• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.83-86
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• 2004

A high temperature tolerant microelectronic-based carbon monioxde(CO) gas sensor has been developed. The gas sensing performance has been studied over a wide temperature range$(100-300^\circ{C)}$. The gas sensitivity of the sensor is high, its initial sensing behavior is very fast, and the sensor is reproducible. Pt-SiC and $Pt-SnO_2-SiC$ diodes are fabricated using standard semiconductor processes and their CO gas-sensing behaviors are analyzed as a function of CO gas concentration and temperature by I-V and $\Delta{I-t}$ methods under steady-state and transient conditions. The sensitivity of the device with $Pt-SnO_2$ catalytic gate is higher than that of the Pt gate. The experimental results indicate that $SnO_2$ layer improves the catalytic reaction of the Pt layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.335-338
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• 1997

Platinum-Cobalt alloy thin films were deposited on A1$_2$O$_3$substrate by magnetron cosputtering for RTD temperature sensors with wide temperature ranges. We made Pt-Co alloy resistance patterns on the A1$_2$O$_3$substrate by lift-off method and fabricated Pt-Co alley RTD temperature sensors by using Pt-wire, Pt-paste. We investigated the physical and electrical characteristics of theme films under various conditions, input power, working vacuum, annealing temperature and time, and also after annealing these films. The resistivity and sheet resistivity of these films were decreased with increasing the annealing temperature. At input power of Pt : 4.4 W/cm$^2$, Co : 6.91 W/cm$^2$, working vacuum of 10 mTorr and annealing conditions of 800$^{\circ}C$ and 60 min, the resistivity and sheet resistivity of Pt-Co thin films was 15${\mu}$$\Omega$$.$cm and 0.5$\Omega$/ , respectively, and the TCR value of Pt-Co alloy thin films with thickness of 3000${\AA}$ was 3740ppm/$^{\circ}C$ in the temperature range of 25∼600$^{\circ}C$. These results indicate that Pt-Co alloy thin films hove potentiality for the RTD with wide temperature ranges.

• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.273-278
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• 2014

Using ab initio calculations, the effects of uniaxial, biaxial, and hydrostatic strains on the magnetocrystalline anisotropy of $L1_0$-orderd FePt and CoPt alloys were systematically investigated. Interestingly, the rates and the signs of magnetocrystalline anisotropy changes of FePt and CoPt were determined by the directions and dimensions of strains. The calculation results are consistent with the previous experimental observations and are expected to provide directions to tailor magnetic properties of various types of $L1_0$-ordered FePt and CoPt systems.

• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.20-23
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• 2002

The local coercivity distribution of CoCrPt alloy films prepared by dc magnetron sputtering has been investigated by means of a magneto-optical microscope magnetometer (MOMM) capable of simultaneously measuring the local properties on 400 nm spatial resolutions. Serial samples of CoCrPt alloy films were prepared with the Pt composition of a range from 6 to 28 at. %. We find that the local coercivity distribution crosses over from Gaussian to non-Gaussian distribution in CoCrPt alloy films with increasing Pt composition, with increasing trends in the width of the distribution as well as the average local coercivity. Transmission electron microscopy (TEM) studies reveal that our findings are closely correlated with the dependences of the grain size distribution and its average size on Pt concentration.

• Journal of Environmental Science International
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• v.20 no.2
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• pp.251-260
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• 2011

$TiO_2$- and $SiO_2$-supported $Co_3O_4$, Pt and $Co_3O_4$-Pt catalysts have been studied for CO and $C_3H_8$ oxidations at temperatures less than $250^{\circ}C$ which is a lower limit of light-off temperatures to oxidize them during emission test cycles of gasoline-fueled automotives with TWCs (three-way catalytic converters) consisting mainly of Pt, Pd and Rh. All the catalysts after appropriate activation such as calcination at $350^{\circ}C$ and reduction at $400^{\circ}C$ exhibited significant dependence on both their preparation techniques and supports upon CO oxidation at chosen temperatures. A Pt/$TiO_2$ catalyst prepared by using an ion-exchange method (IE) has much better activity for such CO oxidation because of smaller Pt nanoparticles, compared to a supported Pt obtained via an incipient wetness (IW). Supported $Co_3O_4$-only catalysts are very active for CO oxidation even at $100^{\circ}C$, but the use of $TiO_2$ as a support and the IW technique give the best performances. These effects on supports and preparation methods were indicated for $Co_3O_4$-Pt catalysts. Based on activity profiles of CO oxidation at $100^{\circ}C$ over a physical mixture of supported Pt and $Co_3O_4$ after activation under different conditions, and typical light-off temperatures of CO and unburned hydrocarbons in common TWCs as tested for $C_3H_8$ oxidation at $250^{\circ}C$ with a Pt-exchanged $SiO_2$ catalyst, this study may offer an useful approach to substitute $Co_3O_4$ for a part of platinum group metals, particularly Pt, thereby lowering the usage of the precious metals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.341-348
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• 1997

