TOWARDS MICROWAVE ABSORBING METAL-OXIDE NANOCOMPOSITES - THE PROBLEM OF METAL MATRIX REACTION/

Thermostable microwave absorbing materials are of considerable interes t for the applications with the tailored radar cross-section. Nanocomp osites metal (Co, Fe)-dielectric (Al2O3, Al(2)O(3)2SiO(2), 3Al(2)O(3)2 SiO(2)) prepared by sol-gel route have been studied by electron micros copy and Fe-57 Mossbauer spectroscopy. The relationships between the m icro/meso porosity, the composition and the state of the matrix precur sor and the metal particle size are discussed with emphasis on the oxi dation of nanoparticles. The size are discussed with emphasis on the o xidation of nanoparticles. Fe-based nanocomposites are obtained only u sing microporous host matrices. The interfacial reaction between iron nitrate solution precursor and host matrix promotes the formation of g amma-(Fe1-xAl9)(2)O-3 phase. The metal content is maximized by the use of highly concentrate iron solution and/or mixing with cobalt nitrate , in which case alloying particles are obtained.