Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
1999-03-16
2001-03-13
Marcantoni, Paul (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S103000
Reexamination Certificate
active
06200916
ABSTRACT:
The invention concerns a manufacturing method for a coloured zirconia based article, in particular such an article having a colour comprised within the range from orange to red/bordeaux and made by sintering. For the sake of convenience such an article will be designated an orange/red article in the following description.
The invention also concerns an orange/red zirconia based decorative article in particular obtained from the above method.
Incorporating dyes or pigments such as cadmium sulphate (CdS), cadmium selenide (CdSe) and cadmium sulphoselenide in ceramic materials to obtain orange/red ceramic articles used, for example, for making enamels, glazes and receptacles for domestic use or floor coverings, is already known.
The use of this type of dye has numerous drawbacks as soon as one wishes to incorporate this type of dye in industrial ceramics, in particular sintered zirconia based materials.
Indeed, these dyes lack stability at high temperatures and only have their colouring properties up to 1,000 or 1,200° C. This greatly limits the use of this type of dye and in particular does not permit the realisation of sintered Zirconia based articles, the sintering temperatures of zirconia being in all cases higher than 1,100° C.
Moreover, the use of these types of dyes, which contain heavy metals, in articles intended to be in contact with the skin of a user, such as a watch case, if not legally prohibited, is at least strongly advised against.
Further, the dyes of this type which are available commercially have a granulometry which is not compatible with obtaining a homogenous mixture with zirconia powder.
A main object of the invention is thus to provide, on the one hand a manufacturing method for an orange/red sintered zirconia based article and on the other hand, such an article obtained in particular according to this method, this article having satisfactory mechanical properties while having an orange/red colouring at least to a depth of 5 mm.
The invention therefore concerns a manufacturing method for an orange/red zirconia based article characterised in that it includes the successive steps of:
forming a first mixture including a zirconia powder, 3 to 20% in weight of a stabilising agent selected from the group of oxides including yttrium oxide, magnesium oxide, cerium oxide and calcium oxide, 0.1% to 5% in weight of powders intended to form a vitreous phase, including silicon oxide, aluminium oxide and yttrium oxide, 0.01% to 10% in weight of a copper oxide powder;
forming a second mixture including said first mixture and a binding agent;
forming a granulated mixture by milling said second mixture;
forming a green body by giving said second granulated mixture the shape of the desired article;
sintering for at least thirty minutes at a temperature comprised between 1,350 and 1,500° C. in ambiant atmosphere, and
annealing the desired article at a temperature comprised between 700° C. and 1,350° C. for a period of time comprised between 30 minutes and 20 hours in an inert or reducing atmosphere having an oxygen partial pressure comprised between 10
−10
and 1 atmosphere, and
polishing said sintered article.
By the incorporation of copper oxide (CuO) powder in the mixture to be sintered, the method of the invention allows a reduction in the sintering temperatures. The copper oxide also acts as one of the determining elements in the orange/red colouring which one wishes to give the article.
Indeed, the colour of the article after the sintering operation in the presence of CuO is green because of an accumulation of CuO in the +2 oxidation state at the grain boundaries. Then during a subsequent step of the method of the invention, called the annealing step, advantage is taken of the presence of CuO (oxidation state +2) to reduce it into Cu
2
O (oxidation state +1) or even to reduce a portion of the Cu
2
O into colloidal copper metal (oxidation state 0). After this annealing step, the article has a colour situated in the range going from orange yellow to red or bordeaux red as a function of the respective quantities of copper at the +2, +1, 0 oxidation states present at the grain boundaries. The colour of the copper oxide (CuO) corresponding to the +2 oxidation state is green, the colour of the copper oxide (Cu
2
O) corresponding to the +1 oxidation state is yellow/orange and the colour of the colloidal copper metal (Cu) is red/bordeaux.
The respective quantities of copper oxides and copper, corresponding to the +2, +1, 0 oxidation states present at the grain boundaries are determined by the annealing conditions, more precisely by causing the oxygen partial pressure to vary within the atmosphere of the furnace where the annealing step take place.
REFERENCES:
patent: 4742030 (1988-05-01), Masaki et al.
patent: 0 218 853 (1987-04-01), None
patent: 0 700 796 A1 (1995-09-01), None
patent: 62-059571 (1987-03-01), None
patent: 06092638 (1994-04-01), None
Lemaire Lionel
Michel Beatrice
Asulab S.A.
Griffin & Szipl, P.C.
Marcantoni Paul
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