• 대한치과기공학회지
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• 제34권4호
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• pp.345-352
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• 2012

Purpose: The age-hardening mechanism of an Au-Ag-Cu-Pt-Zn alloy for crown and bridge fabrication was investigated by means of hardness test, X-ray diffraction study and field emission scanning electron microscopic observation. Methods: Before hardness testing, the specimens were solution treated and then were rapidly quenched into ice brine, and were subsequently aged isothermally at $400-450^{\circ}C$ for various periods of time in a molten salt bath and then quenched into ice brain. Hardness measurements were made using a Vickers microhardness tester. The specimens were examined at 15 kV using a field emission scanning electron microscope. Results: By the isothermal aging of the solution-treated specimen at $450^{\circ}C$, the hardness increased rapidly in the early stage of aging process and reached a maximum hardness value. After that, the hardness decreased slowly with prolonged aging. However, the relatively high hardness value was obtained even with 20,000 min aging. By aging the solution-treated specimen, the f.c.c. Au-Ag-rich ${\alpha}_0$ phase was transformed into the Au-Ag-rich ${\alpha}_1$ phase and the AuCu I ordered phase. Conclusion: The hardness increase in the early stage of aging process was attributed to the formation of lattice strains by the precipitation of the Cu-rich phase and then subsequent ordering into the AuCu I-type phase. The decrease in hardness in the later stage of aging process was due to the release of coherency strains by the coarsening of tweed structure in the grain interior and by the growth and coarsening of the lamellar structure in the grain boundary. The increase of inter-lamellar space contributed slightly to the softening compared to the growth of lamellar structure toward the grain interior.

• 한국안전학회지
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• 제15권4호
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• pp.8-14
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• 2000

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with time of service exposure in the high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, accelerated aging technique are needed to estimate and analyse the material degradation. In the this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. And tensile test, $k_{IC}$ test, hardness test and Scanning Electron Microscope analysis were performed in order to evaluate the degradation of 1Cr-1Mo-0.25V steels.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.389-394
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• 1994

The age-hardening behavior and the structural changes in a commercial dental Au-Ag-Cu-Pd alloy were investigated by means of hardness test, optical and scanning electron microscopic observation, energy dispersive spectroscopy and X-ray diffraction study. The drastic reduction in hardness by prolonged aging occurred after a rapid increase in hardness at the initial stage by the isothermal aging at $350^{\circ}C$. This softening was due to the broad precipitates formation of the lamellar structure which was composed of the f.c.t. AuCu I ordered f.c.t. phase containing Pd and the f.c.c. Ag-rich $\alpha$1 solid solution f.c.c.phase containing Au.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.5-7
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• 1988

Effect of isothermal aging on the crystallization of $Fe_{78}B_{13}Si_{9}$ metallic glass has been investigated by electrical resistivity, X-ray measurements, bending test, thermal analysis and transmission electron microscopy. Amorphous $Fe_{78}B_{13}Si_{9}$ alloy was annealed isothermally for 5 to 1200 mon. between 300 C and 540 C. It has been found that close relation between relative resistivity and X-ray diffraction pattern showed. The crystalline peak of $\alpha$-(Fe, Si) and Fe$_2$B are detected by X-ray experiment. The crystalline phases observed by TEM show $\alpha$-(Fe, Si) and Fe$_3$B with dendritic and cylindrical morphology, respectively. It has been also found that the embrittleness of aged samples rapidly increased with the crystallization and was shown before the crystallization.th the crystallization and was shown before the crystallization.

• 폴리머
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• 제31권4호
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• pp.335-342
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• 2007

장시간에 걸친 에이징이 carboxyl acid group을 포함한 수 백 나노 두께의 6FDA계 폴리이미드 박막에 미치는 영향을 박막의 가스투과도와 굴절률의 변화를 통하여 측정하였다. 에이징 시간에 따른 가스투과도의 변화는 carboxyl acid group을 포함한 박막이 이를 포함하지 않은 박막보다 빠른 투과도 감소와 선택도의 증가를 보였으며, 박막 특성의 정량적 분석을 위해 Lorent-Lorentz 이론을 통하여 volume relaxation을 정량화하였다. 박막의 밀도와 부분자유부피는 에이징 시간의 증가에 따라 지속적인 증가 혹은 감소의 경향을 보였으며, 에이징 시간에 따른 가스투과도와 부분자유부피간의 상관관계를 $P=Ae^{(-B/f)}$을 통하여 예측할 수 있었으며, 그 결과는 다른 고분자 분리막이 보인 경향과 일치하였다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.75-87
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• 2001

