• Korean Journal of Materials Research
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• v.23 no.10
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• pp.543-549
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• 2013

The purpose of this paper was to investigate the effect of a high-energy milling (HEM) process on the particle morphology and the correlation between a thermal treatment and tetragonal/monoclinic nanostructured zirconia powders obtained by a precipitation process. To eliminate chloride residue ions from hydrous zirconia, a modified washing method was used. It was found that the used washing method was effective in removing the chloride from the precipitated gel. In order to investigate the effect of a pre-milling process on the particle morphology of the precipitate, dried $Zr(OH)_4$ was milled using a HEM machine with distilled water. The particle size of the $Zr(OH)_4$ powder exposed to HEM reduced to 100~150 nm, whereas that of fresh $Zr(OH)_4$ powder without a pre-milling process had a large and irregular size of 100 nm~1.5 ${\mu}m$. Additionally, modified heat treatment process was proposed to achieve nano-sized zirconia having a pure monoclinic phase. It was evident that two-step calcining process was effective in perfectly eliminating the tetragonal phase, having a small average particle of ~100 nm with good uniformity compared to the sample calcined by a single-step process, showing a large average particle size of ~300 nm with an irregular particle shape and a broad particle size distribution. The modified method is considered to be a promising process for nano-sized zirconia having a fully monoclinic phase.

• Journal of Surface Science and Engineering
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• v.55 no.6
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• pp.448-459
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• 2022

Generally, steel is the most commonly used in the industry because of good strength, processability and cost-effectiveness. Steel can be surface-treated such as coating or used as an alloy by adding elements such as Cr, Ni, Zr, and Al to increase corrosion resistance. However, even if steel is used in same environment corrosion resistance is sharply lowered when it is exposed to a high temperature for a fixed or extended period of time due to an overload or other factors. In particular, the use of hot-dip aluminized plated steel, which is used in high-temperature atmospheres, is increasing due to the surface Al₂O₃ oxide film. This steel necessitates an urgent solution as issues of corrosion resistance limitations often appear. It is an important issue that not only cause analysis but also the research for the surface treatment method that can be solved. Thus, in this study, Cr in which it is expected to be effective in corrosion resistance and heat resistance attempted to deposit on hot dip aluminized plated steel with PVD sputtering. And it was possible to present the surface treatment application of various types of industrial equipment exposed to high temperature and basic design guidelines for use by confirming the corrosion resistance of hot dip Al-Si plated steel with Cr film deposited at high temperature.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.6
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• pp.559-564
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• 1991

Three different fermentation methods of dongchimi, a Korean radish roots pickle, were compared with conventional method of brining in 7% NaCl solution at $25^{\circ}C$ in order to improve the storage stability. The methods studied were addition of KCI and $CaCl_2 into the hot ($90^{\circ}C$) salt solutin (method A), addition of salts mixture of phosphates (method B) and salts mixture of phosphates, nitrite and citrate (method C) into half fermented dongchimi solution (pH 4.5~4.7) prepared by the method A. It was found from results that the method B and C reduced the decreasing rate of pH very significantly by more than 2~2.5 folds, while total a measured higher values for the method B and C. Changes in hardness of dongchimi showed little diffeence to control. The concentration of reducing sugar in the first day dongchimi solution prepared by hot brining method was measured much higher than those of control which was followed by rapid decrease. Organoleptic comparion showed a clear effect of salts mixtures by receiving the significantly higher scores in fresh dongchimi flavor and lower values in yeast moldy and sour flavor for the method B and C when those were compared to control.

• Resources Recycling
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• v.28 no.6
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• pp.79-86
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• 2019

