Method for thermal treatment of a ceramic part by microwaves

Patent metadata

Field	Value
Publication number	US-11713280-B2
Application number	US-201716345664-A
Country	US
Kind code	B2
Filing date	Oct 20, 2017
Priority date	Oct 28, 2016
Publication date	Aug 1, 2023
Grant date	Aug 1, 2023

Abstract

A field of thermal treatment of ceramic materials is provided, and relates to a method for thermal treatment of a solid ceramic part in a microwave cavity, the direction of the electrical field E being substantially uniform in an empty cavity, comprising the steps that consist of placing, in the cavity, at least one ceramic part surrounded by at least one first susceptor with dimensions, material and arrangement configured to emit infrared radiation, each first susceptor including at least one first main surface, each first main surface being an adjusted surface in which the cone distances are parallel to the electrical field E, and of emitting the microwaves into the cavity.

First claim

The invention claimed is:

1. A process for heat treating two solid parts made of ceramic material in a microwave cavity, the microwave cavity being formed by a chamber having a geometry which is suitable for resonance in a single mode of an electromagnetic field defining at least one local extremum of an electric field E or a magnetic field in the microwave cavity, at a frequency vo comprised between 900 MHz and 1 GHz, the direction of the electric field E being substantially uniform in the microwave cavity when it is empty, the process comprising at least the steps of:
a) placing, in the microwave cavity, two solid parts made of ceramic material suitable for absorbing microwaves at the frequency vo and at a temperature T higher than or equal to 700° C., at the at least one local extremum of the electric field E or the magnetic field, the two solid parts being surrounded by at least one first susceptor having first dimensions, wherein the first dimensions, a material of the at least one first susceptor, and an arrangement of the at least one first susceptor are configured so that infrared radiation is emitted directly toward a at least one of the two solid parts during an interaction with the microwaves, the at least one first susceptor comprising at least one first main surface, the at least one first main surface being a ruled surface having generatrices which are parallel to the electric field E in the microwave cavity when it is empty.
b) emitting the microwaves at the frequency vo into the microwave cavity and brazing the two solid parts.

2. The process as claimed in claim 1 , wherein the two solid parts are initially porous and wherein the two solid parts are densified by heating in step b).

3. The process as claimed in claim 1 , wherein at least one element chosen from a ridge and an apex of the at least one first susceptor is rounded.

4. The process as claimed in claim 1 , wherein the at least one first susceptor is made of silicon carbide.

5. The process as claimed in claim 1 , wherein the ceramic material comprises at least one of alumina and zirconia.

6. The process as claimed in claim 1 , wherein the two solid parts are densified so as to comprise at least 90% ceramic material per unit volume.

7. The process as claimed in claim 1 , further comprising a step of placing the at least one first susceptor and the two solid parts in a first thermal confinement.

8. The process as claimed in claim 7 , wherein the first thermal confinement is surrounded by at least one second susceptor having second dimensions.

9. The process as claimed in claim 8 , wherein surrounding the first thermal confinement by the at least one second susceptor forms a second volume bounded by said one or more the at least one second susceptor, wherein the second dimensions, a material of the at least one second susceptor, and an arrangement of the at least one second susceptor are configured so that infrared radiation is emitted during an interaction with the microwaves.

10. The process as claimed in claims 8 , wherein the at least one second susceptor and the first thermal confinement are arranged in a second thermal confinement.

11. The process as claimed in claim 8 , wherein the at least one second susceptor comprises at least one second main surface, the at least one second main surface being a ruled surface having generatrices which are parallel to the electric field E in the microwave cavity when it is empty.

12. The process as claimed in claim 8 , wherein at least one element chosen from a ridge and an apex of the at least one second susceptor is rounded.

13. The process as claimed in claim 1 , wherein the material of the at least one first susceptor comprises at least one of a refractory and semiconductor oxide of a transition metal, and a carbide.

14. The process as claimed in claim 1 , wherein the material of the at least one first susceptor comprises at least one of silicon carbide and lanthanum chromite.

15. The process as claimed in claim 1 , wherein the ceramic material comprises a plurality of different ceramic phases and wherein the first dimensions, the material of the at least one first susceptor, and the arrangement of the at least one first susceptor are configured to selectively heat treat at least one of the plurality of different ceramic phases of each of the two solids parts.

16. The process as claimed in claim 1 , wherein a maximum size D of the two solid parts is chosen so that a ratio between a penetration depth of the microwaves into the two solid parts and D is between 0.5 and 10.

Assignees

• Centre Nat Rech Scient
• Univ Caen
• Ecole Nat Superieure Dingenieurs Caen
• Univ Polytechnique Hauts De France
• Association Pour La Rech Et Le Developpement De Methodes Et Processus Industriels Armines

Inventors

• Marinel Sylvain
• Savary Etienne
• Lefevre François-Xavier
• Lecourt Jérôme
• Saunier Sébastien
• Chanin-Lambert Pauline

Classifications

• C04B35/64 Primary

  Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F}) · CPC title

• C04B35/10 Primary

  based on aluminium oxide · CPC title

• C04B35/48

  based on zirconium or hafnium oxides, zirconates, {zircon} or hafnates · CPC title

• H05B6/6491

  combined with the use of susceptors (H05B6/80 and subgroups takes precedence) · CPC title

• H05B6/80

  Apparatus for specific applications (stoves or ranges F24C7/02) · CPC title