ALUMINUM OXIDE - (1344-28-1)

Introduction

Name: aluminum oxide; aluminium oxide
* IUPAC
CAS Number: 1344-28-1
Chemical Formula: Al2O3
Molar Mass: 101.961276 g
Mass Percent: Al 52.925 %; O 47.074 % 

Classification

• inorganic

Uses/Function

• "Used as abrasive in sandpaper, sanding and cutting tools, and toothpaste. Large crystals with metal ion impurities often of gemstone quality. Inert support for chromatography. In fibrous forms, woven into heat-resistant fabrics; also used to strengthen ceramics and metals." 1

• "is widely used as a refractory and as a support for catalysts." 2

• "This material is extraordinarily hard, a property that leads to its use as the abrasive in grinding wheels, "sandpaper," and toothpaste." 3

• "The primary use of aluminum oxide is in the manufacture of aluminum metal. When an electric current is passed through molten (melted) aluminum oxide, the compound breaks down to form aluminum metal and oxygen gas. The method is called the Hall process after the American chemist Charles Martin Hall who invented it.

Aluminum oxide is also widely used as an abrasive. An abrasive is a very hard material used to grind, polish, sand, scour, scrub, smooth or polish some other material. Among the products that include aluminum oxide as an abrasive are emery boards, sandpaper, grinding and polishing wheels and belts, lens grinding devices, and gem polishing wheels.

The high melting point of aluminum oxide also makes it a good refractory product. A refractory product is one that does not melt easily, making it suitable for lining the inside of furnaces or the manufacture of glass and ceramic materials that will not melt when exposed to very high temperatures. Some other uses of aluminum oxide include:
• In finely-divided form, as the packing material in chromatographic columns. Chromatography is a process by which individual components of a mixture are separated from each other by passing them through a tube filled with some absorbent material (such as aluminum oxide).
• As a catalyst in many industrial chemical reactions.
• In the paper-making process, as a filler that adds body to the final product.
• As a food additives, where it acts as a dispersant, a substance that keeps a product from clumping together in a package; and
• As the internal coating on frosted light bulbs." 4

• "As adsorbent, dessicant, abrasive; as filler for paints and varnishes; in manuf[acture] of alloys, ceramic materials, electrical insulators, and resistors, dental cements, glass, steel, artificial gems; in coatings for metals, etc.; as catalyst for organic reactions. As a chromatographic 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 manuf[acture] of refractories." 5

• "Bauxite (mostly Al2O3) is the most important ore of aluminum. Another important ore is corundum, which also is a form of Al2O3) and is useful for its abrasive properties." 6

• "In contrast to ferric oxide, however, aluminum oxide (Al2O3) is very durable and tends to coat the surface, thus preventing corrosion." 7

• "Clear glass made from silica works well for windows in houses, but some material scientists have learned how to use aluminum oxide to make glass harder and to take advantage of optical characteristics like fluorescence and wavelength filtering.

Glass is a curious state of matter. It is not liquid or solid, but has properties of both. To make a glass, the trick is to prevent the substance from crystallizing into a regular solid, since the layers in crystal structures refract and reflect visible wavelengths rather than transmitting them. The relevant procedure requires cooling the molten liquid material fairly quickly-before it has the opportunity to form molecular crystal bonds.

While, in principle, any substance could be made into a glass, it is often not possible or economically feasible in practice, mostly because the necessary temperatures and pressures depend on the material and can be extreme in many cases. Scientists have recently found a way, however, to incorporate aluminum oxide with rare earth or calcium oxides to make a particularly resilient glass-one that does not easily deform upon impact. To deform a material uses energy, which means that momentum is not conserved in a collision. A material that minimizes such losses is useful in sporting equipment, such as golf clubs or baseball bats, designed to provide maximum rebound in collisions.

When allowed to crystallize, the alumina-rare earth oxide compounds are proving useful as extremely hard nanoscale ceramics. Transparent alumina films and fibers have also been produced by combining aluminum chloride with methyl cellulose, an organic composite.

