• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.79-84
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• 2011

Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at $380^{\circ}C$ for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.420-426
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• 2021

Graphene, a new material with various advantageous properties, has been actively used in various fields in recent years. Applications of graphene oxide are increasing in combination with other materials due to the different properties of graphene oxide, depending on the number of single and multiple layers of graphene. In this study, single-layer graphene oxide and multi-layer graphene oxide are spray coated on polystyrene, and the physicochemical properties of the coated surfaces are characterized using SEM, Raman spectroscopy, AFM, UV-Vis spectrophotometry, and contact angle measurements. In single-layer graphene oxide, particles of 20 ㎛ are observed, whereas a 2D peak is less often observed, and the difference in surface height increases according to the amount of graphene oxide. Adhesion increases with an increase in graphene oxide up to 0.375 mg, but decreases at 0.75 mg. In multi-layer graphene oxide, particles of 5 ㎛ are observed, as well as a 2D peak. According to the amount of graphene oxide, the height difference of the surface increases and the adhesive strength decreases. Both materials are hydrophilic, but single-layer graphene oxide has a hydrophilicity higher than that of multi-layer graphene oxide. We believe that multi-layer graphene oxide and single-layer graphene oxide can be implemented based on the characteristics that make them suitable for application.

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.593-600
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• 2021

Herein, a series of g-C₃N₄ modified Bi₂MoO₆ nanocomposites using Bi₂MoO₆ and melamine as original materials are fabricated via sintering process. For presynthesis of Bi₂MoO₆ an ultrasonic-assisted hydrothermal technique is researched. The structure and composition of the nanocomposites are characterized by Raman spectroscopy, X-ray diffraction (XRD), and high-resolution field emission scanning electron microscopy (SEM). The improved photoelectrochemical properties are studied by photocurrent density, EIS, and amperometric i-t curve analysis. It is found that the structure of Bi₂MoO₆ nanoparticles remains intact, with good dispersion status. The as-prepared g-C₃N₄/Bi₂MoO₆ nanocomposites (BMC 5-9) are selected and investigated by SEM analysis, which inhibits special morphology consisting of Bi₂MoO₆ nanoparticles and some g-C₃N₄ nanosheets. The introduction of small sized g-C₃N₄ nanosheets in sample BMC 9 is effective to improve the charge separation and transfer efficiency, resulting in enhancing of the photoelectric behavior of Bi₂MoO₆. The improved photoelectronic behavior of g-C₃N₄/Bi₂MoO₆ may be attributed to enhanced charge separation efficiency, photocurrent stability, and fast electron transport pathways for some energy applications.

• Fashion & Textile Research Journal
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• v.24 no.1
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• pp.138-145
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• 2022

Today, graphene loaded textiles are being considered promising smart clothing due to their high conductivity. In this study, we reported reduced graphene oxide(r-GO) deposited pure cotton fabrics fabricated with a colloidal solution of graphene(GO), using a one-step aerosol spray pyrolysis(ASP) process and their potential application on smart textiles. The ASP process is advantageous in that it is easily implementable and can be applied for continuous processing. Moreover, this process has never been applied to deposit r-GO on pure cotton fabric. The field emission-scanning microscopy (FE-SEM) observation, Fourier transform-infrared(FT-IR) analysis, Raman spectroscopy, X-ray diffraction(XRD) analysis, and ultraviolet transmittance(UVT) were used to evaluate material properties of the r-GO colloids. The resistance was also measured to evaluate the electrical conductivity of the specimens. The results revealed that the r-GO was successfully deposed on specimens, and the specimen with the highest electrical conductivity demonstrated an electrical resistance value of 2.27 kΩ/sq. Taken together, the results revealed that the ASP method demonstrated a high potential for effective deposition of r-GO on cotton fabric specimens and is a prospect for the development of conductive cotton-based smart clothing. Therefore, this study is also meaningful in that the ASP process can be newly applied by depositing r-GO on the pure cotton fabric.

