Aluminum oxide Property

Melting point:

2040 °C(lit.)

Boiling point:

2980°C

Density 

3.97

vapor pressure 

17 mm Hg ( 20 °C)

refractive index 

1.765

Flash point:

2980°C

storage temp. 

Sealed in dry,Room Temperature

solubility 

Miscible with ethanol.

form 

powder

color 

White to pink

Specific Gravity

3.97

Odor

Odorless

PH Range

3.5 - 4.5

PH

7.0±0.5 ( in H2O)

Water Solubility 

INSOLUBLE

Crystal Structure

Trigonal

crystal system

Three sides

Merck 

14,356

Space group

R3c

Lattice constant

a/nm	b/nm	c/nm	α/o	β/o	γ/o	V/nm3
0.47589	0.47589	1.2991	90	90	120	0.2548

Exposure limits

ACGIH: TWA 1 mg/m3
OSHA: TWA 15 mg/m3; TWA 5 mg/m3

Dielectric constant

4.5（Ambient）

InChIKey

PNEYBMLMFCGWSK-UHFFFAOYSA-N

CAS DataBase Reference

1344-28-1(CAS DataBase Reference)

NIST Chemistry Reference

Aluminum oxide(1344-28-1)

EPA Substance Registry System

Alumina (1344-28-1)

Safety

Hazard Codes 

Xi,F

Risk Statements 

36/37/38-67-36/38-11-36

Safety Statements 

26-24/25-16-7-36

WGK Germany 

-

RTECS 

BD1200000

F 

3

TSCA 

Yes

HazardClass 

8

HS Code 

28181010

Hazardous Substances Data

1344-28-1(Hazardous Substances Data)

Toxicity

Chronic inhalation of Al2O3 dusts may cause lung damage.

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H225Highly Flammable liquid and vapour

H319Causes serious eye irritation

H336May cause drowsiness or dizziness

Precautionary statements

P210Keep away from heat/sparks/open flames/hot surfaces. — No smoking.

P261Avoid breathing dust/fume/gas/mist/vapours/spray.

P305+P351+P338IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.

Aluminum oxide Chemical Properties,Usage,Production

Description

The oxide of aluminum is Al2O3. The natural crystalline mineral is called corundum, but the synthetic crystals used for abrasives are designated usually as aluminum oxide or marketed under trade names. For other uses and as a powder, it is generally called alumina. It is widely distributed in nature in combination with silica and other minerals and is an important constituent of the clays for making porcelain, bricks, pottery, and refractories.

The crushed and graded crystals of alumina when pure are nearly colorless, but the fine powder is white. Off colors are due to impurities. American aluminum oxide used for abrasives is at least 99.5% pure, in nearly colorless crystals melting at 2050°C. The chief uses for alumina are for the production of aluminum metal and for abrasives, but it is also used for ceramics, refractories, pigments, catalyst carriers, and in chemicals.
Aluminum oxide crystals are normally hexagonal and are minute in size. For abrasives, the grain sizes are usually from 100 to 600 mesh. The larger grain sizes are made up of many crystals, unlike the single-crystal large grains of SiC. The specific gravity is about 3.95, and a hardness is up to 2000 Knoop.
There are two kinds of ultrafine alumina abrasive powder. Type A is alpha alumina with hexagonal crystals with particle size of 0.3 μm, density 4.0, and hardness 9 Mohs, and type B is gamma alumina with cubic crystals with particle size under 0.1 μm, specific gravity of 3.6, and a hardness 8. Type A cuts faster, but type B gives a finer finish. At high temperatures, gamma alumina transforms to the alpha crystal. The aluminum oxide most frequently used for refractories is the beta alumina and hexagonal crystals heat-stabilized with sodium.
Activated alumina is partly dehydrated alumina trihydrate, which has a strong affinity for moisture or gases and is used for dehydrating organic solvents, and hydrated alumina is alumina trihydrate.

History

The hexagonally closest packed α-Al2O3 modification is the only stable oxide in the Al2O3 –H2O system. Corundum is a common mineral in igneous and metamorphic rocks. Red and blue varieties of gem quality are called ruby and sapphire, respectively. The lattice of corundum is composed of hexagonally closest packed oxygen ions forming layers parallel to the (0001) plane. Only two-thirds of the octahedral interstices are occupied by aluminum ions. The structure may be described roughly as consisting of alternating layers of Al and O ions. The corundum structurewas determined in the early 1920s .

