Aqueous solutions of acetate-functionalized alumina nanoparticles (A-alumoxane), with an average particle size of 28 nm, have been used as alumina precursors for the infiltration of porous alpha-alumina bodies in order to produce composite structures with homo-interfaces between substrate and infiltrate. Alternatively, if metal doped-methoxy( ethoxyethoxy) acetic acid-functionalized alumina nanoparticles (M-doped MEEA-alumoxane; M = Ca, Er, La, Ti, and Y), with an average particle size of 67 nm, are used in combination with A-alumoxane, a hetero-interface is formed between substrate and infiltrate. Samples were characterized by SEM, BJH, hardness and bend strength measurements. The bulk hardness of the alpha-alumina substrates increases with sintering temperature, but this increase is significantly smaller than the effect of infiltration. The composite hardness generally increases with decreased average pore size although the exceptions to this trend suggest that the identity of the infiltrate is of equal or greater importance. Overall the hetero-interfaces show higher strength than the homo-interface; the latter showing only slightly better performance than high temperature sintering. For the samples fired at 1000 degreesC, the MgAl2O4/Al2O3 and CaAl12O19/Al2O3 combinations appear to provide the greatest enhancement, with both the LaAl11O18/Al2O3 and Y3Al5O12/Al2O3 hetero-interface samples show marked increase in hardness between 1000 and 1400 degreesC. The elastic modulus and bend strength of the alpha-alumina substrate increases significantly for the Er6Al10O24/Al2O3 and LaAl11O18/Al2O3 infiltrates. The identity of the hetero-interface has a significant effect on the bulk properties of the composite. (C) 2003 Kluwer Academic Publishers.