• Korean Journal of Materials Research
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• v.33 no.4
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• pp.124-129
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• 2023

This study assessed the influences of fluorine introduced into DLC films on the structural and mechanical properties of the sample. In addition, the effects of the fluorine incorporation on the compressive stress in DLC films were investigated. For this purpose, fluorinated diamond-like carbon (F-DLC) films were deposited on cobalt-chromium-molybdenum substrates using radio-frequency plasma-enhanced chemical vapor. The coatings were examined by Raman scattering (RS), Attenuated total reflectance Fourier transform infrared spectroscopic analysis (ATR-FTIR), and a combination of elastic recoil detection analysis and Rutherford backscattering (ERDA-RBS). Nano-indentation tests were performed to measure hardness. Also, the residual stress of the films was calculated by the Stony equation. The ATR-FTIR analysis revealed that F was present in the amorphous matrix mainly as C-F and C-F₂ groups. Based on Raman spectroscopy results, it was determined that F made the DLC films more graphitic. Additionally, it was shown that adding F into the DLC coating resulted in weaker mechanical properties and the F-DLC coating exhibited lower stress than DLC films. These effects were attributed to the replacement of strong C = C by feebler C-F bonds in the F-DLC films. F-doping decreased the hardness of the DLC from 11.5 to 8.8 GPa. In addition, with F addition, the compressive stress of the DLC sample decreased from 1 to 0.7 GPa.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.90-97
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• 2009

Dispersion and self-sensing evaluation for single-carbon fiber reinforced in three different acid-treated CNT-epoxy nanocomposites were investigated by electro-micromechanical techniques and wettability tests. Self-sensing based on contact resistivity exhibited more noise for single carbon fiber/acid-treated CNT-epoxy composites than it did for untreated CNT. However, the apparent modulus was higher the acid treated case than the untreated case which is attributed to better stress transfer. The interfacial shear strength (IFSS) between carbon fibers and the CNT-epoxy was lower than that between carbon fiber and neat epoxy due to the increased viscosity associated with the addition of the CNT. The CNT-epoxy nanocomposite exhibited more hydrophobicity than did neat epoxy. Change in the thermodynamic work of adhesion was consistent with changes in the IFSS but disproportional to that of the apparent modulus. The optimum condition of acid treatment on the need can be obtained instead of the maximum condition.

• Composites Research
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• v.31 no.6
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• pp.385-391
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• 2018

In this study, carbon fibers were fabricated via carbonization of oxidized polyacrylonitrile (oxi-PAN) under different carbonization conditions. Carbonization of oxi-PAN fiber was performed under four different temperature (1300, 1400, 1500, $1600^{\circ}C$) with four different fiber tensions (14, 25, 35, 45 MPa). Effect of carbonization process on the structural development and mechanical properties of carbon fiber were characterized by single filament fiber tensile test and Raman spectroscopy. A clear correlation exists between the Raman spectrum and the tensile modulus of carbon fiber and effect of carbonization temperature on the tensile modulus showed increased tendency only at higher fiber tension (${\geq}25MPa$) while tensile strength showed decreased or random tendency. Therefore, it may be concluded that the optimization of carbonization temperature of oxi-PAN fiber also requires optimization of fiber tension.

• Composites Research
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• v.29 no.5
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• pp.256-261
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• 2016

In this work, we have prepared the filter papers with the pitch-based activated carbon fibers and the binder fibers using wet-laid process. The influence of the binder fiber on the porosity of the filter papers has been investigated by using nitrogen adsorption isotherms at 77 K and a scanning electron microscope (SEM). As a result, the specific surface area has increased with an decrease in the content of binder fiber. It has been shown that the optimum ratio of pitch-based activated carbon fibers and the binder fibers is 70:30, resulting in high porosity, excellent bonding strength, large specific surface area ($650.4m^2/g$) and high noxious gas removal efficiency (86.9%). In addition, it has been observed that the mean pore size distribution of the fiber papers has not been affected by the binder fiber.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.514-519
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• 2020

