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PCB용 Glass/Epoxy 프리프레그의 경화중 점성거동 연구
諸葛英淳,尹南畇 論文集 1999 論文集 Vol.16 No.2
This paper dealed the studies on the viscosity behaviors of glass/epoxy prepreg for PCB during the cure process. The dynamic scan of glass/epoxy prepreg using DSC showed that the exothermic reaction started at the temperature of 118℃. The peak temperature was 169.7℃ and the total reaction enthalpy (ΔH) was 13.54I/g. The results of ion viscosity behaviors of this prepreg system using dielectrometer exhibited the lowest ioniviscosity at about 115℃, and then the ionic viscosity was gradully increased upto 150℃. This indicated that the cure reaction of this prepreg started at 115℃ and the molecular weight was increased by the accelerated thermal cross-linking reaction.
Nam, Yeong Gyun,Koo, Bonuk,Chang, Mi Se,Yang, Sangsun,Yu, Jihun,Park, Yong Ho,Jeong, Jae Won Elsevier 2020 Materials letters Vol.261 No.-
<P><B>Abstract</B></P> <P>Recently, selective laser melting (SLM) of Fe-based soft magnetic bulk metallic glass (BMG) is garnering great attention because it can yield both superior magnetic properties such as high permeability and low core loss and near-net shaping of 3-dimensional complex components. However, full vitrification of BMGs with high saturation magnetization above 1.2 T has never been realized because cooling rates are limited and compositional inhomogeneity induced by rapid laser processing causes severe undesirable crystallization. In this work, a double scan strategy has been employed with the aim of amorphous phase fraction enhancement as well as densification. We have shown that double scanning effectively fills voids generated due to partial melting of powders, and leads to relative density of up to 96% and corresponding saturated magnetization of 1.22 T. More importantly, the double scan strategy stimulates reflow in the melt pool, securing compositional uniformity, and eventually enhances amorphous phase fraction to a value as high as 47%. As a consequence, coercivity has been significantly decreased, which in turn reduces core loss and increases permeability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Selective laser melting of amorphous soft magnetic alloy has been demonstrated. </LI> <LI> Double scanning densifies alloys leading saturated magnetization of up to 1.22 T. </LI> <LI> Double scanning induces reflow in the melt pool and secures compositional uniformity. </LI> <LI> Amorphous phase fraction has been enhanced to a level as high as 47%. </LI> <LI> Double-scanned alloys show improved magnetic properties. </LI> </UL> </P>
Yeong Gyun Nam,Hyun Ah Im,Su Bong An,Hearan Kim,Jung Woo Lee,Sangsun Yang,Jae Won Jeong 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
As the operating frequency of the power conversion element increases for the purpose of miniaturization and weight reduction, the development of a soft magnetic material with high saturation magnetization is required to cope with the increase in current while exhibiting low iron loss even at high frequencies above 100. kHz. In the case of crystalline powder materials such as Fe-Ni, Fe-Si-Al, and Fe-Si, which were used in the past, the iron loss due to the eddy current increases rapidly as the frequency increases above 100 kHz. Current limiting use at high frequencies. Amorphous soft magnetic powder material is emerging as an alternative because it has no crystalline magnetic anisotropy and high specific resistance compared to conventional crystalline powder material and shows low iron loss even at high frequencies. A gas spraying method using an inert gas is used to prepare the amorphous powder, because the water spraying method has effects such as reducing saturation magnetization and increasing iron loss due to oxidation. In the gas injection method, it is important to achieve high GFA (glass forming ability) because the cooling rate is limited and it is difficult to make amorphous powder. In this study, a composition containing 80% or more of Fe was designed to obtain high saturation magnetization and high GFA. Based on the high-Ms Fe82.5B15Si2C0.5 quaternary composition, 1-2% of transition metal Mo and B were added in the direction of increasing GFA. The properties of the amorphous alloy were evaluated by fabricating a ribbon-shaped specimen through arc melting and melt spinning. The magnetic properties of the ribbon were measured using a vibrating sample magnetometer, a DC loop tracer and a BH analyzer. As a result, Fe82.5BXSi2C0.5Mox alloy containing Mo showed high saturation magnetization of 1.5T or more and high GFA for stable formation of high-Ms amorphous soft magnetic powder.
남일현,박주태,안길영,김균환 대한골절학회 1996 대한골절학회지 Vol.9 No.1
Althougn not as common as the intra-articular fracture of distal radius, if present considerable challanges in management. Because the intra-articular fracture is frequently accompanied by comminution and intra-articular extension of fracture, it can produce some disability of the wrist joint. Now there are wide consensus that more aggressive surgical treatments are needed in such complex fracture to fulfill the better results. So recently, anatomical reduction, rigid internal fixation and early rehabilitation was recommended. The authors analized sixteen causes of intra-articular fracture of distal radius that were treated with open reduction and internal fixation at the Department of Orthopedic Surgery of Pohang St, Mary's Hospital from March, 1990 to December, 1993. The object of this study is to evaluated the correlation between the rigid internal fixation and early rehabilitation. The average follow up period was 18.3 months(from 14 to 27 month). The result were as follows; 1. Among 1st 2 weeks after operation, long arm cast was applied. During 2nd 2 weeks, monster cast was applied. At 4 weeks, we started R.O.M.exercise and additional night splint was applied during 4 weeks. 2. The radiological union was achieved at all cases and the average time of union was 9.5 months. 3. According the Cole and Obletz criteria, excellent were I 1 cases, goad 3 cases, fair 2 cases. 4. We obtained satisfactory result by rigid internal fixation and early rehabilitation.