Effects of Inhibitors on the Synthesization of WC/Co Composite Powders by Mechanochemical Method

Im, Hoo Soon; Hur, Jah Mahn; Lee, Wan Jae

doi:10.4028/www.scientific.net/MSF.534-536.1177

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Home Materials Science Forum Progress in Powder MetallurgyEffects of Inhibitors on the Synthesization of...

Effects of Inhibitors on the Synthesization of WC/Co Composite Powders by Mechanochemical Method

Abstract:

Nano-sized WC particles in WC/Co composite powders were synthesized by mechanochemical method. The raw powders(WO3, Co3O4, VC, Cr3C2 and graphite) were mixed by planetary milling with ethyl alcohol for 30 hours. The compositions were WC-10 and -20 wt% Co after reduction and carburization. The powders of VC and Cr3C2 were added as the inhibitors to inhibit the formation of nano-sized WC particles. The direct reduction and carburization of the oxides with carbon were carried at 900°C for 1 to 3 hours under flowing Ar gas. The resultant powders were compacted and sintered at 1300~1360°C for 0.5 hour. The degree of the direct reduction and carburization of the mixed powders increased with the reaction time. The mean size of WC particles in WC/Co composite powders was about 16 nm, and the mean size of WC/Co composite powders was about 240 nm. In WC-10 and -20 wt% Co, the sintered compacts shrank by 16% and 24%, respectively. The mean sizes of WC in WC/Co composite powders were about 50 and 30 nm.

Info:

Periodical:

Materials Science Forum (Volumes 534-536)

Main Theme:

Progress in Powder Metallurgy

Edited by:

Duk Yong Yoon, Suk-Joong L. Kang, Kwang Yong Eun and Yong-Seog Kim

Pages:

1177-1180

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.534-536.1177

Citation:

H. S. Im et al., "Effects of Inhibitors on the Synthesization of WC/Co Composite Powders by Mechanochemical Method", Materials Science Forum, Vols. 534-536, pp. 1177-1180, 2007

Online since:

January 2007

Authors:

Hoo Soon Im, Jah Mahn Hur, Wan Jae Lee

Keywords:

Direct Reduction and Carburization, Mechanochemical Method, Nanosized WC, Sintering, WC/Co Composite Powder

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References

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Paper TitlePages

Fabrication and Evaluation of Ca-α SiAlON Nano Ceramics

Authors: Junichi Tatami, Moegi Iguchi, Mikinori Hotta, Cheng Zhang, Katsutoshi Komeya, Takeshi Meguro, Mamoru Omori, Toshio Hirai, Manuel E. Brito, Yi Bing Cheng

105

Liquid Phase Sintering Behavior of Amorphous Nano-Sized Silicon Nitride Powders

Authors: H.B. Li, Jun Ting Luo, Kai Feng Zhang

Abstract: The amorphous nano-sized silicon nitride powders were sintered by liquid phase sintering method. Si3N4-Si2N2O composites were in-situ fabricated. The Si2N2O phase was generated by an in-situ reaction 2Si3N4(s)+1.5O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% was obtained at a sintering temperature of 1650°C and reduced when the sintering temperature increased or decreased, which indicates that the reaction is reversible. The mass loss, relative density and average grain size increase with increasing of sintering temperature. The average grain size is less than 500nm when the sintering temperature is below 1700°C. During the sintering procedure, there is a complex crystallization and phase transition: amorphous Si3N4 → equiaxial α-Si3N4→ equiaxial β-Si3N4 → rod-likeSi2N2O → needle-like β-Si3N4. Small round-shaped β-Si3N4 particles are entrapped in the Si2N2O grains and a high density of staking faults are situated in the middle of Si2N2O grains at a sintering temperature of 1650°C.

1069

Hot Press Sintering Behavior of Nano-Sized AlN Powders

Authors: Hong Bo Li, Jun Ting Luo, Yong Fei Gu, Yan Xia Xu

Abstract: Aluminum nitride (AlN) is a stoichiometric compound with the hexagonal wurtzite structure. AlN has excellent thermal conductivity and good properties as electronic insulator. It displays good mechanical resistance up to elevated temperatures and is resistant against corrosion by molten metals. Bulk AlN may therefore be used as a refractory structural material as well as a substrate for high power microelectronic devices. However, it is very difficult for sintering high-density AlN at lower temperature than 1800°C. Nano-sized AlN powders were sintered by hot press sintering at low temperature of 1500~1700°C and mechanical properties were investigated. β-AlN and β-Al2O3 were detected when the sintering temperature is 1600°C. The phase transition β-AlN to α-AlN was discovered at a 1700°C sintering temperature. Relative density and average grain size were increasing with the increasing of sintering temperature, and fracture form is intercrystalline crack in 1500°C and transcrystalline crack in 1700°C. 97.3% relative density and 850nm average grain size were deserved at 1700°C.

720

Cold Isostatic Pressing–Normal Pressure Sintering Behavior of Amorphous Nano-Sized Silicon Nitride Powders

Authors: Jun Ting Luo, Chun Xiang Zhang, Hai Feng Ma, Ge Wang

Abstract: The amorphous nano-sized silicon nitride powders were sintered by cold isostatic pressing –normal press sintering method. The sintering additives of Y2O3 and Al2O3 powders with average grain size less than 20nm were prepared by polyacrylamide gel method. Relative density of sintered materials rise and pore size reduce with increasing of cold isostatic pressing. When the pressure is 100MPa, the density is only 48% and average pores size is between 2μm and 20μm which obvious the first particle space. When the pressure is 200MPa, the density is 67% and agglomerated particle size reduce obviously as well as the pores size are between 0.1μm and 1.0μm which appears because of the second particle. Pressed compact with a relative density 74% and average pore size less than 0.5μm reach to a good density state at 300MPa pressure. Sintering material composites with Si2N2O and β-Si3N4 phases, compared with hot press sintering composites, which indicates that increasing of sintering press is conducive to the formation phase Si2N2O. Relative density is above 96% and average pore size is less than 500nm at sintering temperature 1800°C.

A Novel Method for the Preparation of Nano-Sized Nickle Powders

Authors: Zhao Han, Hong Min Zhu

Abstract: Nano-sized nickel powders were prepared through a wet chemical reduction, of NiCl₂ by sodium in liquid ammonia at -45 °C, and a subsequent heat-treatment in vacuum at 300 °C. The prepared product was systematically characterized by X-ray diffraction (XRD), scan electron microscopy (SEM), transmission electron microscopy (TEM), and BET specific surface area measurement. The results show that the product was composed of nano-sized nickel particles, with average particle diameter of about 20 nm, and specific surface area of about 30 m²g^-1. The possible formation mechanism of the nano-sized nickel powder was also discussed briefly.

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