Electrical / Chemical
Nano-porous structures prepared by electrochemical anodisation of aluminium
D. Regonini, C.R. Bowen, D.Allsopp and R. Stevens
Materials Research Centre, Department of Mechanical Engineering, University of Bath, BA2 7AY, UK
Abstract
The anodising of aluminium has been investigated with the aim to realise nano-porous structures and nano-porous oxides for use as nano-templates, as gas-sensor systems and as catalysis. Before undergoing electrochemical oxidation, aluminium samples were cleaned in acetone, annealed at 500oC under nitrogen flow and electropolished using a mixture of perchloric acid, ethanol, 2-butoxyethanol and water. The pre-treated metal surface was analysed with a non-contact surface profilometer. The best pre-treatment results were achieved applying an electropolishing voltage between 50 and 60 V for a time of 20-30 sec. Anodising was carried out under potentiostatic conditions, using oxalic acid as electrolyte. Different combinations of processing parameters (anodisation time, cell temperature, number of anodisation steps) were used in order to optimise the process. Anodised alumina samples were characterised with scanning electron and atomic force microscopy. Partially ordered nano-porous alumina was obtained, however further investigations are required to optimise the production of highly self-ordered porous structures.
Different Influences on the ECF Process
K. Hofmann(a), H. Kück(a)(b) H. Ruoffc, L. Staemmler(b)
a: Institute of Micro- and Precision Engineering (IZFM), University of Stuttgart, 70569 Stuttgart, Germany
b: Hahn-Schickard-Institute for Micro Assembly Technology (HSG-IMAT), 70569 Stuttgart, Germany
c: Institute for Materials Testing, Materials Science and Strength of Materials (IMWF), 70569 Stuttgart, Germany
Abstract
Electrochemical milling with ultra short voltage pulses (ECF) is an innovative technique to machine electrochemically active materials at micrometer feature size, especially very hard materials like steel. The movement of the tool is similar to conventional milling, although it does not rotate. Therefore 3D-forming of the workpiece is possible. The surface of the workpiece is etched by a galvanic current. Due to this neither mechanical forces nor thermal loads are applied to workpiece or tool. The ability to manufacture hard materials like stainless steel at micrometer feature size makes ECF the ideal technique for processing micro moulds. When manufacturing moulds large differences in machining speed and quality of the surface occur. So far possible explanations for this were supposed differences between the machinability of grain boundaries and interior of the grains. But experiments showed no significant influence. Furthermore the dependence of the tool diameter on the working distance was determined. Experiments showed a decreasing working distance with increasing tool diameter. This phenomenon could also be explained theoretically. Finally the influence of the grade of hardness on the ECF process is investigated at the tool steel M 340.
KMPR Photoresist for Fabrication of Thick Microstructures
Chen-Han Lee, Kyle Jiang
Centre for Microengineering and Nanotechnology School of Engineering, the University of Birmingham Edgbaston, Birmingham B15 2TT, UK
Abstract
Presented in this paper is an investigation on using KMPR, a new negative tone photoresist, to build thick micromoulds for electroforming. Compared with SU-8 photoresist, KMPR has the advantage to be removed after electroforming metallic microcomponents. Detailed process of KMPR mould fabrication and stripping is presented and nickel electroforming has been performed using the KMPR moulds. The results are compared with SU-8 moulds and the strip-ability of KMPR is clearly demonstrated.
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Electrical / Chemical
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