🔗 Transparent Aluminum

Aluminium oxynitride (marketed under the name ALON by Surmet Corporation) is a transparent ceramic composed of aluminium, oxygen and nitrogen. ALON is optically transparent (≥ 80%) in the near-ultraviolet, visible, and midwave-infrared regions of the electromagnetic spectrum. It is four times as hard as fused silica glass, 85% as hard as sapphire, and nearly 115% as hard as magnesium aluminate spinel. Since it has a cubic spinel structure, it can be fabricated to transparent windows, plates, domes, rods, tubes, and other forms using conventional ceramic powder processing techniques.

ALON is the hardest polycrystalline transparent ceramic available commercially. Because of its relatively low weight, distinctive optical and mechanical properties, and resistance to oxidation or radiation, it shows promise for applications such as bulletproof, blast-resistant, and optoelectronic windows. ALON-based armor has been shown to stop multiple armor-piercing projectiles of up to .50 BMG.

ALON is commercially available in sizes as large as 18-by-35-inch (460 mm × 890 mm; 46 cm × 89 cm) monolithic windows.