GLASS-CERAMIC ARTICLE

Abstract

A glass-ceramic article, includes at least one substrate, such as a plate, made of glass-ceramic, the substrate being coated in at least one zone with at least one layer including zirconium silicon nitride, Si.sub.xZr.sub.yN.sub.z, with an atomic ratio of Zr to the sum Si+Zr, y/(x+y), of 10% to 90%.

Claims

1. A glass-ceramic article, comprising at least one substrate made of glass-ceramic, said substrate being coated in at least one zone with at least one layer comprising zirconium silicon nitride, Si.sub.xZr.sub.yN.sub.z, with an atomic ratio of Zr to the sum Si+Zr, y/(x+y), of 10% to 90%.

2. The glass-ceramic article as claimed in claim 1, wherein said layer is a zirconium silicon nitride layer, essentially formed to at least 85% by weight, with the exception of the impurities possibly present which do not represent more than 5% of the layer, of silicon, zirconium and nitrogen.

3. The glass-ceramic article as claimed in claim 1, wherein a thickness of said layer is within a range extending from 200 to 5000 nm.

4. The glass-ceramic article as claimed in claim 1, wherein said layer exhibits a hardness H of greater than 15 GPa and a modulus of elasticity E of greater than 140 GPa.

5. The glass-ceramic article as claimed in claim 1, wherein the coating including said layer contains only a single layer comprising zirconium silicon nitride.

6. The glass-ceramic article as claimed in claim 1, wherein the substrate is coated with at least one layer of enamel and/or of paint on or under said layer comprising zirconium silicon nitride.

7. The glass-ceramic article as claimed in claim 1, wherein said layer is directly in contact with said substrate made of glass-ceramic, without other underlying coating layer.

8. The glass-ceramic article as claimed in claim 1, wherein said layer, or at least one layer incorporating zirconium silicon nitride, constitutes an exterior layer of the coating including it present on the glass-ceramic.

9. The glass-ceramic article as claimed in claim 1, wherein said layer is coated with at least one layer having a coefficient of friction of less than 0.25.

10. The glass-ceramic article as claimed in claim 1, wherein said layer exhibits a nitridation z ranging from 4/3(x+y) to 5/3(x+y).

11. The glass-ceramic article as claimed in claim 1, wherein a content of dopant(s) in a target used, as well as in the layer, or a content of other component(s) in the layer, being less than 15% by weight.

12. The glass-ceramic article as claimed in claim 1, wherein the glass-ceramic article is a cooking device additionally comprising one or more heating elements.

13. A process for the manufacture of an article made of glass-ceramic as claimed in claim 1, said article comprising at least one substrate made of glass-ceramic, in which at least one layer comprising zirconium silicon nitride, Si.sub.xZr.sub.yN.sub.z, with an atomic ratio of Zr to the sum Si+Zr, y/(x+y), of 10% to 90% is deposited on at least one zone of said substrate.

14. The process as claimed in claim 13, wherein said substrate, thus coated, is subjected to a tempering treatment or to an annealing at a temperature of 750° C. to 900° C.

15. The process as claimed in claim 13, wherein the deposition of said layer is carried out by cathode sputtering.

16. The glass-ceramic article as claimed in claim 1, wherein the substrate is a plate.

17. The glass-ceramic article as claimed in claim 1, wherein the atomic ratio of Zr to the sum Si+Zr, y/(x+y) is from 15% to 50%.

18. The glass-ceramic article as claimed in claim 17, wherein the atomic ratio of Zr to the sum Si+Zr, y/(x+y) is 28% to 33%.

19. The glass-ceramic article as claimed in claim 3, wherein the thickness of said layer is within a range extending from 700 to 2500 nm.

20. The glass-ceramic article as claimed in claim 19, wherein the thickness of said layer is within a range extending from 1000 to 1500 nm.

Description

[0050] The following examples illustrate the present invention without limiting it.

[0051] In these examples, small 20 cm by 20 cm plates of the same substrate formed of a translucent black glass-ceramic, sold under the reference KeraBlack+ by Eurokera, were used, these small plates exhibiting a smooth upper face and a lower face provided with pins and a thickness of 4 mm.

[0052] A thick layer, with a thickness of 1200 nm, of Si.sub.xZr.sub.yN.sub.z with an atomic ratio of Zr to the sum Si+Zr, y/(x+y), of 32% was deposited on these small plates by pulsed-DC magnetron-enhanced cathode sputtering at low pressure of the order of 2 μbar, with a power density per unit area of the target of less than 6 W/cm.sup.2 and a nitrogen content of between 55% and 65%.

[0053] The hardness H and the elastic modulus E of the bare glass-ceramic and then of the glass-ceramic provided with the preceding layer were subsequently measured using a nanoindenter of DCMII-400 type, the tip used being a pyramidal diamond tip of Berkovich type (3 sides) according to the standard NF EN ISO 14577.

