Deposition of Fe₃O₄ on oxidized activated carbon by hydrazine reducing method for high performance supercapacitor

Oh, Ilgeun,Kim, Myeongjin,Kim, Jooheon Elsevier 2015 Microelectronics and reliability Vol.55 No.1

<P><B>Abstract</B></P> <P>Oxidized activated carbon/Fe<SUB>3</SUB>O<SUB>4</SUB> (AC/Fe<SUB>3</SUB>O<SUB>4</SUB>) composites for supercapacitor electrodes were synthesized by a reduction method. Poly(vinylpyrrolidone) was added as a dispersing agent for homogeneous deposition of Fe<SUB>3</SUB>O<SUB>4</SUB> on AC. The obtained products were identified as AC/Fe<SUB>3</SUB>O<SUB>4</SUB> by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Morphological characterization of AC/Fe<SUB>3</SUB>O<SUB>4</SUB> was carried out by field emission scanning electron microscopy (FE-SEM); the results clearly showed the formation of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles about 30nm in diameter on AC. Moreover, by using N<SUB>2</SUB> adsorption/desorption isotherm analysis, we confirmed that surface areas and pore volumes decreased with increasing Fe<SUB>3</SUB>O<SUB>4</SUB> content. We also carried out electrochemical characterization of AC and AC/Fe<SUB>3</SUB>O<SUB>4</SUB> composites. Remarkably, we found that the value of specific capacitance increased significantly from 99.4Fg<SUP>−1</SUP> of raw AC to 202.6Fg<SUP>−1</SUP> of AC/Fe<SUB>3</SUB>O<SUB>4</SUB> composites at 10mVs<SUP>−1</SUP> of scan rate. This result can be ascribed to a synergistic effect of the combination of electrical double-layer capacitance and pseudo-capacitance properties. This research represents a valuable contribution to the application of supercapacitor electrodes in regard to cost effectiveness and simple fabrication.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nano-sized Fe<SUB>3</SUB>O<SUB>4</SUB> is formed on activated carbon surface as a hybrid material. </LI> <LI> Fe precursor was reduced to Fe<SUB>3</SUB>O<SUB>4</SUB> via chemical reduction by hydrazine method. </LI> <LI> Fe<SUB>3</SUB>O<SUB>4</SUB> contents in the composites optimized for electrochemical performance. </LI> <LI> Higher electrical performance than other carbon/Fe<SUB>3</SUB>O<SUB>4</SUB> composite electrodes. </LI> <LI> Fe<SUB>3</SUB>O<SUB>4</SUB> and activated carbon is cost effective and eco-friendly materials. </LI> </UL> </P>

Aggregation multigrid method for schur complement system in FE analysis of continuum elements

Ko, Jin-Hwan,Lee, Byung Chai Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.4

An aggregation multigrid method (AMM) is a leading iterative solver in solid mechanics. Recently, AMM is applied for solving Schur Complement system in the FE analysis of shell structures. In this work, an extended application of AMM for solving Schur Complement system in the FE analysis of continuum elements is presented. Further, the performance of the proposed AMM in multiple load cases, which is a challenging problem for an iterative solver, is studied. The proposed method is developed by combining the substructuring and the multigrid methods. The substructuring method avoids factorizing the full-size matrix of an original system and the multigrid method gives near-optimal convergence. This method is demonstrated for the FE analysis of several elastostatic problems. The numerical results show better performance by the proposed method as compared to the preconditioned conjugate gradient method. The smaller computational cost for the iterative procedure of the proposed method gives a good alternative to a direct solver in large systems with multiple load cases.

Aggregation multigrid method for schur complement system in FE analysis of continuum elements

Jin Hwan Ko,이병채 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.4

An aggregation multigrid method (AMM) is a leading iterative solver in solid mechanics. Recently, AMM is applied for solving Schur Complement system in the FE analysis of shell structures. In this work, an extended application of AMM for solving Schur Complement system in the FE analysis of continuum elements is presented. Further, the performance of the proposed AMM in multiple load cases, which is a challenging problem for an iterative solver, is studied. The proposed method is developed by combining the substructuring and the multigrid methods. The substructuring method avoids factorizing the full-size matrix of an original system and the multigrid method gives near-optimal convergence. This method is demonstrated for the FE analysis of several elastostatic problems. The numerical results show better performance by the proposed method as compared to the preconditioned conjugate gradient method. The smaller computational cost for the iterative procedure of the proposed method gives a good alternative to a direct solver in large systems with multiple load cases.

