Pressureless Sintering of Powder Processed Graded Metal-Ceramic Composites Using a Nanoparticle Sintering Aid and Bulk Molding Technology
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The need exists to fabricate graded metal-ceramic composites in bulk manufacturing processes for commercial applications. To address this need, a three-fold approach is employed: (1) control of the evolution of shrinkage strain and mechanical properties through the use of a nanoparticle sintering aid, (2) modeling of shrinkage-induced stresses to determine gradient architectures where cracking does not occur, and (3) fabrication of graded metal-ceramic composites using pressureless sintering and bulk molding technology. A new nanopowder TiO2 sintering aid was introduced to control the evolution of shrinkage and mechanical properties of graded Nickel-Alumina composites. The evolution of shrinkage strain and mechanical properties were then used in a recently developed two-dimensional microthermomechanical finite element analysis to determine the effects on shrinkage-induced stresses and develop gradient architectures where cracking would not occur. Finally, a laboratory-scale processing system based on a commercial bulk molding technology was developed to bulk process geometrically-complex gradient structures.