FeSiCr 박편/폴리머 복합시트의 전자파 흡수 특성에 미치는 자성분말 두께의 영향

김주범 ( Ju Beom Kim ),노태환 ( Tae Hwan Noh ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.12

The effects of magnetic powder thickness on electromagnetic wave absorption characteristics in Fe-6.5Si-0.9Cr (wt%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The atomized FeSiCr powders were milled by using attritor for 12, 24, and 36 h, powder thickness changed from 40 μm to 3 μm upon 36 h milling. The composite sheet, including thinned magnetic flakes, exhibited higher power loss in the GHz frequency range as compared with the sheets having thick flakes. Moreover, both the complex permeability and the loss factor increased with the decrease in thickness of the alloy flakes. Therefore, the enhanced power loss property of the sheets containing thin alloy flakes was attributed to the flakes of high complex permeability, especially their imaginary part. Additionally, the complex permittivity was also increased with the reduction of flake thickness, and this behavior was considered to be helpful for improvement of the electromagnetic wave absorption characteristics in the composite sheets, including thin alloy flakes.

Fabrication of an electrochemical biosensor with ZnO nanoflakes interface for methylglyoxal quantification in food samples

Jayaprakasan, Amudha,Thangavel, Amarnath,Bhat, Lakshmishri Ramachandra,Gumpu, Manju Bhargavi,Nesakumar, Noel,Babu, K. Jayanth,Vedantham, Srinivasan,Rayappan, John Bosco Balaguru 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.1

Increased consumption of fried foods such as grilled chicken contains elevated levels of methylglyoxal (MG), which is associated with diabetes mellitus. Hence, in this work, glyoxalase 1(GLO 1) based, zinc oxide (ZnO) flakes interfaced mediator free electrochemical biosensor was developed to detect MG in grilled chicken. ZnO flakes were synthesized by direct precipitation method. X-ray diffractometer and field emission scanning electron microscope were used to study the structural and morphological characteristics of ZnO flakes. The immobilization of GLO 1 on Pt/ZnO flakes modified electrode was confirmed by Fourier transform infrared spectroscopy. Cyclic voltammetric and amperometric studies were carried out using Pt/ZnO flakes/GLO 1 working electrode. The developed biosensor exhibited linear range of $0.6-2.0{\mu}M$, sensitivity of $0.281{\mu}A\;{\mu}M^{-1}$, LOD of 9 nM with a response time of <4 s and shelf life of 18 days (89%).

Fabrication of an electrochemical biosensor with ZnO nanoflakes interface for methylglyoxal quantification in food samples

Amudha Jayaprakasan,Amarnath Thangavel,Lakshmishri Ramachandra Bhat,Manju Bhargavi Gumpu,Noel Nesakumar,K. Jayanth Babu,Srinivasan Vedantham,John Bosco Balaguru Rayappan 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.1

Increased consumption of fried foods such as grilled chicken contains elevated levels of methylglyoxal (MG), which is associated with diabetes mellitus. Hence, in this work, glyoxalase 1(GLO 1) based, zinc oxide (ZnO) flakes interfaced mediator free electrochemical biosensor was developed to detect MG in grilled chicken. ZnO flakes were synthesized by direct precipitation method. X-ray diffractometer and field emission scanning electron microscope were used to study the structural and morphological characteristics of ZnO flakes. The immobilization of GLO 1 on Pt/ZnO flakes modified electrode was confirmed by Fourier transform infrared spectroscopy. Cyclic voltammetric and amperometric studies were carried out using Pt/ZnO flakes/GLO 1 working electrode. The developed biosensor exhibited linear range of 0.6–2.0 lM, sensitivity of 0.281 lA lM-1, LOD of 9 nM with a response time of\4 s and shelf life of 18 days (89%).

FeSiCr 박편/폴리머 복합 시트의 전자파 흡수 특성에 미치는 합금 어닐링 효과

김주범(Ju-Beom Kim),노태환(Tae-Hwan Noh) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.3

The soft magnetic Fe-Si-Cr flakes with the thickness of about 1 μm were annealed at 500 and 700 ℃ for 1 h, and the composite sheets for electromagnetic wave noise absorber available for quasi-microwave band were fabricated by using these annealed flakes and polymer. Further the power loss characteristics of the composite sheets was investigated to clarify the annealing effect on electromagnetic wave absorption properties. The power loss decreased in the frequency range of several GHz when the annealed flakes were used as compared to the sheet using the as-milled FeSiCr alloy flakes. Moreover the sheets using annealed flakes exhibited lower value of real and imaginary part of complex permeability. These inferior electromagnetic wave absorption properties of the composite sheets using annealed alloy flakes were considered to be obtained by the enhanced eddy current effect upon annealing induced recovery of microstructure and resulted low complex permeability.

