• Journal of Magnetics
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• 제8권4호
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• pp.129-132
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• 2003

We investigated the crystallographic and magnetic properties of double perovskite $Sr_2Fe_{l-x}Cr_{x}MoO_{6}$ (x=0.0, 0.01, 0.03, 0.05, and 0.10). Mossbauer spectra of the $Sr_2Fe_{l-x}Cr_{x}MoO_{6}$ have been taken at various temperatures ranging from 15 to 415 K. As the temperature increased towards $T_{c}$(415 K), the Mossbauer spectra showed line broadening and 1, 6 and 3, 4 line-width differences because of anisotropic hyperfine field fluctuation. The Mossbauer spectra indicated that an anisotropic field fluctuation of +H ( $P_{+}$=0.85) was greater than that of -H ($P_{-}$=0.15). We also calculated the field fluctuation frequency factors and the temperature dependence of anisotropy energies from its relaxation rate. We interpreted the effect of Cr ($t^3$$_{2g}$) doping as a decrease in the anisotropy energy.

• 한국세라믹학회지
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• 제37권4호
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• pp.320-326
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• 2000

Development of texture in SiC materials by hot-pressing and subsequent annealing was studied. Crystallographic texture type was characterized by measuring X-ray pole figures on the perpendicular plane to the hot-pressing direction. Observed all pole figures were nearly axially symmetric (fiber texture). In case of ${\beta}$-SiC materials, the pole density of basal plane (0004) increased as annealing time increased, in contrast, other planes (hkil) of ${\beta}$-SiC materials and all planes of ${\alpha}$-SiC materials nearly remained unchanged. In the case of ${\beta}$-SiC materials, therefore, a weak texture of (0001) plane at the normal direction took place in the 8h annealed samples, resulting from grian growth. The fracture toughness values of ${\alpha}$-SiC materials measured in both planes parallel and perpendicular to the hot-pressing direction were very similar. However, the fracture toughness of ${\beta}$-SiC materials measured parallel to the hot-pressing direction were higher than that measured perpendicular to the hot-pressing derection, relatively, because of the texture and the microstructure anisotropy.

• 한국재료학회지
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• 제26권4호
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• pp.207-211
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• 2016

Ti films were deposited on glass substrates under various preparation conditions in a chamber of two-facing-target type dc sputtering; after deposition, the electric resistivity values were measured using a conventional four-probe method. Crystallographic orientations and microstructures, including the texture and columnar structure, were also investigated for the Ti films. The morphological features, including the columnar structures and surface roughness, are well explained on the basis of Thornton's zone model. The electric resistivity and the thermal coefficient of the resistivity vary with the sputtering gas pressure. The minimum value of resistivity was around 0.4 Pa for both the $0.5{\mu}m$ and $3.0{\mu}m$ thick films; the apparent tendencies are almost the same for the two films, with a small difference in resistivity because of the different film thicknesses. The films deposited at high gas pressures show higher resistivities. The maximum of TCR is also around 0.4 Pa, which is the same as that obtained from the relationship between the resistivity and the gas pressure. The lattice spacing also decreases with increasing sputtering gas pressure for both the $0.5{\mu}m$ and $3.0{\mu}m$ thick films. Because they are strongly related to the sputtering gas pressures for Ti films that have a crystallographic anisotropy that is different from cubic symmetry, these changes are well explained on the basis of the film microstructures. It is shown that resistivity measurement can serve as a promising monitor for microstructures in sputtered Ti films.

