• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1123-1128
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• 1999

To investigate the effect of Sn on the recrystallization of Zr-based alloys. Zr-xSn (x=0.5, 0.8, 1.5, 2.0wt.%) alloys were manufactured to be the sheets through the defined manufacturing procedure. The specimens were annealed at $300^{\circ}C$ to $800^{\circ}C$ for 1 hour. The hardness, microstructure and precipitate of the alloys with the annealing temperature were investigated by using micro- knoop hardness tester, optical microscope(O/M) and transmission electron microscope(TEM), respectively. The cold-worked Zr-xSn alloys showed the typical behavior of the recovery. recrystallization, and grain growth. The recrystallization of Zr-xSn alloys occurred between $500^{\circ}C$ and $700^{\circ}C$. As the Sn content increased. the recrystallization temperature of the cold-worked alloys increased but their grain sizes after recrystallization decreased. It is suggested that the recrystallization of the cold- worked Zr alloys be occurred by the subgrain coalescence and growth mechanism.

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.733-739
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• 2001

In Al-25Nb binary system, it was observed only formation of $D0_{22}$ $Al_3Nb$ intermetallic compound after 5hr milling but it was not observed formation of meta stable phase like L1$_2$ phase. In this state, $D0_{22}$ $Al_3Nb$ fabricated had nano sized grain of approximately 20nm. Ternary systems, transition metals such as Cr, Cu, Fe, Mn were added 6~12at.% as substitution of Al, showed formation of $D0_{22}$ $Al_3Nb$ like Al-25Nb binary system. In Al- l2Cu-25Nb system, it was observed that broad XRD pattern like amorphization of Al and not observed formation of $D0_{22}$ $Al_3Nb$ after 5hr milling. But there was mixed phase of a lot of amorphous Al and little $D0_{22}$ $Al_3Nb$ through TEM. In the states of unalloyed, 5~7hr milling time, those showed exothermic reaction at 35$0^{\circ}C$, which was formation of $D0_{22}$ $Al_3Nb$ like Al-25Nb binary system. With increasing milling time to 10hr, $D0_{22}$ $Al_3Nb$ was transformed to mixed phase of amorphous and nanocryatlline, having approximately 10nm grain but the meta stable $Al_3Nb$ was not fabricated by adding transition metals.

• Korean Journal of Materials Research
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• v.17 no.2
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• pp.100-106
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• 2007

The effects of $MgO-P_2O_5$ based sintering additive on the microstructure and material and biological properties of hydroxyapatite $(HAp,\;Ca_{10}(PO_4)_6(OH)_2)$ ceramic were investigated using XRD, SEM and TEM techniques. The $MgO-P_2O_5$ sintering additive improved the material properties and increased the grain size in the sintered HAp bodies. As the content of sintering additive increased over 4 wt%, a small amount of the HAp phase was decomposed and transformed to ${\beta}-TCP$. In the 2 wt% $MgO-P_2O_5$ content HAp sintered body, the maximum values of density and hardness were respectively about 3.10 gm/cc and 657 HV. However, the maximum fracture toughness in the HAp body containing 8 wt% $MgO-P_{2}O_{5}$ was about $1.02MPa{\cdot}m^{1/2}$ due to the crack deflection effect. Human osteoblast like MG-63 cells and osteoclast like raw 264.7 cells were well grown and fully covered all of the HAp sintered bodies. The osteoblast cells were grown with spindle-shaped and the osteoclast cells had a grape-like round shape.

• Korean Journal of Materials Research
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• v.23 no.10
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• pp.592-598
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• 2013

Graphene oxide powders prepared by two different drying processes, freeze drying and spray drying, were studied to compare the effect of the drying method on the physical properties of graphene oxide powder. The graphene oxide dispersion was prepared from graphite by chemical delamination with the aid of sulfuric acid and permanganic acid, and the dispersion was further washed and re-dispersed in a mixed solvent of water and isopropyl alcohol. A freeze drying method can feasibly minimize damage to the sample, but it requires a long process time. In contrast, spray drying is able to remove a solvent in a relatively short time, though this process requires exposure to a high temperature for a rapid evaporation of the solvent. The powders prepared by freeze drying and spray drying were characterized and compared by Raman spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and by an elemental analysis. The graphene oxide powders showed similar chemical compositions; however, the morphologies of the powders differed in that the graphene oxide prepared by spray drying had a winkled morphology and a higher apparent density compared to the powder prepared by freeze drying. The graphene oxide powders were reduced at $900^{\circ}C$ in an atmosphere of $N_2$. The effect of the drying process on the properties of the reduced graphene oxide was examined by SEM, TEM and Raman spectroscopy.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.44-49
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• 1992

Magnetic properties and microstructures of $Nd_{12}Fe_{80}B_{6}(Nb,\;M)$ (M=Ti/Cu/Ga) melt-spun ribbons prepared by single wheel technique have been studied. The results of microstructural study have shown that Ga is effective for the orientation of c-axis normal to the ribbon plane. The Ga-added melt-spun ribbon, $Nd_{12}Fe_{80}B_{6}(Nb,\;Ga)$, quenched at $V_{s}=17.9\;m/s$ was mostly composed of fine grains of about 30 nm in size with the textured free-side surface. The powder of this ribbon aligned in mag-netic field showd a high remanence of 0.87 T which was about 5 % higher than that of ribbon itself. It is believed that there is a possibility to fabricate a new type of HIREM melt-spun ribbon with highly textured free-side surface.