Effect of hydrophilic graphite flake on thermal conductivity and fracture toughness of basalt fibers/epoxy composites

Kim, Seong Hwang,Heo, Young-Jung,Park, Mira,Min, Byung-Gak,Rhee, Kyong Yop,Park, Soo-Jin Elsevier 2018 Composites. Part B, Engineering Vol.153 No.-

<P><B>Abstract</B></P> <P>In this work, we fabricated basalt fiber-reinforced epoxy composites using natural graphite flakes. The composites were reinforced with various concentrations of natural graphite flakes. Natural graphite flakes significantly enhanced the mechanical properties of the composites, such as the critical stress intensity factor (K<SUB>IC</SUB>) and critical strain energy release rate (G<SUB>IC</SUB>). In particular, basalt fiber-reinforced composites containing 20 wt% of natural graphite flakes exhibited highest mechanical behavior compared. The fracture toughness mechanisms were illustrated using a crack theory based on morphology analyses of fracture surfaces. In addition, the composites exhibited high thermal stability and thermal conductivity, attributed to the exceptional thermal stability and thermal conductivity inherent in the natural graphite flakes. We observed a direct linear relationship between thermal conductivity and fracture toughness through certain polar components of surface energy. The natural graphite flake particles improved mechanical and thermal properties by performing a crack pinning role in the epoxy-matrix composites.</P>

FeCuNbSiB 합금 박편/폴리머 복합 시트의 전자파 흡수 특성에 미치는 자성분말 어닐링 온도의 영향

노태환(Tae-Hwan Noh),이태규(Tae-Gyu Lee) 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.5

The effects of annealing temperature on electromagnetic wave absorption characteristics in Fe<SUB>73.5</SUB>Cu₁Nb₃Si<SUB>15.5</SUB>B? (at%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The composite sheet including the magnetic flakes annealed at 425~475 ℃ for 1 h exhibited highest power loss in the ㎓ frequency range as compared with the sheets composed of the alloy flakes annealed at higher temperature than 475 ℃ or in as-milled state. Moreover the imaginary part of complex permeability had largest value in the ㎓ frequency range for the sheets including the flakes annealed at 425~475 ℃. The large value of power loss of the sheets including the magnetic flakes annealed at 425~475 ℃ was attributed to the high imaginary part of the complex permeability. However, because of its large transmission parameter S₂₁, the composite sheet having the magnetic flakes annealed at 525 ℃ showed low power loss.

Ink-jet printed stretchable strain sensor based on graphene/ZnO composite on micro-random ridged PDMS substrate

Hassan, Gul,Bae, Jinho,Hassan, Arshad,Ali, Shawkat,Lee, Chong Hyun,Choi, Yohan Elsevier 2018 Composites. Part A, Applied science and manufactur Vol.107 No.-

<P><B>Abstract</B></P> <P>Strain sensors based on graphene are attracting a lot of attention for electronic applications due to its outstanding electrical and mechanical properties. In this paper, we propose a high stretchable strain sensor based on graphene flakes/ZnO composite, which is deposited on micro-random ridged type PDMS substrate. To connect between graphene flake to flake, ZnO nano particles are applied and best graphene flakes and ZnO nano particles blending ratio is 1:0.5. Using this ink, an active layer is fabricated on the micro-random ridged PDMS substrate at ambient conditions through commercialized inkjet printer DMP-3000. Especially, utilizing the micro-random ridged 1.06 mm thick PDMS substrate with surface roughness of 0.34, its stretchability is achieved up to 30%. The flexibility of the fabricated strain sensor is demonstrated down to 10 mm bending diameter. These results reveal that the proposed strain sensor has potential in diverse wearable electronic applications and diverse human motions.</P>

Fabrication of Novel Ag Flake Composite Films Using a CMC/PEI Cross-Linking Process

Choong-Jae Lee,Byeong-Uk Hwang,Haksan Jeong,Kyung Deuk Min,Seung-Boo Jung 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.4

The multifunctional properties of cross-liked carboxymethlycellulose (CMC) and polyethyleneimine (PEI) films with varied CMC:PEI ratios and Ag flake sizes were studied. Both the CMC and PEI were cross-linked through a sonication process to achieve dispersive equilibrium. Fourier-transform infrared spectroscopy (FT-IR) was used to identify the functional groups in the sample material, with thermogravimetric analysis and differential scanning calorimetry used to investigate the overall thermal behavior of the CMC–PEI cross-linked films. Thermal diffusivity and thermal conductivity were also analyzed using laser flash analysis. To analyze the effects of Ag flakes as a filler material, the distribution of the Ag flakes within the film was determined using scanning electron microscopy. The thermal conductivity and resistance of the CMC films increased when cross-linked with 20% PEI. The electrical and thermal properties of the films also improved with the addition of Ag flakes.

