Poly-Siloxane Impregnation and Pyrolysis of Basalt Fibers for the Cost-Effective Production of CFCCs

In this work, the optimisation of basalt fiber CFCCs (Continuous Fiber Ceramic Composites) production is presented, focusing on the development of a silicon-oxycarbide matrix by PIP (Polymer Impregnation Pyrolysis). The use of low cost poly-siloxanes and basalt fibers is particularly promising for transports and constructions, where thermostructural CFCCs would be interesting for vehicle weight reduction and fire-resistant panels, but only on the condition that production costs are kept really low. The basalt/SiCO composites are suitable for mechanical applications up to 600°C and stand up temperatures up to 1200°C, also in oxidative environments. The key parameters to keep the production costs low are the furnace and moulds type, being steel probably the best material for both, since it withstands the pyrolysis temperature and can be easily cleaned, by oxidation, from any residue. Regarding the pyrolysis environment, two conditions were compared, nitrogen flow and vacuum, being perhaps the vacuum procedure less expensive and so potentially more appealing for a large scale production. The microstructure and the thermomechanical characteristics of the obtained composites were compared. Another key parameter in determining the production costs is the number of PIP steps, which has to be minimised. The present results support the conclusion that one PIP step in nitrogen or two PIP steps in vacuum can provide CFCC with satisfactory mechanical characteristics for thermomechanical applications in oxidative environments.