• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.221.1-221.1
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• 2015

The vapor-liquid-solid (VLS) method, where the "liquid" catalytic droplets collecting atoms from vapor precursors build the solid crystal layers via supersaturation, is a ubiquitous technique to synthesize 1-dimensional nanoscale materials. However, the lack of fundamental understanding of chemical information governing the process inhibits the rational route to the structural programming. By combining the in situ or operando IR spectroscopy with post-growth high resolution electron microscopy, we show the strong correlation between the surface chemical species concentration and nanowire structures. More specifically, the critical role of surface adsorbed hydrogen, generated from the decomposition of Si2H6 precursor on the interplay between nanowire / kinking and the defect propagation is demonstrated. Our results show that adsorbed hydrogen atoms are responsible for selecting -oriented growth and indicate that a twin boundary imparts structural coherence. The twin boundary, only continuous at / kinks, reduces the symmetry of the trijunction and limits the number of degenerate directions available to the nanowire. These findings constitute a general approach for rationally engineering kinking superstructures and also provide important insight into the role of surface chemical bonding during VLS synthesis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.189-192
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• 2003

The Electro-thermal Explosion Coating (EEC) technique is a new surface treatment technology emerged in recent years. It uses an electrical discharge (with very high voltage from 5 to 30 kV or more) to produce a pulse current with large density inside the material to be deposited, the metal wire undergo the heating, melting, vaporization, ionization and explosion processes in a very short time (from tens ns to several hundreds ${\mu}s$), and the melted droplets shoot at the substrate with a very high velocity (3000 - 4500 m/s), so that the coating materials can be deposited on the surface of the substrate. Coatings with nano-size grains or ultra- fine grains can be formed because of rapid solidification (cooling rate up to $10^6-10^9\;k/s$). Surface of the substrate (about $1-5{\mu}m$ in depth) can be melted rapidly and coatings with very high bonding strength can be obtained.

• Journal of the Korean Wood Science and Technology
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• v.36 no.2
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• pp.56-62
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• 2008

The surface and edge structure of OSB is defined by surface strand orientation and strand mat thickness variation parallel to the length of the panel using video-microscope. The bending strength of OSB was correlated with surface strand orientation and decreased with increasing the orientation angle in the direction parallel to length of the panel. Average strand mat thickness variation parallel to the length of the panel did not influence the bending strength, but the bonding characteristics among the outermost strands affects the bending strength of OSB. Hankinson formula can be used to predicts the MOE according to strand orientation in the surface of OSB, and more precise strand alignment and reducing thickness variation should be important in the structural performance of OSB panels.

• Proceedings of the Korean Vacuum Society Conference
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• 2001.07a
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• pp.70-70
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• 2001

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.97-102
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• 2003

Multi-channel images of 11-MUA(11-Mercaptoundecanoic acid) and 11-MUOH(11-Mercaptoundecanol) self-assembled monolayers were obtained by using two-dimensional surface plasmon resonance (SPR) absorption. The patterning process was simplified by exploiting direct photo-oxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter in the visible region, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each point on the sensor surface (at a fixed incident angle) enables us to discriminate the monolayer thickness in nanometer scale. Furthermore, there is no signal degradation such as photo bleaching or quenching, which are common in the detection methods based on fluorescence.

• Journal of Technologic Dentistry
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• v.39 no.1
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• pp.43-52
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• 2017

Purpose: Physical and chemical properties of gold is most suitable to be restored of teeth to its original state. Recently zirconia was used instead of gold because of esthetical and intimacy of human body. Because of high strength and high abrasion resistance of zirconia, all zirconia artificial tooth lead to wear the original tooth of opposite site. To preserve this original tooth, zirconia artificial tooth covered with dental ceramic glass was used. When joining the zirconia core and dental ceramic glass, difference of their thermal expansion coefficient and wetting ability is generated the residual stress at interface lead to crack. In order to solve this problem, intermediate layer what is called zir-liner was imported to decrease the residual stress and increase the bonding strength. Methods: In this study, to identify the optimum conditions for manufacturing process, various methods to rough the surface of zirconia core were adopted, and vary the thickness of interlayer, and analyzed bond strength. Results: Bond strength of sanding specimens group showed higher than that of non-sanding specimens group, and once applied intermediate layer with sanding specimens showed highest bond strength with 28 MPa. SEM photomicrographs of zirconia cores fired at $1500^{\circ}C$ showed parallel straight lines in sanding and pockmarked surface in blasting surfaces as abrasion traces. Observation of the destruction section after shear test by SEM were carried out. Liner applied non-sanding group and non-liner applied sanding group all showed interfacial crack. Sandblasting group with non-liner showed remained dental ceramic glass on the surface of zirconia. Sandblasting group with once applied liner showed partially remained liner and dental ceramic glass on the surface of zirconia. XRD analysis revealed that sandblasting group showed higher monoclinic peaks than other specimens group and this result was due to the high collision energy for stress induced phase transformation. Conclusions: A study on the improvement of bonding strength between zirconia and dental ceramic glass steadily carried out for the future to practical use.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.93-100
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• 2021

