• Progress in Superconductivity
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• 제13권3호
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• pp.169-177
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• 2012

Distribution of the local properties in GdBCO and YBCO coated conductors was investigated using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared GdBCO and YBCO coated conductors to study the spatial distribution of the current density in a single bridge. Inhomogeneity of the ${T_c}^{max}$ in the bridge was analyzed from experimental results of Scanning Laser Microscopy (SLM) near the superconducting transition. The local transport and screening current in the bridge were also investigated using Scanning Hall Probe Microscopy (SHPM). A series of line scans of SLM of the GdBCO and YBCO sample showed that lines with more inhomogeneous distributions of ${\delta}V$ had more inhomogeneous distributions of ${T_c}^{max}$. The defect of the superconducting layer of the GdBCO sample caused by damage to the substrate affected the current flow. And we could analyze the redistribution of the current density using SLM and SHPM.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.49-49
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• 2010

Nanopiezotronics is an emerging area of nanotechnology with a variety of applications that include piezoelectric field-effect transistors and diodes, self-powered nanogenerators and biosystems, and wireless nano/biosensors. By exploiting coupled piezoelectric and semiconducting characteristics, it is possible for nanowires, nanobelts, or nanorods to generate rectifying current and potential under external mechanical energies such as body movement (handling, winding, pushing, and bending) and muscle stretching, vibrations (acoustic and ultrasonic waves), and hydraulic forces (body fluid and blood flow). Fully transparent, flexible (TF) nanogenerators that are operated by external mechanical forces will be presented. By controlling the density of the seed layer for ZnO nanorod growth, transparent ZnO nanorod arrays were grown on ITO/PES films, and a TF conductive electrode was stacked on the ZnO nanorods. The resulting integrated TF nanodevice (having transparency exceeding 70 %) generated a noticeable current when it was pushed by application of an external load. The output current density was clearly dependent on the force applied. Furthermore, the output current density depended strongly on the morphology and the work function of the top electrode. ZnO nanorod-based nanogenerators with a PdAu, ITO, CNT, and graphene top electrodes gave output current densities of approximately $1-10\;uA/cm^2$ at a load of 0.9 kgf. Our results suggest that our TF nanogenerators are suitable for self-powered TF device applications such as flexible self-powered touch sensors, wearable artificial skins, fully rollable display mobile devices, and battery supplements for wearable cellular phones.

• Journal of the Korean Electrochemical Society
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• 제6권4호
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• pp.236-241
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• 2003

Magnetic CoW thin film alloys were electrodeposited from citrate baths to investigate the resulting microstructure and magnetic properties. Deposit tungsten (W) content in the films electrodeposited at $70^{\circ}C$ were independent of current density, while coercivity decreased from hard $(H_{c,//}\~150\;Oe\;and\;H_{c.{\bot}}\;\~240\;Oe)$ to soft magnetic properties $(H_{c,//}\~20\;Oe\;and\;H_{c.{\bot}}\;\~30\;Oe)$ with increasing current densities from $10\;to\;100mA{\cdot}cm^2$, with deposit W content $(\~40\%)$ relatively unaffected by the applied current density. X-ray diffraction analysis indicated that hcp $Co_3W$ phases [(200), (201) and (220) planes] in the CoW films electrodeposited at $70^{\circ}C\;and\;10mA{\cdot}cm^{-2}$ were dominant, whereas amorphous CoW phases with small amount of hcp $Co_3W$ [(002) planes] were dominant with deposition at $70^{\circ}C\;and\;100mA{\cdot}cm^{-2}$. At intermediate current densities $(25\;and\;50mA{\cdot}cm^{-2}),\;hop\;Co_3W$ phases [(200), (002), (201) and (220)] were observed. The average grain size was measured to be 30 nm from Sheller formula. It is suggested that the change of the deposit coercivities in the CoW thin films electrodeposited at $70^{\circ}C$ is attributed to the change of microstructures with varying the current density. Nanostructured $Co_3W/amorphous-CoW$ multilayers were fabricated by alternating current density between 10 and $100 mA{\cdot}cm^{-2}$, varying the individual layer thickness. The magnetic properties of $Co_3W/amorphous-CoW$ multilayers were strongly dependent on the thickness of the alternating hard and soft magnetic thin films. The nanostructured $Co_3W/amorphous-CoW$ multilayers exhibited a shift from low to high coercivities suggesting a strong coupling effect.

• Tribology and Lubricants
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• 제14권2호
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• pp.1-9
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• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphated cellulose particles (average particle size 17.77 ${\mu}{\textrm}{m}$) was investigated at room temperature with electric fields up to 2.5 KV/mm. In this paper, for development of anhydrous ER suspensions using at wide temperature range, we would like to know fundamental understandings on the ER activity. As a first step, the anhydrous ER suspensions dispersed the phosphated cellulose particles were measured, and not only the electrical characteristics such as dielectric constant, current density and electrical conductivity but also the rheological properties on strength of electric field and quantity of dispersed phase were studied. From the experimental results, the anhydrous ER suspensions dispersed phosphated cellulose particles showed a stable current density and very high performance of ER effect $(\tau/\tau_0=1030)$ on the 2.5 KV/mm and the dynamic yield stress $(\tau_y)$ was in exponential proportion to the strength of electric fields.

