• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.381-386
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• 2010

Some basic properties of inorganic coatings hardened by the room temperature reaction with alkalies were examined. The coating paste was prepared from the powders in the system $Al_2O_3-SiO_2$-CaO using blast furnace slag, fly ash and amorphous ceramic fiber after mixing with a solution of sodium hydroxide and water glass. The mineralogical and morphological examinations were performed for the coatings prepared at room temperature and after heating to $1200^{\circ}C$ respectively. The binding force of the coating hardened at room temperature was caused by the formation of fairly dense matrix mainly composed of oyelite-containing amorphous phase formed by the reaction between blast furnace slag and alkali solution. At the temperature, fly ash and ceramic fiber was not reacted but imbedded in the binding phase, giving the fluidity to the paste and reinforcing the coating respectively. During heating up to $1200^{\circ}C$, instead of a break in the coating, anorthite and gehlenite was crystallized out by the reaction among the binding phase and unreacted components in ternary system. The crystallization of these minerals revealed to be a reason that the coating maintains dense morphology after heating. The maintenance of binding force after heat treatment is seemed to be also caused by the formation of welldispersed fiber-like mineral phase which is originated from the shape of the amorphous ceramic fiber used as a raw materials.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1311-1313
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• 1994

The development of an insulated coating which can be used for amorphous alloys is extremely important from the practical point of view. This importance may be enhanced by the influence of the coating on the magnetic properties. The aim of the study is to show how some coating influence the magnetic properties of $Fe_{87}Zr_7B_5Ag_1(at%)$ amorphous alloy.

• Journal of Magnetics
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• v.11 no.3
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• pp.126-129
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• 2006

The phosphate coating on the $(Fe_{0.97}Cr_{0.03})_{76}(Si_{0.5}B_{0.5})_{22}C_2$ amorphous powders with an average size of 10 ${\mu}m$ in diameter has been carried out in aqueous 1.0-2.0 wt% $H_3PO_4$ solutions, and the consolidation behavior and magnetic properties of their compressed powder cores has been investigated. The phosphate coating could provide efficient electrical insulation between amorphous powders and improved consolidation ability at room temperature. Especially when the powders were treated in more concentrated phosphoric acid solution, enhanced phosphate covering and higher frequency/dc-bias stability were achieved. The powder cores phosphate-coated in 2.0 wt% $H_3PO_4$ solution exhibited constant permeability of 21 up to 10 MHz, 110 of the quality factor at 0.9 MHz, 610 mW/cm3 core loss at 100 kHz/0.1 T and 89 of percent permeability at 100 kHz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.953-959
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• 2004

BaTiO$_3$ powder has been applied in so much electronic ceramics. Therefore, as recent, the method to add or coat additive will be needed BaTiO$_3$ powder. As a kind of the method, the coating of BaTiO$_3$ powder was considered. In this study, during BaTiO$_3$ powder was coated by BaTiO$_3$ sol, gelation path was experimented. Standard coating condition was set for homogeneous coating. The phase of the gel was deferent by gelation path. It was confirmed the amorphous gel was made in BaTiO$_3$ phase easily at low temperature. In the amorphous gel, particle growth was shown at 900$^{\circ}C$, because crystallization temperature was low. The optimal ratio of sol and powder was at 10 vol% for the homogeneous coating.

• Journal of Welding and Joining
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• v.25 no.4
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• pp.42-48
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• 2007

An inert gas atomized NiTiZrSiSn bulk metallic glass feedstock was sprayed onto the copper plate using vacuum plasma spraying process. In order to change the in-flight particle energy, that is, thermal energy, the hydrogen gas flow rate in plasma gas mixture was increased at the constant flow rate of argon gas. Coating and single pass spraying bead were produced with the least feeding rate. Regardless of the plasma gas composition, fully melted through unmelted particle could be observed on the overlay coating. However, the frequency of the unmelted particle number density was increased with the decrease of the hydrogen gas flow rate. The amorphous phase fraction within coating was also affected by the number density of the unmelted particle.

