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Using In Situ TEM Helium Implantation and Annealing to Study Cavity Nucleation and Growth

JOM

Taylor, Caitlin A.; Sugar, Joshua D.; Robinson, David R.; Bartelt, Norman C.; Sills, Ryan B.; Hattar, Khalid M.

Noble gases are generated within solids in nuclear environments and coalesce to form gas stabilized voids or cavities. Ion implantation has become a prevalent technique for probing how gas accumulation affects microstructural and mechanical properties. Transmission electron microscopy (TEM) allows measurement of cavity density, size, and spatial distributions post-implantation. While post-implantation microstructural information is valuable for determining the physical origins of mechanical property degradation in these materials, dynamic microstructural changes can only be determined by in situ experimentation techniques. We present in situ TEM experiments performed on Pd, a model face-centered cubic metal that reveals real-time cavity evolution dynamics. Observations of cavity nucleation and evolution under extreme environments are discussed.

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TYPE Journal Article YEAR 2020
ScopusOSTIDOI

Palladium-Coated Platinum Powders with Tunable, Nanostructured Surfaces for Applications in Catalysis

ACS Applied Nano Materials

Gurung, Sita; Robinson, David R.; Cappillino, Patrick J.

Simultaneous control of nanoscale surface morphology and composition remains a challenge in preparing bimetallic catalysts, particularly at the large scale required for industrial application and with high-surface-area substrates. Atomic layer electroless deposition (ALED) is a scalable approach to prepare surface-modified metal powders in which elements more noble than the surface hydrides of the substrate metal are deposited layer-by-layer in a surface-limited fashion. Herein we demonstrate that high-surface-area Pt powder is a viable substrate for controlled deposition of Pd adlayers using this technique, with the potential for large-scale preparation, for use in electrocatalytic and catalytic applications such as fuel cells and functionalization of petrochemical feedstocks. Two different growth mechanisms have been proposed based on bulk and surface Pd atomic fractions obtained from atomic absorption spectroscopy and X-ray photoelectron spectroscopy, respectively. Further, spectral simulations were performed to strengthen the proposed growth mechanisms, favoring conformal growth in initial deposition followed by island formation in subsequent cycles. Observation of multiple pathways suggests a means of controlling adlayer surface morphology of ALED materials, in which an initial cycle of deposition sets the fractional coverage and subsequent cycles tune adlayer thickness.

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TYPE Journal Article YEAR 2020
ScopusOSTIDOI

Listening to Radiation Damage In Situ: Passive and Active Acoustic Techniques

JOM

Dennett, Cody A.; Choens, R.C.; Taylor, Caitlin A.; Heckman, Nathan H.; Ingraham, Mathew D.; Robinson, David R.; Boyce, Brad B.; Short, Michael P.; Hattar, Khalid M.

Knowing when, why, and how materials evolve, degrade, or fail in radiation environments is pivotal to a wide range of fields from semiconductor processing to advanced nuclear reactor design. A variety of methods, including optical and electron microscopy, mechanical testing, and thermal techniques, have been used in the past to successfully monitor the microstructural and property evolution of materials exposed to extreme radiation environments.Acoustic techniques have also been used in the past for this purpose, although most methodologies have not achieved widespread adoption. However, with an increasing desire to understand microstructure and property evolution in situ, acoustic methods provide a promising pathway to uncover information not accessible to more traditional characterization techniques. This work highlights how two different classes of acoustic techniques may be used to monitor material evolution during in situ ion beam irradiation. The passive listening technique of acoustic emission is demonstrated on two model systems, quartz and palladium, and shown to be a useful tool in identifying the onset of damage events such as microcracking.An active acoustic technique in the form of transient grating spectroscopy is used to indirectly monitor the formation of small defect clusters in copper irradiated with self-ions at high temperature through the evolution of surface acoustic wave speeds.These studies together demonstrate the large potential for using acoustic techniques as in situ diagnostics. Such tools could be used to optimize ion beam processing techniques or identify modes and kinetics of materials degradation in extreme radiation environments.

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TYPE Journal Article YEAR 2020
ScopusOSTIDOI

Materials and Hydrogen Isotope Science at Sandia's California Laboratory

Zimmerman, Jonathan A.; Balch, Dorian K.; Bartelt, Norman C.; Buchenauer, D.A.; Catarineu, Noelle R.; Cowgill, D.F.; El Gabaly Marquez, Farid E.; Karnesky, Richard A.; Kolasinski, Robert K.; Medlin, Douglas L.; Robinson, David R.; Ronevich, Joseph A.; Sabisch, Julian E.; San Marchi, Christopher W.; Sills, Ryan B.; Smith, Thale R.; Sugar, Joshua D.; Zhou, Xiaowang Z.

Abstract not provided.

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TYPE Conference Poster YEAR 2018
OSTI
Results 1–25 of 154
Results 1–25 of 154