Increase in graphitization and electrical conductivity of glassy carbon nanowires by rapid thermal annealing

Lim, Yeongjin,Chu, Jae Hwan,Lee, Do Hee,Kwon, Soon-Yong,Shin, Heungjoo ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.702 No.-

<P><B>Abstract</B></P> <P>Glassy carbon (GC) exhibits numerous desirable properties such as high thermal and chemical stabilities, good hardness, and good thermal and electrical conductivities. Moreover, GC can be manufactured into micro-/nanostructures through the versatile microfabrication technology, or carbon-micro electromechanical systems, which includes polymer patterning and pyrolysis. However, despite these advantages, there are growing demands for enhancing the electrical conductivity of GC, so that it can compensate or be substituted for other carbon allotropes such as graphite, carbon nanotubes, and graphene. In this study, we demonstrated that simple rapid thermal annealing (RTA) can dramatically enhance the electrical conductivity of pyrolyzed GC nanostructures by ∼ 300%. In this research, two different architectures of 1D carbon nanostructures such as a suspended nanowire that was separated from the substrate with a fixed distance and a substrate-bound nanowire were fabricated using conventional UV-lithography and pyrolysis processes, and their conductivity enhancement behaviors via RTA were studied. After the RTA process, the carbon/oxygen content and G-/D-band intensity ratios, which are correlated to the electrical conductivity, were enhanced, depending on the pyrolysis temperature. GC structures pyrolyzed at relatively low temperatures became more electrically conductive after the RTA process owing to their relatively higher oxygen content. This is because carbon atoms interconnected to oxygen atoms tend to align more readily than those corresponding to other carbon compositions because of the graphene healing mechanism. In addition, the architecture of the carbon nanostructures (<I>i.e</I>., whether they were suspended or substrate-bound nanowires) influenced the RTA-induced increase in electrical conductivity; the former showed a greater increase in electrical conductivity owing to its larger portion of well-aligned carbon atoms at the surface compared to the latter carbon structure. This is because graphitization is initiated on the surface and then proceeds to the carbon core in the heat treatment. In addition, tensile stress generated only at the suspended carbon nanowires during the pyrolysis process is assumed to enhance further the electrical conductivity via RTA. For instance, the electrical conductivity of the suspended carbon nanowires formed by pyrolysis at 600 °C was enhanced to ∼59,000 S/m after the RTA process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Suspended/substrate-bound glassy carbon nanowires were fabricated using carbon-MEMS. </LI> <LI> The electrical conductivity of carbon nanowires was enhanced by ∼3 times using RTA. </LI> <LI> Long-range graphitic order was induced via RTA. </LI> <LI> Suspended nanowires exhibited twice higher increase in electrical conductivity. </LI> </UL> </P>

페놀수지 및 에틸렌 글리콜을 첨가한 유리질 카본 코팅층의 물성 제어

주상현,주영준,이혁준,심영진,박동진,조광연,Joo, Sang Hyun,Joo, Young Jun,Lee, Hyuk Jun,Sim, Young Jin,Park, Dong Jin,Cho, Kwang Youn 한국결정성장학회 2022 한국결정성장학회지 Vol.32 No.3

In this study, glassy carbon coating was performed on the graphite using a phenolic resin and a curing agent was mixed with ethylene glycol as an additive to form the uniform surface. The phenolic resin was dried and cured under the environments of hot air, then converted into a glassy carbon layer by pyrolysis at 500~1,500℃. FTIR, XRD, SEM analysis, and density/porosity/contact angle measurement were performed for characterization of glassy carbon. The pyrolysis temperature for high-quality glassy carbon was optimized to be about 1,000℃. As the content of the additive increased, the effect of reducing surface defects on the coated surface, reduction of porosity, increase of contact angle, and increase of density were investigated in this study. The method of forming a glassy carbon coating layer through an additive is expected to be applicable to graphite coating and other fields.

Glassy Carbon의 초정밀 가공

황연(Yeon Hwang),이현성(Hyeon-Sung Lee),김혜정(Hye-Jeong Kim),김정호(Jeong-Ho Kim) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.3

Glassy carbon is widely used for high temperature melting process such as quartz due to its thermal stability. For utilizing Classy Carbon to glass mold press(GMP) optical lens, brittleness of Glassy Carbon is main obstacle of ultraprecision machining. Thus authors investigated ductile machining of Glassy Carbon adopting turning and grinding process respectively. From the experiments, ultraprecision turning surfaces resulted brittle crack in all machining conditions and ultraprecision grinding surfaces showed semi-ductile mode in small undeformed chip thickness conditions.

