Process and system for protecting an oxidizable material against oxidation

• US 5,498,760 A
• Filed: 11/02/1993
• Issued: 03/12/1996
• Est. Priority Date: 11/02/1992
• Status: Expired due to Term

• Current Assignee: Aerospatiale Societe Nationale Industrielle
• Original Assignee: Aerospatiale Societe Nationale Industrielle
• Inventors: Rousseau, Gerard, Piketty-Leydier, Laurence, Dorvaux, Jean-Marc
• Primary Examiner(s): BELL, JANYCE A
• Application Number:
  US08/146,988
• Time in Patent Office: 861 Days
• Field of Search: 427/228, 427/399, 427/255.4, 427/255.2, 427/452-454, 427/377, 427/243, 427/244, 427/255.7, 427/255, 118/715
• US Class Current: 427/452
• CPC Class Codes: B64C 1/38 Constructions adapted to reduce effects of aerodynamic or other external heating
• CPC Class Codes: B64G 1/226 Special coatings for spacecraft
• CPC Class Codes: B64G 1/58 Thermal protection, e.g. heat shields
• CPC Class Codes: C04B 35/806 The matrix of the ceramic products consisting of non-oxides only
• CPC Class Codes: C04B 35/83 Carbon fibres in a carbon matrix
• CPC Class Codes: C04B 41/00 After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone conditioning of the materials prior to shaping C04B40/00; applying liquids or other fluent materials to surfaces, in general B05; grinding or polishing B24; apparatus or processes for treating or working shaped articles of clay or other ceramic compositions, slag or mixtures containing cementitious material B28B11/00; working stone or stone-like materials B28D; glazes, other than cold glazes, C03C8/00; etching, surface-brightening or pickling compositions C09K13/00
• CPC Class Codes: C04B 41/009 characterised by the material treated
• CPC Class Codes: C04B 41/4527 Plasma spraying deposition from the gas phase using plasma C04B41/4533
• CPC Class Codes: C04B 41/4554 the coating or impregnating material being an organic or organo-metallic precursor of an inorganic material
• CPC Class Codes: C04B 41/4556 coating or impregnating with a product reacting with the substrate, e.g. generating a metal coating by surface reduction of a ceramic substrate
• CPC Class Codes: C04B 41/4582 Porous coatings, e.g. coating containing porous fillers
• CPC Class Codes: C04B 41/5031 Alumina
• CPC Class Codes: C04B 41/5059 Silicon carbide
• CPC Class Codes: C04B 41/5066 Silicon nitride
• CPC Class Codes: C04B 41/52 Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
• CPC Class Codes: C04B 41/524 Multiple coatings, comprising a coating layer of the same material as a previous coating layer
• CPC Class Codes: C04B 41/89 for obtaining at least two superposed coatings having different compositions

Abstract

Process and system for protecting an oxidizable material against oxidation.

The process according to the invention consists of forming a gas-permeable body (1) having open pores (28), a first surface (2) intended to come into contact with an oxidizing gaseous flow (4) liable to oxidize the body and a second surface (6) opposite to the first surface and injecting an oxygen-free protective gas (8) through the second surface (6) leading to disturbances in the material giving it a protection against oxidation.

Claims

1. Process for the protection against oxidation of an oxidizable material having open pores making it permeable to gases and having a first surface intended to come into contact with an oxidizing gaseous flow able to oxidize it and a second surface opposite to the first, characterized in that it consists of injecting by means of an injection system an oxygen-free protective gas through said second surface, said protective gas being able to limit the access of the oxygen to the interior of the pores of the material and block the active sites of said material.

2. Process according to claim 1, characterized in that the protective gas is injected at a speed enabling it to oppose the oxidizing gaseous flow.

3. Process according to claim 1 characterized in that the protective gas is chosen from among nitrogen, rare gases and chlorine.

4. Process according to claim 1, characterized in that the gas-permeable material is essentially made from carbon or carbon doped with silicon carbide.

5. Process according to claim 1, characterized in that the gas-permeable material comprises a fibrous reinforcement embedded in a matrix which essentially made from carbon or carbon doped with silicon carbide.

6. Process according to claim 5, characterized in that the reinforcement is made from carbon.

7. Process according to claim 1, characterized in that on the first surface is formed a gas-permeable outer coating made from a ceramic material differing from a glass and which also contributes to the oxygen protection of the material.

8. Process according to claim 7, characterized in that the outer coating is obtained by plasma spraying Al₂ O₃.

9. Process according to claim 7, characterized in that the outer coating is of silicon nitride or alpha alumina.

10. Process according to claim 9, characterized in that the outer coating is obtained by nitriding a silicon foam deposited on the permeable body.

11. Process according to claim 10, characterized in that nitriding is carried out under nitrogen.

12. Process according to claim 10, characterized In that the silicon foam is formed by ultrasonic dispersing of silicon powder in an aqueous solution and by maintaining the pH of the aqueous solution between 10 and 12, said foam then being deposited on the permeable body and nitrated to form the outer coating (30).

13. Process according to claim 12, characterized in that the aqueous solution contains a dispersing agent.

14. Process according to claim 9, characterized in that the outer coating is obtained by the pyrolysis of a nitrogen and silicon-containing polymer deposited on the permeable body.

15. Process according to claim 14, characterized in that pyrolysis is performed in the presence of silicon nitride powder.

16. Process according to claim 14 characterized in that the nitrogen and silicon-containing polymer is a polymethyl silazane.

17. Process according to claim 9, characterized in that the outer coating is obtained by depositing an alumina sol on the permeable body and then heat treating said alumina sol.

18. Process according to claim 17, characterized in that the alumina sol is a boehmite sol.

19. Process according to claim 7, characterized in that between the outer coating and the gas-permeable material is placed an gas permeable attachment layer to improve the fixation of the outer coating on the oxidizable body said attachment layer being chemically inert with respect to said body and said outer coating.

20. Process according to claim 18, characterized in that the attachment layer is of gas-permeable silicon carbide.