• Bulletin of the Korean Chemical Society
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• v.13 no.5
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• pp.511-516
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• 1992

The catalytic oxidation of CO on perovskite $Eu_{1-x}Sr_xCoO_{3-y}$, has been investigated at reaction temperatures from 100 to $250^{\circ}C$ under stoichiometric CO and $O_2$ partial pressures. The microstructure and Sr-substitution site of the catalyst were studied by means of infrared spectroscopy. The reaction rates were found to be correlated with 1.5-and 1.0-order kinetics with and without a $CO_2$ trap, respectively; first-and 0.5-order with respect to CO and 0.5-order to $O_2$ with the activation energy of 0.37 eV $mol^{-1}$. It was found from IR, ${\sigma}$ and kinetic data that $O_2$ adsorbs as an ionic species on the oxygen vacancies, while CO adsorbs on the lattice oxygens. The oxidation reaction mechanism is suggested from the agreement between IR, ${\sigma}$ and kinetic data.

• Resources Recycling
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• v.31 no.5
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• pp.20-25
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• 2022

In this study, the applicability of microalgae was evaluated for eco-friendly decontamination of cesium-137 (Cs-137) and strontium-90 (Sr-90), which are radioactive nuclides contained in radioactive waste. The monolithic radioactive solution used in the experiment was manufactured at a concentration of 1.5 Bq/mL Cs-137 and 1.0 Bq/mL Sr-90 by diluting a standard radioactive solution and distilled water. This experiment used two types of microalgae, Chlorella Vulgaris was used for Sr-90 decontamination and Hematococcus pluvialis for Cs-137 decontamination. The experimental method is to put the microalgae cultured for 2 weeks into a bottle with a semi-permeable membrane, and then put the bottle in which the microalgae was put into the manufactured radioactive solution, so that the microalgae and the radioactive solution react through the semi-permeable membrane for 48 hours. For the radioactivity concentration analysis of each sample, a gamma-ray nuclide analyzer was used for Cs-137, a γ-ray isotope, and a Liquid Scintillation Count(LSC) was used f or Sr-90, a β-ray isotope. As a result of the experiment, it was confirmed that about 88.0 % of Cs-137 and about 89.7 % of Sr-90 could be decontaminated, and about 98.6 % of Sr-90 was finally able to be decontaminated by the two-stage decontamination method.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.25-28
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• 2022

We investigated the formation of superconducting intergrowth phases through the interface reaction both between TlSr₂Cu₁O₅ (Tl-121) and (CrO₄)Sr₂CuO₂, and between Tl -121 and ((CO₃)_0.5(CrO₄)_0.5 Sr₂CuO₂ phases. We found oxychromate intergrowth phases can be formed through the interface reactions and a new superconducting oxychromate compound TlSr₄Cu₂O_z(CO₃)_0.5(CrO₄)_0.5 with T_c above 73 K was discovered based on the results of the interface reactions.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.232-237
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• 2008

As the single chamber SOFC(SC-SOFC) showed higher prospect on reducing the operation temperature as well as offering higher design flexibility of SOFCs, lots of concerns have been given to investigate the catalytic activity of perovskite-type oxide in mixed fuel and oxidant conditions. Hence we thoroughly investigated the catalytic property of various perovskite-type oxides such as $La_{0.8}Sr_{0.2}MnO_3(LSM),\;La_{0.6}Sr_{0.4}CoO_3(LSC),\;La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3(LSCF),\;Sm_{0.5}Sr_{0.5}CoO_3(SSC),\;and\;Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}(BSCF)$ under the partial oxidation condition of methane which used to be given for SC-SOFC operation. In this study, powder form of each perovskite oxides whose surface areas were controlled to be equal, were investigated as functions of methane to oxygen ratios and reactor temperature. XRD, BET and SEM were employed to characterize the crystalline phase, surface area and microstructure of prepared powders before and after the catalytic oxidation. According to the gas phase analysis with flow-through type reactor and gas chromatography system, LSC, SSC, and LSCF showed higher catalytic activity at fairly lower temperature around $400^{\circ}C{\sim}450^{\circ}C$ whereas LSM and BSCF could be activated at much higher temperature above $600^{\circ}C$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.415-420
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• 2020

Strontium is known as a salt-soluble element during the electrolytic oxide reduction (EOR) process. The chemical behavior of SrO during EOR was investigated via thermodynamic calculations to provide quantitative data on the chemical status of Sr. To achieve this, thermodynamic calculations were conducted using HSC chemistry software for various EOR conditions. It was revealed that SrO reacts with LiCl salt to produce SrCl₂, even in the presence of Li₂O, and that the ratio of SrCl₂ depends on the initial concentration of Li₂O dissolved in LiCl. It was found that SrO reacts with Li to produce Sr during EOR and that the reduced Sr reacts with LiCl salt to produce SrCl₂. As a result, the proportions of metallic forms were lower in Sr than in La and Nd under various EOR conditions. The thermodynamic calculations indicated that the three chemical forms of SrO, SrCl₂, and Sr co-exist in the EOR system under an equilibrium with Li, Li₂O, and LiCl.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.1
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• pp.25-33
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• 1998

We have studied the reduction of NO by propane over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution by substitution of metal into A or B site of perovskite oxides. In addition, the reaction conditions, such as temperature, $O_2$ concentration, space velocity have been studed. In the $LaCoO_3$ type catalyst, the partial substitution of Ba, Sr into A site enhanced the catalytic activity in the reduction of NO. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3(x=0 \sim 1.9)$ catalyst, the partial substitution of Fe into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. The surface area and catalytic activity of perovskite catalysts prepared by malic acid method showed higher values than those of solid reaction method. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$ catalyst, the conversion of NO increased with increasing $O_2$ concentration and contact time. The introduction of water into reactant feed decreased the catalytic activity.

