• Journal of the Korean Chemical Society
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• v.51 no.3
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• pp.265-269
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• 2007

A comparative study on crystal structures and UV-visible diffuse reflectance spectra for Nb-containing oxyfluorides was performed to probe the relationship between energy band gap and local structure. The oxyfluorides, RbSrNb2O6F, RbCaNb2O6F and RbNb2O5F are commonly composed of the corner-sharing NbO5F octahedra as structural building units. The average Nb-O(F)-Nb bond angles, which can be a measure of the structural distortion, are 158.6° for RbSrNb2O6F, 149.6° for RbCaNb2O6F and 139.5° for RbNb2O5F. As the bond angle decreases, the band gap increases: 3.48eV for RbSrNb2O6F, 3.75eV for RbCaNb2O6F and 4.03 eV for RbNb2O5F. This experimental result implies that the band gap can be controlled with a range of 0.6 eV through a variation of local structure for the Nb-containing oxyfluorides.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.161-161
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• 2012

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.40-49
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• 1994

Potentiometric cell oxygen sensors using $CaF_{2}$ were fabricated for monitering the oxygen partial pressure in the low temperature range ($300^{\circ}C{\sim}$500^{\circ}C). The disk type oxygen sensors consist of a reference electrode: Air($O_{2}:21%$)|Pt, a solid electrolyte $CaF_{2}$, and a sensing metel Pt electrode. And the change in open circuit emf of the disk type cell was about 45mV for the oxygen concentration range, $0.1%{\sim}10%$, at the cell temperature of $400^{\circ}C$. Also, the reference electrode incorporated type sensor showed the change of 40mV for 0.1% to 10% oxygen partial pressure range.

• Journal of the Korean Society of Radiology
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• v.12 no.4
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• pp.451-457
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• 2018

Luminescence properties of $NaCa(PO_3)_3$ doped with $Tb^{3+}$ ions are investigated by optical and laser excitation spectroscopy. The phosphors were prepared by solidstate reaction method The X-ray diffraction(XRD) was used to analyze the crystal structure and the crystallinity of the samples. The excitation and emission spectra and decay curve of $NaCa(PO_3)_3:Tb^{3+}$(0.01 ~ 30mol%) were measured at room temperature. The f - d band of $Tb^{3+}$ is observed in the excitation spectra of $NaCa(PO_3)_3:Tb^{3+}$ in the wave length region 205 ~ 245 nm. Strong emission lines due to the $^5D_4{\rightarrow}^7F_J$ transition and weak emission lines due to the $^5D_4{\rightarrow}^7F_J$ transition are observed in the emission spectra of $NaCa(PO_3)_3:Tb^{3+}$. The energy transfer and cross relaxation between $Tb^{3+}$ ions are discussed in $NaCa(PO_3)_3:Tb^{3+}$ in the emission spectra and life time.

• Molecules and Cells
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• v.44 no.2
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• pp.88-100
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• 2021

Anoctamin 6/TMEM16F (ANO6) is a dual-function protein with Ca2+-activated ion channel and Ca2+-activated phospholipid scramblase activities, requiring a high intracellular Ca2+ concentration (e.g., half-maximal effective Ca2+ concentration [EC50] of [Ca2+]i > 10 μM), and strong and sustained depolarization above 0 mV. Structural comparison with Anoctamin 1/TMEM16A (ANO1), a canonical Ca2+-activated chloride channel exhibiting higher Ca2+ sensitivity (EC50 of 1 μM) than ANO6, suggested that a homologous Ca2+-transferring site in the N-terminal domain (Nt) might be responsible for the differential Ca2+ sensitivity and kinetics of activation between ANO6 and ANO1. To elucidate the role of the putative Ca2+-transferring reservoir in the Nt (Nt-CaRes), we constructed an ANO6-1-6 chimera in which Nt-CaRes was replaced with the corresponding domain of ANO1. ANO6-1-6 showed higher sensitivity to Ca2+ than ANO6. However, neither the speed of activation nor the voltage-dependence differed between ANO6 and ANO6-1-6. Molecular dynamics simulation revealed a reduced Ca2+ interaction with Nt-CaRes in ANO6 than ANO6-1-6. Moreover, mutations on potentially Ca2+-interacting acidic amino acids in ANO6 Nt-CaRes resulted in reduced Ca2+ sensitivity, implying direct interactions of Ca2+ with these residues. Based on these results, we cautiously suggest that the net charge of Nt-CaRes is responsible for the difference in Ca2+ sensitivity between ANO1 and ANO6.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.314-320
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• 2001

