• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.29-30
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• 1999

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.05a
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• pp.67-68
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• 1998

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.11a
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• pp.37-38
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• 1998

• Journal of Power System Engineering
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• v.2 no.3
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• pp.41-48
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• 1998

This study was aimed at development of fabrication process of functionally graded materials(FGM), consisting of metal and ceramic by thermal spraying method. NiCrAIY/$Al_2O_3$ FGM were made by using plasma spraying onto the SS400 carbon steel substrate. And mechanical properties such as microhardness, thermal shock resistance and adhesive strength of the coating layer were investigated. Adhesive strength was evaluated by acoustic emission method. It was resulted that NiCrAIY/$Al_2O_3$ FGM made by thermal spraying method showed excellent thermal shock resistance and adhesive strength compared to the other lamellar structures of sprayed coatings and that AE is useful tool to evaluate the defect of thermal sprayed coating layer.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.1
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• pp.88-94
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• 2019

Increasing demands for esthetic dental treatment, zirconia, which has high mechanical and esthetic properties, had been applied more and more in clinics. Therefore, assessment of biocompatibility of zirconia is necessary. In this article, a review of in vivo studies of zirconia compatibility was performed. In vivo studies showed zirconia had great biocompatibility both on soft and hard tissue. Studies with various animals and patients reported high biocompatibility of zirconia. In terms of bone synthesis and bone adhesion, zirconia showed similar biocompatible properties to titanium. On the other hand, zirconia could be used as implant. For using as an implant, various methods of Hydroxyapatite (HA) coating had been suggested. Since HA coating on titanium implant showed some problems such as low bonding strength and degeneration of HA, HA-zirconia composite, HA-coated zirconia, and HA-zirconia functionally graded material (FGM) or intermediate layer of alumina had been proposed. These methods showed higher bonding strength and biocompatibility.

• Korean Journal of Materials Research
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• v.32 no.6
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• pp.293-300
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• 2022

This study investigated a graded-refractive-index (GRIN) coating pattern capable of improving the light extraction efficiency of GaN light-emitting diodes (LEDs). The planar LEDs had total internal reflection thanks to the large difference in refractive index between the LED semiconductor and the surrounding medium (air). The main goal of this paper was to reduce the trapped light inside the LED by controlling the refractive index using various compositions of (TiO₂)_x(SiO₂)_1-x in GRIN LEDs consisting of five dielectric layers. Several types of multilayer LEDs were simulated and it was determined the transmittance value of the LEDs with many layers was greater than the LEDs with less layers. Then, the specific ranges of incident angles of the individual layers which depend on the refractive index were evaluated. According to theoretical calculations, the light extraction efficiency (LEE) of the five-layer GRIN is 25.29 %, 28.54 % and 30.22 %, respectively. Consequently, the five-layer GRIN LEDs patterned enhancement outcome LEE over the reference planar LEDs. The results suggest the increased light extraction efficiency is related to the loss of Fresnel transmission and the release of the light mode trapped inside the LED chip by the graded-refractive-index.

• Structural Engineering and Mechanics
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• v.59 no.2
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• pp.227-241
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• 2016

A circular plate with constant thickness, finite radius and stiff edge lying on an elastic halfspace is considered. The half-space consists of a soft functionally graded (FGM) layer with arbitrary varying elastic properties and a homogeneous elastic substrate. The plate bends under the action of arbitrary axisymmetric distributed load and response from the elastic half-space. A semi-analytical solution for the problem effective in whole range of geometric (relative layer thickness) and mechanical (elastic properties of coating and substrate, stiffness of the plate) properties is constructed using the bilateral asymptotic method (Aizikovich et al. 2009). Approximated analytical expressions for the contact stresses and deflections of the plate are provided. Numerical results showing the qualitative dependence of the solution from the initial parameters of the problem are obtained with high precision.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.44-51
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• 1995

Homogeneous, compositionally graded, and superlattice-like silicon oxynitride(SiON) dielectric layers, with the refractive index varying from 1.46 to 2.05 as a function of film thickness, were grown by computer-controlled plasma-enhanced chemical vapor deposition (PECVD) using silane, nitrogen, and nitrous oxide reactant gases. An antireflection(AR) coating and thin-film electroluminescent(TFEL) devices with multiple dielectrics were designed and fabricated using real time control of reactant gases of the PECVD system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.102.2-102.2
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• 2012

Different layers of zirconium nitride (ZrN) and hydroxyapatite (HA) coatings were prepared on cp Ti substrate for biomedical applications. The main idea is to improve the mechanical strength as well as the biocompatibility of the coating. ZrN is known for its high mechanical strength, corrosion resistance. HA is well known for its biocompatibility properties. Hence, in this study, both materials were coated on a cp Ti substrate with bottom layer with ZrN for good bonding with substrate and the top layer with HA for induce bioactivity. Middle layer was formed by a composite of HA and ZrN. Detail analyses of the layered coatings for its structural, morphological, topographical properties were carried out. Then the mechanical property of the layered coatings was analyzed by nanoindentation. Biomimetic growths of apatite on the functionally graded coatings were determined by simulated body fluid method. This study provides promising results to use this kind of coatings in biomedical field.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.87-88
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• 2006

Ceramic-Metal Functionally Graded Materials (FGM) are of great interest for application as Thermal Barrier Coating (TBC) or Wear Resistant Coating (WRC). Spark Plasma Sintering (SPS) is a promising techniques for time-saving consolidation of laminated/graduated powder systems: SPS is a pressure-assisted electrical sintering method which directly applies a pulsed DC current as heat source. In the present work, production of $Al_2O_3-Ni$ FGMs by means of Spark Plasma Sintering is considered; effect of sintering condition on density, hardness and fracture toughness is studied. Problems correlated to this new processing technology are discussed.