Micro-cold Spray of Thick Films

We are currently studying the micro-cold spray process (AKA aersosol depostion method or vacuum kinetic spraying) for producing thick films of metals and ceramics at room temperture.  Microcold spray utilizes nanometer to sub-micron powder particles as a feedstock. The particles are aerosolized and deaggomerated before accelerating them through a supersonic jet to velocities of 100-1200 m/sec and impacting them onto a substrate. By rastering the substrate beneath the jet nozzle, thick patterned lines can be directly written at high speeds and at room temperature. Compared to other processes, advantages of the microcold spray process include: 1) Nanostructured or amophous films from virtually any inorganic material can be produced 2) Highly non-equilibrium nanostructured composites can be deposited which exhibit unique and potentially advantageous properties 3) Films with thicknesses of more than 100 µm can be produced 4) Films can be patterned at high velocity and without the need for device-specific tooling 5) Since films are deposited at room temperature, polymeric substrates can be used and 6) the impaction velocities can be controlled, allowing films with a large range of densities to be produced.  We use a combination of experiments and molecular dynamics simulations to study the relationships between processing parameters and microstructur. The aim is to use these processes to direct-write high quality, micro-scale devices or films made from polymers, metals and ceramics.

Collaborators

• Michael Gammage, Army Research Laboratory

•Michael Becker, University of Texas at Austin

•John Keto, University of Texas at Austin

Current Post-Doctoral Researchers and Graduate Student Researchers

•Emmanuel Ekoi

•Stephen Bierschenk

•Liam McAuliffe

This work is currently supported by the US Army Research Laboratory, the National Science Foundation, DARPA, Sandia National Laboratories, and Los Alamos National Laboratory.

Publications

1. S. Burlison, M.F. Becker, and D. Kovar, “A Molecular Dynamics Study of High Velocity Impact of Zinc Oxide Aggregates,” Journal of Aerosol Science, 187 106582 (13 pages) (2025). DOI: 10.1016/j.jaerosci.2025.106582

2. S.  Bierschenk, M.F. Becker and D. Kovar, “Simulating the Effects of the Native Oxide Layer during Kinetic Spraying of Tantalum Particles using a Deep Learning Interatomic Potential,” Journal of Thermal Spray Technology, 34 pp. 1666–1684 (2025). DOI: 10.1007/s11666-025-01991-9 

3. R.F.P. Stone, M. Gammage, J. Wang, M. Cullinan, D. Kovar, and Z. Sha, “A Cooperative Framework for Multi-Nozzle Micro-Cold Spray Systems, Proceedings of the 35th Annual International Solid Freeform Fabrication Symposium, pp. 1153-1165. Austin, TX, August 11-14, 2024. Link.

4. T. Kothapalle, A.V. Melachuri, J.J. Rogers, B. Tran, M.F. Becker, and D. Kovar, “Simulation of High Strain Rate Contact of Single Crystal Al Spheres,” Computational Materials Science, 246 113415 (12 pages) (2024). DOI: 10.1016/j.commatsci.2024.113415 

5. S. Bierschenk and D. Kovar, “Micro-cold Spray Deposition of YSZ Films from Ultrafine Powders Using a Pressure Relief Channel Nozzle,” Journal of Thermal Spray Technology, in press, 2024. DOI: 10.1007/s11666-024-01813-4

6. S.  Bierschenk and D. Kovar, “A Nozzle Design for Mitigating Particle Slowing in the Bow Shock Region during Micro-Cold Spray of 8-YSZ Films,” Journal of Aerosol Science, 179 106360 (16 pages) (2024). DOI: 10.1016/j.jaerosci.2024.106360

7. A. Moyers, M.F. Becker, and D. Kovar, “A Strain Density Function to Analyze Particle Size Effects During High Velocity Impacts of Yttria,” Journal of the American Ceramic Society, 107 [6] pp. 3925-3944 (2024). DOI: 10.1111/jace.19708

8. T.V. Chitrakar, M.F. Becker, and D. Kovar, “Influence of Crystallographic Orientation on the Deformation of Ag Nanoparticles During High-Speed Impact,” Journal of Thermal Spray Technology, 32 pp. 2683–2700 (2023). DOI:10.1007/s11666-023-01664-5

9. S. Bierschenk, M.F. Becker, and D. Kovar, “Effect of an Oxide Layer on High Velocity Impact of Tantalum Particles Characterized using Molecular Dynamics,” Applied Surface Science, 640 158394 (15 pages) (2023). DOI: 10.1016/j.apsusc.2023.158394. 

10. S. Burlison, M.F. Becker, and D. Kovar, “A Molecular Dynamics Study of the Effects of Particle Velocity and Particle Diameter on the Impact Behavior of Zinc Oxide Nanoparticles,” Modelling and Simulation in Materials Science and Engineering,” 31 075008 (17 pages) (2023). DOI: 10.1088/1361-651X/acf060

11. S. Bierschenk, M.F. Becker, and D. Kovar, "Gas and Ceramic Particle Velocities for Micro-Cold Spray," Journal of Aerosol Science, 169 106113 (2023). DOI: 10.1016/j.jaerosci.2022.106113

12. T.V. Chitrakar, M.F. Becker, and D. Kovar, “A Quantitative Criterion to Predict Atomic Disordering During High Velocity Nanoparticle Impact,” Journal of Aerosol Science, 165 106042 (2022). DOI: 10.1016/j.jaerosci.2022.106042

13. D. Davies, A. Moyers, M.F. Becker, and D. Kovar, “Deformation and Film Formation Mechanisms During High Velocity Impact of SiC Nanoparticles,” Journal of Aerosol Science, 163 105997 (2022). DOI: 10.1016/j.jaerosci.2022.105997

14. A. Moyers, D. Davies, M.F. Becker, and D. Kovar, “Impact-induced Amorphization in Yttria Nanoparticles: A Molecular Dynamics Survey Study,” Journal of Aerosol Science, 162 105967 (2022). DOI: 10.1016/j.jaerosci.2022.105976

15. J.J.H. McCallister, M.D. Gammage, J.W. Keto, M.F. Becker, and D. Kovar, “Influence of Agglomerate Morphology on Micro-Cold Spray of Ag Nanopowders,” Journal of Aerosol Science, 151 105648, 2021. DOI: 10.1016/j.jaerosci.2020.105648.

