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Homogeneous WC–Co-Cemented Carbides from a Cobalt-Coated WC Powder Produced by a Novel Solution-Chemical Route
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
2007 (English)In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 90, no 11, 3449-3454 p.Article in journal (Refereed) Published
Abstract [en]

A solution chemical route to cobalt-coated WC-powder is described that allows for the preparation of WC–Co powders and compacts having a carbon content very close to the desired carbon content even under an inert atmosphere. The microstructural homogeneity in the sintered WC–Co composites when using the Co-coated grains was found to be superior as compared with conventionally mill-mixed powders, and the structural changes in the individual WC-grains were found to be much smaller, which is ascribed mainly to the fact that the coated grains do not require a grinding step leading to the formation of a tail of smaller WC grain sizes.

Place, publisher, year, edition, pages
2007. Vol. 90, no 11, 3449-3454 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-12096DOI: 10.1111/j.1551-2916.2007.01948.xISI: 000250762100011OAI: oai:DiVA.org:uu-12096DiVA: diva2:39865
Available from: 2007-11-26 Created: 2007-11-26 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Novel powder-coating solutions to improved micro-structures of ZnO based varistors, WC-Co cutting tools, and Co/Ni nano-phase films and sponges
Open this publication in new window or tab >>Novel powder-coating solutions to improved micro-structures of ZnO based varistors, WC-Co cutting tools, and Co/Ni nano-phase films and sponges
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Solution chemistry is a versatile and powerful tool in the synthesis of designed, complex nano-level high-tech materials. Normally, the technique is considered too expensive for large-scale production of complex multi-component ceramic materials. This thesis describes the expansion of the useful area of solution processing to multi-component bulk materials such as ZnO-based high-field varistors and WC–Co cutting tools, by developing novel techniques for solution-based coating of conventionally prepared metal and ceramic powders. The chemistry and microstructure development in the preparation of coatings, and the sintering of the coated powders to compacts, were studied in detail by SEM-EDS, TEM-EDS, XRD, IR-spectroscopy, dilatometry, TGA and DSC chemical analysis.

ZnO powder with a ca 20 nm thick, homogeneous oxide coat of Bi–Sb–Ni–Co–Mn–Cr–Al oxide was prepared. After sintering to dense varistor bodies, much improved microstructures with much reduced ZnO-grain sizes were obtained. This shows that the oxides added as liquid sintering aid and grain-growth inhibitor become much more active when added homogeneously as a skin on the ZnO powder.

After sintering of cobalt-coated WC, much improved micro-structures were obtained with a much more narrow WC grain-size distribution than that obtained from starting powders mixed by a conventional milling route. Coated powders also obviate the need for the extensive milling of WC and Co powders used in conventional mixing.

The novel solution route was also applied to preparation of porous sponges and thin films on metal, glass and Al2O3 of sub 20 nm sized Co- or Ni-particles.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. 45 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 699
Keyword
Chemistry, Solution processing, powder coating, nano-phase materials, sintering process, varistor, WC–Co, cobalt, nickel, films, sponges, Kemi
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-1948 (URN)91-554-5275-2 (ISBN)
Public defence
2002-04-24, Häggsalen, Ångström-laboratoret, Uppsala, 10:15
Opponent
Available from: 2002-04-03 Created: 2002-04-03 Last updated: 2014-01-24Bibliographically approved

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Westin, Gunnar

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