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UHTCs, which include carbides and borides of early transition metals with melting points exceeding 3000°C, face a critical limitation: low fracture toughness. This drawback restricts their use in environments characterized by thermal shocks and vibrations. To address this issue, carbon or silicon carbide fibres – either short or continuous – are added as reinforcements, resulting in UHTCMCs.

While continuous carbon fibres or fabrics provide superior mechanical properties, as demonstrated in our previous research, short fibres offer distinct advantages for industrial applications. These include lower production costs and greater adaptability to diverse fabrication techniques. However, current methods for incorporating short fibres, such as ball milling, colloidal processing, and tape casting, pose challenges. These methods often cause fibre damage, reduce fibre length, or rely on non-sustainable organic solvents. To overcome these limitations, my research focuses on developing a novel slurry infiltration process.

The first phase of this work involved creating a new fabrication technique that uses natural thickeners and a planetary mixer. This approach enables the production of thin (~100 µm), flexible, solvent-free sheets reinforced with 3–5 mm carbon fibres. These sheets are easy to handle and suitable for assembling homogeneous structures via Hot-Pressing [1]. The versatility of this process also allows to produce graded materials with varying fibres contents that can improve the oxidation resistance [2]. Moreover, it supports the production of complex structures with varying matrix compositions and geometries. Examples include vertically oriented sheets with improved bending properties, multilayer square plates with compositional gradients, and cylindrical or conical shapes fabricated through Hot-Pressing and pressure-less sintering. In collaboration with the University of Bayreuth, we explored the tribological properties of ZrB₂-based UHTCMCs produced using this process for friction applications. The results were promising, highlighting the potential of these materials for future automotive applications [3,4].

Despite the significant achievements to date, perhaps the most exciting aspect of this work is the versatility of the fabrication process. It can be adapted to various matrix compositions and reinforcement contents, broadening the range of potential applications for this technique.

Matteo Mor, PhD

CNR-ISSMC, Via Granarolo, 64, 48018 Faenza (RA)

Email: matteo.mor@issmc.cnr.it

Links:

[1]      https://doi.org/10.26599/JAC.2023.9220674.

[2]      https://doi.org/10.1016/J.JEURCERAMSOC.2024.01.099.

[3]      https://doi.org/10.1016/j.jeurceramsoc.2023.05.019.

[4]      https://doi.org/10.1016/J.JEURCERAMSOC.2024.06.005.