• Journal of Powder Materials
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• v.16 no.2
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• pp.110-114
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• 2009

Mechanical coating process was applied to form 89 %-hydrolyzed poly vinyl alcohol (PVA) onto boron carbide ($B_4C$) nanopowder using one step high energy ball mill method. The polymer layer coated on the surface of B4C was changed to glass-like phase. The average particle size of core/shell structured $B_4C$/PVA was about 50 nm. The core/shell structured $B_4C$/PVA was formed by dry milling. However, the hydrolyzed PVA of $98{\sim}99%$ with high glass transition temperature ($T_g$) was rarely coated on the powder. The $T_g$ of polymer materials was one of keys for guest polymer coating on to the host powder by solvent free milling.

• Journal of Powder Materials
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• v.27 no.1
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• pp.8-13
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• 2020

In this study, we investigated the effects of precipitates and oxide dispersoids on the high-temperature mechanical properties of oxide dispersion-strengthened (ODS) Ni-based super alloys. Two ODS Ni-based super alloy rods with different chemical compositions were fabricated by high-energy milling and hot extrusion process at 1150 ℃ to investigate the effects of precipitates on high-temperature mechanical properties. Further, the MA6000N alloy is an improvement over the commercial MA6000 alloy, and the KS6000 alloy has the same chemical composition as the MA6000 alloy. The phase and microstructure of Ni-based super alloys were investigated by X-ray diffraction and scanning electron microscopy. It was found that MC carbide precipitates and oxide dispersoids in the ODS Ni-based super alloys developed in this study may effectively improve high-temperature hardness and creep resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.735-738
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• 2002

Single crystal 3C-SiC(cubic silicon carbide) thin-films were deposited on Si(100) substrate up to a thickness of $4.3{\mu}m$ by APCVD method using HMDS(hexamethyildisilane) at $1350^{\circ}C$. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like crystal surface. The growth rate of the 3C-SiC films was $4.3{\mu}m/hr$. The 3C-SiC epitaxical films grown on Si(100) were characterized by XRD, AFM, RHEED, XPS and raman scattering, respectively. The 3C-SiC distinct phonons of TO(transverse optical) near $796cm^{-1}$ and LO(longitudinal optical) near $974{\pm}1cm^{-1}$ were recorded by raman scattering measurement. The heteroepitaxially grown films were identified as the single crystal 3C-SiC phase by XRD spectra$(2{\theta}=41.5^{\circ})$.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.561-571
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• 1999

Microstructure and mechanical properties of five Cr-Mo steels for nuclear industry applications have been investigated. Transmission electron microscopy, energy dispersive spectrometer, differential scanning calorimeter, hardness, tensile, and impact test were used to evaluate the Cr and W effect on the microstructure and mechanical properties. Microstructures of Cr-Mo steels after tempering are classified into three types : bainitic 2.25Cr-lMo steel, martensitic Mod.9Cr-lMo, HT9M, and HT9W steels, and dual phase HT9 steel. The majority of the precipitates were found to be M$_{23}$C$_{6}$ carbides. As minor phases, fine needle-like V(C,N), spherical NbC, fine needle-like Cr-rich Cr$_2$N, and Cr-rich M$_{7}$C$_3$were also found. Addition of 2wt.% W in Cr-Mo steels retarded the formation of subgrain and dissolution of Cr$_2$N precipitates. Hardness and ultimate tensile strength increased with increasing Cr content. Though Cr content of HT9W steel was lower than that of HT9 steel, the hardness of HT9W was higher due to the higher W content. W added HT9W steel had the highest ultimate tensile strength above $600^{\circ}C$. But impact toughness of W added steel (HT9W) and high Cr steel (HT9) was low.w.w.

• Korean Journal of Crystallography
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• v.5 no.1
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• pp.39-50
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• 1994

Diamond thin films were deposited on silicon, molybdebum, titanum and tugsten substrates, and were chlwntnizen using scanning electron microscopy, X-ray diffraction analysis and Raman spectroscopy. From the result of experiment in various deposition periods, it was found that found that were nucleated and grown on interlayed carbide layers, which were formed on refractory metal substrates at the initial stage of.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.953-957
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• 2002

