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장평우 청주대학교 산업과학연구소 2007 産業科學硏究 Vol.24 No.2
Coercively of FePt binary alloy films manufactured in an rf magnetron equipment was reported to decrease with film thickness. To improve the low coercively of FePt thick films FePt-Al-O films were sputtered from fePt-Al_(2)O_(3) compiles target for which several Al_(2)O_(3) chips were placed on the Feet alloy target. As a result a coercively larger than 7 kOe could be obtained in FePt-Al-O films with Al contents less than 0.5 at. %.
장평우 청주대학교 산업과학연구소 2003 産業科學硏究 Vol.21 No.1
Magnetic and structural properties of YIG sputter films grown by sputtering were examined by FMR, XRD and VSM. The formation of perovskite phase could be greatly suppressed with small amount of oxygen addition during sputtering. When the films were deposited on GGG substrates at 700 - 750℃, saturation magnetization was as low as 30 emu/cc was due to the formation of amorphous Fe-Y-O phase. However, subsequent annealing in the air after sputtering could enhance the formation of YIG phase. Moreover, epitaxy YIG films were easily grown when amorphous Fe-Y-O films were sputtered at room temperature and then subsequently annealed in the air at 800 ℃. The films showed excellent soft magnetic properties.
기판온도와 Cr함량이 Co-Cr박막의 자기특성과 미세구조에 미치는 영향
장평우 청주대학교 산업과학연구소 1993 産業科學硏究 Vol.11 No.-
In order to clarify the correlation between magnetic properties and microstructural parameters of sputtered Co-Cr thin films, substrate temperature and Cr content in the films are varied. The degree of hcp (002) axis alignment perpendicular to substrate plane is improved and grain size becomes larger with increasing Cr content and decreasing the substrate temperature. The fact that grain size of the films becomes larger with increasing Cr content and decreasing the substrate temperature must be the results of development of preferred orientation during film growth, which originates from the surface energy anisotropy. By utilizing the results above-mentioned, Co-Cr mainlayer was self-epitaxially sputtered on the thin sublayer deposited on the water cooled substrate The perpendicular anisotropy field and c-axis alignment of the film can be improved. This is due to the good c-axis aligning behavior of Co-Cr films deposited at lower substrate temperture.
장평우 청주대학교 산업과학연구소 2005 産業科學硏究 Vol.22 No.3
3 dimensional FEM was used to improve dc bias current permeability of MPP core. In the simulation magnet size and magneto-motive force was varied. With increasing magnet size, bias field and permeability increased and decreased, respectively. However, increasing rate of bias field and decreasing rate of permeability decreased with magnet size. From the simulation it could be shown that a thin NdFeB magnet thinner than 1.2 mm can be effectively used for bias core. Bias core with 1.0 mm NdFeB magnet was manufactured and its properties were analyzed. As a results utility of bias MPP core suggestion could be demonstrated. However, core loss should be reduced for commercialization.
스파터조건이 태양전지용 ZnO:Al 투명전극의 특성에 미치는 영향
장평우,주수용 청주대학교 산업과학연구소 2011 産業科學硏究 Vol.28 No.2
Properties of Al doped ZnO (AZO) transparent conductive oxide (TCO) films were investigated for photovoltaic applications, for which AZO films were sputtered at different condition using two and four inch Al2O3:ZnO ceramic targets at mixture atmosphere of Ar and H2.. The resistivity was decreased with decreasing sputtering pressure and the resistivity of the AZO films sputtered using two inch target was much higher than that of four inch target. An addition of hydrogen during sputtering was very effective to improve the resistivity in addition to the decrease of the resistivity of the AZO films.
장평우 청주대학교 2017 産業科學硏究 Vol.34 No.2
In order to prevent tap water pipeline from corrosion several technologies have been applied such as cathodic anodic protection, coating, passivation and etc. Even though the effects of magnetic treatment has been controversial for past decades, there are some results which have claimed the effectiveness and possible mechanisms for the observed protection in water. In this study the magnetic field strength along the axial direction of the pipeline was simulated with 3-dimensional DC electromagnetic FEM in order to provide fundamental data for magnetic water treatment. For this the DC magnetic properties of pipeline with the same chemical composition as the buried pipeline was measured. It was concluded that the effective length of the pipeline under the magnetic water treatment with a field strength of 10 G was 25 m.
장평우,최재정 청주대학교 산업과학연구소 2014 産業科學硏究 Vol.31 No.2
0.05, 0.3 and 1 alumina powder was mixed to investigate the effects of alumina powder size on the magnetic properties of Fe-3.5%Si powder compressed cores. Core loss of the Fe-Si cores with 0.05 alumina decreased with increasing alumina content while the core loss of the cores with 0.3 and 1 powder increased. Meanwhile density of the core increased with increasing alumina size, the reason for which was assumed to be the fact that it was hard for the powder to be dispersed and attached to the surface of the Fe-Si powder with increasing alumina size so that the alumina powder was trapped in the small volume among the Fe-Si particles. Unusual permeability behavior of the cores with 1 alumina powder was also due to oxide layer formed during stress-relief annealing of the Fe-Si powders. If the oxide layer formed during stress-relief annealing was used together with 0.05 alumina powder as a insulating layer an excellent powder compressed core can be manufactured.
자성유변유체용 분말 및 침강속도 측정기 제작에 관한 연구
장평우 청주대학교 산업과학연구소 2023 産業科學硏究 Vol.41 No.1
In order to confirm whether the gas-atomized Fe-Si powder is applicable for magnetorheological fluids (MR fluid), the Fe-Si powder was heat-treated and a device capable of measuring the sedimentation rate of the MR fluid was studied. When Fe-Si powder is heat-treated, coercive force decreases, but magnetic permeability and maximum magnetic moment also decrease, so there is no advantage compared to carbonyl iron powder. The TIA output, which is a key part, continuously increased due to the increase of the LED temperature. As a result of compensating the output voltage by measuring the LED temperature with an NTC thermometer, stable results were obtained over time, and the sedimentation rate meter was successfully manufactured.