A Cross-Disciplinary Investigation of Amorphous-Crystalline Ceramics Synthesized Using Far-From-Equilibrium Electromagnetic Excitations
Abstract
Overview: My objective is to understand how low-temperature, far-from-equilibrium effects of electromagnetic (EM) fields create phase transformations unavailable to conventional synthesis. Our preliminary research shows that selective heating of conducting layers (e.g., metal) inside a precursor solution by microwave radiation results in low temperature (< 200 oC) growth and crystallization of TiO2 thin films. Our synchrotron x-ray diffraction studies reveal that EM fields accessed a mixture of phases consisting of crystalline domains connected by locally ordered amorphous phases. TiO2 grown at similar temperatures in the furnace without microwave radiation was completely amorphous. High(> 500 oC) temperatures and post-sintering steps in conventional methods will likely re-crystallize the amorphous fractions, which could otherwise influence mechanical, electronic, and optical properties. However, it remains unknown if these phase mixtures arise merely due to equilibrium them1al motion or if phenomena, such as changes in the solid-state phase transformation temperatures, activation energy or frequencies of atomic/molecular vibrations and collisions, can emerge under EM excitation. Hypothesis and Approach: We hypothesize that accurately measuring local temperatures at the point of interaction of EM fields inside the material will be important to understand and control these EM field contributions. The novelty of our experimental approach lies in using thin films or particles of conducting materials (sensitizers) onto which EM field interactions can be selectively localized. This simple scheme enables us to investigate physical (temperature) and structural (crystallinity) properties at a specific reaction site (sensitizer surface) instead of a reaction taking place throughout a liquid medium. Our cross-disciplinary program will combine: (1) newly developed laser based thermoreflectance measurements; (2) time-resolved synchrotron x-ray studies; (3) microstructure analysis; (4) molecular dynamics simulations; and (5) coupled EM-thermal models to systematically identify and study thermal and non-thermal effects of localized EM fields. The resulting knowledge will help us progress towards a generalized theoretical model for how EM fields at different intensities, polarizations, and frequencies can synthesize advanced materials. Impact: The use of EM fields like microwave radiation during materials synthesis can provide an energy-efficient alternative to conventional high temperature thermal curing and sintering methods. The proposed study can thus impact the development of future manufacturing technologies that selectively manipulate EM fields to access phases, crystallographic alignment, microstructures, and properties not achievable through other means. These materials push the barrier between ordered and disordered structures to potentially enable several Army relevant technologies including high strength, light-weight, multifunctional protective armor, vehicles, and weapons.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2018
- Source ID
- W911NF1710589
Entities
People
- B. Reeja‐Jayan
Organizations
- Army Contracting Command
- Massachusetts Institute of Technology
- United States Army