• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.34-39
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• 2018

In this study, e-beam equipment was used to form silver nanoparticles on thin films of $TiO_2$ to increase the efficiency of dye-sensitized solar cells and improve the annealing process. $TiO_2$ thin films with nanoparticle photoelectrodes were fabricated in individual units for use in dye-sensitized solar cells. The characteristics of dye-sensitized solar cells were compared to those of the prepared $TiO_2$ photoelectrode with and without nanoparticles. The dye-sensitized solar cells with silver nanoparticles showed a significant increase in the electric current density compared with the pure $TiO_2$ dye-sensitized solar cell and improved the solar conversion efficiency to 27.89%. The increased density of electric current increased the extent of light absorption of the dye owing to the plasmon resonance of the nanoparticles at the local surfaces. This phenomenon led to increased light scattering, which in turn increased the current density of the dye-sensitized solar cells and improved the solar conversion efficiency.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.682-688
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• 2016

In $TiO_2$-CuO systems, low-temperature sinterability was investigated by a conventional sintering method. Sintering temperatures were set at under $950^{\circ}C$, at which the volume diffusion is inactive. The temperatures are less than the melting point of Ag ($961^{\circ}C$), which is often used as an internal conductor in low-temperature co-fired ceramic technology. To optimize the amount of CuO dopant, various dopant contents were added. The optimum level for enhanced densification was 2 wt% CuO. Excess dopants were segregated to the grain boundaries. The segregated dopants supplied a high diffusion path, by which grain boundary diffusion improved. At lower temperatures in the solid state region, grain boundary diffusion was the principal mass transport mechanism for densification. The enhanced grain boundary diffusion, therefore, improved densification. In this regard, the results of this study prove that the sintering mechanism was the same as that of activated sintering.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.921-925
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• 2000

Characteristics of Pb(Mg, Nb)O$_3$-Pb(Zr, Ti)O$_3$system thick films fabricated by a screen printing method were investigated. The buffer layer were coated with various thickness of Ag-Pd by screen printing to investigate the effect as a diffusion barrier and deposited Pt as a electrode by sputtering on Ag-Pb layer. The printed thick films were burned out at 650$\^{C}$ and sintered at 950$\^{C}$ in O$_2$condition for each 20, 60min after printing with 350mesh screen. The thickness of piezoelectric thick film was 15∼20㎛ and Ag-Pb layer acted as a diffusion barrier above 3㎛ thickness. The PMN-PZT thick films were screen printed on Pt/Ag-Pb(6m) and sintered by 2nd step (650$\^{C}$/20min and 950$\^{C}$/1h) using paste mixed PMN-PZT and binder in the ratio of 70:30, and the remnant polarization of thick film was 9.1$\mu$C/㎠ in this conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.9-14
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• 2008

A Nano particle is a small particle with at least one dimension less than 100 nm Nanoparticle is currently used in an area cf intense scientific research, due to a wide variety cf potential applications in biomedical, optical, and electronic fields. In order to know the biological effect of the nine Nano particles on fertilized egg of Crassostrea gigas experiments were performed Development rates of control (free Nano particles) C. gigas to a particular larval stage (D-shape) was 78%. Development rate of C gigas to a parcicular larval stage (D-shape) after 24 hours exposure to 0.05ppm of AGZ020, Nano silver, P-25 and SnO were 22%, 52%, 58% and 76%, respectively. However, all fertilized eggs were destructed within 8 hours afters exposure to 20ppm of respective particles. On the other hand, All fertilized eggs were not affected after 24 hours respective exposure to 0.05ppm of In, Sb, Sn, Zn, and Ag-$TiO_2$ particles. However, development rates of C. gigas after 24 hours exposure to 20ppm of In, Sb, Sn, Zn, Ag-$TiO_2$ were 57%, 60%, 50%, 65%, and 64% respectively.

