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Alumina
2019-10-05

Alumina is a stable oxide of aluminum with the chemical formula Al2O3. It is also known as bauxite in mining, ceramics and materials science.

Properties: white solid which is insoluble in water, odorless, tasteless, extremely hard, easy to absorb moisture without deliquescence (burning non-hygroscopic). Amphoteric oxide, soluble in inorganic acids and alkaline solutions, almost insoluble in water and non-polar organic solvents; relative density (d204) 4.0; melting point 2050 ° C.

Storage: Sealed and stored dry. SCRC100009

Uses: used as analytical reagents, dehydration of organic solvents, adsorbents, organic reaction catalysts, abrasives, polishing agents, raw materials for smelting aluminum, refractory materials.

YISHANG -Alumina, Zhongshan Yishang Metal Products Co, Ltd

Main ingredient

Alumina contains the elements aluminum and oxygen. If the bauxite raw material is chemically treated to remove oxides of silicon, iron, titanium, etc., the product obtained is a high purity alumina raw material, and the Al2O3 content is generally above 99%. The mineral phase consists of 40% to 76% γ-Al2O3 and 24% to 60% α-Al2O3. γ-Al2O3 can be converted to α-Al2O3 at 950-1200 °C, and significant volume shrinkage occurs at the same time.


Chemical properties

Reacts with acid:

Al2O3 + 6HCl = 2AlCl3 + 3H2O

Al2O3 + 6H = 2Al + 3H2O

Reacts with molten alkali:

Al2O3 + 2NaOH == 2NaAlO2 (sodium metaaluminate) + H2O

React with alkaline solution:

Al2O3+ 2NaOH +3H2O = 2Na[Al(OH)4] (sodium tetrahydroxyaluminate)

Can also be abbreviated as: Al2O3 + 2OH = 2AlO2 (metaluminate ion) + H2O

Alumina is a typical amphoteric oxide.

Variants

There are many variants of Al2O3, the common ones are α, and the γ forms are all white crystals.

The corundum in nature is the most densely packed α-shaped hexagon, with melting point, high hardness, insoluble in acid and alkali, corrosion resistance and good insulation.

The aluminum hydroxide and the aluminum hydroxide or aluminum ammonium lanthanum are co-heated at 723K to obtain a γ-shape, which is insoluble in water, but has strong water absorption, strong adsorption capacity and catalytic activity.

The beta shape has ion conductivity and allows Na to pass.

 

Physical properties

InChI=1/Al.2O/rAlO2/c2-1-3

Quantity: 101.96 amu

Melting point: 2303 K

Boiling point: 3250 K

True density: 3.97 g/cm

Bulk density: 0.85 g / mL (325 mesh ~ 0) 0.9 g / mL (120 mesh ~ 325 mesh)

Crystal structure: Trigonal system (hex)

Solubility: insoluble in water at normal temperature

Conductivity: non-conductive at normal temperature

Al2O3 is an ionic crystal

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

YISHANG -Alumina, Zhongshan Yishang Metal Products Co, Ltd-1

Safety

Ingestion: low risk, easy to cause dementia, damage to children's intelligence

Inhalation : May cause irritation or lung damage

Skin : low risk

Eye: low risk

Use SI units and standard air and air pressures unless otherwise noted.

Quality inspection index

Lysate in water, % ≤0.5

Silicate qualified

Alkali and alkaline earth metals, % ≤ 0.50

Heavy metal (in Pb), % ≤0.005

Chloride, % ≤0.01

Sulfate, % ≤ 0.05

Loss of ignition, % ≤ 5.0

Iron, % ≤0.01

 

Main function

Overview

The main components of ruby and sapphire are alumina, which have different colors due to other impurities. Sapphire contains iron oxide and titanium oxide and is blue.

1. The content of alumina is the highest in the main component of the aluminum ore. Industrially, bauxite is purified to alumina by the Bayer process and then converted to aluminum by the Hall-Heroult process.

2 Aluminum reacts with oxygen in the air to form a dense aluminum oxide film covering the aluminum surface exposed to air. 3

3. Aluminum is a good conductor of electricity and heat. The crystal form of alumina is suitable for use as an abrasive material and a cutting tool because of its high hardness.

4. Alumina powder is often used as a vehicle for chromatographic analysis.

5. 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.