• Journal of the Korean institute of surface engineering
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• v.35 no.3
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• pp.133-140
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• 2002

The Ti-Si-N coating layers were synthesized on SKD 11 steel substrate by a DC reactive magnetron co-sputtering technique with separate Ti and Si targets. The high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses for the coating layers revealed that microstructure of Ti-Si-N layer was nanocomposite, consisting of nano-sized TiN crystallites surrounded by amorphous $Si_3$$N_4$ phase. The highest hardness value of about 39 GPa was obtained at the Si content of ~11at.%, where the microstructure had fine TiN crystallites (about 5nm in size) dispersed uniformly in amorphous matrix. As the Si content in Ti-Si-N films increased, the TiN crystallites became from aligned to randomly oriented microstructure, finer, and fully penetrated by amorphous phase. Free Si appeared in the layers due to the deficit of nitrogen source at higher Si content. Friction coefficient and wear rate of the Ti-Si-N coating layer significantly decreased with increase of relative humidity. The self-lubricating tribe-layers such as $SiO_2$ or (OH)$Si_2$ seemed to play an important role in the wear behavior of Ti-Si-N film against steel.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.621-625
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• 1996

A variety of metal oxides were coated by sol-gel process from their metal alkoxides on the ribbons of Co-based and Fe-based amorphous alloys, and the effects of surface oxide coating on the magnetic properties of the alloy are investigated. The core loss is found to be reduced significantly by the oxide coating, the loss reduction becoming more prominent at higher frequencies. The shape of the hystersis loop is also dependent upon the kind of the coated metal oxide. The coatings of MgO, SiO2, MgO·SiO2 and MgO·Al2O3 induce tensile stress into the Fe-based ribbon whereas those of BaO, Al2O3, CaO·Al2O3, SrO·Al2O3 and BaO·Al2O3 induce compressive stress. These results may be explained by the modification of domain structures via magnetoelastic interactions with the shrinkage stress induced by the sol-gel coating.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.90-95
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• 2005

The wire-arc process is a low-cost thermal spray method simply utilizes electrical energy to melt the feedstock wire. It is more userful for field applications, especially to coat large surface area. In this paper, a special Fe-based alloy coatings by using the wire-arc process were developed. Nanoscale composite coatings were achieved either during spraying or through a post heat treatment. As-sprayed Fe-based alloy coatings had been an amorphous matrix structure, after heating to $700^{\circ}C$ for 10 minutes a solid state transformation occurred in the some fraction of amorphous matrix which resulted in the formation of nanostructured recrystallized phase. Scanning electron microscopy (SEM) and field emotional scanning electron microscope(FE-SEM) were applied to analyze the microstructure of the coatings. Additionally hardness and bend resistance of the Fe-based alloy coatings were examined, and these results were compared with those of partially stabilized zirconia(PSZ) coatings by using the plasma spray process.

• Journal of the Korean institute of surface engineering
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• v.42 no.5
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• pp.220-226
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• 2009

Cr-O-N coatings having different oxygen contents were deposited on Si wafer and SUS 304 substrates by an arc ion plating technique using Cr target in $Ar/O_2/N_2$ gaseous atmosphere. As increasing oxygen content in the coating, the microstructure of Cr-O-N coating changed from polycrystalline having NaCl structure to amorphous structure. Further increase of oxygen content resulted in phase transformation from amorphous to rhombohedral structure. From the variations of d value and average grain size, it was revealed that the maximum solubility of oxygen in Cr-O-N coating was about 21 at.%. And the maximum micro-hardness of 2751HK was obtained in this composition. The lowest friction coefficient was measured in the coating having 34.8 at.% of oxygen. However, more narrow width of wear track was found in the coating having 30.1 at.% of oxygen.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.1
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• pp.1-5
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• 2012

The purpose of this study is to prepare a high strength fiberglass reinforced metal. Aluminum covering was carried out over carbon materials such as carbon fiber in order to increase their wettability to molten metals such as aluminum. A sputtering apparatus with a cylindrical target was fabricated to carry out the covering. Sputtering was caused by glow discharge between the target and the two anode plates attached to its top and bottom. As the substrate for preliminary test, a thin carbon wire was used instead of carbon fiber, and the wire was placed at the central axis of the target. Aluminium coating was formed on the whole surface of the substrate. The formation rate and structure of coating were varied by controlling the electrical potential of substrate. When the substrate was electrically isolated, coating with columnar structure was formed with a formation rate of $15{\mu}m/hr$. In case of grounded substrate, coating with amorphous structure was formed with a formation rate of $7{\mu}m/hr$.