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By trunnano | 11 August 2022 | 0 Comments

Al2O3: Types, structures, and uses

Alumina is the most commonly used material in the field of industrial ceramics. The material has high rigidity and good thermodynamic stability. The material also has excellent electrical and thermal properties, so it is widely used.
Alumina belongs to the rhombohedral system with a melting point of 2054℃ and a boiling point of 2980℃. Due to the difference of steam partial pressure, temperature and pressure, there are many kinds of Al2O3 isomorphs before Al(OH)3 is completely dehydrated to α-Al2O3 at high temperature. It is reported that there are 12 kinds of crystal structures, such as α, β, γ, η, δ, κ, θ and ρ, the most common of which are α, β, and γ. Their density, specific surface area, porosity and acidity vary due to different dehydration conditions and initial aluminum hydroxide.
α-Al2O3 is a rhombohedral system, also known as corundum. The O _ 2-in its Al2O3 crystal is packed closely in hexagonal, while the smaller particle spacing makes the crystal firm and stable. Among all the alumina, α-Al2O3 has the highest density and the most stable crystal phase. Its density is related to impurities and remains about 3.99g/cm3. α-Al2O3 is mainly found in rubies, sapphires and natural corundum.
Although the activity of α-Al2O3 is low, it has excellent properties such as high hardness, high strength, wear resistance, chemical corrosion resistance and good dielectric properties, so it is widely used in refractories and ceramics.
As a kind of alkaline aluminate, the density of β-Al2O3 is about 3.30g/cm3. The stability of β-Al2O3 is poor, and α-Al2O3 and Na2O will be decomposed from it after heating. The interior of Na- β-Al2O3 crystal has a layered structure. Na+ can move and ion exchange freely between layers, so that it has relaxation polarization and ionic conductivity, while Na+ can not be diffused parallel to the C-axis, so that it has no conductivity in the parallel C-axis direction.
Using this property, β-Al2O3 can be used as a diaphragm material in sodium-sulfur battery, and widely used in electronic, medical, mechanical and other fields.
As a transition phase Al2O3, the density of γ-Al2O3 is about 3.42g/cm3. The O2-in γ-Al2O3 crystal structure is distributed at the vertex of cubic lattice, which is closely packed as cubic, and Al3+ is distributed in the packing gap of O2 -. γ-Al2O3 has strong loose adsorption, easy to absorb water and can be dissolved by acid and alkali. Its large specific surface area makes it have high surface energy and high activity. At the same time, γ-Al2O3 will be transformed into stable α-Al2O3 with the increase of temperature, and its volume density increases and volume shrinks at the same time, about 14.3%. The conversion rate and degree of conversion depend on the purity of alumina, preparation conditions and particle size.
Alumina Price
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Alumina Supplier
Luoyang Tongrun Nano Technology Co. Ltd. (TRUNNANO) is a trusted al2o3 manufacturer and al2o3 supplier with over 12-year-experience. We ship our goods all over the world.
If you are looking for high-quality al2o3 powder, please feel free to contact us and send an inquiry. ([email protected])


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