Jef Roos

Electrochemical deposition: a method for the production of artificially structured materials

Abstract The potential of electrochemical deposition (ECD) as a production method for artificially structured materials is discussed. Compared with physical vapour deposition (PVD), ECD technology has some definite advantages. Its low cost, industrial applicability and its ability to produce structural features with sizes ranging from nanometres to micrometres have recently created increased interest in this technology for the production of artificially structured materials. The different ECD methods are briefly reviewed and some specific cases of artificially structured coatings produced by ECD, such as epitaxial multilayered material (Cu/Ni), amorphous material in combination with crystalline material (NiP x /NiP y ) and alternating hard and ductile materials (NiP x /Sn), will be highlighted. It will be shown that, by controlling the ECD conditions adequately, a wide range of artificially structured materials with respect to their constituent to their elements and their microstructural morphology may be produced.

Micro-Raman spectroscopy for the characterization of wear induced surface modifications on hard coatings

Micro-Raman spectroscopy can be a helpful tool in determining wear induced surface modifications due to its ability to identify compounds and measure internal stress in an area with a diameter as low as 1 pm. Micro-Raman spectroscopy is used here to characterize surface reactions, transfer layers and internal stress relaxation induced by wear processes for four different hard coatings: PVD TiN, solar beam oxidized TiN, CVD diamond and diamond-like carbon coatings. The Raman spectroscopic investigation of partially worn coatings has resulted in very specific information complementary to results that can be obtained with commonly used surface characterization techniques.

Electro-osmophoresis of a charged permeable microcapsule with thin double layer

Abstract An analytical study is presented on the effect of the electro-osmotic convection that occurs transversely to a porous membrane of a microcapsule in an unbounded liquid in response to an electric field. The electrical field is assumed to be uniform over distances comparable to the radius of the microcapsule and the microcapsule and pore surfaces are uniformly charged. The governing differential equations and boundary conditions for the fluid velocity and potential fields are developed. The fluid dynamics is handled by defining a stream function which depends on the potential difference across the membrane. The fluid flow through the membrane is described by the Brinkman or by the Darcy equation, depending on the value of the permeability of the membrane. To illustrate the relevance of the effect, the electroosmotic velocity was calculated for typical values of the dimensions and properties of polymeric microcapsules suspended in an aqueous solution. It was found that electro-osmosis can increase the electrophoretic velocity over and above the value given by the Smoluchowski equation by more than 100%.