• Geosciences Journal
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• 제22권6호
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• pp.939-953
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• 2018

We examined the microfabrics of omphacite and garnet in foliated eclogite to determine the influence of the layered structure on seismic observations in subduction zone. The analyzed eclogite, from the Lanterman Range, northern Victoria Land, Antarctica, is characterized by layering in which the modal abundances of garnet and omphacite vary. For garnet, the low aspect ratios, similar angular distribution of long axes relative to the foliation in both layers, uniform grain size distribution, near-random crystallographic preferred orientations (CPOs), and misorientation angle distributions are indicative of passive behavior during deformation. In contrast, omphacite shows relatively high aspect ratios, a low angle between the long axes of crystals and the foliation, a wide grain-size distribution, and distinctive CPOs, suggesting dislocation creep as the main deformation mechanism. The results of fabric analyses are consistent with strain localization into omphacite or omphacite-rich layers rather than garnet or garnet-rich layers. The single-crystal seismic anisotropy of garnet is very weak ($AV_P=0.2%$, $AV_S=0.5-0.6%$), whereas that of omphacite is much stronger ($AV_P=3.7-5.9%$ and $AV_S=2.9-3.8%$). Seismic anisotropy of the omphacite-rich layers shows an increase of 329% for $AV_P$ and 146% for $AV_S$ relative to the garnet-rich layers. Our results demonstrate the importance of the layered structure in strain localization and in the development of the seismic anisotropies of subducting oceanic crust.

• Interaction and multiscale mechanics
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• 제4권2호
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• pp.139-153
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• 2011

In this paper we develop a fully anisotropic pressure and temperature dependent model to investigate the effect of the microstructure on the shock response of ${\beta}$-HMX molecular single and polycrystals. This micromechanics-based model can account for crystal orientation as well as crystallographic twinning and slip during deformation and has been calibrated using existing gas gun data. We observe that due to the high degree of anisotropy of these polycrystals, certain orientations are more favorable for plastic deformation - and therefore defect and dislocation generation - than others. Loading along these directions results in highly localized deformation and temperature fields. This observation confirms that most of the temperature rise during high rates of loading is due to plastic deformation or dislocation pile up at microscale and not due to volumetric changes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.429-431
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• 2009

Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND // <111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study, The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND // <111> texture components through asymmetric rolling in Al sheet.

• Journal of Magnetics
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• 제2권3호
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• pp.67-71
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• 1997

A new hot-forming process has been studied to produce anisotropic Nd-Fe-B based magnets from melt-spun ribbons. The ribbon fragments were inserted in a Cu tube and hot-deformed together with one-stroke. At a height reduction ratio of 0.44, the melt-spun ribbons were densified into a magnet with a density of 7.14 g/cm3, and showed a (BH)max of 14.6 MGOe. With further deformation, the magnets were plastically deformed with Cu tubes in the lateral direction, and crystallographic anisotropy was introduced. The magnets with a height reduction ratio of 0.75 exhibited magnetic properties of (BH)max = 32.1 MGOe, Br = 11.7 kG, and iHc = 10.6 kOe. This process shows the possibility that the conventional hot-pressing and subsequent die-upsetting for anisotropic magnets can be simplified into a one-step process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.477-479
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• 2008

Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND//<111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study. The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through asymmetric rolling in Al sheet.

• 한국재료학회지
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• 제18권1호
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• pp.18-21
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• 2008

The wetting behavior of molten Fe on ${\alpha}-Al_2O_3$ single crystals with three different crystallographic orientations, $R(01\bar{1}2),\;A(11\bar{2}0),\;and\;C(0001)$, was investigated using the sessile drop method under a 10%$H_2-Ar$ atmosphere at 1873 K. It was found that the differences in the contact angle of the three differently oriented ${\alpha}-Al_2O_3$ single crystals were not significant (within $5^{\circ}$, which corresponded to the changes in the work of adhesion of $157mJ/m^2$) due to the surface reconstruction.

• 한국자기학회지
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• 제5권5호
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• pp.465-469
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• 1995

We have investigated the effects of deposition angle on structural and magnetic properties of e-beam evaporated ${(4-{\AA}\;Co/9.2-{\AA}\;Pt)}_{23}$ multilayer thin films prepared on tilted substrates. It was found that the [111] crystallographic orientations of the multilayer thin films were not aligned with colummar growth orientations and they were remained to be normal to the substrate planes even though the deposition angle was severely oblique up to $60^{\circ}$. The analysis of the torque curve reveal that the intrinsic anisotropy energy was monotonically decreased with the deposition angle but the easy axis orientation parallel to the substrate normal was not much influenced by deposition angle.