Korean | English

pISSN : 1976-4251 / eISSN : 2233-4998

2020 KCI Impact Factor : 0.33
Home > Explore Content > All Issues > Article List

2020, Vol.30, No.4

  • 1.

    Investigation of mechanical, thermal and electrical properties of hybrid composites reinforced with multi-walled carbon nanotubes and fused silica particles

    Oh Yun | Kang Jeong Seok | Kang Chang Soo and 2other persons | 2020, 30(4) | pp.353~365 | number of Cited : 0
    Abstract
    In this study, epoxy composites were reinforced with multi-walled carbon nanotubes and fused silica particles, dispersing the fllers within the epoxy resin based on a simple physical method using only shear mixing and ultrasonication. The hybrid composite specimens with 0.6 wt% of carbon nanotubes and 50 wt% of silica particles showed improved mechanical properties, with increase in tensile strength and Young’s modulus up to 12 and 37%, respectively, with respect to those of the baseline specimens. The experimental results showed that the low thermal expansion of the silica particles improved the thermal stability of the composites compared with that of the baseline specimen, whereas the thermal expansion slightly increased, due to the increased heat transfer from the exterior to the interior of specimens by the carbon nanotube fller. The coefcient of thermal expansion of the hybrid composite specimen reinforced with 0.6 wt% of carbon nanotubes and 50 wt% of silica particles was decreased by 25%, and the thermal conductivity was increased by about 84%, compared with those of the baseline specimen.
  • 2.

    Synergetic effect of MWCNT/nanoclays on microcellular polystyrene hybrid nanocomposite foams

    Hasanzadeh Rezgar | Darvishi Mohammad Mehdi | Azdast Taher | 2020, 30(4) | pp.367~371 | number of Cited : 0
    Abstract
    Synergetic efect of multi-walled carbon nanotubes (MWCNTs)/nanoclays hybrid was investigated on the properties of high�impact polystyrene (HIPS) nanocomposite foams. The glass transition temperature and the cellular structure including the cell size and cell density were studied in details. Adding MWCNT and nanoclay increased the glass transition temperature of HIPS by 8.5 °C and 1.5 °C, respectively. The experimental results indicated that the cell size of HIPS foams was reduced from 84.05 to 60.97 µm and 40.22 µm using MWCNTs and nanoclays, respectively. The synergetic efect of MWCNT/nanoclay was more signifcant by reducing the cell size to 13.69 µm. The cell density was improved from 5.79×104 to 1.77×105 cell/ cm3 using MWCNTs and to 9.39×106 cell/cm3 using nanoclays. The cell density reached to 2.90×107 cell/cm3 using the synergetic efect of MWCNT/nanoclay.
  • 3.

    Preparation of petroleum-based binder pitch for manufacturing thermally conductive carbon molded body and comparison with commercial coal-based binder pitch

    Cho Jong Hoon | Im Ji Sun | Kim Min Il and 2other persons | 2020, 30(4) | pp.373~379 | number of Cited : 0
    Abstract
    In the present study, carbon molded bodies were prepared by using graphite/coke fllers and petroleum-based binder pitch with various softening points, and the thermal properties of the prepared carbon molded bodies were investigated. The ratio of a binder afects the molded body preparation: no molded body was prepared at a low binder pitch content, and swelling occurred during the thermal treatment at a high binder pitch content. The binder pitch thermal treatment yield was the high�est at 41 wt% at the softening point of 150 °C and the lowest at 23 wt% at the softening point of 78 °C. A signifcant mass reduction was found in the range of 150 to 300 °C in the petroleum-based binder pitch, and in the range of 300 to 475 °C in the coal-based binder pitch. The molecular weight of the binder pitch was analyzed through the matrix-assisted laser desorption/ionization time-of-fight (MALDI-TOF) method. The molecular weight ratio within the interval showing the highest binder pitch molecular weight (178 to 712 m/z) was the highest at 66.4% in the coal-based binder pitch (softening point 115 °C) and the lowest at 46.0% in the petroleum-based binder pitch (softening point 116 °C). When the petroleum�based binder pitch was applied, as the softening point was increased, the voids decreased and thus the thermal conductivity increased. The highest thermal conductivity was 99.5 W/mK for the carbon molded bodies prepared using the coal-based binder pitch and 102.8 W/mK for those prepared by using the petroleum-based binder pitch. The results showed that the thermal properties were similar between the coal-based binder pitch (softening point 115 °C) and the petroleum-based binder pitch (softening point 150 °C).
  • 4.

