• Journal of the Korean Society for Heat Treatment
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• v.8 no.1
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• pp.65-74
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• 1995

This research was performed to investigate the effect of ageing on grain refinement of 82wt%Cu-13.5wt%Al-4.5wt%Ni-0.1wt% misch metal alloy with ageing temperature and time. The results obtained in this study are as follows; The variation of transformation temperature with ageing temperature had very influence on ageing time at $300^{\circ}C$. But it had not influence on ageing time at $100^{\circ}C$. The variation of transformation temperature after second reversed transformation cycle was not occured in martensitic phase ageing, but $M_s$ point was appeared equally with third reversed transformation cycle in parent phase ageing. The variation of $M_s$ point was not nearly with ageing time at $100^{\circ}C$ ageing temperature. But it was decreasing with ageing time at $300^{\circ}C$ ageing temperature and $A_s$ point was increasing with ageing time. Structure of parent phase ageing was being M18R martensitic and N2H martensitic phase. It was found that ${\alpha}$ and ${\gamma}_2$ phase were created by ageing of long time at $300^{\circ}C$ ageing temperature.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.8
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• pp.451-454
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• 2000

We have grown vertically aligned carbon nanotubes in a large area of Co-Ni codeposited Si substrates by the thermal CVD usign $C_2H_2$ gas. Since the discovery of carbon nanotubes, growth of carbon nanotubes has been achieved by several methods such as laser vaporization, arc discharge, and pyrolysis. In particular, growth of vertically aligned nanotubes is important to flat panel display applications. Recently, vertically aligned carbon nanotubes have been grown on glass by PECVD. Aligned carbon nanotubes can be also grown on mesoporous silica and Fe patterned porous silicon using CVD. In this paper, we demonstrate that carbon nanotubes can be vertically aligned on catalyzed Si substrate when the domain density of catalytic particles reaches a certain value. We suggest that steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically and each nonotubes are grown in bundle.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.103-117
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• 1997

The purpose of this experiment was to determind whether the gold electrodeposit on Pd-Ag and Ni-Cr alloys influences on the shear bond strength between veneering resin and silicoated metal surface. All the metal specimens were sandblasted with $250{\mu}m$ aluminum oxide and followed by silicoating and resin veneering. According to the metal surfaces to be veneered, experimental groups were divided into five. Group Prec : Gold alloy without gold coating Group Semi : Pd-Ag alloy without gold coating Group Base : Ni-Cr alloy without gold coating Group Semi-G : Pd-Ag alloy with gold coating Group Base-G : Ni-Cr alloy with gold coating All specimens were thermocycled 1,000 times at temperature of $5^{\circ}C$ to $55^{\circ}C$. The effects of gold electrodeposit on the shear bond strength between resin and metal interface were measured and fractured surface of the resin veneered metal was examined under the scaning electron microscope. The following results were obtained 1. The shear bond strength between resin and metal was $64.51{\pm}11.11Kg/cm^2$ in Prec group, $62.77{\pm}11.23Kg/cm^2$ in Base group and $58.97{\pm}9.20Kg/cm^2$ in Semi Group. There was no significant difference among the groups. 2. The bond strength in groups Semi-G and Base-G decreased about 17%, compared to the nongold-electrodeposit groups(Semi, Base). 3. In groups of non electrodeposit(Prec, Semi, Base), fracture occurred at the interface between alloy and resin, while fracture interface was observed between gold coating and resin in group Semi-G, and between metal substrate and gold coating in group Base-G respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.123.2-123.2
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• 2017

Fe-Ni-Cu 합금 전주를 위하여 황화물 용액에의 상의 열역학적 안정도를 작성하고 전주 조건을 선정하였다. $Fe-Ni-Cu-S-H_2O$ 용액의 열역학적 상의 안정도를 전산모사하기 위한 프로그램은 C#으로 작성하였다. JANAF 자료를 근거한 적정 전주 조건은 $130mA/cm^2$, $50{\sim}55^{\circ}C$, pH 2.4 이었다. XRF을 이용한 Fe-Ni-Cu의 합금 도막의 평균 조성은 Fe-42Ni-1Cu [wt.%] 이었다, 전류밀도가 낮아질수록 Ni과 Cu량은 증가하였다. 구리 농도가 증가하면 표면조도는 60 nm로 변화하였다.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.6
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• pp.292-298
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• 2012

In this study, Cu-2.5at.%Ni-1at.%Si alloys were fabricated by horizontal continuous casting system to improve the electrical conductivity and mechanical properties of Cu-Ni-Si alloy. Withdrawing speed was changed with 50, 100, 150 and 200 mm/min for the optimum manufacturing condition. Microstructure was observed using OM, FE-SEM and TEM. Electrical conductivity was measured by 4-point probe method and mechanical properties were tested. A horizontal continuous cast thin slab had sound macro and micro structures with partly crystallized structures. Electrical resistivity decreased with increasing annealing temperature from 250 to $850^{\circ}C$, with increasing annealing temperature The maximum hardness and tensile strength were Hv 130, 610 MPa at $550^{\circ}C$, respectively. With changing withdrawing speed from 50 to 150 mm/min, hardness, tensile strength, yield strength and elongation were Hv 60-65, 210-230 MPa, 65-75 MPa and 40-50%, respectively.

