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홍순형(Soon Hyung Hong),김희연(Hee Yeoun Kim),이학주(Hak Ju Lee),박준협(Joon Hyub Park),문성욱(Sung Uk Moon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Mechanical properties of micro/nano-sized materials highly depend on their microstructure such as grain morphology and crystal orientation. In this study, the relationship between the microstructure and the mechanical properties of electrodeposited and sputtered thin films used for MEMS device were investigated. Theoretical elastic modulus from texture information showed good matches with experimental values measured by nanoindenter. Furthermore, the nanowear properties of thin films were characterized by ramped and constant nanoscratch experiments, resulting that the wear depths of MEMS materials under harsh tribological condition were determined by combination of their hardness and the elastic recovery based on the microstructural origins.
초고압 소결된 다이아몬드/실리콘 카바이드 복합재료의 계면특성 및 기계적 특성
박희섭,류민호,홍순형,Park, Hee-Sub,Ryoo, Min-Ho,Hong, Soon-Hyung 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.6
Diamond/SiC composites are appropriate candidate materials for heat conduction as well as high temperature abrasive materials because they do not form liquid phase at high temperature. Diamond/SiC composite consists of diamond particles embedded in a SiC binding matrix. SiC is a hard material with strong covalent bonds having similar structure and thermal expansion with diamond. Interfacial reaction plays an important role in diamond/SiC composites. Diamond/SiC composites were fabricated by high temperature and high pressure (HPHT) sintering with different diamond content, single diamond particle size and bi-modal diamond particle size, and also the effects of composition of diamond and silicon on microstructure, mechanical properties and thermal properties of diamond/SiC composite were investigated. The critical factors influencing the dynamics of reaction between diamond and silicon, such as graphitization process and phase composition, were characterized. Key factor to enhance mechanical and thermal properties of diamond/SiC composites is to keep strong interfacial bonding at diamond/SiC composites and homogeneous dispersion of diamond particles in SiC matrix.
김종형 ( Jong Hyung Kim ),오지선 ( Ji Seon Oh ),김동민 ( Dong Min Kim ),허성재 ( Seong Jae Huh ),임경훈 ( Kyung Hun Lim ),도기원 ( Gi Won Do ),홍순형 ( Soon Hyung Hong ),최승원 ( Seung Won Choi ) 대한류마티스학회 2010 대한류마티스학회지 Vol.17 No.1
Periorbital edema is a rare manifestation of systemic lupus erythematosus (SLE). We describe here a patient with bilateral periorbital edema as a presenting symptom of SLE. A 23-year-old woman was admitted for a sudden onset of severe periorbital edema that developed 7 days previously. On the basis of the malar rash, arthritis of the right hand and left wrist, leukopenia, proteinuria and the positive anti-nuclear and anti-dsDNA antibodies, she was diagnosed with SLE. Kidney biopsy revealed lupus nephritis (WHO class IV). After treatment with high dose of steroids, intravenous cyclophosphamide and daily hydroxychloroquine, her symptoms resolved, including the periorbital edema. She was discharged with prescriptions for prednisolone and hydroxychloroquine and she remains well.
MEMS용 NiTi 형상기억합금박막의 열기계적 물성에 관한 연구
김희연(Hee Yeoun Kim),홍순형(Soon Hyung Hong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
NiTi shape memory alloy have many MEMS applications such as microgripper, micro valve and micropump which need higher displacement. Mechanical properties of NiTi thin film are strongly dependent on concentration change and evolved residual stress during deposition process. In this paper, thermomechanical properties of RF sputtered NiTi thin film have been investigated. 3 types of NiTi thin film, Ni-rich, equiatomic and Ti-rich, was fabricated on p-Si(100) substrate at room temperature and crystallized for 1hr at 500℃. M↔A transformation temperatures with Ti concentration increased. Ti-rich NiTi thin film had martensite structure at room temperature and this type could be applied for microactuator application. In the annealed condition, residual stress showed highest value at Ni-rich composition and concentration dependence of residual stress were contrary from the concentration dependence of transformation stress. This is due to the shift of M↔A to positive direction as Ti contents increased. According to the results of laser curvature measurements, the residual stress of about 400㎫ were relieved by the A->M transformation and this residual stress were well matched to the calculated values from the misfit strain between thin film and substrate during cooling. The microtensile behavior of NiTi thin film showed the plateau at about 200㎫ and this meant the thin film could show higher recovery force rather than bulk NiTi materials residual stress successfully relieved by shape memory effect. Strain-temperaure hysterisis by TMA showed that Ti-rich NiTi thin film could be applied as a microactuator for MEMS at room temperature.