    Preparation of pitch-based activated carbon with surface-treated fly ash for SO2 gas removal

    Kim Min Il | Im Ji Sun | Seo Sang Wan and 3other persons | 2020, 30(4) | pp.381~387 | number of Cited : 1
    Abstract
    Fly ash consists of various metal oxides which can remove SO2 gas by the catalyst efect. When fy ash is added in the prepa�ration process of pitch-based activated carbon, the pitch particles aggregate and fy ash is embedded in the activated carbon. To increase SO2 gas removal performance, activated carbon was prepared by surface-treated fy ash and petroleum-based pitch. Carboxyl groups were introduced into the fy ash by malic acid treatment. The introduced carboxyl groups acted as an activation agent to create micropore around the fy ash, and created micropores were exposed to the fy ash outside of the activated carbon. The exposed fy ash increased removal amount of SO2 gas by a catalytic efect of the metal oxides. The SO2 gas removal performance improved by 34% because of the catalyst efect of the exposed fy ash and improvement in the micropore structure in the activated carbon.
  • 5.

    Reduced graphene oxide/polypyrrole composite: an advanced electrode for high-performance symmetric/asymmetric supercapacitor

    Liu Guijing | Shi Yanying | Wang Lei and 4other persons | 2020, 30(4) | pp.389~397 | number of Cited : 0
    Abstract
    Polypyrrole (PPy) decorated on reduced graphene oxide (rGO) flms is successfully prepared with pyrrole (Py) monomers and rGO through one-step combining oxidation with polymerization reaction. Compared with the pure individual compo�nents, rGO/PPy compound turns out better electrochemical characteristics owing to the introduction of rGO sheets, which improves the specifc surface area and the conductivity of composite material. When the amount of rGO is 10% of the total, the rGO/PPy compound delivers the best capacitance of 389.3 F g−1 at 1.0 A g−1 in a three-electrode system and 266.8 F g−1 at 0.25 A g−1 in the symmetric supercapacitor system. In addition, asymmetric device (rGO/PPy//AC) has been success�fully fabricated using optimized rGO/PPy compound as positive electrode, activated carbon as negative electrode (AC) and 1 M Na2SO4 aqueous solution as electrolyte. The device obtains long cycle stability under the high-voltage region from 0 to 1.6 V, meanwhile displaying the satisfed energy density of 19.7 Wh kg−1 at 478.1 W kg−1. Besides, the rGO/PPy//AC device presents satisfactory rate capability and long life time.
  • 6.

    Analysis of tribological behavior of Al/Gr/MoS2 surface composite fabricated by friction stir process

    Gupta Manoj Kumar | 2020, 30(4) | pp.399~408 | number of Cited : 0
    Abstract
    The life span of many engineering components depends upon their surface properties. The improved surface properties of the materials are essential for enhancing the mechanical and tribological performance of the material. In many applications, the components required only improved surface properties without changing the entire volume properties of the material. The friction stir process (FSP) is a novel processing technique for the fabrication of such surface composites. In the present investigation, the surface composites were fabricated by incorporating molybdenum disulfde (MoS2) and graphite (Gr) as reinforcement on the surface of aluminum alloy (Al 1120) through the friction stir process (FSP) at tool rotational speed of 1400 rpm and tool feed rate of 40 mm/min process parameters using square profle FSP tool. The tribological behaviors of fabricated surface composites were calculated by using a pin on disk tribometer. It was observed that the wear resistance of surface composites improved as compared to the matrix material.
  • 7.

