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Aerosol deposition (AD) is a coating technique wherein particles are impacted onto a target substrate at reduced pressures, and supersonic particle impact velocities lead to coating consolidation. The limiting step in AD application is often not supersonic deposition operation, but aerosolization of powder particles with the proper size distribution; the translational impact velocity is strongly size‐dependent. It is demonstrated that by directly synthesizing particles in the gas phase, size‐controlled ceramic particles can be injected into AD systems. This in situ formation step obviates the need for particle aerosolization. Ultrasonic spray pyrolysis (USP) is applied to produce yttria‐stabilized zirconia (YSZ), and USP is directly coupled with AD to produce consolidated, thick, YSZ coatings on metal substrates. USP‐AD yields YSZ coatings on stainless steel and aluminum substrates with porosities <0.20, which grow to thicknesses beyond 100 μm. Aerodynamic particle spectrometry and electron microscopy reveal that the depositing particles are 200 nm–1.2 μm in diameter, though each particle is composed of nanocrystalline YSZ. Supporting computational fluid dynamics calculations demonstrate that the YSZ particle impact speeds are above 300 m s−1. Thermal conductivity measurements demonstrate that USP‐AD coatings have conductivities consistent with those produced from high‐temperature processes.
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A molecular dynamics study of the effects of velocity and diameter on the impact behavior of zinc oxide nanoparticles
Abstract Molecular dynamics simulations of particle impact have been conducted for a ceramic with mixed ionic-covalent bonding. For these simulations, individual zinc oxide (ZnO) nanoparticles (NPs) were impacted onto a ZnO substrate to observe the effects of impact velocity (1500–3500 m s−1) and particle diameter (10, 20, and 30 nm) on particle deformation and film formation mechanisms that arise during the micro-cold spray process for producing films. The study shows that a critical impact velocity range exists, generally between 1500 and 3000 m s−1, for sticking of the NP to the substrate. Results suggest that solid-state amorphization-induced viscous flow is the primary deformation mechanism present during impact. Decreasing particle diameter and increasing impact velocity results in an increased degree of amorphization and higher local temperatures within the particle. The impact behavior of mixed ionic-covalent bonded ZnO is compared to the behavior of previously studied ionic and covalent materials.
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- Award ID(s):
- 2102818
- PAR ID:
- 10452413
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Modelling and Simulation in Materials Science and Engineering
- Volume:
- 31
- Issue:
- 7
- ISSN:
- 0965-0393
- Page Range / eLocation ID:
- Article No. 075008
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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