Extruded Ceramic Nanofibers and Derived Materials

Patent metadata

Field	Value
Publication number	US-2022306544-A1
Application number	US-202117355841-A
Country	US
Kind code	A1
Filing date	Jun 23, 2021
Priority date	Mar 29, 2021
Publication date	Sep 29, 2022
Grant date	—

Abstract

The present invention relates to gels and processes for making bundles of aligned ceramic nanofibers, ceramic nanostructures made by such processes, and methods of using such ceramic nanostructures. Such process is templated via block copolymer self-assembly but does not require any post processing thermal and/or solvent annealing steps. As a result, such process is significantly more efficient and scalable than other processes that are templated via block copolymer self-assembly. The resulting fibers are aligned according to the direction of deposition, making steps where individual fibers are bundled unnecessary.

First claim

What is claimed is:

1 . A process of making bundles of aligned ceramic fibers, said process comprising pyrolyzing a cured extruded filament under an inert gas, said cured extruded filament being produced by extruding a gel to form an extruded filament and then thermally curing said extruded filament to form a cured extruded filament, said gel comprising, based on total gel weight:
a) from about 11% to about 40%, of a block co-polymer having a weight average molecular weight of from about 53,000 Da to about 77,000 Da, said block co- polymer having Structure 1 below:

wherein the total weight ratio of

in said block co- polymer is from about 1:3 to about 3:1;
b) from about 8% to about 34% of a pre-ceramic polymer having a weight average molecular weight of from about 500 Da to about 100,000 Da, said pre-ceramic polymer comprising units having Structure 2 below:

wherein the weight ratio of the moiety having indice x to the moiety having indice y is from about 10:1 to about 1:100;
c) from about 30% to about 50% of an amphilic solvent, and
d) from about 13% to about 25% of a plasticizer;

with the proviso that the combined weight percentage of said block co-polymer, pre-ceramic polymer, amphilic solvent and plasticizer does not exceed 100%.

2 . The process of claim 1 wherein, based on total gel weight, said gel comprises:
a) from about 11% to about 40% of said block copolymer;
b) from about 8% to about 34% of said preceramic polymer;
c) from about 30% to 50% about of said amphilic solvent; and
d) from about 13% to about 25% of a plasticizer.

3 . The process of claim 2 wherein, based on total gel weight, said gel comprises:
a) from about 22% to about 37% of said block copolymer;
b) from about 15% to about 25% of said preceramic polymer;
c) from about 35% to 46% about of said amphilic solvent; and
d) from about 14% to about 20% of a plasticizer.

4 . The process of claim 3 wherein, based on total gel weight, said gel comprises:
a) from about 25% to about 35% of said block copolymer;
b) from about 19% to about 21% of said preceramic polymer;
c) from about 40% to 45% about of said amphilic solvent; and
d) from about 16% to about 19% of a plasticizer.

5 . The process according to claim 1 wherein said cured extruded filament is produced by extruding a gel at a pressure of from about 500 kPa to about 4000 kPa to form an extruded filament and then thermally curing said extruded filament at a temperature of about 70° C. to about 250° C. to form a cured extruded filament and wherein said cured extruded filament is pyrolyzed at a temperature of about 600° C. to about 900° C.

6 . The process according to claim 2 wherein said gel comprises, based on total gel weight:
a) from about 22% to about 37% of a block co-polymer having a weight average molecular weight of from about 58,000 Da to about 72,000 Da, said block co- polymer having Structure 1 below:

wherein the total weight ratio of

in said block co- polymer is from about 1:2 to about 2:1;
b) from about 15% to about 25% of a pre-ceramic polymer having a weight average molecular weight of from about 1,000 Da to about 25,000 Da, said pre- ceramic polymer comprising units having Structure 2 below:

wherein the weight ratio of the moiety having indice x to the moiety having indice γis from about 1:1 to about 1:50;
c) from about 30% to about 50% of an amphilic solvent that comprises a hydroxyl moiety,
d) from about 14% to about 20% of a plasticizer;

with the proviso that the combined weight percentage of said block co-polymer, pre-ceramic polymer, amphilic solvent and plasticizer does not exceed 100%.

7 . The process according to claim 3 wherein said gel comprises, based on total gel weight:
a) from about 6% to about 10% of a block co-polymer having a weight average molecular weight of from about 61,000 Da to about 67,000 Da, said block co- polymer having Structure 1 below:

wherein the total weight ratio of

in said block co- polymer is about 1:1;
b) from about 25% to about 35% of a pre-ceramic polymer having a weight average molecular weight of from about 2,000 Da to about 15,000 Da, said pre- ceramic polymer comprising units having Structure 2 below:

wherein the weight ratio of the moiety having indice x to the moiety having indice y is about 1:10;
c) from about 35% to about 45%, of an amphilic solvent selected from the group comprising of 2-ethylhexanol, 1-octanol, cyclohexanol and mixtures thereof,
d) from about 16% to about 19% of a plasticizer;

with the proviso that the combined weight percentage of said block co-polymer, pre-ceramic polymer, amphilic solvent and plasticizer does not exceed 100%.

8 . The process according to claim 1 wherein said pre-ceramic polymer is linear or hyper- branched.

9 . The process according to claim 1 wherein said pre-ceramic is hyper-branched, said pre-ceramic polymer comprising units having the following formula:

10 . The process according to claim 1 wherein said plasticizer comprises acetone.

11 . The process according to claim 1 wherein said extrusion process is a 3D printing process.

12 . A fiber bundle comprising aligned ceramic fibers, said ceramic fibers having:
a) an average fiber diameter of from about 620 nm to about 320 nm; and b) an alignment wherein at least 70% of nanofibers are within 25 degrees of the bundle's extruded direction.

13 . A fiber bundle according to claim 12 comprising aligned ceramic fibers, said ceramic fibers having:
a) an average fiber diameter of from about 550 nm to about and 330 nm; and
b) an alignment wherein at least 70% of nanofibers are within 10 degrees of the bundle's extruded direction.

14 . A fiber bundle according to claim 13 comprising aligned ceramic fibers, said ceramic fibers having:
a) an average fiber diameter of from about 360 nm to about 340 nm; and
b) an alignment wherein at least 70% of nanofibers are within 3 degrees of the bundle's extruded direction.

15 . A fiber bundle comprising aligned ceramic fibers according to claim 12 , said ceramic fibers have an alignment wherein at least 90% of nanofibers are within 25 degrees of the bundle's extruded direction.

16 . A fiber bundle comprising aligned ceramic fibers according to claim 15 , said ceramic fibers have an alignment wherein at least 70% of nanofibers are within 10 degrees of the bundle's extruded direction.

17 . A fiber bundle comprising aligned ceramic fibers according to claim 16 , sa

Assignees

• Us Gov Air Force

Inventors

• Dickerson Matthew B
• Bowen John J

Classifications

• C04B2235/6021

  Extrusion moulding · CPC title

• C04B35/62281

  based on silicon carbide (C04B35/571 takes precedence) · CPC title

• C04B2235/483

  Si-containing organic compounds, e.g. silicone resins, (poly)silanes, (poly)siloxanes or (poly)silazanes · CPC title

• C04B35/63424

  Polyacrylates; Polymethacrylates · CPC title

• D01F6/52

  of polymers of unsaturated carboxylic acids or unsaturated esters · CPC title