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최대호,김태호,이상양,이수완 선문대학교 ·중소기업기술지원연구소 2002 선문공대 연구/기술 논문집 Vol.7 No.1
먼저 소형 배합기를 사용하여 특정 방식을 가지고 혼합한 후 일정 성형 조건하에서 브레이크 마찰재 시편을 제작한다. 제조된 브레이크 마찰재 시편을 가지고, 정량적인 마모시험기를 통하여 마모계수를 측정하고 그 마모면을 SEM과 광학현미경을 이용하여 관찰하여 마모 기구를 조사하고, 마찰재의 열전도도 측정, 온도에 따른 TGA, DSC 측정, 분석 등 다양한 열적 특성을 분석하여 열 안정성을 평가하였다. By utilizing small mixer we can make brake frictional materials's specimen with special formulas in the condition of constant pressure and forming processes. The frictional coefficients were measured quantitatively with utilizing tribometer (TE77 reciprocating configuration), the worn surfaces were observed by a SEM (scanning electron microscopy), and the wear mechanism will be investigated. The thermal conductivity of the frictional materials was examined, and, TGA (thermal gravitation analysis), and DSC (differencial scanning calorimeter analysis) were used to study thermal properties and to evaluate the thermal stability of the frictional materials). On the bases of results from these experiments, the quantitative characteristics of frictional materials can be obtained.
생체 세라믹스용 마모시험장비의 제작 및 정방정지르코니아의 마모특성
김성호,류득배,문병규,이수완 선문대학교 중소기업기술지원연구소 2001 선문공대 연구/기술 논문집 Vol.6 No.1
생체 세라믹스용 마모시험장비를 제작하였다. 마모시험기는 lever system을 이용하여 하중인가가 되게 설계되었으며 step motor를 사용하여 회전수 조절이 용이하게 하였다. DAQ (Data Acquisition System)을 이용하여 하중을 측정하여 마찰계수를 측정할 수 있게 하였다. 성능평가를 위해 정방정지르코니아를 Ringer's solution에서 선속도 40 mm/s, 인가하중 10, 20, 30 N에서 마모시험 하였다. Grooving, crack networking등의 마모기구가 관찰되었다. A wear testing machine for bioceramics was designed and made, which loading and rotating parts consisted of a lower systemed and a step motor, respectively. Friction coefficient was determined by DAQ(Data Acquisition System). Wear resistance of tetragonal zirconia was measured under linear velocity of 40 mm/sec, applied load of 10, 20, 30 N in Ringer's solution, which showed grooving, crack networking on worn surfaces.
Behavior of residual stress in plasma sprayed ZrO₂ coatings with different contents of LaPO₄
Soo Wohn Lee,Jia Zhang,Huang Chen,Tohru Sekino,Seung Ho Kim 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
In this study, ZrO2-LaPO4 composite coatings were deposited by a plasma spraying technique. For nondestructive evaluation and easy practicability, the X-ray diffraction method was chosen to determine the residual stress in plasma sprayed ZrO2- LaPO4 composite coatings. The relationship between residual stress and content of LaPO4 was investigated. In this study, ZrO2-LaPO4 composite coatings were deposited by a plasma spraying technique. For nondestructive evaluation and easy practicability, the X-ray diffraction method was chosen to determine the residual stress in plasma sprayed ZrO2- LaPO4 composite coatings. The relationship between residual stress and content of LaPO4 was investigated.
