USE OF SOL-GEL CHEMISTRY FOR THE PREPARATION OF CYANOGELS AS CERAMIC AND ALLOY PRECURSORS

The reaction of aqueous solutions of K2PdCl4 and K3Co(CN)(6) results i n gellike polymeric materials, characterized by bridging cyanides betw een the central metals of the adducts. These materials tend to be rigi d in nature but contain in excess of 95% water by weight. We refer to these novel transition metal based hydrogels as cyanogels. In contrast to classic inorganic hydrogels these materials are not based on an ox ide network. Dehydration of the cyanogels results in amorphous xerogel s which maintain the initial polymeric structure of the cyanogel. Ther mal processing of gels containing palladium and cobalt centers under a n inert atmosphere at temperatures between 200 and 500 degrees C, prod uces a new metastable material. Sintering between 500 and 1000 degrees C produces ferromagnetic alloys, while processing under oxygen in the same temperature region gives the ceramic mixed oxide material PbCoO2 , having the delafossite structure.