고품질 유리질 카본 코팅을 위한 페놀 수지의 고압 경화

홍석기,조광연,권오현,조용수,장승조 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.2

Successful coating of high quality glassy carbon is introduced by applying high pressure during the curing process of dip-coated phenol resin on graphite. The dependence of the applied pressure on the quality of the glassy carbon layer has not been reported so far. Pressure was changed from 0 to 400 psi during curing at 200℃. After carbonized at 1100℃ in inert atmosphere for the 400 psicured sample, as a promising result, a thick (~ 3 mm) and smooth glassy carbon layer could be obtained without any breakage, and the yield of carbonization was remarkably increased. It is believed that the cross-linking of resins results in decreasing volatile contents and, thus, increasing the yield of the glassy carbon. The origin of the improvement is discussed on the basis of several analytical results including FE-SEM, FT-IT and Raman spectrum.

렌즈 성형용 유리탄소 금형의 초정밀연삭

황연(Yeon Hwang),차두환(Du-Hwan Cha),김정호(Jeong-Ho Kim),김혜정(Hye-Jeong Kim) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.3

In this study, glassy carbon was ground for lens core of glass mold press. Ultraprecision grinding process was applied for machining of core surfaces. During the process, brittle crack occurred because of hard-brittleness of glassy carbon. Author investigated optimized grinding conditions from the viewpoint of ductile mode grinding. Geometrical undeformed chip thickness was adopted for critical chip thickness that enables crack free surface. Machined cores are utilized for biaspheric glass lens fabrication and surfaces of lens were compared for verification of ground surface.

Local crystallization and enhanced thermoelectric performance of glassy carbon induced by the electron beam irradiation

오인선,조준현,박정민,Jongmin Lee,Heungjoo Shin,유정우 한국물리학회 2016 Current Applied Physics Vol.16 No.11

Glassy carbon can be used in a variety of harsh environments because it exhibits low electrical resistance, high thermal stability, chemically impermeability and hardness. In this work, we studied the potential application of the pyrolized glassy carbon as a thermoelectric material by electron beam irradiation. Irradiation with electron beam energy of 1.4 MeV and 0.2 MeV triggered local crystallization of glassy carbon, which was determined by a Raman spectroscopy. As the irradiation time was increased, the number of sp2 hybridized carbons was gradually increased while the number of disordered carbons was decreased. This electron beam induced local crystallization caused a synergetic effect on a thermoelectric power factor of the studied glassy carbon films. Although the electrical conductivity was decreased by the e-beam irradiation, the Seebeck coefficient was significantly enhanced resulting in an improved power factor. The optimal power factor we obtained for the irradiated glassy carbon was ~50% higher than that of the non-irradiated sample.

Local crystallization and enhanced thermoelectric performance of glassy carbon induced by the electron beam irradiation

Oh, I.,Jo, J.,Park, J.,Lee, J.,Shin, H.,Yoo, J.W. Elsevier 2016 Current Applied Physics Vol.16 No.11

<P>Glassy carbon can be used in a variety of harsh environments because it exhibits low electrical resistance, high thermal stability, chemically impermeability and hardness. In this work, we studied the potential application of the pyrolized glassy carbon as a thermoelectric material by electron beam irradiation. Irradiation with electron beam energy of 1.4 MeV and 0.2 MeV triggered local crystallization of glassy carbon, which was determined by a Raman spectroscopy. As the irradiation time was increased, the number of sp(2) hybridized carbons was gradually increased while the number of disordered carbons was decreased. This electron beam induced local crystallization caused a synergetic effect on a thermoelectric power factor of the studied glassy carbon films. Although the electrical conductivity was decreased by the e-beam irradiation, the Seebeck coefficient was significantly enhanced resulting in an improved power factor. The optimal power factor we obtained for the irradiated glassy carbon was similar to 50% higher than that of the non-irradiated sample. (C) 2016 Elsevier B.V. All rights reserved.</P>

