• Journal of the Mineralogical Society of Korea
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• v.13 no.2
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• pp.84-95
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• 2000

Tremolite crystals from the Dongyang talc deposit were studied using high-resolution transmission electron microscopy (HRTEM) to characterize the tremolite-to-talc reaction. [001] HRTEM images of tremolite show intergrowths of wide-chain pyriboles and talc; talc is the primary alteration product of tremolite, and triple-chain structures occur sparsely. The boundaries between tremolite and talc are commonly well defined by (010) and (100) interfaces. (001) talc layers are parallel to (100) of tremolite, and the interfaces between tremolite and talc appear to be coherent in HRTEM images, indicating that most talc laters formed directly from tremolite by a gydration reaction. However, some talc formed along (110) of tremolite, and talc layers are not extended from (010) of tremolite, suggesting that part of talc in the deposit was produced through a dissolution-precipitation mechanism. Carbonate minerals are also associated with tremolite and talc. Common replacement of dolomite by calcite indicates that the tremolite-to-talc reaction results in remnant Ca, which was eventually consumed to replace dolomite to form clacite. Some Mg Produced by dolomite during reaction to calcite was apparently utilized to form talc, because talc formation from tremolite requires extra Mg. Although talc could be formend directly from dolomite, extensive alteration of tremolite to talc suggests that part of talc of the deposit was produced from tremolite that was formed by dolomite reaction during an early stage metamorphism.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.1-18
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• 2006

A novel transmission electron microscopy technique for the visualization of polymers adsorbed on secondary fines has been developed. This technique has been utilized in observing the adsorption behavior of various wet-end additives. The technique is sensitive enough not only to allow differentiation between linear and branched polymers, but also to observe differences in the adsorption behavior and conformational characteristics of particular polymeric derivatives. Conformational changes of a cationic polyacrylamide (CPAM) were examined in response to variations in wet-end conditions, such as mixing time and system conductivity. The molecular conformations of cationic starch and cationic guar gum were also examined by this technique. The technique has been employed to observe the effects of silica microparticles on the conformational characteristics of CPAM (drainage/retention aid) pre-adsorbed on secondary fines. The transmission electron microscopy method is a viable tool for investigating the macromolecular events that make up a large part of wet end chemistry in papermaking.

• Current Research on Agriculture and Life Sciences
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• v.32 no.3
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• pp.125-130
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• 2014

This study used transmission electron microscopy (TEM) to investigate the micro-morphological features of two formaldehyde to urea (F/U) mole ratio liquid urea-formaldehyde (UF) resins with three hardener levels as a function of the curing time. The micro-morphological features of the liquid UF resins were characterized after different curing times. As a result, the TEM examination revealed the presence of globular/nodular structures in both liquid UF resins, while spherical particles were only visible in the low F/U mole ratio resins. The high F/U mole ratio liquid UF resins also showed extensive particle coalescence after adding the hardener, along with the appearance of complex filamentous networks. When the resins were cured with a higher amount of hardener and longer curing time, the spherical particles disappeared. For the low mole UF resins, the particles tended to coalesce with a higher amount of hardener and longer curing time, although discrete spherical particles were still observed in some regions. This is the first report on the distinct features of the crystal structures in low F/U mole ratio UF resins cured with 5% hardener and after 0.5 h of curing time. In conclusion, the present results indicate that the crystal structures of low F/U mole ratio UF resins are formed during the curing process.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2304-2311
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• 2021

The dislocation density in strain-hardened Alloy 690 was analyzed using scanning transmission electron microscopy (STEM) to study the relationship between the local plastic strain and susceptibility to primary water stress corrosion cracking (PWSCC) in nuclear power plants. The test material was cold-rolled at various thickness reduction ratios from 10% to 40% to simulate the strain-hardening condition of plant components. The dislocation densities were measured at grain boundaries (GB) and in grain interiors of strain-hardened specimens from STEM images. The dislocation density in the grain interior monotonically increased as the strain-hardening proceeded, while the dislocation density at the GB increased with strain-hardening up to 20% but slightly decreases upon further deformation to 40%. The decreased dislocation density at the GB was attributed to the formation of deformation twins. After the PWSCC growth test of strain-hardened Alloy 690, the fraction of intergranular (IG) fracture was obtained from fractography. In contrast to the change in the dislocation density with strain-hardening, the fraction of IG fracture increased remarkably when strain-hardened over 20%. From the results, it was suggested that the PWSCC growth behavior of strain-hardened Alloy 690 not only depends on the dislocation density, but also on the microstructural defects at the GB.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.352-355
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• 2007

