Alumina Powder: Where, How, and Why It’s Used

Alumina powder Photo credit: Tehran Times

Alumina powder, also known as aluminum oxide (Al2O3), is a white, crystalline substance made from refining bauxite ore. It’s the main component in making alumina ceramics for various industry applications due to its innate properties, like wear resistance.

Industry Applications of Alumina Powder

Alumina ceramics

Alumina powder is a versatile substance that has several industry applications. The alumina ceramics you make from it will show high-performance qualities (more about this in the later section of this article).

Listed below are some of the applications of alumina powder:

Abrasives – Alumina powder, specifically highly pure ones, can resist abrasions, making it perfect for abrasive products like grinding media and sandpaper.
Biomedical Material – Alumina powder-made ceramics have great biocompatibility. It allows them to be used in manufacturing artificial joints and bones, dental crowns, and other medical implants.
Ceramic Sheets – Typically made from 99.0% alumina powder. These sheets have a high-temperature ability that allows them to be used in environments with high humidity.
Electronics – Alumina powder has good thermal and electrical insulation properties. It can be used to make high-voltage insulators and electrical enclosures and substrates.
Engineered Ceramics – These are used in more technical or advanced applications, such as semiconductor manufacturing, CVD processing, and photolithography. To make these, high-purity alumina powder is needed for these to resist wear, chemical reactions, and thermal changes.
Filler Material – Alumina powder can act as a filler material. It helps ensure that products like rubbers and plastics can resist temperature changes and strains.
Glass – Because alumina powder is hard and resistant to pressure, it makes glass bulletproof and shatterproof.
Labware – Alumina powder has a high melting point and is chemically inert. So, it’s most suitable for labware typically used to grind and heat chemical compounds.
Military Use – Alumina powder is used in manufacturing body armor and bulletproof vests because its innate properties allow it to be shock-absorbant.
Refractories – Refractory materials need to have thermal shock resistance and high melting point, which alumina powder possesses.

How Alumina Powder Is Used

In manufacturing alumina ceramics, the alumina powder you’ll use depends on 2 factors: type and level of purity. It’s best to choose the ones that are most beneficial to your product. For example, if you want the product to be extremely hard, a calcined alumina powder is a plausible choice.

You can refer to the tables below to know each type and purity level of alumina powder further.

Types of Alumina Powder

It’s recommended that you only work with the type of alumina powder that matches the specifications of your application. Fortunately, there are only 3 main types you can choose from, which vary depending on the following:

Their iron (Fe2O3), silica (SiO2), and soda (Na2O) content
The alumina powder’s purity level and specific properties used in their production

Types	Description
Calcined alumina	A highly pure alumina, at 99.9%. It resulted from heating the alumina powder to 1050°C to remove the water and impurities in it.
Tabular alumina	A sintered calcined alumina known for its heat resistance, strength, and density.
Hydrated alumina	An alumina known for its high melting point. It’s popularly used in glazes because it can enhance color and adhesive qualities.

Purity Level of Alumina Powder

Alumina powder’s chemical structure (Al2O3) Photo credit: PubChem

The levels vary based on how pure the alumina powder content is in the material composition of the alumina ceramics. Each one has its specific usage.

But of course, we can’t deny that the higher the purity level used in your product, the better its quality.

