• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3057-3060
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• 2009

Ionic palladium(II) complex, [($Me_4en)Pd(L)]_2(ClO_4)_4\;(Me_4$en = N,N,N',N'-tetramethylethylenediamine; L = bis-(4-(4-pyridylcarboxyl)phenyl)methane), allows to form a monodisperse submicrosphere without any template or additive. Surface-perchlorates on the submicrosphere have been exchanged by anionic pH indicators such as thymol blue, bromothymol blue, and bromocresol green. The ionic and amphiphilic properties of the palladium(II) complex appear to be primarily associated with the formation and easy surface-anion exchange of submicrosphere. The surface-anion exchange through the electrostatic interaction is a very good tool for the surface-modification. The color of the pH indicator-exchanged submicrospheres is very sensitive to pH and Hg$^{2+}$ cation, and thus they are promising to submicrospherical indicators.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.265-269
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• 2010

This paper describes the exfoliation and surface modification of muscovite mica for UV coating formulation. For the exfoliation of the mica, hydrothermal process was used in the presence of lithium nitrate ($LiNO_3$). After the cation exchange with $Li^+$ ions, the surface of the mica was modified with several amphiphilic substances to increase compatibility and storage stability in UV coating formulation. Such a hydrophobic surface modification affected colloidal stability as well as dispersibility of the exfoliated mica in UV coating solution. Anticorrosive property of mica/UV coated steel plates was tested by salt spray test (SST) and compared with sodium montmorillonite ($Na^+$-MMT)/UV coated steel plates.

• Journal of Environmental Science International
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• v.12 no.9
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• pp.1005-1010
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• 2003

For the purpose of surveying any possibility of anchoring titanium dioxide on activated carbons to promote their activities as catalysts and/or adsorbents, two activated carbons were oxidized with ammonium peroxydisulfate and followed by anchoring titanium dioxide. The anchoring of titanium dioxide on the oxidized activated carbons were performed via the adsorption of tetrabutyltitanate, hydrolysis with deionized water, and calcination. The effect of oxidizing and anchoring treatment on the surface element composition, surface area, and pore texture were analyzed by XPS, BET and TPD. The oxidation of activated carbons with ammonium peroxydisulfate introduced carboxyl groups on the surface of activated carbons and these carboxyl groups promoted the anchoring of titanium oxide on the activated carbons. However, the treatments affected the surface area and the porosity of activated carbons.

• Journal of Surface Science and Engineering
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• v.22 no.4
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• pp.185-196
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• 1989

The surface modification of a mild and stainless steel by alumina sprayed coating were studied. The effects of surface roughness and bond coating layer on the adhesive strengthy and durability of sprayed specimens were also investiated. The adhesive strength of ceramic coating was affected by surface roughness and bond coating layer thinkness. That showed excellent undergrit blast time and bond coating layer; 60 sec and 0.15-0.33mm, respectively. The adhesive strength and densification of sprayed coating with air pressure were superior to those of without and fracture was mainly occured at alumina-bond coating interface. Under ambient atmosphere at $800^{\circ}C$, the oxides existed within bond coating layer promote diffusion of oxygen to lower durability of sprayed specimens. In this case, fracure was occured at sudstrate-bond coating interface.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1019-1023
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• 1995

A light-emitting silicon material was prepared by electrochemical etching of n-Si single crystal wafers in a solution of hydrofluoric acid and ethanol. Visible photoluminescence from the silicon was inhomogeneous and decayed rapidly in the ambient laboratory conditions or with photoirradiation. Substantial improvements in photoluminescence which include little-dependent luminescence peak energy with excitation energy variation and longer-lasting room temperature visible photoluminescence were achieved when the surface of photoluminescent silicon material was derivatized with the surface modifier of octadecylmercaptan. Surface modification of the photoluminescent silicon was evidenced by the measurements of contact angles of static water drops, FT-IR spectra and XPS data, in addition to changed photoluminescence. Similar improvements in photoluminescence were observed with the light-emitting silicon treated with dodecylmercaptan, but not with octadecane. The present results indicate that sulfurs of octadecylmercaptans or dodecylmercaptans appear to coordinate the surface Si atoms of LESi and perturb the surface states to significantly change the luminescent characteristics of LESi.

• Carbon letters
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• v.6 no.1
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• pp.25-30
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• 2005

The electrosorption of U(VI) from waste water was carried out by using an activated carbon fiber (ACF) felt electrode in a continuous electrosorption cell. In order to enhance the electrosorption capacity at a lower potential, the ACF was electrochemically modified in an acidic and a basic solution. Pore structure and functional groups of the electrochemically modified ACF were examined, and the effects of the modification conditions were studied for the adsorption of U(VI). Specific surface area of all the ACFs was decreased by this modification. The amount of the acidic functional groups decreased with a basic modification, while the amount increased a lot with an acidic modification. The electrosorption capacity of U(VI) decreased on the acid modified electrode due to the shielding effect of the acidic functional groups. The base modified electrode enhanced the capacity due to a reduction of the acidic functional groups. The electrosorption amount of U(VI) on the base modified electrode at .0.3 V corresponds to that of the as-received ACF electrode at .0.9 V. Such a good adsorption capacity was due to a reduction of the shielding effect and an increase of the hydroxyl ions in the electric double layer on the ACF surface by the application of negative potential.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.94-103
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• 2020

This study investigated the effects of ultrasonic nanocrystal surface modification (UNSM) on the deteriorated surface of AISI SUS316L additively manufactured (AM) using the powder bed fusion (PBF) technique. Specifically, the effects of UNSM conditions on surface topology, hardness, and anti-corrosion were examined. Before UNSM treatment, the stainless steel 316L powder was processed via the PBF machine to prepare a substrate. We observed surface changes due to UNSM treatments in PBF SUS316L substrates and examined the correlation between topology changes, roughness, hardness, and anti-corrosion. After UNSM treatment, the coarse as-built surface was refined, and a regular micro-profile was implemented. Compared to the non-treated PBF sample, the waviness and roughness of the surfaces after UNSM treatment decreased by up to 56.0% and 94.5%, respectively, and decreased further as the interval decreased. The hardness improved by up to 63.0% at a maximum depth of 500 ㎛ from top surface by the UNSM treatment. The results of the corrosion test showed that the corrosion resistance of the UNSM specimens was moderately improved compared to that of the untreated surface. This study confirmed that UNSM is an effective post-processing technique for additively manufactured parts.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.78-81
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• 2010

Surface modification of silica nanoparticles was investigated using an aerosol self assembly. Stearic acid was used as surface treating agent. A two-fluid jet nozzle was employed to generate an aerosol of the colloidal suspension, which contained 20 nm of silica nanoparticles, surface modifier, and ethyl alcohol. Powder properties such as morphology, specific surface area and pore size distribution were analyzed by SEM, BET and BJH methods, respectively. Surface properties of the silica power were analyzed by FT-IR. The OH bond of the $SiO_2$ surface was converted to a C-H bond. It was revealed that the hydrophilic surface changed to a hydrophobic one due to the aerosol self assembly. Morphology of the surface treated powder was nanostructured with lots of pores having an average diameter of around $2\;{\mu}m$. Depending on the stearic acid concentration (0.25 to 1.0 wt%), the pore size distribution of the particles and the degree of hydrophobicity ranged from 1.5 nm to 180 nm and 29.6% to 50.2%, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.05a
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• pp.25-26
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• 1999

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.264-266
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• 2011