급냉 응고된 Al합금의 열처리에 따른 미세구조 및 기계적성질에 관한 연구

서동수,조성석,신용덕,김혜성,임승무 忠南大學校 産業技術硏究所 1988 산업기술연구논문집 Vol.3 No.2

Rapidly solidified A2024 alumium alloy plate and powder produced by the twin-roll method and the centrifugal atomization method, respectively. The microstructure and shape of the specimen were closely related to the process parameters. The process parameters of the twin-roll method must be properly combined in order to manufacture defect-free plate. Four kinds of powder shape were produced by the centrifugal atomization process, e.g. spherical, tear drop, ligamental and flake. The age hardening behavior of the rapidly solidified A2024 alloy was somewhat different from the conventional slowly solidified one.

주형을 이용한 실리카 나노구조체 합성

김효중,곽중협,서태수,서동수 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.3

나노미터 직경을 갖는 침상형의 주형(hydroxyapatite)을 이용한 새로운 접근 방법으로 실리카 나노구조체를 졸-겔법을 근간으로 합성하였다. 본 합성법은 나노전구체(실리카 피복 주형) 제조, 나노전구체 소성 및 주형제거 과정으로 구성되어 있다. 나노전구체에 대한 주사 전자현미경(SEM), 투과 전자현미경(TEM), X-선 회절 분석(XRD) 및 광전자 분광 분석(XPS) 결과를 통해 주형 표면에 실리카가 피복되어 있음을 확인할 수 있었다. 또한, 고분해능 XPS 분석에 의해 관찰되는 넓고 비대칭적인 O 1s 스펙트럼의 curve-fitting을 검토한 결과 나노전구체 표면에 여러 종류의 산소가 존재함을 보였다. 또한, 에너지 분산 X-선 분석(EDS)을 통해 나노구조체는 실리콘과 산소로 조성되어 있음을 확인할 수 있었다. 실리카 나노구조체 직경은 대부분 50-200㎚ 정도로 주형의 직경과 동일한 양상을 보였다. 이상의 결과를 통해 본 연구에서 제안한 방법이 나노구조체의 새로운 합성방법으로써 적용 가능함을 확인할 수 있었다. A novel technique for the synthesis of silica nanostructures with needle-like template, hydroxyapatite, having nanometer diameter was investigated in this study. The synthetic method consisted of the following main steps: the preparation of nanoprecursor(silica-coated templates), the calcination of nanoprecursor and the removal of templates. The analysis results of scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photo-electron spectroscopy(XPS) for nanoprecursor revealed that silica particles were deposited onto the surface of templates. Further examinations(curve-fitting processing) of the asymmetrical broadening of O 1s peaks in the XPS spectra indicate the presence of multiple oxygen species on the surface. Energy dispersive X-ray spectroscopy(EDS) result confirmed that nanostructures were composed of silicon and oxygen. The diameters of the synthesized nanostructures, mainly in the range of 50-200㎚, correspond to the diameters of the templates. The results confirm that the proposed technique in this study can be utilized as a new method to fabricate the nanostructures.

플라스마 용사된 Gradient 단열 코팅의 열적 성질

서동수,이홍로 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.9

Two layer thermal barrier coatings failed by the thermal expansion mismatches beteen metallic substrate and ZrO₂ ceramic coat. Therefore, in this study, NiCr-ZrO₂(Y₂O₃) composite coat layers were introduced between substrate and ZrO₂ceramic coat in order to increase the durability by reducing the thermal expansion mismatches and by improving the bond strength. The NiCr alloy within composite coat oxidized prior to oxidation of NiCrAlY bond coat and the specimen failed within the composite coat layer. Oxidation products in composite coat layer were NiO and Cr₂O₃. The efficiency of the thermal barrier coatings increased with temperature up to 800℃ . The temperature of the substrate decreased by about 110℃ when the surface of ZrO₂ ceramic coat was heated to 800℃.

