucleus(PVN) of the hypothalamus and tyrosine hydroxylase(TH) in the LC was observed. The immunocytochemical detection of the Fos protein and TH has been used as a marker of neuronal activation in response to stress. In addition, corticosterone concentration was evaluated by using an enzyme-linked immunosorbent assay(ELISA) The LFN groups were exposed to 32.5Hz and 125Hz of noise(4hr/day for 2days). The numbers of c-fos and TH-immunoreactive cells in the PVN and LC were significantly increased in the LFN groups(32.5Hz and 125Hz) compared to the normal group. Corticosterone concentration in plasma was also increased in LFN groups. The present results demonstrated that exposure with LFN produced a pronounced increase in expression of c-Fos and TH in stress-relevant brain areas. These results suggest that the neural characteristics involved in LFN are similar to those activated by typical processive stressors. These results also suggest that the central and peripheral activations by LFN may be related to LFN-related negative behavioral dysfunctions such as VADs.

탄소섬유의 사이징처리가 탄소섬유/나일론6 복합재료의 기계적 계면 특성에 미치는 영향

최웅기 ( Woong Ki Choi ),김병주 ( Byung Joo Kim ),민병각 ( Byung Gak Min ),배경민 ( Kyong Min Bae ),박수진 ( Soo Jin Park ) 한국고무학회 2010 엘라스토머 및 콤포지트 Vol.45 No.1

탄소섬유/나일론 수지 복합재료의 계면결합력의 향상을 위해 폴리아크릴로니트릴(PAN)계 탄소섬유의 표면에 실란계, 설파이드계, 이미드계 계면결합제를 이용해서 사이징 처리를 수행하였으며, 사이징 처리된 탄소섬유의 젖음성과 표면자유에너지는 접촉각을 통해 확인하였다. 사이징 처리되어 제조된 복합재료의 기계적 계면물성은 임계응력세기인자를 통하여 확인하였으며, 파단실험 후 파단면은 주사전자현미경을 통해 관찰하였다. 실험결과 실란계로 사이징처리된 탄소섬유가 다른 사이징 처리에 비해 표면자유에너지가 큰 것을 접촉각 측정을 통해 관찰하였다. 한편 사이징처리된 탄소섬유 강화 나일론 복합재의 경우 미처리 탄소섬유를 이용한 복합재에 비해 높은 기계적 계면강도를 보였다. 이러한 결과는 섬유의 표면자유에너지가 탄소섬유와 나일론6 기지 사이의 계면결합력의 증대를 유도하여 복합재료의 기계적 계면강도가 증가된 것으로 판단된다. The sizing treatments of PAN-based carbon fiber surfaces were carried out in order to improve the interfacial adhesion in the carbon fibers/nylon6 composite system. The parameter to characterize the wetting performance and surface free energy of the sized fibers were determined by a contact angle method. The mechanical interfacial properties of the composites were investigated using critical stress intensity factor (KIC). The cross-section morphologies of sized CFs/nylon6 composites were observed by SEM. As the experimental results, it was observed that silane-based sizing treated carbon fibers showed higher surface free energies than other sizing treatments. In particular, the KIC of the sizing-treated carbon fibers reinforced composites showed higher values than those of untreated carbon fibers-reinforced composites. This result indicated that the increase in the surface free energy of the fibers leads to the improvement of the mechanical interfacial properties of carbon fibers/nylon6 composites.

Effect of Silane Coupling Agents on Mechanical Interfacial Strength of Carbon Fibers-reinforced Polarized-Polypropylene Matrix Composites

W. K. Choi(최웅기),Y. S. Kuk(국윤수),M. K. Seo(서민강) 한국생산제조학회 2018 한국생산제조시스템학회 학술발표대회 논문집 Vol.2018 No.5

팽창흑연,에리스리톨 복합체의 열적거동에 관한 연구

최보경 ( Bo Kyung Choi ),최웅기 ( Woong Ki Choi ),국윤수 ( Yun Su Kuk ),김홍건 ( Hong Gun Kim ),서민강 ( Min Kang Seo ) 한국공업화학회 2014 공업화학 Vol.25 No.5

In this paper, the thermal behaviors of expanded graphite(EG)/erythritol composites with different contents of EG were studied. The surface and structure properties of the composites were determined by using scanning electron microscope(SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD), respectively. The thermal properties were investigated by differential scanning calorimetry (DSC) and thermal conductivity (TC). As experimental results, the thermal conductivityof the composites increased with increasing the EG content. However, the latent heat was somewhat decreased in the presence of EG. We could concluded that EG was highly promising materials for improving the heat transfer enhancement and energy storage capacity of phase change materials (PCMs).

