• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.154-157
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• 2007

The austenite phase observed in low carbon HSLA steels is well known to be decomposed to various bainitic microstructures, such as granular bainite, acicular ferrite and bainitic ferrite during continuous cooling process. These bainitic microstructures have been usually identified by using either scanning electron microscope (SEM) or transmission electron microscope (TEM). However, SEM and TEM images do no exactly coincide, because of the quite different sample preparation method in SEM and TEM observations. These conventional analysis method is, thus, not suitable for characterization of the complex bainitic microstructure. In this study, focused ion beam (FIB) technique was applied to make site-specific TEM specimens and to identify the 3-dimensional grain morphologies of the bainitic microstructure. The morphological feature and grain boundary characteristics of each bainitic microstructure were exactly identified.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.273-276
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• 2008

In this study, microstructure and distribution of alloy elements were investigated in thermo-mechanically processed C-Mn-Si transformation induced plasticity (TRIP) steels. The microstructures of TRIP steels were investigated by using advanced analysis techniques, such as three dimensional atom probe tomography (3D-APT). At first, the microstructure was observed by using TEM. TEM results revealed that microstructure of C-Mn-Si TRIP steel was composed of ferrite, bainte, and retained austenite. 3D-APT was used to characterize atomic-scale partitioning of added elements at the phase interface. In the retained austenite phase, Ti and B were enriched with C. However, there was no fluctuation of Mn and Si concentration across the interface. Through these analysis techniques, the advanced characteristics of constituent microstructure in C-Mn-Si TRIP steels were identified.

• Applied Microscopy
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• v.24 no.4
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• pp.132-144
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• 1994

The application of TEM in investigating the evolution of microstructure during solid phase crystallization of the amorphous Si, $Si_{1-x}Ge_x,\;and\;Si_{1-x}Ge_x/Si$ films deposited on $SiO_2$ substrate, in identifying the failure mechanism of the TiN barrier layer in the Cu-metallization scheme, and in comparing the microstructure of the as-deposited Cu-Cr and Cu-Ti alloy films are discussed. First, it is identified that the evolution of microstructure in Si and $Si_{1-x}Ge_x$ alloy films strongly depends on the concentration of Ge in the film. Second, the failure mechanism of the TiN diffusion barrier in the Cu-metallization is the migration of the Cu into the Si substrate, which results in the formation of a dislocation along the Si {111} plane and precipitates (presumably $Cu_{3}Si$) around the dislocation. Finally, the microstructure of the as-deposited Cu-Cr and Cu-Ti alloy films is also quite different in these two cases. From these several cases, we demonstrate that the information which we obtained using TEM is critical in understanding the behavior of materials.

• Applied Microscopy
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• v.29 no.3
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• pp.265-274
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• 1999

The microstructure of Cu thin films in various deposition conditions was characterized. Cr films (50 nm thick) and Cu films (500 or 1000 nm thick) were deposited on polyimide films by DC magnetron sputtering. The Ar pressure during Cu deposition was controlled to 5, 50 and 100 mtorr. The microstructure was characterized using conventional and high resolution SEM and TEM. As sputtering pressure increases, open boundaries are observed more frequently. The Cu film deposited at 5 mtorr has a dense and uniform structure, while low-density regions or open boundaries between columns exist in the film deposited at higher pressure. As the film grows thicker, open boundaries are wider and the density of open boundaries are higher. The comparison between SEM and TEM show that the small features shown in high resolution SEM are grains. High resolution SEM is very effective to characterize the microstructure of the thin films. One column in the films deposited at 50 and 100 mtorr consists of several grains, which are smaller than those deposited at 5 mtorr.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.05a
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• pp.14.1-14.1
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• 2007

• Applied Microscopy
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• v.52
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• pp.2.1-2.6
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• 2022

With the lightening of the mobile devices, thinning of electrolytic copper foil, which is mainly used as an anode collection of lithium secondary batteries, is needed. As the copper foil becomes ultrathin, mechanical properties such as deterioration of elongation rate and tear phenomenon are occurring, which is closely related to microstructure. However, there is a problem that it is not easy to prepare and observe specimens in the analysis of the microstructure of ultrathin copper foil. In this study, electron backscatter diffraction (EBSD) specimens were fabricated using only mechanical polishing to analyze the microstructure of 8 ㎛ thick electrolytic copper foil in plane view. In addition, EBSD maps and transmission electron microscopy (TEM) images were compared and analyzed to find the optimal cleanup technique for properly correcting errors in EBSD maps.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.403-409
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• 2015

Metastable phase characteristics of beta Ti alloys were investigated to consider the relationship of the microstructure and diffraction pattern in TEM. TEM analysis showed that the microstructure was mottled as a modulated structure, and the diffraction pattern was composed of spot streaks between the main spots of a stable beta phase with a specific lattice relationship. The modulated structure may be induced by short distance slip or atom movement during a very short interval of solution treated and quenched (STQ) materials. The athermal ${\omega}$ phase, which could be precipitated at low temperature aging, is also analysed by the metastable phase. The metastable phases including athermal ${\omega}$ phase had a common characteristic of hardened and brittle behavior because the dislocation slip was restricted by a super lattice effect due to short distance atom movement at the metastable state.

• Journal of the Korean institute of surface engineering
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• v.32 no.4
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• pp.503-512
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• 1999

The crystal structure and the microstructure of the intermetallic compounds formed in the interface between In solder and Au/Ni/Ti thin films have been investigated by XRD, SEM, and TEM. Indium solder was deposited on the Au/Ni/Ti thin films/Si substrate by evaporation. The heat treatments simulated the flip chip solder joining were performed in RTA system or in furnace. $Auln_2$ phase is formed in all specimens.$ In_{27}$ $Ni_{10}$ and/or $In_{X}$ $Ni_{Y}$ phase are formed in the interface between $Auln_2$ and Ni depending the heat treatment conditions.

• Journal of Powder Materials
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• v.10 no.3
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• pp.195-200
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• 2003

Ni coated $Al_2O_3$ composite was successfully Prepared by the electroless deposition Process. The average size of Ni particles coated on the $Al_2O_3$ matrix powder was about 20 nm. It was hard to find any reaction compound as an impurity at interface between $Al_2O_3$ and Ni particles after sintering. The characterization of microstructure crystal structure and fracture behavior of the sintered body were investigated using XRD, TEM and Victors hardness tester, and compared with those of the sintered $Al_2O_3$ monolithic body. Many dislocations were observed in the Ni phase due to the difference of thermal expansion coefficient between $Al_2O_3$ and Ni phase, and no observed microcracks at their $Al_2O_3$ and Ni interface. In the $Al_2O_3$/Ni composite, the main fracture mode showed a mixed fracture with intergranular and transgranuluar type having some ,surface roughness. The fracture toughness was slightly increased due to the plastic deformation mechanism of Ni phase in the $Al_2O_3$/Ni composite.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.213-216
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• 2009

In this study, three cold-rolled TRIP steels containing different Al content (0.04wt%, 1.0 wt.% and 2.00wt%) were fabricated to understand the complex effects of Al in TRIP steel. The influences of Al on microstructural evolution of cold-rolled TRIP steels have been analyzed by using advanced analysis techniques, such as transmission electron microscope (TEM) and three dimensional atom probe tomography (3D-APT). TEM results revealed that second phases such as bainte and retained austenite decrease with increase of Al content. In addition, 3D-APT was used to characterize atomic-scale distribution of alloying elements at the constituent phases. Through these analysis techniques, the advanced characteristics of constituent microstructure in TRIP steels were identified depending on Al contents in TRIP steels.