Aluminium oxynitride or AlON is a ceramic composed of aluminium, oxygen and nitrogen. It is marketed under the name ALON by Surmet Corporation. AlON is optically transparent (>=80%) in the near-ultraviolet, visible and midwave-infrared regions of the electromagnetic spectrum. It is 4 times harder than fused silica glass, 85% as hard as sapphire, and nearly 15% harder than 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. Combination of optical and mechanical properties makes this material a leading candidate for lightweight high-performance transparent armor applications such as bulletproof and blast-resistant windows and for many military infrared optics. AlON-based armor has been shown to stop multiple armor-piercing projectiles of up to 50 cal. It is commercially available in sizes as big as 18x35-inch monolithic windows.
Video Aluminium oxynitride
Properties
- Mechanical
- Young's modulus 334 GPa
- Shear modulus 135 GPa
- Poisson ratio 0.24
- Knoop hardness 1800 kg/mm2 (0.2 kg load)
- Fracture toughness 2.0 MPa·m1/2
- Flexural strength 0.38-0.7 GPa
- Compressive strength 2.68 GPa
- Thermal and optical
- Specific heat 0.781 J/(g·°C)
- Thermal conductivity 12.3 W/(m·°C)
- Thermal expansion coefficient ~4.7×10-6/°C
- Transparency range 200-5000 nm
ALON also appears to be radiation-resistant and resistant to damage from various acids, bases, and water.
Maps Aluminium oxynitride
Applications
In addition to being used as a transparent armor material, AlON is used as infrared-optical windows. As such it has applications as a sensor component, specialty IR domes, windows for laser communications, and in some semiconductor-related applications.
Bulletproof glass
As a transparent armor material, AlON provides a bulletproof product with far less weight and thickness than traditional bulletproof glass. It has been dubbed transparent aluminum after a fictional Star Trek material. 1.6" thick ALON armor is capable of stopping .50 BMG armor-piercing rounds, which can penetrate 3.7" of traditional glass laminate.
Manufacture
ALON 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%.) 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 2100 °C in inert atmospheres. The grinding and polishing substantially improves the impact resistance and other mechanical properties of armor.
See also
- Transparent ceramics
- Transparent aluminium in Star Trek - a fictional material used in Star Trek IV: The Voyage Home
Patents
- Process for producing polycrystalline cubic aluminum oxynitride JW McCauley U.S. Patent 4,241,000, 1980
- Aluminum oxynitride having improved optical characteristics and method of manufacture TM Hartnett, RL Gentilman U.S. Patent 4,481,300, 1984
- Transparent aluminum oxynitride and method of manufacture RL Gentilman, EA Maguire U.S. Patent 4,520,116, 1985; U.S. Patent 4,720,362, 1988
- Transparent aluminum oxynitride-based ceramic article JP Mathers U.S. Patent 5,231,062, 1993
References
External links
- The Influence of Sintering Additives on the Microstructure and Properties of ALON. Yechezkel Ashuach. Master's Thesis, Technion - Israel Institute of Technology, 2003
- Solubility Limits of La and Y in Aluminum Oxynitride (AlON) at 1870°C Lior Miller and Wayne D. Kaplan. Department of Materials Engineering, Technion, Haifa, Israel, 2006
- Processing of Optically Transparent Aluminum Oxynitride
Source of article : Wikipedia
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