• 한국세라믹학회지
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• 제30권10호
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• pp.829-837
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• 1993

Chemically and geometrically homogeneous mixing of Si3N4 powders with sintering additives(YAG, 3Y2O3$.$5Al2O3) was attempted via coprecipitation method. X-ray dot maps for the additive elements(Al and Y) showed that the additives are evenly distributed in the powder mixture prepared by coprecipitation method(CP). TEM observation of the coprecipittion-treated Si3N4 powders revealed that they are covered with extremely fine crystallites of additive. The shift in isoelectric point(IEP) of Si3N4 powders from pH 6.7 to pH 7.9 after coprecipitation mixing gave another evidence for coating of Si3N4 powders with YAG additives. SIMS analysis for composition on the surface and in the matrix of mixed powders showed that the YAG additives are highly enriched on the surface of coprecipitation-treated Si3N4 powders. Especially when a small amount of additive was used, the effect of homogeneous additive distribution on densification was preceptible: After pressureless-sintering of powder compacts containing 5 mol% YAG at 1800$^{\circ}C$ for 0.5h, a sintered density of 96.5% theoretical was obtained from the specimens prepared bycoprecipitation in comparison with 93.8% from the mechanically-mixed one.

• 동력기계공학회지
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• 제19권4호
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• pp.30-35
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• 2015

The purpose of this study is to identify the low temperature performance and strength characteristics of V-based extruded homogeneous SCR. The extruded catalyst and the coated catalyst showed 50% and 27% of NOx conversion performance respectively at about $210^{\circ}C$ of catalyst temperature, so the extruded SCR was higher in de-NOx performance than the coated SCR especially at a low temperature zone. The compressive strength of the Enhanced Extrusion #1, in which the content of promoters such as silica, clay, glass fiber and binder was optimized, was a 120% improvement compared to the Extrusion#1 catalyst, higher than the coated SCR.

• 한국분말재료학회지
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• 제18권6호
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• pp.552-561
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• 2011

This study attempted to manufacture a Cu-15 at.%Ga coating layer via the cold spray process and investigated the effect of heat treatment environment on the properties of cold sprayed coating material. Three kinds of heat treatment environments, $5%H_2$+argon, pure argon, and vacuum were used in this study. Annealing treatments were conducted at $200{\sim}800^{\circ}C$/1 hr. With the cold sprayed coating layer, pure ${\alpha}$-Cu and small amounts of $Ga_2O_3$ were detected in the XRD, EDS, EPMA analyses. Porosity significantly decreased and hardness also decreased with increasing annealing temperature. The inhomogeneous dendritic microstructure of cold sprayed coating material changed to the homogeneous and dense one (microstructural evolution) with annealing heat treatment. Oxides near the interface of particles could be reduced by heat treatment especially in vacuum and argon environments. Vacuum environment during heat treatment was suggested to be most effective one to improve the densification and purification properties of cold sprayed Cu-15 at.%Ga coating material.

• KSBB Journal
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• 제25권2호
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• pp.137-141
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• 2010

신맛이 요구되는 식품에 일반적으로 첨가되는 구연산의 산미 기능과 첨가물로써 물성을 향상시키기 위하여 식물성 유지를 이용하여 코팅 수율이 95%이상이며 코팅물질함량은 총 조성물 중 20~33% 내외인 코팅구연산 제조공정을 개발하였다. 개발된 코팅구연산 (coated citric acid)은 식품에 투입되었을 때 최종제품에서 본 식품의 물성을 변화시키지 않고 구연산 본래의 신맛을 감소시키며, 제품이 입에서 녹을 시점에서 자극적이지 않은 신맛을 서서히 방출 시키는 특징을 기대할 수 있다. 본 연구를 통하여 개발된 코팅 구연산은 식품산업 및 향장품 등 다양한 관련 산업분야적용이 가능함으로써, 고부가가치 제품으로 수입대체 및 해외수출 등 관련 산업 분야로의 파급효과가 클 것으로 기대된다.

