Innovative Materials for Microwave Tube Applications
Navy STTR FY2014A - Topic N14A-T010
ONR - Steve Sullivan - steven.sullivan@navy.mil
Opens: March 5, 2014 - Closes: April 9, 2014 6:00am EST

N14A-T010 TITLE: Innovative Materials for Microwave Tube Applications

TECHNOLOGY AREAS: Sensors, Electronics, Battlespace

ACQUISITION PROGRAM: PEO IWS 2, Above Water Sensors

OBJECTIVE: Research and development of high purity metal alternatives for microwave tube (MWT) production that meet or exceed the performance and reliability of existing materials.

DESCRIPTION: The Navy uses microwave tubes (MWT) in both radar and electronic warfare (EW) systems. Throughout the microwave tube industry, high purity metals are increasingly difficult and costly to procure. For example, vacuum-grade high purity copper and copper-nickel alloys such as Monel and cupronickel (ref 1, 2, 3) are highly desirable in MWT manufacturing processes because they are corrosion resistant, often stronger than steel, have a low coefficient of thermal expansion, and can be welded and brazed, both to other metals and to metallized ceramics. However, these alloys are considered "niche" market materials and are therefore expensive and increasingly only available from foreign suppliers

Replacement materials are needed that can significantly stabilize the (domestic) MWT material supply base while improving material and process reliability for improved vacuum integrity, manufacturing yield, corrosion resistance, and thermo-mechanical compatibility, resulting in longer life microwave tubes and hence, decreased life-cycle cost. The main difficulty with many otherwise attractive alloys is the fact that metallic and non-metallic impurities infuse into the material and lead to undesirable consequences such as vacuum degradation and cathode poisoning. In some cases, the coefficient of expansion of the impurity is greatly different than the alloy, thus leading to weakness in the material. The weaknesses are often found during the microwave tube manufacturing process where brazing, welding and heat cycling are commonplace. Impurities often cause virtual leaks to occur where vacuum integrity breaks down and the microwave tube ceases to function properly. Presently, in order to mitigate this risk, microwave tube manufacturers often have to plate the material to seal in the potential weak spot which adds cost and time to the manufacturing process.

Alternatives are sought to improve existing manufacturing techniques for MWT relevant metal alloys and/or to develop new materials suitable to replace existing vacuum-grade materials while maintaining MWT compatible characteristics such as coefficients of expansion, manufacturability and thermal conductivity required by the industry. Innovative materials (or processes such as plating and brazing) are needed which mitigate the niche market supply problems which plague the microwave tube industry. Furthermore, proposed solutions should decrease the dependence on foreign supply and the resulting fluctuations in material cost. The solutions will also lead to significant reductions in life cycle costs.

PHASE I: The company will develop a concept for providing high purity materials for microwave tube applications that meet the requirements described above. The company will demonstrate the feasibility of the concept in meeting Navy needs and will establish that the concept can be feasibly developed into a useful product for the Navy. Feasibility will be established through material testing, and analytical modeling. The small business will provide a Phase II development plan that addresses technical risk reduction and provides performance goals and key technical milestones.

PHASE II: Based on the results of Phase I and the Phase II development plan, the small business will develop prototype materials and processes for evaluation. The prototype will be evaluated to determine its capability in meeting the performance goals defined in Phase II development plan and the Navy requirements for high purity materials for microwave tube applications. Microwave tube compatibility and performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters including thermal stress cycling. Evaluation results will be used to refine the prototype into an initial material/process that will meet Navy requirements. The company will prepare a Phase III development plan to transition the technology to industry for the production of microwave tubes for Navy use.

PHASE III: The company will be expected to support the Navy in transitioning the technology for Navy use. The company will develop innovative materials for microwave tube applications in accordance with the Phase III development plan for evaluation in order to determine suitability of the material(s) in the MWT industry and the effectiveness of microwave tubes incorporating these new materials in an operationally relevant environment. The company will support the Navy for test and validation to certify and qualify the material(s) for Navy use.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Innovative materials developed for Navy MWT application have equal applicability to commercial microwave tubes. Other Government agencies and commercial customers use microwave tubes for a wide variety of radar, telecommunications, medical therapy, food and materials processing application. In addition, various scientific applications (such as plasma fusion and materials research) exist which also rely on microwave tube technology.

REFERENCES:
1. W.Schleich, "APPLICATION OF COPPER-NICKEL ALLOY UNS C70600 FOR SEAWATER SERVICE", KM Europa Metal AG, Klosterstr. 29, 49074 Osnabrück Germany. (Also found at <http://www.copper.org/applications/cuni/pdf/NACE_05222_05.pdf.>.

2. Wellington, C. Massing, M. Worthington, "Material optimization and application of process controls for "stringer-free" 70/30 copper-nickel and Monel 404 alloys [microwave tube materials]", "Fifth IEEE International Vacuum Electronics Conference, 2004, (IVEC 2004), pp. 107-108, 27-29 April, 2004.

3. EIA/ECA-950, "Alloy for Vacuum Electron Devices", January 2005, <http://www.ecaus.org/engineering/detailsStds.cfm?id1=1567.>.

KEYWORDS: Microwave Tubes, High Purity Metals, Copper-Nickel Alloys, Monel, Cupronickel, Vacuum-Grade Materials.

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