Method of making a three-dimensional fiber structure of refractory fibers
View Patent ↗Carbon nanotubes are incorporated in the fiber structure by growing them on the refractory fibers of the substrate so as to obtain a three-dimensional substrate made of refractory fibers and enriched in carbon nanotubes. The substrate is densified with a matrix to form a part of composite material such as a friction part of C/C composite material.
1. A method of making a porous three-dimensional fiber structure comprising a coherent three-dimensional substrate of refractory fibers, wherein carbon nanotubes are incorporated in the fiber structure by being grown on the refractory fibers of the substrate, after impregnation by a composition comprising at least one catalyst for carbon nanotube growth, so as to obtain a three-dimensional structure made of refractory fibers and enriched in carbon nanotubes.
2. A method according to claim 1 , comprising the successive steps of:
impregnating two-dimensional plies of refractory fibers with a composition containing at least one catalyst for carbon nanotube growth;
forming a three-dimensional substrate by superposing arid bonding together a plurality of impregnated two-dimensional plies; and
causing carbon nanotubes to grow within the three-dimensional substrate.
3. A method according to claim 2 , wherein the two-dimensional plies are bonded together by needling.
4. A method according to claim 1 , comprising the successive steps of:
a) impregnating refractory fiber two-dimensional plies with a composition containing at least one catalyst for carbon nanotube growth;
b) causing carbon nanotubes to grow within the two-dimensional plies; and
c) forming the three-dimensional fiber structure by superposing and bonding together two-dimensional plies of refractory fibers in which at least some of the plies contain carbon nanotubes obtained by steps a) and b).
5. A method according to claim 4 , wherein the three-dimensional fiber structure is formed by stacking two-dimensional plies having varying quantities of carbon nanotubes.
6. A method according to claim 4 , wherein the two-dimensional plies are bonded together by needling.
7. A method according to claim 6 , wherein a layer of free fibers is deposited on each of at least some of the two-dimensional plies, prior to needling.
8. A method according to claim 6 , wherein the two-dimensional plies with carbon nanotubes are moistened prior to needling.
9. A method according to claim 1 , comprising the successive steps of:
making a three-dimensional substrate of refractory fibers;
subsequently impregnating the substrate with a composition containing at least one catalyst for carbon nanotube growth; and
causing carbon nanotubes to grow within the three-dimensional substrate.
10. A method according to claim 9 , wherein making the three-dimensional substrate includes superposing arid bonding together two-dimensional plies.
11. A method according to claim 10 , wherein the three-dimensional plies are bonded together by needling.
12. A method according to claim 9 , wherein the three-dimensional substrate of refractory fibers is made by three-dimensional weaving, knitting, or braiding.
13. A method according to claim 2 , wherein impregnation is performed using a composition containing at least one catalyst for carbon nanotube growth on refractory fibers having a specific surface area of not less than 10 m 2 .g.
14. A method according to claim 2 , wherein a surface treatment is performed on the refractory fibers in order to impart a specific surface area thereon of not less than 10 m 2 .g.
15. A method according to claim 14 , wherein the surface treatment is performed by controlled oxidation.
16. A method according to claim 14 , wherein the surface treatment is performed by acid attack.
17. A method according to claim 14 , wherein the surface treatment of the refractory fibers is performed prior to impregnation with a composition containing at least one catalyst for carbon nanotube growth.
18. A method according to claim 14 , wherein, the surface treatment of the refractory fibers is performed after impregnation with a composition containing at least one catalyst for carbon nanotube growth.
19. A method according to claim 2 , wherein impregnation is performed with a composition containing a solution of at least one salt of a metal constituting a catalyst for carbon nanotube growth.
20. A method according to claim 19 , further including a step of eliminating particles of metal catalyst after the carbon nanotube enriched three-dimensional structure has been made.
21. A method according to claim 1 , wherein additional carbon nanotubes are introduced into the pores of at least one surface portion of the fiber structure.
22. A method according to claim 21 , wherein additional carbon nanotubes are introduced by bringing a suspension of carbon nanotubes in a liquid to the surface of the fiber structure.