Synthesis and Characterization of Carbon Nanofibers Grown on Ni and Mo Catalysts by Chemical Vapor Deposition

장은이,박희구,최종하,이창섭 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.5

In this study, we synthesized carbon nanofibers using Ni and Mo catalysts by chemical vapor deposition. Catalysts used in the synthesis of carbon nanofibers were prepared by changing the molar ratio of nickel nitrate and ammonium molybdate. Precipitates were then obtained by reacting with ammonium carbonate. The optimum temperature for synthesis of carbon nanofibers was found by changing it between 600 and 800 °C. At these temperatures, carbon nanofibers were synthesized with various ratios of catalysts. Structural and physiochemical properties were analyzed by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy. The specific surface area of synthesized carbon nanofibers was measured by BET. It was found that characterization of carbon nanofibers were significantly affected by the synthesis temperature and the concentration ratio of metal catalysts. When the catalyst with the concentration ratio of Ni and Mo was 6:4 at 800 °C, uniform carbon nanofibers with a diameter of 50 nm were grown. Crystallinity and amorphicity of the synthesized carbon nanofiber were excellent compared to those of carbon nanofibers synthesized with metal catalysts in different concentration ratios. A three-electrode cell was prepared by using the synthesized carbon nanofibers as anode of Li secondary battery. The electrochemical properties of carbon nanofibers were examined through cyclic voltammetry and galvanostatic charge–discharge.

Fabrication of carbon nanofiber electrodes using poly(acrylonitrile‑co‑vinylimidazole) and their energy storage performance

Kyung‑Hye Jung,So Jeong Kim,Ye Ji Son,John P. Ferraris 한국탄소학회 2019 Carbon Letters Vol.29 No.2

For electrodes in electrochemical double-layer capacitors, carbon nanofibers (CNFs) were prepared by thermal treatment of precursor polymer nanofibers, fabricated by electrospinning. Poly(acrylonitrile-co-vinylimidazole) (PAV) was employed as a precursor polymer of carbon nanofibers due to the effective cyclization of PAV polymer chains during thermal treatment compared to a typical precursor, polyacrylonitrile (PAN). PAV solutions with different comonomer compositions were prepared and electrospun to produce precursor nanofibers. Surface images obtained from scanning electron microscopy showed that their nanofibrous structure was well preserved after carbonization. It was also confirmed that electrospun PAV nanofibers were successfully converted to carbon nanofibers after the carbonization step by Raman spectroscopy. Carbon nanofiber electrodes derived from PAV showed higher specific capacitances and energy/power densities than those from PAN, which was tested by coin-type cells. It was also shown that PAV with an acrylonitrile/vinylimidazole composition of 83:17 is most promising for the carbon nanofiber precursor exhibiting a specific capacitance of 114 F/g. Their energy and power density are 70.1 Wh/kg at 1 A/g and 9.5 W/kg at 6 A/g, respectively. In addition, pouch cells were assembled to load the higher amount of electrode materials in the cells, and a box-like cyclic voltammetry was obtained with high capacitances.

Polyacrylonitrile Nanofibers: Formation Mechanism and Applications as a Photoluminescent Material and Carbon-Nanofiber Precursor

Jang, J.,Bae, J.,Park, E. WILEY-VCH Verlag 2006 Advanced Functional Materials Vol.16 No.11

<P>The facile synthesis of polyacrylonitrile (PAN) nanofibers is achieved using a microemulsion polymerization. The detailed formation mechanism of polymer nanofibers is examined using electron microscopy and UV-vis and Fourier transform infrared spectroscopies, and the optoelectronic properties are studied by confocal laser scanning microscopy. The effects of surfactant properties, such as concentration, chain length, and ionic character, as well as monomer structure and polymerization temperature, on the structure of the resulting polymer nanofibers are also investigated extensively. Importantly, PAN nanofibers exhibited novel photoluminescence (PL), which is observed for the first time. The PL of PAN nanofibers is significantly different from that of PAN nanoparticles. The PAN nanofibers are also used as a precursor for carbon nanofibers. The carbonization temperature has a dominant effect on the degree of crystallinity of the resulting carbon nanofibers. This study is the first demonstration of the fabrication of polymer and carbon nanofibers using a convenient polymerization technique.</P> <B>Graphic Abstract</B> <P>Polymer nanofibers with tunable diameters (see figure) are fabricated by microemulsion polymerization. Sphere-to-cylinder micelle transformation due to the addition of ferric chloride is crucial for nanofiber formation. The diameter of the polymer nanofibers depends on the surfactant properties, the monomer type, and the polymerization temperature. This is the first demonstration of the convenient synthesis of polymer nanofibers using a simple polymerization strategy. <img src='wiley_img/1616301X-2006-16-11-ADFM200500598-content.gif' alt='wiley_img/1616301X-2006-16-11-ADFM200500598-content'> </P>