Recently, the use of lithium ion battery(LIB) has increased. As a result, the price of lithium and the amount spent lithium on ion battery has increased. For this reason, research on recycling lithium in waste LIBs has been conducted1). In this study, the effect of roasting for the selective lithium leaching from the spent LIBs is studied. Chemical transformation is required for selective lithium leaching in NCM LiNi_xCo_yMn_zO₂) of the spent LIBs. The carbon in the waste EV cell powder reacts with the oxygen of the oxide at high temperature. After roasting at 550 ~ 850 ℃ in the Air/N₂ atmosphere, the chemical transformation is analysed by XRD. The heat treated powders are leached at a ratio of 1:10 in D.I water for ICP analysis. As a result of XRD analysis, Li₂CO₃ peak is observed at 700 ℃. After the heat treatment at 850 ℃, a peak of Li₂O was confirmed because Li₂CO₃ is decomposed into Li₂O and CO₂ over 723 ℃. The produced Li₂O reacted with Al at high temperature to form LiAlO₂, which does not leach in D.I water, leading to a decrease in lithium leaching ratio. As a result of lithium leaching in water after heat treatment, lithium leaching ratio was the highest after heat treatment at 700 ℃. After the solid-liquid separation, over 45 % of lithium leaching was confirmed by ICP analysis. After evaporation of the leached solution, peak of Li₂CO₃ was detected by XRD.

• Korean Journal of Food Science and Technology
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• v.5 no.4
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• pp.201-205
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• 1973

In order to eliminate aflatoxin in foodstuffs, the effects of the treatment by various pH conditions, acid and alkali, and salt on each temperature and time were studied in this experiment and the results were as follows: 1) In the low pH, aflatoxins were much more destroyed than high pH. The destruction of aflatoxins was significantly increased by heat in the same pH levels. 2) BY the treatment of 1.5 and 10% of sodium hydroxide and ammonia, aflatoxins were completely eliminated, but $40{\sim}80%$ of aflatoxins were eliminated by the treatment of 1.5 and 10% of acetic acid, hydrochloric acid and sulfuric acid. 3) By the treatment of aflatoxin in bile acid and artificial gastric juice, aflatoxins were completly eliminated and 75% respectively. 4) By the boiling $(100^{\circ}C)$ for 30 minutes in salt solution, $39{\sim}55%$ of aflatoxins was eliminated and no variation was observed as the concentration.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.16-20
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• 2016

In this work, we describe the synthesis and infrared light reflecting characteristics of $TiO_2$/mica hybrid composites. $TiO_2$/mica composite materials were obtained by the hydrolysis and condensation reaction of titanium isopropoxide in an aqueous solution of acetic acid in the presence of mica particles. Amorphous phase of $TiO_2$ on the surface of mica was converted to the crystalline rutile phase via anatase phase by heat treatment ($600-1000^{\circ}C$, 1-3 h) of $TiO_2$/mica composite materials, and the size of crystals was controlled by heat treatment conditions. Physicochemical properties of mica and $TiO_2$/mica composites were investigated using FE-SEM, ED-XRF, and PXRD. The solar reflectance of $TiO_2$/mica composites in the near IR region (780~2,500 nm) measured using a diffuse reflectance NIR spectrophotometer was 88.6%, which is rather higher than that of calcined pure mica (86.6%). Therefore, $TiO_2$/mica composites can be used as NIR light reflective pigments.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.1
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• pp.10-19
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• 2006

Microstructure and morphology of precipitates in $Ni_3Al$- and TiAl-based intermetallics containing carbon have been investigated in terms of transmission electron microscopy(TEM). In an $L1_2$-ordered $Ni_3Al$ alloy with 4 mol.% of chromium and 0.2~3.0 mol.% of carbon, fine octahedral precipitates of $M_{23}C_6$ type carbide were formed in the matrix by aging at temperatures around 973 K after solution annealing at 1423 K. TEM examination revealed that the $M_{23}C_6$ phase and the matrix lattices have a cube-cube orientation relationship and keep partial atomic matching at the {111} interface. After prolonged aging or by aging at higher temperatures, the $M_{23}C_6$ precipitates then adopt a rod-like morphology elongated parallel to the <100> directions. In the $L1_0$-ordered TiAl containing 0.1~2.0 mol.% carbon, TEM observations revealed that needle-like precipitates, which lie only in one direction parallel to the [001] axis of the $L1_0$ matrix, appear in the matrix and preferentially at dislocations. Selected area electron diffraction(SAED) patterns analyses have shown that the needle-shaped precipitate is $Ti_3AlC$ of perovskite type. The orientation relationship between the $Ti_3AlC$ and the $L1_0$ matrix is found to be $(001)_{Ti3AlC}//(001)_{L10\;matrix}$ and $[010]_{Ti3AlC}//[010]_{L10\;matrix}$. By aging at higher temperatures or for longer period at 1073 K, plate-like precipitates of $Ti_2AlC$ with a hexagonal structure are formed on the {111} planes of the $L1_0$ matrix. The orientation relationship between the $Ti_2AlC$ and the $L1_0$ matrix is $(0001)_{Ti2AlC}//(111)_{L10\;matrix}$ and $_{Ti2AlC}//_{L10\;matrix}$.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.170-175
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• 2004

