Reactive Multilayer Foils with Controlled, Discontinuous Structures for Chemical Time Delays

Unmet Need
Self-propagating, exothermic reactions in powder compacts are commonly used as chemical time delays, but the performance of these delays is limited and environmentally hazardous materials such as lead oxide are often used. Vapor-deposited reactive materials (RMs) offer an alternative, environmentally friendly source for self-propagating reactions, but their propagation velocities are typically too high.  It would therefore be advantageous to provide a patterned RM with controlled breaks in the material that alter the reaction rate of the material.

Technology Overview
The inventors have developed a novel reactive material multilayer foil with a controllable chemical time delay. The invention presented here is a patterned reactive foil with controlled discontinuities in the foil.  For example, the inventors have developed patterned reactive foil by depositing the foil on a 2-dimensional mesh substrate, where the gaps in the reactive material follow the regular impressions or gaps in the underlying mesh.  Because slowing the rate of a reaction may result in inadvertently quenching the reaction, the inventors have also investigated the best mesh design for creating a reactive material with a chemical time delay.  The inventors have determined that the thickness of the substrate (size of the wire used to make the mesh), its thermal conductivity and heat capacity, and the spacing of the discontinuities in the reactive foil can be varied to control the time and the performance of the delay.

Stage of Development
The inventors have developed prototypes of these reactive materials and have refined the design to achieve slower propagation rates without quenching.
 

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