It has good fluidity, is insoluble in water, and dissolves in molten cryolite. It is the main raw material in the production of aluminum electrolysis.
Name alumina; corundum; white; red stones; sapphire; corundum; corundum
Chemical formula Al2O3
Appearance white crystalline powder or solid
Physical property
Quantity 101.96 amu
Melting point 2303 K
Boiling point 3250 K
Density 3.97 kg/m..
Crystal structure trigonal system (hex)
Thermochemical properties
ΔfH0liquid -1620.57 kJ/mol
ΔfH0solid -1675.69 kJ/mol
S0liquid, 1 bar 67.24 J/mol·K
S0solid 50.9 J/mol·K
safety
Low risk of ingestion
May cause irritation or lung damage by inhalation
Low skin risk
Low eye risk
Use SI units and standard air and air pressures unless otherwise noted.
Alumina is a compound of aluminum and oxygen and has a molecular formula of Al2O3. It is also known as bauxite in mining, ceramics and materials science.
Emergency treatment
Isolation of contaminated areas and restrictions on access. It is recommended that emergency personnel wear a dust mask (full face mask) and wear a protective suit. Avoid dusting, carefully sweep it, place it in a bag and transfer it to a safe place. If there is a lot of leakage, cover it with plastic cloth and canvas. Collected for recycling or transported to a waste disposal site for disposal.
preparation
Strongly hot aluminum hydroxide, an amorphous white alumina powder can be obtained. 2Al(OH) 3 → Al 2 O 3 +3H 2 O
use
1. The main components of ruby ​​and sapphire are alumina, which have different colors due to other impurities. Containing chromium oxide and ruby red, sapphire and the titanium oxide containing iron oxide and blue.
2. The content of alumina is the highest in the main component of the aluminum ore. Industrially, bauxite alumina purified by Bayer process, and then converted by the Hall-Heroult process is aluminum metal.
3. Alumina is the reason why metal aluminum is not easily corroded in the air. Pure metal aluminum reacts easily with oxygen in the air, creating a thin layer of aluminum oxide film that covers the aluminum surface exposed to air. This layer of aluminum oxide film prevents aluminum from being oxidized. The thickness and properties of this oxide film can be enhanced by a process known as anodizing (anode anti-corrosion).
4. Aluminum is a good conductor of electricity and heat. The crystal form of aluminum is suitable for use as an abrasive material and cutting tool because of its high hardness.
5. Alumina powder is often used as a vehicle for chromatographic analysis.
6. In August 2004, scientists working at 3M in the United States developed an alloy made of aluminum and rare earth elements to produce a tempered glass called transparent alumina.
The data corundum powder hardness can be used as abrasive, polishing powder, high temperature sintered alumina, called artificial corundum or artificial gemstone, which can be used as a mechanical bearing or a diamond in a clock. Alumina is also used as a high-temperature refractory material, refractory bricks, enamel, porcelain, artificial gems, etc., and alumina is also a raw material for smelting aluminum. Calcined aluminum hydroxide can produce γ-Al 2 O 3 . γ-Al2O3 has strong adsorption and catalytic activity and can be used as adsorbent and catalyst. The main component of corundum is α-Al2O3. Barrel or cone shaped cubic crystals. There is a glass luster or diamond luster. The density is 3.9 to 4.1 g/cm3, the hardness is 9, and the melting point is 2000 ± 15 °C. Do not dissolve in water, and are not soluble in acids and bases. High temperature resistance. Colorless and transparent, called white jade, reddish ruby ​​containing traces of trivalent chromium; blue sapphire containing divalent iron, trivalent iron or tetravalent titanium; dark gray, dark black with a small amount of triiron tetroxide Called corundum powder. Can be used as a precision instrument bearing, watch diamonds, grinding wheels, polishing agents, refractory materials and electrical insulators. Colorful jewels for decoration. Artificial ruby ​​single crystal can be used to make laser materials. In addition to natural minerals, it can be prepared by melting aluminum hydroxide with an oxyhydrogen flame.
