Transparent Alumina by Hotpressing Platelets into an Aligned Grain Microstructure
A cost-effective technique uses hot-pressing of platelet alumina crystals to create highly transparent, high-density polycrystalline alumina for use in armored windows, rocket nose cones, and protective shields across a broad spectral range.
Researchers at Purdue University have developed new highly transparent polycrystalline alumina materials by
hot-pressing platelets alumina crystals and aligning its grain structure to induce low amounts of grain boundary refraction and reflection. This cost-effective transparent alumina processing technique can be used for applications including high-temperature and armored windows, nose cones for rockets, and ballistic blast as well as protective shields. Purdue researchers have fine-tuned fabrication parameters for the new alumina including specified powder and treatment steps sintering temperatures, green-body and hot-pressing geometries, pre-load pressures and hot pressing pressure to achieve a high density of upwards of 99.95%. This allows a real in-line transmission (RIT), defined as a transmission within a 0.5 degree cone of the center beam, of over 70% and a total transmission of over 80 % at 645nm, approaching the theoretical limit of single crystal sapphire (86%). Notably, the aligned grain microstructure limits grain-induced scattering typically seen with polycrystalline translucent alumina with variance of only 15% in RIT over the wavelength range 280 nm to 2500 nm, allowing this material to be continuously effective in a spectral range from UVB to NIR.
Advantages:
-Transparent
-Cost-Effective
Potential Applications:
-Nose Cones for Rockets
-High-Temperature and Armored Windows
-Blast and Protective Shields
Recent Publication:
"Hot-pressing platelet alumina to transparency"
Journal of the American Ceramic Society
DOI: /10.1111/jace.16932
TRL: 5
Intellectual Property:
Provisional-Gov. Funding, 2020-03-02, United States | Utility-Gov. Funding, 2020-12-15, United States | DIV-Gov. Funding, 2024-06-11, United States
Keywords: Transparent polycrystalline alumina, hot-pressing, platelet alumina crystals, aligned grain structure, high density alumina, real in-line transmission, RIT, armored windows, ballistic shields, nose cones, high-temperature windows, ceramic transparency, Aeronautics, aerospace, Cost-Efficient, High-Temperature, Material Development, Materials and Manufacturing, Materials Engineering, Materials Science, Micro & Nanotechnologies, Military, Rocket, Shielding, Smart Windows, Transparent