• Korean Journal of Materials Research
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• v.26 no.4
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• pp.207-211
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• 2016

Ti films were deposited on glass substrates under various preparation conditions in a chamber of two-facing-target type dc sputtering; after deposition, the electric resistivity values were measured using a conventional four-probe method. Crystallographic orientations and microstructures, including the texture and columnar structure, were also investigated for the Ti films. The morphological features, including the columnar structures and surface roughness, are well explained on the basis of Thornton's zone model. The electric resistivity and the thermal coefficient of the resistivity vary with the sputtering gas pressure. The minimum value of resistivity was around 0.4 Pa for both the $0.5{\mu}m$ and $3.0{\mu}m$ thick films; the apparent tendencies are almost the same for the two films, with a small difference in resistivity because of the different film thicknesses. The films deposited at high gas pressures show higher resistivities. The maximum of TCR is also around 0.4 Pa, which is the same as that obtained from the relationship between the resistivity and the gas pressure. The lattice spacing also decreases with increasing sputtering gas pressure for both the $0.5{\mu}m$ and $3.0{\mu}m$ thick films. Because they are strongly related to the sputtering gas pressures for Ti films that have a crystallographic anisotropy that is different from cubic symmetry, these changes are well explained on the basis of the film microstructures. It is shown that resistivity measurement can serve as a promising monitor for microstructures in sputtered Ti films.

• Ocean and Polar Research
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• v.33 no.2
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• pp.159-169
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• 2011

Antifreeze proteins (AFPs) have ice binding affinity, depress freezing temperature and inhibit ice recystallization which protect cellular membranes in polar organisms. Recent structural studies of antifreeze proteins have significantly expanded our understanding of the structure-function relationship and ice crystal growth inhibition. Although AFPs (Type I-IV AFP from fish, insect AFP and Plant AFP) have completely different fold and no sequence homology, they share a common feature of their surface area for ice binding property. The conserved ice-binding sites are relatively flat and hydrophobic. For example, Type I AFP has an amphipathic, single ${\alpha}$-helix and has regularly spaced Thr-Ala residues which make direct interaction with oxygen atoms of ice crystals. Unlike Type I AFP, Type II and III AFP are compact globular proteins that contain a flat ice-binding patch on the surface. Type II and Type III AFP show a remarkable structural similarity with the sugar binding lectin protein and C-terminal domain of sialic acid synthase, respectively. Type IV is assumed to form a four-helix bundle which has sequence similarity with apolipoprotein. The results of our modeling suggest an ice-binding induced structural change of Type IV AFP. Insect AFP has ${\beta}$-helical structure with a regular array of Thr-X-Thr motif. Threonine residues of each Thr-X-Thr motif fit well into the ice crystal lattice and provide a good surface-surface complementarity. This review focuses on the structural characteristics and details of the ice-binding mechanism of antifreeze proteins.

• Clean Technology
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• v.23 no.1
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• pp.64-72
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• 2017

In this study, the selective catalytic reduction (SCR) for NOx removal was investigated in the temperature range of $150{\sim}400^{\circ}C$. XRD, BET and XPS analyses to determine the structural properties and valence state characteristics of the catalyst were performed. Various ball mill method were shown to a difference in activity at a low temperature below $250^{\circ}C$. Based on the catalyst with the highest denitrification efficiency, the ball mill time was the best result at 3 h. As a result of XPS analysis, the presence of the non-stoichiometric vanadium species and the increase of the number of atoms were attributed to a positive effect in the SCR reaction. it was confirmed that the correlation between the amount of lattice oxygen and the denitrification efficiency through the $O_2$ on-off experiment, and it was in a proportional relationship to each other.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.696-702
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• 2007

