• Carbon letters
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• v.11 no.2
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• pp.107-111
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• 2010

We prepared the amine epoxy adducts (AEA)/thin multiwalled carbon nanotubes (TWCNTs) composite particles using nonsolvent based methods including dry mechano-chemical bonding(MCB) process and supercritical fluid (SCF) process. The resulting TWCNTs/AEA composite particles have been used as curing agents for urethane modified bispheol A type epoxy resin. The thermal, thermomechanical properties of the epoxy resins cured with TWCNTs/AEA composite particles were measured by DMA and the dispersion of CNT was characterized by SEM. Because of high degree of CNT dispersion, thermal and mechanical properties of the epoxy resin cured with TWCNTs/AEA composite particles prepared by SCF process are better than those cured with mechano-chemically prepared TWCNTs/AEA composite particles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.67-73
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• 2017

Recently, macroporous ceramic materials with high electrical conductivity and mechanical strength are urgently needed for semiconductor and display manufacturing devices. In this work, we obtained electro-conducting macroporous aluminosilicate ceramics having surface resistivity of 108~1,010 ohm by dispersing electro-conducting carbon in ceramic matrix. By addition of 0.5~3.0 wt% frit glass, chemical bonding between grains was strengthened, and flexural strength was enhanced up to 160 MPa as a result. We evaluated the characteristics of present ceramics as vacuum chuck module for liquid crystal display display manufacturing devices.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.3
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• pp.518-536
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• 1997

The purpose of the present study was to analyze the pulpal tissue reactions to several capping materials. 8 adult Mongrel dogs and 4 different capping materials (G I : Calcium hydroxide, G II : Bonding resin, G III : Glass ionomer liner, G IV : Bioactive ceramic) we-reused in the study. The results can be summarized as follows : 1. The formation of hard tissue barrier was observed to begin after 2 weeks in all groups with various forms or positions. 2. According to the result of statistical analysis, G I and G IV showed significantly higher degree of inflammation than G II, G III in 1-week samples(p<.05). And in 2-week samples, G I showed higher degree of inflammation than G II, G IV with statistical significance(p<.05). Howere, these inflammatory reactions have gradually dimiished with time resulting in negligible difference between groups. 3. No bacterial penetration was observed in any group. 4. Hard tissue formation was evident in all groups after 2 weeks regardless of material type in this experiment. Conclusion can be drawn from the above-mentioned results that the perfect marginal sealing after pulp capping procedure is thought to be the most important factor in determining the propgnosis of direct pulp capping.

• Composites Research
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• v.28 no.3
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• pp.112-117
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• 2015

Mechanical properties of nonwoven alfa fiber based reinforced biocomposite were evaluated to assess the possibility of using it as a new material in engineering applications such as orthopedic application. Samples were fabricated by needle punching, thermal bonding and Hydroentanglement, by blending alfa fibers with wool fibers or Polypropylene fibers. The mechanical properties were tested and showed that the nonwoven NW3 (alfa fiber/PP/PLA, with hydroentanglement) is the best. It has a value of stress at break of 1.94 MPa, a strain of 54.2% and a young's module of 7.95 MPa, in a production normal direction. A biocomposite has been made with NW3 mixed with PMMA matrix. The use of nonwoven based alfa fiber in reinforcing the composite material increases its rigidity and the tensile strength; the elongation was found to be 1.53%, the Young's Module of 1.79 GPa and the tensile at break of 15.06 MPa. Results indicated that alfa fibres are of interest for low-cost engineering applications and can compete with glass fibres in orthopedic application.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.04a
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• pp.74-79
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• 2000

In an attempt to estimate the wetting properties of wettable metal layers by wetting balance method, an analysis of wetting curves of the coating layer was performed. Based on the analysis, wetting properties of UBM-coated Si-plate were estimated by the new wettability indices. The wetting curves of the one and both sides-coated UBM layers have the similar shape and show the similar tendency to the temperature. So the wetting property estimation of one side coating is possible with wetting balance method. For UBM of Si-chip, Cr/Cu/Au UBM is better than Ti/Ni/Au in the point of wetting time. At general reflow temperature, the wettability of high melting point solders(Sn-Sb, Sn-Ag) is better than that of few melting point ones(Sn-Bi, Sn-In).The contact angle of the one side coated plate to the solder can be calculated from the farce balance equation by measuring the static state force and the tilt angle.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.119-128
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• 2007