In this paper, the properties of an expansive agent (CaO-CaS $O_4$) for dry shrinkage compensation were investigated by a series of experimental program, which might be used at On-Dol heating system as mortar type. The expansion principle of the CaO-CaS $O_4$ was mainly verified. As a result of this study, the correlation between the content of the expansive agent and the compressive strength was obtained in the form of exponential function(Y = A $e^{-x}$), showing that as the content of expansive agent increased as the expansion performance with the compressive strength increased by only a certain amount. Also, as a results of the analysis of a correlation between the expansive performance and the chemical properties which generally accompanied a part of quality management in manufacturing the expensive cement, the expansive performance was relative to only the contents of the F-CaO among chemical properties(Blaine, +44$\mu\textrm{m}$R, F-CaO, S $O_3$,L.O.I). And it was clarified that the results were relative to the second order function, showing that if the contents of the F-CaO increased the expansive performance Increased.d.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.204-210
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• 2000

The control of dissolved aluminum concentration in the hot dip zinc galvanizing bath is greatly important in producing galvannealed steel sheets. The purpose of present study is to provide basic data for measurement of the aluminum concentration in site in hot dip zinc bath at the temperature of $460^{\circ}C\~500^{\circ}C$ using $CaF_2$ solid electrolyte sensor with three kinds of reference electrode. Good workability and stability of the sensor were confirmed with the $Bi+BiF_3$ reference electrode from the emf measurement. In order to measure the aluminum concentration in Zn-Al bath, the galvanic cell of fluorine ion was constructed with $CaF_2$ solid electrolyte as follows; $$(-)W|Zn-Al,\;AlF_3|CaF_2|Bi,BiF_3|W(+)$$. The emf measurement was made at the temperature of $460\pm10^{\circ}C$ in the Zn-Al bath. The following correlationship between aluminum concentration and emf was obtained by the least square regression analysis; $$E/mV=56.795log[\%Al]+1881.7\;R=0.9704$$,$$0.026wt\%{\leq}[\%Al]{\leq}0.984wt\%$$

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.8-15
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• 2024

The CaF₂ single crystal has notable characteristics such as a large band gap (12 eV), excellent transparency over a wide wavelength range, low refractive index and dispersion. Due to these outstanding properties, CaF₂ single crystal has considered as a promising material for short-wavelength light sources in recent lithography processes. However, there is an inherent birefringence of the material at 157 nm and the resulting aberration can be compensated for through the combination of the (100) plane and the (111) plane. Therefore, it is necessary to investigate the characteristics according to the plane. In this study, we analyzed crystallinity, optical properties of commercial CaF₂ single crystal wafers grown by the Czochralski method. In particular, through chemical etching under various conditions, it was confirmed that the shape of etch pits appears differently depending on the plane and the shape and array of specific etch pits affected by dislocations and defects were examined.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.3
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• pp.130-134
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• 2009

A new long persistent phosphors of $CaZrO_3$ was synthesized at high temperature with weak reduction atmosphere by a traditional solid state reaction method. Photoluminescence spectra analysis showed that the $CaZrO_3$ doped with $Tb^{3+}$ emitted green-yellow emission caused by the energy level transition from the $^5D_3$ and $^5D_4$ to $^7F_1{\sim}^7F_6$. The main emission spectra of 542 nm peak by the $^5D_4{\rightarrow}^7F_5$ transition was revealed through synthesizing at high temperature in $N_2$ gas atmosphere. The afterglow emission spectra of $CaZrO_3:Tb^{3+}$ long persistent phosphores arise at 546 nm peak of narrow range. After the 254 nm ultraviolet light excitation source was switched off, the green-yellow long persistent phosphor can be observed which could last for 8 h in the limit of light perception of dark-adapted human eyes ($0.32\;mcd/m^2$).

• Journal of Korean Society of Environmental Engineers
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• v.32 no.5
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• pp.437-442
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• 2010

This work was initiated both to maximize purity of calcium fluoride sludge and to minimize water content in the settled sludge. The sludge was produced in the process of fluoride removal of semiconductor wastewater by the addition of $Ca^{2+}$ ion. Fludized bed reactor(FBR) using calcium fluoride as a seed was adapted. Optimum pH and molar ratio of $Ca^{2+}/F^-$ were determined in lab-scale study. The experimental results showed that fluoride removal was increased as pH and molar ratio of $Ca^{2+}/F^-$ increased, with the best removal of 79.8% in an optimum condition. In the optimum point of fluoride removal, very low ${PO_4}^{3-}$-P removal of 9.3% was observed. It indicates forming $CaF_2$ crystal of high purity, when side reaction of calcium with phosphate was minimized. In addition, water content of settled sludge was 19.3%, which is relatively low compared to other fluoride removal processes. Consequently, the FBR process proposed in this study was very effective in fluoride removal, producing good sludge of high purity and less water content.