16. M.F. Becker and D. Kovar, “A Quantitative Criterion for Predicting Solid-State Disordering During High Strain Rate Deformation, Journal of Physics: Condensed Matter, 33 (6) 065405, 2020. DOI: 10.1088/1361-648X/abc4ef

17. T.V. Chitrakar, G.J.J. Noiseau, J.W. Keto, M.F. Becker, and D. Kovar, “An Experimental and Computational Study of High-Speed Impact of Ag Nanoparticles,” Journal of Applied Physics,  125, 195104, (2019). DOI: 10.1063/1.5063345

18. J.J.H. McCallister, J.W. Keto,  M.F. Becker, and D. Kovar, “Influence of Normal Velocity on Microstructure and Density of Films Produced by Nanoparticle Impact,” AIP Advances, 9 035226 (2019). DOI: 10.1063/1.5080949

19. T.V. Chitrakar, J.W. Keto, M.F. Becker, and D. Kovar, "Particle Deposition and Deformation from High Speed Impaction of Ag Nanoparticles," Acta Materialia, 135 252-262 (2017). DOI: 0.1016/j.actamat.2017.05.062

20. J. Ma, M.F. Becker, J.W. Keto, and D. Kovar, “Laser Ablation of Nanoparticles and Nanoparticulate, Thick Fe1.92Tb0.3Dy0.7 Films,” J. Mater. Res., 25 [10], 1733-1740 (2010). DOI: 10.1557/JMR.2010.0234

21. C. Huang, E.-J. Yun, J. Ma, J. Keto, M.F. Becker, and D. Kovar, “Synthesis and Characterization of Permalloy Nanostructured Films by Deposition of Laser Ablated Nanoparticles,” J. Magn. Mag. Mater.321, 2537-2540 (2009). DOI: 10.1016/j.jmmm.2009.03.029

22. C. Huang, M.F. Becker, J.W. Keto, and D. Kovar, "Annealing of Nanostructured Silver Films Produced by Supersonic Deposition of Nanoparticles," J. Appl. Phys. 102, 054308 (2007). DOI: 10.1063/1.2776163

23. C. Huang, W.T. Nichols, D.T. O’Brien, M.F. Becker, D. Kovar, and J.W. Keto, “Supersonic Jet Deposition of Silver Nanoparticle Aerosols: Correlations of Impact Conditions and Film Morphologies,” J. Appl. Phys. 101, 064902 (2007). DOI: 10.1063/1.2710304 

24. A.D. Albert, C. Huang, M.F. Becker, J.W. Keto, and D. Kovar, “Deposition of Nanostructured Silver Lines and Films from Aerosols Produced by LAMA,” Proceedings of the International Symposium on Synergistic Effects of Materials and Processing (ISSEMP 2006), JSME No. 06-207, pp. 1-6, Japan Society of Mechanical Engineers, Kumamoto, Japan, September 19, 2006. 

25. J.W. Keto, M.F. Becker, D. Kovar, G. Malyavanatham, A. Muller, D.T. O'Brien, C.K. Shih, and J. Wang, "Nanoparticles of Er-Doped Glass Produced by Laser Ablation of Microparticles,"J. Opt. Soc. Am. B., 23 [8] 1581-1585 (2006). DOI: 10.1364/JOSAB.23.001581 

26. G. Malyavanatham, D.T. O'Brien, M.F. Becker, W.T. Nichols, J. W. Keto, D. Kovar, S. Euphrasie, T. Loue and P. Pernod, "Thick Films Fabricated by Laser Ablation of PZT Microparticles," J. Mater. Proc. Tech., 168 [2] 273-279 (2005). DOI: 10.1016/j.jmatprotec.2005.02.255 

27. M.F. Becker, J.W. Keto, and D. Kovar, “Nanoscale Manufacturing-Nonlinear Nanocomposites for Magnetostrictive Actuators and Photonic Devices,” 2005 NSF Design, Service and Manufacturing Grantees and Research Conference Proceedings, pp. 1-5, January 3-6, 2005, Scottsdale, AZ.

28. M.F. Becker, J.W. Keto, and D. Kovar, “Nanoscale Manufacturing-Nonlinear Nanocomposites for Magnetostrictive Actuators and Photonic Devices,” Proceedings of the 2004 NSF Nanoscale Science and Engineering Grantees Conference, pp. 1-3, December 13-15, 2004, Arlington, VA.

29. J. Ma, D.T. O’Brien, M.F. Becker, J.W. Keto, D. Kovar, “Nanoscale Manufacturing - Nanocomposites for Magnetostrictive Actuators,” 2004 NSF Design, Service and Manufacturing Grantees and Research Conference Proceedings, January 5-8, 2004, Dallas, TX.

30. J.W. Keto, W. Nichols, D. O'Brien, M.F. Becker, and D. Kovar, “Nanoparticles: Building Blocks for Nanostructured Materials,” From the Atomic to the Nano-scale, Proceedings of the International Workshop, C. T. Whelan and J. H. McGuire, Eds. (Old Dominion, 2003) pp. 54-62.