Platinum Metals Review - Volume 25, Issue 1, 1981

The development of a range of thick film platinum resistance temperature detectors is described and the method of manufacture of a cylindrical version by a highly automated route is outlined. These novel detectors comprise a film of platinum bonded to an inert ceramic substrate and protected from the environment by a ceramic glaze and the advanced version of this series shows stability in sealed probes to maximum rated temperatures as well as improved thermal stability relative to previous versions.

Regulations requiring strict control of nitrogen oxide emissions from automobiles come into force in 1981 in the United States. This has necessitated the development of new catalyst systems that are capable of controlling nitrogen oxide as well as hydrocarbon and carbon monoxide emissions from spark ignition engines. These devices are known as three-way catalysts. Johnson Matthey have developed catalyst systems based upon platinum and rhodium to meet the requirements and these have been certified for use on 1981 model year vehicles by a number of automobile manufacturers.

The effect of the cyclic stress intensity on the growth rates of fatigue cracks in the platinum metals in air can be predicted on the basis of established correlation equations. These suggest an inverse relationship between the growth rate of fatigue cracks in a material and its elastic modulus, and this has been experimentally confirmed for platinum and palladium and for a 30 per cent rhodium-platinum alloy. It may therefore be expected that ruthenium and rhodium have a higher resistance to fatigue crack growth than most other metals. Osmium and iridium may have absolutely the highest resistance to fatigue crack growth of all metallic materials. The effect of an evacuated test environment is also considered.

The successful development of gold and silver plating in 1840 led to a number of scientists turning their attention to the electrodeposition of platinum and palladium, but before commercially satisfactory processes could be established they met with considerable difficulties because of the insolubility of the anodes and of the complex nature of the chemical compounds of these metals.