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Search Publications by Andrew J Allen

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Displaying 1 - 25 of 114

Volumetric and Size Characterization of Void Morphologies in Thermally Sprayed Metallic Deposits Using Scattering Techniques

October 12, 2021
T Keller, W. Wagner, J Ilavsky, Andrew J. Allen, N Margadant, S Siegmann, J Pisacka, G Barbezat, R Enzl
The complex void microstructure of thermally sprayed deposits may be approximated by three major void syste(interlamellar pores, intralamellar cracks, and volumetric globular voids), each with different volume fractions,anisotropies, sizes and shapes. This

Solid-State Transformation of an Additive Manufactured Inconel 625 Alloy at 700 degC

September 23, 2021
Fan Zhang, Jan Ilavsky, Greta Lindwall, Mark R. Stoudt, Lyle E. Levine, Andrew J. Allen
Inconel 625, a nickel-based superalloy, has drawn much attention in the emerging field of additive manufacturing (AM) because of its excellent weldability and resistance to hot cracking. The extreme processing condition of AM often introduces enormous

Density Functional Theory Study of the Structure of the Pillared Hofmann compound Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4] (Ni-BpyMe or PICNIC 21)

July 14, 2021
Eric J. Cockayne, Winnie Wong-Ng, Yu-Sheng Chen, Jeffrey T. Culp, Andrew J. Allen
We use dispersion-corrected density functional theory (DFT) to investigate the structure of the pillared Hofmann compound Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4] (NiBpyMe for short, or PICNIC 21). We model the disorder found in experimental X-ray structure

Synthesis, Structural and Sorption Characterization of a Hofmann Compound, Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4]

March 6, 2021
Winnie Wong-Ng, Jeffrey T. Culp, Daniel Siderius, Yu-Sheng Chen, S. Y. G. Wang, Andrew J. Allen, Eric J. Cockayne
Crystal structure of the guest-free Ni(CN)4-based metal organic framework Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4] (nicknamed Ni-BpyMe(A)), was determined to be orthorhombic, Pmma, a= 12.6025(4) Å, b=7.3324(3) Å, c=11.3095(4) Å, V=1045.07 (2) Å3 and Z=2

Materials Research & Measurement Needs for Ceramics Additive Manufacturing

November 1, 2020
Andrew J. Allen, Igor Levin, Suzanne E. Witt
We report on a recent workshop dedicated to additive manufacturing (AM) of ceramics that was held at the National Institute of Standards and Technology (NIST) in November 2019. This two- day all-invited meeting brought together experts from industry

Early stage nucleation in barium disilicate glass

August 1, 2020
Ling Cai, Randall E. Youngman, David E. Baker, Aram Rezikyan, Minghui Zhang, Bryan Wheaton, Indrajit Dutta, Bruce G. Aitken, Andrew J. Allen
Early stage nucleation in silicate glasses is often evidenced by formation of nanosized regions that are stoichiometrically different from the surrounding matrix. The structural origin of these early stage nucleation sites is of great interest in gaining a

Outcomes and Conclusions from the 2018 AM-Bench Measurements, Challenge Problems, Modeling Submissions, and Conference

February 13, 2020
Lyle E. Levine, Brandon M. Lane, Jarred C. Heigel, Kalman D. Migler, Mark R. Stoudt, Thien Q. Phan, Richard E. Ricker, Maria Strantza, Michael R. Hill, Fan Zhang, Jonathan E. Seppala, Edward J. Garboczi, Erich D. Bain, Daniel Cole, Andrew J. Allen, Jason C. Fox, Carelyn E. Campbell
The Additive Manufacturing Benchmark Test Series (AM-Bench) was established to provide rigorous measurement test data for validating additive manufacturing (AM) simulations for a broad range of AM technologies and material systems. AM-Bench includes

Utica Shale Reactivity: CO2 Induced Pore Scale Changes in the Fracture Network and Matrix

January 3, 2020
Angela Goodman, Sean Sanguinito, Sittichai Natesakhawat, Patricia Cvetic, Barbara Kutchko, Andrew J. Allen
The Utica Shale is expected to be a substantial fossil fuel resource in the future. Currently, 663.5 billion cubic feet of natural gas and oil are being produced from the Utica in Eastern Ohio. In this work, we examined the Utica Shale and its reactivity

Phase Fraction and Evolution of Additively Manufactured 15-5 Stainless Steel and Inconel 625 AM- Benchmark Artifacts

August 5, 2019
Fan Zhang, Lyle E. Levine, Andrew J. Allen, Sandra A. Young, Maureen E. Williams, Mark R. Stoudt, Kil-Won Moon, Jarred C. Heigel, Jan Ilavsky
A proper understanding of the structure and microstructure of additive manufactured (AM) alloys is essential not only to the prediction and assessment of their material properties, but also to the validation and verification of computer models essential to

Disordered Heterogeneous Materials

July 1, 2019
Andrew J. Allen
This chapter describes the use of diffraction-based methods to characterize amorphous or disordered heterogeneous materials. Quantitative materials microstructure characterization using small-angle scattering methods is emphasized. While these techniques

Structural basis of CO2 adsorption in a flexible metal organic framework material

March 4, 2019
Andrew J. Allen, Winnie K. Wong-Ng, Eric J. Cockayne, Jeffrey T. Culp, Christopher Matranga
This paper reports the structural basis of CO2 adsorption in a representative model flexible metal organic framework (MOF) material, Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)4] (NiBpene or PICNIC-60). NiBpene exhibits a CO2 sorption isotherm with

Simulation of TTT curves for additively manufactured Inconel 625

January 1, 2019
Carelyn E. Campbell, Greta Lindwall, Eric Lass, Fan Zhang, Mark R. Stoudt, Andrew J. Allen, Lyle E. Levine
The ability to use common computational thermodynamic and kinetic tools to study the microstructure evolution in Inconel 625 (IN625) manufactured using the additive manufacturing (AM) technique of laser powder-bed fusion is evaluated. Solidification

Transformation of Engineered Nanomaterials through the Prism of Silver Sulfidation

January 1, 2019
Fan Zhang, Andrew J. Allen, Aaron C. Johnston-Peck, Jingyu Liu, John M. Pettibone
Structure transformation of engineered nanomaterials (ENMs) often dictates their efficacy, safety, and environmental impact. To address the existing significant knowledge gap regarding the fundamental kinetic rate and extent of ENMs transformation in

High-efficiency Coherence-Preserving Harmonic Rejection with Crystal Optics

September 1, 2018
Fan Zhang, Andrew J. Allen, Lyle E. Levine, Gabrielle G. Long, Ivan Kuzmenko, