Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Patent
1990-08-28
1992-05-19
Dixon, Jr., William R.
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
501 86, C03C 602, C03C 3062, C03C 400
Patent
active
051148838
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for the manufacture of a vitreous material exhibiting an ox blood-red colour, capable of being especially employed in jewellery.
SUMMARY OF THE INVENTION
The material which is the subject of the present invention comprises a transparent and colourless vitreous matrix composed essentially of lead silicate, containing a large quantity of cuprite (Cu.sub.2 O) crystals which make the material opaque and give it a characteristic ox blood-red colour.
The process for manufacturing the material defined above according to the present invention is characterized in that it comprises the following stages: oxide (PbO) and silica (SiO.sub.2) in such proportions that the ratio of these two components is 65% by weight of lead oxide and 35% by weight of silica, the melting temperature being approximately between 1000.degree. and 1300.degree. C., obtained in the above stage, the quantity of this addition of copper being such that the weight concentration of oxide in the final product is approximately from 6 to 8%, the temperature of the melt bath being maintained between 1000.degree. and 1300.degree. C., approximately 1000.degree. to 1300.degree. C., so as to eliminate bubbles, approximately between 500.degree. and 800.degree. C. for a sufficient time to produce formation and growth of microcrystals of cuprite (Cu.sub.2 O), the formation of residual stresses in this mass.
Siliceous sand and red lead or else a lead silicate sinter can be employed to obtain the basic melt or melt bath during the first stage of the process according to the invention. During this first stage small additions of other components may be provided, such as especially lithium, sodium, potassium, calcium, magnesium, barium, aluminium or phosphorus oxides, and the like, so as to modify the chemical, physical and mechanical properties of the material finally obtained. During the final stage of the heat treatment at a temperature of approximately between 500.degree. and 800.degree. C., the cuprite microcrystals formed during this stage separate from the vitreous material and develop and grow as a function of the temperature and of the residence time. The formation of red crystallites is generally observed in the form of interlaced shoots or branches of variable sizes, of the order of a few microns (preferably approximately two microns) to approximately 2 mm. The longer the residence time at the growth temperature of the crystals, the larger the crystal size. The characteristic bright red colour of the material forming the subject of the present invention is obtained by carrying out the heat treatment of the melt in the temperature range referred to above. With regard to the duration of the treatment, this is a function of the mass of the molten substance treated and of its composition, it being possible for this duration of treatment to vary from a few minutes to several hours. The relative density of the material according to the invention is approximately between 4.0 and 4.5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of a process of manufacture forming the subject of the present invention has been given below by way of example, no limitation being implied.
In order to obtain a vitreous material with a characteristic ox blood-red colour and comprising micro-inclusions of cuprite crystals, this substance having the following composition (as percentage by weight):
______________________________________ PbO 52% SiO.sub.2
28%
Cu.sub.2 O
6% Sb.sub.2 O.sub.3
1%
K.sub.2 O
5% Na.sub.2 O
2.5%
Al.sub.2 O.sub.3
2% CaO 3%
P.sub.2 O.sub.5
0.5%
______________________________________
siliceous sand, of red lead, of potassium carbonate, of sodium felspar, of
sodium phosphate and of calcium carbonate, and this mixture was melted at
a temperature of the order of 1200.degree. C.
After the melting was accomplished, the appropriate quantities of Cu.sub.2 O and of metallic antimony, referred to above, were added, while stirring vigorously so as to obtain
REFERENCES:
patent: 2331052 (1943-10-01), Shadduck
Glass Technology, vol. 22, No. 1, Feb. 1981 (Sheffield, G.B.) A. A. Ahmed et al.: "Effect of Heat Treatment Crystallization of Cuprous Oxide in Glass", pp. 24-33.
Derwent Japanese Patents Report, vol. 74, No. 36, Oct. 10, 1974; pp. L1-L3 reporting on Japanese Patent Publication No. 74032298.
Kagan Jean
Kagan Michel
Kagan Rubin
Verita Livio
Bonner C. Melissa
Dixon Jr. William R.
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