[0054] It was observed that the bare glass-ceramic has a hardness of 7.5 GPa and that the deposition of a thick layer of zirconium silicon nitride made it possible to increase the hardness up to approximately 14.5 GPa. The modulus of elasticity (or elastic modulus) E of the layer was 140 GPa.

[0055] An annealing (or tempering) at 850° C. for 10 min was subsequently carried out on the coated glass-ceramic, resulting in even higher values of hardness on the coated substrate and of modulus of elasticity E of the layer: H=15.5-20.5 GPa and E=155 GPa.

[0056] The abrasion resistance of these samples was also measured using an abrasive paper of P800 type sold by Norton and incorporating silicon carbide grains with a mean equivalent diameter of 20 μm, by making a paper to-and-fro motion over the surface of the glass-ceramic (bare or coated) over a distance of 3.81 cm at a rate of 15 to-and-fro motions per minute and an applied pressure of 5 N/cm.sup.2. The measurements in terms of number of scratches were made from photos taken by illuminating the samples using 3-color light-emitting diodes in a light box, image processing (binarized in black and white and making it possible to reveal the scratches in black pixels and the unscratched part in white pixels) making it possible to analyze the photographs taken. A “scratchability index” was evaluated giving an index x corresponding to the number y of black pixels recorded on an image composed of 132 000 pixels divided by 10 000 (x=y/10 000, the index x being, for example, 1 when there are 10 000 black pixels, 2 when there are 20 000 black pixels, and the like), the bare glass-ceramic obtaining an index of 4 whereas the coated glass-ceramic in accordance with the invention obtained an index of 2 before annealing heat treatment and of 1 after annealing heat treatment at a temperature of the order of 850° C. for approximately ten minutes, thus showing a considerable reduction in the number of scratches in comparison with a bare glass-ceramic.

[0057] The coefficient of friction was also measured using a CSM microscratch device sold by CSM Instruments. A constant force of 1N was applied to a stainless steel ball with a diameter of 1 cm moving over a distance of 2 cm at constant speed, thirty passes being carried out in all. The coefficient of friction measured was the ratio of the tangential force applied to the normal force applied, which forces are measured by sensors. The coefficient of friction measured for the bare glass-ceramic (glass-ceramic/metal contact) was 0.3 and that for the coated glass-ceramic was lowered to 0.2. By way of comparison, that obtained by using, as coating, in place of the layer according to the invention, a hard coating of the same thickness based on SiN (without zirconium) obtained a higher coefficient, equal to 0.4.

[0058] These same samples were subjected to a metal friction test on a reference 5750 Linear Abraser device (sold by Taber) with a flat stainless steel wiper, the arm carrying the wiper travelling 3.81 cm at a rate of 60 cycles per minute, with an application force of 2 MPa. The test consisted in carrying out to-and-fro motions and in determining the number of cycles from which a metal deposit was observed at the surface, this test making it possible to simulate the movement of a saucepan at the surface of a glass-ceramic, the movements of saucepans generating two types of damage: scratches in the form of metal deposits resulting from the saucepan, and plastic deformation or cracks or abrasions of the glass-ceramic.

[0059] On the bare glass-ceramic, the wiper scratched the surface in less than approximately twenty cycles, just as for samples with only a deposit (of the same thickness as the layer according to the invention tested) of TiO.sub.x or of TiZrO.sub.x, the sample carrying a layer of SiN bringing about metal deposits after approximately thirty cycles.

[0060] The sample according to the invention (provided with the abovementioned layer of SiZrN) was scratched only from approximately sixty cycles, i.e. twice as many cycles as the best of the preceding comparative samples.

[0061] The addition to the abovementioned layer of SiZrN of a layer of TiO.sub.x or TiZrO.sub.x with a thickness of 5 nm, having a coefficient of friction of 0.17 and 0.15 respectively, further made it possible to improve these results, in particular making it possible to go even beyond approximately a hundred cycles.

[0062] Various cleaning tests on surfaces carrying traces of coffee, milk, vinegar, burnt tomato sauce, under cold and hot conditions, with different household products (such as the VitroClen brand products from Reckitt Benckiser or an induction and glass-ceramic cleaning product from Kiraviv) have also demonstrated that the glass-ceramic coated with the layer selected according to the invention was easy to clean and that the layer did not degrade chemically. Likewise, this layer did not delaminate after thermal shocks at 620° C., nor did it show degradation after 100 h at 580° C.

[0063] The articles according to the invention can in particular be used with advantage to produce a novel range of cooktops for kitchen ranges or cooking surfaces or a novel range of work tables, consoles, credenzas, central islands, and the like.