Andrew J Allen (Fed)

Research Interests

• X-ray and neutron scattering-based microstructure characterization to address technological barriers in advanced materials development, for example:
• Nanoparticle formation, assembly and interaction, for industrial, biomedical and environmental health applications (including RM development in collaboration with National Cancer Institute).
• Structure-property relationships in films, coatings and energy materials, including high-k dielectric films, thermal barrier coatings and solid oxide fuel cell materials.
• Fundamentals of cement hydration, including the effects of additives and environmental conditions on concrete used in the nation's infrastructure.
• In operando characterization of selective gas sorption phenomena in advanced sorbents and carbonation processes.
• X-ray and neutron studies of mesoscale equilibrium and non-equilibrium dynamics relevant to advanced materials processes, e.g., ceramics additive manufacturing and densification, or precipitation kinetics in additive manufactured alloys.

Postdoctoral Research Opportunities

Microstructure of Structural and Functional Ceramics for Additive Manufacturing, Energy Conversion and Storage
(Research Opportunity no. 50.64.31.B7417):
Control of microstructure, internal dynamics, materials physics and chemistry is of primary importance in determining the processing, performance and viability of advanced ceramic components such as relevant to solid oxide or hydrogen fuel cells, carbon capture materials (including direct air capture and carbon mineralization), and other systems that advance the hydrogen economy, promote US energy independence, or support advanced manufacturing methods such as additive manufacturing (AM) and post-process densification. The operative scale range for the void and phase microstructures of relevance extends from the micrometer scale down to the sub-nanometer scale regime. Our goal is to leverage our access to state-of-art X-ray and neutron facilities to develop and apply operando measurement methods that can quantify full three-dimensional void and phase microstructures and dynamics in technological ceramic materials, including changes during service life and dependence on processing conditions [1]. Such characterization addresses issues relevant to (e.g.) the electrodes and electrolyte of SOFCs, component phases and interfaces in fuel-reforming, hydrogen storage or carbon dioxide capture materials. In these cases, the microstructure frequently must be related to the reaction site kinetics and to changes in site chemical reactivity during service life [2]. Equally, these characterization methods interrogate physics-based phenomena relevant to many aspects of ceramic advanced manufacturing such as found in direct-ink write ceramic extrusion AM and in novel post-process densification methods such as cold sintering of AM ceramic green bodies [3]. This opportunity will address these interconnected issues by utilizing unique instrumentation, developed by NIST and its collaborators, and located at the Advanced Photon Source, the National Synchrotron Light Source II, and the NIST Center for Neutron Research. In summary, the opportunity exists for investigating fundamental processes relevant to novel energy materials and devices including structural and electronic ceramics, batteries, solid oxide fuel cells, energy harvesting devices, photovoltaics, carbon capture materials, as well as phenomena relevant to additive manufacturing of ceramics and their post-process densification. Complementary computational model simulation capabilities are also available.
For more information...

Carbon (CO₂) Capture, Selective Gas Sorbent Materials, and Carbon Sequestration
(Research Opportunity no. 50.64.31.B8183):
Many industrial processes generate carbon dioxide as a by-product, which is released to the atmosphere and contributes to global warming. To address the increasing urgency of mitigating global warming, clean, low-carbon-dioxide emission technologies must be complemented with more aggressive carbon capture technologies, including those for the direct air capture (DAC) of carbon dioxide, and its permanent mineralization or sequestration through appropriate carbonation processes. Development of these technologies is critical to meet U.S. energy and manufacturing needs in an environmentally sustainable manner. Low carbon emission and direct carbon capture technologies depend on transient gas/solid material interactions. Such interactions cannot be inferred from initial or final state materials property measurements such as sorbent microstructure, but must be measured in situ during the sorption or release process. This project focuses on the design, construction, and application of a suite of in situ measurement platforms for use with NIST’s state-of-the-art neutron and synchrotron X-ray scattering facilities [1], capable of interrogating critical carbon capture properties across the range of candidate carbon dioxide sorbent solid materials, as well as candidate materials, both natural and fabricated, for final mineralization or sequestration of carbon dioxide through carbonation. Measurements will focus on in situ determination of changes in structure, microstructure, atomic bonding, and dynamics in sorbent materials during the sorption and release of carbon dioxide under controlled conditions of temperature, pressure, humidity, and atmosphere, or in the case of mineralization as a function of carbonation reaction. Where possible, X-ray or neutron diffraction abd scattering analysis [2] and thermogravimetric analysis will be carried out in situ with samples that are simultaneously undergoing evolved gas analysis. The experimental measurements will be complemented by computer model simulations using available capabilities based on methods such as density functional theory (DFT) [3].
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    •    Plenary Speaker, 18th International Conference on Small-Angle Scattering, Campinas, Brazil, 2022
    •    Editor-in-Chief of International Union of Crystallography (IUCr) Journals, 2018 - present
    •    Department of Commerce Silver Medal, Group Award, 2016
    •    Main Editor, Journal of Applied Crystallography, 2014-2018
    •    Plenary Speaker, 15th International Conference on Small-Angle Scattering, Sydney, Australia, 2012
    •    Department of Commerce Bronze Medal Award, 2009
    •    Department of Commerce Silver Medal, Group Award, 2008
    •    Best Paper Award, Journal of Thermal Spray Technology, Volume 14, 2005
    •    Co-Editor, Journal of Applied Crystallography, 2002-2014
    •    NIST Bronze Medal, Group Award, 1998
    •    Best Paper Award, International Thermal Spray Conference, France, 1998
    •    Advisory Editor, Journal of Physics: Condensed Matter, 1991-96
    •    Open Exhibition Scholarship, Oxford University, 1974-1977