Graphite materials for lithium ion battery anode materials are the most commercially available due to their structural stability and low price. Recently, research efforts have been conducted on carbon coatings by improving side reactions at the edge site of carbon materials. The carbon coating process has classified into a CVD by chemical reaction, wet coating process with solvent and dry coating by mechanical impact. In this paper, the rapid crush/coating process was used to solve the problem of which only few parts of the carbon precursor (pitch) can be used and also environmental problems caused by solvent removal in the wet coating process. When the ratio of needle coke to pitch was 8 : 2 wt%, and the rapid crush/coating process was carried out, it was confirmed that the fracture surface was coated by pitch. The pitch-coated sample was treated at 2400 ℃ and 41.8% improvement in 10C/0.1C rate characteristic was observed. It is considered that the material simply manufactured through the simple crush/coating process can be used as an anode electrode material for a lithium ion battery.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.159-163
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• 2023

Salt cores have attracted considerable attention for their application to the casting process of electric vehicle parts as a solution to ecological issues. However, the salt core still has low mechanical strength for use in high-pressure die casting. In this study, we investigated the improvements in the bending strength of KCl-based salt cores resulting from the use of reinforcing materials. KCl and Na₂CO₃ powders were used as matrix materials, and glass fiber and carbon fiber were used as reinforcing materials. The effects of carbon fiber and glass fiber contents on the bending strength properties were investigated. Here, we obtained a new fiber-reinforced salt core composition with improved bending strength for high-pressure die casting by adding a relatively small amount of glass fiber (0.3 wt%). The reinforced salt core indicates the improved properties, including a bending strength of 49.3 Mpa, linear shrinkage of 1.5%, water solubility rate of 16.25 g/min·m² in distilled water, and hygroscopic rate of 0.058%.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.323-328
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• 2010

In this work, an intention to synthesize the carbon molecular sieve (CMS) with ideal sieving properties from palm shell has been attempted. The process includes three main stages: carbonization, carbon dioxide activation and polymer deposition using polyfurfuryl alcohols. Palm shell based activated carbon (AC) produced by carbon dioxide activation was used as raw material in synthesis of CMS. After preparing palm shell based AC, optimum concentration ratio of furfuryl alcohols and formaldehyde to AC for CMS synthesis was obtained in this study. Deposition of polyfurfuryl alcohols on the palm shell based AC was then carried out prior to carbonization. These polymer deposited AC was subjected to carbonization at $700-900^{\circ}C$ under inert condition. All the microporous materials were analyzed using micromeritics ASAP/2020. The results show that optimum concentration ratio of furfuryl alcohol and formaldehyde to AC is 1:2.5. The micropore with pore width less than 7 ${\AA}$ was formed on the polymer deposited AC at $700^{\circ}C$, $800^{\circ}C$ and $900^{\circ}C$ for 1.5 hours. Carbonization temperature at $900^{\circ}C$ for 1.5 hours was found to be optimum for CMS synthesis. The CMS produced under this condition has pore width of 5.884 ${\AA}$.

• Composites Research
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• v.27 no.4
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• pp.168-173
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• 2014

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through various experiments. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and $T_g$ was conformed according to different epoxy mixing ratio. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.98-98
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• 2005

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.762-770
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• 2005

Adsorption and biodegradation performance of chlorinated by-products such as trihalomethanes(THMs) and haloacetic acids(HAA5) on granular activated carbon were evaluated in this study. The coconut-based activated carbon was found more effective than others in adsorption of THMs due to larger pore volume of less than $20{\AA}$. The wood-based activated carbon was less effective than coconut- and coal-based activated carbon in adsorption nevertheless having larger pore volume and specific surface area than others. The maximum adsorption capacity(X/M) of coconut-based carbon for THMS was 1.1-1.5 times larger than coal based carbon and 14.1-31.4 times larger than wood based activated carbons. Activated carbon usage rate(CUR) of coconut-, coal- and wood-based activated carbons for chloroform were 9.4, 11.2 and 38 g/day respectively. In the evaluation of adsorption isotherm of THM species for coconut-, coal- and wood-based activated carbons, k value of chloroform was the lowest in the THM species, It menas that chloroform is difficult to remove by activated carbon adsorption. and BDCM, CDBM, bromoform are in the succeeding order of adsorption. In the evaluation of biodegradation rate, mean biodegradation rate was chloroform 7%, BDCM 5%, CDBM 4% and bromoform 3%, respectively THMs are difficult materials to be biodegraded. In the evaluation of characteristics of adsorption and biodegradation for HAA5 species, HAA5 species appear to be removed effectively by activated carbon. Most of the HAA5 are adsorbed at the beginning of operation periods and HAA5 except TCAA were almost biodegraded from bed volume of 2,000 and more than 90 percent of biodegradation of TCAA was started from bed volume around 4,000 and after that biodegradation rate was increased with increasing bed volume.