Fabrication of complex-shaped alumina/nickel nanocomposites by gelcasting process

Complex-shaped Al2O3/Ni nanocomposites with preserved multifunctional magnetic properties are successfully fabricated by a gelcasting process. Based on an investigation of the effects of suspension composition on the drying, debinding, and reduction-pressureless sintering processes, a stable Al2O3/NiO binary oxide aqueous suspension with optimal monomer, dispersant, and solid composition is defined. Wet gelcast bodies produced using this suspension system shrink by 4.72% during humidity-controlled drying, with a bending strength of the fully dried green body of 3.84+/-0.84 MPa. The interconnected void structure of the debound green body provides hydrogen reduction of dispersed NiO without metamorphosis or shrinkage. Al2O3/Ni nanocomposites with complex shapes are successfully produced by pressureless sintering, and exhibit appropriate strength (586+/-50 MPa) after 21.5% shrinkage. Dispersed Ni particles exhibit typical ferromagnetic behavior in the Al2O3 matrix. This study confirms that gelcasting is a viable process for fabricating industrially applicable Al2O3/Ni nanocomposites with balanced mechanical and magnetic properties. (C) 2003 Elsevier Ltd. All rights reserved.