• Title/Summary/Keyword: Hollow carbon spheres

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Synthesis of Hollow Carbon Spheres with Various Diameters and Their Lithium Storage Properties (다양한 직경의 속이 빈 탄소구체의 제조 및 리튬 저장 특성)

  • Seulgi Shin;Hyeokrae Cho;Yong-Jae Jung;Sang-Mo Koo;Jong-Min Oh;Weon Ho Shin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.36 no.1
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    • pp.10-15
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    • 2023
  • The carbonaceous materials have attracted much attention for utilization of anode materials for lithium-ion batteries. Among them, hollow carbon spheres have great advantages (high specific capacity and good rate capability) to replace currently used graphite anode materials, due to their unique features such as high surface areas, high electrical conductivities, and outstanding chemical and thermal stability. Herein, we have synthesized various sizes of hollow carbon spheres by a facile hardtemplate method and investigated the anode properties for lithium-ion batteries. The obtained hollow carbon spheres have uniform diameters of 350 ~ 600 nm by varying the template condition, and they do not have any cracks after the optimization of the process. Increasing the diameter of hollow carbon spheres decreases their specific capacities, since the larger hollow carbon spheres have more useless spaces inside that could have a disadvantage for lithium storage. The hollow carbon spheres have outstanding rate and cyclic performance, which is originated from the high surface area and high electrical properties of the hollow carbon spheres. Therefore, hollow carbon spheres with smaller diameters are expected to have higher specific capacities, and the noble channel structures through various doping approaches can give the great possibility of high lithium storage properties.

Synthesis of Hollow Mesoporous Carbon Nitride Spheres Using Polystyrene Spheres as Template (폴리스티렌 구형입자를 주형으로 이용한 할로우 메조포러스 질화탄소 구형입자의 합성)

  • Park, Sung Soo;Ha, Chang-Sik
    • Journal of Adhesion and Interface
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    • v.15 no.2
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    • pp.63-68
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    • 2014
  • Hollow mesoporous carbon nitride material with sphere shape was synthesized using polystyrene sphere as template and cyanamide as nitrogen and carbon atom sources via thermal treatment process. The process of the silica removal is not necessary because silica as template is not in use for the synthesis of hollow mesoporous carbon nitride material and any solvents are also not in use. The size of polystyrene spheres was about 170 nm. Hollow diameter and wall thickness were 82 nm and 13 nm, respectively, in hollow mesoporous carbon nitride sphere. Surface area, mesopore size and pore volume of hollow mesoporous carbon nitride material was $188m^2g^{-1}$, 3.8 nm and $0.35cm^3g^{-1}$, respectively. The wall in hollow sphere has graphitic structure. Hollow mesoporous carbon nitride material has potential applications in the area of fuel cell, catalysis, photocatalysis, electroemmision device, etc.

Highly Sensitive and Fast-Responding Ethanol Sensor using Au Doped-In2O3 Hollow Spheres

  • Seong-Young Jeong
    • Journal of Sensor Science and Technology
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    • v.33 no.5
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    • pp.242-247
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    • 2024
  • Pure and 0.3 wt% Au-doped In2O3 hollow spheres were synthesized via ultrasonic spray pyrolysis of droplets containing an In-source and sucrose in air and their gas sensing characteristics to 1 ppm ethanol, 1 ppm toluene, 1 ppm xylene, 2 ppm nitrogen dioxide (NO2), and 30 ppm carbon monoxide (CO) were measured at 400 - 450℃. The pure In2O3 hollow spheres exhibited relatively low gas responses and sluggish recovery kinetics. In contrast, the doping of Au into In2O3 hollow spheres significantly increased the gas response (S= resistance ratio) to 1 ppm ethanol (S= 20.6) at 400℃ with low cross-responses (S = 1.3-8.8) to other interference gases. Furthermore, the hollow spherical morphology of In2O3 provides a large surface area and facilitates rapid gas diffusion, resulting in fast response and recovery times. The sensor exhibited excellent performance with a low detection limit of 1.6 ppb. These findings indicate that the Au-In2O3 hollow spheres are promising candidates for advanced ethanol-sensing applications, particularly in breath-alcohol monitoring for ignition interlock devices.

Ni Nanoparticles-hollow Carbon Spheres Hybrids for Their Enhanced Room Temperature Hydrogen Storage Performance

  • Kim, Jin-Ho;Han, Kyu-Sung
    • Journal of Hydrogen and New Energy
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    • v.24 no.6
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    • pp.550-557
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    • 2013
  • A glucose hydrothermal method is described for preparing hollow carbon spheres (HCS), which have a regular morphology and a high Brunauer-Emmett-Teller surface area of 28.6 m2/g. Scanning electron microscopy shows that they have thin shells and diameter between 2 and 8 ${\mu}m$. The HCSs were modified for the enhanced room temperature hydrogen storage by employing Ni nanoparticles on their surface. The Ni-decorated HCSs were characterized by X-ray diffraction, transmission electron microscopy coupled with an energy dispersive spectroscope, and an inductively coupled plasma spectrometer, indicating that fine and well-distributed Ni nanoparticles can be accomplished on the HCSs. The hydrogen uptake capacity in HCSs with and without Ni loading was evaluated using a high-pressure microbalance at room temperature under a hydrogen pressure upto 9 MPa. As much as 1.23wt.% of hydrogen can be stored when uniformly distributed Ni nanoparticles are formed on the HCSs, while the hydrogen uptake capacity of as-received HCSs was 0.41 wt.%. For Ni nanoparticle-loaded HCSs, hydrogen molecules could be easily dissociated into atomic hydrogen and then chemically adsorbed by the sorbents, leading to an enhanced capacity for storing hydrogen.