    Preparation of electrochemically exfoliated graphene sheets using DC switching voltages

    Lim Sungmook | HAN, Jonghun | Kang, Hyun Wook and 2other persons | 2020, 30(4) | pp.409~416 | number of Cited : 0
    Abstract
    Among various methods to produce graphene sheets, electrochemical exfoliation has been regarded as an efective method for the mass production of high-quality graphene sheets because of its simplicity and environmental friendliness. However, conventional electrochemical exfoliation has a disadvantage of accumulating intercalating ions at graphite interlayers owing to the use of a constant voltage. In this study, we developed a DC switching technique to achieve more efcient intercalation of ions than that in the conventional method. In the DC switching method, positive and negative voltages are successively applied to release the accumulated intercalating ions. By testing various conditions, we found the optimum switching time to produce high-quality graphene sheets with the highest yield rate and the highest electrical conductivity. As a result, the graphene sheets using this DC switching technique showed 85% higher yield rate, 193% higher electrical conductivity, 160% larger area, and 25% thinner thickness than those obtained when using a constant DC method. We believe that this DC switching technique can be used for large-scale production of high-quality graphene sheets.
  • 8.

    Study of electrical conductivity and photoelectric response of liquid phase exfoliated graphene thin film prepared via spray pyrolysis route

    Vasanthi V. | Logu T. | Ramakrishnan V. and 2other persons | 2020, 30(4) | pp.417~423 | number of Cited : 0
    Abstract
    Facile process for the fabrication of multi-layer graphene thin flm (MLGF) is reported here. Multi-layer graphene dispersion prepared by liquid-phase exfoliation of graphite was sprayed on a glass substrate by spray pyrolysis method. The structural, optical and electrical properties of the deposited MLGF are investigated. The sheets of graphene are deposited uniformly on the substrate and distribution of small graphene sheets with size of 300–500 nm can be observed in SEM image. AFM and micro-Raman results ensured that the spray-coated graphene thin flm is composed of multi-layer graphene sheets. Spray coated graphene thin flm showed signifcant optical transparency of 57% in the visible region (400–550 nm). MLGF pos�sessed the electrical conductivity in the order of 744 S/m with surface resistivity of 3.54 k Ω/sq. The prepared liquid-phase exfoliated graphene thin flm showed superior photoelectric response. The results of this study provided a framework for fabricating an optimized MLGF using a spray pyrolysis route for optoelectronics devices.
  • 9.

    In situ synthesis of MgWO4–GO nanocomposites and their catalytic effect on the thermal decomposition of HMX, RDX and AP

    Wang Jingjing | Wang Weimin | Wang Jinghua and 1other persons | 2020, 30(4) | pp.425~434 | number of Cited : 0
    Abstract
    For solving phase separation of nanoparticles and graphene oxide (GO) in the application process, MgWO4–GO nanocom�posites were successfully synthesized using three diferent dispersants via a facile solvothermal-assisted in situ synthesis method. The structure and morphology of the prepared samples were characterized by X-ray difraction, Scanning electron microscopy, Transmission electron microscopy, Fourier transform infrared and Raman techniques. The experimental results show that MgWO4 nanoparticles are tightly anchored on the surfaces of GO sheets and the agglomeration of MgWO4 nano�particles is signifcantly weakened. Additionally, MgWO4–GO nanocomposites are more stable than self-assembly MgWO4/ GO, which there is no separation of MgWO4 nanoparticles and GO sheets by ultrasound after 10 min. The catalytic results show that, compared with bare MgWO4, MgWO4–GO nanocomposites present better catalytic activities on the thermal decomposition of cyclotetramethylenete tranitramine (HMX), cyclotrimethylene trinitramine (RDX) and ammonium per�chlorate (AP). The enhanced catalytic activity is mainly attributed to the synergistic efect of MgWO4 nanoparticles and GO. MgWO4–GO prepared using urea as the dispersant has the smallest diameter and possesses the best catalytic action among the three MgWO4–GO nanocomposites, which make the decomposition temperature of HMX, RDX and AP reduce by 10.71, 11.09 and 66.6 °C, respectively, and the apparent activation energy of RDX decrease by 68.6 kJ mol−1
  • 10.