• 한국세라믹학회지
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• 제33권12호
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• pp.1353-1364
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• 1996

Recently semiconductor doped glasses have attracted attention as nonlinear optical materials because of their large third order nonlinear optical properties. The transparent and homogeneous CdS-doped SiO2 glass thin films were obtained by the dip=coating process of the sol-gel method. Thin films were consisted of glasses containing CdS microcrystallites which were formed by dissolved Cd2+ and S2- ions in a SiO2 matrix solutions. A subsequent thermal treatment of this samples led the formation of colloidal agglomerates and finally of microcrystallites. The size of CdS microcrystallites was about 4 to 15 nm after thermal treatments at various heating conditions. From the optical absorption spectra of the CdS-doped SiO2 glass films it was found that the absorption edge was blue-shifted compared with that of the bulk CdS crystal(~2, 4 eV) and that the amount of energy shift was inversely proportional to the crystal size. And the band gap energy increased with the decrease in crystallite size indicating that the quantum size effects occured.

• 한국주조공학회지
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• 제14권5호
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• pp.429-437
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• 1994

Influence of interfacial structure between matrix and particle in A356/coated SiC composite fabricated by squeeze casting method was studied. Experimental variables are types of coated metallic film on SiC particles such as Cu, Ni-P, and applied pressure for squeeze casting. It was found that coating treatment on SiC particles improves the wetting of liquid A356 alloy on SiC particles. SiC particle distribution is very homogeneous in A356 matrix alloy which is fabricated by squeeze casting. Analysing the surface morphology of fractured A356/coated SiC, it was concluded that metallic thin film by coating treatment on SiC particle improves the interfacial bonding between particle and matrix, and so does on mechanical properties such as tensile strength. However, there was on significant difference in hardness between those composite made of as-received SiC particle and coated SiC particle.

• 전자공학회논문지A
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• 제32A권11호
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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.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권7호
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• pp.514-520
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• 1999

Ferroelectric PZT(30/70)/PZT(70/30) heterolayered thin films were fabricated by spin-coating method on the $Pt/Ti/SiO_2Si$ substrate alternately using(30/70) and PZT(70/30) alkoxide solutions prepared by sol-coating method. The coating and heating procedure was repeated six times to form PZT heterolayered films, and thickness of the film obtained by one-times drying/sintering process was about 40-50 nm. All PZT heterolayered films, showed dense and homogeneous structure without the presence of rosette sturctrue. The relative dielectric constant, remanent polarization and leakage current density of PZT heterolayered films were superior to those of single composition PZT(30/70) and PZT(70/30) films, and those values for the PZT-6 film were 975, $21 \muC/cm^2\; and\; 8\times10^{-9}\; A/cm^2$, respectively. And the PZT-6 heterolayered film showed fairly good fatigue characteristics of remanent polarization and coercive field after application of $10^8$ switching cycles.

• Journal of Welding and Joining
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• 제15권1호
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• pp.116-124
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• 1997

A scope of this study is to establish the optimum plasma spray conditions for fine ($5\mu\textrm{m}$) $Al_2O_3$ powder. However, the flowability of the $Al_2O_3$ powder is not so good because of irregular particle shape and fine particle size. Therefore, powder feeding system was modified by 1) change of powder feeding line material from polymer to copper 2) shorten the powder feeding tube length 3) heating the powder feeding system to $80^{\circ}C$4) vibrating the powder feeding line continuously, in order to feed the fine powder homogeneously. The homogeneous powder feeding conditions were obtained with the modified powder feeding system by controlling the powder carrier gas flow and the powder flow rate indicator. The best plasma spraying conditions for the fine $Al_2O_3$ powder were found out as 40kw gun power, 80 g/min. powder feed rate and 50 mm working distance after characterizing the microstructure, hardness and wear loss of the $Al_2O_3$ coating layer.

• Journal of Welding and Joining
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• 제25권3호
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• pp.37-44
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• 2007

Mechanical and thermomechanical properties of the bulk metallic glass (BMG) are so unique that the deformation behavior is largely dependent on the temperature and the strain rate. Impacting behavior of NiTiZrSiSn bulk metallic glass powder during kinetic spraying was investigated in this study. Considering the impact behavior of the BMG, the kinetic spraying system was modified and attached the powder preheating system to make the transition from the inhomogeneous deformation to the homogeneous deformation of impacting BMG particle easy BMG splat formation is considered from the viewpoint of the adiabatic shear instability. It is suggested that the impact behavior of bulk metallic glass particle is determined by the competition between fracture and deformation. The bonding of the impacting NiTiZrSiSn bulk amorphous particle was primarily caused by the temperature-dependent deformation and fracture (local liquid formation) behavior.