Mechanisms for Film Formation During Room Temperature Micro Cold Spray of Ceramics

This grant advances the understanding of a recently discovered direct-write, additive manufacturing process for producing films. Additive manufacturing by direct writing is the process of producing a patterned film from a digital computer model without the need for a mask or other part-specific tooling. The technique has the potential to revolutionize the way things are made because it can dramatically lower the cost for making patterned films for low production volume parts or even allow custom geometries for each part.

There are many existing direct-write manufacturing processes that can produce patterned films. However, they generally require high temperature which can damage the substrate that the films are deposited on and this is particularly problematic for ceramic films since the processing temperatures are usually very high. This award supports fundamental research to provide needed knowledge for the development of a room temperature direct-write additive manufacturing process for depositing ceramics.

This process will enable the deposition of high-quality ceramic films at room temperature. Combined with metal films that can be deposited using the same process, these ceramic films can be use in hybrid devices that require multiple materials such as sensors, actuators, and rechargeable batteries. Therefore, results from this research will benefit the U.S. economy and society.

This research requires expertise in both experimental and computational materials science. The multi-disciplinary approach will train students in an areas that can contribute immediately to industry and outreach activities that will broaden participation of female engineering students in research and positively impact engineering education.

The micro cold spray process offers unique advantages compared to existing manufacturing processes for depositing thick films of metals and ceramics: 1) Deposition occurs at or near room temperature allowing for the use of film materials and substrates that are temperature sensitive; 2) It is possible to deposit oxygen-sensitive and very high melting temperature metals without highly specialized and expensive equipment; 3) Non-equilibrium mixtures of materials can be deposited onto a wide range of substrate materials with minimal surface preparation. However, experiments have shown that micro cold spray produces high quality ceramic films only over a narrow window of processing parameters.

The existing empirical approach was required because the mechanism(s) for particle bonding remain poorly understood. A fundamental understanding of the physics of film formation would allow the establishment of a processing window a priori that would dramatically reduce the number of experiments required to produce high quality patterned thick ceramic films using micro cold spray.

An understanding of the factors that affect film deposition by micro cold spray requires the study of new fundamental science to advance the manufacturing process because the combination of extremely high strain rates, large strains, primarily compressive stress states, and locally high temperatures that arise during particle impact for micro cold spray are unique in ceramics processing and have not been previously explored. This grant uses a combined experimental and molecular dynamics simulation-based approach to establish the scientific underpinnings advancing this manufacturing process and provides a fundamental understanding of the particle and agglomerate deformation mechanisms that lead to film formation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.