    Metronomic chemotherapy of carboplatin-loaded PEGylated MWCNTs: synthesis, characterization and in vitro toxicity in human breast cancer

    Sharma Suraj | Naskar Sweet | Kuotsu Ketousetuo | 2020, 30(4) | pp.435~447 | number of Cited : 0
    Abstract
    Our objective of this study is to design and develop a polyethylene glycol (PEG2000)-modifed multiwall carbon nanotube (PEGylated MWCNT) formulation for oral controlled metronomic chemotherapeutic drug delivery. Multiwall carbon nano�tubes undergo various chemical modifcations including oxidation with strong acids, conjugation of polyethylene glycol, and coating with cellulose acetate phthalate which resulted in the formation of aqueous dispersion and prevention of drug degradation in acidic environment. Advanced analytical procedure such as Fourier transform infra-red, X-ray difraction, diferential scanning calorimetry, thermal gravimetric analysis, transmission electron microscopy, and dynamic light scat�tering techniques were used to evaluate physicochemical characterization. We also performed in vitro cytotoxic study by MTT assay and results revealed that carboplatin-loaded PEGylated MWCNTs did not show signifcant detrimental efect on the viability of MDA-MB-231 (human breast cancer) cells. The maximum encapsulation and drug-loading capacity were determined to be 71.58±0.04 and 39.62±0.07%, respectively. The release of carboplatin from PEGylated MWCNTs was investigated at simulated intestinal fuid (SIF), pH 6.8, after optimizing at simulated gastric fuid (SGF), pH 1.2, by enteric coating. Enteric-coated PEGylated MWCNTs exhibit pH-responsive drug activity in a sustained manner especially at pH 6.8. This surface modifcation strongly suggests that PEGylated MWCNTs could be a potential carrier for metronomic chemotherapeutic agent for high drug resistance, drug with maximum adverse efect and poorly oral bioavailable drugs.
  • 11.

    Photo-Fenton-inspired deoxygenation of tea polyphenol–graphene by household bleach

    Ismail Zulhelmi | 2020, 30(4) | pp.449~456 | number of Cited : 0
    Abstract
    A liquid-phase exfoliation of few-layer graphene in tea is considered as one of the alternative approaches for the preparation of environment-friendly graphene. However, the removal of chemically adsorbed tea-polyphenols from graphene is known to be difcult and the application of centrifugation or fltration alone for the purifcation of graphene against tea-polyphenols is regarded to be almost technically impossible. Notably, a strategy for facile deoxygenation of tea-graphene must be established for a green and economical production of graphene to be realized. In this work, a simple purifcation method of graphene through the application of merely a household bleach (Clorox®) after the pre-exfoliation in black tea has been proposed. It has been found that the carbon–oxygen (C/O) value for graphene increases from 2.7 to 8.1 while the values of C–OH, C–O–C and C=O region in the C1s spectrum of graphene decrease signifcantly after being purifed in bleach for 5 h. The stretching and shift of C–OH, C=O and C–O–C at 3468 cm−1, 1637 cm−1 and 1008 cm−1 from IR spectrum of purifed graphene seems to be in agreement with the produced data from the XPS and Raman spectroscopy. Despite the enhanced ID/IG of Raman from the hybridization of sp2 by hydroxylation, the deoxygenation of tea-graphene does not negatively afect the electrical performance since the sheet resistance was impressively reduced to 193 Ω from 2.1 kΩ. It is believed that this photo-Fenton-inspired purifcation strategy would assist in the washing issue of polyphenol-stabilized graphene for various future electronic applications.
  • 12.

    Enhanced mechanical properties and thermal conductivity of polyimide nanocomposites incorporating individualized boron-doped graphene

    Ha Yu-Mi | Kim Young Nam | Kim Young-O and 4other persons | 2020, 30(4) | pp.457~464 | number of Cited : 0
    Abstract
    Herein, we report signifcantly enhanced mechanical properties and thermal conductivity of polyimide (PI) by incorporating a small amount (0.01 wt %) of individualized boron-doped high-quality graphene as a fller. The boron-doped expandable graphite (B-EG) was synthesized by mixing boric acid (H3BO4) with expandable graphite (EG) and thermally treating the mixture at 2450 °C for 30 min using a graphite furnace in an argon atmosphere. The boron-doped graphene (B-g) was pre�pared by the solution-phase exfoliation of B-EG with an ultrasonication process, which is a method to obtain individualized graphene as well as few-layer graphene. The PI nanocomposites were prepared using the obtained graphene. The PI nanocom�posites synthesized with high-quality B-graphene (B-g) showed enhanced mechanical properties and thermal conductivity compared to those of pure PI due to the doping efects and strong interfacial interactions between graphene and the PI matrix.