The family of (Sr,Mg)-doped $LaGaO_3$ compounds, which exhibit high ionic conductivity at $600-800^{\circ}C$ over a wide range of oxygen partial pressure, appears to be promising as the electrolyte for intermediate temperature solid oxide fuel cells. Conventional synthesis routes of (Sr,Mg)-doped $LaGaO_3$ compounds based on solid state reaction have some problems such as the formation of impurity phases, long sintering time and Ga loss during high temperature sintering. Phase stability problem especially, the formation of additional phases at the grain boundary is detrimental to the electrical properties of the electrolyte. From this point of view, we focused to synthesize single phase (Sr,Mg)-doped $LaGaO_3$ electrolyte at the stage of powder synthesis and to apply relatively low heat-treatment temperature using novel synthesis route based on combustion method. The synthesized powder and sintered bulk electrolytes were characterized by XRD, TG-DTA, FT-IR and SEM. AC impedance spectroscopy was used to characterize the electrical transport properties of the electrolyte with the consideration of the contribution of the bulk lattice and grain boundary to the total conductivity. Finally, relationship between synthesis condition and electrical properties of the (Sr, Mg)-doped $LaGaO_3$ electrolytes was discussed with the consideration of phase analysis results.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.362-368
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• 2006

Epitaxial $Ba_{0.5}Sr_{0.5}TiO_3$ (BSTO) thin films have been grown on TiN buffered Si (001) substrates by Pulsed Laser Deposition (PLD) method and the effects of substrate temperature and oxygen partial pressure during the deposition on their dielectric properties and crystallinity were investigated. The crystal orientation, epitaxy nature, and microstructure of oxide thin films were investigated using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Thin films were prepared with laser fluence of $4.2\;J/cm^2\;and\;3\;J/cm^2$, repetition rate of 8 Hz and 10 Hz, substrate temperatures of $700^{\circ}C$ and ranging from $350^{\circ}C\;to\;700^{\circ}C$ for TiN and oxide respectively. BSTO thin-films were grown on TiN-buffered Si substrates at various oxygen partial pressure ranging from $1{\times}10^{-4}$ torr to $1{\times}10^{-5}$ torr. The TiN buffer layer and BSTO thin films were grown with cube-on-cube epitaxial orientation relationship of $[110](001)_{BSTO}{\parallel}[110](001)_{TiN}{\parallel}[110](001)_{Si}$. The crystallinity of BSTO thin films was improved with increasing substrate temperature. C-axis lattice parameters of BSTO thin films, calculated from XRD ${\theta}-2{\theta}$ scans, decreased from 0.408 m to 0.404 nm and the dielectric constants of BSTO epitaxial thin films increased from 440 to 938 with increasing processing oxygen partial pressure.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.397-400
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• 2007

For mapping the distribution of heavy metals in the mining area, field spectroscopy and hyperspectral remote sensing were used in this study. Although heavy metals are spectrally featureless from the visible to the short wave infrared range, possible variations in spectral signal due to heavy metals bound onto minerals can be explained with the metal binding reaction onto the mineral surface. Variations in the spectral absorption shapes of lattice OH and oxygen on the mineral surface due to the combination of heavy metals were surveyed over the range from 420 to 2400 nm. Spectral parameters such as peak ratio and peak area were derived and statistically linked to metal concentration levels in the streambed samples collected from the dry stream channels. The spatial relationships between spectral parameters and concentrations of heavy metals were yielded as well. Based on the observation at a ground level for the relationship between spectral signal and metal concentration levels, the spectral parameters were classified in a hyperspectral image and the spatial distribution patterns of classified pixels were compared with the product of analysis at the ground level. The degree of similarity between ground dataset and image dataset was statistically validated. These techniques are expected to support assessment of dispersion of heavy metal contamination and decision on optimal sampling point.

• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1267-1273
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• 2009

The correlation between the sintering temperature and dielectric properties in the $Nb^{5+}\;and\;Ta^{5+}$ doped BaTi$O_3$ solid solutions have been investigated. The samples were sintered at temperatures ranging from 1250 to 1350 ${^{\circ}C}$ for 4 h in air. SEM, XRD and SEM/EDS techniques were used to examine the structure of the samples with particular focus on the incorporation of $Nb^{5+}\;and\;Ta^{5+}$ ions into the BaTi$O_3$ crystal lattice. The X-ray diffraction peaks of (111), (200) and (002) planes of BaTi$O_3$ solid solution doped with different fractions of $Nb^{5+}\;and\;Ta^{5+}$ were investigated. The dielectric properties were analyzed and the relationship between the properties and structure of doped BaTi$O_3$ was established. The fine-grain and high density of the doped BaTi$O_3$ ceramics resulted in excellent dielectric properties. The dielectric properties of this solid solutions were improved by adding a small amount of dopants. The transition temperature of the 1.0 mole% $Ta^{5+}$ doped BaTi$O_3$ solid solution was $\sim$110 ${^{\circ}C}$ with a dielectric constant of 3000 at room temperature. At temperatures above the Curie temperatures, the dielectric constant followed the Curie-Weiss law.

