(605d) A Purely Mechanical Approach to the Fabrication of Reactive Metal Laminate Powders

A new method of mechanically fabricating reactive laminate powders has been developed. Fabrication is a two-step process: first bulk reactive materials are fabricated by rolling elemental sheets of nickel and aluminum laminated sheets with bilayer thicknesses ranging from 8 μm to 0.75 μm. Then these sheets are ground in a commercial blender to produce laminate powders ranging in size from 850 μm to less than 53 μm. This fabrication method allows the particle size and reactant spacing to be varied independently. Powders fabricated by this method have a heat of mixing that varies with the reactant spacing and the average diameter of the powders. This variation is due to an uneven Ni:Al composition in the smallest powders after processing. When a powder's diameter approaches the size of the reactant spacing, some powders are Ni rich and others that are Al rich and shown by differential scanning calorimetry, differential thermal analysis and pycnometry. After fabrication, the Ni/Al laminate powders were packed in steel tubes with other metal powders such as tungsten, magnalium, (93% Al 7% Mg) or aluminum and swaged into fully dense compacts that are machinable. Both swaged and loose compacts were tested in a bomb calorimeter to determine the heat from oxidation in a pressured oxygen environment.