Polycrystalline materials such as steels(BCC) and aluminum alloys(FCC) show the strain hardening and the strain rate hardening during the plastic deformation. The strain hardening is induced by deformation resistance of dislocation glide on some crystallographic systems and increase of the dislocation density on grain boundaries or inner grain. However, the phenomenon of the strain rate hardening is not demonstrated distinctly. In this paper, tensile tests for various strain rates are performed in the rage of $10^{-2}$ to $10^2s^{-1}$ then, specimens are extracted on the same strain position to investigate the microscopic behavior of deformed materials. The extracted specimen is investigated by using the electron backscattered diffraction(EBSD) and transmission electron microscopy(TEM) results which contain grain size, grain shape, aspect ratio and dislocation substructure.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.136-146
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• 1990

Whiskers of SiC were grown from the mixture of silica and graphite powders by Acheson method(direct heating method). The structrua, morphological and chemical characterizations have been performed by X-ray diffractometer(XRD), transmission electron microscopy(TEM), optical microscopy(OM), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and energy dispersive spectrometer(EDS). The growth mechanism of SiC whiskers is also discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.179-179
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• 2016

A radio-frequency (RF) Inductively Coupled Plasma (ICP) torch system was used for boron-nitride nano-tube (BNNT) synthesis. Because of electrodeless plasma generation, no electrode pollution and effective heating transfer during nano-material synthesis can be realized. For stable plasma generation, argon and nitrogen gases were injected with 60 kW grid power in the difference pressure from 200 Torr to 630 Torr. Varying hydrogen gas flow rate from 0 to 20 slpm, the electrical and optical plasma properties were investigated. Through the spectroscopic analysis of atomic argon line, hydrogen line and nitrogen molecular band, we investigated the plasma electron excitation temperature, gas temperature and electron density. Based on the plasma characterization, we performed the synthesis of BNNT by inserting 0.5~1 um hexagonal-boron nitride (h-BN) powder into the plasma. We analysis the structure characterization of BNNT by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy), also grasp the ingredient of BNNT by EELS (Electron Energy Loss Spectroscopy) and Raman spectroscopy. We treated bundles of BNNT with the atmospheric pressure plasma, so that we grow the surface morphology in the water attachment of BNNT. We reduce the advancing contact angle to purity bundles of BNNT.

• Applied Microscopy
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• v.36 no.spc1
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• pp.25-33
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• 2006

Nanofabrication with finely focused ion and electron beams is reviewed, and position and size controlled fabrication of nano-metals and -semiconductors is demonstrated. A focused ion beam (FIB) interface attached to a column of 200keV transmission electron microscope (TEM) was developed. Parallel lines and dots arrays were patterned on GaAs, Si and $SiO_2$ substrates with a 25keV $Ga^+-FIB$ of 200nm beam diameter at room temperature. FIB nanofabrication to semiconductor specimens caused amorphization and Ga injection. For the electron beam induced chemical vapor deposition (EBI-CVD), we have discovered that nano-metal dots are formed depending upon the beam diameter and the exposure time when decomposable gases such as $W(CO)_6$ were introduced at the beam irradiated areas. The diameter of the dots was reduced to less than 2.0nm with the UHV-FE-TEM, while those were limited to about 15nm in diameter with the FE-SEM. Self-standing 3D nanostructures were also successfully fabricated.

• Microbiology and Biotechnology Letters
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• v.15 no.2
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• pp.95-97
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• 1987

The protoplast formation of Streptomyces mitakaensis was monitored with scanning electron microscopy and transmission electron microscopy. The normal cells formed regular mycelium and spore, and their cell wall and cell membrane appeared to be normal, but the cell wall of the lysozyme treated cells (1 mg/$m\ell$) was damaged, which was finally disappeared from cells to become protoplast in 30 to 60 minutes.

• Vacuum Magazine
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• v.4 no.4
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• pp.18-22
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• 2017

Transmission electron microscopy (TEM) is a versatile and powerful technique that enables direct visualization of biological samples of sizes ranging from whole cell to near-atomic resolution details of a protein molecule. Thanks to numerous technical breakthroughs and monumental discoveries, 3D electron microscopy (3DEM) has become an indispensable tool in the field of structural biology. In particular, development of cryo-electron microscopy(cryo-EM) and computational image processing played pivotal role for the determination of 3D structures of complex biological systems at sub-molecular resolution. Here, basis of TEM and 3DEM will be introduced, especially focusing on technical advancements and practical applications. Also, future prospective of constantly evolving 3DEM field will be discussed, with an anticipation of great biological discoveries that were once considered impossible.