| Aluminum foam is a porous form of solid aluminum. One method of producing aluminum foam is the powder metallurgy process. Aluminum powder is mixed with a foaming agent, generally titanium hydride (TiH2), and pressed to form a compact. In the foaming process, the compact is heated and hydrogen gas is released from the agent to form bubbles within the surrounding aluminum. However, there is a significant gap between the onset of the decomposition temperature of the TiH2 (400°C) and the melting point of aluminum (660°C). The hydrogen gas evolution begins while the aluminum is still solid, creating an accumulation of gas pressure which eventually causes microfissures inside the matrix. As a result, the final structure has interconnected pores and inferior properties.;Electroless plating is a process that can be used to deposit metallic coatings on non-conductive materials. Metallic ions in solution are reduced by a suitable agent, creating a metal deposit on the substrate. The process is autocatalytic and continues until all the metallic ions are consumed.;The objective of this work was to investigate the effect of the copper and nickel coatings on the hydrogen evolution of titanium hydride powders. It was found that the metal coatings do tend to delay the temperature of gas release and that this could potentially be used to improve the foaming process.;This problem may be overcome by delaying the temperature of hydrogen evolution so that it coincides with the melting point of aluminum. Coating the titanium hydride with copper or nickel can create a kinetic barrier that retards the flow of hydrogen into the surrounding matrix. |
