• Korean Journal of Materials Research
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• v.30 no.8
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• pp.421-425
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• 2020

A transparent quantum dot (QD)-based light-emitting diode (LED) with silver nanowire (Ag NW) and indium-tin oxide (ITO) hybrid electrode is demonstrated. The device consists of an Ag NW-ITO hybrid cathode (-), zinc oxide, poly (9-vinylcarbazole) (PVK), CdSe/CdZnS QD, tungsten trioxide, and ITO anode (+). The device shows pure green-color emission peaking at 548 nm, with a narrow spectral half width of 43 nm. Devices with hybrid cathodes show better performances, including higher luminance with higher current density, and lower threshold voltage of 5 V, compared with the reference device with a pure Ag NW cathode. It is worth noting that our transparent device with hybrid cathode exhibits a lifetime 9,300 seconds longer than that of a device with Ag NW cathode. This is the reason that the ITO overlayer can protect against oxidization of Ag NW, and the Ag NW underlayer can reduce the junction resistance and spread the current efficiently. The hybrid cathode for our transparent QD LED can applicable to other quantum structure-based optical devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.71-74
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• 2003

Photoconductor for direct detection fiat-panel imager present a great materials challenge, since their requirement include high X-ray absorption, ionization and charge collection, low leakage current and large area deposition, CdTe is practical material. We report studies of detector sensitivity, That is an CdTe with $5{\mu}m$ thickness on glass. That is hybrid layer of depositting ZnS:AgCl phosphor with $100{\mu}m$ on CdTe. The leakage current of hybrid is similar to it of a-Se, but photocurrent is larger than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

• Journal of Radiation Protection and Research
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• v.31 no.3
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• pp.123-128
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• 2006

A small radiation detection system is necessary for the direct characterization of alpha/beta-ray contamination inside pipes generated during the decommission of a nuclear facility. In this work, the new type phoswich detector consisting of the ZnS(Ag) and plastic scintillator for ${\alpha}/{\beta}$ simultaneous counting was designed as part of a development of a equipment capable of monitoring radiological contamination inside pipes. The optimum counting conditions in dimensions of scintillator and a detection system were experimentally confirmed and a performance of alpha/beta-ray discrimination was evaluated. As a result, optimum conditions of a detector suitable for monitoring radiological contamination inside pipes and a feasibility of application to pipe-inside were confirmed.

• Journal of Radiation Protection and Research
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• v.46 no.4
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• pp.194-203
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• 2021

Background: Surface soil radiation monitoring around nuclear facilities is important to classify and characterize the contaminated areas. A scanning and direct measurement technique can survey the sites rapidly before starting sampling analysis. Materials and Methods: Regarding this, we test and suggest a measurement technique for gross alpha/beta and ⁹⁰Sr activities in surface soil based on a mobile ZnS(Ag)/PVT (polyvinyltoluene) array and a handheld PVT rod, respectively. To detect ⁹⁰Sr selectively in soil mixed with naturally occurring radioactive materials, chosen energy channel counts from the multichannel analyzers were used instead of whole channel counts. Soil samples contaminated with exempt liquid ⁹⁰Sr with 1 Bq·g^-1, 3 Bq·g^-1, and 10 Bq·g^-1 were prepared and hardened by flocculation. Results and Discussion: The mobile ZnS(Ag)/PVT array could discriminate gross alpha, gross beta, and gamma radiation by the different pulse-shaped signal features of each sensor material. If the array is deployed on a vehicle, the scan minimum detectable concentration (MDC) range will be about 0.11-0.17 Bq·g^-1 at 18 km·h^-1 speed, highly sensitive to actual sites. The handheld PVT rod with 12 mm (Φ) × 20 mm (H) size can directly measure ⁹⁰Sr selectively if channels on which energies are from 1,470 and 2,279 keV are gated, minimizing crossdetection of other radionuclides. These methods were verified by measuring soil samples fabricated with homogeneous ⁹⁰Sr concentrations, showing static MDC of 2.16 Bq·g^-1 at a measurement time of 300 seconds. Conclusion: Based on the results, comprehensive procedures using these detectors are suggested to optimize soil sites survey.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.421-426
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• 1995

