Chemical Properties and Wide Applications of Aluminum Oxide

Chemical formula of aluminium oxide is Al₂O₃. Aluminium oxide is an abundant compound and stands for one third of the Earth's crust composition. It incorporates about 8% oxygen on its surface in the form of hydroxyl groups. This creates a very stable compound with high refractive power that is often used by optometrists to make glass lenses because they have low chromatic aberration or distortion: they also exhibit high resistance to corrosion as well as fracture under pressure, making them perfect for spectacle frames whose components are exposed to water at regular intervals (e.g., swimming goggles).

Physical properties of aluminium oxide

1. Molar mass: 50.468 g/mol

The molar mass of aluminium oxide is 50.468 g/mol. This is slightly less than the molar mass of oxygen (O₂) which, at 32 g/mol, is the most abundant element in our planet's crust and is estimated to be at least 23 per cent of all the Earth's crust. An indication of the high level of stability of aluminium oxide, however, is that it is never found in its natural state as an element and must be prepared by quite mild means. Aluminium oxide occurs naturally with oxygen in the form of a solid hydroxide (Al(OH)₃).

2. Density: 2.70 g/cm³

Aluminium oxide is a hard and brittle greyish-white or transparent powder that feels like sand when pressed between the fingers. It melts at 927℃and is quite deliquescent, forming an odourless hydrated complex, Al₂O₃·3H₂O, which is easily soluble in water. At standard temperature and pressure, it has a density of 2.70 g/cm³.

3. Hardness: 4.0

Aluminium oxide is hard and brittle (gold has a score of 2.5, glass about 5.5, diamond 10.0), but also quite tough and as a result does not fracture under pressure and can be used for deep-sea diving suits (these suits will not break when subjected to great pressure from the depth of the sea). Its hardness can be explained by the strong bonds between its atoms. In fact, in terms of hardness, aluminium oxide is less dense than most other common materials (lead and platinum are 2.2; silicon dioxide 6; coal 3; etc.).

4. Maximum achievable stress: 196 MPa

Aluminium oxide can withstand high pressures without breaking but is much more susceptible to chemical attack (such as hydroxy or hydroxyl attacks from dilute acids), and in this way would not be suitable for deep-sea diving suits. As a result, only abrasive materials such as diamonds and glass would not be able to be sufficiently dressed to the surface of the aluminium oxide unless they are modified by the addition of metals such as Pt, Pd or Ni. This is because aluminium oxide is insensitive to combination with other atoms (unlike silicon dioxide). This may be explained by chemical formula of aluminium oxide.

Uses of Aluminium oxide

1. As a pigment in paint

The most common usage for aluminium oxide is in the production of paints. Aluminium oxide provides colour variations to the white and black colours that are associated with different crystalline forms. When viewed from afar, these forms will appear either lustrous or dull and opaque depending on their colour composition. However, when viewed closely it will be observed that they look like irregularly shaped particles and are not shiny at all.

2. As a glaze in ceramics

Aluminium oxide is also used in the production of ceramic glazes. This is because aluminium oxide enhances the lustre and glassy appearance of these materials and thus creates a uniform surface that attracts most of the light that falls on it. This can be beneficial in making finished products with high-transparency such as windows, plates, etc.; or to create products with high gloss such as soaps, toothpaste and cosmetics.

3. As a refractory material in furnaces

Aluminium oxide is also used to make refractory bricks and furnace linings. These bricks are used in kilns and furnaces that are used in the ceramic industries as well as in glass-making. The reason for this is its high resistance to chemical attack; it is inert to most acids, as well as to oxidation, and is thus a very stable material for use in environments with reactive chemicals. It also does not absorb water easily (and because of this is one of the most common materials used for producing ceramic glazes). It has a melting point of 1170℃ however, so it must be fired at higher temperatures than other refractory materials.

In conclusions, chemical formula of aluminium oxide is Al₂O₃. Aluminium oxide is an abundant compound with refractive power and high hardness. It is often used as a raw material in production of many other products and also used as a pigment in paint.