Copper sheets has been used widely in electric and electron industry fields because they have good electric and heat conduction property of the material. And, in order to bond copper material, a kind of soldering process is generally used. But, because it is difficult to bond by soldering between overlapped thin copper sheets, so, another kind of brazing bonding process can be used in that case. But, because the brazing process needs wide bonding area, it needs heat treatment process in electric furnace. Generally, for spot welding of sheets, a conventional electric Resistance Spot Welding process(RSW) has been used, it has welding characteristics using contact resistance heating induced by electric current flow between sheets. But, because copper sheets has the low electric resistance, it is difficult to weld by electric resistance spot welding. So, in this study, an electric Resistance heated Surface Friction Spot Welding process(RSFSW) is suggested and is testified for the spot welding ability of thin copper sheets. It is known from the experimental results and simulation that the suggested spot welding process will be able to improve the spot welding ability of copper sheets by the combined three kinds of heating generated by surface friction by rotating pin, and conducted from heated steel electrode, and generated by contact resistance of electricity.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.369-375
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• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• Journal of Technologic Dentistry
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• v.41 no.4
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• pp.279-285
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• 2019

Purpose: The dental CAD / CAM system has been popular with the development of the digital dental industry. Zirconia is a typical material in dental CAD / CAM systems. Zirconia crowns are classified into single layer and double layer. This study is about the double layer crown of zirconia. The surface roughness, bond strength and fracture patterns of the zirconia surface were observed. Methods: Zirconia blocks were cut using a low speed cutter. Sintered to form a plate shape (6mm × 6mm × 3mm). The prepared specimens were surface treated in four ways. Surface roughness and bond strength were measured. And the fracture pattern was observed. Results: Result of surface treatment of zirconia. The surface roughness test results were as ET 2.87 ㎛, ST 2.67 ㎛, LT 2.44 ㎛, AT 2.41 ㎛, CN 2.08 ㎛ order. Bond Strength results were as LT 25.09 MPa, AT 23.27 MPa, ST 21.27 MPa, ET 21.09 MPa, CN 16.12 MPa order. Fracture patterns showed cohesive failure of 25-50% of the bond area. Conclusion: Surface roughness, bond strength and fracture pattern of the zirconia surface were observed. Etching the surface treatment of zirconia materials has been shown to affect the surface roughness. Zirconia special binder treatment has been shown to affect the bond strength improvement.

• Restorative Dentistry and Endodontics
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• v.32 no.5
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• pp.426-436
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• 2007

The objective of this study is to evaluate the effect of an additional application of bonding resin on the bond strength of resin luting cements in both the light-cure (LC) and self-cure (SC) modes by means of the ${\mu}TBS$ tests. Three combinations of One-Step Plus with Choice, Single Bond with Rely X ARC, and One-Up Bond F with Bistite II were used. D/E resin and Pre-Bond resin were used for the additional application. Twelve experimental groups were made. Three mandibular $3^{rd}$ molars were used in each group. Indirect composite blocks were cemented on the tooth surface. $1\;{\times}\;1\;mm^2$ dentin-composite beam for ${\mu}TBS$ testing were made and tested. When total-etching dentin adhesives were used, an additional application of the bonding resin increased the bond strength (P < 0.05). However, this additional application didn't influence the bond strength of self-etching dentin adhesives (P > 0.05). In conclusion, the results suggest that an additional application of the bonding resin increases bond strength and enhances quality of bonding when using total-etching dentin adhesives.