Abstract: A part is made of a composite material having an alumina matrix by impregnating a fiber texture with a fluid composition containing a liquid precursor of alumina, a thermoplastic resin, and a suspension of alumina powder, and subsequently convening the precursor into alumina. Additional solid fillers may be added to the impregnation composition. The impregnated fiber texture is preferably made by draping and molding plies that are pre-impregnated with said composition.

Abstract: A microwave antenna capable of operating at high temperature comprises at least one waveguide opening to the outside through an opening in a covering panel and including a tubular portion integrally formed with the panel, projecting inwards therefrom, and connected to the remainder of the panel around the opening, the panel and the integrated waveguide being made of a refractory composite material capable of ensuring microwave propagation and constituting a structural element capable of being raised to high temperature. The waveguide is filled with a refractory dielectric material such as an alumina-alumina type composite material.

Abstract: The apparatus comprises a waveguide having one end with an outside rim in the form of a test flange having a plane front surface defining a calibration plane and intended to be applied against a plane surface of a sample of material to be tested, a generator coupled to the waveguide to inject microwaves therein, and means for detecting the waves reflected by the material. At least the terminal portion of the waveguide including the test flange for application against the material to be tested at very high temperature is made of an electrically conductive refractory composite material, such as a carbon/carbon or a carbon/ceramic composite material.