• Advances in nano research
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• v.13 no.3
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• pp.207-216
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• 2022

In this paper, a novel model is developed for frequency behavior of single walled carbon nanotubes. The governing equation of motion is constructed method based on the Sander theory using Rayleigh-Ritz's method The frequencies enhances on increasing the power law index using simply supported, clamped and clamped free end conditions. The frequency curve for C-F is less than other conditions. It is due to the physical constraints which are applied on the edge of the CNT. It is observed that the C-F boundary condition have less frequencies from the other two conditions. The frequency phenomena for zigzag are insignificant throughout the aspect ratio. Moreover when index of power law is increased then frequencies increases for all boundary conditions. The natural frequency mechanism for the armchair (10, 10) for various values of power law index with different boundary conditions is investigated. Here frequencies decrease on increases the aspect ratio for all boundary conditions. The frequency curves of SS-SS edge condition is composed between the C-C and C-F conditions. The curves of frequency are less significant from small aspect ratio (L/d = 4.86 ~ 8.47) and decreases fast for greater ratios. It is found that the frequencies via aspect ratios, armchair (10, 10) have higher values from zigzag (10, 0). It is due to the material structure which is made by the carbon nanotubes. The power law index have momentous effect on the vibration of single walled carbon nanotubes. The present frequency result is also compared numerically experimentally with Raman Spectroscopy.

• Fashion & Textile Research Journal
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• v.24 no.1
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• pp.146-155
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• 2022

We proposed a simple process of creating electroconductive textiles by using PEDOT:PSS(Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate))/non-oxidized graphene to coat polyamide or polyurethane knitted fabric for smart healthcare purposes. Electroconductive textiles were obtained through a coating process that used different amounts of PEDOT:PSS/non-oxidized graphene solutions on polyamide/polyurethane knitted fabric. Subsequently, the surface, electrical, chemical, weight change, and elongation properties were evaluated according to the ratio of PEDOT:PSS/non-oxidized graphene composite(1.3 wt%:1.0 wt%; 1.3 wt%:0.6 wt%; 1.3 wt%:0.3 wt%) and the number of applications(once, twice, or thrice). The specimens' surface morphology was observed by FE-SEM. Further, their chemical structures were characterized using FTIR and Raman spectroscopy. The electrical properties measurement (sheet resistance) of the specimens, which was conducted by four-point contacts, shows the increase in conductivity with non-oxidized graphene and the number of applications in the composite system. Moreover, a test of the fabrics' mechanical properties shows that PEDOT:PSS/non-oxidized graphene-treated fabrics exhibited less elongation and better ability to recover their original length than untreated samples. Furthermore, the PEDOT:PSS/non-oxidized graphene polyamide/polyurethane knitted fabric was tested by performing tensile operations 1,000 times with a tensile strength of 20%; Consequently, sensors maintained a constant resistance without noticeable damage. This indicates that PEDOT:PSS/non-oxidized graphene strain sensors have sufficient durability and conductivity to be used as smart wearable devices.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.106-110
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• 2023

Lignin is compatible with various polymeric materials and useful as a carbon precursor. In this work, carbon monolith films were produced from polyacrylonitrile (PAN)@lignin precursor films by a controlled carbonization cycle. In addition, their morphological features, electrical properties, and adsorption behavior were analyzed and compared with those of carbonized PAN films. The successful formation of PAN@lignin precursor was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. SEM was used to examine the morphology of precursor and carbonized films, revealing that both precursor and carbonized films retained structural stability following carbonization. A trace of lignin in the carbonized films was also found. The pore structure of the carbonized PAN@lignin film was measured using the BET method, indicating the formation of fairly uniform pores. The electrical properties were also analyzed to obtain the Ohmic relation, which demonstrated that the electrical signal was influenced by incoming materials. Finally, the carbonized PAN@lignin films were useful as adsorbents to remove metal ions. This study provides important information for future initiatives in relevant research fields.

