Understanding Unusual Amorphous-to-Crystalline Phase Transformations and Mechanical Resilience of Structural Ceramics Under Irradiation
Abstract
The objective of this proposal is to understand how irradiation initiates athermal amorphous-to-crystalline (a-to-c) phase transformations in structural ceramics, and the implications on mechanical resilience. Metal oxides and nitrides are widely used as structural ceramics, but their properties and performance - including thermal, electrical, electrochemical, and mechanical - are sensitive to atomic ordering and phase structures. While a-to-c phase transformations can conventionally occur through thermal annealing, other external stimuli such as irradiation can trigger a-to-c transformations at temperatures well below critical crystallization temperatures, to phases not typically accessible through thermodynamics alone, and which appear to possess surprising levels of mechanical resilience. However, the fundamental mechanisms of these irradiation-induced a-to-c transformations remain largely unknown. To harness the unique properties of athermal a-to-c transformations, there is a critical need to understand the underlying mechanisms. We will conduct systematic and fundamental studies on three model structural ceramic systems- aluminum oxide (Al2O3), zirconium oxide (ZrO2), and silicon nitride (Si3N4). Our approaches utilize an iterative loop project and we will elucidate the role of irradiation dose rate and electronic structure on phase evolution using systematic variations in irradiation conditions. Amorphous specimens will be synthesized by electrochemical anodization or chemical vapor deposition methods. Advanced analytical TEM will be used to characterize phases and ordering, including electron pair distribution function (ePDF) and atomic electron tomography (AET), which are emerging techniques for characterizing order-disorder transformations. The scientific outcome will be a mechanistic understanding of irradiation-induced a-to-c transformations in structural ceramics, bridging from the electronic structure scale to the mechanical behavior scale. More broadly, this work will enable researchers to harness the phase transformation to tailor materials characteristics and irradiation conditions to access unique metastable phase structures and mechanical behaviors. Further, since irradiation is almost universally understood to introduce disorder into materials, this project represents a paradigm shift around the use of irradiation to design and tailor materials structures and properties. This work is directly relevant to DEPSCoR Topic Area 7, which seeks to elucidate the mechanisms governing phase transformations, new means of manipulating them, and the creation of specific short-range orders in amorphous materials with unique mechanical characteristics.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 06, 2024
- Source ID
- FA95502310507
Entities
People
- Hui Xiong
Organizations
- Air Force Office of Scientific Research
- Boise State University
- Office of the Secretary of Defense