• Journal of the Korean institute of surface engineering
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• v.26 no.6
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• pp.334-340
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• 1993

The physico-chemical properties and characteristics after thermal treatment of natural zeolite from Kampo area were studied. The physico-chemical properties of natural zeolite were studied by investigating chemical composition, x-ray diffraction pattern(XRD), scanning electronic microscope(SEM), infrared spec-tra(IR), thermal analysis(TA), and cation exchange capacity(C.E.C.), and the characteristics of natural zeo-lite after thermal treatment from $400^{\circ}C$ to $900^{\circ}C$ were compared with the natural zeolite. This study showed that clinoptilolite was the predominant costituent in natural zeolite, and the natural zeolite contained a little amount of quartz and feldspar as impurities. Zeolite mineral was seen to develop slowly by the natural alternation of volcanic ash considering the almost amorphous crystal structure. The more temperature of ther-mal treatment increased, the more adsorption capacity decreased, considering the fact that the hydroxy peak diminished on infrared spectra, and that cation exchange capacity also decreased distinctly.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1265-1268
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• 2003

The estimation of retention factors by correlation equations with physico-chmical properties maybe helpful in chromatographic work. The physico-chemical properties were water solubility (S), hydrophobicity (P), total energy ($E_t$), connectivity index 1 ($^1{\chi}$), hydrophilic-lipophlic balance (x) and hydrophilic surface area (h) of isoflavones. The retention factors were experimentally measured by RP-HPLC. Especially, the empirical regulations of water solubility and hydrophobicity were expressed in a linear form. The equation between retention factors and various physico-chemical properties of isoflavones was suggested as $k = a_0 + a_1\;log S + a_2log\;P^Q + a_3(E_t) + a_4(^1{\chi}) + a_5(x) + a_6(h)$, and the correlation coefficients estimated were relatively higher than 0.95. The empirical equations might be successfully used for a prediction of the various chromatographic characteristics of substances, with a similar chemical structure.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.177-180
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• 2016

The surface properties of carbon microfibers (CMFs) are modified by chemical deposition of carbon nanofibers via the so-called ethylene processing. CMFs and the modified CMFs (MCMFs) are investigated as reinforcement additives to fabricate polyethylene (PE) composites with enhanced mechanical characteristics. The mechanical properties of the PE-MCMF composites are found to be better and favorable for applications under harsh climatic conditions such as those in Siberia. Improved adhesive interaction between MCMFs and PE is responsible for these enhanced mechanical properties.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.1
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• pp.57-61
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• 2006

The research on surface modification technology has been advanced to improve the properties of engineering materials. Ion implantation is a novel surface modification technology that enhances the mechanical, chemical and electrical properties of substrate's surface using accelerated ions. In this research, nitrogen ions were implanted into AC7A aluminum substrates which would be used as molds for rubber molding. The composition of nitrogenion implanted aluminum and distribution of nitrogen ions were analyzed by Auger Electron Spectroscopy (AES). To analyze the modified surface, properties such as hardness, friction coefficient, wear resistance, contact angle, and surface roughness were measured. Hardness of ion implanted specimen was higher than that of untreated specimen. Friction coefficient was reduced, and wear resistance was improved. From the experimental results, it can be expected that implantation of nitrogen ions enhances the mechanical properties of aluminum mold.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.168-169
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• 2021

A hydrophobic surface increases the contact angle between water and cement paste. There are two methods to increase water contact angle, i.e. lowering the surface energy and adjusting the surface roughness of concrete. The hydrophobicity of concrete can be quantitatively evaluated according to the chemical and physical properties of the solid surface. So far, researches have shown the chemical properties of hydrophobic concrete, however it has not covered how to control surface. This study demonstrated the hydrophobic cement paste prepared by low-resolution molds printed with a 3D printer that exhibit rough surface. Thus, we presented the most hydrophobic characteristics of mold.

• Polymer(Korea)
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• v.25 no.4
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• pp.587-593
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• 2001

In this work, red mud (RM) was chemically modified by 0.1, 1, and 5 M H3PO4 solution to prepare epoxy/RM nanocomposites. The effect of chemical treatment on pH, acid-base values, specific surface area, and porosity of RM surface was analyzed. To estimate the mechanical interfacial properties of epoxy/RM nanocomposites, the critical stress intensity factor (K$_{IC}$) was measured. From the experimental results, it was clearly revealed that the porosity, specific surface area, and acid values of RM surface were developed as the increase of the treatment concentration due to the increase of acidic functional group, including hydroxyl group on RM surface. The mechanical interfacial properties of epoxy/treated-RM nanocomposites were higher than those of epoxy/RM as-received due to an improvement of interfacial bonding between basic matrix and RM surface.

