Aluminium oxynitride

Aluminium oxynitride or ALON is a ceramic composed of aluminium, oxygen and nitrogen. It is marketed under the name ALON by Surmet Corporation.[3] ALON is optically transparent (≥80%) in the near-ultraviolet, visible and midwave-infrared regions of the electromagnetic spectrum. It is four 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.[2] Its 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 optoelectronics.[4] ALON-based armor has been shown to stop multiple armor-piercing projectiles of up to .50 BMG cal.[5] It is commercially available in sizes as large as 18 by 35 inches (460 mm × 890 mm) monolithic windows.[6]

Aluminium oxynitride

Spinel structure of AlON
Names
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
1.79[2]
Structure
cubic spinel
a = 794.6 pm[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Properties
Mechanical[2]
Thermal and optical[7]
  • 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.[8]

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, speciality IR domes, windows for laser communications, and in some semiconductor-related applications.[9][10]

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 aluminium after a fictional Star Trek material.[11] 1.6 inches (41 mm) thick ALON armor is capable of stopping .50 BMG armor-piercing rounds, which can penetrate 3.7 inches (94 mm) of traditional glass laminate.[12]

Military

In 2005, the United States Air Force began testing ALON, "to shield troops".[13]

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%.[14]. 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.[7]

Aluminum oxynitride is not mentioned in the 1986 film Star Trek IV: The Voyage Home, but "transparent aluminum" became a popular phrase after appearing in the film. [15] [16]

Aluminum oxynitride is mentioned and described in the Jack Reacher novel, Personal by Lee Child, and mentioned by Jimmy Fallon as the material used to create the gyrosphere vehicles' outer protective bubble in the 2015 film Jurassic World.

See also

Patents

References
  1. "ALON Optical Ceramic. Technical data" (PDF). Surmet Corporation. 2003. Archived from the original (PDF) on 2013-06-12. Retrieved 2009-01-09.
  2. Mohan Ramisetty et al. Transparent Polycrystalline Spinels Protect and Defend, American Ceramic Society Bulletin, vol.92, 2, 20–24 (2013)
  3. Richard L. Gentilman et al. Transparent aluminum oxynitride and method of manufacture U.S. Patent 4,520,116 Issue date: May 28, 1985
  4. "Domes & Infrared Optics". Surmet.
  5. Ramisetty, Mohan; Sastri, Suri A.; Goldman, Lee (Aug 2013). "Transparent Ceramics Find Wide Use in Optics". Photonics Spectra.
  6. "Surmet Achieves Major Milestone on its ALON® Window Scale-up Program". PRWeb. May 28, 2013.
  7. Joseph M. Wahl et al. Recent Advances in ALONTM Optical Ceramic, Surmet
  8. Corbin, N (1989). "Aluminum oxynitride spinel: A review". Journal of the European Ceramic Society. 5 (3): 143–154. doi:10.1016/0955-2219(89)90030-7.
  9. Lee M. Goldman et al. ALON® Optical Ceramic Transparencies for Sensor and Armor Applications, Surmet
  10. Zhu, Ming; Tung, Chih-Hang; Yeo, Yee-Chia (2006). "Aluminum oxynitride interfacial passivation layer for high-permittivity gate dielectric stack on gallium arsenide". Applied Physics Letters. 89 (20): 202903. doi:10.1063/1.2388246.
  11. Optically Clear Aluminium Provides Bulletproof Protection, TSS, 3 June 2015, accessed 10 July 2015
  12. Surmet's ALON® Transparent Armor .50 Caliber Test
  13. Schogol, Jeff (October 30, 2005). "Air Force testing lighter, transparent ALON armor". Stars and Stripes. Retrieved June 25, 2020.
  14. Graham, Earl K.; Munly, W.C.; McCauley, James W.; Corbin, Norman D. (1988). "Elastic properties of polycrystalline aluminum oxynitride spinel and their dependence on pressure, temperature and composition". Journal of the American Ceramic Society. 71 (10): 807–812. doi:10.1111/j.1151-2916.1988.tb07527.x.
  15. Harve Bennett, Nicholas Meyer, Steve Meerson, & Peter Krikes (1986). "Screenplay for Star Trek IV: The Voyage Home". Retrieved 2020-02-22.CS1 maint: multiple names: authors list (link)
  16. Harve Bennett, Nicholas Meyer, Steve Meerson, & Peter Krikes (1986). "Screenplay for Star Trek IV: The Voyage Home". Retrieved 2020-02-22.CS1 maint: multiple names: authors list (link)
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