The interplay of crack hopping, delamination and interface failure in drying nanoparticle films

Films formed through the drying of nanoparticle suspensions release the build-up of strain through a variety of different mechanisms including shear banding, crack formation and delamination. Here we show that important connections exist between these different phenomena: delamination depends on the dynamics of crack hopping, which in turn is influenced by the presence of shear bands. We also show that delamination does not occur uniformly across the film. As cracks hop they locally initiate the delamination of the film which warps with a timescale much longer than that associated with the hopping of cracks. The motion of a small region of the delamination front, where the shear component of interfacial crack propagation is believed to be enhanced, results in the deposition of a complex zig-zag pattern on the supporting substrate

On the evolution of surface roughness during deformation of polycrystalline aluminum alloys

Surface roughening of polycrystalline Al-Mg alloys during tensile deformation is investigated using white light confocal microscopy. Materials are tested that differ only in grain size. A height-height correlation technique is used to analyze the data. The surface obeys self-affine scaling on length scales up to a correlation length which approximately equals the grain size and above which no height correlation is present. The self-affine scaling exponent increases initially with strain and saturates at a value around 0.9. A linear relation is observed between root-mean-square roughness and both strain and grain size. The observed roughness is explained as the result of the combined effect of a self-affine roughening on a subgrain scale and a grain scale roughening caused by orientation differences between neighboring grains. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

HREM INVESTIGATION OF AL-MGO INTERFACE

A metal-ceramic interface was produced by depositing Al on a (100) MgO substrate in a MBE system. The interface was studied with High Resolution Electron Microscopy. Results of some image simulations are shown, raising the question if effects of ionicity and charging should be taken into account

Metal-ceramic interfaces studied with high-resolution transmission microscopy

This paper reports on investigations of Ag-ZnO and Cu-ZnO interfaces, produced by internal oxidation. ZnO precipitates with the wurtzite structure were found showing mainly one orientation relationship( OR) with the matrix. However, closely related ORs were found, rotated by small angles from that orientation relation. The atomic structure of several interfaces surrounding these precipitates was studied and compared using high resolution transmission electron microscopy. This paper focuses on interfaces between low index facets of ZnO and vicinal planes of Ag. These interfaces clearly show relaxations. An interpretation of these relaxations in terms of dissociation of partial dislocations at the interface is put forward.</p