• Macromolecular Research
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• v.13 no.5
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• pp.409-417
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• 2005

The surface of rutile titania nanoparticles was chemically modified by reacting with alkoxy silane. The surface and rheological properties in silicone oil having a wide range of viscosity were investigated. Total surface free energy($\gamma_S$) of the titania particles decreased from 53.12 to 26.94 mJ/$m^2$ as the silane used for surface treatment was increased from 0 to 5.0 wt$\%$. The surface free energy of neat silane was 25.5 mJ/$m^2$, which is quite close to that oftitania particles treated with 5.0 wt$\%$ silane. Due to the hydrophobic nature oftreated-titania, the contact angle was accordingly higher for polar solvent in the order of water>ethylene glycol> formamide>$\alpha$-bromonaphthalene. In sum of rheological behavior, as the applied shear stress or viscosity of the silicone oil increased, the titania particles tend to form layers and agglomerated clusters, showing shear-thinning and shear-thickening behaviors, sequentially. A good dispersion of discrete titania particles obeying a Newtonian flow behavior was achieved at a surface energy or low concentration of silane-treated titania particles in hydrophobic silicone oil.

• Carbon letters
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• v.5 no.1
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• pp.12-17
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• 2004

In this study, the oxyfluorination of PAN-based carbon fibers was undertaken at room temperature using fluorine-oxygen mixtures, and the influence of oxyfluorination on properties was investigated. The surface characteristics of the modified fiber were determined by using X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer. The oxyfluorination of carbon fibers was one of the more effective methods to increase surface wettability by the formation of semicovalent C-F bond and C-O bond depending on reaction conditions. When oxygen mole fraction is increased from 0.5 to 0.9, it is probable that attached fluorine atoms at the surface of the fibers reacted with other components. As increased oxyfluorination time and decreased its pressures, semi-covalent peak is increased at 0.5 of oxygen mole fraction. The total surface free energy of oxyfluorinated carbon fibers decreased with increasing oxygen mole fraction over 0.5. These results indicate that the surface of carbon fibers became much more hydrophilic after the short oxyfluorination. The surface free energy of oxyfluorinated carbon fibers progressively decreased after 10 min treatment. The polar components of surface free energies were however, significantly higher for all oxyfluorinated samples than that for the untreated carbon fiber.

• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.297-301
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• 2021

Microbial fuel cells (MFCs) convert chemical energy to electrical energy via electrochemically active microorganisms. The interactions between microbes and the surface of a carbon electrode play a vital role in capturing the respiratory electrons from bacteria. Therefore, improvements in the electrochemical and physicochemical properties of carbon materials are essential for increasing performance. In this study, a microwave and sulfuric acid treatment was used to modify the surface structure of graphite granules. The prepared expandable graphite granules (EGG) exhibited a 1.5 times higher power density than the unmodified graphite granules (1400 vs. 900 mW/m³). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed improved physical and chemical characteristics of the EGG surface. These results suggest that physical and chemical surface modification using sulfuric acid and microwave heating improves the performance of electrode-based bioprocesses, such as MFCs.

• Membrane and Water Treatment
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• v.1 no.2
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• pp.103-120
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• 2010

Surface modification of microfiltration and ultrafiltration membranes has been widely used to improve the protein adsorption resistance and permeation properties of hydrophobic membranes. Several surface modification methods for converting conventional membranes into low-protein-binding membranes are reviewed. They are categorized as either physical modification or chemical modification of the membrane surface. Physical modification of the membrane surface can be achieved by coating it with hydrophilic polymers, hydrophilic-hydrophobic copolymers, surfactants or proteins. Another method of physical modification is plasma treatment with gases. A hydrophilic membrane surface can be also generated during phase-inverted micro-separation during membrane formation, by blending hydrophilic or hydrophilic-hydrophobic polymers with a hydrophobic base membrane polymer. The most widely used method of chemical modification is surface grafting of a hydrophilic polymer by UV polymerization because it is the easiest method; the membranes are dipped into monomers with and without photo-initiators, then irradiated with UV. Plasma-induced polymerization of hydrophilic monomers on the surface is another popular method, and surface chemical reactions have also been developed by several researchers. Several important examples of physical and chemical modifications of membrane surfaces for low-protein-binding are summarized in this article.