Low temperature annealing effects on magnetron sputtered Ni(V)/Al reactive coatings
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0908-OO14-26.1
Low temperature annealing effects on magnetron sputtered Ni(V)/Al reactive coatings a,*
M. P. Blickley
b
a
a
a
, N. A. Soroka , J. D. Demaree , J. K. Hirvonen and P. G. Dehmer
a US Army Research Laboratory, Aberdeen Proving Ground, MD, USA 21005 b US Military Academy, West Point, NY, USA 10996
ABSTRACT Reactive nanofoil coatings of magnetron-sputtered aluminum and nickel/vanadium bilayers were characterized for reliable debonding of segmented carbon composite or metallic structures to be used in future Army applications. We determined the initiation energies of multilayer stacks by discharging an electric spark from a fixed capacitor bank and varying DC voltage before and after low temperature annealing, which resulted in varying amounts of interfacial interdiffusion observable by Rutherford backscattering spectrometry (RBS). The propagation velocity of the reaction was also measured using high speed video photography. Significant increases in initiation energy and decreasing propagation velocities were observed with increasing anneal times and temperatures, in agreement with the RBS results and existing literature discussion of reaction mechanisms. Initiation sensitivity and propagation velocity were both impacted by varying the stoichiometric ratio of Al and Ni/V, and the propagation rate was also affected by the nature of the substrate. These results allow for the optimization of both reliable initiation and long term, low temperature storage stability of the final reactive coatings for debonding applications. INTRODUCTION Exothermic, self-propagating reactions of bimetallic nanolaminate materials have been studied for a variety of applications, including the synthesis of intermetallic compounds, the joining of dissimilar materials, and solder-free electronic module mounting.1-6 In particular, the US Army has investigated the use of such exothermic reactions for the development of functionally graded composite armor.7 More recently, the use of such exothermic reactions as debonding agents has been discussed. 8 Researchers at the Army Research Laboratory have shown that the insertion of commercially available freestanding nanolaminate foils of Ni/Al into an adhesive bonded composite structure will not affect the mechanical integrity of the structure, but when the reaction is initiated the adhesive bond will degrade, separating the components. In order to simplify the manufacturing and assembly process of such structures, it has been proposed that the nanolaminate coatings be deposited directly onto the components to be bonded, using dual-source magnetron sputtering. In this study, we demonstrate the deposition of such nanolaminate coatings directly onto two structural materials (carbon composite and stainless steel) and investigate the effect of annealing on both initiation sensitivity and propagation velocity. This allows us to assess the possible significance of thermal management during long-time depositions in vacuum, the use of annealing to reduce overly sensitive ignition, and the rel
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