• Applied Science and Convergence Technology
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• v.25 no.3
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• pp.51-55
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• 2016

The surface treatment of a titanium implant is investigated with a non-thermal atmospheric pressure plasma jet. The plasma jet is generated by the injection of He and $O_2$ gas mixture with a sinusoidal driving voltage of 3 kV or more and with a driving frequency of 20 kHz. The generated plasma plume has a length up to 35 mm from the jet outlet. The wettability of 4 different titanium surfaces with plasma treatments was measured by the contact angle analysis. The water contact angles were significantly reduced especially for $O_2/He$ mixture plasma, which was explained with the optical emission spectroscopy. Consequently, plasma treatment enhances wettability of the titanium surface significantly within the operation time of tens of seconds, which is practically helpful for tooth implantation.

• Carbon letters
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• v.10 no.3
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• pp.234-238
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• 2009

The field emitters were fabricated by screen-printing of carbon nanotube paste, and their emission stabilities were evaluated. It was found that the emission stability measured in a sealed device is much higher than that measured in a vacuum chamber in spite of similar pressure. This was because oxygen gas was scarcely remained in the sealed device, while the gas is continuously supplied into the vacuum chamber during the stability measurement. It was found that the plasma treatment etched the protruded CNTs, resulting in the uniform height of CNT tips. As a result, the stability was increased remarkably. It was also found that the stability of CNT paste emitter was improved by electrical aging and that the optimum condition for the aging was varied with the size of emitter.

• Journal of Chest Surgery
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• v.46 no.5
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• pp.383-387
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• 2013

Vacuum-assisted closure therapy is an alternative method for a massive subcutaneous emphysema treatment. It is easily applicable and shows rapid effectiveness in massive subcutaneous emphysema, intractable with chest tube drainage.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.138.1-138.1
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• 2013

We present the low temperature (${\leq}1,000^{\circ}C$) vacuum sublimation behavior of an e-beam evaporative deposited on a SiC film and a method to reduce the vacuum sublimation through an ion beam process. The density of the SiC film deposited using the e-beam evaporation method was ~60% of the density of the bulk source material. We found that the sublimation became appreciable above ${\sim}750^{\circ}C$ under $1.5{\times}10^{-5}$ torr pressure and the sublimation rate increased with an increase in temperature, reaching ~70 nm/h at $950^{\circ}C$ when the coated sample was heated for 5 h. When the film was irradiated with 70 keV N+ ions prior to heating, the sublimation rate decreased to ~23 nm/h at a fluence of $1{\times}10^{17}\;ions/cm^2$. However, a further increase in fluence beyond this value or an extended heating period did not change (decrease or increase) the sublimation rate any further.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.4
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• pp.191-196
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• 2003

For improvement of the wear performance of Ti alloy, vacuum-carburizing technique was tried for the first time using propane atmosphere. During the low pressure carburizing carbide was formed at the surface and carbon transfer was occurred from the carbide to the matrix. It was found that: (i) surface hardness increased with the reduction of operating pressure and time; (ii) optimum hardness distribution could be obtained with the proper choice of temperature and carbon flux control; and, (iii) case depth was largely influenced not by time but by temperature. The two steps process was recommended for obtaining thick case depth and high surface hardness of Ti alloy. For the low oxygen partial pressure, it was necessary to introduce additional CO gas to the atmosphere.Grain boundary oxidation and non-uniformity could be prevented.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.87-92
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• 2001

In this paper, high strength pressure vessel steels having the same chemical compositions were manufactured by the two different steel-making processes, such as vacuum degassing(VD) and electro-slag remelting(ESR) methods. After the steel-making process, they were normalized at $955^{\circ}C$, quenched at $843^{\circ}C$, and finally tempered at $550^{\circ}C$ or $450^{\circ}C$, resulting in tempered martensitic microstructures with different yielding strengths depending on the tempering conditions. Low-cycle fatigue(LCF) tests, fatigue crack growth rate(FCGR) tests, and fracture toughness tests were performed to investigate the fatigue and fracture behaviors of the pressure vessel steels. In contrast to very similar monotonic, LCF, and FCGR behaviors between VD and ESR steels, a quite difference was noticed in the fracture toughness. Fracture toughness of ESR steel was higher than that of VD steel, being attributed to the removal of impurities in steel-making process.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.84-90
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• 2004

