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1
Content available Synthesis and Characterization of W Composite Powder with La2O3-Y2O3 Nano-Dispersoids by Ultrasonic Spray Pyrolysis
Heo Youn Ji, Lee Eui Seon, Kim Jeong Hyun, Lee Young-In, Jeong Young-Keun, Oh Sung-Tag
Archives of Metallurgy and Materials
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2022
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Vol. 67, iss. 4
1507--1510
EN
An optimum route to synthesis the W-based composite powders with homogeneous dispersion of oxide nanoparticles was investigated. The La2O3 dispersed W powder was synthesized by ultrasonic spray pyrolysis using ammonium metatungstate hydrate and lanthanum nitrate. The dispersion of Y2O3 nanoparticles in W-La2O3 powder was carried out by a polymer addition solution method using yttrium nitrate. XPS and Tem analyses for the composite powder showed that the nano-sized La2O3 and Y2O3 particles were well distributed in W powder. This study suggests that the combination processing of ultrasonic spray pyrolysis and polymeric additive solution is a promising way to synthesis W-based composite powders.
2
Content available Synthesis of Y2O3-Dispersed W Powders Prepared by Ultrasonic Spray Pyrolysis and Polymer Solution Route
Jo Hyeonhui, Lee Young-In, Suk Myung-Jin, Jeong Young-Keun, Oh Sung-Tag
Archives of Metallurgy and Materials
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2021
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Vol. 66, iss. 3
799--802
EN
The nano-sized Y2O3 dispersed W composite powder is prepared by ultrasonic spray pyrolysis of a tungsten precursor using ammonium metatungstate hydrate and a polymer addition solution method using Y-nitrate. XRD analysis for calcined powder showed the formation of WO2 phase by partial oxidation of W powder during calcination in air. The TEM and phase analysis for further hydrogen reduction of calcined powder mixture exhibited that the W powder with a uniform distribution of Y2O3 nanoparticles can be successfully produced. These results indicate that the wet chemical method combined with spray pyrolysis and polymer solution is a promising way to synthesis the W-based composites with homogeneous dispersion of fine oxide particles.
3
Content available Homogeneous Dispersion of Yttrium Oxide Particles in Nickel-Based Superalloy by High Pressure Homogenizing and Ball Milling Method
Byun Jongmin, Lee Young-In, Oh Sung-Tag
Archives of Metallurgy and Materials
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2021
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Vol. 66, iss. 4
1055--1058
EN
An optimum route to fabricate the Ni-based superalloy with homogeneous dispersion of Y2O3 particles is investigated. Ni-based ODS powder was prepared by high-energy ball milling of gas-atomized alloy powders and Y2O3 particles treated with a high-pressure homogenizer. Decrease in particle size and improvement of dispersion stability were observed by high-pressure homogenization of as-received Y2O3 particles, presumably by the powerful cavitation forces and by collisions of the particles. Microstructural analysis for the ball-milled powder mixtures reveal that Ni-based ODS powders prepared from high-pressure homogenization of Y2O3 particles exhibited more fine and uniform distribution of Ni and Y elements compared to the as-received powder. These results suggested that high-pressure homogenization process is useful for producing Ni-based superalloy with homogeneously dispersed oxide particles.
4
Content available Dilatometric Analysis of the Sintering Behavior of Bi2Te3 Thermoelectric Powders
Han Ju-Yeon, Byun Jong Min, Lee Young-In, Choi Byung Joon, Kim Hogyoung, Oh Sung-Tag
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 3
1117--1120
EN
The sintering behavior of p-type bismuth telluride powder is investigated by means of dilatometric analysis. The alloy powders, prepared by ball milling of melt-spun ribbons, exhibit refined and flake shape. Differential thermal analysis reveals that the endothermic peak at about 280°C corresponds to the melting of bismuth, and peaks existing between 410°C and 510°C are presumably due to the oxidation and crystallization of the powder. The shrinkage behavior of ball-milled powders was strongly dependent of heating rate by the thermal effect exerted on specimens. In the case of 2°C/min, the peak temperature for the densification is measured at 406°C, while the peak temperature at a heating rate of 20°C/min is approximately 443°C. The relative density of specimen pressureless-sintered at 500°C exhibited relatively low value, and thus further study is required in order to increase the density of sintered body.
5
Content available Effect of Process Control Agent on the Microstructure of Ni-Based ODS Superalloy Produced by Mechanical Alloying and Sintering
Han Ju-Yeon, Kang Hyunji, Oh Sung-Tag
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 3
949--952
EN
The effects of different types of process control agents (PCA) on the microstructure evolution of Ni-based oxide dispersion-strengthened superalloy have been investigated. Alloy synthesis was performed on elemental powders having a nominal composition of Ni-15Cr-4.5Al-4W-2.5Ti-2Mo-2Ta-0.15Zr-1.1Y2O3 in wt % using high energy ball milling for 5 h. The prepared powders are consolidated by spark plasma sintering at 1000°C. Results indicated that the powder ball-milled with ethanol as PCA showed large particle size, low carbon content and homogeneous distribution of elemental powders compared with the powder by stearic acid. The sintered alloy prepared by ethanol as PCA exhibited a homogeneous microstructure with fine precipitates at the grain boundaries. The microstructural characteristics have been discussed on the basis of function of the PCA.
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