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Reaction kinetics and phase evolution of nanoporous TaC from metallic precursors.

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Title: Reaction kinetics and phase evolution of nanoporous TaC from metallic precursors.
Authors: Ott, Catherine1 (AUTHOR), Peters, Adam2 (AUTHOR), McCue, Ian1 (AUTHOR) ian.mccue@northwestern.edu
Source: Acta Materialia. Apr2026, Vol. 307, pN.PAG-N.PAG. 1p.
Subjects: Carburization, Activation energy, Ultra-high-temperature ceramics, Phase transitions, Microstructure, Metal compounds, Chemical kinetics
Abstract: Ultra-high temperature ceramics (UHTCs) are promising materials for use in next-generation aerospace structures but have processing challenges, particularly with respect to densification. Here, a nano-sized UHTC powder precursor was synthesized via atmospheric pressure gas-phase carburization of nanoporous tantalum to the ultra-high-temperature ceramic, TaC, at unconventionally low temperatures (700–900 °C). First, a 1-D moving interface model was constructed to predict carburization depth and compare data from the present work to that in the literature, and the model was validated for finite geometries (i.e., powders). Then, the kinetic properties of Ta conversion in a carburizing environment were examined over a range of temperatures to determine rate-limiting behavior and activation energy for the process. It was found that the apparent activation energy for carburization was initially low, and conversion proceeded much faster than predicted, suggesting accelerated carbon diffusion pathways. Detailed microstructural analysis was carried out on in-house atomized powders, which did not show evidence of grain boundary diffusion. Instead, it revealed that the effects of residual strain and defects from processing may play a significant role in the carburization rates of tantalum. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Ultra-high temperature ceramics (UHTCs) are promising materials for use in next-generation aerospace structures but have processing challenges, particularly with respect to densification. Here, a nano-sized UHTC powder precursor was synthesized via atmospheric pressure gas-phase carburization of nanoporous tantalum to the ultra-high-temperature ceramic, TaC, at unconventionally low temperatures (700–900 °C). First, a 1-D moving interface model was constructed to predict carburization depth and compare data from the present work to that in the literature, and the model was validated for finite geometries (i.e., powders). Then, the kinetic properties of Ta conversion in a carburizing environment were examined over a range of temperatures to determine rate-limiting behavior and activation energy for the process. It was found that the apparent activation energy for carburization was initially low, and conversion proceeded much faster than predicted, suggesting accelerated carbon diffusion pathways. Detailed microstructural analysis was carried out on in-house atomized powders, which did not show evidence of grain boundary diffusion. Instead, it revealed that the effects of residual strain and defects from processing may play a significant role in the carburization rates of tantalum. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:13596454
DOI:10.1016/j.actamat.2026.121980