A performance evaluation is made in terms of thrust, impulse bit. and specific impulses for a set of mono-propellant hydrazine thrusters producing 0.95 lbf of nominal thrust at an inlet pressure of 350 psia. With a brief description on the hot-firing test configuration and procedures. a typical data obtained from steady-state firing mode is given directly showing the variational behavior of propellant supply pressure, mass flow rate, vacuum condition, and thrust. The performance features are successfully compared to the reference criteria of 1-lbf standard mono-propellant rocket engine. Additionally. a statistical inter-thruster treatment is concisely depicted for the justification of selected thrusters as a grouped member of flight model for spacecraft propulsion system.

• Journal of the Korean Wood Science and Technology
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• v.27 no.3
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• pp.39-50
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• 1999

This research was carried out to investigate the development of fire-retardancy treatment technology and performance evaluation of fire-retardant treated plywoods. Radiata pine, keruing, dillenia, calophyllum and terminalia veneers were treated by normal(conventional) pressure soak(NPS) and vacuum-pressure-soak(VPS) using 20% water solution of diammonium phosphate. Then, 4.8mm thick, 3ply plywoods were fabricated with combination of fire-retardant treated, untreated or water-immersion types and several composition types of radiata pine and keruing veneers, i,e. the uniform and the mixed types in species composition, and the homogenious and the alternate layer types in veneer treatment. In composed species, the retention and the treatment effects of fire-retardant chemicals III radiata pine was still greater than those of keruing. The effect of VPS treatment was larger than that of NPS treatment, however, adhesive bonding strength and bending strength of plywoods treated by these two methods were not necessarily lowered, compared to those of untreated plywood. And also, fire endurance performance of the urea melamine resin-bonded plywood was greater than that of the phenol resin-bonded plywood. In result, the appropriate combination in veneer species and layer as well as alternate fire-retardant treatments would be more efficiently available in service.

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.99-102
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• 2004

In this work the electrical characteristics of organic thin film transistors with the surface-treated organic gate insulator have been studied. For the surface treatment of gate dielectric, Ar plasma was used. Pentacene and PVP were used as active and dielectric layers respectively. Pentacene was thermally evaporated in vacuum at a pressure of about $10^{-6}$ Torr and at a deposition rate of 0.5 $\AA$/sec. PVP was spin coated and cured at $100^{\circ}C$. before pentacene deposition. organic thin film transistors with surface-treated gate insulators have provided improved operation characteristics.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.219-248
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• 1989

The purposes of this study were to analyze the microstructural and compositional changes of metal surfaces following different conditions of preoxidizing heat treatment, to investigate the composition of metal oxides, and to evaluate the effect of preoxidation and removal of surface oxides on microstructure and diffusion profiles. The techniques of EDAX (energy-dispersive analysis of x-ray), ESCA (electron spectroscopy for chemical analysis), and EPMA (electron probe micro analysis) were used, along with SEM (scanning electron microscopy). The obtained results were as follows : 1. A surface of the specimen became rough and the amount of the metal oxides increased with increasing the heat treatment time and temperature and the partial pressure of oxygen. 2. At an air pressure of 28' vacuum, the higher the temperature and the longer the time of preoxidation, the higher Ni concentration was detected. 3. Cr concentration in the specimen heat treated with air was higher than that of with vacuum. 4. The oxides in the specimens were mainly composed of Ni and Cr oxides. On the globular growth particles, significant rises in Al concentration of Rexillium III and Ti concentration of Verabond were noted. 5. Atomic diffusion occurred at the ceramic-metal interface, furthermore the amount of the flux was increased with preoxidation heat treatment.