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5Cr 계 열간공구강의 충격인성과 절삭성에 미치는 희토류금속 첨가의 영향
박현균,송치복,소진왕 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.8
A small amount of rare earth metals(REM) was added in melts of 5Cr hot working tool steel in order to investigate the changes in cleanliness, shape control of nonmetallic inclusions, and mechanical properties in comparison with those of typical hot working tool steel. The important results obtained are summarized as follows. 1) REM addition in 5Cr hot working tool steel resulted in significant decreases in final oxygen and sulfur, and total nonmetallic inclusions content. 2) RE-complex inclusions in the form of fine globular less than 3㎛ were composed of RE-oxysulfide surrounded by RE-sulfide. 3) Impact toughness, machinability, and chipability were improved by REM addition, owing to the refining of prior austenite grain size and insoluble carbide, and RE-complex inclusions.
박현균,조윤성,문길수,이준항 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.8
Noise problem arising from transmission gears of automobiles is well known to be related to the oxidation of gear materials during crburizing and distortion in the subsequent quenching and tempering process. In order to develop new grade steels with minimal internal oxidation layer which has detrimental effects on gear life and noise reduction, the effects of alloying element, Mn, Cr and Si on the internal oxidation behavier during carburization were studied in comparision to the characteristics of internal oxidation for two commmom transmission gear materials, SCM415H, SCR420H. The chemical composition of the new grade is 0,17C -Si$lt;0.13-0.75Mn -1.0Cr -0.40Mo. The hardenability characteristics of new grade steel is equivalent to that of SCM415H and SCr420H and internal oxidation layer depth after case hardening was smaller than those of SCM415H and SCr420H. The depth of internal oxidation layer was decreased with decreasing the amount of Si which has the highest affinity for oxygen.
박현균,김도경,박경진,전홍성,박종필,김종승,김성준 조선대학교 부설 유전생물공학연구소 1992 유전생물공학연구지 Vol.2 No.-
환경 미생물 분야와 산업미생물 분야 및 분자생물학 분야에서 주목을 받고 있고, 많은 연구가 된 새로운 E. coli의 bacteriophage를 토양으로 부터 분리해서, 그 물리적인 특성과 핵산을 밝혀내, phage상호간의 관련성을 검토하여 보았다. 그 결과를 요약하면 다음과 같다. 1. 토양으로 부터 분리한 phage는 숙주균에 따라 SJ-1, SJ-2, SJ-3, SJ-4, SJ-5, SJ-6, SJ-7이라 명명하였다. SJ phage들은 높은 숙주특이성을 나타내 phage SJ-2, SJ一7은 단일종 숙주균에만 감염이 되었고, SJ-1, SJ-3, SJ-4, SJ-5, SJ-6은 다중독성을 나타내었다. 2. 7종류의 SJ-phage는 본 실험조건하에서는 모두 virulent phage임이 밝혀졌다. 모든 용균반의 형태는 중앙이 투명한 둥근 모양이었으며 주변에 무리가 있는 것과 없는것 두가지 형태를 나타냈다. 용균반의 크기는 1-5mm이었으며, SJ-5phage의 용균반이 5mm로서 가장 컸고 SJ-7 phage가 가장 적었다. 숙주균은 OD_600 0.3-0.5상태에서 가장 감염되기가 좋았다. 그리고 상층배지의 한천 농도와 양은 0.5%와 3ml이 가장 좋은 조건이었다. 3. 일단 증식 실험의 결과를 보면 SJ-phage는 잠복기가 15-50분이었고 평균 phage방출수는 190-250이었다. SJ-6과 SJ-7이 잠복기가 15분으로 가장 짧았고 SJ-4가 50분으로 가장 길었다. 평균 방출수는 SJ-3과 SJ-5가 250정도로 많았으며 SJ-1과 SJ-2는 약 190정도였다. 4. SJ-phage는 PD buffer에서 안정하였고, magnesium ion 5×10^-3M의 첨가는 phage에게 큰 안정성을 주었다. SJ-phage는 pH6과 pH9사이에서 안정하였으며 그 pH는 숙주균의 최적 pH였다. SJ-phage의 온도 불활성화는 40 ℃이상에서 불활성화되기 시작하여 60 ℃이상에서는 완전히 불활성화 되었다. 자외선 조사에 의한 불활성화에서 SJ-phage는 120초 이후에 완전히 불활성화 되었다. All phages used in this experiment were isolated from soil of the surburbs of Chun-Nam, and they designated as phage SJ-1, SJ-2, SJ-3, SJ-4, SJ-5, SJ-6, SJ-7. The hosts were JM105, JM109, K802, LE392, MC1000, MV1184 and PSM CC, respectively. These phages were virulent under the experimental conditions. They produced plaques with dear and round without halo. The size of plaques was 1-5mm in diameter. SJ-phages were stable in 5×10^-3M Mg^2+. Thermostability experiments indicated that SJ-phages were stable at 37℃. Optimal pH of the phages were 6-9. Exposure of the phages to U.V. for 120 seconds resulted in complete inactivation. In one-step growth experiments, the latent period at 37 ℃ was about 15-50 min and the average burst see was 190-250. Agarose gel electrophoresis of the phage DNA showed single band of high molecular weight from SJ-1 to SJ-7 phages
