Transparent aluminum or Aluminum Oxynitride (ALON) is an optically transparent aluminum which is a crystalline substance made of aluminate powder alloys.
Aluminum being a popular construction material becomes aesthetically pleasing when a transparent element is added to it. ALON or transparent aluminum is used in various applications like infrared optical windows, sensor components, and the military defense industry.
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This article discusses the features and applications of transparent aluminum in the construction industry.
Features of Transparent Aluminum
- Transparent aluminum or ALON is a transparent polycrystalline ceramic with a cubic spinel crystal structure. Its chemical formula is Al2O27N5.
- ALON is produced by combining aluminum, oxygen, and nitrogen. The manufacturing process involves pressurizing aluminum oxynitride powder to 15,000 pounds per inch in rubber molds submerged in hydraulic fluid. The obtained material, which is molded and opaque, is heated to 2000oC and kept at this temperature for two days. Once cooled, ALON emerges transparent, which is then ground and polished for extra clarity and strength.
- ALON can be fabricated as rods, tubes, plates, windows, domes, and other forms using conventional ceramic powder pressing techniques.
- The grinding and polishing of ALON during its manufacturing improves its impact resistance and mechanical properties.Â
Properties of Transparent Aluminum
- Transparent aluminum is optically transparent, i.e., 80% transparency over the region from near-ultraviolet to visible and near-infrared wavelengths.
- The material remains solid up to a temperature of 1200oC, and it is highly resilient.
- It is three times harder than steel of the same thickness.
The mechanical properties of transparent aluminum are listed in Table-1 below:
| Mechanical Property | Values |
| Compressive strength | 2.68 GPa |
| Flexural strength | 0.38 -0.7 GPa |
| Fracture toughness | 2 MPa/m1/2 |
| Knoop hardness | 1800 kg/mm2 |
| Poisson ratio | 0.24 |
| Shear modulus | 135 GPa |
| Young modulus | 334 GPa |
- Transparent aluminum is delamination resistant as it has less interlaminar residual stress.
- As transparent aluminum is crystal clear, it provides outstanding refractive index homogeneity over large areas.
- It is scratch-resistant and has a high life expectancy.
Applications of Transparent Aluminum
- The toughness of transparent aluminum makes it a great choice for infrared windows.
- It is used for making armored windows and optical lenses.
- Transparent aluminum is used for manufacturing bulletproof glasses.
- It is used in infrared (IR) domes and semiconductor-related applications.
- They are used in refractories, insulators, and heat radiation plates.
The production of transparent aluminum with higher transparency invites a few challenges, which include:
- Minimizing impurities
- Control of grain boundaries
- Elimination of micropores
Several research works are being carried out to improve the transmittance of transparent aluminum by controlling the grain size in a specific wavelength.Â
FAQs
Transparent aluminum or Aluminum Oxynitride (ALON) is an optically transparent aluminum which is a crystalline substance made of aluminate powder alloys.
ALON is produced by combining aluminum, oxygen, and nitrogen. The manufacturing process involves pressurizing aluminum oxynitride powder to 15,000 pounds per inch in rubber molds submerged in hydraulic fluid. The obtained material, which is molded and opaque, is heated to 2000oC and kept at this temperature for two days. Once cooled, ALON emerges transparent, which is then ground and polished for extra clarity and strength.
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