SBIR-STTR Award

Conductively linking compact accelerator systems with advanced cryocoolers though high-performance thermal straps would eliminate the requirements for liquid cryogens, and thus facilitate rapid attainment of operational temperatures. However, the sluggish conduction cooling rate of traditional thermal straps made from copper, aluminum, or graphite hinders the practical applications of thermal straps to compact accelerators and superconducting radio frequency technologies. If the thermal and mechanical properties of thermal straps could be improved, this would effectively balance the device heat dissipation with the cryocooler capacity, and reduce the conduction cooling time, enabling faster operation. The proposed project aims to develop a scalable manufacturing approach for producing graphene-copper hybrid foil based thermal straps for connecting superconducting radio frequency cavities or other related devices with cryocooler to reduce cooldown time. The proposed program utilizes the intrinsic physiochemical, thermal and mechanical properties of graphene and copper matrix, combined with advanced electro-codeposition techniques for hybrid strap fabrication. The proposed technology can tailor graphene-copper hybrid properties as needed for tuned operational performance, making the hybrid material an ideal thermal strap for fast conduction cooling processes. Furthermore, the process is inherently low- cost, robust and scalable, making it suitable for industrialization. Phase I will build an electro-codeposition apparatus and investigate the parameters of a pulse/pulse reverse electro-codeposition process for fabricating graphene-copper hybrid foils for thermal straps. The thermal and mechanical properties of the copper-graphene hybrid foils will be evaluated through characterization of thermal conductivity, thermal cycling, and mechanical stiffness. A preliminary economic/scale-up analysis will provide high-level metrics for the potential industrial-scale viability of the proposed process. Other than the applications for compact accelerator systems for high energy physics experiments, the copper-graphene hybrid material technology will be of interest to agencies with advanced thermal management needs via a conduction cooling process, including NASA and Air Force. Furthermore, the proposed technology is anticipated to attract interest from the very large market for medical electronics, which mostly use conduction cooling technology for heat transfer.

Statement of problem or situation being addressed: The sluggish conduction cooling rate of conventional thermal straps made from copper, aluminum, or graphite hinders the application of thermal straps to compact accelerators and superconducting radio frequency technologies. Advanced materials with high performance properties hold the key for thermal straps, effectively balancing device heat dissipation with cryocooler capacity, and reducing conduction cooling time, enabling faster operation. Space platforms and high-power electronic systems require next-generation high thermal and electrical conductivity materials for fast conduction cooling and/or low resistance electrical pathways.Statement of how problem is being addressed: This project will develop and validate an efficient, scalable, manufacturing-ready approach for production of high-performance graphene-copper hybrid foils/coatings, and demonstrate their application in thermal straps, electronic devices, and space landing systems. This technology utilizes the intrinsic physiochemical, thermal and mechanical properties of graphene and copper matrix, combined with advanced electrodeposition techniques for hybrid material fabrication. This technology can tailor graphene-copper hybrid properties for operational performance, making the hybrid material an ideal thermal strap or coating for fast conduction cooling processes and/or low electrical resistance requirements.What was done in Phase I? Manufacturing processes to fabricate graphene-copper hybrid foils were developed. Fabricated hybrid foils exhibited ~50% sheet resistance reduction and ~50% mechanical strain increase compared to pure copper foils. Thermal conductivity, measured by the stepped-bar method, increased with the incorporation of graphene in the copper matrix, adjusted for surface roughness. Government users and commercial partners were identified.What is planned for Phase II? Phase II will mature and scale the production of graphene-copper hybrid foils with both incorporated and laminate structures. The graphene-copper hybrid foils will be assembled into thermal straps for SRF cavities and cryocoolers. The performance of individual foils and assembled thermal straps will be evaluated. The hybrid foil manufacturing parameters will be customized based on both DOE applications in thermal straps and identified commercial applications in electronics, and space systems. The cost analysis will be refined and a technology transfer plan and business case based on the commercial interests of our partners will be further developed.Commercial Applications and Other

Benefits:
Copper-graphene hybrid materials are of interest to entities with advanced thermal management needs using conduction cooling, including NASA and Air Force. The proposed technology is anticipated to attract interest from markets for high-powered electronics and space landing systems, which use conduction cooling technology for heat transfer or high conductivity backplanes as low resistance electrical pathways.