Platinum Metals Review - Volume 55, Issue 4, 2011

To improve the high temperature properties, platinum can be hardened by solid solution and/or oxide particles. The investigated alloy, dispersion hardened platinum-5% rhodium (Pt-5%Rh DPH), was produced via melting and subsequent annealing of the semi-finished product in order to obtain an oxide particle dispersion. Despite the relatively large oxide particles formed in this process, the creep strength is much higher in comparison to conventional Pt-5%Rh. The aim of this paper is to study the strengthening mechanisms in the alloy Pt-5%Rh DPH by transmission and scanning electron microscopy. The size distribution of oxide particles shows a bimodal distribution, and the average oxide particle diameter is 315 nm for particles larger than 150 nm. For particles between 25 nm and 150 nm the average diameter is 49 nm. The size ranges of oxide particles are not substantially affected by high temperature creep deformation, but particles of <25 nm evolve during high temperature creep. It was found that all particles of different size ranges interact with dislocations and hence contribute to the strengthening of Pt-5%Rh DPH. Dislocation forests are pinned on the surface of oxide particles larger than 150 nm in diameter. Dislocation pile ups form between particles with a size range of about 500 nm. Medium size and small particles of diameters between 50 nm and 10 nm act as obstacles to single dislocations through backside pinning.

The species present in a variety of fresh and road aged light-duty diesel catalysts were determined by platinum L3 edge X-ray absorption spectroscopy (XAS). It was found that it is not sufficient to use the analysis of X-ray absorption near edge structure (XANES) alone to determine the nature of species present in fresh and road aged catalysts. Detailed analysis of the extended X-ray absorption fine structure (EXAFS) revealed the presence of a mixture of oxidic and metallic species in the fresh catalysts. Metallic components were predominantly found in the road aged catalysts. The present study did not find any chloroplatinate species in the systems investigated.

This review looks at the discovery and the discoverers of the thirty-eight known ruthenium isotopes with mass numbers from 87 to 124 found between 1931 and 2010. This is the sixth and final review on the circumstances surrounding the discoveries of the isotopes of the six platinum group elements. The first review on platinum isotopes was published in this Journal in October 2000 (1), the second on iridium isotopes in October 2003 (2), the third on osmium isotopes in October 2004 (3), the fourth on palladium isotopes in April 2006 (4) and the fifth on rhodium isotopes in April 2011 (5). An update on the new isotopes of palladium, osmium, iridium and platinum discovered since the previous reviews in this series is also included.