가정간편식(HMR) 활용을 위한 수프용 양파 플레이크 제조 및 품질 특성

김두리(Duri Kim),천지연(Ji-Yeon Chun) 한국식품영양과학회 2021 한국식품영양과학회지 Vol.50 No.2

본 연구에서는 가정간편식용 수프에 첨가되는 양파 플레이크를 제조하기 위한 데치기 공정을 확립하고 이를 통해 제주산 농산물을 이용한 가정간편식용 수프 개발 시 첨가되는 양파 플레이크를 생산하기 위한 기초자료를 제공하고자 다양한 온도와 시간에 따른 양파의 색도, 수분활성도, 갈변도, pH, 가용성 고형분(Brix), 재복원율, 총 페놀 함량을 측정하였다. 데치기 조건에 따른 양파 플레이크의 수분활성도는 처리구별 큰 차이를 보이지 않았으며, 색도는 50°C 데치기 처리구가 70°C 데치기 처리구에 비해 L값이 증가하였고 a값이 감소하였다. 또한 저온에서 단시간 데치기가 양파 플레이크의 갈변을 억제하는 것으로 관찰되었다. pH와 가용성 고형분 함량은 데치기 온도와 시간이 증가할수록 감소하는 경향을 보였으며 재복원율은 70°C의 높은 온도를 이용하여 데치는 경우 높은 재복원율을 보였다. 총 페놀 함량은 데치기 온도와 시간이 증가할수록 감소하는 경향을 보였다. 결론적으로 본 연구에서는 pH가 낮아 미생물의 증식을 억제할 수 있는 70°C를 데치기 온도의 최적으로 선정하였고, 이 온도에서 데치기 시간에 따른 물리적, 영양학적 검사를 비교한 결과 데치기 시간이 증가할수록 재복원율이 높아졌지만 가용성 고형분 함량은 낮아지는 경향을 나타냈다. 또한 열처리 효율성과 상업적으로 이용성을 고려하여 1분 동안 처리하는 것을 최적으로 선정하였다. 이는 제주형 HMR 제품을 개발하는 데 기초자료로 활용될 수 있을 것으로 판단되며 양파플레이크를 수프에 적용하는 추가적인 연구가 필요할 것으로 사료된다. This study was undertaken to optimize the blanching process for producing onion flakes generally added in solid type HMR soup. Briefly, peeled and chopped onions were water-blanched at various temperatures and times (50, 60, 70°C/ 1, 2, 3 min), followed by hot air-blast drying (60°C, 9 h). Results revealed that the 50°C blanched treatment had a higher L-value and lower a-value than the 70°C blanched treatment. Moreover, the pH value, Brix, and total phenolic contents of onion flakes showed a dose-dependent decrease with increasing blanching temperature and time. Blanching at low temperature for a shorter time was effective in preventing the browning of onion flakes. In blanching at 70°C, the rehydration ratio was increased according to the increase of blanching time. Taken together, the results of this study reveal that water blanching at 70°C for 1 min is the optimal pre-treatment condition for commercial processing of onion flakes, wherein the nutritional properties are optimally retained.

알루미늄 기판에 코팅된 흑연입자의 배향도 변화와 열방사율 변화의 관계

강동수,이상민,김석환,이상우,노재승,Kang, Dong Su,Lee, Sang Min,Kim, Suk Hwan,Lee, Sang Woo,Roh, Jae Seung 한국재료학회 2014 한국재료학회지 Vol.24 No.3

This study is research on the thermal emissivity depending on the alignment degrees of graphite flakes. Samples were manufactured by a slurry of natural graphite flakes with organic binder and subsequent dip-coating on an aluminum substrate. The alignment degrees were controlled by applying magnetic field strength (0, 1, and 3 kG) to the coated samples. The alignment degree of the sample was measured by XRD. The thermal emissivity was measured by an infrared thermal image camera at $100^{\circ}C$. The alignment degrees were 0.04, 0.11, and 0.17 and the applied magnetic field strengths were 0, 1, and 3 kG, respectively. The thermal emissivities were 0.829, 0.837, and 0.844 and the applying magnetic field strengths were 0, 1, and 3 kG, respectively. In this study the correlation coefficient, $R^2$, between thermal emissivity and alignment degree was 0.997. Therefore, it was concluded that the thermal emissivities are correlated with the alignment degree of the graphite flakes.