• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2792-2794
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• 2009

• 한국분말재료학회지
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• 제15권6호
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• pp.489-495
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• 2008

Colored tantalum oxy-nitride (TaON) and tantalum nitride ($Ta_{3}N_{5}$) were synthesized by ammonolysis. Oxygen deficient tantalum oxides ($TaO_{1.7}$) were produced by a titration process, using a tantalum chloride ($TaCl_5$) precursor. The stirring speed and the amount of $NH_{4}OH$ were important factors for controling the crystallinity of tantalum oxides. The high crystallinity of tantalum oxides improved the degree of nitridation which was related to the color value. Synthesized powders were characterized by XRD, SEM, TEM and Colorimeter.

• 한국재료학회지
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• 제11권12호
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• pp.1047-1051
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• 2001

Purity tantalum powder has been produced by sodium reduction of potassium tantalum fluoride($K_2TaF_7$)in a stainless steel bomb. The influence of experimental variable, such as excess of reductant and temperature of reduction on the yield and quality of the Ta powder has been studied. The excesses of reductant were varied from -20%, -10%, 0%, 5%, 10%, 20%. When -20% excess of sodium was used, the un-reacted sodium remained in the reacted product. The yield of 81% of Ta powder has been achieved by reducing 50g of$K_TaF_7$with 5% sodium in excess of stoichiometric amount in presence of 16.8g of sodium chloride in the charge at a reduction temperature of$905{\circ}C$. The proportion of fine fraction(~325mesh) decreased appreciably with the increase of sodium excess, and the yield of tantalum powder improved from 65% to 94%. The average particle size of Ta Powder is improved from 3 microns to 4 microns in the 5% excess sodium.

• 한국세라믹학회지
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• 제46권6호
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• pp.583-586
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• 2009

The Tantalum nitride has attracted wide at attention as issues related to the toxicity of Cd-related materials. But in the titration process of Ta$Cl_5$ solution with $NH_4$OH, $NH_4$Cl, as a by product, was remained in the prepared Tantalum precursor. The tantalum precursor with $NH_4$Cl was nitrided by ammonolysis. The red color tone of $Ta_3N_5$ was reduced by the residual $NH_4$Cl reduce. Therefore, amorphous Tantalum precursor was prepared by filtering process with as hydrous ethanol to remove the $NH_4$Cl. In the case of using Tantalum precursor without $NH_4$Cl, we successfully synthesized the Tantalum nitride with good red color. The value of red color tone was improved from $a^*$=36.8 to $a^*$=53.0. The synthesized powder was characterized by XRD, SEM, the Nitrogen / Oxygen Determinator, TG-DTA, and the CIE $L^*a^*b^*$ colorimeter.

• 방사성폐기물학회지
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• 제18권3호
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• pp.337-346
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• 2020

Two commonly used ceramics in molten salt research are alumina and mullite. The two ceramics were exposed to a combination of rare earth chlorides (YCl₃, SmCl₃, NdCl₃, PrCl₃, and CeCl₃; each rare earth chloride of 1.8 weight percent) in LiCl-KCl at 773 K for approximately 13 days. Scanning electron microscopy with wave dispersion spectra was utilized to investigate a formation layer or deposition of rare earths onto the ceramic. Only the major constituents of the ceramics (Al, Si, and O₂) were observed during the wave dispersion spectra. X-ray fluorescence was used as well to determine concentration changes in the molten salt as a function of ceramic exposure time. This study shows no evidence of ionic exchange or layer formation between the ceramics and molten chloride salt mixture. There are signs of surface tension effects of molten salt moving out of the tantalum crucible into secondary containment.

• 한국세라믹학회지
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• 제53권6호
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• pp.597-603
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• 2016

Tantalum carbide, which is one of the ultra-high temperature ceramics, was deposited on graphite by low pressure chemical vapor deposition from a $TaCl_5-C_3H_6-Ar-H_2$ mixture. To maintain a constant $TaCl_5/C_3H_6$ ratio during the deposition process, $TaCl_5$ powders were continuously fed into the sublimation chamber using a screw-driven feeder. Sublimation behavior of $TaCl_5$ powder was measured by thermogravimetric analysis. TaC coatings have various phases such as $Ta+{\alpha}-Ta_2C$, ${\alpha}-Ta_2C+TaC_{1-x}$, and $TaC_{1-x}$ depending on the powder feeding methods, the $C_3H_6/TaCl_5$ ratio, and the deposition temperatures. Near-stoichiometric TaC was obtained by optimizing the deposition parameters. Phase compositions were analyzed by XRD, XPS, and Raman analysis.

• 한국재료학회지
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• 제14권12호
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• pp.857-862
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• 2004

Production of titanium powder directly from tantalum oxides ($TiO_2$) pellet through an electronically mediated reaction (EMR) by calciothermic reduction has been investigated. Feed material ($TiO_2\;pellet$) and reductant (Ca-Ni alloy) were charged into electronically isolated locations in a molten calcium chloride ($CaCl_2$) bath at $950^{\circ}C$. The current flow through an external circuit between the feed (cathode) and reductant (anode) locations was monitored during the reduction of $TiO_2$. The current approximately 3.2A was measured during the reaction in the external circuit connecting cathode and anode location. After the reduction experiment, pure titanium powder with low nickel content was obtained even though Ca-Ni alloy was used as a reductant. These results demonstrate that titanium powder can be produced without direct physical contact between the feed and reductant. In certain experimental conditions, pure titanium powder with approximately $99.5\;mass\%$ purity was successfully obtained.