Purity Level	Usage	Example Applications
99.9% alumina	Used only in highly critical applications where one or a combination of the following properties is essential: Mechanical Electrical Thermal Corrosion resistant	Nuclear-grade insulators Plasma etching components
99.8% alumina	Used in applications that require first-rate plasma and chemical resistance and high dielectric properties	Semiconductors
99.7% alumina	Used in applications that require the following: 98% reflectance at 1064 nanometers 96% reflectance from 500–2000 nanometers	Laser reflectors
99.5% alumina	Used in applications that require a combination of electrical and chemical resistance	Semiconductors, including fixtures and chambers
99.0% alumina	Used in applications that require hardness and resistance	Rotary components Reciprocating pumps for chemicals
98.6% alumina	Used in applications that require lightweight materials	Armors in military vehicles
97.6% alumina	Used in applications that require dimensional and electrical stability in varying temperatures	Laser components X-rays Electro-optical devices
97.5% alumina	Used in applications that require thick metal coatings and abrasion and chemical resistance	Resistor networks Dielectric layers Conductors
97.0% alumina	Used in applications that require electrical insulation	X-ray tubes Insulation for medical devices Electron microscopes
96.0% alumina	Used in applications that require a combination of the following properties: Electrical Chemical Thermal Mechanical	Medical devices, such as nozzles, electrical connector housings, and blood valves
95.0% alumina	Used in applications that require enhanced compressive and flexural strength, as well as first-rate hermeticity	Ceramic-to-metal feed-throughs Medical implants Military body armor
94.0% alumina	Used in applications that require the addition of manganese metal coating and the following properties: : Low thermal expansion Dielectric constant High volume resistivity Chemical resistant Abrasion resistant	Bearing coatings Pressure sensor Electron tube
92.0% alumina	Used in applications that require it to be dense and non-porous	Electrical packaging Grinding media

Zirconia Toughened Alumina

Zirconia toughened alumina (ZTA) is a special type that combines alumina powder with 10%–20% zirconia (zirconium oxide, ZrO2).

With zirconia embedded into the alumina matrix composite, the resulting material will have enhanced strength, toughness, and wear resistance. It’s so much better than if it was made from a highly pure alumina powder.

Characteristics That Made Alumina Powder a Viable Material

Firing ceramics Photo credit: Viviane Okubo on Unsplash

Up to this point, we have mentioned the quality of alumina ceramics. So, what is in alumina powder that makes these ceramics resistant to wear, corrosion, high temperatures, and chemicals?

Density – Alumina powder is ground to the nanometer to ensure its grain size is between 3 and 5 microns after firing. It ensures fewer voids in the alumina ceramics, resulting in higher density, which in turn, leads to optimum wear surface.
High-temperature resistance – Unlike metal, alumina powder retains its properties in high temperatures. It can withstand up to 1650°C in oxidizing and reducing environments and up to 2000°C in vacuum environments.
Abrasion resistance – Alumina powder is, by nature, hard, having hra80-90 on the Rockwell hardness scale. So, it has high abrasion resistance, ensuring that the alumina ceramics won’t be worn down easily.
Chemical resistance – Alumina powder is chemically inert, so substances like solvents won’t have much effect on the alumina ceramics.
Mechanical – Alumina powder can handle stress and strains due to its inherent hardness. Plus, the higher the purity of alumina powder in the alumina ceramics, the higher its mechanical characteristics.
Dielectric – Alumina powder can help alumina ceramics withstand electromagnetic voltage without dielectric loss. Such characteristic makes it ideal for the production of insulation materials.
Thermal – Because alumina powder can adapt to high temperatures, it has high resistance to thermal conductivity. The effect of thermal shock on alumina ceramics will be minimized.

FAQ

Is Alumina Powder Safe to Use?

Yes. Alumina powder isn’t immediately dangerous to your health or life. However, you must take care not to inhale it or make eye or skin contact with it. Otherwise, it’ll cause respiratory issues and eye and skin irritations, respectively. (You can read more about it at PubChem.)

So, to ensure your safety, it’s best to follow the safety guidelines and wear appropriate personal protective equipment.

Is Alumina Powder the Same as Alumina Ceramics?

No. Alumina powder (aluminum oxide, Al2O3) is the substance that alumina ceramics are made from.

Is Alumina Powder the Same as Aluminum Powder?

No. One factor that distinguishes them is their ability to react to chemicals. Alumina powder has high chemical inertness that makes it stable and resistant to corrosion.

Aluminum powder, on the other hand, is made up of metallic aluminum (Al) which will oxidize when exposed to air. The oxidized layer will then result in an oxide film that will help with its corrosion resistance.

Conclusion

Alumina powder is a flexible substance used in different industry applications. Each application is made from a certain type and purity that ensures the alumina ceramics function as they should.

For example, you’re manufacturing labwares. You’ll use 99.0% or above purity level to achieve optimal thermal and chemical properties.