Growth of nickel-catalyzed carbon nanofibers using MPCVD method and their electrical properties

Kim, Sung-Hoon The Korea Association of Crystal Growth 2004 韓國結晶成長學會誌 Vol.14 No.1

Carbon nanofilaments were formed on silicon substrate via microwave plasma-enhanced chemical vapor deposition method. The structure of carbon nanofilaments was identified as the carbon nanofibers. The extent of carbon nanofibers growth and the diameters of carbon nanofibers increased with increasing the total pressure. The growth direction of carbon nanofibers was horizontal to the substrate. Laterally grown carbon nanofibers showed the semiconductor electrical characteristics.

Fabrication and electrochemical characterization of polyimide‐derived carbon nanofibers for self‐standing supercapacitor electrode materials

Han, Nam Koo,Ryu, Ji Hyung,Park, Do Un,Choi, Jae Hak,Jeong, Young Gyu John Wiley Sons, Inc. 2019 Journal of applied polymer science Vol.136 No.32

<P><B>ABSTRACT</B></P><P>We report the electrochemical performance of aromatic polyimide (PI)‐based carbon nanofibers (CNFs), which were fabricated by electrospinning, imidization, and carbonization process of poly(amic acid) (PAA) as an aromatic PI precursor. For the purpose, PAA solution was electrospun into nanofibers, which were then converted into CNFs via one‐step (PAA‐CNFs) or two‐step heat treatment (PI‐CNFs) of imidization and carbonization. The FTIR and Raman spectra demonstrated a successful structural evolution from PAA nanofibers to PI nanofibers to CNFs at the molecular level. The SEM images revealed that the average diameter of the nanofibers decreased noticeably via imidization and carbonization, while it decreased slightly with increasing the carbonization temperature from 800 °C to 1000 °C. In case of PI‐CNF carbonized at 1000 °C, a porous structure was developed on the surface of nanofibers. The electrical conductivity of PI‐CNFs, which was even higher than that of PAA‐CNFs, increased significantly from 0.41 to 2.50 S/cm with increasing the carbonization temperature. From cyclic voltammetry and galvanostatic charge/discharge tests, PI‐CNF carbonized at 1000 °C was evaluated to have a maximum electrochemical performance of specific capacitance of ~126.3 F/g, energy density of ~12.2 Wh/kg, and power density of ~160 W/kg, in addition to an excellent operational stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. <B>2019</B>, <I>136</I>, 47846.</P>

Fabrication of carbon nanofiber electrodes using poly(acrylonitrile‑co‑vinylimidazole) and their energy storage performance

정경혜,김소정,손예지,John P. Ferraris 한국탄소학회 2019 Carbon Letters Vol.29 No.2

For electrodes in electrochemical double-layer capacitors, carbon nanofibers (CNFs) were prepared by thermal treatment of precursor polymer nanofibers, fabricated by electrospinning. Poly(acrylonitrile-co-vinylimidazole) (PAV) was employed as a precursor polymer of carbon nanofibers due to the effective cyclization of PAV polymer chains during thermal treatment compared to a typical precursor, polyacrylonitrile (PAN). PAV solutions with different comonomer compositions were prepared and electrospun to produce precursor nanofibers. Surface images obtained from scanning electron microscopy showed that their nanofibrous structure was well preserved after carbonization. It was also confirmed that electrospun PAV nanofibers were successfully converted to carbon nanofibers after the carbonization step by Raman spectroscopy. Carbon nanofiber electrodes derived from PAV showed higher specific capacitances and energy/power densities than those from PAN, which was tested by coin-type cells. It was also shown that PAV with an acrylonitrile/vinylimidazole composition of 83:17 is most promising for the carbon nanofiber precursor exhibiting a specific capacitance of 114 F/g. Their energy and power density are 70.1 Wh/kg at 1 A/g and 9.5 W/kg at 6 A/g, respectively. In addition, pouch cells were assembled to load the higher amount of electrode materials in the cells, and a box-like cyclic voltammetry was obtained with high capacitances.