포도구균성 열상 피부 증후군 ( Staphylococcal Scalded Skin Syndrome ) 6 예

김윤동(Yoon Dong Kim),박민수(Min Soo Park),서기범(Ki Beom Suhr),이증훈(Jeung Hoon Lee),박장규(Jang Kyu Park) 대한피부과학회 2002 대한피부과학회지 Vol.40 No.2

The staphylococcal scalded skin syndrome encompasses a spectrum of blistering skin disease that ranges in severity from localized bullous impetigo to a generalized syndrome with cutaneous tenderness, widespread blistering, and superficial denudation or desquamation. This disorder is induced by the exfoliative toxin of Stapylococcus aureus. The intermediate form of staphylococcal scalded skin syndrome may be seen that begin as localized bullous impetigo but evolve to produce regionally limited bullae and denuded areas that may or may not harbor causative microorganism. We report six cases of the intermediate form of staphylococcal scalded skin syndrome in Daejeon for a short time. All cases occurred in children under 5 years of age and showed localized bullae and erythroderma with positive Nikolsky`s sign.

Fabrication and Inertia Dynamic Friction Properties of Pitch-based Carbon-Carbon Composites

Lee, Jinyong,Suhr, Dong-Soo,Lim, Yun-Soo,Lee, Seung-Goo,Park, Jong-Kyoo The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.3

This paper presents the effects of an initial braking velocity, a braking pressure, and the number of braking stop on the tribological behaviors for the three different C-C composites using an inertia dynamic-friction tester. The C-C composites were prepared through the processes of several cycles of pitch impregnation/carbonization with different friction surface texture such as continuous 8-harness satin fabric (ADD-1), chopped fiber (ADD-2) and chopped fiber (ADD-3) having higher fiber volume fraction on friction than ADD-2 by about 10%. ADD-1 exhibited a higher fraction coefficient (0.41~0.33) than those of ADD-2 and ADD-3 (0.32~0.26) under the various initial braking velocities and braking pressures. The fraction coefficients decreased with increasing the initial velocity and the braking pressures. Wear rate by the thickness change after every 25 stop indicated that ADD-2 and ADD-3 having 1.7~2.7 $\mu\textrm{m}$/stop/pair were much lower than that of ADD-1 showing 5.0~6.5 $\mu\textrm{m}$/stop/pair. All specimens showed a little bit lower wear rate during the middle stage than the initial and latter stages among 100 braking stops. ADD-1 showed higher friction coefficient and wear rate due to the active pull-out of the fibers, evidenced by thicker were film and wear debrises.

급속응고한 고망간강 박판의 미세조직 및 기계적 성질에 미치는 Cr 첨가원소 및 열처리 영향

김형수,서동수,조성석,홍종휘,전병완 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.5

Using a twin-roller type melt-quenching technique, we investigated the effects of Cr alloying element on the microstructure and mechanical properties of rapidly to solidified high manganese steel strip(0.5㎜ thick). We confirmed the possibility of manufacturing a high Mn alloy steel plate without hot-rolling by this method. In melt-quenched, the transformation from austenite to ferrite was suppressed resulting in only austenite phase. Its solidification mode is similar to the typical structure of the rapidly solidified metals. The dendrite structure region without directionality increased with increasing Cr alloying element. The 0.2% yield stress of the alloy with Cr was higher than the standard high manganese steel. The strengthening effect of Cr after heat treatment cannot be explained by its small solution hardening effect alone and is rather considered to be mainly attributable to gram refining due to the rapid solidification and the addition of carbide forming element, Cr.