Fe₄N 나노분말과 Fe₁₇Sm₂N<SUB>x</SUB> 자성분말의 자기적 특성

오영우(Young Woo Oh),이정구(Jung Goo Lee),박상준(Sang Jun Park) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.3

Nano-magnetic materials such as iron-nitrides have been actively studied as an alternative to the application of high density, high performance needs for next generation information storage and also alternative to the rare earth and neodymium magnet. Fe₄N is the basic materials for magnetic storage media and is one of the important magnetic materials in focus because of its higher magnetic recording density and chemical stability. Single phase γ’-Fe₄N nanoparticles have been prepared by a PAD (Plasma Arc Discharge) method and nitriding in a NH₃-H₂ mixed gases at temperature, 400 ℃ for 4 hrs. Also Fe₁?Sm₂N<SUB>x</SUB> powders were synthesized by nitriding after reduction/diffusion of Fe₁?Sm₂ to compare the magnetic properties with nano-sized Fe₄N particles. The saturation magnetization of Fe₄N and Fe₁?Sm₂N<SUB>x</SUB> were 149 and 117 emu/g, respectively, but the coercive force was considerably smaller than that of bulk or acicular Fe₄N.

Fe/BEA 제올라이트 촉매의 N₂O/NO 동시 환원 반응에서 금속 담지 방법이 촉매 활성에 미치는 영향

전민욱,이승재,유인수,문승현,이영우,전상구,Jeon, Min-Wook,Lee, Seung-Jae,Ryu, In-Soo,Moon, Seung-Hyun,Rhee, Young Woo,Jeon, Sang Goo 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.5

Fe/BEA 제올라이트 촉매의 $N_2O/NO$ 동시 환원반응에서 Fe이온을 담지하는 방법이 촉매의 활성에 미치는 영향을 고찰하였다. Fe/BEA 제올라이트 촉매는 함침법과 이온교환법으로 제조되었으며, 제조된 촉매의 성능을 확인하기 위하여 암모니아를 환원제로 사용하는 선택적 촉매 환원 반응을 실시하였다. 그 결과 이온교환 촉매는 함침 촉매보다 높은 NO 및 $N_2O$ 전환율을 나타내었다. 이러한 촉매 활성의 차이를 규명하기 위하여 XRD, $H_2-TPR$, $O_2-TPD$, XPS와 같은 촉매 특성 분석들이 수행되었다. 이온교환 촉매의 활성 증가는 향상된 환원 특성 및 증가된 산소 탈착 속도에 기인한 것으로 판단되며, 이온교환 촉매 제조시 촉매 활성과 관련이 있는 $Fe^{2+}$가 함침 촉매에 비해 약 1.6배 이상 형성되는 것을 XPS 분석을 통하여 확인하였다. The influence of catalytic activity on Fe loading methods over Fe/BEA zeolite catalyst in the simultaneous reduction of $N_2O/NO$ has been studied. The Fe/BEA zeolite catalysts were prepared by ion exchange and impregnation. Catalytic tests were carried out in the selective catalytic reduction using ammonia as a reductant to identify the activity of prepared catalysts. The results show that the ion exchanged catalyst exhibited higher NO and $N_2O$ conversions than the impregnated catalysts did. To investigate the difference in catalytic activity, we performed various analyses such as XRD, $H_2-TPR$, $O_2-TPD$ and XPS. It is considered that the increase in the activity of the ion exchange catalyst is due to improved reducibility and increased oxygen desorption rate. In addition, the ion exchange catalyst was found through the XPS analysis that $Fe^{2+}$, which is related to the catalytic activity, is formed about 1.6 times more than the impregnated catalyst.

마이크로에멀젼법을 이용하여 실리카 코팅된 나노 Fe₃O₄ 분말의 합성과 분석연구

유리,김유진,피재환,황광택,양희승,김경자,Yu, Ri,Kim, Yoo-Jin,Pee, Jae-Hwan,Hwang, Kwang-Taek,Yang, Hee-Seung,Kim, Kyung-Ja 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.2

The silica coated $Fe_3O_4$ nanoparticles have been synthesized using a micro-emulsion method. The $Fe_3O_4$ nanoparticles with the sizes 6 nm in diameter were synthesized by thermal decomposition method. Hydrophobic $Fe_3O_4$ nanoparticles were coated silica using surfactant and tetraethyl orthosilicated (TEOS) as a $SiO_2$ precursor. Shell thickness of silica coated $Fe_3O_4$ can be controlled (11~20 nm) through our synthetic conditions. The $Fe_3O_4$ and silica coated $Fe_3O_4$ nano powders were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD) and vortex magnetic separation (VMS).

