Physical properties: It is a white solid at room temperature, with a melting point of up to 2072 ° C, high hardness (Mohs hardness of 9, second only to diamond), and insoluble in water.

Chemical properties: Belonging to amphoteric oxides, it can react with strong acids (such as hydrochloric acid) or strong bases (such as sodium hydroxide) to form salts and water.

Form of existence

Natural existence: It exists in the form of corundum in nature, with ruby (containing chromium) and sapphire (containing iron and titanium) being its gemstone variants.

Industrial forms: Common α - Al ₂ O3 (stable phase, used in ceramics and abrasives) and γ - Al ₂ O3 (porous, used as catalyst support).

application area 

Industrial materials: refractory materials (furnace lining), abrasives (sandpaper, cutting tools), ceramics (toughening).

Chemical industry: catalyst carriers (such as petroleum refining), adsorbents (desiccants, purifiers).

High tech: laser materials (doped corundum), semiconductor substrates (sapphire chips), bioceramics (artificial joints).

Daily necessities: toothpaste abrasives, cosmetic fillers.

Preparation method

Natural extraction: Extracting bauxite through the Bayer process (alkali dissolution, precipitation, calcination).

Synthesis production: High temperature oxidation of aluminum (4Al+3O ₂ → 2Al ₂ O3) or dehydration of aluminum hydroxide (2Al (OH) V3 → Al ₂ O3+3H ₂ O).

matters needing attention

Dust protection: Long term inhalation may cause respiratory irritation, and dust prevention equipment should be worn.

High temperature operation: Molten alumina should be protected from burns and avoid direct contact with strong acids/alkalis.

Expand knowledge

Nano alumina: used to enhance the strength of composite materials and improve the wear resistance of coatings.

Porous alumina template: an important substrate material for preparing nanowires/tubes.