Search

US-20260126410-A1 - ROBUST TAPER SEAL MICRO-CHANNEL MEMBRANE FOR A HIGH TEMPERATURE REFERENCE ELECTRODE

US20260126410A1US 20260126410 A1US20260126410 A1US 20260126410A1US-20260126410-A1

Abstract

A micro-channel membrane for use with high-temperature molten salts used with high-temperature reference electrodes (HTREs). The micro-channel membrane includes a ring having an opening with an opening surface and a plug positioned within the opening with a plug surface. The opening surface and the plug surface contact and interface with each other to form a plurality of micro-channels. The opening surface and the plug surface may be tapered. The opening surface and/or the plug surface may have a surface configuration to facilitate formation of the micro-channels, such as a plurality of facets, a helical channel, a roughened surface, a channel pattern, or a knurled surface pattern. One or more tack welds may secure the plug within the ring. A method for making the micro-channel membrane may include measuring a leak rate through the micro-channels and securing the plug when a target leak rate is measured.

Inventors

  • Lee C. Sorensen
  • Thomas A. Meaders
  • James J. Steppan
  • Byron S. Millet

Assignees

  • HIFUNDA, LLC

Dates

Publication Date
20260507
Application Date
20251104

Claims (20)

  1. 1 . A micro-channel membrane for use with high-temperature molten salts used with high-temperature reference electrodes (HTREs) comprising: a ring having an opening, wherein the opening comprises an opening surface; a plug disposed within the opening, wherein the plug comprises a plug surface and wherein the opening surface and the plug surface contact and interface with each other to form a plurality of micro-channels.
  2. 2 . The micro-channel membrane according to claim 1 , wherein the opening surface comprises a tapered opening surface and wherein the plug surface comprises a tapered plug surface.
  3. 3 . The micro-channel membrane according to claim 2 , wherein the tapered plug surface or the tapered opening surface comprises a plurality of facets.
  4. 4 . The micro-channel membrane according to claim 2 , wherein the tapered plug surface or the tapered opening surface comprises a helical channel.
  5. 5 . The micro-channel membrane according to claim 2 , wherein the tapered plug surface or the tapered opening surface comprises a controlled surface finish having a predetermined surface roughness.
  6. 6 . The micro-channel membrane according to claim 2 , wherein the tapered plug surface or the tapered opening surface comprises a channel pattern.
  7. 7 . The micro-channel membrane according to claim 2 , wherein the tapered plug surface or the tapered opening surface comprises a knurled surface pattern.
  8. 8 . The micro-channel membrane according to claim 1 , wherein the micro-channel membrane further comprises one or more tack welds to secure the plug within the ring opening.
  9. 9 . The micro-channel membrane according to claim 8 , wherein the tack welds are positioned to fully or partially close off micro-channels.
  10. 10 . The micro-channel membrane according to claim 8 , wherein the tack welds are porous.
  11. 11 . The micro-channel membrane according to claim 1 , wherein the plurality of micro-channels have a cross-sectional size less than 10 microns.
  12. 12 . The micro-channel membrane according to claim 1 , wherein the micro-channel membrane comprises a gas leak rate in the range from 1×10 −5 atm·cm 3 /min to 0.1 atm·cm 3 /min.
  13. 13 . A method for making a micro-channel membrane for use with high-temperature molten salts used with high-temperature reference electrodes (HTREs) comprising: pressing a plug within a ring, wherein the plug comprises a plug surface and the ring comprises an opening having an opening surface, wherein the opening surface and the plug surface contact and interface with each other to form a plurality of micro-channels; controlling a force and/or distance of pressing the plug within the ring to control a cross-sectional size of the plurality of micro-channels and/or a leak rate through the plurality of micro-channels; and securing the plug within the ring.
  14. 14 . The method for making a micro-channel membrane according to claim 13 , further comprising measuring a leak rate through the plurality of micro-channels and wherein the step of securing the plug occurs when a target leak rate is measured.
  15. 15 . The method for making a micro-channel membrane according to claim 14 , wherein the target leak rate is a gas leak rate in the range from 1×10 −4 atm·cm 3 /min to 5×10 −3 atm·cm 3 /min.
  16. 16 . The method for making a micro-channel membrane according to claim 13 , wherein the opening surface comprises a tapered opening surface and wherein the plug surface comprises a tapered plug surface.
  17. 17 . The method for making a micro-channel membrane according to claim 13 , wherein the step of securing the tapered plug within the tapered ring comprises applying one or more tack welds to secure the tapered plug within the tapered ring.
  18. 18 . The method for making a micro-channel membrane according to claim 16 , wherein the tapered plug surface or the tapered opening surface comprises a plurality of facets.
