Platinum Metals Review - Volume 19, Issue 4, 1975

The economic use of noble metals as catalysts usually requires them to be in the form of extremely small particles, typically less than 100 Å in size. This article reviews methods for the preparation and characterisation of such particles, and their importance in catalysis. For certain limited classes of reaction, activity per unit of surface area is itself a function of particle size; possible bases for explaining this effect are discussed.

On gentle heating in air or in oxygen all six of the platinum metals develop thin tarnish films, visible or invisible, on their surfaces. On exceeding individual critical temperatures these films disappear, exposing clean metal, the change having the characteristics of a low-energy phase transformation. The mechanisms involved are examined in this survey and their effects on the stability, strength and surface reactivity of the platinum metals and their alloys are discussed.

In a paper presented to the American Chemical Society Symposium on Auto Emission Catalysts, held in Chicago in August, an investigation was described in which it was shown that, by careful selection of the position of the catalyst in the exhaust train and of the operating temperature, deterioration due to lead poisoning can be minimised. This article summarises the findings reported in the paper.

Thick-film, silver-palladium conductor compositions with improved mechanical properties have been developed in the Johnson Matthey Research Laboratories. These conductors are capable of retaining high adhesion strengths using tin-lead solder after prolonged storage at elevated temperature. This article is based upon a contribution to the Institution of Electronic and Radio Engineers’ Conference held at the University of Technology, Loughborough, in September.