Single crystal 3C-SiC (cubic silicon carbide) thin-films were deposited on Si(100) wafer up to the thickness of 4.3 ${\mu}{\textrm}{m}$ by APCVD (atmospheric pressure chemical vapor deposition) method using HMDS (hexamethyildisilane; ｛CH$_{3}$｝$_{6}$ Si$_{2}$) at 135$0^{\circ}C$. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like crystal surface. The growth rate of the 3C-SiC film was 4.3 ${\mu}{\textrm}{m}$/hr. The 3C-SiC epitaxial film grown on Si(100) wafer was characterized by XRD (X-ray diffraction), AFM (atomic force microscopy), RHEED (reflection high energy electron diffraction), XPS (X-ray photoelecron spectroscopy), and Raman scattering, respectively. Two distinct phonon modes of TO (transverse optical) near 796 $cm^{-1}$ / and LO (longitudinal optical) near 974$\pm$1 $cm^{-1}$ / of 3C-SiC were observed by Raman scattering measurement. The heteroepitaxially grown film was identified as the single crystal 3C-SiC phase by XRD spectra (2$\theta$=41.5。).).

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.131-135
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• 2004

The effect of Co additive on the microstructural evolusion of WC was investigated. A small amount of Co powder was placed on the top-center of the pure WC powder compact and then sintered at 1950$^{\circ}C$. During sintering some abnormally large WC grains of different size and shape observed depending on the distance from the liquid source. However, in the region far away from Co liquid source, it showed low densification and the grains of WC were very small and uniform in size. A small amount of Co liquid phase has a remarkable influence on the AGG of WC and it has been explained in terms of 2-D nucleation and growth mechanism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.533-536
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• 2001

Single crystal cubic silicon carbide(3C-SiC) thin film were deposited on Si(100) substrate up to a thickness of $4.3{\mu}m$ by APCVD(atmospheric pressure chemical vapor deposition) method using hexamethyildisilane(HMDS) at $1350^{\circ}C$. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like. The growth rate of the 3C-SiC films was $4.3{\mu}m/hr$. The 3C-SiC epitaxical layers on Si(100) were characterized by XRD(X-ray diffraction), raman scattering and RHEED(reflection high-energy electron diffraction), respectively. The 3C-SiC distinct phonons of TO(transverse optical) near $796cm^{-1}$ and LO(longitudinal optical) near $974{\pm}1cm^{-1}$ were recorded by raman scattering measurement. The deposition films were identified as the single crystal 3C-SiC phase by XRD spectra($2{\theta}=41.5^{\circ}$). Also, with increase of films thickness, RHEED patterns gradually changed from a spot pattern to a streak pattern.

• Journal of the Korean institute of surface engineering
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• v.28 no.6
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• pp.368-375
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• 1995

Thermal CVD method is in general used for the fabrication of TiC/$Al_2O_3$-coated carbide tools. The growth of TiC layer and the coating morphology depended on the chemical composition of the hard metal substrate on which the tool properties were strongly influenced. TiC-coated layer was grown by the diffusion of carbon from the substrate, whereas the growth of $Al_2O_3$ layer was unrelated to the composition of substrate. In the nitride hard coatings of Zr, Nb and Mo metals deposited on high speed steel substrate by magnetron sputtering, the reactivity of the metal elements was decreased with increasing group number in one period of the periodic system. The hard material films exhibited the highest adhesion with the chemical composition of stoichiometry or substoichiometry. The critical load as a measure of adhesion was evaluated using scratch tester. The CVD tools indicated the values of 80 and 40N in the coated layers with proper bonding to the substrate and with $\eta$ phase of 1$\mu\textrm{m}$ in the interface respectively, but the nitride films prepared by sputtering of PVD showed only the values between 10 and 20N.

• Tribology and Lubricants
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• v.11 no.5
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• pp.99-107
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• 1995

This paper reported research results to develop an algorithm of on-lin evaluation of surface profiles and roughness generated by turning. The developed module consisted of computer simulation of surface profiles using mechanism of cutting mark formation and cutting vibrations, and online measurement of cutting vibrations. The relative cutting vibrations between tool and worpkiece were measured through an inductance pickup at the rate of one sample per rotation of the workpiece. The sampling process was monitored using an encoder to avoid conceling out the phase lag between waves. The digital cutting signals from the Analog-to-Digital converter were transferred to the simulation module of surface profile where the surface profiles were generated. The developed algorithm or surface generation in a hard turning was analyzed through computer simulations to consider the stochastic and dynamic nature of cutting process. Cutting tests were performed using AISI 304 Stainless Steel and carbide inserts in practical range of cutting conditions. Experimental results showed good correlation between the surface profiles and roughness obtained using the developed algorithm and the surface texture measured using a surface profilemeter. The research provided the feasibility to monitor surface characteristics during tribelogical tests considering wear effect on surface texture in machining.