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A B S T R A C T Graphite felts are often activated thermally before use in electrochemical reactors. This has the effect of improving wetting and decreasing charge-transfer resistance. In part I of this study, considerable variations were observed between two polyacrylonitrile (PAN)-based felts from different production charges after thermal activation, despite both charges being of the same type of felt from one supplier. A difference due to bulk crystallinity or due to pronounced core-rim structures of the fibres has been excluded. In this second part a limitation from tarry coatings, which are a possible side products of graphitization, could not be corroborated. However, differences were ascribed to variations in the surface chemistry, which was characterised by Boehm method titration and cyclic voltammetry. The composition of the oxides is discussed together with the possible role they play in the activation and wetting of the felts. The rather high amount of oxides suggests that the Boehm method measures subsurface groups in addition to surface groups. The wetting quality of activated felts can be correlated well with the concentration of neutral quinone groups, characterised by cyclic voltammetry.

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We present a unidimensional discrete solid-on-solid model evolving in time using a kinetic Monte Carlo method to simulate microstructuring of kerfs on metallic surfaces by means of laser-induced jet-chemical etching. The precise control of the passivation layer achieved by this technique is responsible for the high resolution of the structures. However, within a certain range of experimental parameters, the microstructuring of kerfs on stainless steel surfaces with a solution of H3PO4 shows periodic ripples, which are considered to originate from intrinsic dynamics. The model mimics a few of the various physical and chemical processes involved and within certain parameter ranges reproduces some morphological aspects of the structures, in particular ripple regimes. We analyze the range of values of laser beam power for the appearance of ripples in both experimental and simulated kerfs. The discrete model is an extension of one that has been used previously in the context of ion sputtering and is related to a noisy version of the Kuramoto-Sivashinsky equation used extensively in the field of pattern formation.