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NICKEL

The basics: atomic number 28, atomic mass 58.69,
melting point 1455°C, boiling point 2913°C.

Nickel is located in the first transition series of metals
between cobalt and copper, in the same group as
palladium and platinum.

Nickel is a silvery metal which can be highly polished. It
is hard, relatively ductile and malleable. At room
temperature it has a face centred cubic crystal
structure.

Nickel is produced by nuclear fusion in stars and has
been identified in supernovae. 62Ni is the most stable
nucleide of all the elements and 78Ni is thought to play
an important role in the synthesis of elements heavier
that iron in supernovae explosions. Most of the Earth’s
nickel is in the core and it is thought that the nickel
deposits in the crust are the result of metallic meteor
impacts in the early part of the Earth’s geological history.

Nickel has been known since ancient times, though it is
thought that the first deliberate use of the metal dates to
20BC when it was used by the Syrians in bronzes.

Baron Axel Fredrik Cronstedt was the first person to
isolate nickel in the western world and he did this in
Stockholm in 1751. He was trying to extract copper from
the mineral niccolite but ended up with a silvery metal
instead. This is not entirely surprising as niccolite is
nickel arsenide! He named the new metal after the
mineral from which it originated, but the word nickel
actually derives from the German word Kupfernickel
which means Devil’s Copper.

Nickel is slow to react in air at room temperature allowing
it to be used in coinage which needs to have a long
service life. Like platinum and palladium, nickel is used
as a catalyst due to its corrosion resistance.

Nickel is one of only three naturally ferromagnetic
materials, the others being iron and cobalt. Although the
weakest of the three it has been used in AlNiCo magnets
for many years. These magnets are useful as they have
a high Curie Point and can safely be used up to a
temperature of 538°C. The Curie Point is the
This article appeared in
Issue 31 of the SAS
newsletter in Spring 2009.
temperature above which the material loses its magnetic
properties.

Commercial-purity nickel alloys contain at least 99.5%
nickel and are used for their good mechanical properties
and corrosion resistance in food processing equipment,
rocket and missile components, heat shields and heat
exchangers.

One of the most important used of nickel is as an alloying
addition in stainless steels, where is usually added at
between 8 and 10 wt%. The most widely used grade of
stainless steel is 304 which is often referred to as 18/8 as
it contains 18wt%Cr and 8wt%Ni.

Superalloys retain their strength, creep resistance and
corrosion resistance to temperatures around 70% of their
melting point and are based on nickel. They are used for
components such as blades and discs which operate
above 600°C in jet engines and where exceptional creep
resistance is needed the blades are grown as single
crystals.

Nickel-chromium alloys containing 7 to 30wt%Cr have
incredible high temperature oxidation resistance and are
used for electrical resistance wires for heating elements
and in thermocouples which operate up to 1100°C.

Copper-nickel alloys are extensively used because of
their good strength, ductility and corrosion resistance.
The alloys contain between 10 and 45wt%Ni and are
used for coinage, resistance wire, marine applications
and automotive applications.

Nickel silvers contain copper, up to 40wt%Zn and no
silver at all! They are used for electrical contacts,
coinage, camera parts, zips, guitar frets, clarinet keys
and musical instruments such as flutes and saxophones.

The nickel-iron alloy Invar has the lowest coefficient of
thermal expansion (CTE) of any metal or alloy at just
1.2ppm/°C. It is used in bimetallic strips alongside brass,
in the manufacture of cathode ray tubes as a shadow
mask and for electronic component frames as it can be
designed to have the same CTE as silicon.

Nickel is also used for electroplating other metals to give
a silver, corrosion resistant surface layer, as a catalyst in
the hydrogenation of vegetable oils to make margarine,
as the cathode in the form of nickel oxide hydroxide in
nickel-metal hydride batteries and as an alloying addition
to gold to produce white gold.

The alloy containing roughly equal parts of nickel and
titanium is known as Nitinol and this shape memory alloy
has found a large number of applications due to its
fatigue resistance, and the fact that it can demonstrate
the shape memory effect over a wide range of
temperatures.

When small amounts of copper and nickel are added to
glass they produce a green colour.