Phase Transformations in Ceramics: Science and Applications: Session II
Program Organizers: Pankaj Sarin, Oklahoma State University; Scott Mccormack, University Of California, Davis; Waltraud Kriven, University of Illinois at Urbana-Champaign; Theresa Davey, Bangor University; Sanjay V. Khare, University of Toledo
Wednesday 2:00 PM
October 12, 2022
Room: 408
Location: David L. Lawrence Convention Center
Session Chair: Waltraud Kriven, University of Illinois at Urbana-Champaign; Pankaj Sarin, Oklahoma State University
2:00 PM
Microstructural Evolution of Single Crystal CoTi2O5: A Study Combining Experiment and Simulation: Junyan Zhang1; Connor McNamara1; Animesh Kundu1; Helen Chan1; Jeffrey Rickman1; 1Lehigh University
A duplex structure of CoTiO3 and TiO2 can react to form single crystal CoTi2O5 during heat-treatment. The transformation nucleates at the surface and proceeds inwards along the bi-phase boundaries; hence the potential exists to exploit the starting structure as a template for the product phase. The CoTi2O5 morphology and degree of transformation with depth was studied as a function of heat-treatment time and temperature. The potential parameters that control the morphology and reaction rate of CoTi2O5 were examined. SEM (scanning electron microscopy) and EBSD (electron backscattered diffraction) microstructural images were used to create digital templates for simulation. The rate of growth both along, and perpendicular to the phase boundaries was modelled using a stochastic numerical simulation that solves the pertinent reaction-diffusion master equation. Simulated data were compared with the microstructure to identify the influence of physical parameters. The potential of using this knowledge in microstructural design was discussed.
2:30 PM
Single Crystal Growth and Characterization of Magnetic Ceramics Using the Laser Heated Pedestal Growth Process: Edward Hoffman1; Dolendra Karki1; Travis Olds2; Paul Ohodnicki1; 1University of Pittsburgh; 2Carnegie Museum of Natural History
Single crystal growth of magnetic ceramics will be discussed using laser heated pedestal growth (LHPG). The LHPG method has been adapted as a method for floating zone crystal growth to avoid contamination effects and prompt coherent growth. However, as with any floating zone crystal growth method, there are challenges for growth of homogeneous single crystal oxides which display incongruent melting due to the need to maintain stability of the growth interface and the desire to mitigate compositional segregation within the grown single crystal. In this work we explore feasibility for growth of magnetic ceramics single crystals of stoichiometric chemistry despite modest chemical segregation between the solid and liquid phase predicted at the solidification temperature. Samples prepared through LHPG are characterized using structural and magnetic property characterization methods, and subsequent annealing following single crystal growth is also explored to facilitate chemical homogenization and phase purity of single crystal samples.
2:50 PM
Study Toward Size Dependent Solid State Phase Transition between γ-WO3 and ε-WO3 via In Situ Cryogenic Raman Spectroscopy: Owen Abe1; Zanlin Qiu1; Zexu Chen1; Joerg Jinschek2; Pelagia-Irene Gouma1; 1Ohio State Universsity; 2Denmark Technical University
The low-temperature WO3 polymorph, ε-WO3, has been shown to function as a highly sensitive and selective gas sensor for the detection of acetone, an important biomarker for metabolic disorders, and as the foundational material for various chromic devices. Unfortunately, the kinetic and thermodynamic characteristics of the phase transformation between the room-temperature γ-WO3 and ε-WO3 phase as well as the thermostability of the ε polymorph is limited. Here, the low temperature phase transformation from γ-WO3 into ε-WO3 is studied by using in-situ Raman spectroscopy. The results provide insight into the size dependency nature of this phase transformation. Specifically, the transformation onset temperature between γ-WO3 and ε-WO3 is confirmed to be linearly proportional to reciprocal of average crystallite radius, which can be explained by several published thermodynamic models. [1] [1] O.O. Abe, Z. Qiu, Z. Chen, J.R. Jinschek, P.-I. Gouma, Ceramics International 2021
3:10 PM
Far-From-Equilibrium Processing of Materials with Swift Heavy Ions and Mechanical Milling: Eric O'Quinn1; Alexandre Solomon1; Casey Corbridge1; Antonio Fuentes2; Maik Lang1; 1University of Tennessee; 2Cinvestav Unidad Saltillo
The fabrication of next generation energy materials requires structurally resilient materials in far-from-equilibrium conditions. High energy ball milling and swift heavy ion irradiation are two extreme processing routes that rapidly deposit enormous amounts of energy to small sample volumes which yields intricate structural changes inaccessible through conventional synthesis techniques. Using simple, binary oxides (Ln2O3 with Ln = Gd - Yb) as a model system, we demonstrate the formation of a variety of defect structures and metastable phases accessible via these extreme processing conditions. The highly transient temperature and pressure regimes result in phase transformation pathways that can be adjusted by milling and ion-beam parameters. The induced material modifications strongly depend on the physics of interaction, and detailed characterization of the resulting structural changes over a wide range of experimental conditions present a fundamental first step to better understand and control matter far away from equilibrium.