Nanomechanical behavior of 3D porous metal–ceramic nanocomposite Bi/Bi2O3 films

The nanomechanical properties of three-dimensional (3D) porous metal/metal oxide composite (Bi/Bi2O3) films grown by direct current electrodeposition have been studied by nanoindentation at two different loading rates. The synthesized films exhibit a mixture of crystallographic phases of metallic Bi and α-Bi2O3, as evidenced by X-ray diffraction. An in-situ compaction of the sample during the nanoindentation assays has been observed. This in-situ compaction has an influence over both the hardness and elastic modulus of the material, being more important on the latter and, therefore, on the determination of the degree of porosity of the composite film. The influence of the loading rate on the mechanical properties has been investigated. In addition, time-dependent deformation processes (creep tests) have been also performed, revealing an anelastic behavior irrespective of the loading rate. From these creep tests, a viscoelastic non-Newtonian behavior of the sample is evidenced, which is well-described by a three-element Voigt model.