• Applied Chemistry for Engineering
• /
• v.26 no.1
• /
• pp.92-98
• /
• 2015

In this study, phenol-based activated carbons (ACs) were fluorinated at various fluorine partial pressures (0.01~0.03 MPa) and the $Cr^{6+}$ ion adsorption of fluorinated ACs was investigated. According to BET and XPS results, the specific surface area and total pore volume of fluorinated ACs increased by 24.7 and 55.8%, respectively, and fluorine functional groups were introduced to AC surface. The most optimized condition of $Cr^{6+}$ ion adsorption was confirmed at the fluorine partial pressure of 0.02 MPa. And also the removal efficiency of $Cr^{6+}$ ion was up to 98% at 300 mg/L of the initial concentration, and these results showed an approximately three-fold increase compared to that of using untreated ACs. Furthermore, the $Cr^{6+}$ ion adsorption of fluorinated ACs was completed in less than 30 min in contrast with untreated ACs, which was expected to be an increase of the affinity between $Cr^{6+}$ ions and ACs surfaces by fluorination.

• Korean Chemical Engineering Research
• /
• v.54 no.6
• /
• pp.830-837
• /
• 2016

In order to improve the compressive strength of graphite foams (GFms), mesophase pitch (MP) was stabilized in air atmosphere and then fluorinated at different conditions. The Fluorine/Carbon (F/C) in surface-chemical contents of fluorinated MP has range of 23.75%~61.48% according to the different fluorine partial pressure. The compressive strengths of GFms prepared from fluorinated MP were increased in proportion to the apparent densities. The compressive strength of the GFm produced from MP with 35.93% of F/C (%) showed maximum value in $2.93{\pm}0.06MPa$, which was increased up to 27.95% than that of the GFm prepared from un-fluorinated MP. This result was attributed that the interface bonding between of MPs due to fluorine functional groups with high surface energy helped to improve compressive strength of the GFm.

• Transactions of the Korean hydrogen and new energy society
• /
• v.17 no.1
• /
• pp.47-54
• /
• 2006

Activated carbon fibers (ACFs) with high surface area and pore volume were modified with metal Ni impregnation and fluorination and investigated hydrogen storage properties by volumetric method. Micropore volume values of ACFs obtained from surface modification with Ni impregnation and fluorination were decreased 9 and 35 %, respectively. Hydrogen storage capacities of fluorinated ACFs were slightly changed, on the other hand, that of Ni impregnated ACF was considerably increased. It means that hydrogen was not only adsorbed on ACF surface, but also on Ni metal surface by means of dissociation. Although the microphone volume of ACF modified with fluorination was decreased, its hydrogen storage were found not to be changed compared with fresh ACF. These results indicated that the surface of ACF after fluorination modification may be strongly attracted hydrogen due to high electronegativity of fluorine. Therefore, it was proven that hydrogen storage capacity was related with micropore volume and surface property of carbon materials as well as specific surface area.

• Korean Journal of Materials Research
• /
• v.1 no.4
• /
• pp.214-220
• /
• 1991

The effects of $SiO_2$ reactive ion etching (RIE) in $CHF_{3/}C_2F_6$ on the surface properties of the underlying Si substrate were studied by X-ray photoelectron spectroscopy(XPS) and secondary ion mass spectrometry(SIMS) techniques. Angle-resolved XPS analysis was carried out as non-destructive depth profile one for investigating the chemical bonding states of silicion, carbon, oxygen and fluorine. The residue layer consists of C-F polymer. O-F bond was found on the top of the polymer layer and Si-O, Si-C and Si-F bonds were detected between Si substrate and polymer film. A 60nm thick damaged layer of silicon surface mainly contains carbon and fluorine.

• Clean Technology
• /
• v.16 no.4
• /
• pp.239-244
• /
• 2010

The carboxylation of the fluorenyl epoxide with a spiro framework, 9,9'-Bis(4-oxiranylmethoxyphenyl) fluorine (2) was catalyzed by some onium salts such as quaternary ammonium and phosphonium salts to produce the corresponding five-membered cyclic carbonate (3) in an efficient and environmentally benign fashion. The coupling reactions depend greatly on the kind of the halide anions and alkyl chain length of the onium salts. While the reaction was sensitive to the reaction temperature, the reaction trends suggest that the catalytic efficiency of the quaternary ammonium halides may correlate strongly with the melting points of the halides. The reactions using a catalytic amount (2 mol %) of quaternary ammonium bromide with an n-butyl chain at 75.9 bar of $CO_2$ and 393 K give the highest yield of the cyclic carbonate (92%).

