TiZr

Titanium/Zirconium null matrix alloy

TiZr cell for automatic sample changer

TiZr cell for automatic sample changer
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(Unrevised) extracts from a safety report by Rob Done

Composition

By weight, the alloy is made to the specification 52.5% Titanium / 47.5% Zirconium. Titanium has a bound coherent scattering length of -3.44 fm and Zirconium +7.16 fm. If these two elements are alloyed in the mass ratio Ti:Zr=7.16:3.44 i.e. 2.1:1 then the total coherent scattering length should equal zero.

In this composition the alloy exhibits excellent strength properties whilst retaining a high neutron transparency. Its appearance is similar to stainless steel.

Physical properties

Density = 5.23 g/cm³ = 0.542 atoms/Å3

Melting point = 1540 to 1575 °C

Chemical properties

Titanium/Zirconium metal is rapidly dissolved by hydrofluoric acid or hydrofluoric-nitric acid mixtures.

Above 200°C Zirconium reacts exothermically with halogen gases, fluorine, chlorine, bromine, iodine and halo-carbons, including carbon tetrachloride, Freons and Teflon.

The material can be used in most applications ranging from the manufacture of thin walled sample holders, through to pressure vessels at both elevated and cryogenic temperatures. Because of its low coherent neutron scattering qualities and its relatively high strength, the alloy is suitable for the construction of sample holders subjected to very high pressures, particularly for neutron diffraction experiments.

Titanium/Zirconium alloy does however have certain limitations to its use. Because of its intrinsic pyrophoric nature, there is a fire hazard associated with the processing of the material. Its maximum service temperature in air is 200°C, above which the alloy reacts with the gases present and there is a risk of it self igniting. Processes such as welding must be undertaken in a controlled atmosphere of Argon to prevent any such reaction.

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