In the field of high-end manufacturing and advanced materials, high-purity alumina is a vital basic material. Its purity usually reaches 99.99% (4N grade) or even 99.999% (5N grade) or above. With its excellent physical and chemical properties, it is widely used in semiconductor, new energy, optics, medical and other industries.
So, what exactly is high-purity alumina powder? What are its unique properties? How is it prepared and applied? Today, let's take a deeper look at this material.
1. What is high-purity alumina powder?
The main component of high-purity alumina powder is alumina, but unlike ordinary industrial alumina, it has extremely high purity and extremely low impurity content (such as Na, Fe, Si, etc. controlled at the ppm level). According to the purity, it can be divided into:
• 4N grade (99.99%)
• 5N grade (99.999%)
• 6N grade (99.9999%)
The higher the purity, the better the performance and the higher the application field.
2. Unique properties of high-purity alumina powder
(1) Ultra-high hardness
The Mohs hardness of alumina is as high as 9, second only to diamond and silicon carbide. It can be used for precision polishing, wear-resistant coatings, etc.
(2) High temperature resistance
The melting point is about 2050℃. It can remain stable in high temperature environments and is suitable for refractory materials, aerospace components, etc.
(3) Excellent insulation
It has high resistivity and good dielectric properties, making it an ideal material for electronic components and integrated circuit substrates.
(4) Strong chemical stability
It is resistant to acid and alkali corrosion and is not easy to decompose even in strong acid and alkali environments. It is suitable for chemical, biomedical and other fields.
(5) Optical properties
High-purity alumina can be made into transparent ceramics for lasers, infrared windows, LED substrates, etc.
3. How is high-purity alumina powder prepared?
(1) Alcohol salt hydrolysis method (high purity 5N grade or above)
Using high-purity aluminum alkoxide as raw material, hydrolysis produces aluminum hydroxide, and then calcination to obtain ultra-fine high-purity Al2O3, which is suitable for semiconductor-grade applications.
(2) Modified Bayer process (4N grade mainstream process)
The traditional Bayer process purifies bauxite, and then combines ion exchange, recrystallization and other processes to remove impurities. It has low cost and is suitable for large-scale production.
(3) Ammonium sulfate method
Through the reaction of ammonium sulfate and aluminum salt, multiple crystallization and purification, it is suitable for the preparation of high-purity ultra-fine powder.
(4) Spark discharge plasma method (nanoscale preparation)
It is used to produce nano-high-purity alumina, with finer particle size and larger specific surface area.
4. Application fields of high-purity alumina powder
(1) LED and semiconductor industry
• Sapphire substrate (single crystal Al₂O₃) is the key material for LED chips. For example, High Purity Alumina Powder For Sapphire.
• Used in semiconductor packaging, integrated circuit substrate, etc.
(2) New energy battery
• Lithium battery diaphragm coating, improves high temperature resistance and electrolyte wettability, and enhances safety.
• Research material for solid electrolyte.
(3) Precision polishing (CMP)
• Ultra-precision polishing of silicon wafers, optical glass, and hard disk platters.
(4) Transparent ceramics
• High-pressure sodium lamp tubes, laser windows, and bulletproof armor.
(5) Biomedicine
• Reinforcement phase of artificial joints and dental restoration materials, with excellent biocompatibility.
(6) Other high-end applications
• Aerospace high-temperature resistant coatings, catalyst carriers, high-end refractory materials, etc.
Although high-purity alumina powder is not as popular as graphene and carbon nanotubes, it plays an irreplaceable role in modern high-tech industries. From sapphire glass in mobile phone screens to battery separators in electric vehicles, from semiconductor chips to artificial joints, it is everywhere. In the future, with the advancement of materials science, the application boundaries of high-purity alumina powder will continue to expand.