Physical properties

Regular aluminum oxide is white and has a chemical composition of approximately 95 % Al2O3, 1.5 % SiO2, less than 0.5 % Fe2O3, and 3 % TiO2. Because of very slow cooling in the Higgins furnace, the crystals of alumina are coarse, averaging 10 – 15mm in diameter.

Classifications

Four grades can be distinguished according to the content of calcined aluminium:
(i) Standard calcined aluminas with a sodium content of between 3000 and 7000 ppm wt. Na₂O.
(ii) Intermediate calcined alumina with a sodium content of between 1000 and 3000 ppm wt. Na₂O. The sodium content of this grade has been lowered by modifying the conditions of the precipitation of gibbsite or of the calcination.
(iii) Low-sodium calcined aluminas with a sodium content of between 300 and 1000 ppm wt. Na₂O. These aluminas are usually obtained by washing the precursor or by the extraction of sodium as a volatile compound with the mineralizer during calcination.
(iv) High-purity aluminas with an extra-low sodium content below 100 ppm wt. Na₂O. These aluminas obtained from an aluminum hydroxide produced by a process other than the Bayer process. The main applications for calcined aluminas are as feedstocks for refractories, glass and enamel, tiles and porcelain, and advanced ceramics. The diversity of applications for calcined aluminas can be explained by the wide range of properties: refractoriness, sinterability, chemical inertness in both oxidizing and reducing atmosphere and in both acid and alkaline media, hardness, wear and abrasion resistance, dimensional stability, high thermal conductivity, electrical resistivity, low dielectric loss and high permittivity, and high ionic conductivity in the case of beta-alumina.

Uses

Aluminum Oxide (Alumina) is the most widely used oxide, chiefly because it is plentiful, relatively low in cost, and equal to or better than most oxides in mechanical properties. Density can be varied over a wide range, as can purity-down to about 90% alumina-to meet specific application requirements. Alumina ceramics are the hardest, strongest, and stiffest of the oxides. They are also outstanding and with electrical resistivity and dielectric strength, are resistant to a wide variety of chemicals, and are unaffected by air, water vapor, and sulfurous atmospheres. However, with a melting point of only 2039°C, they are relatively low in refractoriness and at 1371°C retain only about 10% of room-temperature strength. In addition to its wide use as electrical insulators and its chemical and aerospace applications, the high hardness and close dimensional tolerance capability of alumina make this ceramic suitable for such abrasion-resistant parts as textile guides, pump plungers, chute linings, discharge orifices, dies, and bearings.

Industrial Manufacture

Monocrystalline aluminum oxide is a very high purity abrasive, produced directly from bauxite in a single-stage fusion . The preferred method employs a furnace feed consisting of bauxite, pyrite (FeS2) or sulfur, carbon, and iron borings. When subjected to fusion in the Higgins batch furnace, two immiscible liquids are formed as with regular aluminum oxide. However, in the present case very slowcooling of the upper liquid results in essentially pure, individual crystals of Al2O3 in a matrix of sulfides. After the pig has cooled and been crushed, the matrix is removed chemically and mechanically. This treatment releases alumina crystals in the range of sizes required by the industry.

Description

Aluminum(III) oxide is also called aluminum oxide. In mineral form it is called corundum and is referred to as alumina in conjunction with mining and aluminum industries. Alumina exists in hydrated forms as alumina monohydrate, Al₂O₃?H₂O and alumina trihydrate Al₂O₃?3H₂O. The geologic source of aluminum is the rock bauxite, which has a high percentage of hydrated aluminum oxide. The main minerals in bauxite are gibbsite (Al(OH)₃), diaspore (AlO(OH)), and boehmite (AlO(OH).

Chemical Properties

Aluminum is a combustible, light, silverywhite, soft, ductile, malleable, amphoteric metal.Vary according to the method of preparation. White powder, balls, or lumps of various mesh.Insoluble in water, dif- ficultly soluble in mineral acids and strong alkali. Noncombustible.

