• Journal of Oral Medicine and Pain
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• v.25 no.1
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• pp.41-51
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• 2000

This study was performed to investigate the effect of three modalities commonly used for reduction of oral malodor and to review the contributing factors for halitosis. For this study, 45 subjects of good general health in their third decades were selected, and they were divided into three groups by each modality, that is, tongue scraping, $ZnCl_2$ mouth rinse, and periodontal treatment. Subjective sense of halitosis, diets, Oral hygiene index based on tooth brushing and tongue brushing habit, resting salivary flow rate, gingival index, degree of tongue coating were recored in the Halito-Chart designed by the author. Oral malodor converted from volatile sulfur compound was measured by the Halimeter$^{(R)}$(Interscan Co., USA), and the correlation between the oral factors and pre-treatment halimeter score were analysed. Data obtained were analysed by the SPSS windows program and the results of this study were as follows : 1. There were no significant correlation between oral factors such as oral hygiene index, salivary flow rate, gingival index, degree of tongue coating and pre-treatment halimeter score. 2. Difference between pre- and post-treatment halimeter score by the three modalities were significant, but correlation between pre- and post-treatment score within group was most significant in the periodontal treatment group followed by the tongue scraping group and lowest in the $ZnCl_2$ mouth rinse group. 3. Reduction of halimeter score was significant only in subjects with relatively more tongue coating in the tongue scraping group, but in the $ZnCl_2$ mouth rinse group and in the periodontal treatment group, the modality applied to each group had same significant effects without regard to the degree of oral hygiene index or gingival index. 4. Men had more tongue coating than women, and reduction of halimeter score was significant in men, but not in women.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.237-242
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• 2012

We report on the NO gas sensing properties of Al-doped zinc oxide-carbon nanotube (ZnO-CNT) wire-like layered composites fabricated by coaxially coating Al-doped ZnO thin films on randomly oriented single-walled carbon nanotubes. We were able to wrap thin ZnO layers around the CNTs using the pulsed laser deposition method, forming wire-like nanostructures of ZnO-CNT. Microstructural observations revealed an ultrathin wire-like structure with a diameter of several tens of nm. Gas sensors based on ZnO-CNT wire-like layered composites were found to exhibit a novel sensing capability that originated from the genuine characteristics of the composites. Specifically, it was observed by measured gas sensing characteristics that the gas sensors based on ZnO-CNT layered composites showed a very high sensitivity of above 1,500% for NO gas in dry air at an optimal operating temperature of $200^{\circ}C$; the sensors also showed a low NO gas detection limit at a sub-ppm level in dry air. The enhanced gas sensing properties of the ZnO-CNT wire-like layered composites are ascribed to a catalytic effect of Al elements on the surface reaction and an increase in the effective surface reaction area of the active ZnO layer due to the coating of CNT templates with a higher surface-to-volume ratio structure. These results suggest that ZnO-CNT composites made of ultrathin Al-doped ZnO layers uniformly coated around carbon nanotubes can be promising materials for use in practical high-performance NO gas sensors.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.277-277
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• 2012

New concept of coating process, which is called Electro Magnetic Levitation-Physical Vapour deposition (EML-PVD) was developed and investigated. Zinc coating was performed and succeeded for the first time on the steel strip (Cold-rolled Steel) in a continuos pilot line using the EML-PVD process which is specialized in the high deposition rate and high vapor yield. EML-PVD will be expected to be the next generation coating technology to be applied to the steel industry.

• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.65-70
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• 2007

There are many kinds of protection methods for marine structures, with varyingeconomical and environmental advantages. The coating protection method is being widely used in both continental and marine structures. In this study, by adding some additives, such as Zn powder(Zn), carbon black(CB) to epoxy anti-corrosive paint, the effect on the corrosion resistance was investigated throughan electrochemical method. The additive of Zn(20)+CB(10) showed the lowest passivity current density. Polarization resistance in both cyclic voltammogram and impedance measurement of an additive of Zn(20)+CB(10) was also the largest value, compared to other additives. Furthermore, rusting and bubbling was not observed on the surface of the test specimen with the additive of Zn(20)+CB(10), compared to other specimens. It is suggested that the corrosion resistance of the anti-corrosive paint can be improved by using some additives.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.735-738
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• 2000

The characteristics of wire electrical discharge machining (WEDM) are governed by many factors such as the power supply type, operating condition and electrode material. This work deals with the effect of wire electrode materials on the machining characteristics such as, metal removal rate, surface characteristics and surface roughness during WEDM A wire's thermal physical properties are melting point, electrical conductivity and vapor pressure. One of the desired qualities of wire is a low melting point and high vapor pressure to help expel the contaminants from the gap. They are determined by the mix of alloying elements (in the case of plain brass and coated wire) or the base core material(i.e. molybdenum). Experiments have been conducted regarding the choice of suitable wire electrode materials and influence of the properties of these materials on the machinability and surface characteristics in WEDM, the experimental results are presented and discussed from their metallurgical aspect. And the coating effect of various alloying elements(Au, Ag, Cu, Zn, Cr, Mn, etc.) to the Cu or 65-35 brass core on them was reviewed also. The removal rate of some coated wires are higher than that of 65-35 brass electrode wire because the wire is difficult to break due to the wire cooling effect of Zn evaporation latent heat and the Zn oxide on the surface is effective in preventing short circuit. The removal rate increases with increasing Zn content from 35, 40 and Zn coated wire

