Influence of surface roughness on the adhesion of elastic films

It is shown that a self-affine roughness at the junction of an elastic film and a hard solid substrate influences considerably the adhesion of the elastic film, especially for small roughness exponents H (H<0.5) and/or large long wavelength roughness ratios w/ξ with w being the rms roughness amplitude and ξ being the in-plane roughness correlation length. Analytical calculations of the local surface slope allows an estimate of the roughness effects on the adhesion energy more precisely than those presented in earlier works (especially for roughness exponents H<0.5). For weak surface roughness the elastic energy contribution is significant on the film effective surface energy Δγeff and on pull-off force for elastic modulus E in the range of GPa. Moreover, in the case of partial contact an estimation of the pull-off force shows that it strongly decreases with reducing contact area due to surface.

Influence of self-affine roughness on the detachment stress at an elastic-inelastic interface

This work concentrates on the influence of roughness on the detachment stress of an elastic body in contact to self-affine rough surfaces. It is shown that the self-affine roughness influences the detachment stress depending on the elastic modulus E and the details of the specific roughness. The roughness influence is more dominant for detachment lengths λ smaller or comparable to the in-plane roughness correlation length ξ, and low roughness exponents H (<0.5). The detachment stress as a function of the correlation length ξ shows a maximum for correlation lengths ξ>λ and low roughness exponents (H<0.5), while the correlation length ξ where the maximum occurs approaches the size of the detachment length λ with increasing roughness exponent H.

Variation of structure and magnetic properties with thickness of thin Co59Fe26Ni15 films

Variations of phase composition and magnetic properties of electrodeposited nanocrystalline Co-Fe-Ni films with film thickness in the range of 50-500 nm were analyzed. The samples were magnetically soft with coercivity in the range H-c = 2-20 Oe and uni axial magnetic anisotropy up to H-k = 20 Oe. It was found that H-c decreases and H-k increases with increasing film thickness. The BCC phase dominates at small film thickness up to about 80 nm and the FCC phase increases when the film growths to a larger thickness. The increase of FCC phase correlates with the improvement of the ultrasoft magnetic properties. &COPY; 2004 Elsevier B.V. All rights reserved

Cracks in nano-ceramic thin layers produced by laser treatments

Sol-gel derived thin nano-ceramic layers of TiO2 and Al2O3 are studied using scanning electron microscopy to reveal the microstructure and morphologies of the layers. The low-voltage scanning electron microscope with a field emission gun is equipped with an especially designed lens, where the specimen is placed at the location where the magnetic field is the largest. In such a way a maximum resolving power could be attained of 1.5 nm at 3kV accelerating voltage. The melt-spun layers were treated differently afterwards, i.e. by furnace and by laser curing. These heat treatments appeared to dictate the final morphologies of the layers to a large extent. Grain growth is observed for the furnace as well as the laser cured layers. The activation energy for grain growth of these layers is determined. Homogeneous dense layers may be obtained if the parameters in the curing process are selected adequately. If the parameters are chosen incorrectly, severely debonded layers may be obtained. Pre-heating the layers resulted in less blister formation. The mechanisms which may cause the layers to fail were examined in more detail.</p