Mechanical and magnetic properties of Ni-Co dispersed Al2O3 nanocomposites

Effects of the fabrication processing on the microstructure and properties of composites were investigated. High-density Ni-Co dispersed-Al2O3 (Al2O3/Ni-Co) composites were obtained by hydrogen reduction and consolidated using hot pressing and pulse electric current sintering (PECS) of Al2O3, Ni(NO3...

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Bibliographic Details
Published in:Journal of materials science 2001-04, Vol.36 (7), p.1817-1821
Main Authors: OH, Sung-Tag, SANDO, Mutsuo, NIIHARA, Koichi
Format: Article
Language:English
Subjects:
Aluminum oxide
Applied sciences
Ball milling
Building materials. Ceramics. Glasses
Ceramic industries
Chemical industry and chemicals
Coercivity
Exact sciences and technology
Ferromagnetism
Grain boundaries
Hot pressing
Hydrogen reduction
Magnetic properties
Magnetism
Materials science
Metals. Metallurgy
Microstructure
Miscellaneous
Nanocomposites
Other composite materials with one or more metallic components
Powder metallurgy. Composite materials
Production techniques
Sintering (powder metallurgy)
Technical ceramics
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Summary:Effects of the fabrication processing on the microstructure and properties of composites were investigated. High-density Ni-Co dispersed-Al2O3 (Al2O3/Ni-Co) composites were obtained by hydrogen reduction and consolidated using hot pressing and pulse electric current sintering (PECS) of Al2O3, Ni(NO3)2·6H2O and Co(NO3)2·6H2O powder mixtures. Microstructural investigations of the hot-pressed composite fabricated using again wet/dry ball-milled powder mixture after calcination revealed that fine Ni-Co particles, about 145 nm in diameter, dispersed homogeneously at the matrix grain boundaries. In particular, fine microstructure of dispersion with the average size of 90 nm was realized for the specimen consolidated by PECS method. High strength of over 1 GPa and hardness of 19 GPa were measured for the nanocomposites prepared from the again ball-milled powder mixture. The ferromagnetism of nano-sized Ni-Co contributes to the magnetic properties of the composites. A change in the coercive force with dispersion size was observed. Also, the extent of magnetic response by an applied stress was strongly influenced by the size of Ni-Co particles. The relations between microstructure and mechanical as well as magnetic properties are discussed.
ISSN:0022-2461
1573-4803
DOI:10.1023/A:1017541112681