Alumina (Al2O3) Nanoparticles - Properties & Applications

By Reginald DaveyReviewed by Megan Craig, M.Sc.Apr 4 2013

This article was originally published in 2013 and has since been updated.

Alumina nanoparticles are valued for their enhanced properties compared to bulk materials. These particles, less than 100 nm in diameter, exhibit improved hardness, strength, and conductivity due to their small size. To learn more about the properties, applications in various industries, and eco-friendly synthesis methods of alumina nanoparticles, continue reading.

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The surface effects and properties of nanoparticles are directly related to their small size, as when materials are produced from nanoparticles, a substantial number of atoms are exposed on the surface. It has been shown that the performance and behavior of materials are altered when constructed on the nanoscale.

Aluminum is a Block P, Period 3 element, while oxygen is a Block P, Period 2 element.

Al₂O₃ nanoparticles possess aspherical morphology, appearing as a white powder. Alumina nanoparticles (both liquid and solid forms) are graded as highly flammable and an irritant that can cause serious eye and respiratory irritation.

Chemical Properties of Aluminum Oxide Nanoparticles

The chemical properties of aluminum oxide nanoparticles are outlined in the following table.

Physical Properties of Aluminum Oxide Nanoparticles

The physical properties of aluminum oxide nanoparticles are given in the following table.

Thermal Properties of Aluminum Oxide Nanoparticles

The thermal properties of aluminum oxide nanoparticles are provided in the table below.

Manufacturing Process of Aluminum Oxide Nanoparticles

Aluminum oxide nanoparticles can be synthesized by many techniques, including ball milling, sol-gel, pyrolysis, sputtering, hydrothermal, and laser ablation. Laser ablation is a commonly used technique to produce nanoparticles since they can be synthesized in a gas, vacuum, or liquid.

The technique offers several advantages, such as a rapid and high-purity process compared with other methods. Additionally, nanoparticles prepared by the laser ablation of materials in liquid are collected more easily than those in a gas atmosphere.

Within the last couple of decades, chemists at the Max-Planck-Institut für Kohlenforschung in Mülheim an der Ruhr found a way to produce corundum (also known as alpha-alumina), a very stable variant of alumina in the form of nanoparticles using a simple ball mill method.

Applications of Aluminum Oxide Nanoparticles

Electronics and Optoelectronics:

Aluminum oxide nanoparticles find extensive use in various electronic and optoelectronic applications, including:

• Integrated circuit baseboards for enhanced performance.
• Transparent ceramics, high-pressure sodium lamps, and EP-ROM windows, contributing to the development of efficient lighting and data storage technologies.
• YAG laser crystals that enable precise laser systems.
• Sapphire and yttrium aluminum garnets, serving as essential components in optical and laser systems.

Advanced Materials and Manufacturing:

These nanoparticles play a crucial role in creating high-strength aluminum oxide ceramics and substrates, which are utilized in:

• Packaging materials for electronics and sensitive equipment.
• Cutting tools and high-purity crucibles for material processing.
• Polishing materials for glass, metal, and semiconductor products.
• Plastic, tape, and grinding belts, enhancing the durability and performance of manufacturing tools.

Coatings and Functional Materials:

Aluminum oxide nanoparticles contribute to the development of coatings and functional materials, including:

• Paints, rubber, and plastic additives, increasing wear resistance.
• Advanced waterproof materials, ensuring protection in various environments.
• Catalysts and catalyst carriers, facilitating chemical reactions and industrial processes.
• Analytical reagents, aiding in laboratory research and analysis.

Aerospace and Aviation:

In the aerospace industry, these nanoparticles are used in applications such as:

• Aircraft wing leading edges, where they enhance durability and resistance to high-speed airflow.

Miscellaneous Applications:

Aluminum oxide nanoparticles also play roles in various other fields, including:

• Vapor deposition materials, contributing to thin-film production.
• Special glass and fluorescent materials, enhancing optical properties.
• Composite materials and resins, strengthening structural components.

Applications in Liquid Form (Aqueous Dispersion):

When utilized in liquid form, aluminum oxide nanoparticles serve diverse purposes:

Advanced Materials:

• They improve the density, smoothness, fracture toughness, creep resistance, and thermal fatigue resistance of ceramics, ensuring their suitability for demanding applications.
• Polymer products benefit from enhanced wear resistance when aluminum oxide nanoparticles are incorporated.

Far Infrared Emission Technologies:

• These nanoparticles find application as materials for far infrared emission technologies, contributing to the development of specialized devices.

Aluminum oxide nanoparticles, whether in solid or liquid form, continue to drive innovation across multiple industries, offering enhanced performance, durability, and functionality in various applications.

Research Perspective: Synthesizing Alumina Nanoparticles Using Green Chemistry Methods

Conventional nanoparticle synthesis does not often meet the requirements of green chemistry despite the great potential of nanotechnology in controlling and preventing disease. This is because synthesis methods commonly use highly toxic and environmentally damaging chemicals and large amounts of resources.

Plant-mediated synthesis could overcome these critical issues, improving the sustainability and efficiency of producing materials such as Al₂O₃ nanoparticles.

A recent paper published in the journal Environmental Chemistry Letters has reviewed these green synthesis methods and applications of alumina nanoparticles in biomedical science and water treatment.

The paper explores eco-friendly alternatives for the synthesis of these nanoparticles, such as alkaloids, flavonoids, polyphenols, and quercetins, which are commonly found plant extracts that function as complexing and capping agents for alumina nanoparticle synthesis.

Al₂O₃ nanoparticles produced using these green chemistry processes exhibit favorable physical properties, specific surface areas, and diverse ranges of crystal phase and shape.

The research paper highlights the superior ability of these green nanoparticles to remove over 90% of contaminants such as nitrate, organic dyes, and fluoride from water supplies. Additionally, they display favorable antifungal, antioxidant, and antibacterial activities, making them attractive targets for biomedical science.

In Summary

Alumina (AL₂O₃) nanoparticles are an emerging material in many industries, with vast potential in multiple additional scientific sectors. They display favorable chemical and physical properties, which make them attractive research targets.

While conventional preparation of these nanoparticles does not satisfy the requirements of green chemistry, some promising research has been undertaken in this area, further cementing these nanoparticles as innovative materials for the future of many industries.

Read this interview to learn more.

References and Further Reading

Tran, G.T et al. (2023) Plant extract-mediated synthesis of aluminum oxide nanoparticles for water treatment and biomedical applications: a review Environmental Chemistry Letters 21 pp. 2417-2439 [online] link.springer.com. Available at: https://link.springer.com/article/10.1007/s10311-023-01607-0

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