간행물
Carbon Letters KCI 등재 Carbon letters
- 발행기관 한국탄소학회
- 자료유형 학술지
- 간기 격월간
- ISSN 1976-4251 (Print)2233-4998 (Online)
- 수록기간 2000 ~ 2023
- 주제분류 자연과학 > 자연과학일반 자연과학 분류의 다른 간행물
- 십진분류KDC 530DDC 620
권호리스트/논문검색
Vol.30 No.4 (2020년 8월) 12건
1.
2020.08
구독 인증기관 무료, 개인회원 유료
In this study, epoxy composites were reinforced with multi-walled carbon nanotubes and fused silica particles, dispersing the fillers 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 filler. The coefficient 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.
4,500원
2.
2020.08
구독 인증기관 무료, 개인회원 유료
Synergetic effect of multi-walled carbon nanotubes (MWCNTs)/nanoclays hybrid was investigated on the properties of highimpact 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 effect of MWCNT/nanoclay was more significant 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 effect of MWCNT/nanoclay.
4,000원
3.
2020.08
구독 인증기관 무료, 개인회원 유료
In the present study, carbon molded bodies were prepared by using graphite/coke fillers 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 affects 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 highest at 41 wt% at the softening point of 150 °C and the lowest at 23 wt% at the softening point of 78 °C. A significant 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-flight (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 petroleumbased 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).
4,000원
4.
2020.08
구독 인증기관 무료, 개인회원 유료
Fly ash consists of various metal oxides which can remove SO2 gas by the catalyst effect. When fly ash is added in the preparation process of pitch-based activated carbon, the pitch particles aggregate and fly ash is embedded in the activated carbon. To increase SO2 gas removal performance, activated carbon was prepared by surface-treated fly ash and petroleum-based pitch. Carboxyl groups were introduced into the fly ash by malic acid treatment. The introduced carboxyl groups acted as an activation agent to create micropore around the fly ash, and created micropores were exposed to the fly ash outside of the activated carbon. The exposed fly ash increased removal amount of SO2 gas by a catalytic effect of the metal oxides. The SO2 gas removal performance improved by 34% because of the catalyst effect of the exposed fly ash and improvement in the micropore structure in the activated carbon.
4,000원
5.
2020.08
구독 인증기관 무료, 개인회원 유료
Polypyrrole (PPy) decorated on reduced graphene oxide (rGO) films is successfully prepared with pyrrole (Py) monomers and rGO through one-step combining oxidation with polymerization reaction. Compared with the pure individual components, rGO/PPy compound turns out better electrochemical characteristics owing to the introduction of rGO sheets, which improves the specific 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 successfully 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 satisfied 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.
4,000원
6.
2020.08
구독 인증기관 무료, 개인회원 유료
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 disulfide ( 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 profile 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.
4,000원
7.
2020.08
구독 인증기관 무료, 개인회원 유료
Among various methods to produce graphene sheets, electrochemical exfoliation has been regarded as an effective 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 efficient 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.
4,000원
8.
2020.08
구독 인증기관 무료, 개인회원 유료
Facile process for the fabrication of multi-layer graphene thin film (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 film is composed of multi-layer graphene sheets. Spray coated graphene thin film showed significant optical transparency of 57% in the visible region (400–550 nm). MLGF possessed 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 film 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.
4,000원
9.
2020.08
구독 인증기관 무료, 개인회원 유료
For solving phase separation of nanoparticles and graphene oxide (GO) in the application process, MgWO4– GO nanocomposites were successfully synthesized using three different dispersants via a facile solvothermal-assisted in situ synthesis method. The structure and morphology of the prepared samples were characterized by X-ray diffraction, 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 nanoparticles is significantly 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 perchlorate (AP). The enhanced catalytic activity is mainly attributed to the synergistic effect 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.
4,000원
10.
2020.08
구독 인증기관 무료, 개인회원 유료
Our objective of this study is to design and develop a polyethylene glycol ( PEG2000)-modified multiwall carbon nanotube (PEGylated MWCNT) formulation for oral controlled metronomic chemotherapeutic drug delivery. Multiwall carbon nanotubes undergo various chemical modifications 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 diffraction, differential scanning calorimetry, thermal gravimetric analysis, transmission electron microscopy, and dynamic light scattering 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 significant detrimental effect 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 fluid (SIF), pH 6.8, after optimizing at simulated gastric fluid (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 modification strongly suggests that PEGylated MWCNTs could be a potential carrier for metronomic chemotherapeutic agent for high drug resistance, drug with maximum adverse effect and poorly oral bioavailable drugs.
4,500원
11.
2020.08
구독 인증기관 무료, 개인회원 유료
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 difficult and the application of centrifugation or filtration alone for the purification 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 purification 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 significantly after being purified 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 purified 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 affect 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 purification strategy would assist in the washing issue of polyphenol-stabilized graphene for various future electronic applications.
4,000원
12.
2020.08
구독 인증기관 무료, 개인회원 유료
Herein, we report significantly 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 filler. 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 prepared 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 nanocomposites 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 effects and strong interfacial interactions between graphene and the PI matrix.
4,000원