나노탄소섬유와 나노카바이드섬유를 이용한 복합재의 제조와 활용에 관한 연구

임연수,김기덕,이재춘,김명수,김성수 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.6

Fabrication of carbon fiber reinforced composites was carried out by hand lay-up method. Carbon nanofibers and SiC nanofibers were used as filler in the composites fabrication. Carbon nanofibers, one of the new carbon materials, have 5∼500 nm in diameter and 5-10 nm in length. SiC nanofibers were modified by silicon monoxide vapor with carbon nanofibers. The composites were carbonized at 1000$^{\circ}C$ in a nitrogen atmosphere, and then densified by molten pitches impregnated in vacuum. Multiple cycles of liquid pitch impregnation and carbonization were carried out to obtain a desired density. The composites were characterized by density, microstructure. The inter-laminar shear strength (ILSS) test was performed for mechanical properties. For the new application, the microwave reflective proeprty of composites was investigated. Dielectric constant and permeability spectrum were measured in 12∼18 GHz frequency ranges. On the basis of the wave propagation theory in a lossy media, the reflection loss from the composite inter-layer was predict as a function of frequency.

촉매법으로 제조한 나노탄소섬유의 미세구조 및 전기적 특성 제어 연구

김명수,우원준,송희석,임연수,이재춘 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.4

Carbon nanofibers were prepared from the decomposition of various carbon-containing gases over pure Ni, pure Fe and their alloys with Cu. They yields, properties, and structure of carbon nanofibers obtained from the various reaction conditions were analyzed. Type of reacting gas, reaction temperature and catalyst composition were changed as the reaction variable. With Ni-Cu catalysts, the maximum yields of carbon nanofibers were obtained at temperatures between 550 and 650$^{\circ}C$ according to the reacting gas mixtures of C2H2-H2, C2H4-H2 and C3H8-H2, and the surface areas of the carbon nanofibers produced were 20∼350㎡/g. In the case of CO-H2 mixture, the rapid deposition of carbon nanofibers occurred with Fe-Cu catalyst and the maximum yield were obtained around 550$^{\circ}C$ with the range of surface areas of 140∼170㎡/g. The electrical resistivity of carbon nanofiber regarded as the key property of filler for the application of electromagnetic interference shielding was very sensitive to the type of reactant gas and the catalyst composition ranging 0.07∼1.5Ωcm at a pressure of 10000 psi, and the resistivity of carbon nanofibers produced over pure nickel catalyst were lower than those over alloy catalysts. SEM observation showed that the carbon nanofibers produced had the diameters ranging 20∼300 nm and the straight structure of carbon nanofibers changed into the twisted or helical conformation by the variation of reacting gas and catalyst composition.

다공성 탄소나노재료를 사용하는 Capacitive Deionization 공정의 염수 제거효과

양천모 ( Yang Cheon Mo ),최운혁 ( Choe Un Hyeog ),조병원 ( Jo Byeong Won ),조원일 ( Jo Won Il ),윤경석 ( Yun Gyeong Seog ),한학수 ( Han Hag Su ) 한국공업화학회 2004 공업화학 Vol.15 No.3