• Clean Technology
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• v.17 no.3
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• pp.225-230
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• 2011

Characteristics of hydrocarbon selective catalytic reduction of NOx using various noble metal catalysts were investigated. The best active metal is Pt, supports are $CeO_2$ and $TiO_2$ by strong interactions between active metals, and 55% of conversion rate of NOx is shown. Pd, Rh and Ag catalysts presented a conversion of less than 20% as active metals, and supports also showed the poor activity compared to $SiO_2$ and $ZrO_2$. Experiments were performed with different types of reducing agents, amount, concentration of oxygen and space velocity in order to investigate the performance of catalysts according to operating conditions. The results confirm that the methane is better than propane as a reducing agent, and as the ratio of methane/nitrogen oxide increases, the catalytic activity increased, as the concentration of oxygen increases and space velocity decreases, the performance of catalysts increased.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.185-197
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• 2023

The Gubong Au-Ag deposit consists of eight lens-shaped quartz veins. These veins have filled fractures along fault zones within Precambrian metasedimentary rock. This has been one of the largest deposits in Korea, and is geologically a mix of orogenic-type and intrusion-related types. Korea Mining Promotion Corporation drilled into a quartz vein (referred to as the No. 6 vein) with a width of 0.9 m and a grade of 27.9 g/t Au at a depth of -728 ML by drilling (No. 90-12) in the southern site of the deposit, To further investigate the potential redevelopment of the No. 6 vein, another drilling (No. 04-1) was carried out in 2004. In 2004, samples (wallrock, wallrock alteration and quartz vein) were collected from the No. 04-1 drilling core site to study the occurrence and chemical composition of Ti-bearing minerals (ilmenite, rutile). Rutile from mineralized zone at a depth of -275 ML occur minerals including K-feldspar, biotite, quartz, calcite, chlorite, pyrite in wallrock alteration zone. Ilmenite and rutile from ore vein (No. 6 vein) at a depth of -779 ML occur minerals including white mica, chlorite, apatite, zircon, quartz, calcite, pyrrhotite, pyrite in wallrock alteration zone and quartz vein. Based on mineral assemblage, rutile was formed by hydrothermal alteration (chloritization) of Ti-rich biotite in the wallrock. Chemical composition of ilmenite has maximum values of 0.09 wt.% (HfO₂), 0.39 wt.% (V₂O₃) and 0.54 wt.% (BaO). Comparing the chemical composition of rutile at a depth -275 ML and -779 ML, Rutile at a depth of -779 ML is higher contents (WO₃, FeO and BaO) than rutile at a depth of -275 ML. The substitutions of rutile at a depth of -275 ML and -779 ML are as followed : rutile at a depth of -275 ML Ba²⁺ + Al³⁺ + Hf⁴⁺ + (Nb⁵⁺, Ta⁵⁺) ↔ 3Ti⁴⁺ + Fe²⁺, 2V⁴⁺ + (W⁵⁺, Ta⁵⁺, Nb⁵⁺) ↔ 2Ti⁴⁺ + Al³⁺ + (Fe²⁺, Ba²⁺), Al³⁺ + V⁴⁺+ (Nb⁵⁺, Ta⁵⁺) ↔ 2Ti⁴⁺ + 2Fe²⁺, rutile at a depth of -779 ML 2 (Fe²⁺, Ba²⁺) + Al³⁺ + (W⁵⁺, Nb⁵⁺, Ta⁵⁺) ↔ 2Ti⁴⁺ + (V⁴⁺, Hf⁴⁺), Fe²⁺ + Al³⁺ + Hf ⁴⁺ + (W⁵⁺, Nb⁵⁺, Ta⁵⁺) ↔ 2Ti⁴⁺ + V⁴⁺ + Ba²⁺, respectively. Based on these data and chemical composition of rutiles from orogenic-type deposits, rutiles from Gubong deposit was formed in a relatively oxidizing environment than the rutile from orogenictype deposits (Unsan deposit, Kori Kollo deposit, Big Bell deposit, Meguma gold-bearing quartz vein).

• Journal of Welding and Joining
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• v.10 no.3
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• pp.63-72
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• 1992

The joining methods of ceramics to metals which can be expected to obtain high temperature strength are mainly classified into the solid-state diffusion bonding method and the active brazing method. Between these two, the solid-state diffusion bonding method is given attentions as substituting method for active brazing method due to being capable of obtaining higher bonding strength at high temperature and accurate bonding. In this paper, the solid-state diffusion bonding of $Al_{2}$O$_{3}$ ceramics to Ni-Cr-Mo alloy steel (SNCM21) using insert metal was carried out. The insert metal employed in this study was experimentally home-made, Ag-Cu-Ti alloy. Influence of several bonding parameters of $Al_{2}$O$_{3}$SNCM21 joint was quantitatively evaluated by bonding strength test, and microstructural analyses at the interlayer were performed by SEM/EDX. From above experiments, the optimum bonding condition of the solid-state diffusion bonding of $Al_{2}$O$_{3}$/SNCM21 using Ag-Cu-Ti insert metal was determined. Futhermore, high temperature strength and thermal-shock properties of $Al_{2}$O$_{3}$/SNCM21 joint were also examined. The results obtained are as follows. 1. The maximum bonding strength was obtained at the temperature of 95% melting point of insert metal. 2. The high temperature strength of $Al_{2}$O$_{3}$/SNCM21 joint appeared to bemaximum value at test temperature 500.deg.C and the bonding strength with increasingtemperature showed parabolic curve. 3. The strength of thermal-shocked specimens was far deteriorated than those of as-bonded specimens. Especially, water-quenched specimen after heated up to 600.deg. C was directly fractured in quenching.