탄소나노튜브 무전해 니켈 도금과 양극산화가 탄소나노튜브/에폭시 복합재료의 전자파 차폐효율에 미치는 영향

함은광,고재경,최웅기,김영근,서민강,Ham, Eun-Kwang,Ko, Jae-Kyoung,Choi, Woong-Ki,Kim, Young-Keun,Seo, Min-Kang 한국섬유공학회 2015 한국섬유공학회지 Vol.52 No.3

In this work, the influence of electroless nickel-plated and anodized carbon nanotubes (CNT) on the electromagnetic interference shielding effectiveness (EMI-SE) properties of CNT/epoxy composites was studied. The surface properties of modified CNT were measured by field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The composites were prepared by adding 7 wt% modified CNT to epoxy. The EMI-SE of the composites was evaluated through reflection and absorption loss in the frequency range of 30 MHz-1.5 GHz. The electric conductivity was measured using a 4-point-probe electric resistivity tester. The results show that, the EMI-SE of the composites with 3 min nickel-plated CNT was the highest. The reflection loss of anodized CNT was found to be sharply increased in the frequency range of 1.25-1.35 GHz. In addition, the reflection loss of modified CNT was improved, but the absorption loss was decreased, respectively. This was probably because electroless nickel-plating and anodization led to the improvement in the polarity of the CNT surface which increased the EMI-SE of the composites.

탄소나노튜브 표면 관능기가 탄소나노튜브/고분자 복합재료의 기계적 및 열적 특성에 미치는 영향

함은광(Eun-Kwang Ham),최웅기(Woong-Ki Choi),김영근(Young-Keun Kim),서민강(Min-Kang Seo) 한국고분자학회 2015 폴리머 Vol.39 No.6

본 연구에서는 탄소나노튜브 관능기의 형태가 탄소나노튜브/고분자 복합재료의 기계적 및 열적 특성에 미치는 영향에 관하여 알아보았다. 탄소나노튜브의 관능기를 정량적으로 분석하기위해 X-선 광전자 분광법을 사용하였다. 복합재료는 에폭시 수지와 비닐에스터 수지에 산처리된 탄소나노튜브를 0.7 wt%를 첨가하여 제작하였다. 실험결과, 탄소나노튜브/에폭시 복합재료는 8 M 질산으로 처리된 탄소나노튜브를 첨가하였을 때 가장 높은 기계적 특성을 나타내었으며, 탄소나노튜브/비닐에스터 복합재료는 황산/질산 혼합액으로 처리된 탄소나노튜브를 첨가하였을 때 기계적 특성이 향상됨을 알 수 있었다. 열전도도는 에폭시와 비닐에스터에 8 M 질산으로 처리된 탄소나노튜브가 첨가되었을 때 향상되었다. 이는 탄소나노튜브에 카보닐기(C=O)의 도입으로 탄소나노튜브/에폭시 복합재료의 계면접착력이 개선되었으며, 카복시기(O-C=O)의 증가는 탄소나노튜브/비닐에스터 복합재료의 기계적 물성 향상에 기여하였다. 또한 탄소나노튜브/에폭시 복합재료와 탄소나노튜브/비닐에스터 복합재료의 열전도도는 탄소나노튜브의 표면구조와 길이에 영향을 받는다고 판단된다. The influence of carbon nanotube (CNT) functional groups on mechanical and thermal properties of CNT/polymer composites was investigated. The functional groups of the CNT were quantitatively analyzed using X-ray photoelectron spectroscopy. The composites were prepared by adding the 0.7 wt% acid-treated CNT in the epoxy resins and vinyl ester resins, respectively. As a result, the CNT/epoxy composites showed the highest tensile and flexural properties when addition of the 8 M HNO3-treated CNT. Tensile and thermal properties of the CNT/vinyl ester composites were improved by addition of H2SO4/HNO3-treated CNT. Thermal conductivities of CNT/epoxy composites and CNT/vinyl ester composites were improved in 8M HNO3-treated CNT. Introduction of carbonyl group (C=O) on CNT led to improvement of interfacial bonding in CNT/epoxy composites. The increase in the content of carboxyl group (O-C=O) on CNT contributed to increase in mechanical properties of CNT/vinyl ester composites. Also, the thermal conductivity of CNT/epoxy composites and CNT/vinyl ester composites were probably influenced on the structure and length of the CNT.

전기화학적 산화처리가 탄소섬유/극성화된 폴리프로필렌 복합재의 기계적 계면 특성에 미치는 영향

김현일 ( Hyun Il Kim ),최웅기 ( Woong Ki Choi ),오상엽 ( Sang Yub Oh ),안계혁 ( Kay Hyeok An ),김병주 ( Byung Joo Kim ) 한국공업화학회 2013 공업화학 Vol.24 No.5

In this work, the effects of electrochemical oxidation of carbon fiber surfaces on mechanical interfacial properties of carbon fibers-reinforced polarized-polypropylene matrix composites were studied with various current densities during the treatments. Surface properties of the fibers before and after treatments were observed by SEM, AFM, XPS, and contact angle measurements. Mechanical interfacial properties of the composites were measured in terms of critical stress intensity factor (KIC). From the results it was found that O1s peaks of the fiber surfaces were strengthened after electrochemical oxidation which led to the enhancement of surface free energy of the fiber, resulting in good mechanical performance of the composites. It can be concluded that electrochemical oxidation of the carbon fiber surfaces can control the interfacial adhesion between the carbon fibers and polarized-polypropylene in this composites system.