• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.65-71
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• 2008

The use of titanium in the field of dentistry has increased, due to their excellent biocompatibility, appropriate mechanical properties, corrosion-resistance and low price. However, many difficulties with the use of titanium for metal-ceramic crowns remain to be solved. The objective of this study was to evaluate the influence of surface modifications on the bonding characteristics of specific titanium porcelain bonded to cast titanium. The surfaces of Titanium were prepared with 4 test groups, i) sandblasted with particles of different size, ii) sandblasted after treated oxidization and oxidized after sandblast. We observed the bond strength and node aspect of titanium and ceramic, and respect to the methods of modifying surface of titanium by the test of mean roughness of surface, Scanning Electron Microscope, and 3-point flexural bend test. The results show that, 1. The specimens, which treated oxidization after process of sandblast with particles of 50um size, were the better for the bond strength in comparison with other specimen. 2. The specimen with process of sandblasting after oxidization treatment were the better for stability of the bond strength. 3. The wettability of titanium surface affect the bond strength.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.330-341
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• 1999

An experimental study for the two types of burners used in the non-oxidizing direct fired furnaces of the heat treatment process for the cold rolled plate has been carried out to investigate the combustion characteristics and the oxidization of the surface of steel plate. A steep temperature gradient and entrainment of residual oxygen were found near the heating surface in the flame of the nozzle mixing burner which has strong swirl velocity component. It was concluded that the elimination of the residual oxygen and the increase of the temperature of combustion gas on the heating surface are needed to enhance the performance of the burners for application to the non-oxidizing direct fired furnaces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.83-88
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• 2004

Micro wires manufactured by the straightening progress are widely used in bio-medical and semi-conductor fields. In this study, we have developed a novel straightener which uses the direct heating method for straightening. In order to avoid the surface oxidization, during the heating process, we supplied the inert gas(Ar) and examined the effect of the gas flow rate. The effect of the tension and the current applied to the tungsten micro wires were thoroughly studied. From various experiments, it was found that when the tension is $500{\sim}600gf$ and the current is about 1.5A, we obtained higher straightness(${\approx}1{\mu}m/1000{\mu}m$) and roundness ($<{\pm}2{\mu}m/100{\mu}m$).

• Journal of Magnetics
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• v.7 no.3
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• pp.63-71
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• 2002

Three fabrication techniques for forming thin barrier layer with uniform thickness and large barrier height in magnetic tunnel junction (MTJ) are discussed. First, the effect of immiscible element addition to Cu layer, a high conducting layer generally placed under the MTJ, is investigated in order to reduce the surface roughness of the bottom ferromagnetic layer, on which the barrier is formed. The Ag addition to the Cu layer successfully realizes the smooth surface of the ferromagnetic layer because of the suppression of the grain growth of Cu. Second, a new plasma source, characterized as low electron energy of 1 eV and high density of $10^{12}$ $cm^{-3}$, is introduced to the Al oxidation process in MTJ fabrication in order to reduce damages to the barrier layer by the ion-bombardment. The magnetotransport properties of the MTJs are investigated as a function of the annealing temperature. As a peculiar feature, the monotonous decrease of resistance area product (RA) is observed with increasing the annealing temperature. The decrease of the RA is due to the decrease of the effective barrier width. Third, the influence of the mixed inert gas species for plasma oxidization process of metallic Al layer on the tunnel magnetoresistance (TMR) was investigated. By the use of Kr-O$_2$ plasma for Al oxidation process, a 58.8 % of MR ratio was obtained at room temperature after annealing the junction at $300{^{\circ}C}$, while the achieved TMR ratio of the MTJ fabricated with usual Ar-$0_2$ plasma remained 48.4%. A faster oxidization rate of the Al layer by using Kr-O$_2$ plasma is a possible cause to prevent the over oxidization of Al layer and to realize a large magnetoresistance.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.362-374
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• 2007

Statement of problem. The intial stability for osseointegration of implant has been an interesting factor. Especially, in the case of poor bone quality or immediately loaded implant, various strategies have been developed focusing on the surface of materials to improve implant fixation to bone. The microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Purpose. The aims of this study are to perform a histologic and histomorphometric comparison of the healing characteristics of three different surfaces and the comparison of resonance frequency analysis (RFA) values measured by $Osstell^{TM}$ and perio-test values (PTV) measured by Periotest. Material and methods. A total of 24 screw titanium implants (Dentium Co., Seoul, Korea) with 6mm in length and 3.4mm in diameter, were placed in the mandible of 4 beagle dogs. Implants were divided into three groups following the surface treatment methods: Group I is machined(control group). Group II is anodically oxidized. Group III is coated 500nm in thickness with hydroxyapatite(HA) by ion beam assisted deposition(IBAD) on the anodized oxidization. Bone blocks from 2 dogs were caught after 3 weeks of covered healing and another blocks from 2 dogs after 6 weeks. RFA values and PTV were measured right after insertion and at 3 and 6weeks. Histomorphometric analysis was made with Kappa Image Base System to calculate bone-to-implant contact (BIC) and bone area inside the threads. Pearson's correlation analyses were performed to evaluate the correlation between RFA and PTV, BIC and bone area ratio of three different surfaces at 3 and 6 weeks. Results. 1) In all surface treatment methods, the RFA values decreased and the PTV values increased until 6 weeks in comparison to initial values. 2) At 3 weeks, no significant difference was found from bone-to-implant contact ratio and bone area ratio of three different surface treatment methods(P>0.05). However, at 6 weeks, different surface treatment methods showed significantly different bone-toimplant contact ratio and bone area ratio(P<0.05). 3) In the implants with the IBAD on the anodic oxidization, significant difference was found between the 3 weeks and the 6 weeks bone area ratio(P<0.05). 4) Correlation was found between the RFA values and the bone area ratio at 3 and 6 weeks with significant difference(P<0.05). Conclusions. These results indicate that the implants with the IBAD on the anodic oxidization may have a high influence on the initial stability of implant.

