Methods for electropolishing and coating aluminum on air and/or moisture sensitive substrates

Patent metadata

Field	Value
Publication number	US-12129551-B2
Application number	US-202217895148-A
Country	US
Kind code	B2
Filing date	Aug 25, 2022
Priority date	Sep 17, 2019
Publication date	Oct 29, 2024
Grant date	Oct 29, 2024

Abstract

Methods for electropolishing and coating aluminum on a surface of an air and/or moisture sensitive substrate, including: in a vessel, submerging the substrate in a first molten salt bath and applying an anodizing current to the substrate at a first temperature to electropolish the surface of the substrate; wherein the first molten salt bath includes one of a first organic salt bath and first inorganic salt bath; wherein, when used, the first organic salt bath includes one of (a) aluminum halide and ionic liquid, (b) a combination of an aluminum halide and halogenatedmethylphenylsulfone (C 6 (H 5-y , X y )SO 2 CX 3 , where y is a number from 0-5), (c) a combination of an aluminum halide, an ionic liquid, and halogenatedmethylphenylsulfone (C 6 (H 5-y , X y )SO 2 CX 3 ), and (d) AlF 3 -organofluoride-hydrofluoric acid adduct; wherein, when used, the first inorganic salt bath includes aluminum halide and alkali metal halide; and wherein the anodizing current is 10-30 mA/cm 2 .

First claim

What is claimed is:

1. A method for electropolishing a surface of an air and/or moisture sensitive substrate, the method comprising:
in a vessel, submerging the substrate in a first molten salt bath at a first temperature and applying an anodic current to the substrate to electropolish the surface of the substrate;
wherein the first molten salt bath comprises a first inorganic salt bath;
wherein, when used, the first inorganic salt bath comprises aluminum halide and alkali metal halide; and wherein, when used, the first inorganic salt bath comprises 76-100 wt % AlI 3 , 0-15 wt % NaI, and 0-9 wt % KI at a first temperature of 110-250 degrees C.; and
wherein the anodic current density is 10-30 mA/cm 2 applied using one of a reverse bias from a power supply coupled to the first molten salt bath and by swapping working and auxiliary electrode leads coupled to the first molten salt bath.

2. A method for electropolishing a surface of an air and/or moisture sensitive substrate, the method comprising:
in a vessel, submerging the substrate in a first molten salt bath at a first temperature and applying an anodic current to the substrate to electropolish the surface of the substrate;
wherein the first molten salt bath comprises a first inorganic salt bath;
wherein, when used, the first inorganic salt bath comprises aluminum halide and alkali metal halide; and wherein, when used, the first inorganic salt bath comprises 82 wt % AlCl 3 , 11 wt % NaCl, and 7 wt % KCl; and
wherein the anodic current density is 10-30 mA/cm 2 applied using one of a reverse bias from a power supply coupled to the first molten salt bath and by swapping working and auxiliary electrode leads coupled to the first molten salt bath.

3. The method of claim 1 , further comprising, subsequent to electropolishing the surface of the substrate, coating the electropolished surface of the substrate with aluminum.

4. The method of claim 3 , wherein coating the electropolished surface of the substrate with aluminum comprises:
discontinuing the anodic current and allowing the electropolished substrate to dwell in the first molten salt bath such that the electropolished surface of the substrate is coated with aluminum.

5. The method of claim 3 , wherein coating the electropolished surface of the substrate with aluminum comprises:
one or more of heating the first molten salt bath and evaporating the first molten salt bath under vacuum to remove the first molten salt bath from the vessel, physically pumping the first molten salt bath from the vessel, and draining the first molten salt bath from the vessel; and
in the vessel, submerging the electropolished substrate in a second molten salt bath at a second temperature such that the electropolished surface of the substrate is coated with aluminum;
wherein the second molten salt bath comprises one of a second organic salt bath and second inorganic salt bath;
wherein, when used, the second organic salt bath comprises one of (a) aluminum halide and ionic liquid (e.g., trihexyltetradecylphosphonium chloride (P((CH 2 ) 5 CH 3 ) 3 (CH 2 ) 13 CH 3 Cl)), (b) a combination of an aluminum halide and halogenatedmethylphenylsulfone (C 6 (H 5-y ,X y )SO 2 CX 3 , where y is a number from 0-5), (c) a combination of an aluminum halide, an ionic liquid (e.g., trihexyltetradecylphosphonium chloride (P((CH 2 ) 5 CH 3 ) 3 (CH 2 ) 13 CH 3 Cl)), and halogenatedmethylphenylsulfone (C 6 (H 5-y ,X y )SO 2 CX 3 , where y is a number from 0-5), and (d) AlF 3 -organofluoride-hydrofluoric acid adduct; and
wherein, when used, the second inorganic salt bath comprises aluminum halide and alkali metal halide.