• Journal of the Korean Vacuum Society
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• v.7 no.4
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• pp.355-360
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• 1998

Epitaxial $Ba_{0.5}Sr_{0.5}TiO_3$thin films of two different thickness (~250 $\AA$ and ~1340 $\AA$) on MgO(001) prepared by a pulsed laser deposition method were studied by synchroton x-ray scattering measurements. The film initially grew on MgO(001) with a cube-on-cube relationship, maintaining it during further growth. As the film grew, the surface of the film became rough significantly, but the interface between the film and the substrate seemed to have changed little. In the early stage, the film was highly strained in a tetragonal structure with the longer axis parallel to the surface normal direction. As the growth proceeded further, it was mostly relaxed to a cubic structure with the lattice parameter of the bulk value and the mosaic distribution improved significantly in both in-plane and out-of-plane directions.

• Journal of Environmental Science International
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• v.25 no.5
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• pp.737-744
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• 2016

For electrolysis process using an insoluble electrode, electrochemical performance was greatly affected by the manufacturing method and procedure, such as the firing temperature, pre-treatment, type of precursor solution, coating method, electrode material, etc. Components of the electrode therein is one of the most important factors in electrochemical reaction. To achieve such characteristics, a appropriate ratio of the electrode material should be carefully chosen. The aim of this research was to apply experimental design method in the optimization of electrode component for the maximum generation of oxidants in electrochemical oxidation process. Mixture design, especially expanded simplex lattice design, in DOME (design of mixture experiments) with Design Expert - commercial software - was used to analyze the data. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9470, thus ensuring a satisfactory adjustment of the $3^{rd}$ order special cubic regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the TRO generation concentration and independent variables(mol ratio of 3 electrode components) in a real unit: TRO generation concentration $(mg/L)=TRO\;conc.=98.25{\times}[Ir]+49.71{\times}[Sn]+95.29{\times}[Sb]-16.91{\times}[Ir]{\times}[Sn]-29.47{\times}[Ir]{\times}[Sb]-22.65{\times}[Sn]{\times}[Sb]+703.19{\times}[Ir]{\times}[Sn]{\times}[Sb]$. The optimized formulation of the 3 component electrode for an high TRO (total residual oxidants) generation was acquired at mol ratio of Ir 0.406, Sn 0.210, Sb 0.384 (desirability d value, 1).

• Applied Microscopy
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• v.49
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• pp.3.1-3.7
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• 2019

Graphene, which is one of the most promising materials for its state-of-the-art applications, has received extensive attention because of its superior mechanical properties. However, there is little experimental evidence related to the mechanical properties of graphene at the atomic level because of the challenges associated with transferring atomically-thin two-dimensional (2D) materials onto microelectromechanical systems (MEMS) devices. In this study, we show successful dry transfer with a gel material of a stable, clean, and free-standing exfoliated graphene film onto a push-to-pull (PTP) device, which is a MEMS device used for uniaxial tensile testing in in situ transmission electron microscopy (TEM). Through the results of optical microscopy, Raman spectroscopy, and TEM, we demonstrate high quality exfoliated graphene on the PTP device. Finally, the stress-strain results corresponding to propagating cracks in folded graphene were simultaneously obtained during the tensile tests in TEM. The zigzag and armchair edges of graphene confirmed that the fracture occurred in association with the hexagonal lattice structure of graphene while the tensile testing. In the wake of the results, we envision the dedicated preparation and in situ TEM tensile experiments advance the understanding of the relationship between the mechanical properties and structural characteristics of 2D materials.