X-ray diffraction patterns of Pt/Co modulated films prepared by RF comagnetron sputtering method was investigated. Modulated films ([$Pt10.7\AA/Co2.8{\AA}{\times}{12}$]) were deposited on glass substrate with various sputtering conditions : sputtering with variations of gas pressures, sputtering with Xe instead Ar gas, and etching of the buffer layers. In order to obtain the structural information of Pt/Co modulated films, the structural model was constructed and calculated data of the model were compared with experimental ones. Comparison results showed that there were good agreements in satellite peak position and its intensity between them. This suggests that the realistic Pt/Co modulated film can be reproduced by our structure model.

• Journal of the Korean Magnetics Society
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• v.15 no.5
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• pp.276-281
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• 2005

We have investigated the effects of an external magnetic field on the growth direction and the grain size of electrochemically prepared CoPtP alloys. Electrodeposited CoPtP alloys were synthesized by appling an external magnetic field with 0 to 1 T to the perpendicular direction of the films. In the electrodeposited CoPtP alloys without external magnetic field, the growth direction of the alloys was mixed by fcc (111) and hop (002), but only hop (002) was observed in the alloys with 1 T external magnetic field. CoPtP alloys were grown as the columnar growth and the grain size increases with growing the alloys. With appling an external field, the grain size of the alloys was controlled less than 20 nm which is smaller than single domain of Co, and the easy axis of alloys, hcp (002) direction, was grown perpendicular to the films up to 200 nm. We could obtain the optimal thickness of the alloys and electrodeposition condition from the above results. Coercivity and squareness of CoPtP alloys taken out-of-plane are 6.1 kOe and 0.9, respectively. The magnetic properties of CoPtP alloys were measured by VSM, and the microstructural characterization and crystalline orientation measurement of the alloys were carried out by TEM and XRD.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.72-77
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• 1998

The effects of Al micro-bumps on the magnetic properties of CoCr(Pt)Ta/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by incorporating Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCr(Pt)/Ta grains, and the refinement of CoCr(Pt)/Ta grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCr(Pt)Ta/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCr(Pt)Ta grains.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.143.2-143.2
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• 2016

The influence of electric field on CO adsorbed on Pt(111) was investigated with reflection-absorption infrared spectroscopy (RAIRS) in ultrahigh vacuum system. The ice film capacitor method was used to apply electric field to the amorphous ice film with CO on Pt(111). Two systems were compared by measuring the change of the CO stretching vibrational mode under applied electric field; one is CO on Pt(111), and the other is CO buried inside an ice film on Pt(111). By comparing them, we were able to calculate the additional effect of adsorption of CO on Pt(111) on peak shift. The CO adsorbed on Pt(111) has shown larger peak shift than CO adsorbed with H2O when we applied stronger electric field. Additionally, the differences were observable when the applied electric field exceeds $1{\times}10V/m^8$.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.433-437
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• 2006

Pt/Nafion self-humidifying membranes for Polymer Electrolyte Membrane Fuel Cell(PEMFC) were synthesized via supercritical-impregnation methods. The Nafion 112 membranes were impregnated with Pt(II)$(acetylacetonate)_2$ from a supercritical carbon dioxide $(scCO_2)$ solution at $80^{\circ}C$ and 30MPa. After the impregnation, the pressure decreased slowly by releasing $CO_2$. And the Pt-impregnated Nafion membrane was converted Pt deposited Nafion membrane by reducing agent, sodium borohydride $(NaBH_4)$ with various concentrations under $50^{\circ}C$ and 2 hours. The prepared Pt-impregnated Nafion (Pt/Nafion) composite membrane were investigated by Electron Prove Micro analysis (EPMA) and X-rat Diffraction analysis (XRD) which showed distribution of Pt particle and Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) a which revealed morphology of surface of Pt/Nafion composite membrane. The performance of the Pt/Nafion 112 membranes was examined in PEMFC as aself-humidifyin membranes using purpose-built equipment.