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Carbon nanotubes/nickel-cobalt hydroxide nanorods composite for supercapacitor applictation
장기훈,안희준 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Supercapacitors have intrigued researchers because of their greater energy density compared to conventional capacitors and their greater power density than batteries, as well as their long cycle life. However, for high power applications, a major disadvantage is that they have unsatisfactory energy density compared to batteries. To increase the energy density of supercapacitors, increasing the potential range is an effective approach. Carbon can complement or replace batteries in electrical energy storage and harvesting applications, where high power delivery and wide potential range are needed. Among them, CNTs are an attractive solution for energy storage devices due to their unique properties such as high chemical stability, high aspect ratio, strong mechanical strength, and high activated surface area. Alternative pseudocapacitive materials have proven to be promising materials for supercapacitor applications. Among these other metal oxides/hydroxides, nickel- and cobalt-based materials are considered the most promising for the next generation of supercapacitors because of their high specific capacitances, cost effectiveness, and natural abundance. Herein, multi-walled carbon nanotube (MWCNT) and nickel-cobalt binary metal hydroxide nanorod hybrids have been developed through the chemical synthesis of binary metal hydroxide on a MWCNT surface. These hybrids show enhanced supercapacitive performance and cycling ability. In this study, we report on the synthesis of nickel-cobalt hydroxide and CNT composites on a stainless steel substrate with promising charge storage performance. These electrodes yield a significantly high capacitance of 502 F/g with a high energy density of 69 Wh/kg at a scan rate of 5 mV/s. The film is stable up to 5000 cycles with greater than 80% capacitance retention.
장기훈,이성원,유성일,Rahul R. Salunkhe,정일두,최성민,안희준 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.10
Mn3O4/multi-walled carbon nanotube (MWCNT) composites are prepared by chemically synthesizing Mn3O4 nanoparticles on a MWCNT film at room temperature. Structural and morphological characterization has been carried out using X-ray diffraction (XRD) and scanning and transmission electron microscopies (SEM and TEM). These reveal that polycrystalline Mn3O4 nanoparticles, with sizes of about 10-20 nm, aggregate to form larger nanoparticles (50-200 nm), and the Mn3O4 nanoparticles are attached inhomogeneously on MWCNTs. The electrochemical behavior of the composites is analyzed by cyclic voltammetry experiment. The Mn3O4/ MWCNT composite exhibits a specific capacitance of 257 Fg−1 at a scan rate of 5 mVs−1, which is about 3.5 times higher than that of the pure Mn3O4. Cycle-life tests show that the specific capacitance of the Mn3O4/ MWCNT composite is stable up to 1000 cycles with about 85% capacitance retention, which is better than the pure Mn3O4 electrode. The improved supercapacitive performance of the Mn3O4/MWCNT composite electrode can be attributed to the synergistic effects of the Mn3O4 nanoparticles and the MWCNTs, which arises not only from the combination of pseudocapacitance from Mn3O4 nanoparticles and electric double layer capacitance from the MWCNTs but also from the increased surface area, pore volume and conducting property of the MWCNT network.
장기훈,임동균,신승중 한국인터넷방송통신학회 2010 한국인터넷방송통신학회 논문지 Vol.10 No.6
이 연구는 실업계 고등학교 전자회로 교과서 내용의 효과적인 실습을 위한 과제 개발에 관한 것이다. 이 논문은 먼저 현재 실업계 고등학교에서 사용하는 제 7차 교육과정의 전자회로 교과서에서 다루는 실습내용에 대한 문제와 이의 발전방향으로 학생들에게 수업동기를 유발시킬 새로운 과제를 제시 하였다. 기존 실업계 고등학교 전자회로 교과서의 내용은 학생들에게 과목을 이해시키기 위해 다양한 주제의 단원들이 독립되어 단원별로 구분된 실습을 진행하도록 되어 있다. 따라서 학생들이 단원별로 습득한 회로지식을 연계 및 응용하는데 제한이 있으며 학생들에게 무의미한 실습의 반복으로 받아들여져 학습동기를 저해하게 된다. 이에 연구자는 이 연구를 통해 현재 교과서의 단원별 실습내용을 수정하고 추가하여 모듈로 제작하되, 교과가 종료되는 시기에 단원별 실습의 결과물인 모듈들을 조립하여 유용한 기능을 수행하는 하나의 전자기기를 완성하도록 실습과제를 제시하였다. 이러한 실습방법을 통해 학생들은 각 과제를 완성해나가며 최종 목표달성을 하였을 때 성취감을 얻을 수 있을 것이며, 그 과정에서 학습효과는 더욱 높아질 것이다. 이 논문에서 제시되는 실습과제는 회로 설계부터 시뮬레이션을 통해 회로의 정상작동을 검증하였고 이를 바탕으로 회로를 실제 제작하여 동작내용을 측정하고 확인하였다. This paper is about a development of effective practice subject in electronic circuit textbook of industrial high school. This paper introduces generally about the practice subject in electronic circuit textbook of industrial high school of the 7th National curriculum and presents problem of current practice and makes an alternative idea that improve current practice. The contents of current electronic circuit textbook of industrial high school have variety topics and these topics are independence and separated. So students have some problems to apply of learned knowledge. Therefore, researcher improved the various electronic circuit practice in current electronic circuit text book and added new practice and manufactured a electronic circuit module based on these circuits. And researcher suggested new practice subject what useful electronic equipment that assembled module of result of electronic circuit practice of each section. When the last subjects are accomplished the students may have feel of achievement and high study effect from these practice. The practice subjects of this paper were manufactured after verification and tested it's performance by computer simulation program