Information: The hardness of corundum powder can be used as abrasive, polishing powder, high temperature sintered alumina, called artificial corundum or artificial gemstone, which can be used to make diamonds in mechanical bearings or watches. 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. Calcination of aluminum hydroxide produces γ-. 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 a diamond luster. The density is 3.9 to 4.1 g/cm, 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, ferric 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 component of bauxite. White powder. With different crystal forms, α-Al2O3 and γ-Al2O3 are common. The corundum in nature is α-Al2O3, hexagonally packed crystals. The melting point of α-Al2O3 is 2015±15°C, the density is 3.965g/cm, the hardness is 8.8, and it is insoluble in water, acid or alkali. γ-Al2O3 is a cubic packed crystal, insoluble in water, but soluble in acid and alkali.

Vehicle

Alumina powder is often used as a vehicle for chromatography.

Manufacturing tempered glass

Information: The hardness of corundum powder can be used as abrasive, polishing powder, high temperature sintered alumina, called artificial corundum or artificial gemstone, which can be used to make diamonds in mechanical bearings or watches. 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. Calcination of aluminum hydroxide produces 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 a diamond luster. The density is 3.9 to 4.1 g/cm, 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, ferric 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 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 the oxide film can be enhanced by a process known as anodizing (anode anti-corrosion).

Bauxite

(Al2O3·H2O and Al2O3·3H2O) are the main minerals of aluminum in nature. After pulverizing, they are impregnated with high-temperature sodium hydroxide solution to obtain sodium metaaluminate solution; the residue is removed by filtration, the filtrate is cooled and aluminum hydroxide crystals are added. After a long time of stirring, 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-type alumina powder, and the mother liquor can be recycled. This method was invented by the Austrian scientist K.J. Bayer in 1888 and is still the main method of industrial production of alumina. It is called the Bayer method.

Alpha alumina

In the lattice of alpha alumina, oxygen ions are closely packed in hexagonal form, and Al is distributed symmetrically in the octahedral coordination center surrounded by oxygen ions. The lattice energy is very large, so the melting and boiling points are very high.Alpha alumina is insoluble in water and acid, also known as aluminum oxide industry, is the basic raw material for the production of metal aluminum;Also used for making various refractory bricks, refractory crucible, refractory tube, high temperature experimental instruments;It can also be used as grinding agent, flame retardant, filling material, etc.High purity alpha alumina is also used to produce synthetic corundum, synthetic rubies and sapphires.Also used in the production of modern large-scale integrated circuit board substrate.

Gamma alumina

Gamma-alumina is aluminum hydroxide in 140-150℃ under the environment of dehydration, industry is also called active alumina, aluminum glue.In its structure, oxygen ions are approximately piled up in the vertical center, and Al is irregularly distributed in the gaps of octahedron and tetrahedron surrounded by oxygen ions.Gamma-alumina is insoluble in water but soluble in strong acid or alkali solutions. When heated to 1200℃, it is completely converted into alpha alumina.Gamma-alumina is a porous substance with an internal surface area of up to hundreds of square meters per gram.Industrial products are usually colorless or pink microstrip cylindrical particles, good pressure resistance.It is commonly used as adsorbent, catalyst and catalyst carrier in petroleum refining and petrochemical industry.Industrial transformer oil, turbine oil deacidifier, also used for chromatography analysis;It is a neutral and strong desiccant in the laboratory, and its drying ability is no less than phosphorus pentoxide. After use, it can be regenerated and reused after heating for 6-8h under 175℃.

More than 90% of the world's alumina is produced by the bayer process. Most of it is used to make aluminium, but less than 10% is used for other purposes.

Electrolytic alumina

The main process of mass production of electrolytic aluminum is an electrochemical process of molten salt, which can be expressed as follows:

Molten salt electrolysis

Main reaction: Al ₃ ₂ O + 2 c -- -- -- - > 2 Al + CO ₂ write + CO write (1)

Anode 960 ~ 990℃ cathode

Side effects: AlF ₃ + C - Al + CF ₃ diction

3 nafalf ₃ + C - Al + NaF + CF ₄ + F ₂ (3)

NaF + C > Na + CF ₄ (4)

Beta alumina

There is also a beta Al ₂ O ₃, it have ionic conduction ability (Na will be allowed to pass), beta bauxite as electrolyte of sodium sulfur battery.Because of the large amount of energy stored per unit weight, the battery can discharge with large current, so it has a broad application prospect.The battery negative extremely molten sodium, the anode for sodium sulfide (Na ₂ Sx), electrolyte for beta bauxite (sodium ion conductor)

The battery has a temperature range of 620 ~ 680K, and its storage capacity is 3 ~ 5 times that of the lead battery.Made from beta Al ₂ O ₃ ceramic diaphragm caustic soda production, electrolytic salt water with high purity and pollution characteristics of small.

