• Journal of the Speleological Society of Korea
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• no.76
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• pp.61-66
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• 2006

The present report is the investigation of the effects of the HIP treatment on plasma-sprayed ceramic coating of $Al_2O_3$, $Al_2O_3-SiO_2$ on the metal substrate. These effects were characterized by phase identification, Vickers hardness measurement, and tensile test before and after HIPing.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.631-637
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• 1990

Lithium fluolide single crystals were grown by a floating zone method, with infrared radiation convergence type heater, which is free of contamination from the crucible wall. The crystals grown by this apparatus are 5cm in length and 5-6mm in diameter. The grown cryatal was examined by an optical microscope, XRD, Laue camera, Vickers hardness tester, and FTIR.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.275-275
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.166.2-166.2
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• 2016

최근 생산 장비의 발달로 인해 절삭공구, 전기전자 부품, 항공 및 자동차 부품 생산에 필요한 생산 장비의 수명연장, 고속 절단 및 고성능화가 중요시 되면서 우수한 내구성, 내마모성 및 고온 안정성을 갖는 기계부품 및 공구를 요구하게 되었다. 내마모성을 가지는 표면을 얻기 위해서는 TiN, TiC, AlN, Al2O3, CrN, ZrO2와 같은 경도 높은 물질을 증착하여 특성을 개선시키는 방법이 있다. 특히 AlN은 비교적 우수한 경도와 고온 안정성을 가지고 있어, 생산 장비의 고속 절단 및 반복되는 정밀 작업으로 인한 열충격과 마모를 완화시키는 역할을 하는 코팅재로 사용하기 적합하다. 본 실험에서는 RF-magnetron sputtering 방법을 이용하여 AlN 박막을 파워 150W, 질소가스 분압비에 따라 25%, 50%, 75%, 100%의 조건으로 금속기판 위에 증착하였다. 금속 기판 위에 제작된 AlN막은 XRD (X-ray Diffraction)을 사용하여 배향성을 확인하였고, HM-220 (Micro-vickers hardness tester)을 사용하여 AlN박막의 경도를 측정하였으며, SEM (Scanning Electron Microscope), AFM (Atomic Force Microscope)을 이용하여 표면의 구조와 거칠기를 측정하였다. 이 실험을 통하여 우수한 물성과, 치밀한 조직의 AlN박막이 고속 절삭 공구, 유공압 실린더, 베어링과 같은 금속부품의 코팅소재로 적용가능 할 것으로 기대된다.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.55-61
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• 1990

Effect of Al2O3 addition on the mechanical properties and microstructure of Ce-TZP were studied. 12, 14, 16Ce-TZP containing 0-40wt% Al2O3 were prepared by sintering at 155$0^{\circ}C$ for 2h. in air. Density, linear shrinkage, bending strength, Vickers hardness, microstructuer and the amount of stress induced phase transformation were examined. Vickers hardness increased linearly with increasing amounts of Al2O3. The amount of transformation and fracture toughness decreased linearly with increasing amount of Al2O3. Linear shrinkage and relative density decreased with increasing Al2O3 content in all composition of Ce-TZP. Grain growth of Ce-TZP was inhibited by Al2O3 dispersion and fracture mode of Ce-TZP/Al2O3 composites transformed from intergranular to transgranular fracture as the amount of Al2O3 increased. TEM observation revealed that Al2O3 particles were located mainly at grain boundaries of ZrO2.

• Journal of Technologic Dentistry
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• v.32 no.1
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• pp.9-16
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• 2010

This study sought to apply different MgO additions to Zirconia (20wt % Frit) and thereby determine its mechanical properties depending upon variation of temperature, as a part of elementary study. First, in terms of sintering density depending on sintering conditions, it was found that sintering density increased as temperature varied from $1100^{\circ}C$ to $1300^{\circ}C$. As the addition of MgO increased, it was found that sintering density tended to decrease at each temperature. For the maximum sintering density obtained from pellet, it was found that 3wt% MgO addition specimens sintered at $1300^{\circ}C$ had its maximum sintering density as high as 97.39%. This study measured mechanical properties of these specimens, and it was found that their bending strength tended to decrease as the content of MgO addition increased. And it was found that their bending strength reached up to 162 MPa when 3wt% MgO was added to them for sintering process at $1300^{\circ}\Delta C$. It was also found that those specimens had Vickers microhardness up to 4.6 GPa when 5wt% MgO was added to them for sintering process at $1300^{\circ}C$.