Effect of Heat-treatment Temperature on the Formation of ε-Fe2O3 Nanoparticles Encapsulated by SiO2

Trinh Nguyen Thi,Phuoc Cao Van,Kirakosyan Artavazd,Chanyong Hwang,Jihoon Choi,Hyojin Kim,Jong-Ryul Jeong 한국자기학회 2023 Journal of Magnetics Vol.28 No.3

ε-Fe2O3 has received attention with particular interest because of its large coercive field at room temperature, high-frequency millimeter-wave absorption, and the coupling of its magnetic and dielectric properties. This work investigated the effect of heat treatment on the formation of ε-Fe2O3/SiO2 composites fabricated using reverse-micelle and sol-gel methods. The heating process was performed at various temperatures to figure out the optimal conditions for acquisition of the ε-Fe2O3 phase, which exhibits the largest coercive field among the Fe oxides. The sample treated at 1,075 °C had the highest percentage of ε-Fe2O3 phase, with a coercivity (HC) of 21.57 kOe measured at room temperature that reached a maximum of 23.7 kOe at 230 K. The measurement of the magnetization-temperature (M-T) curve for this sample also reveals the characteristic magnetic transition associated with ε-Fe2O3 within the temperature range of 40-150 K. The crystal structure of ε-Fe2O3 was confirmed using X-ray powder diffraction. Transmission electron micrographs revealed a broad size distribution of iron oxide nanoparticles ranging from 12 to 22 nm. The findings indicate that ε-Fe2O3 is a promising candidate with high electromagnetic-wave absorption capacity that is appropriate for high-speed wireless communication applications.

마이크로에멀젼법을 이용하여 실리카 코팅된 나노 Fe3O4 분말의 합성과 분석연구

유리,김유진,피재환,황광택,양희승,김경자 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.2

The silica coated Fe3O4 nanoparticles have been synthesized using a micro-emulsion method. The Fe3O4 nanoparticles with the sizes 6 nm in diameter were synthesized by thermal decomposition method. Hydrophobic Fe3O4 nanoparticles were coated silica using surfactant and tetraethyl orthosilicated (TEOS) as a SiO2 precursor. Shell thickness of silica coated Fe3O4 can be controlled (11~20 nm) through our synthetic conditions. The Fe3O4 and silica coated Fe3O4 nano powders were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD) and vortex magnetic separation (VMS).

Sol-Gel 방법을 이용하여 제작된 Pt이 첨가된 Fe₂O₃ 나노 입자의 가스 감지 특성

장민형,임유성,최승일,박지인,황남경,이문석,Jang, Min-Hyung,Lim, Yooseong,Choi, Seung-Il,Park, Ji-In,Hwang, Namgyung,Yi, Moonsuk 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.5

$Fe_2O_3$ is one of the most important metal oxides for gas sensing applications because of its low cost and high stability. It is well-known that the shape, size, and phase of $Fe_2O_3$ have a significant influence on its sensing properties. Many reports are available in the literature on the use of $Fe_2O_3$-based sensors for detecting gases, such as $NO_2$, $NH_3$, $H_2S$, $H_2$, and CO. In this paper, we investigated the gas-sensing performance of a Pt-doped ${\varepsilon}$-phase $Fe_2O_3$ gas sensor. Pt-doped $Fe_2O_3$ nanoparticles were synthesized by a Sol-Gel method. Platinum, known as a catalytic material, was used for improving gas-sensing performance in this research. The gas-response measurement at $300^{\circ}C$ showed that $Fe_2O_3$ gas sensors doped with 3%Pt are selective for $NO_2$ gas and exhibita maximum response of 21.23%. The gas-sensing properties proved that $Fe_2O_3$ could be used as a gas sensor for nitrogen dioxide.

For high performance supercapacitor, deposition of Fe₃O₄ on oxidezed acitivated carbon using hydrazine reducing method

최재호,김명진,김기호,유석규,김주헌 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Oxidized activated carbon/Fe₃O₄ (AC/Fe₃O₄) composites for supercapacitor electrodes were synthesized by a reduction method. Poly(vinylpyrrolidone) was added as a dispersing agent for homogeneous deposition of Fe₃O₄ on AC. By using N₂ adsorption/desorption isotherm analysis, we confirmed that surface areas and pore volumes decreased with increasing Fe₃O₄ content. We also carried out electrochemical characterization of AC and AC/Fe₃O₄ composites. Remarkably, we found that the value of specific capacitance increased significantly from 99.4 F g^-1 of raw AC to 202.6 F g^-1 of AC/Fe₃O₄ composites at 10 mV s^-1 of scan rate. This result can be ascribed to a synergistic effect of the combination of electrical double-layer capacitance and pseudo-capacitance properties. This research represents a valuable contribution to the application of supercapacitor electrodes in regard to cost effectiveness and simple fabrication.