7 research outputs found
Observing and modeling the sequential pairwise reactions that drive solid-state ceramic synthesis
Solid-state synthesis from powder precursors is the primary processing route
to advanced multicomponent ceramic materials. Designing ceramic synthesis
routes is usually a laborious, trial-and-error process, as heterogeneous
mixtures of powder precursors often evolve through a complicated series of
reaction intermediates. Here, we show that phase evolution from multiple
precursors can be modeled as a sequence of pairwise interfacial reactions, with
thermodynamic driving forces that can be efficiently calculated using ab initio
methods. Using the synthesis of the classic high-temperature superconductor
YBaCuO (YBCO) as a representative system, we rationalize how
replacing the common BaCO precursor with BaO redirects phase evolution
through a kinetically-facile pathway. Our model is validated from in situ X-ray
diffraction and in situ microscopy observations, which show rapid YBCO
formation from BaO in only 30 minutes. By combining thermodynamic modeling
with in situ characterization, we introduce a new computable framework to
interpret and ultimately design synthesis pathways to complex ceramic
materials
Method for Cross-sectional Transmission Electron Microscopy Specimen Preparation of Composite Materials Using a Dedicated Focused Ion Beam System
Direct 3D (S)TEM Observation at Specific-site and High Resolution Using a FIB Micro-sampling Technique
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Observing and Modeling the Sequential Pairwise Reactions that Drive Solid-State Ceramic Synthesis.
Solid-state synthesis from powder precursors is the primary processing route to advanced multicomponent ceramic materials. Designing reaction conditions and precursors for ceramic synthesis can be a laborious, trial-and-error process, as heterogeneous mixtures of precursors often evolve through a complicated series of reaction intermediates. Here, ab initio thermodynamics is used to model which pair of precursors has the most reactive interface, enabling the understanding and anticipation of which non-equilibrium intermediates form in the early stages of a solid-state reaction. In situ X-ray diffraction and in situ electron microscopy are then used to observe how these initial intermediates influence phase evolution in the synthesis of the classic high-temperature superconductor YBa2 Cu3 O6+ x (YBCO). The model developed herein rationalizes how the replacement of the traditional BaCO3 precursor with BaO2 redirects phase evolution through a low-temperature eutectic melt, facilitating the formation of YBCO in 30 min instead of 12+ h. Precursor selection plays an important role in tuning the thermodynamics of interfacial reactions and emerges as an important design parameter in planning kinetically favorable synthesis pathways to complex ceramic materials