Spark plasma sintering methods for fabricating dense graphite
Various embodiments of the disclosure provide methods using spark plasma sintering (SPS) at moderate temperatures and moderate pressures to fabricate high-density graphite material. The moderate temperatures may be temperatures not exceeding about 1200° C. The moderate pressures may be pressures not exceeding about 300 MPa. The high density exhibited by the resulting, sintered, high-density graphite material may be greater than about 1.75 g/cm 3 (e.g., greater than about 2.0 g/cm 3 ).
1. A method for fabricating a high-density graphite material, the method comprising subject a raw material comprising graphite to an electrical current, a temperature not exceeding 1200° C., and a pressure not exceeding about 300 MPa to sinter the raw material into a high-density graphite material having a carbon content of greater than about 95 atomic percent and exhibiting a density of greater than 2.0 g/cm 3 .
2. The method of claim 1 , further comprising selecting the raw material to comprise the graphite in powder form.
3. The method of claim 1 , further comprising selecting the raw material to comprise graphite in natural flake form.
4. The method of claim 1 , further comprising fabricating the high-density graphite material to define a graphite structure with a greatest outer dimension of at least 5 mm.
5. The method of claim 1 , further comprising fabricating the high-density graphite material to define a graphite structure with a greatest outer dimension of at least 50 mm.
6. The method of claim 1 , further comprising, prior to the subjecting, providing a die defining an opening and inserting the raw material in the opening of the die.
7. The method of claim 1 , further comprising, prior to the subjecting, compacting the raw material.
8. The method of claim 1 , further comprising, before the subjecting:
disposing, within an opening defined in a die, the raw material;
at least partially inserting inserts into the opening, the raw material disposed between opposing surfaces of the inserts; and
axially compressing the raw material between the opposing surfaces of the inserts.
9. The method of claim 8 :
further comprising disposing, within the opening defined in the die, an other structure adjacent the raw material,
wherein at least partially inserting inserts into the opening comprises:
at least partially inserting, into the opening, one of the inserts above the raw material and the other structure; and
at least partially inserting, into the opening, an other of the inserts below the raw material and the other structure, and
wherein axially compressing the raw material comprises axially compressing the raw material and the other structure between the opposing surfaces of the inserts.
10. The method of claim 9 , further comprising, prior to disposing the other structure adjacent the raw material, providing the other structure to comprise a sintered material.
11. The method of claim 9 , wherein disposing, within the opening defined in the die, the other structure adjacent the raw material comprises disposing the other structure and the raw material to be wholly received within the opening in the die.
12. The method of claim 1 :
further comprising, before the subjecting:
disposing, within an opening defined in a die, the raw material between opposing surfaces of two structures, the opposing surfaces received within the opening; and
axially compressing the raw material between the opposing surfaces of the two structures,
wherein subjecting the raw material comprising graphite to the electrical current, the temperature not exceeding 1200° C., and the pressure not exceeding about 300 MPa sinters the raw material into the high-density graphite material to bond the two structures via the high-density graphite material.
13. The method of claim 1 , further comprising selecting the raw material to comprise graphite and at least one metal material.
14. The method of claim 13 , further comprising selecting the at least one metal material to comprise one or more of zirconium (Zr), nickel (Ni), iron (Fe), or chromium (Cr).
15. The method of claim 1 , further comprising providing the raw material to comprise the graphite and at least one oxide material.
16. The method of claim 15 , further comprising selecting the at least one oxide material to comprise at least one of uranium or plutonium.
17. The method of claim 1 , wherein subjecting a raw material comprising graphite to an electrical current comprises subjecting the raw material to an electric current of from about 500 amperes to about 10,000 amperes.
18. The method of claim 1 , wherein subjecting a raw material comprising graphite to an electrical current comprises subjecting the raw material to an applied electrical field of from about 4 V/cm to about 20 V/cm.