Methods of forming ceramic matrix composites using sacrificial fibers and related products
Methods for preparing ceramic matrix composites using melt infiltration and chemical vapor infiltration are provided as well as the resulting ceramic matrix composites. The methods and products include the incorporation of sacrificial fibers to provide improved infiltration of the fluid infiltrant. The sacrificial fibers are removed, such as decomposed during pyrolysis, resulting in the formation of regular and elongate channels throughout the ceramic matrix composite. Infiltration of the fluid infiltrant can then take place using the elongate channels resulting in improved density and an improved ceramic matrix composite product.
1. A method of forming a ceramic matrix composite (CMC) product comprising:
forming a CMC preform comprising a slurry, the slurry comprising ceramic reinforcing fibers and sacrificial fibers;
removing the sacrificial fibers such that elongate channels are formed throughout the CMC preform;
applying a fluid infiltrant to the CMC preform thereby densifying the CMC preform and forming the CMC product; and
forming infiltrant veins in the CMC product, the infiltrant veins comprising unreacted infiltrant, wherein the unreacted infiltrant comprises free silicon and the free silicon is from about 0.1% by volume to about 10% by volume of the CMC product.
2. The method according to claim 1 , wherein the fluid infiltrant comprises silicon or silicon alloy.
3. The method according to claim 1 , wherein the fluid infiltrant comprises methyltrichlorosilane.
4. The method according to claim 1 , wherein removing the sacrificial fibers comprises:
heating the CMC preform to decompose the sacrificial fibers, wherein the sacrificial fibers are formed of material with a decomposition temperature of about 200° C. to about 650° C.
5. The method according to claim 1 , wherein the sacrificial fibers comprise a semi-crystalline polymer, a cross-linked polymer, an amorphous polymer, or combinations thereof.
6. The method according to claim 1 , wherein the sacrificial fibers comprise one or more of crosslinked phenolic resin, crosslinked poly(vinyl butyral), polyamides, polyesters, and combinations thereof.
7. The method according to claim 1 , wherein the reinforcing fibers comprise one or more of carbon, silicon carbide, silicon nitride, silicon oxycarbides, silicon oxynitrides, silicides, aluminum oxide, silicon dioxide, yttrium aluminum garnet, aluminosilicates, zirconium carbide, hafnium carbide, carbon, SiNC, SiBNC, and boron carbide.
8. The method according to claim 1 , wherein the CMC product comprises a ceramic matrix that comprises one or more of silicon carbide, silicon nitride, silicon oxycarbides, silicon oxynitrides, silicides, aluminum oxide, silicon dioxide, yttrium aluminum garnet, aluminosilicates, zirconium carbide, hafnium carbide, carbon, and boron carbide.
9. The method according to claim 1 , wherein forming the CMC preform comprises forming the sacrificial fibers in a woven pattern.
10. The method according to claim 1 , wherein forming the CMC preform comprises forming the sacrificial fibers in a parallel direction to adjacent sacrificial fibers within a ply.
11. The method according to claim 1 , wherein sacrificial fibers are about 0.1% to about 15% by volume of the CMC preform, and wherein the sacrificial fibers have an average diameter of about 10 μm to about 500 μm.
12. The method according to claim 1 , wherein the sacrificial fibers have an aspect ratio of about 10 to about 10,000.
13. The method according to claim 1 , wherein the sacrificial fibers are continuous along a length or width of the CMC preform.
14. The method according to claim 1 , wherein applying the infiltrant to the CMC preform comprises applying a melt infiltrant to fill the elongate channels throughout the CMC preform.
15. The method according to claim 1 , wherein applying the infiltrant to the CMC preform comprises applying a chemical vapor infiltrant to fill the elongate channels throughout the CMC preform.
16. The method according to claim 1 , wherein the reinforcing fibers have a diameter from about 5 μm to about 20 μm.
17. The method according to claim 1 , wherein the reinforcing fibers have a diameter from about 125 μm to about 175 μm.
18. The method according to claim 1 ,
wherein removing the sacrificial fibers is done in an oxidizing, reducing, inert, or vacuum atmosphere.
19. A method of forming a ceramic matrix composite (CMC) product comprising:
forming a CMC preform comprising a slurry, the slurry comprising ceramic reinforcing fibers and sacrificial fibers, wherein the reinforcing fibers have a diameter from about 125 μm to about 175 μm;
removing the sacrificial fibers such that elongate channels are formed throughout the CMC preform;
applying a fluid infiltrant to the CMC preform thereby densifying the CMC preform and forming the CMC product; and
forming infiltrant veins in the CMC product, the infiltrant veins comprising unreacted infiltrant, wherein the unreacted infiltrant comprises free silicon and the free silicon is from about 0.1% by volume to about 10% by volume of the CMC product.