The ferroelectric (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ thin films were fabricated by sol-gel method using Y-acetate, Yb-acetate, and Mn-acetate as raw materials. The stable (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ precursor solution (sol) was prepared through the reflux process with acetylaceton as a catalyst and coated on Si(100) substrate by spin coating. The heat treatment temperature and, Rw ($H_2O$/alkoxide moi ratio) dependence on crystallinity of thin films were studied. The lowest temperature for obtaining YbMn $O_3$phase and the optimum heat-treatment conditions were proved as at 7$50^{\circ}C$ and 80$0^{\circ}C$, respectively. The hexagonal YbMn $O_3$with c-axis preferred orientation could be obtained at Rw=1 condition. The remanent polarization for the thin films of x=0 or 1 was about 200 nC/㎤ while, for the specimens ot 0< x< 1, were 50∼100 nC/$\textrm{cm}^2$.

• The Korean Journal of Food And Nutrition
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• v.15 no.2
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• pp.104-111
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• 2002

The peptidyl prolyl sis-trans isomerase (PPIase, EC 5.2.1.8) from bacillus stearothermophilus was extracted from the cells treated with by lysozyme. PPIase was purified from the cell extracts by heat treatment, ammonium sulfate precipitation, ion exchange chromatography and finally gel filtration, sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE). The molecular weight of the purified PPIase was estimated as 18kDa by SDS-PAGE. The 39 amino acid residues from the N-terminus were determined by the protein sequencer. The enzyme showed the optimum pH at 8.0 and was stable at the range of pH 7.0∼8.0. The enzyme was considerably stable after heat treatment at 60$\^{C}$ for 30minutes, and the enzyme was quite stable up to 65$\^{C}$. The presence of the PPIase in the refolding solution accelerated the isomerization rate of the assay peptide. PPIase gene of Bacillus stearothermophilus was screened from a genomic library by plaque hybridization using the A-l primer as a probe. A PPIase positive plaque contained a 3.0kb insert of the chromosomal DNA. A 3.0kb fragment was subcloned into pUC18, resulting pPI-40. A DNA fragment encoding the N-terminal portion of the PPIase in pPI-40 was amplified by polymerase chain reaction(PCR) method using the A-1 and B-2 primers. The amplified fragment was cloned into the Sma I site of pUC18 and recombinant plasmid was designated as pSN-18. The nucleotide sequence of 167bp fragment was determined. The deduced amino acid sequence of PPIase was completely matched with the determined N-terminal amino acid sequence of PPIase B. stearothermophilus.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.199-209
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• 1994

$PbTiO_3$ thin films were prepared on soda-lime-silica slide glasses, Si-wafer and sapphire substrate by the dip-coating of precursor solution. As starting materials, titanium tetra iso-propoxide and lead acetate trihydrate were used. Then acetylacetone was added to prepare stable sol. The effect of the parameters such as viscosity and composition of sol were investigated. The optical transmittance at visible range, refractive index, IR spectra were measured in varying compositions, thickness and heat treatment temperature. The crystallization of $PbTiO_3$ films were measured by using XRD and SEM. Diffusion of compositions from slide glass to thin film were investigated by using EDX, too. These sols not precipitated for 20 days. Transmittance of $PbTiO_3$ films at visible range were decreased with the increase of thickness and heat treatment temperatures, and were exhibited flat spectra. Pyrochlore type appeared in the films on slide glass and perovskite type appeared in the films on Si-wafer or sapphire at $600^{\circ}C$. Perovskite crystals transformed to $PbTi_3O_7$ phase at $800^{\circ}C$.