Particle size and shape effects on the surface mechanical properties of aluminium coated with carbonaceous materials

Influence of particle size and shape of carbonaceous materials on the surface mechanical properties of Aluminium-1100 substrates is evaluated. The aluminium surface is impregnated with multiwalled carbon nanotubes (one dimensional), Graphene nanoplatelets (two dimensional) and graphite flakes (three dimensional) of various sizes. An electrical resistance heat assisted pressing technique was used for localised melting of the aluminium substrate followed by the mechanical impregnation of the carbonaceous materials. Surface mechanical properties of the so obtained surface composites were evaluated by microhardness and nanoindentation studies. A general observation is that the indentation hardness and Young’s modulus increase as the shape changes from three dimensional to one dimensional and also with the reduction in particle size. The maximum surface hardness achieved for each of these particles and the processing conditions at which the best properties are attained give insights into the prevailing hardening mechanisms. Raman spectroscopic analysis, which shows a variable shift and change in intensity ratios of the corresponding G, D and 2D bands, corroborates the experimental observations.