Synthesis of Non-Equilibrium Phases Through Thermomechanical Nanomolding
Abstract
Processing metals under non-equilibrium conditions is a powerful tool to manipulate atomic structure, phase selection and microstructure. Non-equilibrium phases are either achieved through suppressing required diffusion to reach equilibrium or through changing conditions from typical equilibrium conditions such as high pressure. Highly practical and widely used is rapid cooling as a technique to realize conditions far away from equilibrium. As the various processes to reach equilibrium such as topological fluctuations, self and interdiffusion, and ordering have different inherent time scales, the effectiveness of rapid cooling to synthesize non-equilibrium materials varies dramatically. An alternative and qualitative different approach to synthesize non-equilibrium materials is suggested by our recent highly surprising and potentially disruptive method to fabricate nanowires. The preliminary results suggest that this Òthermo-mechanical nanomoldingÓ (TMNM) is based on atomic diffusion, where individual atoms diffuse down a pressure gradient into a nanocavity forming high aspect ratio nanowires. Typical time scales for TMNM are ~10 sec at 50% of the melting temperature under a pressure of ~100 MPa. As atomic diffusion is ubiquitously present, TMNM offers itself as a general method for nanofabrication. Pre-liminary results suggest that the composition of the feedstock alloy can vary drastically from the composition of the nanowire and it appears that this variation scales with the diffusivities of the alloy constituents. This finding constitutes the basis for proposed research, to utilize the unique conditions during TMNM as a method to overwrite thermodynamic motifs and hence synthesize novel non-equilibrium materials. Therefore, fundamental research is suggested to explore through a set of specifically designed experiments in which cases and by how much the unique conditions of TMNM can override thermodynamics motifs such as phase selection, ordering, mixing, and de-mixing. Scaling experiment paired with comparisons of thermodynamic driving forces will be used to quantify the effectiveness of the unique conditions of TMNM to overwrite thermodynamic motifs and synthesis novel non-equilibrium materials. If the mechanism is indeed according to our hypothesis, it would provide a powerful toolbox to synthesize novel non-equilibrium materials beyond those that can be currently fabricated with rapid quenching methods. Even though proposed research is of a fundamental nature, it has likely disruptive technological impact which will be visible on the medium to long term time scale, specifically for the application focus of the US Army. For example, outcome of proposed research can be expected to enable novel capabilities in sensing, protection, power/energy storage and generation. This could be generally realized through utilization of the novel material nanofibers in composites or surface composites. Particular for non-equilibrium nanowires based on refractory elements, such composites can be expected to yield enhancement in protection and general mechanical response. Specifically for sensing, communication, and energy generation, expected outcomes of proposed research suggests Army relevant advantages. We envision that TMNM will enable a broad range of surface functionalization of structure materials. TMNM suggest itself as a technique to apply nanowire arrays on large surfaces where enhancement of functional performance can be achieved through larger surface area, the ability to dramatically alter composition during TMNM, and potentially the novel non-equilibrium material of the nanowires. Proposed research, which is fundamental in nature, advances science by providing insights into single crystal formation, yields novel non-equilibrium materials, suggests a path for technological exploration of such materials, and educate involved students in advanced materials fabrication and characterization...
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 13, 2023
- Source ID
- W911NF2310132
Entities
People
- Jan Schroers
Organizations
- Army Contracting Command
- United States Army
- Yale University