Electrochemical Properties of Using MnO2-HCS Composite for Supercapacitor (MnO2-HCS 복합체를 이용한 슈퍼커패시터의 전기화학적 특성)

  • Jin, En Mei;Jeong, Sang Mun
    • Clean Technology
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    • v.24 no.3
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    • pp.183-189
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    • 2018
  • Hollow carbon spheres (HCS) and carbon spheres (CS) were prepared by a hydrothermal reaction and they were introduced as a substrate for the deposition of $MnO_2$ nanoparticles. The $MnO_2$ nanoparticles were deposited on the carbon surface by a chemical redox deposition method. After deposition, the $MnO_2$ nanoparticles were uniformally distributed on the carbon surface in a slit-shape, and sparse $MnO_2$ slits appeared on the HCS surface. The $MnO_2-HCS$ showed an initial specific capacitance of $164.1F\;g^{-1}$ at scan rate of $20mv\;s^{-1}$, and after 1,000 cycles, the specific capacitance was maintained to $141.3F\;g^{-1}$. The capacity retention of $MnO_2-HCS$ and $MnO_2-CS$ were calculated to 86% and 78% in the cycle performance test up to 1,000 cycles, respectively. $MnO_2-HCS$ showed a good cycle stability due to the mesoporous hollow structure which can cause a faster diffusion of the electrolyte and can easily adsorb and desorb $Na^+$ ions on the surface of the electrode.

Effect of Hollow Sphere Size on Heat Shield Properties of hollow TiO2/polyacrylate Composites (중공구의 크기에 의한 hollow TiO2/polyacrylate 복합체의 열차단 특성)

  • Kim, Jong Seok
    • Applied Chemistry for Engineering
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    • v.32 no.6
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    • pp.690-694
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    • 2021
  • Carbon spheres (CS) were fabricated using glucose as a precursor in the hydrothermal method. Hollow TiO2 (H-TiO2) spheres with 200 nm, 500 nm, and 1,200 nm were synthesized by CS/TiO2 core-shell particles via a sol-gel and calcination method. H-TiO2 spheres with nano and micron sizes were characterized using FE-SEM, HR-TEM, and X-ray diffraction. The CIE color coordinate, solar reflectance, and heat shield temperatures of H-TiO2/polyacrylate (PA) composite film were investigated using a UV-Vis-NIR spectrometer and homemade heat insulation temperature measuring device. H-TiO2/PA composites exhibit excellent thermal insulation since the hollow structure filled with dry air has low thermal conductivity and near infrared light reflecting performance. The thermal insulation increased with increasing the hollow sphere (HS) size on H-TiO2/PA composites. The PA composite film mixed with H-TiO2 filled with 1200 nm HS reduced the heat shield temperature by 26 ℃ compared to that of the transparent glass counterpart.

Microstructural changes of polyacrylonitrile-based carbon fibers (T300 and T700) due to isothermal oxidation (1): focusing on morphological changes using scanning electron microscopy

  • Oh, Seong-Moon;Lee, Sang-Min;Kang, Dong-Su;Roh, Jae-Seung
    • Carbon letters
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    • v.18
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    • pp.18-23
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    • 2016
  • Polyacrylonitrile (PAN)-based carbon fibers have high specific strength, elastic modulus, thermal resistance, and thermal conductivity. Due to these properties, they have been increasingly widely used in various spheres including leisure, aviation, aerospace, military, and energy applications. However, if exposed to air at high temperatures, they are oxidized, thus weakening the properties of carbon fibers and carbon composite materials. As such, it is important to understand the oxidation reactions of carbon fibers, which are often used as a reinforcement for composite materials. PAN-based carbon fibers T300 and T700 were isothermally oxidized in air, and microstructural changes caused by oxidation reactions were examined. The results showed a decrease in the rate of oxidation with increasing burn-off for both T300 and T700 fibers. The rate of oxidation of T300 fibers was two times faster than that of T700 fibers. The diameter of T700 fibers decreased linearly with increasing burn-off. The diameter of T300 also decreased with increasing burn-off but at slower rates over time. Cross-sectional observations after oxidation reactions revealed hollow cores in the longitudinal direction for both T300 and T700 fibers. The formation of hollow cores after oxidation can be traced to differences in the fabrication process such as the starting material and final heat treatment temperature.

Fabrication of Carbon Microcapsules Containing Silicon Nanoparticles-Carbon Nanotubes Nanocomposite for Anode in Lithium Ion Battery

  • Bae, Joon-Won;Park, Jong-Nam
    • Bulletin of the Korean Chemical Society
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    • v.33 no.9
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    • pp.3025-3032
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    • 2012
  • Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a two step polymerization method. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were prepared with a wet-type beadsmill method. A polymer, which is easily removable by a thermal treatment (intermediate polymer) was polymerized on the outer surfaces of Si-CNT nanocomposites. Subsequently, another polymer, which can be carbonized by thermal heating (carbon precursor polymer) was incorporated onto the surfaces of pre-existing polymer layer. In this way, polymer precursor spheres containing Si-CNT nanohybrids were produced using a two step polymerization. The intermediate polymer must disappear during carbonization resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.