A Structural Study of the Activated Carbon Fibers as a Function of Activation Degrees

Jae-Seung Roh,Dong-Soo Suhr 한국탄소학회 2004 Carbon Letters Vol.5 No.2

Isotropic pitch-based carbon fiber was isothermally activated in CO2 atmosphere. Structural parameters of the isotropic carbon fibers and activated carbon fibers (ACFs) were evaluated by X-ray diffraction (XRD). The d002 and La of the carbon fibers were measured to be 4.04 a and 23.6 a and those of ACFs were 4.29 a and 22.7 a, respectively, representing less ordered through activation process. The pores in the ACFs were characterized by BET, and they showed super-high specific surface area of maximum value 3,495 m2/g from average pore size of 8.3 a at 59% burn-off. It was recognized that 8-9 a was optimum range of pore size for efficient creation of high specific surface area. The average size of the pores formed at higher temperature (1100℃) was larger than that of the pores formed at lower temperature (900℃).

Analysis of X-ray Diffraction Patterns from Mechanically Alloyed Al - Ti Powders

KIM, Hye Sung,SUHR, Dong Soo,KIM, Gyeung Ho,KUM, Dong Wha 대한금속재료학회(대한금속학회) 1996 METALS AND MATERIALS International Vol.2 No.1

X-ray diffraction (XRD) method is one of the most versatile tools to characterize various forms of materials. Simplicity and wealth of information from the spectrum makes it attractive for the evaluation of mechanical alloyed powders. However, careful interpretation of the solubility of minor phase is necessary due to the effect of particle size on the detection limit in XRD method. In this study, we demonstrate the inaccuracy of solubility from XRD analysis of nanosized particle system using Al-Ti as a model. Using transmission electron microscopy (TEM), it is confirmed that large amount of nanosized Ti in Al matrix is not detected by XRD. The peak disappearance of minor phase can not be used to determine the solubility of nroechanically alloyed powders. Lattice parameter change of the major phase should be used to assess the solubility limit of the minor phase in nanosized particle system. In addition, the possible sources of error are addressed when mechanically alloyed powders of Al-Ti system are characterized by the XRD method. Proper XRD analysis methods are suggested to determine the lattice parameter, solubility of minor elements, crystallite size and strain variance in the MA Al-Ti samples. Pure Al is used as an internal standard to correct instrumental broadening, the Al {111} peak is used to determine lattice parameter of Al, and the lattice parameter of A1 is recommended to estimate the solubility of Ti in Al. The calculation of crystallite size and strain variance in the MA powders using Williamson-Hall equation is also discussed in detail.

Anisotropy in the Domain-Wall Motion of YFeO_3 Single Crystal

Kim, Chong-Oh,Suhr, Dong-Soo,Han, Kwan Hee 충남대학교 공업교육연구소 1985 論文集 Vol.8 No.2

단결정 YFeO₃에서 관찰되는 자구의 자벽이동속도의 결정방향 의존성을 사진법을 사용하여 측정하였다. 자벽이동속도의 이방성은 자벽에너지의 계산식으로부터 잘 설명되었다. 사방정시료의 대칭성으로부터 나오는 기하학적 요소가 자벽에너지 이방성을 만들며 이것이 자벽이동도의 이방성 원인이 되었다.

A Structural Study of the Activated Carbon Fibers as a Function of Activation Degrees

Roh, Jae-Seung,Suhr, Dong-Soo Korean Carbon Society 2004 Carbon Letters Vol.5 No.2

Isotropic pitch-based carbon fiber was isothermally activated in $CO_2$ atmosphere. Structural parameters of the isotropic carbon fibers and activated carbon fibers (ACFs) were evaluated by X-ray diffraction (XRD). The $d_{002}$ and La of the carbon fibers were measured to be 4.04 ${\AA}$ and 23.6 ${\AA}$ and those of ACFs were 4.29 ${\AA}$ and 22.7 ${\AA}$, respectively, representing less ordered through activation process. The pores in the ACFs were characterized by BET, and they showed super-high specific surface area of maximum value 3,495 $m^2/g$ from average pore size of 8.3 ${\AA}$ at 59% burn-off. It was recognized that 8-9 ${\AA}$ was optimum range of pore size for efficient creation of high specific surface area. The average size of the pores formed at higher temperature ($1100^{\circ}C$) was larger than that of the pores formed at lower temperature ($900^{\circ}C$).