• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.78-78
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• 2017

Pure Titanium and alloy have been widely used in dental implants and orthopedics due to their excellent mechanical properties, biocompatibility and corrosion resistance. However, due to the biologically inactive nature of Ti metal implants, it cannot bind to the living bone immediately after transplantation into the body. In order to improve the bone bonding ability of titanium implants, many attempts have been made to alter the structure, composition and chemical properties of titanium surfaces, including the deposition of bioactive coatings. The PEO method has the advantages of short experiment time and low cost. These advantages have attracted attention recently. Recently, many metal ions such as silicon, magnesium, zinc, strontium, and manganese have received attention in this field due to their impact on bone regeneration. Silicon (Si) in particular has been found to be essential for normal bone and cartilage growth and development. Zinc (Zn) plays very important roles in bone formation and immune system regulation and promotes bone metabolism and growth. Manganese (Mn) is an essential trace metal found in all tissues and is required for normal amino acid, lipid, protein and carbohydrate metabolism. The objective of this work was research on the corrosion behavior of Si, Zn and Mn-doped hydroxyapatite on the PEO-treated surface. Anodized alloys was prepared at 270V~300V voltage in the solution containig Zn, Si, and Mn ions. Ion release test was carried out using potentidynamic and AC impedance method in 0.9% NaCl solution. The surface characteristics of PEO treated Ti-6Al-4V alloy were investigated using XRD, FE-SEM, AFM and EDS.

• Journal of the Korean Applied Science and Technology
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• v.29 no.4
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• pp.618-625
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• 2012

In this study, prepared synthesis waterborne acrylic resin and water soluble milk casein resin. And than extent of casein contents in acrylic resin. We measured property of these samples by Lamb leather which is coated by acrylic-casein resins. According to measure data for solvent resistance, WAR resin and Hybrid resins had good property. Among this result knew that increase of casein constant did not influence to big change of hybrid resin property. As test of tensile strength, WAR had lowest strength($1.399kg_f/mm^2$) and WAC-3 had highest strength($1.426kg_f/mm^2$). Also we knew that best property of abrasion was WAC-3(69.774 mg.loss). In elongation case, WAR had best property(820%) in this experiment.

• Textile Coloration and Finishing
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• v.27 no.4
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• pp.334-339
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• 2015

Polyketone fiber, a newly developed high strength fiber, has a tenacity and modulus similar to the paramid fiber, and can be used for reinforcing mechanical rubber goods(MRG), such as tires, hoses, and technical textiles. In addition, aliphatic polyketone, which has excellent strength, modulus, chemical stability and reasonable price, is being developed only in South Korea. It will be expected for replacement of super fiber such as aramids and increasing the technical textile market share. This paper surveys the mechanical properties of polyketone fiber yarn for technical textiles. For this purpose, two kinds of yarns are prepared, mechanical properties of coated and uncoated polyketone yarns such as tensile strength, elongation and modulus were examined before and after weather resistance test(temperature $60^{\circ}C$, humidity 60%, amount of power $0.67w/m^2$). The differences of mechanical properties between uncoated and coated yarns for high functional technical textiles and composite materials are estimated through this study.

• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.547-556
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• 2011

The primary factors affecting concrete sulfate resistance are the chemical composition of the Portland cement, and the chemistry and quantity of mineral admixtures. To investigate the effect of those on the sulfate attack, the testing program involved several different mortar mixes using the standardized test, ASTM C1012. Four different cements were evaluated, including one Type I cement, two Type I-II cements, and one Type V cement. Mortar mixes were also made with mineral admixtures, as each cement was combined with three different types of mineral admixtures. One Class F fly ash, one Class C fly ash, and one ground granulated blast furnace slag (GGBFS) were added in various percent volumetric replacement levels. Expansion measurements were taken and investigated with the expansion criteria recommended by ASTM.

• Journal of Adhesion and Interface
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• v.6 no.3
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• pp.19-25
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• 2005

Synthetic rubber based pressure-sensitive adhesives (PSAs) usually containing SIS or SBS block copolymer, tackifier, plasticizer, and other additives are now widely used on various applications. As these PSAs are physically crosslinked and can be applied without the use of solvent, they are thermally processable and environmentally friendly. However these PSAs cannot be used in high temperature applications and in applications where solvent and chemical resistance properties are required. We developed the PSA adding UV curable system, such as thiol-ene system, to increase adhesion properties at elevated temperature. The adhesion properties such as probe tack, peel strength, shear adhesion failure temperature (SAFT) were evaluated. The probe tack test was conducted with varying probe materials and coating thickness of PSAs. Using the contact angle, the surface property of the cured PSAs was also observed.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.101-104
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• 2008

The cost of repairing the deterioration of concrete structures due to corrosion of the reinforcement steel has been the prominent figure in the maintenacne of the reinforced-concrete infrastructures. As an alternative material to steel reinforcement, the use of Fiber Reinforced Polymer (FRP) bar in concrete is being actively studied for the high resistance of chemical environment and high strength to weight ratio properties of FRP. However, there remain various aspects of FRP properties that still need to be studied before the standard design criteria can be established. One of the imminent issues is the bond between FRP and concrete. In this study, the bond-behavior of FRP bars in concrete is investigated via the pullout test with three varying parameters: surface condition of FRP bars, concrete compression strength, and cyclic loading patterns. As a result of experiment, the bond strength of GFRP increased with the concrete compression strength increasing and decreased with applying cyclic load.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.266-270
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• 2004

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine because it has excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing jiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC/SiC composites by hot pressing method. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method in Ar atmosphere at $1800^{\circ}C$ under 20MPa using $Al_2O_3,\;Y_2O_3\;and\;SiO_2$ as sintering additives in order to low sintering temperature and sintering pressure. The starting powder was high purity $\beta-SiC$ nano-powder with all average particle size of 30mm. The characterization of LPS-SiC was investigated by means of SEM and three point bending test. Base on the composition of sintering additives-, microstructure- and mechanical property correlation, tire compositions of sintering additives are discussed.

• Tuberculosis and Respiratory Diseases
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• v.41 no.6
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• pp.651-657
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• 1994

Asbestos is widely used in the textile, asbestos cement, construction products, friction material, paper products, insulation products, chemical and plastic products because of its heat resistance, flexibility, tensile strength, and texturability. It is now generally recognized that longterm and excessive inhalation of asbestos dust causes asbestosis, lung cancer, malignant mesothelioma and malignancies in other organs such as cancer of gastrointestinal tract, leukemia, lymphoma. Although eighty thousand tons of asbestos has been annually consumed since 1979 in korea, it has not been reported asbestos and lung cancer by asbestos dust so far, while a case of mesothelioma was officially diagnosis as a occupational disease at 1993. We experienced firstly a case of asbestosis and lung cancer caused simultanously by occupational asbestos exposure 11 years, which was confirmed by chest x-ray, pulmonary function test, chest CT and HRCT, bronchoalveolar lavage, and gallium scan. And so We present a case of asbestosis, pleural effusion and lung cancer with a review literature.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.929-932
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• 2008

The unsaturated polyester(UP) and epoxy resin have a superior material properties and a chemical resistance using sewerage pipes rehabilitation. However, UP and epoxy have not a low temperatures harding, the requirement $8{\sim}11$ hours long times harding and heating system used by reinforcement liner. This study is to evaluate the effects of low temperature harding properties methyl methacrylate(MMA) monomer using expanded polystyrene(EPS) in addition of initiator and promoters. From the test result, viscosity tends to increase with increasing EPS contents. However, harding time change of the MMA resins which it follows in addition of the initiator and promoter.