Platinum Metals Review - Volume 57, Issue 3, 2013

Uniform dispersed spherical platinum particles were precipitated by reducing Pt(IV) hexaammine ([Pt(NH3)6]⁴⁺) complex ions with L-ascorbic acid in the presence of polymeric dispersants. By varying the nature and the amount of dispersing agent the average diameter of the Pt spheres could be adjusted between 200 nm and 800 nm. Electron microscopy and X-ray diffraction (XRD) evaluations revealed that the final Pt particles were the result of an irreversible aggregation of small (~6 nm) nanoparticles. The size of the constituent crystallites was controllably increased through a subsequent heat treatment process without affecting the shape or the dispersion of the Pt spheres. The method described represents a versatile and cost-effective route for producing Pt powders at the sub-micrometre or micrometre scale with controlled crystallinity for thick film electronic applications.

The crystallographic properties of osmium at temperatures from absolute zero to the experimental limit at 1300 K are assessed following a review of the literature published between 1935 and to date. Selected values of the thermal expansion coefficients and measurements of length changes due to thermal expansion have been used to calculate the variation with temperature of the lattice parameters, interatomic distances, atomic and molar volumes and densities. The data is presented in the form of Equations and Tables. The density of osmium at 293.15 K is 22,589 kg m⁻³.

In the present study polyvinylpyrrolidone (PVP) stabilised copper/palladium bimetallic nanoclusters were synthesised through chemical routes. The prepared Cu/Pd bimetallic nanoparticles were characterised by ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The UV-vis absorbance band confirmed the formation of complex metal ions triggered by the complexing agent trisodium citrate. The XRD pattern indicated the formation of bimetallic nanoparticles. The TEM images of the synthesised bimetallic Cu/Pd nanoparticles showed that the size distribution of the particles was in the range 5–15 nm. An acoustic particle sizer was then used to analyse the size distribution. The results obtained by the acoustic particle sizer were consistent with the XRD and TEM analyses. These results demonstrate the potential usefulness of the acoustic particle sizer for quick and easy characterisation of nanoparticles in various catalytic, sensor and fuel cell applications.