Abrasive alumina

Alumina is applicable to a variety of dry and wet treatment processes, can be any workpiece rough surface grinding fine, is one of the most economical abrasive.This sharp synthetic abrasive with water caltrop is second only to diamond in hardness, especially suitable for the use of strict requirements on iron pollution.Used for the roughest cutting, but also can be made into pebble shape for the size of the workpiece for processing, to achieve very low roughness.Because of its high density, sharp, angular structure, it is currently one of the fastest cutting abrasive.

Alumina is made of brown alumina by electrosmelting high quality bauxite, while high quality aluminate is used to produce powdered and white corundum.Their natural crystal structure makes them hard and fast to cut.At the same time, they are often used as the raw materials for consolidation and coating abrasive tools.

Alumina can be recycled many times, the number of cycles and material grade and specific process, most of the standard abrasive blasting equipment can be used.

Industrial scope: aerospace industry, automotive industry, consumer goods processing, casting/die-casting, OEM distributors, semiconductor industry and other fields.

Applicable process scope: surface plating, painting, glazing and coating of teflon pretreatment;Deburr aluminum and alloy products, remove pot fouling;Mold cleaning;Metal sandblasting pretreatment;Dry and wet grinding;Precision optical refraction;Grinding of minerals, metals, glass and crystals;Glass carving and paint additive.

Activated alumina

Technical indicators

Active alumina appearance: active alumina is white spherical porous particles, uniform particle size, smooth surface, high mechanical strength, strong moisture absorption, water absorption does not expand and crack to maintain the original state, non-toxic, odorless, insoluble in water, ethanol, has a strong adsorption of fluorine, mainly used in the area of high fluorine drinking water fluoride removal.

Activated alumina has a selective adsorption capacity for gases, water vapor and some liquids.After adsorption saturation, water can be removed by heating at about 175-315℃ and revived.Adsorption and resurrection can be performed multiple times.Besides being used as desiccant, it can also absorb the vapor of lubricating oil from polluted oxygen, hydrogen, carbon dioxide and natural gas.It can be used as catalyst and catalyst carrier and chromatographic analysis carrier.

Under certain operating and regenerative conditions, the drying depth of activated alumina can be as high as below -70 ℃ of dew-point temperature.

Ceramic role

Alumina is divided into calcined alumina and ordinary industrial alumina. Calcined alumina is a necessary raw material for the production of archaized brick, while industrial alumina can be used for the production of microcrystalline stone. In traditional glaze, alumina is often used for whitening.Because archaize brick and microspar were favored by the market, the amount of alumina also increased year by year.

Therefore, alumina ceramic in ceramic industry arises at the historic moment, alumina ceramic is a kind of Al ₂ O ₃ as the main raw material, ceramic material is given priority to with corundum crystal phase. Because of its high mechanical strength, high hardness, low dielectric loss at high frequency, high temperature and high insulation resistance, chemical corrosion resistance and good thermal conductivity and other excellent comprehensive technical performance advantages.


Applicable

The product can be used as a high fluoride drinking water fluoride agent (fluoride in large capacity), recycling paraffins in alkylbenzene production of fluorine remover, transformer oil acid regeneration agent, used as oxygen gas drying industry, textile industry, electronics industry, automation instrument wind drying and in industries such as chemical fertilizers, petroleum and chemical drying desiccant, purifying agent (dew point can be up to 40 degrees), dew point pressure swing adsorption (psa) in air separation industry can reach to 55 degrees.It is a kind of high efficiency desiccant with trace water depth drying.Very suitable for non - thermal regeneration plant.

1. nano alumina paste xz-l14 appearance of white powder.

2 nano alumina xz-l14 crystal phase &alpha phase.

3 nano alumina xz-l14 content % more than 99.9%.

4. Nano alumina xz-l14 average particle size (nm) 20±.5.


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