• Korean Journal of Materials Research
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• v.28 no.4
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• pp.221-226
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• 2018

The property changes of 18, 14, and 8K green gold alloys for jewelry are observed by adding 0.0, 3.0, and 5.0 wt% of indium (In), respectively. To check the composition of the alloys, an energy dispersive spectroscopy (EDS) analysis is conducted. Color and microstructure analysis is executed through bare-eye, macro camera, UV-VIS-NIR-colormeter, and optical microscope. The melting point, wetting angle, and hardness are measured using TGA-DTA, a wetting angle tester, and a Vickers hardness tester. The EDS analysis result demonstrates that each of the green gold alloys was manufactured with purposed contents. The color analysis result shows that the color of the alloys is similar to the color of the conventional 4 wt%-Cd 18K green gold, and the green color improves as the In content increases. The micro structure analysis result demonstrates that grain refinement improves as the amount of In increases. Enhancements in the melting point, wettability, and Vickers hardness changes appear as the In content increases and Au content decreases. The hardness is up to 260, which implies good durability. Therefore, the results suggest that the proposed 18, 14, and 8K In-added green gold alloys enhance the properties of jewelry products with regard to the green color, castability, and durability.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.515-518
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• 2006

This paper presents the friction and wear characteristics of contact type sealing unit for a water turbine of a small hydro-power generation, which Is to stop a leakage of a circulating water from a outside of an impeller to an inside of a rolling bearing. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Vickers hardness and the hardness of silicone carbide of SiC is 714.1 in Vickers hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces aye a dry friction a water film friction and a mixed friction that is contaminated by a dust, silt and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components

• Journal of Conservation Science
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• v.19
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• pp.31-42
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• 2006

There are many materials used in restoring missing parts of pottery and ceramics and they are used according to the each quality of materials. In our research we tried to find the new repair materials to solve many problems exposed in the existing repair materials. As a result, we made new repair materials that we properly put oven bake clays into repair epoxy putty which is being used as oven bake clays for a long time. Fortunately, through testing yellowing, vickers hardness, coloring and heating temperature, We could get an idea that new repair materials would be the best materials in the efficiency of restoration, yellowing, and coloring.

• Journal of Technologic Dentistry
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• v.31 no.3
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• pp.9-14
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• 2009

This study evaluated the mechanical properties of Ti-Cu alloys with the hope of developing an alloy for dental casting with better mechanical properties than unalloyed titanium. Ti-Cu alloys with four concentrations of Cu(2,5,10wt%) were made in an argon-arc melting furnace. The microstructure and micro-Vickers hardness were determined. X-ray diffraction pattern test was performed on the polished specimens. The microstructure of 2%Cu and 5%Cu alloys are shown acicular ${\alpha}Ti$ phase formed on the surfaces of previously formed $\beta$grains. The 10%Cu alloys has essentially a eutectoid structure; this structure includes lamella of ${\alpha}Ti$ and $Ti_2Cu$ phase that transformed from ${\alpha}Ti$ at the eutectoid temperature. The micro-Vickers hardness of CP Ti specimens was significantly(p<0.05) lower than that of any of the other alloys. Among the Ti-Cu alloys, the 10%Cu alloys exhibited a significantly(p<0.05) higher hardness value. but lower than that of Ti-6%Al-4%V alloy. From these results, it was concluded that new alloys for dental castings should be designed as Ti-Cu based alloys if other properties necessary for dental castings were obtained.