• Title/Summary/Keyword: nanofibers

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Ni Nanoparticles-Graphitic Carbon Nanofiber Composites for Pt-Free Counter Electrode in Dye-Sensitized Solar Cells (염료감응 태양전지의 비백금 상대전극을 위한 니켈 나노입자-흑연질 탄소나노섬유 복합체)

  • Oh, Dong-Hyeun;Koo, Bon-Ryul;Lee, Yu-Jin;An, HyeLan;Ahn, Hyo-Jin
    • Korean Journal of Materials Research
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    • v.26 no.11
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    • pp.649-655
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    • 2016
  • Ni nanoparticles (NPs)-graphitic carbon nanofiber (GCNF) composites were fabricated using an electrospinning method. The amounts of Ni precursor used as catalyst for the catalytic graphitization were controlled at 0, 2, 5, and 8 wt% to improve the photovoltaic performances of the nanoparticles and make them suitable for use as counter electrodes for dye-sensitized solar cells (DSSCs). As a result, Ni NPs-GCNF composites that were fabricated with 8 wt% Ni precursors showed a high circuit voltage (0.73 V), high photocurrent density ($14.26mA/cm^2$), and superb power-conversion efficiency (6.72%) when compared to those characteristics of other samples. These performance improvements can be attributed to the reduced charge transport resistance that results from the synergetic effect of the superior catalytic activity of Ni NPs and the efficient charge transfer due to the formation of GCNF with high electrical conductivity. Thus, Ni NPs-GCNF composites may be used as promising counter electrodes in DSSCs.

Electrical Properties of PVdF/PVP Composite Filled with Carbon Nanotubes Prepared by Floating Catalyst Method

  • Kim, Woon-Soo;Song, Hee-Suk;Lee, Bang-One;Kwon, Kyung-Hee;Lim, Yun-Soo;Kim, Myung-Soo
    • Macromolecular Research
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    • v.10 no.5
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    • pp.253-258
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    • 2002
  • The multi-wall carbon nanotubes (MWNTs) with graphite crystal structure were synthesized by the catalytic decomposition of a ferrocene-xylene mixture in a quartz tube reactor to use as the conductive filler in the binary polymer matrix composed of poly(vinylidene fluoride) (PVdF) and poly(vinyl pyrrolidone) (PVP) for the EMI (electromagnetic interference) shielding applications. The yield of MWNTS was significantly dependent on the reaction temperature and the mole ratio of ferrocene to xylene, approaching to the maximum at 800 $^{\circ}C$ and 0.065 mole ratio. The electrical conductivity of the MWNTs-filled PVdF/PVP composite proportionally depended on the mass ratio of MWNTs to the binary polymer matrix, enhancing significantly from 0.56 to 26.7 S/cm with the raise of the mass ratio of MWNTs from 0.1 to 0.4. Based on the higher electrical conductivity and better EMI shielding effectiveness than the carbon nanofibers (CNFs)-filled coating materials, the MWNTs-filled binary polymer matrix showed a prospective possibility to apply to the EMI shielding materials. Moreover, the good adhesive strength confirmed that the binary polymer matrix could be used for improving the plastic properties of the EMI shielding materials.

Mineralogical Properties of Asian Dust in April 6 and 15, 2018, Korea (2018년 4월 6일과 15일 황사의 광물학적 특성)

  • Jeong, Gi Young
    • Journal of the Mineralogical Society of Korea
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    • v.31 no.2
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    • pp.103-111
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    • 2018
  • Mineralogical properties of two Asian dust (Hwangsa) samples collected during dust events in April 6 and 15, 2018 were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analyses showed that Asian dusts were dominated by phyllosilicates (62 wt%) comprising illite-smectite series clay minerals (ISCMs) (55%), chlorite (3%) and kaolinite (4%). Nonphyllosilicate minerals were quartz (18%), plagioclase (9%), K-feldspar (3%), calcite (3%), and gypsum (2-4%). Mineral compositions determined by SEM chemical analyses were consistent with XRD data. ISCMs occur as submicron grains forming aggregate particles or coating coarse mineral grains such as quartz, plagioclase, K-feldspar, chlorite, and calcite. The ISCMs are often associated with calcite nanofibers and gypsum blades. Mineralogical properties of 2018 dusts were similar to those of previous dusts although clay contents were higher than that of coarse 2012 dust.

