Research Project

Rapid, Exothermic Phase Transformations in Reactive Materials

We have investigated exothermic reactions in a variety of layered, material systems.

Over the last 15 years we have investigated exothermic reactions in a variety of layered, material systems that include Ni-Al, Zr-Al, Ti-Al, Pd-Al, Ni-Zr, Ni-Cu-Ti-Zr-Al, Nb-Si and Al/CuOx [1-13]. The layered materials are fabricated by either sputter deposition or mechanical processing and contain many alternating layers of materials that have high heats of mixing, such as Al and Ni or Nb and Si.  The individual layers range in thickness from a few nanometers to tens of microns, but each sample typically contains hundreds of these layers and has a total thickness between 10 and 100µm for sputter deposited foils and between 100µm and 10mm for mechanically processed materials.  If the reactant spacing is fine enough and the heat of reaction high enough the reactions can self-propagate at speeds ranging from 0.1 to 20 m/s, and they reach final temperatures as high as 1600 °C as shown in Figure 1.

Figure 1: (a) Photograph of reacting Ni/Al multilayer foil. The foil is 40 mm thick and approximately one inch on each side. Its reaction was initiated with a spark on the lower left side and is propagating radially outward at ~10m/s, reaching temperatures near 1900 K. (b) Cross-sectional TEM of a Ni/Al multilayer foil prior to reaction showing the nanoscale layers of Ni (dark) and Al (light) [6].

Figure 1: (a) Photograph of reacting Ni/Al multilayer foil. The foil is 40 mm thick and approximately one inch on each side. Its reaction was initiated with a spark on the lower left side and is propagating radially outward at ~10m/s, reaching temperatures near 1900 K. (b) Cross-sectional TEM of a Ni/Al multilayer foil prior to reaction showing the nanoscale layers of Ni (dark) and Al (light) [6].

Under funding from NSF, ARL, LLNL, ONR, Agilent and 3M we have studied and continue to study the microstructural, physical and chemical parameters that control the heat, ignition and velocity of these reactions. We use a variety of experimental tools including XRD, TEM [14], Differential Scanning Calorimetry [15-24], microcalorimetry, pyrometry [13], and ohmic heating [25].  Recently we have expanded this effort to include in situ microdiffraction experiments in conjunction with the groups of Professor Todd Hufnagel (JHU) and Sol Grunner (Cornell) [26-29] as well as Dynamic TEM with Dr. Geoff Campbell’s group at LLNL.  These unique efforts have demonstrated that the sequence of phase transformations found in a rapid, self-propagating reaction are quite different than those found in the same reaction if it occurs in a slow, controlled manner.  During these studies we also team with other research groups (Professor Omar Knio, Drs. Betsy Rice and Scott Weingarten (ARL) and Professor Michael Falk) to predict reaction behavior using analytical[6,29], numerical{30-35] and Molecular Dynamic [36] modeling tools.  The fact that the Molecular Dynamic studies can now simulate reactions on length and time scales that approximately match the length and time scales of the in situ characterizations provides a unique opportunity to study rapid formation reactions.  Lastly, we are actively engaged with researchers at UCSD and Georgia Tech to understand how these reactive materials behave under rapid loading conditions [37-40], particularly for the case of mechanically processed reactive materials [41-42].

In early 2000 my research group demonstrated that vapor deposited reactive foils can act as local heat sources for joining temperature sensitive materials and for igniting other reactions [43-50].  Thus, in 2001 I co-founded Reactive NanoTechnologies with Professor Omar Knio to pursue commercial applications and the company demonstrated bonding capabilities for multiple applications [51-57], many of which are described in a recent review of joining with reactive multilayer foils [58]. The company’s NanoFoil® product was cited in the President’s 2004 Strategic Plan for Nanotechnology, and won an R&D 100 Award and a NanoTech 50 Award in 2005.  The NanoFoil® and NanoBond® Technologies were recently acquired by Indium Corporation and continue to be developed and sold for joining application.

 

  1. T.W. Barbee, Jr. and T.P. Weihs, Ignitable, Heterogeneous, Stratified Structures for the Propagation of an Internal Exothermic, Chemical Reaction along an Expanding Wavefront, U.S. Patent 5,538,795, July 23, 1996.
  2. T.W. Barbee, Jr. and T.P. Weihs, Method for Fabricating an Ignitable, Heterogeneous, Stratified Structure, U.S. Patent 5,547,715, August 20, 1996
  3. T. P. Weihs, A. Gavens, M.E. Reiss, D. van Heerden, A. Draffin, and D. Stanfield, Self-Propagating Exothermic Reactions in Nanoscale Multilayer Materials, TMS Proceedings, 75, Feb., 1997 Meeting, Orlando, FL.
  4. Self-Propagating Reactions in Multilayer Materials, T. P. Weihs, chapter in Handbook of Thin Film Process Technology, edited by D.A. Glocker and S.I. Shah, IOP Publishing, 1998. (Invited Review)
  5. M.E. Reiss, C.M. Esber, D. Van Heerden, and T.P. Weihs, Self-propagating Formation Reactions in Nb/Si Multilayers, Mat. Sci. Eng. A.-Struct., A261, 217-222, (1999).
  6. A.J. Gavens, D. Van Heerden, A.B. Mann, M.E. Reiss, and T.P. Weihs, Effect of Intermixing on Self-Propagating Exothermic Reactions in Al/Ni Nanolaminate Foils, J. Appl. Phys., 87, 1255-1263, (2000).
  7. K.J. Blobaum, M.E. Reiss, J.M. Plitzko, and T.P. Weihs, Deposition and Characterization of a Self-Propagating CuOx/Al Thermite Reaction in a Novel Multilayer Foil Geometry, J. Appl. Phys., 94, 2915-2922 (2003).
  8. M.E. Reiss and T.P. Weihs, Method of Making Reactive Multilayer Foil and Resulting Product, U.S. Patent  6,534,194, March 18, 2003.
  9. T.P. Weihs, M.E. Reiss, O.M. Knio, D. Van Heerden, T.C. Hufnagel, and H.S. Feldmesser, Free-standing Reactive Multilayer Foils, U.S. Patent 6,736,942, May 18, 2004.
  10. J.C. Trenkle, J. Wang, T.P. Weihs, and T.C. Hufnagel, Microstructural study of an oscillatory formation reaction in nanostructured reactive multilayer foils, App. Phy. Lett., 87, 153108 (2005) (3 pages).
  11. R. Knepper, M.R. Snyder, G. Fritz, K. Fisher, O. Knio, and T.P. Weihs, Effect of varying bilayer spacing on reaction energy and kinetics in reactive Al/Ni multilayers, J. Appl Phy., 105, 083504  (2009) (9 pages).
  12. C.J. Morris, B. Marya, E. Zakara, S. Barron, G. Fritz, O. Knio, T.P. Weihs, R. Hodgin, P. Wilkins & C. May, Rapid initiation of reactions in Al/Ni multilayers with nanoscale layering, J. Phys. Chem. Solids, 71, 84–89 (2010).
  13. S. Barron and T.P. Weihs, Characterizing Reaction Heats, Temperatures and Velocities in Ni-Zr and Ni-Hf Multilayer Foils, in preparation for J. Appl. Phys.
  14. D. Van Heerden, A.J. Gavens, A.B. Mann, and T.P. Weihs, Metastable Phase Formation and Microstructural Evolution during Self-Propagating Reactions in Al/Ni and Al/Monel Multilayers, Mat. Res. Soc. Symp. Proceedings, Vol. 481, 533-8, edited by M. Atzmon, E. Ma, P. Bellon
Highlights from this Research
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