Although there are many different ways that restorations can be made, it can be said that the biocompatibility of abutment and crown is very important in this experiment. When placed in the actual oral cavity, the differences were obvious. Compared to In-ceram Aluminium, the structure that is obtained after firing reveals a particularly homogeneous distribution of the crystal and glass phase. The In-ceram aluminium system had many problems, such as having weak tensile strength, and having low bonding strength due to the shrinking that occurs after firing. Because of the opaque finish of the metal frame, the two may look similar from the outside, but it is evident that there are differences between using a metal frame and In-ceram. VITA VM9 has been designed as a special ceramic featuring a fine structure or stabilized Zro2 substructures, and so the VITA VM9 excels in its light refraction and reflection behavior, which is similar to natural teeth. It also has outstanding chemical balance, which presents advantages such as considerably reduced accumulation of plaque on the ceramic surface.? This ultimately results in easier care and cleaning for the patient.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.26-29
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• 2004

High density plasma fluorinated silicate glass (HDP FSG) is used as a gap fill film for metal-to-metal space because of many advantages. However, FSG films can cause critical problems such as bonding issue of top metal at package, metal contamination, metal peel-off, and so on. It is known that these problems are caused by fluorine penetration out of FSG film. To prevent it, FSG capping layers such like SRO (Silicon Rich Oxide) are needed. In this study, their characteristics and a capability to block fluorine penetration for various FSG capping layers are investigated. Normal stress and High stress due to denser film. While heat treatment to PETEOS caused lower blocking against fluorine penetration, it had insignificant effect on SiN. Compared with other layers, SRO using ARC chamber and SiN were shown a better performance to block fluorine penetration.

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.155-162
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• 2018

A smart glass fiber reinforced polymer (SMFRP) reinforcing bar with a fiber Bragg grating (FBG) sensor was fabricated using a pultrusion technique, while ribs were formed to improve bonding between concrete and SMFRP. Then, strain of SMFRP bars were measured for a uniaxial tension test of an SMFRP bar, and a four-point bending test of concrete beams reinforced with SMFRP bars. The results of a uniaxial tension test illustrate that the strain obtained from an FBG sensor agrees well with that obtained from electrical resistance strain gauge (ERSG). Additionally, concrete beams reinforced with SMFRP bars were fabricated, and actual flexural test were performed while the strain of with an FBG sensor was compared with that of ERSG. The experimental results demonstrate that SMFRP bars can be used as reinforcement of concrete member while providing deformation information. Furthermore, SMFRP bars may provide stronger durability and smart monitoring to reinforced concrete members under corrosive environments during a service life.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.402.1-402.1
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• 2014

Photonic force microscopy (PFM) is an optical tweezers-based scanning probe microscopy, which measures the forces in the range of fN to pN. The low stiffness leads proper to measure single molecular interaction. We introduce a novel photonic force microscopy to stably map various chemical properties as well as topographic information, utilizing weak molecular bond between probe and object's surface. First, we installed stable optical tweezers instrument, where an IR laser with 1064 nm wavelength was used as trapping source to reduce damage to biological sample. To manipulate trapped material, electric driven two-axis mirrors were used for x, y directional probe scanning and a piezo stage for z directional probe scanning. For resolution test, probe scans with vertical direction repeatedly at the same lateral position, where the vertical resolution is ~25 nm. To obtain the topography of surface which is etched glass, trapped bead scans 3-dimensionally and measures the contact position in each cycle. To acquire the chemical mapping, we design the DNA oligonucleotide pairs combining as a zipping structure, where one is attached at the surface of bead and other is arranged on surface. We measured the rupture force of molecular bonding to investigate chemical properties on the surface with various loading rate. We expect this system can realize a high-resolution multi-functional imaging technique able to acquire topographic map of objects and to distinguish difference of chemical properties between these objects simultaneously.

• Korean Journal of Materials Research
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• v.17 no.7
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• pp.376-381
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• 2007

Fluorine-doped tin oxide (FTO) thin film was coated on aluminosilicate glass at $450^{\circ}C$ by spray pyrolysis method. In the range of 0-2.7 molar ratio of F/Sn, the variations of electrical conductivity and visible light transmission were investigated. At the F/Sn ratio of 1.765, the film showed the lowest electrical resistivity value of $3.0{\times}10^{-4}{\Omega}\;cm$, the highest carrier concentration of $2.404{\times}10^{21}/cm^3$, and about $8\;cm^2/V{\cdot}sec$ of electronic mobility. The FTO film showed a preferred orientation of (200) plane parallel to the substrate. X-ray photoelectron spectroscopy analysis results indicated that the contents of $Sn^{4+}-O$ bonding are the highest at 1.765 of F/Sn molar ratio.