Chemical Properties

Aluminum oxide occurs as a white crystalline powder. Aluminum oxide occurs as two crystalline forms: α-aluminum oxide is composed of colorless hexagonal crystals, and γ-aluminum oxide is composed of minute colorless cubic crystals that are transformed to the α-form at high temperatures.

Physical properties

White and translucent hard material used as abrasive for grinding. Excellent electric insulator and also wear resistant. Insoluble in water and in strong mineral acids, readily soluble in strong alkali hydroxides, attacked by HF or NH₄HF₂. Owing to its corrosion resistance, in inert atmosphere, in molten metals such as Mg, Ca, Sr, Ba, Mn, Sn, Pb, Ga, Bi, As, Sb, Hg, Mo, W, Co, Ni, Pd, Pt, and U it is used as crucible container for these liquid metals. Alumina is readily attacked in an inert atmosphere by molten metals such as Li, Na, Be, Al, Si, Ti, Zr, Nb, Ta, and Cu. Maximum service temperature 1950°C

Physical properties

Al2O3 Colorless hexagonal crystal; refractive index 1.768; density 3.965 g/cm3 (at 25°C); mp 2072°C; bp 2980°C; insoluble in water α-Al2O3 Colorless rhombic crystal; mp between 2005 to 2025°C ; density 4.022 g/m3 ; hardness 9Moh γ-Al2O3 white microscopic crystal Al2O3•H2O colorless rhombic crystal; refractive index 1.624; density 3.014 g/cm3 Al2O3•3H2O white monoclinic crystal; refractive index 1.577; density 2.420 g/cm3 All forms are insoluble in water.

Occurrence

Occurs in nature in abundance; the principal forms are bauxites and laterites. The mineral corundum is used to produce precious gems, such as ruby and sapphire. Activated aluminas are used extensively as adsorbents because of their affinity for water and other polar molecules; and as catalysts because of their large surface area and appropriate pore sturcture. As adsorbents, they are used for drying gases and liquids; and in adsorption chromatography. Catalytic properties may be attributed to the presence of surface active sites (primarily OH^- , ^O2- , and Al³⁺ ions). Such catalytic applications include sulfur recovery from H₂S (Clauss catalysis); dehydration of alcohols, isomerization of olefins; and as a catalyst support in petroleum refining.

Characteristics

Aluminum Oxide (Alumina) is the most widely used oxide, chiefly because it is plentiful, relatively low in cost, and equal to or better than most oxides in mechanical properties. Density can be varied over a wide range, as can purity — down to about 90% alumina — to meet specific application requirements. Alumina ceramics are the hardest, strongest, and stiffest of the oxides. They are also outstanding in electrical resistivity, dielectric strength, are resistant to a wide variety of chemicals, and are unaffected by air, water vapor, and sulfurous atmospheres. However, with a melting point of only 2039°C, they are relatively low in refractoriness, and at 1371°C retain only about 10% of room-temperature strength. In addition to its wide use as electrical insulators and its chemical and aerospace applications, the high hardness and close dimensional tolerance capability of alumina make this ceramic suitable for such abrasion-resistant parts as textile guides, pump plungers, chute linings, discharge orifices, dies, and bearings.

Uses

Aluminum oxide is known as the mineral bauxite. Its main use is for the production of aluminum metal by electrolysis. It is also used in many other chemical reactions.

Uses

• As adsorbent, desiccant, abrasive,thickening and anti-caking agent;
• As filler for paints and varnishes;
• In manufacture of alloys,refractories, ceramic materials, electrical insulators and resistors, dental cements, glass, steel, artificial gems; in coatings for metals, etc.;
• As catalyst for organic reactions.
• As an insoluble carrier for mineral pigment, and is frequently mixed into mineral powder makeup. Because of its abrasive texture, many use these crystals to exfoliate and resurface the skin-particularly with Microdermabrasion.
• As a chromotagraphic matrix; originally called Brockmann aluminum oxide when used for this purpose.
• The minerals corundum (hardness = 9) and Alundum (obtained by fusing bauxite in an electric furnace) are used as abrasives and polishes;
• In manufacture of cosmetic products like blush, powder foundation, lipstick and facial cleanser.