aluminium oxide
Definition
Noun 1. A chemical compound: Aluminium oxide is a chemical compound of aluminium and oxygen with the formula Al₂O₃. It occurs naturally in various crystalline forms, most notably as the mineral corundum.
Usage
- Aluminium oxide is valued for its hardness and is used as an abrasive and as a refractory material.
- In its gemstone forms, such as ruby and sapphire, aluminium oxide is highly prized.
- The primary ore of aluminium, bauxite, contains aluminium oxide along with other minerals.
Examples
- Industrial Use: "The grinding wheel is coated with aluminium oxide for cutting metal."
- Natural Occurrence: "Aluminium oxide in the form of corundum is one of the hardest naturally occurring substances."
- Scientific Context: "The layer of aluminium oxide on the surface of the metal protects it from further corrosion."
Advanced Usage
- "Activated alumina": This refers to a highly porous form of aluminium oxide used as a desiccant (drying agent) and as a filter medium.
- Example: "The laboratory uses activated alumina to dry the compressed air stream."
- In materials science, specific crystalline structures of aluminium oxide have designations like "alpha-alumina" (the most stable form, e.g., corundum) and "gamma-alumina" (a porous form used as a catalyst support).
Variants and Related Words
- Alumina: This is the most common name for aluminium oxide, especially in industrial and chemical contexts.
- Example: "The refinery produces alumina from bauxite ore."
- Corundum: The natural crystalline mineral form of aluminium oxide.
- Sapphire/Ruby: Gemstone varieties of corundum (aluminium oxide), where trace impurities provide color (blue for sapphire, red for ruby).
Synonyms
- Alumina (n): The most frequent synonym, particularly in technical and commercial language.
- Corundum (n): Specifically denotes the natural mineral form.
Notes on Different Meanings
The term "aluminium oxide" consistently refers to the compound Al₂O₃. Its different meanings or applications stem from its various physical forms (e.g., powdered abrasive, synthetic gemstone, porous catalyst support) and natural occurrences (corundum, ruby, sapphire), not from a change in its fundamental chemical definition.
Noun
-
any of various forms of aluminum oxide occurring naturally as corundum
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