• Korean Journal of Materials Research
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• v.13 no.11
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• pp.742-748
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• 2003

The structural parameters such as Lc, La and d of $CO_2$activated isotropic carbon fibers(ACFs) were obtained from XRD in order to understand a development mechanism of micropores. And the structural parameters were compared with specific surface area(SSA) data. The $d_{002}$, Lc, and La of the original fiber were measured to be 4.04$\AA$, 6.2$\AA$, and 23.6$\AA$, respectively. Carbonization of outer-parts and oxidization of inner-parts of the original fibers were far from completeness. It was observed that the structural changes of the ACFs during activation take place severely, therefore the carbonization and the oxidization of the fibers take place simultaneous with pore developments. The $d_{002}$ of the ACFs was increased to be 2.80$\AA$, and the La of the ACFs was decreased to be 17.0$\AA$ by activation. It was shown that the pores are developed continuously from the outer-parts to the inner-parts of the fibers, therefore the SSA increases as a result of the development of pores fully to the inner-parts of the fiber when the burn-off degree was over :39%. It seems that the (002) planes of crystallites contribute to the micropore wall related to the super high SSA.SSA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.218-224
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• 2016

The surface of Mg alloy, AZ31 and AZ91, were treated by PEO (plasma electrolytic oxidation) in Na-P system electrolyte, with different applied voltage and time. Thickness, roughness and X-ray crystallographic analysis revealed several results. The more applied time and voltage of PEO treated, the thicker oxidized surface coating layer were covered. And surface roughness increased with the thickness of oxidized layer. It was thought that when oxide layer grew, resistivity and breakdown voltage increased with the thickness of layer, and then, the energy of micro plasma need to be higher then before. So, it made craters and pores of surface become greater, which were responsible for the coarse surface.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.43-46
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• 2004

Multi-walled carbon nanotubes (MWNTs) produced by chemical vapor deposition were treated with acidic solution for purification and oxidization of CNTs. The surface modification of the oxidized CNTs was achieved by amine treatment and oxygen plasma treatment. The functionalized CNTs were embedded in the epoxy resin by sonication method and the resulting composite was investigated by FESEM. Rheological and mechanical properties of nanocomposites were measured by AR2000 and Instron. The rheological properties and dispersion of modified CNTs/epoxy composites were improved as CNTs were modified, because the modification of CNTs led to a improvement interaction between the CNTs and the epoxy resin. In addition to this, mechanical properties are also improved because of the effective stress transfer between the CNTs and the polymer.

• Transactions of Materials Processing
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• v.18 no.4
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• pp.304-309
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• 2009

Quenchable boron steel is a new type of high strength steel to reduce the weight of automobiles and maintain the safety conditions. Quenchable blanks can be hot-stamped and hardened in a water-cooled tool to achieve high strength. In this paper, new alloy for hot stamping is designed based on requirement of mechanical properties and two types of surface coating are investigated in viewpoints of oxidization and exfoliation. An automotive part of center pillar is manufactured by hot-stamping using Al-Si coated sheet. The performance of developed part is compared by static compression test and side impact crash test.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1185-1194
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• 2022

The maintenance of condenser main pipe is the key to achieve film-forming amine maintenance effectiveness. In this work, oxygen content, pH and temperature of the solution were controlled to simulate the condition of condenser main pipe, and magnetite coated carbon steel sample was prepared by pre-oxidization. CAM was used to characterize the hydrophobicity of film formed samples. Hydrophobic film was formed on pre-oxidized carbon steel samples when octadecylamine concentration reaches 20 mg/kg. SEM, EDS, EIS, and PD were used to characterize the influence of octadecylamine concentration on maintenance effectiveness. It was found that the maintenance effectiveness was enhanced and the corrosion rate was suppressed with the increase of octadecylamine concentration. FIB and TEM were used to detect the adsorbed octadecylamine film thickness founding that octadecylamine adsorbed onto the surface of pre-oxidized carbon steel by multi-layer adsorption mechanism.