• Korean Journal of Materials Research
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• v.26 no.8
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• pp.417-421
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• 2016

We improve the energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC) by preparing a working electrode (WE) with localized surface plasmon resonance (LSPR) by inducing Au thin films with thickness of 0.0 to 5.0 nm, deposited via sputtering. Field emission scanning electron microscopy and atomic force microscopy were used to characterize the microstructure of the blocking layer (BL) of the Au thin films. Micro-Raman measurement was employed to confirm the LSPR effect, and a solar simulator and potentiostat were used to evaluate the photovoltaic properties, including the impedance and the I-V of the DSSC of the Au thin films. The results of the microstructural analysis confirmed that nano-sized Au agglomerates were present at certain thicknesses. The photovoltaic results show that the ECE reached a value of 5.34% with a 1-nm thick-Au thin film compared to the value of 5.15 % without the Au thin film. This improvement was a result of the increase in the LSPR of the $TiO_2$ layer that resulted from the Au thin film coating. Our results imply that the ECE of a DSSC may be improved by coating with a proper thickness of Au thin film on the BL.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.343-348
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• 2018

Recently, the properties of nanostructured materials as advanced engineering materials have received great attention. These properties include fracture toughness and a high degree of hardness. To hinder grain growth during sintering, it is necessary to fabricate nanostructured materials. In this respect, a high-frequency induction-heated sintering method has been presented as an effective technique for making nanostructured materials at a lower temperature in a very short heating period. Nanopowders of W and $Al_2O_3$ are synthesized from $WO_3$ and Al powders during high-energy ball milling. Highly dense nanostructured $W-Al_2O_3$ composites are made within three minutes by high-frequency induction-heated sintering method and materials are evaluated in terms of hardness, fracture toughness, and microstructure. The hardness and fracture toughness of the composite are $1364kg/mm^2$ and $7.1MPa{\cdot}m^{1/2}$, respectively. Fracture toughness of nanostructured $W-Al_2O_3$ is higher than that of monolithic $Al_2O_3$. The hardness of this composite is higher than that of monolithic W.

• Applied Microscopy
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• v.43 no.2
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• pp.65-74
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• 2013

Although the geometrical difference in body position between web-building and wandering spiders could affect the organization of their central nervous system (CNS), however most of our informations about spider's CNS are dependent on those revealed from the wandering spiders. Therefore, this paper describes microstructural organizations of the CNS in the geometric orb-web spider Araneus ventricosus. Similarly to other wandering spiders, the CNS of A. ventricosus is also consisted of a dorsal supraesophageal ganglion and a ventral subesophageal mass. The supraesophageal ganglia are fused together and made up of a large sized nerve cell clusters, whereas the subesophageal ganglia are made up of the foremost part of the ventral nerve cord. It has been revealed that the only nerve arising from the supraesophageal mass was the optic nerve which connected with four pairs of eyes, whereas a pair of pedipalpal and four pairs of appendage nerves including abdominal nerve pairs were arisen from the subesophageal nerve mass. Fibrous masses are highly organized into longitudinal and transverse tracts, and are only consisted of processes of neurons and the terminal ramnifications of peripheral sensory neurons. In addition, central fibrous mass of both the brain and the subesophageal mass are totally devoid of nerve cell bodies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.308-311
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• 2003

The mesoporous TiO2 film for the dye-sensitized solar cell was prepared by the spin coating using nano particle $TiO_2$ slurry. In order to obtain the good dispersion of nano size $TiO_2$ particles in slurry, the pH of solvent, the sort and quantity of solvent additive and the quantity of surfactant were adjusted. The experimental range of pH was $2\;{\sim}\;4$. The basic solvent for slurry was dilute $HNO_3$ and the solvent additives were ethylene glycol, propylene glycol and butylene glycol. The degree of particle dispersion was indirectly estimated by the viscosity of slurry and the microstructure after sintering. As results, the lower the pH of solvent was the lower the viscosity of the slurry became. The addition of ethylene glycol and propylene glycol to dilute $HNO_3$ brought about the lowering of viscosity and the enhancement of stability in slurry. The addition of surfactant lowered the viscosity of slurry. It was possible to obtain the homogeneous and uniformly dispersed mesoporous TiO2 film using the dilute HNO3 solvent of pH 2 with the addition of ethylene glycol, propylene glycol and neutral surfactant.

• Journal of Powder Materials
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• v.21 no.3
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• pp.222-228
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• 2014

Much research into fuel cells operating at a temperature below $800^{\circ}C$. is being performed. There are significant efforts to replace the yttria-stabilized zirconia electrolyte with a doped ceria electrolyte that has high ionic conductivity even at a lower temperature. Even if the doped ceria electrolyte has high ionic conductivity, it also shows high electronic conductivity in a reducing environment, therefore, when used as a solid electrolyte of a fuel cell, the powergeneration efficiency and mechanical properties of the fuel cell may be degraded. In this study, gadolinium-doped ceria nanopowder with $Al_2O_3$ and $Mn_2O_3$ as a reinforcing and electron trapping agents were synthesized by ultrasonic pyrolysis process. After firing, their microstructure and mechanical and electrical properties were investigated and compared with those of pure gadolinium-doped ceria specimen.