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.89-92
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• 2012

The effect of organic impurities on the electrical properties of a neat epoxy resin was studied. 0.05, 0.5 and 1.0 phr of iso-propyl alcohol (IPA) and methylene chloride (MC) mixture (50/50 wt%) were used as impurities. The current density, volume resistance and impedance characteristics of the epoxy/IPA/MC systems were measured with a high voltage source meter and broadband dielectric spectroscopy. Glass transition temperature (Tg) was measured by a differential scanning calorimetry (DSC) and it was found that Tg decreased slightly with increasing IPA/MC content. It was also found that Tg values of the epoxy systems with various IPA/MC contents were closely related to the current density, volume resistance and impedance characteristics.

• Journal of Surface Science and Engineering
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• 제50권3호
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• pp.155-163
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• 2017

In this study, the effects of the concentration of metal ions and the applied current density in the Sn-Ag plating solutions were examined in regards to the resulting composition and morphology of the solder bumps' surface. Furthermore the effect of any impurities present in the methanesulfonic acid used as a base acid in the Sn-Ag solder plating solution on the stability of plating solution as well as the characteristics of the Sn-Ag alloys films was also explored. As expected, the uniform bump was obtained by means of removing impurities in the plating solution. Consequently the resultant solder bump was obtained in an optimal current density of the range of $1A/dm^2$ to $15A/dm^2$, which has acceptable bump shape and surface roughness with 12inch wafer trial results.

• Journal of Surface Science and Engineering
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• 제37권2호
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• pp.128-136
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• 2004

Effects of alloying elements on the surface characteristics of Fe-38Al intermetallic compounds were investigated using potentiostat. The specimens were casted by the vacuum arc melting. The subsequent homogenization and the stabilization led to the homogeneous DO$_3$ structure of the specimen. After the corrosion tests, the surface of the tested specimen was observed by the optical microscopy and scanning electron microscopy(SEM). For Fe-38 at.% Al intermetallic compound, the addition of Cr and Mo proved to be beneficial in decreasing the grain boundary attack by decreasing the active current density. Addition of Band Nb resulted in a higher active current density and also a higher passive current density. These results indicated the role of Cr and Mo in improving the pitting corrosion resistance of Fe-38 at.%Al intermetallic compound. Band Nb addition to Fe-38 at.%Al accelerated the granular corrosion. Fe-38 at.%Al containing Cr and Mo showed remarkably improved pitting corrosion resistance in comparison with Band Nb addition to Fe-38 at. %Al.

• Proceedings of the Korean Fiber Society Conference
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• 한국섬유공학회 2003년도 The Korea-Japan Joint Symposium
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• pp.69-70
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• 2003

10 wt.% of PAN was dissolved in N,N-dimethylformamide (DMF) and 1 wt. % of the multi wall carbon nanotubes (MWCNTs) was evenly dispersed in PAN solution by using ultrasonic miner. The 1 wt.% addition of MWCNT increased the specific capacitance by two times more from 82 to 160 F/g. The specific capacitance of carbon nanofiber(CNF)/carbon nanotube(CNT) composite capacitors was about 90 F/g at the current density of 500 mA/g. This value is even larger than the capacitance from the CNF electrode at the current density of 5 mA. The relatively high capacitance at the high current density is a practical importance for applications to supercapacitor in motor vehicle.

• Proceedings of the KIEE Conference
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1529_1530
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• 2009

The process conditions for fabricating p-type silicon pillars were optimized by controlling current density, bath temperature. To get best process flexibility for pillar arrays formation, three factors affecting pillar formation were changed. First, the solution bath was designed to keep constant temperature during the experiment irrespective of external temperature. Second, the counter Pt electrode was changed from rod type to mesh to obtain uniform distribution of current density. Third, Cr-Cu alloy electrode instead of Cu was used to increase electrode current density.

• Environmental Engineering Research
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• 제18권3호
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• pp.157-161
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• 2013

Treatment of textile wastewater by the electrocoagulation (EC) process is being investigated by this experimental study. The objective of this experiment is to observe the efficiency of the EC process in removing chemical oxygen demand (COD) and turbidity. In this experiment an iron electrode is used in the EC process, and different working parameters such as pH, current density and operating time were studied in an attempt to achieve a higher removal capacity. The results show that the maximum COD removal occurred at neutral pH at operating time 30 min. COD and turbidity removal reaches at maximum, with optimum consumption of electrodes, between current density 85-95 $A/m^2$, and only trace amounts of metals were determined in the EC treated effluent.