• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.14-20
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• 2018

Lead zinc niobate (PZN) added lead zirconate titanate (PZT) thick films with thickness of $5{\sim}10{\mu}m$ were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0 %, 20 % and 40 %. The initial particles (PZT, 2PZN-8PZT, 4PZN-6PZT) had irregular shape and submicron sizes. The as-deposited film had fairly dense microstructure without any crack, and showed only a perovskite single phase formed with nano-sized grains. The as-deposited films on silicon were annealed at the temperatures of $700^{\circ}C$, and the films deposited on sapphire were annealed at $900^{\circ}C$ in the electrical furnace. The effects of PZN addition on the microstructural evolution were observed using by FE-SEM and HR-TEM.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.9-14
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• 2006

Sample preparation plays a critical role in microstructure analysis using TEM. Although TEM specimen has been usually prepared by jet-polishing or Ar-ion beam milling technique. these methods could not be applied to YBCO CC which is composed of IBAD or RABiTS substrates, several buffet layers, and YBCO superconducting layer because of big difference in mechanical strengths between the metallic phase and oxide phases. To obtain useful cross-sectional information such as interface between the phases or second phases in YBCO CC, it is prerequisite to secure the large area of thin section in the cross-sectional direction. The superconducting layer or the buffer layers are relatively weak and fragile compared to the metallic substrate such as Ni-5wt%W RABiTS of Hastelloy-based IBAD, and preferential removal of weak ceramic phases during polishing steps makes specimen preparation almost impossible. Tripod polisher and small jig were home-made and employed to sample preparation. The polishing angle was maintained <$1^{\circ}$ throughout the polishing steps using 2 micrometers attached to the tripod plate. TEM specimens with large and thin area could be secured and used for RABiTS/IBAD substrate analyses. In some cases, additional Ar-beam ion milling with low beam current and impinging angle was used for less than 30 sec. to remove debris or polishing media attacked to the specimens.

• Journal of Powder Materials
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• v.10 no.1
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• pp.26-33
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• 2003

Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders rapidly solidified by the gas atomization method were subjected to mechanical milling(MM). The morphology, microstructure and hardness of the powders were investigated as a function of milling time using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Vickers microhardness tester. Microstructural evolution in gas-atomized Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders was studied during mechanical milling. It was noted that the as-solidified particle size of $200\mutextrm{m}$ decreases during the first 48 hours and then increases up to 72 hours of milling due to cold bonding and subsequently there was continuous refinement to $20\mutextrm{m}$ on milling to 200 hours. Two microstructurally different zones, Zone A, which is fine microstructure area and Zone B, which has the structure of the as-solidified powder, were observed. The average thickness of the Zone A layer increased from about 10 to $15\mutextrm{m}$ in the powder milled for 24 hours. Increasing the milling time to 72 hours resulted in the formation of a thicker and more uniform Zone A layer, whose thickness increased to about $30~50\mutextrm{m}$. The TEM micrograph of ball milled powder for 200 hours shows formation of nano-particles, less than 20 nm in size, embedded in an Al matrix.

• Food Science and Preservation
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• v.16 no.6
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• pp.875-883
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• 2009

We investigated the effects of manufacturing method on the quality of beef jerky using electron micrography. Six types of beef jerky were prepared by the addition of sugar (A), licorice (B), one of three kinds of spice extract (clove: C, fennel fruit: D, and Chungyang green pepper extract: E), or a mixture of all spice extracts (F). Microstructural changes in beef jerky during preparation by drying, with respect to drying method and the nature of the added spice extract, were observed by scanning electron micrography (SEM) and transmission electron micrography (TEM). The latter technique showed that the microstructure of fresh meat showed actin and myosin in myofibril lines, and also mitochondria and inner membranes. Beef muscle structure was broken at many myofibril lines and decomposition of inner membrane material was evident after seasoning. SEM of air-blast dried beef jerky with added medicinal herb extracts showed both large spaces and regular myofibrils, whereas hot air-dried beef jerky had no spaces and the muscle myofibrils were still evident. After review of all available micrographs from SEM and TEM, we concluded that use of medicinal herb extracts could be helpful in preserving the muscle myofibril structure during drying, and the air-blast drying method is recommended to optimize the textural quality characteristics of beef jerky.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.696-700
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• 2004

The reduction behavior of $Al_{2}O_3/CuO$ powder mixtures, prepared from $Al_{2}O_3/CuO$ or $Al_{2}O_3/Cu-nitrate$, was investigated by using thermogravimetry and hygrometry. The powder characteristics were examined by BET, XRD and TEM. Also, the influence of powder characteristics on the microstructure and properties of hot-pressed composites was analyzed. The formation mechanism of nano-sized Cu dispersions was explained based on the powder characteristics and reduction kinetics of oxide powders. In addition, the dependence of the microstructure and mechanical properties of hot-pressed composites on powder characteristics is discussed in terms of the initial size and distribution of Cu particles. The practical implication of these results is that an optimum processing condition for the design of homogeneous microstructure and required properties can be established.

