• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.6
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• pp.884-891
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• 2005

This paper describes the purification and properties of a multicatalytic proteinase complex, proteasome, from bovine skeletal muscle, in comparision with proteasome prepared from other species or organs. The purified bovine skeletal muscle proteasome exhibited a single band on polyacrylamide gel electrophoresis under nondenaturing conditions. Bovine skeletal muscle proteasome degraded synthetic peptides maximally at pH 8.0. Relative to pH 8.0, activities were gradually decreased with the lowering pH, but the extent of decrease was substrate-dependent, and the activity at pH 5.5 still retained 78-10% of the activity at pH 8.0, indicating the possibility that the proteasome is active in muscle during aging. When the proteasome was heated at 60$^{\circ}C$ for 15 or 30 min and treated in the presence of 0.0125% SDS, the activity increased over 1.8 and 3.1 times (LLVY (Suc-Leu-Leu-Val-Tyr-NH-Mec) as a substrate), respectively. These results (activation with heat or SDS) indicate that the hydrolytic activity of proteasome was stimulated under mild denaturing conditions. The characteristics of the bovine skeletal muscle proteasome obtained in our experiment were almost the same as those of the proteasome prepared from other species or organs.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.4
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• pp.58-65
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• 2000

Use of a pectinase during preparing handmade papers from bast fiber of paper mulberry(Broussonetia kazinoki Sieb.) was investigated in order to decrease cooking chemicals and environmental pollution. For this purpose, four kinds of commercial pectinases, Rapidase LIQ(RLP), Rapidase Press(RP), Rapidase C80L Max(RCM) and Pectinase SS Kyowa(PSK) were used. And the durability of handmade papers before and after pectinase treatment was determined. RP and PSK had higher pectinase activity ad lower cellulase activity. The bast fiber was not defibered when pectinase was used. In order to increase the efficiency of enzymes, the bast fiber were treated ammonium oxalate(AO) or $K_2CO_3$under mild conditions. The AO pretreatment with those produced by $K_2CO_3$. The RP treated pulps after mild $K_2CO_3$cooking of the bast fiber were defibrated more easily than untreated pulp. The handmade paper prepared with the RP treated pulps after mild $K_2CO_3$cooking has good strength properties such as breaking length and folding endurance. Also, it has higher durability on heat aging, though its brightness was slightly lower than that of untreated paper.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.5
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• pp.249-256
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• 2006

Structural studies have been performed on precipitation hardening found in $L1_2$ ordered ${\gamma}^{\prime}-Ni_3(Al,Ti)$ alloys using transmission electron microscopy. A uniform solid solution of ${\gamma}^{\prime}-L1_2$ ordered phase supersaturated with Ni can be obtained by solution annealing in a suitable temperature range. The ${\gamma}^{\prime}$ phase hardens appreciably by the fine precipitation of disordered ${\gamma}$. The shape of ${\gamma}$ precipitates formed during aging is initially spherical or round-cubic and grow into platelets as aging proceeds. High resolution electron microscopy revealed that the ${\gamma}$ precipitates are perfectly coherent with the matrix ${\gamma}^{\prime}$ as long as the ${\gamma}$-precipitates are plates. The loss of coherency initiates by the introduction of dislocations at the ${\gamma}/{\gamma}^{\prime}$ interface followed by the step formation at the dislocations. The ${\gamma}$ precipitates become globular after the loss of coherency. The strength of ${\gamma}^{\prime}-Ni_3(Al,Ti)$ increases over the temperature range of experiment by the precipitation of fine ${\gamma}$ particles. The peak temperature where a maximum strength was obtained shifted to higher temperature.

• Corrosion Science and Technology
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• v.2 no.2
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• pp.75-81
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• 2003

Chromium, molybdenum. and nitrogen are very important alloying elements in stainless steels and its effect was approved in pitting resistance equivalent (PRE) equations and many experimental results. However, Cr can improve the corrosion resistance, but facilitate the formation of sigma phase. Also. Mo has the same effect in stainless steels. If Cr and Mo are added at high amount to increase the corrosion resistance of stainless steel, corrosion resistance in annealed alloys can be improved, but in case of welding or aging heat treatment. its resistance will be drastically decreased. In this work, increasing Cr and N contents but decreasing Mo than the commercial alloys made the experimental alloys. Typical alloys are 25Cr-4.5Mo-0.43N alloy, 27Cr-4.7Mo-0.4N alloy, 27Cr-5.3Mo-0.25N alloy, 32Cr-2.6Mo-0.36N alloy. After annealing and aging heat treatment, microstructures, anodic polarization test, and pitting corrosion test were performed. Annealed alloys showed $100^{\circ}C$ of CPT and aged alloys showed the different tendency depending upon Cr and Mo contents(SFI)

• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.177-184
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• 2022

The present study aims to investigate the influence of Zn addition on hardness and microstructural characteristics of discontinuous precipitates (DPs) formed by isothermal aging in Mg-9%Al and Mg-9%Al-1%Zn alloys. To obtain large DPs volume fractions in the microstructure, the alloy specimens were solution-treated at 688 K for 24 h followed by water quenching, and then aged at 413 K for 48 h. The aged Mg-9%Al-1%Zn alloy had higher DPs content than the Mg-9%Al alloy, indicating that the Zn addition plays a beneficial role in enhancing age-hardening response. The DPs in the Zn-containing alloy possessed the higher hardness than those of the Zn-free alloy. Microstructural examination revealed that the increased hardness of the DPs resulting from the Zn addition is closely associated with the lower α-(Mg)/β(Mg₁₇Al₁₂) interlamellar spacing and the higher volume fraction of β phase layer of the DPs.

• Food Science and Preservation
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• v.23 no.3
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• pp.301-309
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• 2016

The objective of this study was to investigate physicochemical and antioxidant characteristics of immature flat persimmon during 7 heat treatment aging steps. The pH decreased, and hence, acidity increased with aging. Hunter L value decreased with aging. The a value rapidly increased until step 3, whereas the b value decreased. Fructose content decreased while glucose contents slightly increased during aging. Hardness, chewiness and gumminess rapidly decreased, indicating softening in texture, but it was negligible after aging step 3. Phenolic compounds including gallic acid and homogentisic acid were detected at step 3 and then gradually increased with aging. However, contents of flavonoid and tannin were much higher in step 1 sample than others. The antioxidant activities observed by DPPH, ABTS, and FRAP assay were the highest at step 1 possibly due to the higher levels of flavonoids and tannin acid in the step 1 sample.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.34-43
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• 1991

A small amount of misch metal and/or Zr was added as a dopant to 70.5wt----Cu-26wt----Zn-3.5wt----Al shape memory alloy in order to study the effect of grain refinement and heat treatments on the transformation behavior, stabilization of martensite, and shape memory ability. It was found that the addition of misch metal and Zr was very effective for reducing the grain size. The fracture mode has been changed from intergranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal and Zr. Aging of the ${\beta}$-phase decreases the $M_s$ temperature, but that of the martensite phase increases the $A_s$ temperature. The hysteresis of transformation temperature ${\Delta}T(A_s-M_s)$ has an increasing tendancy by grain refinement. The crystal structure of martensite was identified as monoclinic structure. As the grain size decreased, martensite stabilization more easily occured and the shape, memory ability has been reduced by the grain size refined.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.83-83
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• 2000

Alkylketene dimer was known as a cellulose reactive or alkaline size because it does not require to fix to the fiber as do the traditional rosin sizes. A proposed sizing mechanism of AKD was the formation of P -ketoester bond between AKD and cellulose which provides the permanent attachment and the orientation of the hydrophobic alkylchains outward. However, some questions about the reaction had arisen and thus, the sizing mechanism of AKD has been a subject of controversy for several decades. The major concern of the controversy is that AKD is really reactive with cellulose or not in the papermaking conditions. In this study, reaction between AKD and pulp fiber was investigated, in order to find out whether AKD forms P-ketoester with pulp fiber during aging under no catalyzed neutral condition with obvious spectroscopic evidence. In addition, effect of aging treatment on the sizing development was studied. It has been disclosed that, in absence of water, AKD reacted with cellulose to form P -ketoester linkage under no catalyzed neutral condition, while, in presence of water, most of AKD was hydrolyzed to a dialkyl ketone or P -ketoacid. In addition, during the aging treatment of AKD-sized paper, its typical IR spectra bands gradually were reduced, completely disappeared after 6hr aging, and formed new absorption bands at 1707cm-' and shoulder peak at 1700cm-' which refer to the typical dialkylketone absorption bands. Therefore, the formation of P -ketoester between AKD and pulp fiber is impossible in the practical papermaking process. It could be suggested that the sizing development of AKD-sized paper is obtained by next two mechanism: 1) formation of a thin-layer of AKD on the fiber surface through melting and spreading of AKD emulsion particles by heat and 2) the hydrolysis of AKD to dialkyl ketone which has higher melting point, during drying and storage of AKD sized papers.

• Journal of Korea Foundry Society
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• v.14 no.3
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• pp.233-239
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• 1994

The effects of solid solution treatment and aging in the properties of Cu-0.32wt%Be-1.35wt%Co alloy was gravity die casted and forged were investigated in order to examine the optimum heat treatment conditions for production of high conductivity mold material. The optimum properties for mold material were obtained under the conditions which were solid solution treated at $930^{\circ}C$ for 1 hour and aged at $430^{\circ}C$ for 2hours.