Development of next-generation oxidic ceramic fibres for the establishment of value chains within Europe
GLASER L. 1, RÜDINGER A. 1, HERBORN R. 1
1 Fraunhofer Institut für Silicatforschung, Zentrum für Hochtemperaturleichtbau, Würzburg, Germany
CMCs and thus also oxidic ceramic fibres are becoming increasingly important for the development of efficient, ecological and tailor-made industrial solutions today. The developments of the last few years have shown how fragile global relationships and over-dependence on individual manufacturers in only a few countries can be. For this reason, the aim of the EU project InVECOF (start 05/22) is the development of innovative value chains for European oxide ceramic fibres. In a period of 3 years, oxide-ceramic reinforcement fibres are to be developed, which can compete with the state-of-the-art fibres from Japan and the USA. In addition, work is also being done on the development of next-generation oxide fibres with improved thermomechanical properties.
The fibres in the InVECOF project are produced using a sol-gel process and a dry spinning process. They are based on various compositions such as corundum, mullite or YAG. Part of the project is also the upscaling of the developed spinning masses to the fibre pilot plant of Fraunhofer center HTL in Bayreuth, which was put into operation in 2022 for oxidic fibres. There, on 1300 square meters, spinning masses can be produced and spun in a dry spinning plant and then thermally treated on site. This thermal treatment (calcination & sintering) poses a particular challenge for oxidic ceramic fibres and in particular for the corundum fibres developed in InVECOF, among other things. One reason for this is the escape of chlorine and hydrogen chloride during pyrolysis when using chlorine-containing precursors, which leads to irreparable structural defects within the fibres. For this reason, a main focus of our research is to understand the chlorine effect during calcination using XRD, XRF and ion chromatography and to reduce the chlorine content as much as possible using different temperature profiles and different atmospheres during calcination. In this way, the handling of the fibres has already improved considerably. This has been quantified by means of tensile strength tests and determination of the porosity. Up to now, fibres with a tensile strength of 1500 MPa could be produced.