The magnetic properties of the hot-pressed magnets made from the Fe-Nd-B alloys, mechanically ground and subsequently blended with binary additives such as Al-Cu and Ag-Zn before hot pressing, were investigated. The coercivities of the magnets increased as the concentration of Al-Cu increased up to 1 wt.% or up to 3 wt.% in the case of Ag-Zn. At higher concentrations the coercivities decreased markedly. The maximum gain in coercivity by the addition was about 20 %. typical values of $_{i}H_{c}$ and $B_{r}$ of a hotpressed magnet containing 1 wt.% Al-Cu were 18 kOe and 7 kG, respectively. It was found that Cu, Ag, and Zn, which diffused into the magnet during hot pressing, were mostly concentrated on the Nd-rich grain boundary phase whereas Al was present not only in the grain boundary region but also in the matrix grains.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.3
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• pp.1-13
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• 2010

The aim of this study is to analyze gold-silver mineral potential in the Taebaeksan mineralized district, Korea using a Geographic Information System(GIS) and an artificial neural network(ANN) model. A spatial database considering Au and Ag deposit, geology, fault structure and geochemical data of As, Cu, Mo, Ni, Pb and Zn was constructed for the study area using the GIS. The 46 Au and Ag mineral deposits were randomly divided into a training set to analyze mineral potential using ANN and a test set to verify mineral potential map. In the ANN model, training sets for areas with mineral deposits and without them were selected randomly from the lower 10% areas of the mineral potential index derived from existing mineral deposits using likelihood ratio. To support the reliability of the Au-Ag mineral potential map, some of rock samples were selected in the upper 5% areas of the mineral potential index without known deposits and analyzed for Au, Ag, As, Cu, Pb and Zn. As the result, No. 4 of sample exhibited more enrichments of all elements than the others.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.27-30
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• 2002

Photoconductor for direct detection flat-panel imager present a great materials challenge, since their requirements include high X -ray absorption, ionization and charge collection, low leakage current and large area deposition. Selenium is practical material. But it needs high thickness and high voltage in selenium for high ionization rate. We report comparative studies of detector sensitivity. One is an a-Se with $70{\mu}m$ thickness on glass. The other has hybrid layer of depositting ZnS phosphor with $100{\mu}m$ on a-Se. The leakage current of hybrid is similar to it of a-Se, but photocurrent is lager than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

• Journal of the Korean institute of surface engineering
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• v.41 no.4
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• pp.169-173
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• 2008

The objective of this study is to coat the $SiO_2$ layer uniformly on the ZnS:Cu phosphors by using Sol-Gel method. From results of SEM micrographs observation, XRD and XPS analysis, it could be confirmed that $SiO_2$ layer was relatively well coated on ZnS:Cu particles. $Ag_2S$ was used as a decoding chemical to analyze the dense and uniform coating performance of $SiO_2$ layer on phosphor particles. It could be concluded that phosphors synthesized from our two step replacement method showed strong blue peak comparing to other method and rather weak green peak also. Obtained particle size of phosphors were about 20m diameter. Luminescence properties of the phosphors were examined by photoluminescence spectra at the excitation wavelength of 270 nm.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3723-3729
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• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.604-608
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• 2006

Polymer composites for measuring the radioactive contamination are prepared by coating ZnS(Ag) powders as a scintillator on polysulfone base layer. The composites consist of the active layer for a scintillation reaction with radioactive wastes and the transparent support layer for transmittance of light photons emitted by scintillation in the active layer. The binding of the active layer, including ZnS(Ag), on the support layer is proceeded via coating with polysulfone as a binder, without any extra adhesive. The coating was obtained by either casting via a Doctor Blade as applicator or screen printing. The prepared composites feature a monolithic structure, resulting in the complete adhesion between two layers. The composite prepared by the casting technique using an applicator holds a good detection efficiency in measuring the alpha radionuclide, but its structure becomes fragile because of warping in morphology. On the contrary, the composite prepared by the screen printing shows a good detection capacity as well as a good stability in a mechanical shape.