Single-Particle Mineralogy and Mixing State of Asian Dust, Spring, 2009 (2009년 봄철 황사 단일 입자의 광물학 몇 혼합상태)

  • Jeong, Gi-Young;Choi, Ho-Jeong;Kwon, Seok-Ki
    • Journal of the Mineralogical Society of Korea
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    • v.24 no.3
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    • pp.225-234
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    • 2011
  • The mineralogy and mixing state were investigated by the high resolution scanning electron microscopy combined with energy-dispersive X-ray analysis on particles of the total suspended solid (TSP) samples collected during the Asian dust event, spring, 2009. Relatively large particles were dominated by quartz, plagioclase, K-feldspar, amphibole, biotite, muscovite, chlorite, and calcite. Clay minerals usually occur as thin coatings on the coarse minerals or as aggregates. Calcite nanofibers are often admixed with clay platelets in the clay coatings and aggregates. Dust particles were classified on the basis of their main minerals. The single-particle mineralogy and mixing state of the TSP sample are consistent with those of $PM_{10}$ samples in previous studies.

Spindle-shaped Fe2O3 Nanoparticle Coated Carbon Nanofiber Composites for Low-cost Dye-sensitized Solar Cells (저비용 염료감응 태양전지를 위한 방추형 Fe2O3 나노입자가 코팅된 탄소나노섬유 복합체)

  • Oh, Dong-Hyeun;An, HyeLan;Koo, Bon-Ryul;Ahn, Hyo-Jin
    • Journal of Powder Materials
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    • v.23 no.2
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    • pp.95-101
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    • 2016
  • Carbon nanofiber (CNF) composites coated with spindle-shaped $Fe_2O_3$ nanoparticles (NPs) are fabricated by a combination of an electrospinning method and a hydrothermal method, and their morphological, structural, and chemical properties are measured by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. For comparison, CNFs and spindle-shaped $Fe_2O_3$ NPs are prepared by either an electrospinning method or a hydrothermal method, respectively. Dye-sensitized solar cells (DSSCs) fabricated with the composites exhibit enhanced open circuit voltage (0.70 V), short-circuit current density ($12.82mA/cm^2$), fill factor (61.30%), and power conversion efficiency (5.52%) compared to those of the CNFs (0.66 V, $11.61mA/cm^2$, 51.96%, and 3.97%) and spindle-shaped $Fe_2O_3$ NPs (0.67 V, $11.45mA/cm^2$, 50.17%, and 3.86%). This performance improvement can be attributed to a synergistic effect of a superb catalytic reaction of spindle-shaped $Fe_2O_3$ NPs and efficient charge transfer relative to the one-dimensional nanostructure of the CNFs. Therefore, spindle-shaped $Fe_2O_3$-NP-coated CNF composites may be proposed as a potential alternative material for low-cost counter electrodes in DSSCs.

ZnO Hierarchical Nanostructures Fabricated by Electrospinning and Hydrothermal Methods for Photoelectrochemical Cell Electrodes (전기방사와 수열합성법으로 제작한 광전화학셀 전극용 나노 계층형 아연산화물 구조 연구)

  • Yi, Hwanpyo;Jung, Hyuck;Kim, Okkil;Kim, Hyojin;Kim, Dojin
    • Korean Journal of Materials Research
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    • v.23 no.11
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    • pp.655-660
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    • 2013
  • Photoelectrochemical cells have been used in photolysis of water to generate hydrogen as a clean energy source. A high efficiency electrode for photoelectrochemical cell systems was realized using a ZnO hierarchical nanostructure. A ZnO nanofiber mat structure was fabricated by electrospinning of Zn solution on the substrate, followed by oxidation; on this substrate, hydrothermal synthesis of ZnO nanorods on the ZnO nanofibers was carried out to form a ZnO hierarchical structure. The thickness of the nanofiber mat and the thermal annealing temperature were determined as the parameters for optimization. The morphology of the structures was examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The performance of the ZnO nanofiber mat and the potential of the ZnO hierarchical structures as photoelectrochemical cell electrodes were evaluated by measurement of the photoelectron conversion efficiencies under UV light. The highest photoconversion efficiency observed was 63 % with a ZnO hierarchical structure annealed at $400^{\circ}C$ in air. The morphology and the crystalline quality of the electrode materials greatly influenced the electrode performance. Therefore, the combination of the two fabrication methods, electrospinning and hydrothermal synthesis, was successfully applied to fabricate a high performance photoelectrochemical cell electrode.

