Hydrated alumina is a type of hydrated alumina compound widely used in industry, materials, environmental protection, and medicine. Its core functions can be summarized as follows:
Flame retardant and filler function (most common application)
Hydrated alumina (especially trihydrated alumina Al(OH)₃) is a non-toxic, halogen-free, environmentally friendly flame retardant, widely used in organic polymer materials such as plastics, rubber, cables, and unsaturated polyesters.
Its flame retardant mechanism is as follows:
Endothermic decomposition: When the temperature rises above 200℃, hydrated alumina decomposes into alumina and water (2Al(OH)₃ → Al₂O₃ + 3H₂O↑). This process absorbs a large amount of heat (approximately 1967 kJ/kg), effectively inhibiting the temperature rise of the material.
Dilution of combustible gases: The released water vapor dilutes the concentration of oxygen and combustible gases, inhibiting the spread of combustion.
Formation of an insulating layer: Residual alumina forms a dense inorganic layer on the material surface, isolating oxygen from contact with combustibles.
Furthermore, it also functions as a filler, improving the material's hardness, weather resistance, and processing performance; the addition amount can reach 30%-40%.
Preparation of alumina ceramics and functional materials:
Hydrated alumina is a key precursor for preparing high-performance alumina ceramics. Through high-temperature calcination (>1273K), it can be converted into α-Al₂O₃, possessing high thermal stability, high strength, low coefficient of expansion, and excellent dielectric properties, and is used in:
Electronic ceramics, refractory materials, grinding media. The controllable synthesis of nano-alumina, achieved by regulating the preparation process of boehmite (boehmite monohydrate), allows for precise control of the final alumina microstructure.
Catalysis and Support Applications
Catalyst Supports: Hydrated alumina such as boehmite and gibbsite possess high specific surface area and porosity, and are commonly used as catalyst support materials in petroleum catalytic cracking (FCC), automotive exhaust treatment, and hydrogenation reactions.
Activated Alumina Precursors: γ-Al₂O₃ (activated alumina), obtained by dehydrating hydrated alumina, exhibits strong adsorption and catalytic activity and is widely used in adsorbents, desiccants, catalyst supports, and other fields.
