Microstructural transformations and kinetics of high-temperature heterogeneous gasless reactions by high-speed x-ray phase-contrast imaging

Abstract

Heterogeneous gasless reactive systems, including high-energy density metal-nonmetal compositions, have seen increasing study due to their various applications. However, owing to their high reaction temperature, short reaction time, and small scale of heterogeneity, investigation of their reaction mechanisms and kinetics is very difficult. In this study, microstructural changes and the kinetics of product layer growth in the W-Si system was investigated using a high-speed x-ray phase-contrast imaging technique. Using the Advanced Photon Source of Argonne National Laboratory, this method allowed direct imaging of irreversible reactions in the W-Si reactive system at frame rates up to 36 000 frames per second with 4 s exposure and spatial resolution of 10 m. Details of the Si melt and reactions between W and Si, that are unable to be viewed with visible-light imaging, were revealed. These include processes such as the initiation of nucleated melting and other physical phenomena that provide insight into the mixing of reactants and subsequent reaction. Through the use of this imaging technique and future optimization in the imaging process, a model for accurately identifying kinetics of chemical reactions, both spatially and temporally, is also proposed.

Reactive multilayers fabricated by vapor deposition: A critical review

“…Differences in experimental test procedures may also account for the dissimilarities, to some degree. A survey of the literature shows that a large range of heating rates have been used for thermal explosion tests of bulk solids [107][108][109][110], and, in general, the T ig of a reactive material increases with heating rate [111,112].…”

Role of nanostructure on reaction and transport in Ni/Al intermolecular reactive composites

“…7,8 Despite these advances, experimental characterization remains limited by the extremely short time scales and small spatial scales involved. 9 On the other hand, such small scales make IRCs appropriate for direct molecular dynamics (MD) simulations that explicitly capture the complex interplay between the various processes such as phase transformations, mass and thermal transport, and solid phase reactions that control the kinetics of these reactions. [10][11][12][13] These studies have correlated melting of the various components of IRCs to their response and provided information about the role of mechanical intermixing and interfacial strain 14 in chemistry.…”

Molecular dynamics simulations of the reaction mechanism in Ni/Al reactive intermetallics

“…A movie of this processes is included in the supplementary material. Similar instabilities driven by local density gradients have been experimentally observed in wires of the reactive W-Si system [34].…”