About Titanium

Titanium was discovered in 1790 by William Gregor, a Cornish cleric and amateur mineralogist.



Portrait of William Gregor (courtesy of Huntsman)


In 1791 he published his discovery of the presence of the oxide of an unknown metal found during his experiments on the black beach sands of Cornwall (ilmenite). In 1795 Martin Heinrich Klaproth, a German chemist, isolated a similar substance from ‘red schorl’ (rutile) from Hungary. He acknowledged Gregor’s prior discovery but named the new element titanium.

 ‘Wherefore no name can be found for a new fossil (element) which indicates its peculiar and characteristic properties, in which position I find myself at present, I think it is best to choose such a denomination as means nothing of itself and this can give no rise to any erroneous ideas. In consequence of this, as I did in the case of uranium, I shall borrow the name for this metallic substance from mythology, and in particular from the Titans, the first sons of the earth. I therefore call this metallic genus, titanium.’

It was to be over 100 years before MA Hunter, in the USA in 1910, isolated the pure metal and a potential industrial process for its production was not developed until 1932 by Dr Wilhelm Kroll.

Titanium may be truly called a space-age metal for had not its unique combination of properties, light weight and high strength been needed by the USA aerospace programme in the 1950s, it may have remained an interesting curiosity for metallurgists.
As can be seen in the following table, titanium fills a space between aluminium and iron in terms of weight but is as strong as steel and has a higher melting point.

Metal
Specific gravity
Melting point (deg.C)
Atomic number
Aluminium (Al)
2.7
660
13
Titanium (Ti)
4.5
1668
22
Iron (Fe)
8
1535
26
Copper (Cu)
9
1083
29
Silver (Ag)
10.5
960
47
Gold (Au)
19.3
1062
79

A quote from a speaker at the First International Titanium Conference held in London in 1968 emphasises just how new the metal was: ‘In 1941 virtually no metallurgist in the USA had seen a piece of ductile titanium, by 1948 a number had dealt with the mysteries of the metal.’

The commercial production of titanium started in the 1950s based on the Kroll process and developed rapidly. Production of titanium grew from 75 tons in 1951 to 6000 tons in 1957. However, as the USA space programme provided the impetus for the growth of titanium production, so the radical change in policy and consequent drop in demand caused a crisis, and, in 1958 the price of the metal dropped significantly. This put titanium within reach of other applications and its corrosion resistance proved particularly useful in the chemical process industries. The metal went from curiosity to commodity in 10 years and has suffered a cyclical demand pattern throughout the last five decades.

The late isolation and exploitation of titanium could be taken as an indication that it is a rare element but this is not so. Titanium is relatively abundant at 0.6 % of the earth’s crust and it is also present in the atmosphere of the sun and in interstellar space. It is the ninth most common element and the fourth commonest metal after aluminium, iron and magnesium. However it is very reactive and unlike gold, silver, copper and iron, it is never found as a pure metal. This very reactivity is why it is so difficult to isolate and process as a pure metal. Even today a batch method is used which makes production relatively slow and expensive. The first stage of the production is ‘titanium sponge’. An early decorative use of this material is a silver pendant, hallmarked 1963, by Malcolm Green, in the collection of the Worshipful Company of Goldsmiths, where the ‘sponge’ is set as an object.

The seeming paradox of a reactive metal being used as a corrosion-resistant element is explained by the fact that a thin, tough, protective oxide layer forms on the surface within minutes of its production, unless it is in an inert atmosphere. This layer, only a few nanometers thick, protects the metal from further attack. The further growth and manipulation of this oxide layer creates colour on titanium.

The colours produced on titanium are a manifestation of interference, a purely optical phenomenon, which depends solely on the thickness, transparency and the refractive index of the oxide layer.  Reaction with oxygen by the application of energy in the form of heat or electricity, i.e. anodising, thickens the very thin, air-formed film of oxide on the surface of titanium to produce a specific range of colours. The sequence of colours exhibited by this thin detergent film on polished metal ranging from ochre through purple, blue, silver, yellow, pink and purple to green are the same as those shown by titanium as seen in the anodised wire spirals and the chain bracelet and necklace.

Titanium jewellery by Lynne Bartlett, 2005
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