Ti-6Al-4V합금에서 양극산화 공정변수가 TiO2 나노튜브 형성에 미치는 영향
유승연,박현균 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.8
To investigate the effect of anodic oxidation process parameters on TiO2 nanotube formation in Ti- 6Al-4V alloys, the composition of NH4F and H2O in the anodic oxidation processes were changed under the conditions of constant DC power ranging from 20 V to 60V and current density ranging from 10 mA to 30 mA. As the amount of NH4F was increased, the surface reaction rate became faster and surface dissolution also became more active. This result can be explained by the fact that TiO2 nanotubes were basically formed in the TiO2 layer located in the front of the Ti matrix by selective dissolution of the oxide layer, due to F - ions existing in the electrolytes. In anodic oxidation in ethylene glycol + 0.2 wt% NH4F with different amounts of water ranging from 0 ~ 8 vol%, the increase in the amount of water resulted in an increase in both the diameter and the length of growing nanotubes. When the voltage increased, the diameter and the length of the nanotubes tended to increase. But no nanotubes were formed at the voltage and the current density lower than a certain critical value. An increase in electrolytic holding time resulted in the diameter of the nanotubes increasing and decreasing repeatedly, but eventually increasing. X-ray analysis indicated that the as-grown nanotubes were amorphous while the anatase phase and the rutile phase were detected after anodic oxidation treatment, followed by annealing at 650 oC under Ar atmosphere for 2 hours.
Al2O3/Cu 접합에서 Metallizing paste의 조성이 접합강도에 미치는 영향
윤종혁,박현균 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.6
In joining Alumina to copper plate by Mo-Mn metallizing process, the effects of the composition of metallizing paste on the bonding strength were investigated. The bonding strength increased with increasing Mn amount in the paste up to 20% but followed by the decrease with addition of Mn. The maximum bonding strength reached 50MPa at 20%Mn when heated to 1550℃ for 60minute. The addition of Si to the metallizing powder increased the bonding strength of the joint by enhancing the mechanical bonding between the Alumina and the metallizing layer due to the decrease of layer viscosity with the addition of SiO2. It is thought that MnO reacted with Al2O3 to yield MnAl2O4 spinel, forming a joint.
Ag계 Filler Metal을 사용한 YSZ와 STS430의 브레이징 접합시 Ti, Sn의 함량 변화가 접합강도에 미치는 영향
이기영,박현균,Lee, Ki Young,Park, Hyun Gyoon 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.1
In Ti active brazing of YSZ to STS 430 using Ag-Cu Filler Metal, the effect of Ti contents on the shear bonding strength were investigated together with the effect of brazing temperature and holding time. The addition of Ti in Ag-Cu Filler Metal increased the bonding strength up to 4.68% Ti, followed by the decrease with further addition. This seems to be caused by formation of TixOy at the reaction layer. Brazing temperature was optimized at $960^{\circ}C$ among a given temperature ranges. The addion of Sn to Ag-Cu filler metal brought the decrease of its melting temperature its melting temperature without a significant decrease of bonging strength.