• The Korean Journal of Food And Nutrition
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• v.6 no.3
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• pp.178-188
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• 1993

This research was attempted to investigate changes in physicochemical properties of rice extrudate with added ginger powder extruded by single screw extruder. Graphic three dimensional analysis on response surface regression was used to evaluate effects of extrusion variables on quality factors of the extrudate according to two independent variables, ginger consent 0∼12%, moisture content 14∼26%. The summarized results are as follows : 1) Regarding proximate composition of rice extrudate with added ginger powder, as ginger powder content of raw material Increased, crude tat, crude protein, crude ash and crude fiber increased, while soluble nitrogen free extract decreased. 2) Graphic three dimensional analysis on response surface regression was conducted for each dependent variable which revealed statistically significant relationship with independent variables, 0∼120A ginger and 14∼26% moisture content. Expansion ratio had a critical point as moisture content changed. As ginger and moisture content Increased, bulk density, break strength and water absorption Index Increased, while water solubility Index decreased. The predicted maximum degree of gelatinization in 6.15% ginger and 15.56% moisture content is 88.27%, and lightness decreased as ginger content Increased. According to the microstructure for the cross section of extrudate obsorbed with image analyzer, air cell number and perimeter revealed saddle point, meanwhile total area and fractarea of air cell had critical points as moisture content changed. In view of the results, quality of rice extrudate with added ginger powder was optimum when rice flour was fed to the extruder with 2∼7% singer powder and 15∼20% moisture content.

• Korean Journal of Materials Research
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• v.17 no.8
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• pp.397-401
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• 2007

Fe based SOFC(Solid Oxide Fuel Cell) interconnector was fabricated by using the spark plasma sintering process and its microstructure and mechanical properties were investigated in this study. To fabricate the interconnector, the Fe-26Cr powder was mixed with the Ag (5, 10, 20wt.%) particles. In the Fe-26Cr-Ag sintered bodies, the Ag particles were almost dispersed at the grain boundary of the Fe-26Cr. The sintered bodies have the density of 87.2-97.5%, the density increases with increasing Ag content at sintering temperature of $850^{\circ}C$. Also, the compressive yield strength increases with increasing Ag content at the same sintering temperature.

• Food Science and Preservation
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• v.9 no.2
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• pp.221-227
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• 2002

Effects of adding of dandelion flour on the quality characteristics of bread were investigated. Dandelion flour was substituted at levels of 0, 0.5, 1.0, 2.0% to wheat flour for bread making, respectively. Quality characteristics of bread such as dough yield, dough microstructure, loaf volume, bread yield, crumb color, mechanical property and sensory evaluation were analyzed. Addition of dandelion flour to wheat flour increased dough yield, loaf volume and bread yield. And, addition of dandelion flour caused a decrease in the lightness and an increase in the redness. The results of texture evaluation revealed that hardness, chewiness, springiness of bread increased as the level of dandelion flour was increased. As the addition level of dandelion flour increased, flavor balance, bitterness, aftertaste, grassy odor of bread increased but overall acceptability, moistness decreased. In conclusion, bread with 0.5% leaf powder was the best quality in bread properties.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.775-780
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• 2006

Mechanical and electrical performance of anode-supported SOFC single cells were analyzed after thermal cyclic operation. The experiments of thermal cyclic cell-operation were carried out four times and performance of each cell was measured at different temperatures of 650, 700, and $750^{\circ}C$, respectively. As increasing the number of thermal cycle test, single cells showed poor I-V characteristics and lower 4-point bending strength. The anode polarization was also measured by AC-impedance analysis. The observation of the microstructure of the anodes in single cells proved that the average particle size of Ni decreased and the porosity of anode increased. It is thought that the thermal cycle caused the degradation of performance of single cells by reducing the density of three-phase boundary region.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.595-600
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• 2020

The photovoltaic properties of perovskite solar cells (PSCs) with a carbon electrode fabricated using different annealing processes are investigated. Perovskite formation (50 ℃, 60 min) using a hot-plate and an oven is carried out on cells with a glass/fluorine doped TiO₂/TiO₂/ZrO₂/carbon structure, and the photovoltaic properties of the PSCs are analyzed using a solar simulator. The microstructures of the PSCs are characterized using an optical microscope, a field emission scanning electron microscope, and an electron probe micro-analyzer (EPMA). Photovoltaic analysis shows that the energy conversion efficiency of the samples fabricated using the hot-plate and the oven processes are 2.08% and 6.90%, respectively. Based on the microstructure of the samples and the results of the EPMA, perovskite is formed locally on the carbon electrode surface as the γ-butyrolactone (GBL) solvent evaporates and moves to the top of the carbon electrode due to heat from the bottom of the sample during the hot plate process. When the oven process is used, perovskite forms evenly inside the carbon electrode, as the GBL solvent evaporates extremely slowly because heat is supplied from all directions. The importance of the even formation of perovskite inside the carbon electrode is emphasized, and the feasibility of oven annealing is confirmed for PSCs with carbon electrodes.