Technology Assessment and Transfer (United States)

Magnesium aluminate spinel is a durable electro-optical material with high visible through mid-IR transmission. Technology Assessment and Transfer (TA and T) reports on their efforts to integrate electromagnetic interference protection into spinel domes through the use of metallic grids. TA and T is developing an approach to embed noble metal EMI grids in spinel domes by encapsulating the grid with a germanate glass that has matching refractive index and coefficient of thermal expansion to spinel. Achievements to date and an outlook on this method as a viable manufacturing route are presented.

Magnesium aluminate spinel is a durable, broadband, electro-optical material that can be readily manufactured into transparent domes for multimode seeker applications. Technology Assessment & Transfer, Inc. reports on the results of its Army SBIR-funded research and development efforts to resolve manufacturing issues with regard to transparent spinel domes. The specific areas of study have been cost, quality, and ability to scale up to full production. Alternative manufacturing approaches were evaluated and compared. A clear path to full scale production has been identified.

This chapter contains sections titled: Abstract Overview of Spinel Transparent Armor The Manufacturing Process Comparison Summary

Magnesium aluminate spinel is a durable, broadband, electro-optical material that can be readily manufactured into transparent domes for multimode seeker applications. Actual spinel domes have suffered from manufacturing difficulties and light-scattering inclusions. The program described herein has solved many of the difficulties to achieve better optical properties and better process yields.

ABSTRACTA powder composite AlCuFe target was used to produce 10 micron films of a quasicrystalline precursor phase by RF sputtering onto polycrystalline alumina substrates. X-ray studies have determined this precursor to be a nano-quasicrystalline phase, despite previous reports of an amorphous structure. Anneals for various times at temperatures between 450°C and 550°C showed the evolution and grain growth of the quasicrystalline approximant structure as a function of both variables. Synchrotron diffraction studies showed a bimodal grain size distribution of the quasicrystalline approximant structure for anneals at 450 °C for 1 hour, below a previously reported transition temperature of 475 °C. Composition analysis of annealed films by XPS depth profiling showed the surface composition to be nearly stoichiometric Al2O3 and extensive oxygen penetration to 160 nm. X-ray diffraction studies have been correlated with cross section microscopy to characterize the development of quasicrystalline films from their precursors. Anneals for longer times and at higher temperatures showed no evidence of a bimodal distribution or remaining nanoquasicrystalline phases.

ABSTRACTThin films of B4C and SiC deposited by magnetron sputtering as components of multilayers have the potential to provide significant property improvements over current wear resistant coating technology. B4C and SiC have previously been found to be amorphous and possibly nanocrystalline under the deposition conditions used. This study reports results of synchrotron x-ray scattering experiments providing information on the degree of crystallinity, strain, average density, and coordination number in 2000 Å films of these compounds on Si substrates. Radial distribution functions from B4C and SiC thin films were obtained and used to model the structure. Strain results are compared with Double Crystal x-ray Diffraction Topography (DCDT) results as a means for establishing a standard strain state.