• Transactions on Electrical and Electronic Materials
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• v.14 no.2
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• pp.78-81
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• 2013

$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3+0.2wt%\;Ag_2O$ (hereafter, No excess NKN) ceramics and $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3+0.2wt%\;Ag_2O$ with excess $(Na_{0.5}K_{0.5})NbO_3$ (hereafter, Excess NKN) were fabricated by the conventional solid state sintering method, and their phase transition properties and dielectric properties were investigated. The crystalline structure of No excess NKN ceramics and Excess NKN ceramics were shown characteristics of polymorphic phase transition (hereafter, PPT), especially shift from the orthorhombic to tetragonal phase by increasing sintering temperature range from $1,100^{\circ}C$ to $1,200^{\circ}C$. Also, the temperature coefficient of capacitance (hereafter, TCC) of No excess NKN ceramics and Excess NKN ceramics from $-40^{\circ}C$ to $100^{\circ}C$ was measured to evaluate temperature stability for applications in cold regions. The TCC of No excess NKN and Excess NKN ceramics showed positive TCC characteristics at a temperature range from $-40^{\circ}C$ to $100^{\circ}C$. Especially, Excess NKN showed a smaller TCC gradient than those of Excess NKN ceramics in range from $-40^{\circ}C$ to $100^{\circ}C$. Therefore, NKN piezoelectric ceramics combined with temperature compensated capacitor having negative temperature characteristics is desired for usage in cold regions.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.373-373
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• 2014

Resistive-change random access memory (ReRAM) device is one of the promising candidates owing to its simple structure, high scalability potential and low power operation. Many resistive switching devices using transition metal oxides materials such as NiO, Al2O3, ZnO, HfO2, $TiO_2$, have attracting increased attention in recent years as the next-generation nonvolatile memory. Among various transition metal oxides materials, HfO2 has been adopted as the gate dielectric in advanced Si devices. For this reason, it is advantageous to develop an HfO2-based ReRAM devices to leverage its compatibility with Si. However, the annealing temperature of these high-k thin films for a suitable resistive memory switching is high, so there are several reports for low temperature process including microwave irradiation. In this paper, we demonstrate the bipolar resistive switching characteristics in the microwave irradiation annealing processed Ag/HfO2/Pt ReRAM device. Compared to the as-deposited Ag/HfO2/Pt device, highly improved uniformity of resistance values and operating voltage were obtained from the micro wave annealing processed HfO2 ReRAM device. In addition, a stable DC endurance (>100 cycles) and a high data retention (>104 sec) were achieved.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.151-156
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• 1995

Low temperature firing $(Ba, Sr)TiO_{3}$ dielectrics were successfully prepared with lead based glass and those electrical properties were investigated. Different amount of PbO content glass materials were added to dielectrics to investigate the sinterability and its dielectric properties. Also, various compositions of ceramic capacitors were prepared to applicate in multilayer ceramic capacitors. A large amount of experiment has been done with various Pb contented glasses and different sintering temperatures. The sintering temperature of $(Ba,Sr)TiO_{3}$can be reduced from $1350^{\circ}C$to as low as $1050^{\circ}C$ with 4wt% addition of $PbO-ZnO-B_{2}O_{2}$ glass materials. Its dielectric constant at room temperature was up to 8100 with low dielectric loss, 0.005. This ceramic capacitor showed fully fired microstructures with its grain size of 1-3$\mu \textrm{m}$. The sintered body which was sintered at $1150^{\circ}C$ for 2hr with 4wt% $PbO-ZnO-B_{2}O_{2}$ glass material addition satisfied the Z5U specification of the EIAS.