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Classification of alumina Al2O3

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Author : TRUNNANO
Update time : 2023-04-04 14:38:50
What is alumina?
Alumina (aluminium oxide) is an inorganic substance with the chemical formula Al2O3, a high hardness compound with a melting point of 2054°C and a boiling point of 2980°C. It is an ionic crystal that can be ionized at high temperatures and is commonly used in the manufacture of refractory materials.
Industrial alumina is prepared from bauxite (Al2O3-3H2O) and hard alumina, Al2O3 with high purity requirements, is generally prepared by chemical methods. al2O3 has many homogeneous hetero-crystals, more than 10 kinds are known, there are mainly 3 crystal types, namely α-Al2O3, β-Al2O3, γ-Al2O3. which have different structures and different properties, and are almost completely converted to Al2O3 at high temperatures above 1300℃. The structure of alumina is different and its properties are different, but it is almost completely converted to α-Al2O3 at a high temperature above 1300℃.
 
Characteristics of alumina
Aluminium oxide is a stable oxide of aluminium with the chemical formula Al2O3, also known as alumina in mining, pottery and material science.
Properties: white solid insoluble in water, odourless, tasteless, extremely hard, easily hygroscopic but not hygroscopic (burned not hygroscopic). Alumina is a typical amphoteric oxide (corundum is α-shaped belonging to the hexagonal most dense accumulation, is an inert compound, slightly soluble in acid and alkali corrosion resistance, soluble in inorganic acids and alkaline solutions, almost insoluble in water and non-polar organic solvents; relative density (d204) 4.0; melting point 2050 ℃.
Aluminium oxide storage: sealed and dry storage.
Alumina uses: used as an analytical reagent, dehydration of organic solvents, adsorbent, organic reaction catalyst, abrasive, polishing agent, raw material for smelting aluminium, and refractory material.
 
Classification of alumina
Al2O3 has many variants, the common ones are α, and γ types are white crystals. Corundum in nature is α type belongs to the hexagonal most dense accumulation, melting point, high hardness, insoluble in acid and alkali corrosion resistance, and good insulation.
Aluminium hydroxide and meta-alumina or alumino-ammonium alum at 723K cheat can be obtained γ type, insoluble in water, but strong water absorption, strong adsorption ability and catalytic activity. β form has ionic conductivity, allowing Na+ to pass.
 
α-type alumina
In the lattice of α-type alumina, the oxygen ions are closely packed, and Al3+ is symmetrically distributed in the octahedral coordination centre surrounded by the oxygen ions, and the lattice energy is very large, so the melting point and boiling point are very high, Filler, etc.; high purity alpha alumina is also the raw material for the production of artificial corundum, artificial ruby and sapphire.
 
γ-type alumina
γ-type alumina is produced by dehydrating aluminium hydroxide at a low temperature of 140-150℃, which is also called active alumina and alumina gel in industry. The structure of the oxygen ion is close to the centre of the vertical closely stacked, Al3+ irregularly distributed in the oxygen ion surrounded by octahedral and tetrahedral gaps. γ-type alumina is insoluble in water, and soluble in strong acid or strong alkali solution, it will be heated to 1200 ℃ will all be transformed into α-type alumina. γ-type alumina is a porous material, with an internal surface area of each gram of up to hundreds of square meters, high activity and strong adsorption capacity. Industrial products are often colourless or slightly pink cylindrical particles, with good pressure resistance. In the petroleum refining and petrochemical industry, it is a common adsorbent, catalyst and catalyst carrier; in industry, it is deacidified for transformer oil and turbine oil, and is also used for colour layer analysis; in the laboratory, it is a neutral strong desiccant, its drying capacity is as good as phosphorus pentoxide, and it can be regenerated and reused after being heated below 175℃ for 6-8h.
 
β-type alumina
There is also a kind of β-Al2O3, which has ionic conductivity (allowing Na to pass), with β-alumina as the electrolyte to make sodium-sulfur batteries. This kind of battery has a broad application prospect because of its large storage capacity per unit weight and its ability to carry out the high current discharge. The negative electrode of this battery is molten sodium, the positive electrode is sodium polysulfide (Na2Sx), and the electrolyte is β-alumina (sodium ion conductor). This battery can be used in the temperature range of 620-680K, and its storage capacity is 3-5 times that of a lead battery. Caustic soda is produced by using β-Al2O3 ceramic as a diaphragm for the electrolysis of salt water, which has the characteristics of high product purity and low pollution.
 
Alumina high purity white powder Al2O3 powder supplier
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