Photocatalytic Activities of Plasma Sprayed TiO<sub>2</sub>-Based Coatings
Chen, Huang,Lee, Soo Wohn,Kim, Ho Seob,Lee, Eun Ah,Kim, Tae Ho,Shin, Jae Heyg,Aum, Ho Sung,Hur, Bo Young Trans Tech Publications, Ltd. 2005 Materials science forum Vol.486 No.-
<P>Plasma spraying technique was used to deposit thin TiO2-based photocatalytic coatings on a foamed aluminum. Before spraying, the composites of nano-TiO2 powder (P25) and nano- ZnO/CeO2/SnO2 powders were agglomerated into microsized powders by a spray-drying process. XRD, SEM, TEM, XPS and the photocatalytic activity evaluation by the decomposition of benzene were applied to characterize the starting powders and the coatings, respectively. The results showed that all the three plasma sprayed TiO2-based coatings were the mixture phases of anatase and rutile. The XPS spectra results revealed that the oxygen element was composed of three kinds of chemical states, i.e., crystal lattice oxygen, hydroxyl oxygen and physical-adsorbed oxygen. The plasma sprayed 90%TiO2-10%CeO2 coating and 90%TiO2-10%SnO2 coating exhibited similar photocatalytic activity, which was higher than that of 90%TiO2-10%ZnO coating.</P>
Low friction and high strength of 316L stainless steel tubing for biomedical applications
Amanov, Auezhan,Lee, Soo–,Wohn,Pyun, Young–,Sik Elsevier 2017 Materials Science and Engineering C Vol.71 No.-
<P>We propose herein a nondestructive surface modification technique called ultrasonic nanocrystalline surface modification (UNSM) to increase the strength and to improve the tribological performance of 316L stainless steel (SS) tubing. Nanocrystallization along nearly the complete tube thickness of 200 pm was achieved by UNSM technique that was confirmed by electron backscatter diffraction (EBSD). Nano-hardness of the untreated and UNSM-treated specimens was measured using a nanoindentation. Results revealed that a substantial increase in hardness was obtained for the UNSM-treated specimen that may be attributed to the nanocrystallization and refined grains. Stress-straip behavior of the untreated and UNSM-treated specimens was assessed by a 3-point bending test. It was found that the UNSM-treated specimen exhibited a much higher strength than that of the untreated specimen. In addition, the tribological behavior of the untreated and UNSM-treated specimens with an outer diameter (OD) of 1.6 mm and an inner diameter (ID) of 1.2 mm was investigated using a cylinder-on-cylinder (crossed tubes of equal radius) tribo-tester against itself under dry conditions at ambient temperature. The friction coefficient and wear resistance of the UNSM-treated specimen were remarkably improved compared to that of the untreated specimen. The significant increase in hardness after UNSM treatment is responsible for the improved friction coefficient and wear resistance of the tubing. Thus, the UNSM technique was found to be beneficial to improving the mechanical and tribological properties of 316L SS tubing for various potential biomedical applications, in particular for coronary artery stents. (C) 2016 Elsevier B.V. All rights reserved.</P>
Effect of amount of magnesia on wear behavior of silicon nitride
김성호,이수완,엄호성,정용선 韓國結晶成長學會 1999 한국결정성장학회지 Vol.9 No.2
세라믹 복합체의 미세구조는 이차상의 종류 및 양, 소결 조제, 그리고 소결 조건(즉, 소결 온도, 압력, 유지시간)에 영향을 받는다. 또한, 내마모 특성은 미세구조와 작업 조건이 내마모 특성에 크게 영향을 미친다. 본실험에서는 질화규소에 마그네시아의 양을 변화시켜 가압 소결(Hot Press) 방법으로 시편을 제조하였다. 마그네시아 양에 따른 미세구조, 기계적 특성 (경도, 강도, 파괴인성 ), 그리고 다양한 분위기(공기, 물, paraffin oil)에서의 내마모 특성을 조사하였다. 질화규소에 마그네시아의 양이 증가하였을 때, 입계의 유리상이 β-상의 장주형 입자를 커지게 하고, 또한 Hertzian contact damage를 저하시킨다. 대기 중에서 내마모 거동은 강도뿐만 아니라 파괴인성과 관련이 있고, 물과 paraffin oil에서는 경도와 밀접하다. 물속에서 마모시험 중 많은 유리상이 물과 반응하는 것을 생각할 수 있다. 그러므로 마찰 화학적 반응(tribochemical reaction)은 마모도 저하시킨다. Paraffin oil에서 높은 하중을 부하할 경우, Hertzian contact damage 때문에 초기 마모가 마모량에 지배적이다. The microstructure of ceramic composite has been found to be governed by the type and amount of the secondary phase, the sintering aid, and the sintering conditions such as sintering temperature, pressure and holding time. Moreover, tribological properties are strongly dependent on microstructure of composite and operating conditions. In this study, silicon nitride with various amount of magnesia as a sintering aid were prepared and sintered by a hot pressing (HP) technique. Microstructure, mechanical properties (hardness, strength, and fracture toughness), and tribological properties in different environments of Si_(3)N_(4) (in air, water, and paraffin oil) were investigated as a funtion of MgO content in Si_(3)N_(4). As increasing the amount of MgO in Si_(3)N_(4), the glassy phase in the grain boundaries enlarged the β-phase elongated grains, and also degraded the Hertzian contact damage resistance. Tribological behaviors in air was seemed to be determined by fracture toughness of Si_(3)N_(4), and those in water and paraffin oil was seemed to be determined by hardness as well as strength. Since glassy grain-boundary phase (MgO) in Si_(3)N_(4) expected to be reacted with water during sliding, such tribochemical reaction reduced wear. In paraffin oil under a higher applied load, the initial sliding dominated wear rate because of Hertzian contact damage.