Titanium-platinum (Ti50Pt50) (all compositions in at%) alloy exhibits thermoelastic martensitic phase transformation above 1000°C and has potential for high-temperature shape memory material applications. However, as has been previously reported, Ti50Pt50 alloy exhibited a negligible recovery ratio (0–11%) and low strength in martensite and especially in the austenite phase due to low critical stress for slip deformation. In order to improve the high-temperature strength and shape memory properties, the effects of partial substitution of Ti with other Group 4 elements such as zirconium and hafnium and the effect of partial substitution of Pt with other platinum group metals (pgms) such as iridium and ruthenium on the high-temperature mechanical and shape memory properties of Ti50Pt50 alloy were recently investigated. This paper reviews the transformation temperatures and high-temperature mechanical and shape memory properties of recently developed Ti site substituted (Ti,Zr)50Pt50, (Ti,Hf)50Pt50 and Pt site substituted Ti50(Pt,Ru)50 and Ti50(Pt,Ir)50 alloys for high-temperature (~800°C–1100°C) material applications.
Electrical resistivity values for both the solid and liquid phases of the platinum group metals (pgms) palladium and platinum are evaluated. In particular improved values are obtained for the liquid phases of these metals. Previous reviews on electrical resistivity which included evaluations for the pgms included those of Meaden (1), Bass (2), Savitskii et al. (3) and Binkele and Brunen (4) as well as individual reviews by Matula (5) on palladium and White (6) on platinum.
We review developments in the study of the stability of platinum-iridium standard weights, in particular the kilogram prototypes manufactured from alloy supplied by Johnson Matthey in the 1880s that still stand at the heart of the International System of Units (abbreviated SI from the French: Système international d’unités). The SI has long since moved on from length standards based on physical artefacts fabricated from this alloy, but the SI unit of mass is still defined in this way, as the mass of a real physical object. The stability of these reference masses has been a concern since the 1930s, with mass loss or gain at the surface being the principal concern. In recent years X-ray photoelectron spectroscopy (XPS) has been particularly valuable in elucidating the types of contamination present and the mechanism by which contamination takes place. While direct studies on the International Prototype Kilogram are understandably difficult, at Newcastle University we have examined the surfaces of six Pt mass standards also manufactured in the mid-19th century, using XPS to identify contamination chemically. XPS shows a significant quantity of mercury on the surfaces of all six. The most likely source of Hg vapour is the accidental breakage of thermometers and barometers, and the mechanism of contamination may be similar to the poisoning of platinum group metal (pgm) catalysts by Hg, an effect known for almost a century.
Having established that osmium is the densest metal at room temperature the question arises as to whether it is always the densest metal. It is shown here that at ambient pressure osmium is the densest metal at all temperatures, although there is an ambiguity below 150 K. At room temperature iridium becomes the densest metal above a pressure of 2.98 GPa, at which point the densities of the two metals are equal at 22,750 kg m–3.