  19. 19 . The method for making a micro-channel membrane according to claim 16 , wherein the tapered plug surface or the tapered opening surface comprises a helical channel.
  20. 20 . The method for making a micro-channel membrane according to claim 16 , wherein the tapered plug surface or the tapered opening surface comprises a roughened surface.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application No. 63/716,668, filed Nov. 5, 2024, the entire contents of which are incorporated by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Award Number: DE-SC0020579 awarded by the U.S. Department of Energy and titled, Stable High-Temperature Molten Salt Reference Electrodes. The government has certain rights in the invention. BACKGROUND The disclosed invention relates to a micro-channel membrane suitable for use with high-temperature molten salts used with high-temperature reference electrodes (HTREs). A reference electrode must have ionic communication between the reference salt and the test melt through a membrane. A high-temperature reference electrode (HTRE) for molten salt systems must have a membrane that can withstand the high melt temperatures of the salt and is chemically compatible with the reference salt and the molten test salt. Methods of achieving ionic communication through high-temperature membranes are through either ionically conductive ceramics, ionically-conductive salt melts, or micro-sized channels in a membrane that are typically less than 10 microns (0.0004 inch). High rates of mass transfer are not required for ionic communication and not desired as the reference melt will be contaminated with the test melt leading to HTRE voltage drift. Mass transfer is the result of pressure and/or concentration gradients between the reference compartment of the HTRE and the test melt. Pressure-driven mass transfer of the reference salt is minimized by incorporation of a vent in the HTRE for pressure equalization during heating. Diffusion-driven mass transfer is minimized by incorporating the same test melt chemistry, e.g. FLiNaK, in both the reference compartment and the test cell. Mass transfer of reference salt is minimized by the high mass transfer resistance of the microchannels. There is a delicate balance between minimizing mass transfer and still maintaining ionic communication. For example, if the leak rate of the metal membrane is zero, then there is no mass transfer, but no ionic communication and the HTRE won't function. However, if the metal membrane has a very low leak rate and its microchannels are filled with high-temperature molten salts (HTMS), it will have low mass transfer, good ionic communication, and good HTRE performance. Ceramic membranes can easily break and are incompatible with fluoride-based molten salts. Membranes using micro-channels have the advantage that they can be made from metal for improved chemical compatibility and robustness. However, creating microchannels on the order of 1 micron diameter or less is a challenging process. It is possible to use laser drilling to make the channels, but the depth of cut is limited to about 0.005 inches and there are long lead times and limited suppliers with this capability. HTREs built with these thin membranes have failed under pressure during freeze/thaw cycles of the reference salt. Porous metal membranes can also be used, but these have been observed to degrade during freeze/thaw cycles, require pore forming processes that can be complex to get repeatable leak rates, or by compressing metal foam to get the desired leak rate, which can also lead to variability in the leak rates depending on the resulting number of open channels and paths. There is a need in the art for a membrane having micro-channels for use with HTREs which is robust and easily manufactured with a repeatable assembly process. SUMMARY The disclosed invention relates to micro-channel membranes suitable for use with high-temperature molten salts (HTMS) used with high-temperature reference electrodes (HTREs). The disclosed invention further includes a robust and repeatable method of making a micro-channel membrane. The membrane can be much thicker than that of a laser-drilled membrane, thus enabling the membrane to withstand higher pressures and providing more robustness. The membrane is designed for manufacturing and is easy to assemble with a repeatable assembly process. In some disclosed embodiments, a micro-channel membrane for use with high-temperature molten salts used with high-temperature reference electrodes (HTREs) includes a ring having an opening and a plug disposed within the opening. The ring opening defines an opening surface. The plug defines a plug surface. The opening surface and the plug surface contact and interface with each other to form a plurality of micro-channels. The formed micro-channels typically have a cross-sectional size less than 10 microns. In some embodiments the cross-sectional size ranges from about 0.5 micron to 10 microns. In some embodiments the micro-channels have a cross-sectional size of about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 microns, where any of the stated values can form an upper or