• Korean Journal of Materials Research
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• v.2 no.3
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• pp.213-219
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• 1992

The microstructure, dopant distribution and electrical properties of the $As^{+}$ ion-implanted surface layer differ significantly depending on the methods of subsequent heat treatments, furnace annealing(FA) and rapid thermal annealing(RTA). The amorphous layer created by ion implantation was recrystallized during the thermal annealing through solid phase epitaxial (SPE) growth. The dopant distribution and electrical properties are discussed with respect to the TEM cross-sectional microstructure observed. The microstructure, dopant distribution and electrical properties depended upon especially the annealing time of the heat treatment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.322-325
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• 2007

Precipitation characteristics of the Fe-36Ni based high strength Invar alloy for power transmission wire was investigated in this study. High strength can be obtained in this alloy through solution hardening, precipitation hardening and strain hardening by cold working. In the present study, ingots of Fe-36Ni based Invar alloys with the contents of C, Mo and V varied. Microstructure observations by OM, SEM, and TEM were carried out to validate the simulation results. BCC phase and $FeNi_3$ phase are also expected at lower temperatures below $500^{\circ}C$. Aging treatments were carried out at temperatures ranging from 400 to $900^{\circ}C$ for time intervals from 3 min to 100hrs. Peak aging condition was obtained as $400^{\circ}C$ and 1 hr. With temperature increased, peak strength was decreased abruptly. Microstructure observation was conducted by optical microscopy, scanning electron microscopy, and transmission electron microscopy.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.507-511
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• 2017

An optimum route to fabricate oxide dispersion strengthened ferritic superalloy with desired microstructure was investigated. Two methods of high energy ball milling or polymeric additive solution route for developing a uniform dispersion of $Y_2O_3$ particles in Fe-Cr-Al-Ti alloy powders were compared on the basis of the resulting microstructures. Microstructural observation revealed that the crystalline size of Fe decreased with increases in milling time, to values of about 15-20 nm, and that an FeCr alloy phase was formed. SEM and TEM analyses of the alloy powders fabricated by solution route using yttrium nitrate and polyvinyl alcohol showed that the nano-sized Y-oxide particles were well distributed in the Fe based alloy powders. The prepared powders were sintered at 1000 and $1100^{\circ}C$ for 30 min in vacuum. The sintered specimen with heat treatment before spark plasma sintering at $1100^{\circ}C$ showed a more homogeneous microstructure. In the case of sintering at $1100^{\circ}C$, the alloys exhibited densified microstructure and the formation of large reaction phases due to oxidation of Al.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.224-232
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• 2012

In this study, the effect of hot-stamping heat treatment on the microstructure and hardness of TWB(Tailor Welded Blank) laser joints in Al-Si-coated boron steel and Zn-coated DP(Dual Phase)590 steel was investigated. In the TWB joints without heat treatment, hardness profiles showed local hardness deviation near the fusion zone. However, there was no hardness deviation in the heat treated specimen and its hardness was higher than that of the one without the heat treatment, due to a fully martensite microstructure. In the TWB joints of both the boron and DP steels, the maximum hardnesses were observed at the HAZ(Heat Affected Zone) near the base metal, and the hardness decreased gradually to the base metal. In the heat treated joints, the hardnesses of the HAZ and the base metal of the boron steel side were similar to the maximum hardness of the weld, while those of the HAZ and the base metal of the DP steel side were higher than the maximum hardness.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.9-15
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• 2024

Nd-Fe-B permanent magnets have been utilized on various industrial fields such as electric vehicles, generator, robots with actuator, etc, due to their outstanding magnetic properties even 10 times better than conventional magnets. Recently, there are many researches that report magnetic properties improved by controlling microstructure through adjusting alloying elements or conducting various processing. Especially, post-sintering annealing (PSA) can significantly improve the coercivity by modifying the distribution and morphology of Nd-rich phase which formed at grain boundaries. In this study, Nd-Fe-B sintered magnets were subjected to primary heat treatment followed by secondary heat treatment at 460℃, 500℃, and 540℃ to investigate the changes in microstructure and magnetic properties with the secondary heat treatment temperature. EBSD analysis was conducted to compare anisotropic characteristics. Through the SEM and TEM observation for analyzing the morphology and distribution of Nd-rich phase, we investigated the relationship between microstructure and magnetic properties of sintered Nd-Fe-B magnets.