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ALTERNATIVE STABILISERS FOR ZIRCONIA CERAMICS:POWDERS DERIVED BY PROCESSING OF EUDIALYTE

Objective

THE PROGRAMME WILL ASSESS THE POWDER QUALITY IN TERMS OF THE STRENGTH, TOUGHNESS AND STABILITY OF THE RESULTING CERAMICS, A MAJOR OBJECTIVE BEING THE IDENTIFICATION OF OPTIMUM STABILISER COMPOSITIONS.

COLLABORATION IN THE WORK INVOLVES TEAMS EXPERIENCED IN MINERALS PRODUCTION AND UPGRADING IN CHEMICAL EXTRACTION METHODS, IN POWDER PREPARATION AND CHARACTERIZATION, AND IN CERAMICS PREPARATION AND TESTING.

THE AIM OF THE WORK IS TO MAKE AVAILABLE WITHIN EUROPE A LOW COST FEED MATERIAL FOR THE PREPARATION OF ZIRCONIA CERAMICS WHICH OFFERS, IN ADDITION TO THE ECONOMIC BENEFIT, COMPOSITIONS OF ENHANCED STABILITY AND HENCE RELIABILITY.
The purification process found to yield feasible powder material used sulphuric acid in purification reactions. Further extraction steps were used for separation and purification of zirconium oxide, and especially the yttrium-rare earth element oxide fractions. 2 sulphate based laboratory scale routes for the fabrication of closely specified TZP powders stabilized by a wide range of yttrium-rare earth element oxide mixtures were developed.
The co-precipitation/calcination/milling route developed leads to powders containing significant residual sulphite ion. However, with a properly adjusted sintering scheme, high quality TZP ceramics are easily prepared from these powders.
The hydrothermal route developed offers the advantages of a simplified processing scheme, the avoidance of organic solvents in the washing steps and a possible complete elimination of residual sulphite ion.
The study of different mixed yttrium-rare earth element oxides stabilizers showed that it is possible to produce high strength, moderate toughness TZP ceramics with improved ageing behaviour in aqueous solutions using inexpensive mixtures.

Eudialyte also consists of other oxides. These were evaluated for their potential in the manufacture of ceramics with wide ranging properties. Several different quality ceramics were synthesized.
CRITICAL PROBLEMS FOR THE DEVELOPMENT OF ENGINEERING CERAMICS ARE FOUND IN RESPECT TO RELIABILITY AND COST.
FOR ZIRCONIA BASED CERAMICS, A MAJOR CONCERN IS TO ENSURE THE STABILITY FOR THE REQUIRED LIFETIMES OF THE METASTABLE STRUCTURES THAT ARE REQUIRED FOR HIGH STRENGTH AND TOUGHNESS (TRANSFORMATION TOUGHENING). THE LOSS OF STRENGTH OF MATERIAL EXPOSED TO MOISTURE AT 25 CELSIUS DEGREES IS A MOST IMPORTANT EXAMPLE.
THE PROPOSED WORK SETS OUT TO SOLVE THESE PROBLEMS IN TWO WAYS, NAMELY (I) TO USE A LOW COST RAW MATERIAL AS THE SOURCE MATERIAL FOR THE ZIRCONIA AND FOR THE STABILISING OXIDES USED IN MAKING ZIRCONIA CERAMICS (IN PLACE OF YTTRIUM OXIDE), AND (II) TO USE MULTICOMPONENT STABILISING ADDITIVES TO RETARD THE RATE OF MICROSTRUCTURAL CHANGE (INFLUENCE ON DIFFUSION PROCESSES), A MAJOR COMPONENT BEING CEO2.
THE WORK EXPLOITS THE AVAILABILITY OF EUDIALYTE AS A SOURCE MINERAL FOR ZIRCONIA AND STABILISERS (Y, RARE EARTH OXIDES); THIS IN COMBINATION WITH SOURCES OF CEO2 WILL BE TREATED BY IDENTIFIED EXTRACTION METHODS TO PREPARE ACTIVE, MIXED STABILISER, LOW COST, FEED POWDERS FOR THE PRODUCTION OF ZIRCONIA CERAMICS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

TECHNICAL UNIVERSITY OF DENMARK
Address
Anker Engelundsvej 1, Building 101
2800 Lyngby
Denmark

Participants (3)

AS Carl Nielsen
Denmark
Address
4,Islands Brygge
2300 København S
UNIVERSITY OF LEEDS
United Kingdom
Address
Woodhouse Lane
LS2 9JT Leeds
Ålborg Portland A/S
Denmark
Address
44,Rørdalsvej
9100 Ålborg