Equipment for ceramic-metal composites densification using SHS-reaction

Ceramic-metal composites have been obtained trough S.H.S.- reactions (Self-Propagating High Temperature Synthesis). The resulted material is normally porous and for their application as structural components it is necessary to produce them with high density. This can be carried out by the simultaneous application of mechanical pressure. For this aim, a pressing system and a reaction chamber were constructed. At high temperatures taking advantage of the material plasticity immediately after the occurrence of the reaction, a hydraulic system acts on the sample and compacts it. With this equipment it is possible to change pressure, atmosphere, pre-heating temperature of reactants, final sample dimensions and the delay time for the pressing action. A mold-punger set was specially developed to allow gas escape during pressing. Gases are generated due to S.H.S.-reaction and its removal is important for a successful densification. Alumina-zirconia-niobium composites were obtained from a niobia-aluminium S.H.S.- reaction with additions of zirconia as diluent. This work shows the evolution of the densification in the system mentioned above. (author)