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Hartstoffverstaerkte Zr02-Keramik mit mechanischer Stabilitaet unter hydrothermaler Beanspruchung, Verfahren zu deren Herstellung und Verwendung

New hard material-reinforced stabilised zirconia ceramic - has high mechanical stability under hydrothermal conditions.
 
: Krell, A.; Blank, P.

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Frontpage ()

DE 1996-19640923 A1: 19961004
DE 1997-19733700 A: 19970804
DE 19733700 C2: 19990602
C04B0035
German
Patent, Electronic Publication
Fraunhofer IKTS ()

Abstract
A novel, hard material-reinforced, stabilised ZrO2 ceramic, with mechanical stability under hydrothermal conditions, has the composition (by vol.) 5-50% hard material component with 0.2-1 mu m grain size, 2-45% Al2O3 with 0.1-1 mu m grain size and balance ( at least 30%) stabilised ZrO2 phase with a solid solution of 2-3.5 mol% Y2O3 and 1-7 mol% CeO2 (based on the ZrO2 content in the starting powder composition) and with 0.2-0.7 mu m grain size. Production of the above ceramic involves: (a) providing a ZrO2 powder which contains Y2O3 in solid solution and which is doped with Ce with high spatial distribution homogeneity wrt. the ZrO2 particles, this homogeneity being fixed for the subsequent process steps without significantly modifying the electrokinetic properties at the ZrO2 particle surfaces; (b) subjecting this ZrO2 powder, of less than 0.5 mu mean particle size, to wet mixing and grinding together with a hard material component of less than 5 mu m mean particle size and Al2O3 of less than 0.7 mu m mean particle size, with addition of the requisite organic pressing aid and sintering additive; and (c) moulding and sintering the resulting mixture. Preferably, the hard material component is TiC of any stoichiometry. The stabilised ZrO2 preferably has a primary particle size of 10-60 nm and the Al2O3 preferably contains at most 2% coarse particles of greater than 2 mu M size. The sintering additive preferably comprises 2-10 wt.% TiH2. USE - In components, tools or instruments used under hydrothermal conditions, especially in roller or plain bearings (claimed). ADVANTAGE - The ceramic has high hydrothermal stability (without requiring an extremely fine ZrO2 phase grain size or a high Ce doping level), combined with high strength (e.g. a bending strength of 900 MPa or more) and hardness, and can be produced without use of processes (e.g. hot pressing) which limit the product geometry or which employ chemical reactions.

: http://publica.fraunhofer.de/documents/PX-16804.html