Novel Gas Phase Route Toward Patterned Deposition of Sputter-Free Pt/Al Nanofoils

This article reports a new approach toward fabrication and directed assembly of nanoparticulate reactive system (Nanofoils) on patterned substrates. Different from current state-of-the-art, gas phase electrodeposition uses nanoparticles instead of atoms to form densely packed multilayered thin films at room temperature-pressure. On ignition, the multilayer system undergoes an exothermic self-propagating reaction. The numerous contact points between two metallic nanoparticulate layers aid in high heat release. Sub-10-nm Platinum (Pt) and Aluminum (Al) particles are synthesized through cathode erosion of metal electrodes in a flow of pure nitrogen gas (spark ablation). Pt/Al bilayer stacks with total thickness of 3-8 & mu;m undergo self-propagating reaction with a 10.3 mm s(-1) wavefront velocity on local ignition. The reaction wavefront is captured using high speed videography. Calorimetry studies reveal two exothermic peaks suggesting Pt/Al alloy formation. The peak at 135 & DEG;C has a higher calorific value of 150 mW g(-1) while the peak at 400 & DEG;C has a 12 mW g(-1) exothermic peak. X-ray diffraction study shows reaction-products are cubic Al2Pt with small quantities of orthorhombic Al6Pt and orthorhombic AlPt2. Electron microscopy studies help draw a correlation between film morphology, bimetallic interface, nanoparticle oxidation, and self-propagating reaction kinetics that is significant in broadening our understanding towards nanoparticulate reactive systems.