• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.542-547
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• 2021

Glass lined impellers are corrosion resistant to most chemicals, including strong acids, and also have a smooth, non-stick surface, easy to clean and free from impurities in the process. Glass lined home base impeller is a multi-purpose impeller designed to stir a wide viscosity range of liquids from low viscosity fluids to high viscosity fluids, among others, cell culture, yeast culture, and beer fermentation pots, especially used for air-water system breathable stirring. The glass lining for HB impellers, which are simple in structure and competitive in performance, is essential to have upper and lower division in order to make the joint area between the impeller and shaft as small as possible. The upper and lower division of the impeller hardly affects the mixing performance, but the aeration performance. In this study, in order to optimize the shape of the Glass Lining HB impeller, a study was conducted on the effect of the angle between the upper and lower impellers, the clearance between the impellers, and the number of baffles on the aeration power. The optimal shape and baffle plate conditions for the Glass lined HB impeller were derived through the study results that the angle and the clearance between the upper and lower impellers decreased the ration of the power consumption with aeration P_g and that without aeration P₀, P_g/P₀.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.19-24
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• 2020

In this work, the electrical property of Si-doped β-Ga2O3 was investigated via a post-growth annealing process. The Ga2O3 samples were annealed under air (O-rich) or N2 (O-deficient) ambient at 800~1,200℃ for 30 mins. There was no correlation between the crystalline quality and the electrical conductivity of the films within the experimental conditions explored in this work. However, it was observed the air ambient led to severe degradation of the film's electrical conductivity while N2-annealed samples exhibited improvement in both the carrier concentration and Hall mobility measured at room temperature. Interestingly, the x-ray photoemission spectroscopy (XPS) revealed that both annealing conditions resulted in higher concentration of oxygen vacancy (VO). Although it was a slight increase for the air-annealed sample, high resistivity of the film strongly suggests that VO cannot be a shallow donor in β-Ga2O3. Therefore, the enhancement of the electrical conductivity of N2-annealed samples must be originated from something other than VO. One possibility is the activation of Si. The XPS analysis of N2-annealed samples showed increasing relative peak area of Si 2p associated with SiOx with increasing annealing temperature from 800 to 1,200℃. However, it was unclear whether or not this SiOx was responsible for the improvement as the electrical conductivity quickly degraded above 1,000℃ even under N2 ambient. Furthermore, XPS suggested the concentration of Si actually increased near the surface as opposed to the shift of the binding energy of Si from its initial chemical state to SiOx state. This study illustrates the electrical changes induced by a post-growth thermal annealing process can be utilized to probe the chemical and electrical states of vacancies and dopants for better understanding of the electrical property of Si-doped β-Ga2O3.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.477-483
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• 2008

$La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ oxide was synthesized by a citrate method and a typical dense membrane of perovskite oxide has been prepared using as-prepared powder by pressing and sintering at $1300^{\circ}C$. Precursor of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ prepared by citrate method was investigated by TGA and XRD. Metal-citrate complex in precursor was decomposed into perovskite oxide in the temperature range of $260{\sim}410^{\circ}C$ but XRD results showed $SrCO_3$ existed as impurity at less than $900^{\circ}C$. Electrical conductivity of membrane increased with increasing temperature but then decreased over $700^{\circ}C$ in air atmosphere ($Po_2=0.2atm$) and $600^{\circ}C$ in He atmosphere ($Po_2=0.01atm$) respectively due to oxygen loss from the crystal lattice. The oxygen permeation flux increased with increasing temperature and maximum oxygen permeation flux of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ membrane with 1.6 mm thickness was about $0.31cm^3/cm^2{\cdot}min$ at $950^{\circ}C$. The activation energy for oxygen permeation was 88.4 kJ/mol in the temperature range of $750{\sim}950^{\circ}C$. Perovskite structure of membrane was not changed after permeation test of 40 h and the membrane was stable without secondary phase change with 0.3 mol Sr addition.

• Korean Journal of Heritage: History & Science
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• v.47 no.4
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• pp.210-223
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• 2014

When sarira reliquary was found in stone pagoda of Mireuksa Temple, there were 494 gold artifacts, including inner gold pot, gold plate with inscription for Sarira enshrinement, etc. Most of gold artifacts were crafted, but there were 22 gold plates and 4 gold ingots, which did not have any specific shape. It was considered that they had not been crafted. Since gold exists as a metal rather than a metallic oxide in nature, in general, it can be crafted by melting and shaping. However, gold in nature has impurities so it has to be refined to have malleability. The characteristic features were identified through the analysis of gold artifacts from sarira reliquary found in stone pagoda of Mireuksa Temple. The analysis result showed that there were 3 types of gold; pure gold artifacts, artifacts produced with silver containing gold and natural gold ingots. Inner gold pot, gold earrings and gold small beads were produced with pure gold and they contained less than 1wt.% of copper. It seemed like they were produced as pure gold to be shaped by hammering. Gold plate with inscription, tweezers, gold earrings, ingots, etc. were produced with silver containing gold as they had to be more solid. Gold ingots seemed to be natural gold considering the distribution of silver and copper in them, but it cannot be concluded as there are not enough information on gold ingots in Korea. The comprehensive research on gold ingots from various regions in Korea has to be carried out to confirm the above. Sarira Reliquary showed the very sophisticated gold craftsmanship. Gold ingots with the inscriptions, which say 1 nyang, were approximately 14g. Considering the weight of these ingots as standard, weights of other ingots were half nyang(7g), 2 nyang(28g), etc.