Spinel structure of ALON
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Names | |
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Systematic IUPAC name
Aluminium oxynitride | |
Identifiers | |
Abbreviations | ALON |
Properties | |
(AlN)x·(Al2O3)1−x, 0.30 ≤ x ≤ 0.37 | |
Appearance | White or transparent solid |
Density | 3.691–3.696 g/cm3[1] |
Melting point | ~2150 °C[1] |
insoluble | |
Refractive index (nD)
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1.79[2] |
Structure | |
cubic spinel | |
a = 794.6 pm[2]
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Aluminium oxynitride (marketed under the name ALON by Surmet Corporation[3]) is a transparent ceramic composed of aluminium, oxygen and nitrogen. Aluminium oxynitride is optically transparent (≥ 80%) in the near-ultraviolet, visible, and mid-wave-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. It can be fabricated into transparent windows, plates, domes, rods, tubes, and other forms using conventional ceramic powder processing techniques.[citation needed]
Aluminium oxynitride is the hardest polycrystalline transparent ceramic available commercially.[2] 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.[4] Aluminium oxynitride-based armor has been shown to stop multiple armor-piercing projectiles of up to .50 BMG.[5]
Aluminium oxynitride is resistant to various acids, bases, and water.[6]
Aluminium oxynitride has the following mechanical properties:[2]
Aluminium oxynitride has the following thermal and optical properties:[7]
Aluminium oxynitride is used for infrared-optical windows, with greater than 80% transparency at wavelengths below about 4 micrometers, dropping to near zero at about 6 micrometers.[8] It has also been demonstrated as an interface passivation layer in some semiconductor-related applications.[9]
Aluminium oxynitride has less than half the weight and thickness of glass-based transparent armor.[10] Aluminium oxynitride armor of 1.6-inch (41 mm; 4.1 cm) thickness is capable of stopping .50 BMG armor-piercing rounds, which can penetrate 3.7 inches (94 mm; 9.4 cm) of traditional glass laminate.[8][11]
In 2005, the United States Air Force began testing aluminium oxynitride-based armor.[12]
Aluminium oxynitride can be fabricated as windows, plates, domes, rods, tubes and other forms using conventional ceramic powder processing techniques. Its composition can vary slightly: the aluminium content from about 30% to 36%, which has been reported to affect the bulk and shear moduli by only 1–2%.[13] The fabricated greenware is subjected to heat treatment (densification) at elevated temperatures followed by grinding and polishing to transparency. It can withstand temperatures of about 2,100 °C (2,370 K) in inert atmospheres. The grinding and polishing substantially improves the impact resistance and other mechanical properties of armor.[7]
Patents related to aluminium oxynitride include: