Crystals can be divided into alumina trihydrate and alumina monohydrate according to the number of water molecules in their structure. Aluminum oxide trihydrate (also known as aluminum hydroxide) has three crystal forms: α-Al2O3·3H2O, β-Al2O3·3H2O, and new β-Al2O3·3H2O. Alumina monohydrate (also known as hydroxyl alumina) comes in two crystal forms: γ-AlOOH and α-AlOOH.
Application of hydrated alumina
1. As a precursor of activated alumina
Activated alumina (such as γ-Al2O3) has a rich mesopore structure and relatively active chemical properties. It has good thermal and hydrothermal stability under catalytic cracking operating conditions, so adding activated alumina to the catalyst has become a common method to improve the activity of the matrix. Pseudo-boehmite and Boehmite are both precursors of activated alumina and play different roles in catalysts. The catalyst prepared with acidified pseudo-boehmite as a binder has the advantages of good pore structure and the strong cracking ability of heavy oil. The catalyst containing Boehmite has better resistance to heavy metals.
2. Prepare flame retardants
Aluminum hydroxide (aluminum oxide trihydrate) powder is often regarded as an ideal flame retardant filler for plastics, unsaturated polyesters, rubber, and other organic polymers because of its filling, flame retardant, smoke suppression function and non-toxic and harmless. Flame retardant mechanism of aluminum hydroxide: When the temperature exceeds 200 ° C, aluminum hydroxide begins to absorb heat decomposition and release three crystal water, and its decomposition rate is maximum at about 250 ° C. This reaction is a strong endothermic reaction, which inhibits the rise of polymer temperature, reduces its decomposition rate, only produces water vapor, and does not generate toxic and harmful gases.
3. Preparation of alumina powder/ceramics
Hydrated alumina can be calcined at high temperatures to obtain α-Al2O3, with high thermochemical stability, thermal strength, creep resistance, dielectric properties, and low coefficient of thermal expansion, usually used to prepare alumina ceramics. It can also be used as a functional additive, widely used in various industries. In the process of ceramic synthesis, alumina hydroxide is activated, and the crystallization process is controlled so as to control the phase formation of the composite. By altering the procedure for the preparation of Boehmite precursor, The microstructure and the characteristics of the final product, alumina, can be controlled, and it has been one of the hot spots for research for the development of nano-alumina.
4. As a lithium diaphragm material
The many characteristics of nano-boehmite make it unique in the industry application of lithium electric diaphragm. Excellent thermal conductivity and flame retardant can effectively solve the problem of lithium battery diaphragm heat conduction to avoid spontaneous combustion and even explosion of the battery. Good hydrophobicity is conducive to improving the safety and stability of the battery. Its low hardness is conducive to reducing the cost of machining. It is worth mentioning that Boehmite has good compatibility with organic matter, so blending Boehmite with organic matter and applying it to lithium battery diaphragm materials has become a hot spot.
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