Reason: This article duplicates significant parts of a paper by the same author that had already appeared in Mater. Sci. Eng. C, 4 (1996) 69–82, doi:10.1016/0928-4931(96)00134-8. One of the conditions of submission of a paper for publication is that authors declare explicitly that the content of the paper has not been published elsewhere. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and we apologize to readers of the journal that this was not detected during the submission process.