Size and shape effects on the strength of platinum nanoparticles

Several previous studies demonstrated that defect-free faceted nanocrystals of face-centered cubic metals (such as Au, Ni and Pd) exhibit extraordinarily high mechanical strength approaching the theoretical strength of the respective metals. In the present work, we have studied the compressive strength of Pt nanoparticles fabricated by the solid-state dewetting method optimized for producing nanoparticles with a wide range of shapes and sizes. The particles exhibit a well-pronounced size effect on strength, with the smallest particles achieving the highest compressive strength of 9.5 GPa corresponding to the lower limit of the theoretical strength of Pt. However, the average strength of the Pt particles normalized by the respective shear modulus is significantly lower than that of Au and Ni nanoparticles fabricated by a similar dewetting method. We have also established a correlation between the particles strength and shape described by the ratio of the particle top facet and projected diameters. Smaller values of this ratio correlate with higher compressive strength. Based on the experimental data obtained, we formulate a power law describing the combined effect of the particle size and shape on its strength. Our results are in qualitative agreement with previous computational studies demonstrating that the theoretical strength of Pt normalized by its shear modulus is significantly lower than that of other face-centered cubic metals.