• Journal of the Korean Ceramic Society
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• v.44 no.4 s.299
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• pp.214-218
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• 2007

The decrease of polarization resistance in cathode is the key point for operating at intermediate temperature SOFC (solid oxide fuel cell). In this study, the influence of Co substitution in B-site at complex perovskite on the electronic conductivity of PSCM ($Pr_{0.3}Sr_{0.7}Co_xMn_{(1-x)}$) was investigated. The PSCM series exhibits excellent MIEC (mixed ionic electronic conductor) properties. The ASR (area specific resistance) of PSCM3773 was $0.174{\Omega}{\cdot}cm^2\;at\;700^{\circ}C$. The activation energy of PSCM3773 was also lower than other compositions of PSCM. The TEC(thermal expansion coefficient) was decreased by addition of Mn. The ASR values were increased gradually during the thermal cycling test of PSCM37773 due to the delamination between electrolyte and cathode materials. The delamination was caused by the difference of TEC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.330-337
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• 2005

La/sub 0.8/Sr/sub 0.2/Ga/sub 0.8/Mg/sub 0.2/O/sub 3-δ/-based solid electrolytes in which Mg site was partially substituted by Fe, Co or Ni (0.05, 0.1, 0.15 at.％) were fabricated by conventional solid-state reaction and their sintered densities were above 94％ of theoretical density. X-ray diffraction analysis and microstructure observation for the sintered specimens were performed. The ac complex impedance were measured at 400。C to l000。C in air and fitted with a Solatron ZView program. The electrical conductivity of La/sub 0.8/Sr/sub 0.2/Ga/sub 0.8/Mg/sub 0.2/O/sub 3-δ/-based solid electrolytes substituted by Fe, Co or Ni was higher than that of pure La/sub 0.8/Sr/sub 0.2/Ga/sub 0.8/Mg/sub 0.2/O/sub 3-δ/. The electrical conductivity of La/sub 0.8/Sr/sub 0.2/Ga/sub 0.8/Mg/sub 0.05/Ni/sub 0.15/O/sub 3-δ/ electrolyte was 3.4×10/sup -2/ Scm/sup -1/ at 800。C and the highest value of the whole electrolytes.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.297-302
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• 2018

Bead type and hollow fiber type catalyst (HFC, Hollow Fiber type Catalyst) was prepared by $La_{0.1}Sr_{0.9}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF1928) perovskite powder catalyst which showed excellent methane complete oxidation characteristics through previous studies. The HFC have a cylindrical shape with an empty interior, and pores can be formed through Phase inversion method so the specific surface area can be remarkably improved. In the case of the bead type catalyst prepared by adding Methyl Cellulose (MC), $SrCO_3$ was produced in addition to the original catalyst composition of LSCF1928 due to the reaction of $CO_2$ emitted from MC and Sr of the catalyst. In the case of the HFC, a single phase perovskite structure was obtained without impurities. The HFC calcined at $700{\sim}900^{\circ}C$ showed pore structure of finger-sponge-finger structure, and 99.9% oxygen conversion rate was achieved through complete oxidation of methane at $475^{\circ}C$. Air gap and spinning pressure condition were changed to control the HFC pore. 2 cm air gap and 7 bar spinning pressure showed the best catalytic performance and achieved oxygen conversion rates of more than 70.65%, 93.01%, and 99.99% at $425^{\circ}C$, $450^{\circ}C$ and $475^{\circ}C$, respectively.

• Korean Journal of Materials Research
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• v.8 no.8
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• pp.737-743
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• 1998

The synthesis of $SrAI_2O_4:Eu^{2+}$ phosphor and its properties of both photoluminescence and long-phosphorescent were investigated as a function of sintering condition. Single phase of $SrAl_2O_4$ was obtained by sintering the mixtures of $SrCO_3$, $Eu_2O_3$, $AI_2O_34 and 3wt% $B_2O_3$ powders over 100$0^{\circ}C$ in Ar/H2 atmosphere. The optimum sintering condition for the long-phosphorescent phosphor of $SrAI_2O_4:Eu^{2+}$ was found at 130$0^{\circ}C$ for 3hours. The PL emission spectrum of $SrAI_2O_4:Eu^{2+}$ shows a maximum peak intensity at 520nm(2.384eV) with a broad emission extending from 450 to 650nm which resulted from the $4f^65d^1$$\rightarrow$$4f^7$ transition of $Eu^{+2}$ under 360nm exitation. Monitored at 520nm. the excita¬tion spectrum of $SrAI_2O_4:Eu^{2+}$ exhibits a maximum peak intensity at 360nm (3.44eV) with a broad absorption band extending from 250 to 480nm.