다양한 pH 용액에서 네자리 Schiff base 착물이 수식된 유리질탄소 전극의 산소환원 촉매적 특성

노선균 ( Seon Gyun Rho ),한신 ( Shin Han ) 조선대학교 공학기술연구원 2014 공학기술논문지 Vol.7 No.3

The electrocatalytic effect of oxygen reduction was investigated at glassy carbon electrode coated with tetradentate Schiff base transition metal(II) complexes ; Co(II)(SOPD), Co(II)2(SMPD)2 and Co(II)2(SPPD)2 in the 1 M KOH solution. The reduction current of oxygen measured by cyclic voltammetry was increased by about 150 % more than that of bare glassy carbon electrode and the reduction potential was shifted about 140 mV to the positive direction. The reduction current of oxygen was increased by raising scan rate and reduction potential was shifted to the negative potential direction. The electrocatalytic effect of oxygen reduction was investigated in various pH solutions by cyclic voltammetry at the glassy carbon electrode coated with tetradentate Schiff base transition metal(II) complexes. The reduction current of oxygen at glassy carbon electrode coated with Co(II)(SOPD) was increased by about 200 % more than that of bare glassy carbon electrode and the reduction potential was shifted about 300~350 mV to the positive direction, compared to those of bare glassy carbon electrode in the pH 4, 7, and 10 solution. In the pH 10 solution, especially, the reduction current of oxygen at the electrode coated with Co(II)2(SMPD)2 complex was increased by about 200 % and peak potential was shifted about 500 mV to the positive direction.

전자빔 조사에 의한 유리상 탄소에서의 구조적 변화와 열전 성능의 상관관계

오인선 ( Inseon Oh ),조준현 ( Junhyeon Jo ),안기석 ( Ki-seok An ),유정우 ( Jung-woo Yoo ) 한국복합재료학회 2016 Composites research Vol.29 No.4

유리상 탄소는 열적으로 안정하고, 화학적 반응성이 매우 낮으며, 다양한 크기로 제작이 가능하고, 전기적 저항 또한 낮아서 다양한 극한 환경에서 사용 가능하다. 이 논문에서는 전자빔 조사가 유리상 탄소 박막의 구조 변화에 미치는 영향과 그에 따른 열전효과 변화에 대해 연구하였다. 라만 분광 특성 분석을 바탕으로 유리상 탄소 박막에 전자빔 조사에 따라 결정화 또는 비정질화가 일어나는 것을 확인하였다. 또한, 이러한 결정변화가 유리상 탄소 박막의 자유전자 도핑 농도의 변화시키며 그에 따른 제백 상수나 전기적 전도도의 변화도 확인하였다. 전자빔 조사로 인하여 유리상 탄소의 열전파워 펙터가 최대 200%까지 향상되는 것을 보여 주었다. Glassy carbon can be utilized in a variety of harsh environment due to exceptional thermal stability and chemically impermeability along with scalability and low electrical resistance. In this work, we studied effects of electron(e)-beam irradiation on thermoelectric properties of the glassy carbon film. E-beam irradiation triggered local crystallization and/or amorphization of glassy carbon thin films, which was determined by a Raman spectroscopy. The structural change by e-beam irradiation leads to the change in the doping level of the glassy carbon, which can be inferred from the change of a Seebeck coefficient and an electric conductivity. The optimal power factor we obtained for the irradiated glassy carbon film was ~200% higher than that of the non-irradiated sample.

전기 화학적으로 활성화된 glassy carbon 전극에서의 전압-전류 법을 이용한 Clenbuterol 측정

이소희,박원철,Lee, Sohee,Piao, Yuanzhe 한국전기화학회 2014 한국전기화학회지 Vol.17 No.4

전기 화학적으로 활성화된 glassy carbon 전극을 사용하여 Clenbuterol 의 정량측정을 위해 신속하고 민감한 전압-전류 법을 개발하였다. 시차 펄스 전압-전류 법(Differential pulse voltammetry)을 이용하여, Clenbuterol에 대해 $1{\times}10^{-7}M$에서 $2{\times}10^{-5}M$의 범위에서 선형적인 반응을 보였으며 검출한계는 $6{\times}10^{-9}M$ (S/N = 3)이었다. Clenbuterol 의 농도가 $1{\times}10^{-6}M$에서의 상대표준편차는 4.3%이었다. 다양한 양의Clenbuterol이 포함된 소변 샘플로부터 96%의 회수율을 나타냈다. (N = 3, $5{\times}10^{-7}M$에서 $1{\times}10^{-6}M$의 Clenbuterol) A rapid and sensitive voltammetric method for the quantitative determination of Clenbuterol on electrochemically activated glassy carbon electrode has been developed. Using differential pulse voltammetry, the linear response range for the clenbuterol was between $1{\times}10^{-7}$ and $2{\times}10^{-5}M$, and the detection limit was $6{\times}10^{-9}M$ (S/N = 3). The relative standard derivation was 4.3% for $1{\times}10^{-6}M$ clenbuterol. Recoveries of 96% of the clenbuterol (n = 3) were obtained from urine spiked with different amounts in the ranges $5{\times}10^{-7}M$ and $1{\times}10^{-6}M$ by this method.