6. The method of claim 5 , wherein, the halogenatedmethylphenylsulfone comprises fluorinatedmethylphenylsulfone (C 6 (H 5-y ,F y )SO 2 CF 3 ).

7. The method of claim 5 , further comprising purging the vessel with an inert gas after the first molten salt bath is removed from the vessel.

8. The method of claim 5 , wherein the second temperature is below a flash point of the second organic salt bath, when used, and 95-250 degrees C. for the second inorganic salt bath, when used.

9. The method of claim 5 , wherein the second inorganic salt bath comprises 68-100 wt % AlCl 3 , 0-19 wt % NaCl, and 0-13 wt % KCl.

10. The method of claim 3 , wherein coating the electropolished surface of the substrate with aluminum further comprises:
applying a reducing current to the electropolished substrate to coat the surface of the electropolished substrate with aluminum derived from the first molten salt bath.

11. The method of claim 10 , wherein the reducing current is no more than 7 mA/cm 2 , is alternating-current frequency modulated, and is applied using a working electrode coupled to the first molten salt bath.

12. The method of claim 5 , wherein coating the electropolished surface of the substrate with aluminum further comprises:
applying a reducing current to the electropolished substrate to coat the surface of the electropolished substrate with aluminum derived from the second molten salt bath.

13. The method of claim 12 , wherein the reducing current is no more than 7 mA/cm 2 , is alternating-current frequency modulated, and is applied in the second molten salt bath.

14. The method of claim 5 , further comprising adding a transition metal halide to the second molten salt bath to cause an aluminum alloy to be coated on the surface of the electropolished substrate.

15. The method of claim 14 , wherein the transition metal halide comprises one or more of Mn, Cr, and Ni.

16. The method of claim 3 , further comprising annealing a resulting aluminum coating.

17. The method of claim 3 , wherein coating the electropolished surface of the substrate with aluminum comprises:
in the vessel, submerging the substrate in a molten pool of aluminum to coat the surface of the substrate with aluminum or the surface of an aluminum-coated substrate with additional aluminum.

18. A method for coating aluminum on a surface of an air and/or moisture sensitive substrate, the method comprising:
in a vessel, submerging the substrate in a molten salt bath with a temperature of 95 degrees C. to 250 degrees C., wherein the molten salt bath comprises an inorganic salt bath comprising 76-100 wt % AlI 3 , 0-15 wt % NaI, and 0-9 wt % KI;
applying an anodic current to the substrate to electropolish the surface of the substrate; and
coating the electropolished surface of the substrate with aluminum by one of submerging the substrate in a molten pool of aluminum, discontinuing the anodic current and allowing the electropolished substrate to dwell in the molten salt bath at a temperature of 95 degrees C. to 250 degrees C. such that the electropolished surface of the substrate is electrolessly coated with aluminum, and applying a reducing current to the electropolished substrate to electroplate the surface of the electropolished substrate with aluminum derived from the molten salt bath, wherein the reducing current is no more than 7 mA/cm 2 ;
wherein the molten salt bath comprises aluminum halide and alkali metal halide.

19. The method of claim 18 , wherein the substrate comprises one or more of zirconium, hafnium, thorium, uranium, plutonium, manganese, a rare earth metal (La—Lu), yttrium, magnesium, lithium, and their alloys.

20. The method of claim 18 , wherein the vessel is sealed and contains an inert cover gas.

21. The method of claim 18 , wherein the substrate electrolessly coated with aluminum is submerged in a molten pool of aluminum.

Assignees

• Cons Nuclear Security Llc

Inventors

• Freiderich John W
• Boyd Tasha L

Classifications

• C25F3/28

  of actinides · CPC title

• C25F3/22

  of heavy metals · CPC title

• C25D3/665

  from ionic liquids · CPC title

• C25F3/26

  of refractory metals · CPC title

• C23C18/31

  Coating with metals · CPC title