• Journal of the Korean institute of surface engineering
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• v.57 no.1
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• pp.22-30
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• 2024

This study reports a direct growth of carbon nanotubes (CNTs) on the surface of LiCoO₂ (LCO) powders to apply as highly efficient cathode materials in lithium-ion batteries (LIB). The CNT synthesis was performed using a thermal chemical vapor deposition apparatus with temperatures from 575 to 625 ℃. Ferritin molecules as growth catalyst of CNTs were mixed in deionized (DI) water with various concentrations from 0.05 to 1.0 mg/mL. Then, the LCO powders was dissolved in the ferritin solution at a ratio of 1g/mL. To obtain catalytic iron nanoparticles on the LCO surface, the LCO-ferritin suspension was dropped in silicon dioxide substrates and calcined under air at 550℃. Subsequently, the direct growth of CNTs on LCO powders was performed using a mixture of acetylene (10 sccm) and hydrogen (100 sccm) for 10 min. The growth behavior was characterized by scanning and transmission electron microscopy, Raman scattering spectroscopy, X-ray diffraction, and thermogravimetric analysis. The optimized condition yielding high structural quality and amount of CNTs was 600 ℃ and 0.5 mg/mL. The obtained materials will be developed as cathode materials in LIB.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2842-2849
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• 2024

The amorphous glasses containing PbO, ZnO, MgO, and B₂O₃ have been fabricated using the melt quenching technique. The structural properties have been analysed using the Fourier-transform infrared (FTIR) and Raman spectroscopy. Derivative of Absorption Spectra Fitting (DASF) method have been used to estimate the band gap energy from the UV-Vis absorption data which decreases from 3.02 eV to 2.66 eV with increasing the concentration of the PbO.The four glass samples 0.284 and 0.826 MeV showed unique variations in terms of gamma attenuation ability. LZMB4 glass sample proved to be the mist effective in terms of shielding of gamma radiation as it requires little distance compared to LZMB3, LZMB2 and LZMB1 to attenuate. RPE revealed a raise with increase in the thickness of the material and reduces as the energy raises. TF is superior in LZMB1 compared to LZMB2, LZMB3 and LZMB4, confirming that, LZMB4 will attenuate better. The Z_Eff of the materials was seen falling as the energy increases, confirming that the linear attenuation coefficient of the glass materials decreases when the energy is increased. The results confirmed that, glass material LZMB4 is the best option especially for gamma radiation shielding applications compared to LZMB3, followed by LZMB2, then LZMB1.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.1-10
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• 2020

The atomic structures of silicate liquids at high pressure provide insights into the transport properties including thermal conductivities or elemental partitioning behavior between rocks and magmas in Earth's interior. Whereas the local electronic structure around silicon may vary with the arrangement of the nearby oxygens, the detailed nature of such relationship remains to be established. Here, we explored the atomic origin of the pressure-induced changes in the electronic structure around silicon by calculating the partial electronic density of states and L₃-edge X-ray absorption spectra of SiO₂ polymorphs. The result showed that the Si PDOS at the conduction band varies with the crystal structure and local atomic environments. Particularly, d-orbital showed the distinct features at 108 and 130 eV upon the changes in the coordination number of Si. Calculated Si XAS spectra showed features due to the s,d-orbitals at the conduction band and varied similarly with those observed in s,d-orbitals upon changes in the crystal structures. The calculated Si XAS spectrum for α-quartz was analogous to the experimental Si XRS spectrum for SiO₂ glass, implying the overall similarities in the local atomic environments around the Si. The edge energies at the center of gravity of XAS spectra were closely related to the Si-O distance, thus showing the systematic changes upon densification. Current results suggest that the Si L_2,3-edge XRS, sensitive probe of the Si-O distance, would be useful in unveiling the densification mechanism of silicate glasses and melts at high pressure.