Alumina chemical formula Al2O3, molecular weight 101.96. The main ingredient of bauxite. White powder. With different crystal forms, common are α-Al2O3 and γ-Al2O3. The corundum in nature is α-Al2O3, which is a hexagonal packed crystal. The melting point of α-Al2O3 is 2015±15°C, the density is 3.965g/cm3, the hardness is 8.8, and it is insoluble in water, acid or alkali. γ-Al2O3 is a cubic close-packed crystal, insoluble in water, but soluble in acids and bases, and is a typical amphoteric oxide.
Al2O3+6H+=2Al3++3H2O
Al2O3+2OH-=2AlO2-+H2O
Alumina preparation and application:
1. A method for producing an alumina film having an α-type crystal structure as a main body, an alumina film having an α-type crystal structure as a main body, and a film containing the same
2. Method for producing a-alumina powder
3. A method for producing a-alumina powder and α-alumina powder obtained by the method
4, a-alumina powder and production method thereof
5, a-alumina powder and its manufacturing method
6, a-alumina and its manufacturing method
7. Preparation method of α-alumina pellets
8. Preparation method of α-alumina nano powder
9, α-alumina fine powder and manufacturing method thereof
10. Method for producing alpha-alumina powder
11. Preparation method of β-alumina
12. Preparation method of γ-alumina
13. In-situ coated monolithic catalyst carrier for θ-alumina
14. Method for jointly producing alumina and calcium aluminate cement by Bayer process
15. Fluidization process of red mud water suspension in the process of alumina production by Bayer process
Aluminum is burned in the air and oxygen combines to form alumina. The chemical equation can be written as â–³
2Al+3O===Al2O3
CAS No.: 1344-28-1
EINECS accession number: 215-691-6
What is alumina
Pure alumina is a white amorphous powder, commonly known as alumina, density 3.9-4.0g/cm3, melting point 2050 ° C, boiling point 2980 ° C, insoluble in water, alumina mainly has two variants of alpha and gamma, industrially Can be extracted from bauxite.
Bauxite (Al2O3·H2O and Al2O3·3H2O) is the main mineral of aluminum in nature. It is pulverized and impregnated with high temperature sodium hydroxide solution to obtain sodium aluminate solution; the residue is removed by filtration, the filtrate is cooled and hydroxide is added. The aluminum crystal is stirred for a long time, and the sodium aluminate solution will be separated into precipitates of aluminum hydroxide; the precipitate is separated and washed, and then calcined at a temperature of 950-1200 ° C to obtain α-alumina powder, and the mother liquor can be recycled. This method was invented by the Austrian scientist KJ Bayer in 1888 and is still the main method of industrial production of alumina. It is called the Bayer method.
In the crystal lattice of α-type alumina, the oxygen ions are hexagonally packed closely, and Al3+ is symmetrically distributed in the octahedral coordination center surrounded by oxygen ions, and the lattice energy is large, so the melting point and boiling point are very high. Insoluble in water and acid, also known as aluminum oxide in industry, is the basic raw material for making metal aluminum; also used in making various refractory bricks, refractory concrete, refractory tubes, high temperature resistant experimental instruments; also as abrasives, flame retardants , fillers, etc.; high-purity α-alumina is also the raw material for the production of artificial corundum, artificial ruby ​​and sapphire; also used to produce the board base of modern large-scale integrated circuits.
Γ-type alumina is obtained by dehydrating aluminum hydroxide at a low temperature of 140-150 ° C. It is also called activated alumina and aluminum rubber in the industry. The oxygen ions in the structure are close to the vertical side and the Al3+ is irregularly distributed. Among the octahedral and tetrahedral voids enclosed by oxygen ions, γ-type alumina is insoluble in water, soluble in strong acid or strong alkali solution, and it is converted into α-alumina by heating it to 1200 ° C. alumina is a porous material, the internal surface area per gram up to several hundred square meters high adsorption capacity strong activity. industrial often colorless or slight pink cylindrical particles, pressure is good. in the petroleum refining It is a commonly used adsorbent, catalyst and catalyst carrier in petrochemical industry; it is industrial deacidizer for turbine oil and turbine oil, and is also used for chromatographic analysis; it is a neutral strong desiccant in the laboratory, its drying ability less than phosphorus pentoxide was heated 6-8h also repeated use below 175 ℃ after use.
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