4/9/2021: The U.S. Navy uses thoriated tungsten wire (W-Th) in their radar equipment. A small piece of W-Th is used inside high power microwave vacuum tubes to amplify radar signals. While W-Th has a good source of electrons and can operate at high temperatures, over time it can decay. One drawback is that making the wire produces hazardous byproducts, which is why the Navy is asking the industry for help. It wants a new material to replace W-Th that offers the same performance parameters yet is made in a more environmentally friendly process.

The Navy has several suggestions. One is improving W-Th wire performance by using additives. The majority of W-Th is tungsten, with 1% thorium oxide by weight. Another solution could be applying alternative wire surface coatings that would need to have a low work function, and be resistant to deformation at 1600°C. The Navy has already tested alloys of cerium and lanthanum with tungsten wire, but it is looking for a new process or alternative materials that can be used in the vacuum tubes, and operate within the same voltage and temperature as the W-Th wire.

Since the diameter of the wire used in the vacuum tubes is small, about 35 AWG, and each tube would only use about an inch of wire. The total length needed would depend on the number of tubes needed. An estimated 15 km of wire would be needed per year, notes Brady Walter, the science and technology contact at the Indiana Innovation Institute (IN3), which is a partner in the project.

The Navy is open to industry proposals. Anyone with expertise on the subject can submit a response, and a security clearance is not needed. The deadline for submissions has been extended to May 15, 2021. IN3 is working with the Naval Surface Warfare Center, Crane Division, on this project. The Navy ultimately decides if a proposal will be accepted, and if so, it will provide the funds. Enquiries about the project and submissions can be sent to This email address is being protected from spambots. You need JavaScript enabled to view it..