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.4
• /
• pp.140-143
• /
• 2005

Carbon Nanotube(CNTs) counter electrode is a promising alternative to Platinum counter electrode for dye sensitized solar cells (DSSCs). In this study, CNT counter electrodes having different visible light transmittance were prepared on fluorine-doped tin oxide (FTO) glass surface by spray coating method. Microstructural images show that there are CNT-tangled region coated on FTO glass counter electrodes. Using such CNT counter electrodes and screen printed $TiO_2$ electrodes, DSSCs were assembled and its I-V characteristics have been studied and compared. Light energy conversion efficiency of DSSCs increased with decreasing in light transmittance of CNT counter electrode. Efficiency of DSSCs having CNT counter electrode is compatible to that of Pt counter electrode.

• Journal of the Korean institute of surface engineering
• /
• v.51 no.6
• /
• pp.365-371
• /
• 2018

1D core-shell nanostructures have attracted great attention due to their enhanced physical and chemical properties. Specifically, oriented single-crystalline $TiO_2$ nanorods or nanowires on a transparent conductive substrate would be more desirable as the building core backbone. However, a facile approach to produce such structure-based hybrids is highly demanded. In this study, a three-step hydrothermal method was developed to grow NiMn-layered double hydroxide-decorated $TiO_2$/carbon core-shell nanorod arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates. XRD, SEM, TEM, XPS and Raman were used to analyze the obtained samples. The in-situ fabricated hybrid nanostructured materials are expected to be applicable for photoelectrode working in water splitting.

• Applied Chemistry for Engineering
• /
• v.34 no.2
• /
• pp.170-174
• /
• 2023

CO₂ is known as one of the causes of global warming, and various studies are being conducted to capture it. In this study, a tetrafluoromethane (CF₄) plasma reaction was performed to improve the CO₂ adsorption of activated carbons (ACs) through changes in surface characteristics, and the adsorption characteristics according to the reaction time were considered. After the reaction, the micropore volume increased up to 1.03 cm³/g. In addition, as the reaction time increased, the fluorine content on the surface increased to 0.88%. It was possible to simultaneously control the pore properties and surface functional groups of the ACs through this experiment. Also, the CO₂ uptake of surface-treated ACs improved up to 7.44% compared to untreated ACs, showing the best performance at 3.90 mmol/g when the reaction time was 60 s. This is due to the synergy effect of the fluorine functional groups introduced on the surface of the ACs and the increased micropore volume caused by the etching effect. It was found that the micropore volume had a greater effect on CO₂ adsorption in the region where the CO₂ uptake was less than 3.67 mmol/g, while the added fluorine content had a greater effect in the region above that.

• Korean Journal of Mineralogy and Petrology
• /
• v.36 no.1
• /
• pp.19-32
• /
• 2023

This study was conducted to remove fluorine (F) (initial concentration of 9.5 mg/L) from leachate of reclaimed mine waste dump site via different methods: (1) co-precipitation using Ca-based materials; (2) adsorption using activated carbon and fly ash; and (3) coagulation and sedimentation using alum. The F removal efficiencies of each case were estimated as 65.6% (Ca co-precipitation), 27.9% (adsorption of activated carbon), 71.5% (adsorption of fly ash), and 96.6% (alum coagulation and sedimentation). In addition, the applicability of the continuous treatment process using alum coagulation was evaluated by lab-scale experiments using simulated mine drainage containing F of lower (6.4 mg/L) and higher (15.7 mg/L) concentrations, and it was confirmed that the treatment of both cases met the domestic standard (below 3 mg/L) for discharged water in clean areas. Furthermore, the results of bench-scale field tests indicated that the water quality standard of discharged water could be satisfied with the proper operation and management of the process.

• Applied Chemistry for Engineering
• /
• v.32 no.6
• /
• pp.653-658
• /
• 2021

Polyvinylidene fluoride (PVDF) is a promising coating material because of its outstanding processability. The PVDF coating, however, has limitations in anti-corrosion application due to its weak hydrophobicity compared to that of other fluoropolymers. In this study, plasma fluorination was performed using carbon tetrafluoride (CF₄) gas to improve anti-corrosion properties of PVDF. The fluorine content and hydrophobicity of PVDF were investigated in different CF₄ flow rates, followed by the determination of anti-corrosion properties. The fluorine content on the surface of the PVDF film increased by up to 46.70%, but the surface free energy was independent of CF₄ flow rate. Meanwhile, the surface roughness of the PDVF film tended to increase by up to 150% and then decrease with increasing CF₄ flow rate. It is considered that the plasma fluorination affects the surface free energy due to the introduction of fluorine functional groups and surface etching. In addition, the degree of corrosion of the PVDF-coated Fe plate was significantly reduced from 49.2% to 19.0% compared to that of the uncoated Fe plate. In particular, the degree of corrosion of the fluorinated PVDF-coated Fe plate was 13.6%, which was 28.4% lower than that of the PVDF-coated Fe plate, showing improved anti-corrosion protection.