CMCs and thus also oxide ceramic fibres are becoming increasingly important today for the
development of efficient, ecological and tailor-made industrial solutions.
For this reason, oxide ceramic fibres, an essential component of CMCs, have become an important field
of research with great public interest. Two EU-funded projects on the development of oxide ceramic
fibres are presented below.

Developments in recent years have shown how fragile global relationships and overdependence on
single producers in a few countries can be. The aim of the EU project InVECOF (start 05/22) is therefore
to develop innovative value chains for European oxide ceramic fibres. Over a period of 3 years, oxide
ceramic reinforcement fibres are to be developed, that can compete with the most advanced 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 EuroStars project “Material Advancements for Solar Fuels Technology” (MAfoS) is developing
critical equipment and materials for the first industrial solar-to-fuel pilot plant. Concentrated solar
energy, water, CO2, and CH4 will be used to produce sustainable liquid fuel. A subfield of this project
includes the development of tubes made of high temperature oxide ceramic fibre composite (high
temperature CMC – ceramic matrix composite), which are used in a temperature range of 1200 °C1500 °C.

In particular, Fraunhofer Center HTL has the task of developing oxide fibres that exhibit very good thermomechanical properties above 1300 °C.
The fibres in both projects are produced using a sol-gel process followed by dry-spinning. They are based
on different compositions such as corundum, mullite or YAG and different dopants. Part of the projects
is also the upscaling of the developed spinning masses to the fibre pilot plant of Fraunhofer Centre HTL
in Bayreuth, which was commissioned in 2022 for oxide fibres. There, spinning masses can be produced
on 1300 square metres and spun in a dry spinning plant and then thermally treated on site. This thermal
treatment (calcination & sintering) is a particular challenge for oxide ceramic fibres. Therefore, it is
important to gain a comprehensive understanding of the complex processes in synthesis, ageing,
spinning process and thermal treatment through comprehensive analytics such as XRF, SEM, XRD and
DTA. In this way, the handling of the fibres has already been significantly improved. This was quantified
using tensile strength tests and the determination of porosity. So far, fibres with an average tensile
strength of1500 MPa (corundum) and 1600 MPa (mullite) could be produced