• Korean Journal of Metals and Materials
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• v.48 no.8
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• pp.749-756
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• 2010

Low carbon steels were oxidized isothermally at 1050 and $1180^{\circ}C$ for 4 hr in air in order to determine the effect of alloying elements Si, S, Cu, Sn, and Ni on oxidation. For oxidation resistance of low carbon steels, the beneficial elements were Si, Cu, and Ni, whereas the harmful elements were S and Sn. The most active alloying element, Si, was scattered inside the oxide scale, at the scale-alloy interface, and as an internal oxide precipitate. The relatively noble elements such as Cu and Ni tended to weakly segregate at the scale-alloy interface. Sulfur and Sn were weakly, uniformly distributed inside the oxide scale. Excessively thick, non-adherent scales containing interconnected pores formed at $1180^{\circ}C$.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.11a
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• pp.57-57
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• 2000

Brazing characteristics of the LTCC(Low Temperature Co-fired Ceramics)/ Kovar(Fe-Ni-Co alloy) was investigated. Kovar is one of the typical material for the lid of MCM and packages. In case of alumina package, Brazing process is done by higher temperature profile than 800 $^{\circ}C$ and Ag-Cu alloy. But, LTCC has sintering temperature near 850 $^{\circ}C$. So, it is difficult to use the same process as alumina brazing. The adhesion strength of the brazed part is affected by brazing alloy and metallization properties between conductor pattern and LTCC material. We investigated brazing characteristics of the LTCC/Kovar using various brazing alloys(Ag-Cu, Au-Sn) and process conditions. And, we examined the influence of the glass contents in conductor on the brazing characteristics of the LTCC/Kovar.

• Progress in Superconductivity
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• v.6 no.1
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• pp.69-73
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• 2004

Ni alloy tape is electropolished to be used as a metal substrate for fabrication of IBAD (ion-Beam Assisted Deposition)-MgO texture template fur HTS coated conductor. Electropolishing is needed to obtain a very smooth surface of Ni alloy tape because the in-plane texture of templates is sensitive to the roughness of metal substrate. The critical current of YBCO coated conductor depends on the texture of YBCO that depends on the texture of the IBAD MgO layer. And so the smoothness of the metal substrate is directly related to the superconducting properties of the coated conductor. In this study, we have prepared a reel-to-reel electropolishing apparatus to polish the Ni alloy tapes for IBAD. Various electropolishing conditions were investigated to improve the surface roughness. Hastelloy tape is continuously electropolished with high polishing current density (0.5 ∼ 2 A/$\textrm{cm}^2$) and fast processing time (1 ∼ 3 min). Polished hastelloy tapes have surface roughness(RMS) of below 1 nm on a 5 ${\times}$ 5 $\mu\m^2$ from AFM and SEM.

• The Journal of Korean Academy of Prosthodontics
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• v.19 no.1
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• pp.55-60
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• 1981

Some physical properties of Ni-Cr based alloy for porcelain veneering were compared after repeated casting without the addition of any new alloy. The specimen were cast in a centrifugal caster with an oxygen-propane torch at optimum temperature. The obtained results were as follows: 1. The yield strength and hardness of the second generation were no significant differences compared with first generation but the yield strength and hardness of the third generation slightly decrased. 2. The ultimate tensile strength and elongation appeared to decrease slightly in second, third generations. 3. The tensile fractured facets of the first generation specimen were normal in all specimen, but in the second generation there were six tensile specimen out of ten, in the third there were four tensile specimen out of ten.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.109-113
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• 2015

초임계 이산화탄소 발전 시스템 구축을 위해서는 고온, 고압의 열악한 환경에 노출되는 터빈, 열 교환기, 압축기와 같은 핵심 부품들의 내식성 평가는 반드시 수행되어야 한다. 이를 위해 후보소재 3종 Ferritic-Martensitic Steel (T92), Austenitic Steel (SS316L), Ni-based Alloy (IN738LC)를 선정하여 고온의 유사 초임계 $CO_2$ 발전 환경에서의 내식성 평가를 진행하였다. $600^{\circ}C$, $700^{\circ}C$의 2개의 온도 구간에서 $CO_2$ 분위기를 조성하여 800 시간 동안 노출시킨 뒤, Weight Change, Surface Morphology, Cross Section, Composition을 분석하였다. Cr-rich Protective Layer를 형성하는 Ni-based Alloy와 Fe/Cr-rich oxide를 형성하는 Austenitic Steel은 우수한 부식 저항성을 보인 반면에 Ferritic-Martensitic Steel은 높은 Weight Change와 Fe-rich Non-Protective Oxide가 관찰되어 상대적으로 낮은 부식 저항성을 보였다.