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활성화 및 에어로졸 공정에 의한 다공성 그래핀 볼 제조 및 슈퍼커패시터 응용
이총민,장한권,장희동,Lee, Chongmin,Chang, Hankwon,Jang, Hee Dong 한국입자에어로졸학회 2019 Particle and Aerosol Research Vol.15 No.4
Here, we introduce porous graphene balls (PGB) showing superior electrochemical properties as supercapacitor electrode materials. PGB was fabricated via activation of graphene oxides (GO) by H<sub>2</sub>O<sub>2</sub> and aerosol spray drying in series. Effect of activation on the morphology, specific surface area, pore volume, and electrochemical properties were investigated. As-prepared PGB showed spherical morphology containing pores, which lead to the effective prevention of restacking in graphene sheets. It also exhibited a large surface area, unique porous structures, and high electrical conductivity. The electrochemical properties of the PGB as electrode materials of supercapacitor are investigated by using aqueous KOH under symmetric two-electrode system. The highest specific capacitance of PGB was 279 F/g at 0.1 A/g. In addition, the high rate capability (93.8% retention) and long-term cycling stability (92.2%) of the PGB were found due to the facilitated ion mobility between the porous graphene layers.
이총민,장한권,장희동,Lee, Chongmin,Chang, Hankwon,Jang, Hee Dong 한국입자에어로졸학회 2017 Particle and Aerosol Research Vol.13 No.4
Potassium hexatitanate ($K_2Ti_6O_{13}$) with high thermal insulating capacity, good mechanical properties, and excellent chemical stability are promising functional materials in the field of reinforcing material, heat insulating paints and automotive brake linings. In this study, we successfully synthesized rod-shaped potassium hexatitanate ($K_2Ti_6O_{13}$) by aerosol spray drying and post heat treatment as an eco-friendly process. The $KHCO_3-TiO_2$ porous particles were firstly synthesized from a colloidal mixture of $K_2CO_3$ and $TiO_2$ via aerosol spray drying. Size of $KHCO_3-TiO_2$ porous particles was ranged from $1{\mu}m$ to $5{\mu}m$. The porous particles were then heated to fabricate rod-type $K_2Ti_6O_{13}$. The length and width of rod-type composites were affected by temperature and heating time. The length and width of $K_2Ti_6O_{13}$ were increased by 830 nm and 500 nm, respectively, as the reaction temperature and time increased.
에어로졸 분무열분해법을 이용한 코발트페라이트-그래핀 복합체 분말 제조 및 슈퍼커패시터 응용
이총민,장한권,장희동,Lee, Chongmin,Chang, Hankwon,Jang, Hee Dong 한국입자에어로졸학회 2017 Particle and Aerosol Research Vol.13 No.1
Cobalt-iron oxides have emerged as alternative electrode materials for supercapacitors because they have advantages of low cost, natural abundance, and environmental friendliness. Graphene loaded with cobalt ferrite ($CoFe_2O_4$) nanoparticles can exhibit enhanced specific capacitance. In this study, we present three-dimensional (3D) crumpled graphene (CGR) decorated with $CoFe_2O_4$ nanoparticles. The $CoFe_2O_4$-graphene composites were synthesized from a colloidal mixture of GO, iron (III) chloride hexahydrate ($FeCl_3{\cdot}6H_2O$) and cobalt chloride hexahydrate ($CoCl_2{\cdot}6H_2O$) respectively, via one step aerosol spray pyrolysis. Size of $CoFe_2O_4$ nanoparticles was ranged from 5 nm to 10 nm when loaded onto 500 nm CGR. The electrochemical performance of the $CoFe_2O_4$-graphene composites was examined. The $CoFe_2O_4$-graphene composite electrode showed the specific capacitance of $253F\;g^{-1}$.
코어-쉘 구조의 산화철/그래핀 복합체 제조 및 슈퍼커패시터 응용
이총민,장한권,장희동,Lee, Chongmin,Chang, Hankwon,Jang, Hee Dong 한국입자에어로졸학회 2018 Particle and Aerosol Research Vol.14 No.3
Core-shell structured $Fe_3O_4/graphene$ composites were synthesized by aerosol spray drying process from a colloidal mixture of graphene oxides and $Fe_3O_4$ nanoparticles. The structural and electrochemical performance of $Fe_3O_4/graphene$ were characterized by the field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, cyclic voltammetry, and galvanometric discharge-charge method. Core-shell structured $Fe_3O_4/GR$ composites were synthesized in different mass ratios of $Fe_3O_4$ and graphene oxide. The composite particles were around $3{\mu}m$ in size. $Fe_3O_4$ nanoparticles were encapsulated with a graphene. Morphology of the $Fe_3O_4/graphene$ composite particles changed from a spherical ball having a relatively smooth surface to a porous crumpled paper ball as the content of GO increased in the composites. The $Fe_3O_4/GR$ composite fabricated at the weight ratio of 1:4 ($Fe_3O_4:GO$) exhibited higher specific capacitance($203F\;g^{-1}$) and electrical conductivity than as-fabricated $Fe_3O_4/GR$ composite.
