• Applied Chemistry for Engineering
• /
• v.20 no.4
• /
• pp.402-406
• /
• 2009

$TiO_2$ thin films were surface-modified with atmospheric plasma and their photocatalytic activities were evaluated. The films were deposited on glass plates by dip-coating in a $TiO_2$ sol-gel solution and sintered at various temperatures for various times. Nitrogen plasma was used for the modification and the experiments were carried out varying operational parameters such as discharge power and treatment time. Photocatalytic activity was evaluated based on the degradation efficiency of methylene blue (MB) under irradiation of UV-A and fluorescent light. According to XPS analysis, a little amount of nitrogen was found to be doped in the film surface after the modification. As a result, photocatalytic activity increased under irradiation of UV-A and fluorescent light, especially fluorescent light.

• Korean Journal of Materials Research
• /
• v.27 no.10
• /
• pp.563-568
• /
• 2017

In this study, the coating of an Al-Cr layer on the surface of a Zircaloy-4 alloy was carried out through plasma pretreatment coating and a laser surface melting process. Two different conditions for laser treatment, severe or minimal surface melting of the Zr alloy substrate, were applied to form the final coating. When there was significant surface melting of the Zr alloy, the solidification microstructure of the newly formed coating layer was mainly composed of needle-shaped $Al_3Zr$, Al(Cr) and $Al_7Cr$ phases. On the other hand, the solidification microstructure of the coating layer was mainly composed of Al(Cr) and $Al_7Cr$ phases when there was minimal surface melting of Zr base in the laser process. However, when the coating was maintained at $1100^{\circ}C$ for 2 hours, significant inter-diffusion occurred between the phases in the coating. As a result, the upper part of the coating layer was observed to mainly consist of $Al_3Zr$ and $Al_8Cr_5$ phases, regardless of the laser treatment conditions.

• Journal of Sensor Science and Technology
• /
• v.30 no.3
• /
• pp.165-169
• /
• 2021

The objective of this study was to fabricate a novel hydrophobic stent for reducing restenosis by employing electron beam equipment. The stent was fabricated from a CoCr alloy tube by using a femtosecond laser and was treated with argon plasma. Subsequently, the stent's surface specification changed from hydrophilic to hydrophobic. Application of the electron beam offers several advantages such as a short processing time, whole surface reforming, and enhancement of material properties. As the surface of the stent was rendered hydrophobic, it can provide equivalent or enhanced mechanical properties and greater functionality with a higher radial force at the extended stent in a blood vessel. The obtained results corresponding to the mechanical properties indicate that the contact angle increased to approximately 130°, and the radial force increased to approximately 3 N. Furthermore, cell culture experiments were conducted for verifying whether cells were cultured on the surface-modified CoCr surface. Based on the obtained results, it is believed that an effective reduction in the restenosis of inserted vascular stents is possible.

• Korean Journal of Materials Research
• /
• v.8 no.2
• /
• pp.131-134
• /
• 1998

The deposition rate and surface morphology of Al films deposited by MOCVD have been studied on the $SiO_{2}$ and TiN(60nm/Si) substrates. A1 films were deposited with the pyrolysis of dimethylethylamine alane(DMEAA). When A1 was deposited on Ti& substrate without carrier gas, Al deposition rate increased with H\ulcorner pre- treatment. The $H_2$ gas enhances the CVD reaction at the substrate surface. When Al was deposited on $SiO_{2}$ substrate, $H_2$ plasma pretreatment reduced Al incubation time and made a dense Al film compared with Ar plasma pre- treatment or no pretreatment.

• Polymer(Korea)
• /
• v.32 no.3
• /
• pp.276-283
• /
• 2008

Kind of monomer(MMA, EA, BA, St)and the monomer ratio(80/20 to 20/80) where changed in the preparation of the core shell binder, and property was improved the plasma processing. Each material changed by plasma treatment time($1{\sim}10\;s$) to change to measure the tensile strength, contact angle and adhesion peel strength for the core shell binder optimal conditions for handling the output of the surface treatment. The type of polymerization and composition of the binder is a regardless initiator of APS, the reaction temperature of $85^{\circ}C$ to 0.3 wt% of the surfactant used to indicate when the conversion rate was the highest, core shell composite particle binder got two glass temperature curves. Core shell binder after the plasma processing contact angle change is the PEA/PSt 38 percent of cases within five seconds to indicate slight decrease was a decline rapidly if not handled $0^{\circ}$ to reach. Tensile strength PSt/PMMA varies $46.71{\sim}46.27\;kg_f$/2.5 cm and adhesion strength PEA/PMMA varies $7.89{\sim}14.44\;kg_f$/2.5 cm increases. Overall, adhesion strength of core shell composite particle is in the order of order PEA>PBA>PSt for shell monomer MMA.

• Polymer(Korea)
• /
• v.24 no.6
• /
• pp.869-876
• /
• 2000

In order to improve the cell-compatability of poly(L-lactide-co-glycolide) (75 : 25 by mole ratio of lactide to glycolide, PLGA) surfaces, the physicochemical treatments have been demonstrated. Chemical treatments were 70% perchloric acid. 50% sulfuric acid and 0.5 N sodium hydroxide solution and physical methods were corona and plasma treatment. The water contact angle of surface treated PLGA decreased from 73$^{\circ}$ to 50~60$^{\circ}$, i.e., increased hydrophilicity, due to the introduction of oxygen-containing functional group onto PLGA backbone by the measurement of an electron spectroscopy for chemical analysis. It could be observed that the adhesion and growth of fibroblast cell on physicochemically treated PLGA surfaces, especially perchloric acid treated PLGA surface, were more active than on the controt. In conclusion, it seems that surface wettability as hydrophilicity of PLGA plays an important role in cell adhesion, spreading and growth.