Three different kinds of substrate used in this study : bare Cu substrate, Ni-P/Cu substrate with a Ni-P layer thickness of $5\mu\textrm{m},$ and Au/Ni-P/Cu substrate with the Ni-P and Au layers of $0.15\mu\textrm{m}$ and $5\mu\textrm{m}$ thickness respectively. The wettability of various Sn-base solders was affected by the substrate metal finish used, i.e., nickel, gold and copper. On the Au/Ni-F/Cu substrate, Sn-base solders wet better than any of the other substrate metal finishes tested. The interfacial reaction between various substrate and Sn-base solder was investigated at $70^{\circ}C,$ $100^{\circ}C,$ $120^{\circ}C,$ $150^{\circ}C,$ $170^{\circ}C$ and $200^{\circ}C$ for reaction times ranging from 0 day to 60 day. Intermetallic phases was formed along a Sn-base solder/ various substrate interface during solid-state aging. The apparent activation energy for growth of Sn-Ag/Cu, Sn-Ag-Bi/Cu, and Sn-Bi/Cu couples were 65.4, 88.6, and 127.9 Kj/mol, respectively. After isothermal aging, the fracture surface shoved various characteristics depending on aging temperature and time, and the types of BGA pad.

• 전자공학회논문지A
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• 제30A권1호
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• pp.23-30
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• 1993

Hydrogenation on the top gate and bottom gate Poly-Si TET's was performed by using Nh$_{3}$ plasma and annealing SiN film deposited by PECVD and then the electric characteristics on Poly-Si TET were investigated. As the time of NA$_{3}$ plasma treatment increaes, on/off current ratio gradually increases and the swing value decreases. The trap densities of graim boundaries in Poly-Si decrease very much during the inital 20min of hydrogenation time, and the decreasing scale becomes smaller after 20 min. The electric characteristics of the top gate TFT are better than those of the bottom gate TFT, it is considered due to the defects at the interface between the Poly-Si and the underlayer, SiO$_{2}$. After NH$_{3}$ plasma was treated for 2 hours for the top gate TFT, as the aging time atroon temperature increases on current was not scacely changed and off current decreases more than 1 order. Gate current density recovers to original value after the aging treatment for 8 days and then the electric characteristics are finally improved. It is suggested that the degraded characteristics of gate oxide are improved, from the variations of C-V characteristics with aging time. For the hydrogenation of isothermal and isochronal annealing SiN film deposited by PECVD, the characteristics of Poly-Si TFT are improved with increasing annealing temperature and are not largely changed with increasing annealing time. This results is good in agreement with the hydrogen reduction in Sin film as variations of annealing temperature and time.

• 한국기계가공학회지
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• 제17권6호
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• pp.46-52
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• 2018

Nondestructive evaluation for mechanical degradation of ultrasuper-critical (USC) heat-resistance steel, which is attractive to the next generation of power plants is studied by magnetic reversible permeability. The interrelationship between reversible permeability and high-temperature mechanical degradation has been investigated by precise measurement of permeability nondestructively. Also, the effects of microstructural variation on reversible permeability are discussed. Isothermal aging was observed to coarsen the tempered carbides ($Cr_{23}C_6$), generated the intermetallic phases ($Fe_2W$), and grow rapidly during aging. The dislocation density also decreases steeply within lath interior. The peak to peak interval (PPI) of reversible permeability profile decreased drastically during the initial 500 h aging period, and was thereafter observed to decrease only slightly. The variation in PPI is closely related to the decrease in the number of pinning sites and the degradation in tensile strength.

• 비파괴검사학회지
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• 제28권2호
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• pp.177-183
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• 2008

고온-고압의 장시간 사용으로 나타나게 되는 재료열화현상을 이해하고 구조건전성 모니터링을 위한 기초연구로 사용하고자 대표적인 로터용 내열강인 2.25CrMo 강과 9CrMo 강 그리고 12CrW 강을 연구하였다. 재료열화를 모니터링하기 위해 2.25CrMo 강은 등온열화 시험을 9CrMo 강은 크리프-피로 시험을 그리고 12CrW 강은 크리프 시험을 각 단계별로 수행하였다. 이들 각 손상재에 대한 초음파전파특성, 비저항측정 그리고 보자력측정을 통하여 미세조직 의존성을 고찰하였고 이들 파라미터는 특정 미세조직의 변화에 상당히 민감하게 작용하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.502-505
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• 2004

The purpose of this experiment is to modify diagnosis criterion of isothermal relaxation current(IRC) measurement equipment which is using for distribution cable diagnosis. We're using this system for several years in the field instead of DC leakage current measurement and lots of cables were replaced. But we have to investigate on the reliability of this equipment for our cables because we didn't carried out condition assessment of extracted cables after field diagnosis by this equipment. It is important thing for cable maintenance. If the replacement criterion is improper we can not prevent failures or will waste budget on account of replacement of the sound cables. In this papar we selected field installed cables and injected silicone fluid to the cables for insulation rehabilitation. In order to prove reliability of the diagnosis equipment we compared diagnosis results and AC breakdown strength according to operating time after silicone treatment. This is the results of the field test for 1 year.