봉상형 육티탄산칼륨(K<sub>2</sub>Ti<sub>6</sub>O<sub>13</sub>) 제조 및 형상제어
이총민,장한권,장희동,Lee, Chongmin,Chang, Hankwon,Jang, Hee Dong 한국입자에어로졸학회 2018 Particle and Aerosol Research Vol.14 No.4
Rod shaped Potassium hexatitanate ($K_2Ti_6O_{13}$) was synthesized from colloidal mixture of $TiO_2$, KOH and graphene oxide (GO) by aerosol spray drying and post heat treatment. Firstly, $TiO_2-KOH-GO$ composites were fabricated by aerosol spray drying in argon atmosphere. The composites were then calcined to form a rod shaped morphology of potassium titanate (KTO) in the presence of graphene at $900^{\circ}C$ for 3 h in argon atmosphere. Finally, the rod shaped KTO was obtained after removal of graphene (GR) at $800^{\circ}C$ and 3 h in air atmosphere. Characterization of the synthesized $K_2Ti_6O_{13}$ was carried out using the XRD, BET and FE-SEM. The length and diameter of the synthesized $K_2Ti_6O_{13}$ could be controlled by weight fraction of GO in the aerosol precursor. The length of $K_2Ti_6O_{13}$ rod increased with decreasing its diameter as GO concentration increased. The aspect ratio of the synthesized $K_2Ti_6O_{13}$ rod was controlled from 5 to 13.
에어로졸 공정을 이용한 오산화바나듐(V<sub>2</sub>O<sub>5</sub>)-그래핀 복합체 제조 및 슈퍼커패시터 응용
이총민,장희동,Lee, Chongmin,Jang, Hee Dong 한국입자에어로졸학회 2020 Particle and Aerosol Research Vol.16 No.4
Vanadium Pentoxide (V2O5) has been emerged as alternative electrode materials for supercapacitors due to their low cost, natural abundance, and environmental friendliness. Graphene (GR) loaded with V2O5 can exhibit enhanced specific capacitance. In this study, we present three-dimensional (3D) crumpled graphene (CGR) decorated with V2O5. The V2O5-graphene composites were synthesized from a colloidal mixture of graphene oxide (GO) and Ammonium metavanadate (NH4VO3), via aerosol spray drying and post heat treatment process. The average size of composite was ranged from 1.82 to 4.6 ㎛. Morphology of the composite changed from a crumpled paper ball to spherical ball having relatively smooth surface as the content of V2O5 increased in the composites. The electrochemical performance of the V2O5-graphene composites was examined. The V2O5-graphene composite electrode showed the specific capacitance of 312 F/g. In addition, the device possessed acceptable cyclic stability, with 84% after 2000 cycles at 2 A/g. These outstanding properties are expected to make the composites prepared in this study as promising electrode materials for supercapacitor applications.