Morphology Control of NiO Catalysts on NiCrAl Alloy Foam Using a Hydrothermal Method (수열합성법을 이용한 NiCrAl 합금 폼 위에 합성된 NiO 촉매 형상 제어)

  • Sin, Dong-Yo;Lee, Eun-Hwan;Park, Man-Ho;Ahn, Hyo-Jin
    • Korean Journal of Materials Research
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    • v.26 no.7
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    • pp.393-399
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    • 2016
  • Flower-like nickel oxide (NiO) catalysts were coated on NiCrAl alloy foam using a hydrothermal method. The structural, morphological, and chemical bonding properties of the NiO catalysts coated on the NiCrAl alloy foam were investigated by field-emission scanning electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, respectively. To obtain flower-like morphology of NiO catalysts on the NiCrAl alloy foam, we prepared three different levels of pH of the hydrothermal solution: pH-7.0, pH-10.0, and pH-11.5. The NiO morphology of the pH-7.0 and pH-10.0 samples exhibited a large size plate owing to the slow reaction of the hydroxide ($OH^-$) and nickel ions ($Ni^+$) in lower pH than pH-11.5. Flower-like NiO catalysts (${\sim}4.7{\mu}m-6.6{\mu}m$) were formed owing to the fast reaction of $OH^-$ and $Ni^{2+}$ by increased $OH^-$ concentration at high pH. Thus, the flower-like morphology of NiO catalysts on NiCrAl alloy foam depends strongly on the pH of the hydrothermal solution.

Drug Delivery System Using Electrospun Nanofiber Mats (전기방사된 나노파이버 매트를 이용한 약물전달시스템에 관한 연구)

  • Yoon, Hyeon;Park, Yoon-Kyung;Kim, Geun-Hyung
    • Polymer(Korea)
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    • v.33 no.3
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    • pp.219-223
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    • 2009
  • The nanofibers fabricated by using an electrohydrodynamic process has been used as various applications, such as nano-device, filtering system, protective clothes, wound dressing, and drug delivery system (DDS). Of these applications, the DDS should be needed to minimize side effects of drugs, maximize the properties of medicine, and efficiently deliver the required amount of drugs to the diseased area. In this paper, by using the electro spinning process, which is one of electrohydrodynamic processes, two different types, polycarprolactone and poly(ethylene oxide)/Rhodamine B, of electrospun mats were fabricated layer by layer and the release behavior of Rhodamine B was characterized with time. In addition, to show the feasibility of DDS of this type, we tested release behavior of a peptide of the nanofiber system, a PCL/(Peptide+PEO)/PCL nanofiber mat. The released peptide did not loss biological activities. From these results, we believe that the layered nanofiber mat as a DDS has enough function of a new drug delivery system.

Effect of Operating Conditions and Recovery of Water Back-washing in Spiral Wound Microfiltration Module Manufactured with PVDF Nanofibers for Water Treatment (수처리용 PVDF 나노섬유 나권형 정밀여과 모듈에서 운전조건의 영향과 물 역세척 회복)

  • Kyung, Kyu Myung;Park, Jin Yong
    • Membrane Journal
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    • v.25 no.2
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    • pp.180-190
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    • 2015
  • PVDF (polyvinylidene fluoride) nanofiber has the advantages such as excellent strength, chemical resistance, nontoxic, non-combustibility. Flat membranes with 0.3 and $0.4{\mu}m$ pore size respectively, were manufactured by PVDF nanofiber, and then each spiral wound module was prepared with them. A woven paper was not included in preparing the module with $0.3{\mu}m$ pore size; however, it was included the module with $0.4{\mu}m$ pore size. The permeate fluxes and rejection rates of the two modules were compared using pure water and simulation solution including kaolin and humic acid. The recovery rate and filtration resistance were calculated after water back-washing. In addition, the effect of flow rate and trans-membrane pressure on treatment efficiency and filtration resistance were investigated for the spiral wound module with $0.4{\mu}m$ pore size.

Formation of Uniform SnO2 Coating Layer on Carbon Nanofiber by Pretreatment in Atomic Layer Deposition (전처리를 이용한 탄소 나노 섬유의 균일한 SnO2 코팅막 형성)

  • Kim, Dong Ha;Riu, Doh-Hyung;Choi, Byung Joon
    • Journal of Powder Materials
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    • v.25 no.1
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    • pp.43-47
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    • 2018
  • Carbon nanofibers (CNF) are widely used as active agents for electrodes in Li-ion secondary battery cells, supercapacitors, and fuel cells. Nanoscale coatings on CNF electrodes can increase the output and lifespan of battery devices. Atomic layer deposition (ALD) can control the coating thickness at the nanoscale regardless of the shape, suitable for coating CNFs. However, because the CNF surface comprises stable C-C bonds, initiating homogeneous nuclear formation is difficult because of the lack of initial nucleation sites. This study introduces uniform nucleation site formation on CNF surfaces to promote a uniform $SnO_2$ layer. We pretreat the CNF surface by introducing $H_2O$ or $Al_2O_3$ (trimethylaluminum + $H_2O$) before the $SnO_2$ ALD process to form active sites on the CNF surface. Transmission electron microscopy and energy-dispersive spectroscopy both identify the $SnO_2$ layer morphology on the CNF. The $Al_2O_3$-pretreated sample shows a uniform $SnO_2$ layer, while island-type $SnO_x$ layers grow sparsely on the $H_2O$-pretreated or untreated CNF.