다공성 탄소재료를 이용하여 만든 전극을 사용해서 전기화학적으로 이온을 흡착시켜 제거시키는 capacitive deionization (CDI) 특성을 다공성 탄소재료의 종류에 따라서 조사하였다. CDI에 의한 담수화는 충전 시, 두 개의 다공성 탄소전극에 적절한 전압을 인가하고 그 사이로 이온들이 함유된 물을 흘려주어 양이온은 음극에, 음이온은 양극에 흡착되어 이온들이 서로 분리되고, 양이온과 음이온으로 포화된 탄소전극은 반대 전압을 인가하거나 탄소전극을 서로 연결(Short circuit)해주면 흡착된 이온들이 탈리되는 원리이다. 다공성 탄소 전극 재료로는 탄소에어로젤 (specific surface area : 950 ㎡/g, pore volume : 3.71 ㏄/g, pore diameter : 15.19 ㎚)과 활성탄소(BP-25: specific surface area 2500 ㎡/g, Kansai Coke & Chemicals Co. Ltd), 탄소나노튜브(MWNT type, 10~20 ㎚ diameter, ILJIN Nanotach), 그리고 탄소나노섬유(straight type, 130~150 ㎚ diameter, Nanomirae Co. Ltd)를 전극 활물질로 사용하여 침지법으로 CDI용 탄소전극을 각각 제조하였으며, 0.9 V 충전과 -0.001 V 방전, 휴기(rest) 과정을 1회로 하여 CDI 특성을 탄소전극 활물질의 종류에 따라 10회 동안 조사하였다. 충전과 방전 시 평균 전하량은 활성탄소를 이용한 전극에서 각각 0.229〔Aㆍmin〕와 0.143〔Aㆍmin〕으로 가장 높았으며, 활물질의 양을 고려한 평균 방전 비전하량의 경우, 전극 활물질로서 탄소에어로젤이 0.593〔Aㆍmin〕으로 가장 높게 나타났다. 10회 충-방전 싸이클에 대한 전하량 효율은 탄소에어로젤이 63.98%로 가장 우수하였으며, 활성탄소(62.45%)와 탄소나노섬유(56.50%)도 비교적 안정하게 나타났다. Capacitive deionization (CDI) process is a removal process of ions via electrochemical adsorption using porous carbon materials. The ions are adsorbed onto the surface of porous carbon electrodes by applying electric field to brackish water. Adsorbed ions are desorbed from the surface of the porous carbon electrdes by eliminating the field or reversing electric field, resulting in the regeneration of electrodes. Recently, carbon aerogel electrodes, one of the porous carbon materials, are bring used for CDI process. In this study, the electrode using carbon aerogel (specific surface area: 960m^(2)/g, pore volume: 3.71 cc/g, and pore diameter: 15.19 nm), activated carbon(BP-25: specific surface 2500m^(2)g, frpm Kansai Cole & Chemicals Co. Ltd), carbon nanotube (MMMT type, 10-20 nm diameter, from ILJIN Nanotech) and carbon nanofiber (straight type, 130∼150 nm diameter, from Nanomirae Co. Ltd) were fabricated by dip coating method. Porous carbon electrodes were charged at 0.9 V, discharged at -0.001 V, cycled 10 times, and their CDI performances were compared with CDI characteristics. An activated carbon electrode showed higher average charge and discharge coulombs than others and its average charge and discharges were 0.229 [Aㆍmin] and 0.143 [Aㆍmin], respectively. At the average discharge specific-coulombs, a carbon aerogel electrode had highest average specific discharge coulomb of 0.593 [(Aㆍmin)/g]. The values of coulombic-efficiencies showed 63.98% for the carbon aerogel electrode, 62.45% for the activated carbon, and 56.50% for the carbon nanofiber.

Fabrication and characterization of carbon nanofiberμesoporous carbon core-shell composite for the Li-air battery

Song, M.J.,Shin, M.W. New York] ; North-Holland 2014 APPLIED SURFACE SCIENCE - Vol.320 No.-

In this study, we successfully design and synthesize the mesoporous carbon coated carbon nanofibers (CNFμesoCs) for the Li-air battery. The composites are fabricated via electrospinning technique and nanocasting strategy. After mesoporous carbon coating process, the composites have retained their original one-dimensional structure as pristine carbon nanofibers. Every nanofiber entangles with each other to form a three-dimensional cross-linked web structure. Because of the mesoporous carbon coating on carbon nanofibers, the surface area increases from 708m<SUP>2</SUP>g<SUP>-1</SUP> to 2194m<SUP>2</SUP>g<SUP>-1</SUP>. We confirm that the mesoporous carbon coated on carbon nanofibers is well-graphitized by analysis of Raman spectra. The graphitized surface of CNFμesoCs (4.638Scm<SUP>-1</SUP>) is believed to result in their higher electrical conductivity than that of pristine carbon nanofibers (3.0759Scm<SUP>-1</SUP>). Without employment of any binders and metal foams, the cathode of CNFμesoCs exhibits high discharge capacity of 4000mAhg<SUP>-1</SUP>, which is much higher than that from pristine carbon nanofibers (2750mAhg<SUP>-1</SUP>). This work demonstrates that the fabricated CNFμesoCs structures have a great potential to be employed as light-weight and efficient electrode for energy storage and conversion devices.