Influence of Synthesis on the Mechanical Properties of sintered and nanoporous Copper

Indentation is a widely used destructive testing method to estimate mechanical properties of materials. Nanoindentation is a special indentation technique which can evaluate mechanical properties of materials at smaller dimensions, which traditional indentation tests fail to address. Nanoindentation can also accurately probe local mechanical property variation in the nanoscale. In this study we have used nanoindentation technique to examine mechanical properties of different forms of copper. Using a Berkovich indenter we have obtained  the hardness and modulus values of copper synthesized using Spark Plasma Sintering (SPS).  The variation in mechanical properties is discussed with respect to the initial copper powder sizes used in SPS for sintering, which can be related to the grain sizes observed in the sintered samples. The grain size is tied to the mechanical properties via the barriers of the plastic zone expansion.  We will explain the combination of sintering variables (pressure and temperature) used to synthesize dense copper pellets using SPS. In addition to bulk copper, we have evaluated the mechanical properties of copper nanofoam. The nanoporous Cu films are synthesized on a silicon substrate by electrochemical dealloying. The nanofoam behaves much differently than the bulk due to the high porosity volume fraction.  The nanofoam has a rough unequal surface, and therefore the average mechanical properties are obtained through a series of indentations.