• Korean Journal of Veterinary Research
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• v.31 no.1
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• pp.89-97
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• 1991

For the ultrastructural observation on Babesia gibsoni(B gibsoni), the protozoa were challenged experimentally to splectomized dog. To examine the ultrastructure of the B gibsoni in the erythrocyte, the infected erythrocytes were collected at the cephalic or jugular vein of the dog. The results obtained by TEM(transmission electron microscopy) were as follows; 1. The sizes of protozoa in erythrocytes are $0.92{\pm}0.36{\mu}m{\times}0.67{\pm}0.21{\mu}m$, the sizes of nucleus of the protozoa are $0.55{\pm}0.24{\mu}m{\times}0.38{\pm}0.26{\mu}m$, and sizes of rhoptries in plasma of the protozoa are $0.33{\pm}0.05{\mu}m{\times}0.25{\pm}0.07{\mu}m$, respectively. 2. The tropozoite membrane in the erythrocyte was one, and it's nuclear membrane was made up of double. But the protozoa of initial stage in infected erythrocyte had double clear mambranes, and distinguished from plasma membrane of red blood cell. 3. The mitochondrialike structures covered with two membranes were observed in the protozoa. 4. Mitochondria and vesicles of the reticulocyte were observed near protozoa in the erythrocyte. 5. There are rhoptry, coiled structure and single nucleous in the merozoite. 6. The shape of rhoptry was round or ovoid form and in occasionally, the content of rhoptry was lost partially. 7. There was able to observe the dividing process of the protozoa. 8. Maurer's cleft-like structure was observed.

• Korean Journal of Veterinary Research
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• v.39 no.6
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• pp.1057-1065
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• 1999

The study was designated to investigate the electron microscopic findings following diethylnitrosamine (DEN) treatment in rats. Forty four male (Srague Dawley) rats were continuously given water containing 0.01% DEN for 13 weeks and livers of five rats with more tumor lesions at 16 and 17 weeks after initial treatment were used as EM materials. In transmission electron microscopic findings, most small-sized hepatocytes were active cells containing large mount of organelles, but light (pale staining) hepatocytes among small-sized hepatocytes were injured cells containg disorganized organelles. Tumor cells among small-sized hepatocytes were irregularly arranged and have pleomorphic nuclei containing electron dense chromatin but the organelles in cytoplasm were swelled. Large-sized hepatocytes were active cells with condensed chromatin but the cytoplasm of these cells were pale due to be injured and dilated organelles. Dark hepatocytes were apoptotic cells with homogenous pyknotic nuclei and cytoplasm, and the cytoplasm of these cells contained dilated smooth endoplasmic reticulum (sER) but these sER were non-vesiculated. Cholangiocarninoma cells were crowded and were pale by far less number of organelles in cytoplasm and nuclei. In scanning electron microscopic findings, the lumens of portal veins, bile canaliculi, bile ductules, bile ducts and sinusoids were dilated and have irregular folded inner surface by protruded parenchyma.

• Journal of Life Science
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• v.14 no.4
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• pp.560-566
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• 2004

Agrocybe aegerita is Hymenomycetes fungus belonging to the order Agaricales and family of Bolbitiaceae. Much less is known about liquid culture of Agrocybe aegerita. Thus, the present study was to investigate the liquid cultural characteristics of Agrocybe aegerita my-celium. The optimal medium for the mycelial growth and density was ME medium, optimal tem-perature and initial pH were 25$\pm$1$^{\circ}C$ and 5.5, respectively. And optimal culture time for mycelial growth was 12 days. The modified optimal medium compositions were dextrin 3% (w/v), yeast extract 2% (w/w), MgSO$_4$0.05% (w/v), and KH$_2$PO$_4$0.15% (w/v). Under optimal culture conditions, the mycelial growth of modified optimal medium was higher than that of ME medium.

• Journal of the Mineralogical Society of Korea
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• v.18 no.3 s.45
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• pp.155-164
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• 2005

Volcanic rocks from the Mt. Mudeung area which are composed of Hwasun andesite, Mudeungsan dacite and Togok rhyolite contain plagioclase phenocrysts in common. Majority of the repeated twins observed in optical microscopy are albite twin and some are pericline twin. EPMA studies of plagioclases from Hwansun andesite, Mudeungsan dacite and Togok rhyolte indicate calcic andesine, andesine-oligoclase, nearly pure albite, respectively Albite twin and pericline twin can be easily distinguished through TEM diffraction patterns, which is quite difficult by optical microscopy. Plagioclases in volcanic rocks from the Mt. Mudeung area do not show e-reflection in (100) electron diffraction patterns, probably because of their high cooling rate, which inhibited phase separations during cooling.

• Journal of the Mineralogical Society of Korea
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• v.1 no.2
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• pp.117-130
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• 1988

The morphology of the Ca-montmorillonites from the Gampo area was investigated by the use of scanning and transmission electron microscope. These bulk samples show an irregular or rugged surface with well developed cavities and relict outline of original ash material at low magnification by SEM, indicating that montmorillonites are derived from volcanogenic material. Two different types of morphology of montmorillonites by SEM were observed which appear to depend very much on the space available for crystal growth. One is honeycomb structure montmorillonite growing in an open space. The other is the closely packed aggregates of intergrown montmorillonite showing platy particles where available space for the growth is limited. Several different habits of montmorillonite within a single sample can be observed by TEM. The dominant habit observed is the irregularly shaped and foliated aggregates and the platy shaped particles. In general, platy shaped particles are relatively abundant in the samples from Yongdongri compared with those from Jugjeonri area.