8

• "In particulate form, aluminum oxide is used as an abrasive in emery board and sandpaper" 9

Physical Properties

Melting Point:*
2053°C 10 = 2326.15 K = 3727.4°F
Boiling Point:*
3000°C 10 = 3273.15 K = 5432°F
Density (g/cm3):
3.97 at room temperature/pressure 10
* - 1 atm pressure
‡ - approximate

Solubility

Qualitative:
insoluble:  10
slightly soluble: 10

Bonding

Bonding: ionic
Ionic Character: 55.45 %

Thermochemistry

ΔHf° (s alpha-corundum): -400.4 kcal/mol 11 = -1,675.27 kJ/mol
ΔHf° (s gamma-corundum): -396.0 kcal/mol 11 = -1,656.86 kJ/mol
ΔHf° (ℓ): -377.90 kcal/mol 11 = -1,581.13 kJ/mol
S° (s alpha-corundum): 12.17 cal/(mol•K) 12 = 50.92 J/(mol•K)
S° (s gamma-corundum): 14.3 cal/(mol•K) 12 = 59.83 J/(mol•K)
S° (ℓ): 21.41 cal/(mol•K) 12 = 89.58 J/(mol•K)
ΔGf° (s alpha-corundum): -378.1 kcal/mol 13 = -1,581.97 kJ/mol
ΔGf° (s gamma-corundum): -373.5 kcal/mol 13 = -1,562.72 kJ/mol
ΔGf° (ℓ): -358.33 kcal/mol 13 = -1,499.25 kJ/mol

Reactions

Safety Information

NFPA 704 Ratings:
Health: 1 - Exposure would cause irritation with only minor residual injury.
Flammability: 0 - Will not burn.
Reactivity: 0 - Normally stable, even under fire exposure conditions, and is not reactive with water.

For More Information

Wikipedia
Journals:
W. Buchberger, K. Winsauer, J. Chromatog. 482, 401 (1989)
M. T. Kelly, M. R. Smith, J. Pharm. Biomed. Anal. 7, 1757 (1989)
L. Sedel et. al., J. Bone Joint Surg. [Brit.] 72-B, 658 (1990)
L. P. Zichner, H.-G. Willert, Clin. Ortho. Rel. Res. 282, 86 (1992)
P. Boutin et. al., J. Biomed. Mat. Res. 22, 1203-1232 (1988)
P. S. Christel, Clin. Ortho. Rel. Res. 282, 10-18 (1992)

Sources

(1) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill: New York, 2006; p 569.
(2) - Swaddle, T.W. Inorganic Chemistry; Academic Press: San Diego, 1997; p 6.
(3) - Kotz and Treichel. Chemistry & Chemical Reactivity, 4th ed.; Thomson Brooks/Cole: Belmont, CA, 1999; p 1021.
(4) - Schlager, Neil, Weisblatt, Jayne, Newton, David E., and Montney, Charles B. Chemical Compounds Vol. 1; Thomson-Gale: Detroit, MI, 2006; pp 50-51.
(5) - The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 13th ed.; Budavari, S.; O'Neil, M.J.; Smith, A.; Heckelman, P. E.; Kinneary, J. F., Eds.; Merck & Co.: Whitehouse Station, NJ, 2001; entry 355.
(6) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 6.
(7) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 8.
(8) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 19.
(9) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 21.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4-39.
(11) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(12) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(13) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(14) - Kotz, John C., Treichel, Paul, and Weaver, Gabriela. Chemistry & Chemical Reactivity 6th ed.; Thomson Brooks/Cole: Belmont, CA, 2006; p 157.
(15) - Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 132.
(16) - Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 206.
(17) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 15.
(18) - Kotz, John C., Treichel, Paul, and Weaver, Gabriela. Chemistry & Chemical Reactivity 6th ed.; Thomson Brooks/Cole: Belmont, CA, 2006; p 166.
(19) - Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 132.
(20) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 8.
(21) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 18.
(22) - Atkins, Jones, and Laverman. Chemical Principles 6th ed.; W.H. Freeman and Company: New York, NY, 2013; p F94.