An investigation of sintering in electro exploded platinum nanopowder

Abstract

From literature, bulk platinum in the microscale (between 0.5 to 2 micrometers) [21] is known to exhibit sintering at 1000 degrees C or higher [22]. However, when reducing platinum metal to the nanoscale, the characteristics of platinum may exhibit changes in its physical properties. The purpose of this research was to investigate if sintering can occur at much lower temperatures when platinum metal was reduced to the nanoscale, in the form of wire exploded platinum nanopowder.

In order to achieve this, platinum nanopowder was first obtained using the electro exploding wire technique. Differential Scanning Calorimetry (DSC) was then used to characterise platinum nanopowder at different heating rates. At each heating rate, an exothermic peak was produced on the DSC graph. These exothermic peaks were identified, evaluated for its activation energy, and further characterised using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to identify if the exothermic peaks observed were due to the presence of sintering.

After the exothermic peaks were identified through DSC characterisation, one of the peaks was chosen, and a sample of platinum nanopowder was heated up to the temperature of the exothermic peak at its respective heating rate. SEM and XRD analysis were then used on the heated platinum nanopowder, as well as the original platinum nanopowder to analyse for differences in its physical structure.

From the SEM images produced, it suggests that sintering occurred after the platinum nanopowder was heated to the exothermic peak temperature. It also showed that there was a larger distribution of sizes of platinum nanoparticles as compared to the SEM image of the unheated platinum nanopowder.

XRD analysis was done to analyse for shifts in the peaks of XRD graphs obtained for both the unheated and heated platinum nanopowder (which indicates changes in the lattice parameter), as well as compare the differences between the average grain size and microstrain of the unheated and heated platinum nanopowder. However, the XRD analysis results were inconclusive, due to the degree of uncertainties present in the XRD data. It was concluded that perhaps an XRD machine with a higher resolution, as well as more experimental runs were needed to reduce the experimental error associated with this research.