• Laser Solutions
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• v.4 no.3
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• pp.30-39
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• 2001

This work was tamed out to apply a laser welding technique in joining between a Zn coated low carbon steel plate(SECC) and a free cutting carbon steel shaft(SUM24L) with or without W coating. Experiments were carried out and analysed by applying the FD(factorial design)method to obtain the optimum Laser welding condition. Optical microscopy, SEM, TEM and XRD analyses were performed in order to observe the microstructures in the fusion zone and the HAZ. Mechanical properties of the welded specimens were examined by microhardness test, tensile test and twist test. There was no flawed Zn in the fusion zone by EDS analysis. This means that during the welding process, Zn gas could be eliminated by appropriate shielding gas flow rate and butt welding gap. Ni coating itself did not influence on the tensile strength and hardness. However, twist bending strength and the weld depth of the Ni-coated free cutting carbon steel were lower as compared with those of the uncoated free cutting carbon steel. It was attributed to a lower absorbance of laser beam to the shin Ni surface. According to the results of the factorial design tests, the twist bending strength of welded specimens was primarily affected by pulse width, laser power, frequency and speed.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.325-330
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• 2010

Many surface protection methods have been developed to apply for constructional steels used under severe corrosive environment. Thermal spray coating has been known to be an attractive technique due to its relatively high coating speed. Furthermore high corrosion resistance of coated film with thermal spray is required to expand its application. Four types of coated films(DFT:300 um) such as pure zinc, pure aluminum and two Al-Zn alloy (Al:Zn=85:15 and Al:Zn=95:5) onto the carbon steel (SS401) were prepared with arc spray, and the corrosion behavior of their samples were evaluated by electrochemical method in this study. Pure aluminum sample showed high corrosion resistance behavior exposed to sea water solution and pure zinc and alloy (Al:Zn=95:5) samples followed pure aluminum sample. The other alloy(Al:Zn=85:15) so called galvalume coated onto the carbon steel ranks the 4th corrosion resistance in this study. The results of porosity ratio of those samples by observation are well matched with the electrochemical data.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.7-12
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• 2013

The dissimilar welding between magnesium alloy and steel sheet was required in automobile industry to increase the strength of the dissimilar joints. Laser brazing is one of the good joining processes for Mgsteel dissimilar joint. In this study, the effect of coating materials was evaluated on the laser brazing for the dissimilar joint between AZ31 and coated steels such as Zn, Sn and Ni. Diode direct laser was used to braze the lap-edge joint with Mg600 filler wire and Superior #21 flux. The wettability was best on Zn coated steel. The interlayer was formed at the interface between brazement and steel for all coating materials. The strengths of brazed specimen were 146.5N/mm, 204.6N/mm and 101.6N/mm for Zn, Sn and Ni coated steel respectively.

• Corrosion Science and Technology
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• v.18 no.1
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• pp.16-23
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• 2019

Steels for automotive fuel tank require unique properties such as corrosion resistance for fuel, welding for joining, forming for press, and painting for exterior. Recently, automakers have been requiring excellent seam weldable steels to enhance manufacturing productivity of fuel tank. Thus, POSCO developed a new type of functional steels coated with nano-composite thin layer on Zn-Ni plating steels. The nano-composite coating solution was prepared by mechanical fine dispersion of solutions consisting of polymeric resin and nano-composite materials in aqueous media. The composite solution was coated on the plating steel surface by using roll coater and cured through induction furnace. These new developed plating steels were evaluated for quality performances such as seam and spot weldability, press formability, and corrosion resistance. These new functional steels coated with nano-composite layer exhibited excellent seam weldability and press formability. Detailed discussion of coating solution and experimental results suggest that nano-sized composite dispersion as coating layer plays a key role in enhancing the quality performance.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.15-18
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• 2012

Transparent conductive indium zinc oxide thin films were prepared by spin-coating a sol-gel solution. Zinc acetate dihydrate [$Zn(CH_3COO)_2{\cdot}2H_2O$] and indium acetate [In$(CH_3COO)_3$] were used as starting precursors, and 2-methoxyethanol with 1-propanol as solvents. Upon annealing in a temperature range from 500 to $1000^{\circ}C$, the thin film crystallizes into polycrystalline $In_2O_3$(ZnO). The lowest electrical resistivity was obtained at an annealing temperature of $700^{\circ}C$ as $2{\Omega}{\cdot}cm$. Average optical transmittances were higher than 80% at all annealing temperatures. These experimental results confirm that the sol-gel spin-coating can be a good simplified practical method for forming transparent electrodes.