a ceramic-based mechanical pump at the georgia institute of technology (atlanta, ga.) operated at a record temperature of 1,400 degrees celsius (1,673 kelvin), demonstrating its ability to transfer high-temperature liquids, such as molten tin, and the potential for new energy conversion and storage systems.

this image shows liquid metal flowing at 1400°c in the lab at georgia tech.
(caleb amy)

according to a report from georgia tech, the research was supported by the advanced research projects agency - energy (arpa-e) and was developed in collaboration with researchers from purdue university (west lafayette, ind.) and stanford university (stanford, calif.).

“the new pump could facilitate high efficiency, low-cost thermal storage, providing a new way to store renewable energy generated by wind and solar power, and facilitate an improved process for generating hydrogen directly from fuels such as methane – without producing carbon dioxide,” the report explained.  

“use of ceramic components, normally considered too brittle for mechanical systems, was made possible by precision machining – and seals made from another high-temperature material: graphite.”

the hotter the temperature, the more thermal energy can be converted to mechanical or electrical energy because entropy declines at higher temperatures. prior attempts at operating at extreme temperatures had softened the material of the pump and the entire infrastructure.

“the researchers used an external gear pump,” according to the article, “which uses rotating gear teeth to suck in the liquid tin and push it out of an outlet. that technology differs from centrifugal and other pump technologies, but [researchers] chose it for its simplicity and ability to operate at relatively low speeds.”

graphite was also used in the design to form the seals in the pump, piping, and joints. normally, flexible polymers would be used in those parts, but the extreme temperatures made them untenable. the pump was also operated in a nitrogen-rich environment to avoid oxidation.

“the pump operated for 72 hours continuously at a few hundred revolutions per minute at an average temperature of 1,473 kelvin – with brief operation up to 1,773 kelvin in other experimental runs,” the article continued. “because the researchers used a relatively soft ceramic known as shapal for ease of machining, the pump sustained wear…other ceramics with greater hardness will overcome that issue, and the team is already working on a new pump made with silicon carbide.”

the research was recently published in nature. the abstract stated:

“heat is fundamental to power generation and many industrial processes, and is most useful at high temperatures because it can be converted more efficiently to other types of energy. however, efficient transportation, storage and conversion of heat at extreme temperatures (more than about 1,300 kelvin) is impractical for many applications.

“liquid metals can be very effective media for transferring heat at high temperatures, but liquid-metal pumping has been limited by the corrosion of metal infrastructures. here we demonstrate a ceramic, mechanical pump that can be used to continuously circulate liquid tin at temperatures of around 1,473–1,673 kelvin.

“our approach to liquid-metal pumping is enabled by the use of ceramics for the mechanical and sealing components, but owing to the brittle nature of ceramics their use requires careful engineering.

“our set-up enables effective heat transfer using a liquid at previously unattainable temperatures, and could be used for thermal storage and transport, electric power production, and chemical or materials processing.”