• Composites Research
• /
• v.31 no.1
• /
• pp.17-22
• /
• 2018

Long Fiber Prepreg Sheet (LFPS) has the advantages of excellent production efficiency and formability for complex shapes compared to conventional continuous fiber reinforced composites. When fibrous composites are used with different materials, joining method is important because strength of the joining part determines the strength of the hybrid structure. In this study, the adhesive joint strengths of co-cured LFPS and aluminum were evaluated under various surface treatment conditions and environmental conditions (temperature and moisture conditions). Mechanical abrasion and plasma exposure were used for the surface treatment. The adhesive joints experienced various surface treatments were tested by using single lap joint specimens. Adhesive strengths under various conditions were compared and the most appropriate condition was determined.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.8
• /
• pp.859-869
• /
• 2005

The commercial $V_2O_5-WO_3/TiO_2$ catalysts which had been exposed to the off gas from incinerator for a long time were regenerated by physical and chemical treatment. The catalytic properties and NOx conversion reactivity of those catalysts were examined by analysis equipment and NOx conversion experiment. The characterization of the catalysts were performed by XRD(x-ray diffractometer), BET, POROSIMETER, EDX(energy dispersive x-ray spectrometer), ICP(inductively coupled plasma), TGA(thermogravimetric analyzer) and SEM (scanning electron microscopy). NOx conversion experiment were performed with simulated off gas of the incinerator and $NH_3$ was used as a reductant of SCR reaction. Among the regeneration treatment methods which were applied to regenerate the aged catalysts in this study, it showed that the heat treatment method had excellent regeneration effect on the catalytic performance for NOx conversion. The catalytic performance of the regenerated catalysts with heat treatment method were recovered over than 95% of that of fresh catalyst. For the regenerated catalysts with the acid solution(pH 5) and the alkali solution(pH 12), the catalytic performance were recovered over than 90% of that of fresh catalyst. From the characterization results of the regenerated catalysts, the specific surface area was recovered in the range of $85{\sim}95%$ of that of fresh catalyst. S and Ca element, which are well known as the deactivation materials for the SCR catalysts, accumulated on the aged catalyst surface were removed up to maximum 99%. Among the P, Cr, Zn and Pb elements accumulated on the aged catalyst surface, P, Cr and Zn element were removed up to 95%. But the Pb element were removed in the range of $10{\sim}30%$ of that of fresh catalyst.

• Journal of the Korean institute of surface engineering
• /
• v.46 no.4
• /
• pp.145-152
• /
• 2013

The growth behavior of nanocrystalline diamond (NCD) film has been studied for three different substrates, i.e. bare Si wafer, 1 ${\mu}m$ thick W and Ti films deposited on Si wafer by DC sputter. The surface roughness values of the substrates measured by AFM were Si < W < Ti. After ultrasonic seeding treatment using nanometer sized diamond powder, surface roughness remained as Si < W < Ti. The contact angles of the substrates were Si ($56^{\circ}$) > W ($31^{\circ}$) > Ti ($0^{\circ}$). During deposition in the microwave plasma CVD system, NCD particles were formed and evolved to film. For the first 0.5h, the values of NCD particle density were measured as Si < W < Ti. Since the energy barrier for heterogeneous nucleation is proportional to the contact angle of the substrate, the initial nucleus or particle densities are believed to be Si < W < Ti. Meanwhile, the NCD growth rate up to 2 h was W > Si > Ti. In the case of W substrate, NCD particles were coalesced and evolved to the film in the short time of 0.5 h, which could be attributed to the fact that the diffusion of carbon species on W substrate was fast. The slower diffusion of carbon on Si substrate is believed to be the reason for slower film growth than on W substrate. The surface of Ti substrate was observed as a vertically aligned needle shape. The NCD particle formed on the top of a Ti needle should be coalesced with the particle on the nearby needle by carbon diffusion. In this case, the diffusion length is longer than that of Si or W substrate which shows a relatively flat surface. This results in a slow growth rate of NCD on Ti substrate. As deposition time is prolonged, NCD particles grow with carbon species attached from the plasma and coalesce with nearby particles, leaving many voids in NCD/Ti interface. The low adhesion of NCD films on Ti substrate is related to the void structure of NCD/Ti interface.

• International Journal of Korean Welding Society
• /
• v.1 no.1
• /
• pp.58-62
• /
• 2001

The surface of AC8A Ah alloy was modified by adding the Cu powder using a Plasma Transferred Arc (PTA) welding process. Under the optimum fabricating conditions, the modified surface of AC8A Ah alloy was observed to possess the sound microstructure with a minimum porosity. Hardness and wear resistance properties of the as-fabricated alloy were compared with those of the 76 heat-treated one. In case of the as-fabricated alloy, the hardness of the modified layer was twice that of the matrix region. Although significant increase in the hardness of the matrix region was observed after T6 heat treatment, the hardness of the modified layer was not observed to change. The wear resistance of the modified layer was significantly increased compared to that of the matrix region. The microstructure of a weld zone and the matrix region were investigated using the optical microscope, scanning electron microscope (SEM), electron probe microanalysis (EPMA), and transmission electron microscope (TEM). The primary and eutectic silicon in the weld zone were finer and more curved than in the matrix region, while some precipitates has had been found therein. According to the TEM observation, the predominant precipitate present in the weld zone was the $\theta$'phase, which is precipitated during cooling by rapid solidification in PTA welding process. Improvement of hardness and wear properties in the weld zone in the as-fabricated condition can be explained based on the presence of $\theta$’precipitates and fine primary and eutectic silicon distribution.