Properties of Cobalt
Cobalt is one of the world's essential elements. Of all elements, 27 are essential to man. Cobalt is one of these. It has many strategic and industrial uses becomes VITAL to man as the central component of Vitamin B12. Cobalt has many uses based on several of its unique properties:
- Cobalt's High Temperature Melting Point (1493°C) and retains its strength to a high temperature - Cutting tools, superalloys, surface coating, high speed steels, cemented carbides, diamond tooling
- Cobalt is ferromagnetic (nickel and iron are as well) and retains this property to 1100°C, a higher temperature (Curie Point) than any other material - Alnico magnets, recording tape, soft magnetic materials, samarium cobalt, NdBFe + cobalt
- Cobalt Blue Coloring - in conjunction with silica, cobalt produces intense blue colours. Of all the uses of cobalt, the paint pigment represents the single largest use of cobalt. - Cobalt Blue in paints, glazes, enamels, etc.
- Cobalt is multivalent - Catalytic action is enhanced - OXO reaction, Fischer-Tropsch, oil desulphurisation, paint and ink driers, tyre adhesives
Cobalt is resistant to stress and corrosion at high temperatures and is used in the following ways:
- In the production of super alloys for the aerospace industry
- In the production of industrial gas turbines
- In the production of hard metals such as cemented carbides and diamond tooling for metal cutting
- As a pigment in commercial and industrial ceramics and glass, inks, plastics and paints
- In the production of magnets, chemicals and rechargeable batteries
Main Properties of Cobalt
Cobalt is a transition metal appearing in the first long period of the Periodic Table between iron and nickel. The ground state atom is s22s22p63s23d74s2
Cobalt is a shiny, grey, brittle metal with a close packed hexagonal (CPH) crystal structure at room temperature but which changes at 421°C to a face centred cubic form. The metal is rarely used as a structural material in the pure form but almost always as an alloy or a component of another system.
Physical Properties of Cobalt
With an atomic number of 27, cobalt falls between iron and nickel on the periodic table. The density of cobalt is 8.8 g/cm3 similar to that of nickel. Its thermal expansion coefficient lies between those of iron and nickel. At temperatures below 417°C cobalt exhibits a hexagonal close-packed structure. Between 417°C and its melting point of 1493°C, cobalt has a face-centered cubic structure.
The elastic modulus of cobalt is about 210 GPa (30 x 106 psi) in tension and about 183 GPa (26.5 x 106 psi) in compression.
Cobalt is also an important ingredient in other materials. In the nickel-base superalloys, cobalt (which is present typically in the range 10 to 15 wt%) provides solid solution strengthening and decreases the solubility of aluminum and titanium.
The role of cobalt in cemented carbides is to provide a ductile bonding matrix for tungsten-carbide particles. The commercially significant cemented carbides contain cobalt in the range of 3 to 25 wt%. As cutting tool materials, cemented carbides with 3 to 12 wt% Co are commonly used.
Cobalt is naturally ferromagnetic and provides resistance to demagnetization in several groups of permanent magnet materials including:
- Aluminum-nickel-cobalt alloys (in which cobalt ranges from about 5 to 35 wt%)
- Iron-cobalt alloys (approximately 5 to 12 wt%)
- Cobalt rare-earth intermetallics (which have some of the highest magnetic properties of all known materials).
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