유기 주형 입자를 이용한 소디움 실리케이트로부터 중공형 실리카 입자 제조
이총민 ( Chong Min Lee ),김지웅 ( Ji Woong Kim ),장한권 ( Han Kwon Chang ),노기민 ( Ki Min Roh ),장희동 ( Hee Dong Jang ) 한국화학공학회 2015 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.53 No.1
유기주형(organic template) 입자를 이용하여 소디움실리케이트(sodium silicate)로부터 중공형 실리카(hollow silica)입자를 제조하였다. 유기주형 입자로는 스티렌 단량체(styrene monomer)로부터 분산중합(dispersion polymerization)에 의해 제조된 폴리스티렌 라텍스(polystyrene latex, PSL) 입자를 사용하였다. 유기주형 입자 제조 시 중합개시제인 2,2``-azobisisobutyronitrile(AIBN)의 주입량을 조절하여 1~3 um의 크기를 가진 입자를 제조하였다. 생성된 유기주형 입자표면에 졸-겔(sol-gel)법에 의해 소디움실리케이트로부터 생성된 실리카(SiO2) 나노 입자를 코팅하여 PSL/SiO2 코어-쉘형태의 입자를 제조하였다. 유기용매인 테트라하이드로푸란(tetrahydrofuran, THF)을 이용하여 코어-쉘 입자 내부의 유기주형을 제거 하였다. 코어-쉘 입자 제조 시 용매의 종류 및 pH의 변화에 따라 생성되는 중공형 실리카 입자의 형상을 조사하였다. PSL/SiO2 코어-쉘 입자 제조 시 용매를 에탄올에서 물로 변경했을 때 중공형 실리카 입자가 성공적으로 제조되었으며 낮은 pH 값을 갖는 용매에서 쉘 두께가 균일한 중공형 실리카 입자가 형성되었다. 중공형 실리카 입자의 반사도를 측정한 결과 상용 제품(Insuladd)보다 높은 반사 특성을 보여주었다. Hollow silica particles were prepared using sodium silicate and organic templates. Polystyrene latex (PSL) particles produced by dispersion polymerization were used as organic templates. PSL particles ranged from 1 um to 3 um in diameter were synthesized by adjusting the amount of 2,2`-azobisisobutyronitrile (AIBN). The PSL/SiO2 core-shell particles were prepared by coating of silica nanoparticles originated from sodium silicate using sol-gel method. The organic templates were removed by the organic solvent, tetrahydrofuran (THF). Morphology of hollow silica particles was investigated with respect to types of the reaction medium and pH during the process. By changing the solvent from ethanol to water, hollow silica particles were successfully formed. Hollow silica particles with the uniform shell thickness were produced at low pH as well. The reflectivity of the as-prepared silica particles was measured in the range of the wavelength of UV and visible light. Hollow silica particles showed much better reflective properties than the commercial light reflector, Insuladd.
분무열분해 공정에 의한 규산수용액으로부터 다양한 미세기공을 갖는 실리카 나노다공체 제조
김선경,이총민,장한권,장희동,Kim, Sun Kyung,Lee, Chongmin,Chang, Hankwon,Jang, Hee Dong 한국입자에어로졸학회 2016 Particle and Aerosol Research Vol.12 No.3
Nanoporous $SiO_2$ particles containing different pore volume and size were prepared from silicic acid by a spray pyrolysis. The pore size, pore volume and particle size could be controlled with varying the precursor concentration, reaction temperature, and amount of organic templates such as Urea and poly ethylene glycol (PEG). The pore size distribution, pore volume and specific surface area of as-prepared particles were analyzed by BET and BJH methods, and the average particle sizes were measured by a laser diffraction method. The nanoporous $SiO_2$ particles ranged $0.6-0.9{\mu}m$ in diameter were successfully synthesized and the average particle size increased as the silicic acid concentration increased. The morphology of nanoporous $SiO_2$ particles was spherical and pores ranged 1 - 40 nm in diameter were measured in the particles. In case of Urea added into silicic acid, it showed no much difference in the morphology, pore size and pore volume at different Urea concentration. On the other hand, when PEG was added, it was clearly observed that pore diameter and pore volume of the particles surface increased with respect to PEG concentration.
에어로졸 공정에 의한 Multiwall carbon nanotube/Graphene 복합체 제조 및 슈퍼커패시터 특성평가
조은희,김선경,장한권,이총민,박수련,최지혁,장희동,Jo, Eun Hee,Kim, Sun Kyung,Chang, Hankwon,Lee, Chong Min,Park, Su-Ryeon,Choi, Ji-hyuk,Jang, Hee Dong 한국입자에어로졸학회 2016 Particle and Aerosol Research Vol.12 No.4
A multiwall carbon nanotube (MWCNT)/graphene (GR) composite was synthesized for an enhanced supercapacitor. Aerosol spray pyrolysis (ASP) was employed to synthesize the MWCNT/GR composites using a colloidal mixture of MWCNT and graphene oxide (GO). The effect of the weight ratio of the MWCNT/GO on the particle properties including the morphology and layered structure were investigated. The morphology of MWCNT/GR composites was generally the shape of a crumpled paper ball, and the average composite size was about $5{\mu}m$. MWCNT were uniformly dispersed in GR sheets and the MWCNT not only increase the basal spacing but also bridge the defects for electron transfer between GR sheets. Thus, it was increasing electrolyte/electrode contact area and facilitating transportation of electrolyte ion and electron in the electrode. Electrochemical data demonstrate that the MWCNT/GR (weight ratio=0.1) composite possesses a specific capacitance of 192 F/g at 0.1 A/g and good rate capability (88% capacity retention at 4 A/g) using two-electrode testing system.