SITIS Archives - Topic Details
Program:  SBIR
Topic Num:  N102-163 (Navy)
Title:  High Strength, Optical Quality Spinel
Research & Technical Areas:  Air Platform, Materials/Processes, Sensors

Acquisition Program:  Naval Unmanned Combat Air System (NUCAS) PMA-268
 RESTRICTION ON PERFORMANCE BY FOREIGN NATIONALS: This topic is “ITAR Restricted”. The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120-130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign nationals may perform work under an award resulting from this topic only if they hold the “Permanent Resident Card”, or are designated as “Protected Individuals” as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign national who is not in one of the above two categories, the proposal may be rejected.
  Objective:  Increase the mean mechanical strength of optical quality spinel for large windows to 300 MPa with a Weibull modulus of at least 6 to reduce the thickness and weight required for large-area applications.
  Description:  Of the three available durable midwave infrared sensor window materials, spinel has the widest transmission window and the lowest mechanical strength. For applications such as reconnaissance, windows need to be as thin as possible to maximize transmission and minimize weight. However, the thickness must be great enough to bear the required mechanical load. The goal of this SBIR topic is to increase the strength of spinel to at least 300 MPa with a Weibull modulus of at least 6, while retaining the best possible optical quality. The method must be scaleable to make windows with dimensions of at least 0.40 x 0.40 x 0.013 m.

  PHASE I: Conduct coupon-level experiments to demonstrate a method to make optical quality spinel with a mean strength of at least 300 MP and Weibull modulus of at least 6, as measured in biaxial flexure with 38-mm-diameter x 2-mm-thick disks. Methods used must be scaleable to eventually give windows with dimensions of at least 0.40 x 0.40 x 0.013 m. Coupons should have not more than 0.5% total integrated forward optical scatter at 3.39 microns and should be free of obvious inclusions and defects and stress birefringence.
  PHASE II: Optimize the mechanical strength of large spinel windows while retaining excellent optical quality. Goals are a mean strength of at least 300 MPa with a Weibull modulus of at least 6. Evaluate mechanical and optical properties with coupons cut out of 0.40 x 0.40 x 0.013 m plates.

  PHASE III: Scale up for commercial production of 0.4 x 0.4 m or larger finished windows for Navy airborne reconnaissance platforms or a Navy ship such as the DDX-1000 destroyer. PRIVATE SECTOR COMMERCIAL POTENTIAL/

  DUAL-USE APPLICATIONS: There is a potentially large market for strengthened spinel for bulletproof windows for armored vehicles

  References:   1. S. M. Sweeney, M. K. Brun, T. J. Yosenick, A. Kebbede, and M. Manoharan, “High Strength Transparent Spinel with Fine, Unimodal Grain Size,” Proceedings of SPIE. 2009, 7302, 73020G. 2. J. L. Sepulveda, R. O. Llutfy, S. Chang, S. Ibrahim, and N. Traggis, “Advances in Spinel Ceramic Technology for large Windows and Domes,” Proceedings of SPIE. 2009, 7302, 73020E. 3. J. R. Bashe and D. Hibbared, “Observations During the Fabrication of Spinel Optics,” Proceedings of SPIE. 2009, 7302, 73020C.

Keywords:  Spinel; Infrared Window; Transparent Ceramic; Mechanical Strength

Questions and Answers:
Q: 1) Does the method of manufacture matter more than the final properties?
2) Will weight be given to new methods to achieve the end goal?
3) Should a higher Weibull modulus than 6 be demonstrated, could a thinner than 13mm thickness end up being used in the final application?
A: 1. The manufacturing method must be able to produce spinel at a reasonable cost in comparison to existing manufacturing methods and it should be scalable for a range of sizes.

2. We will consider any sensible method.

3. The higher the Weibull modulus, the better. Any thickness could be required in the future. For large windows, a thickness of 13 mm is representative.

Record: of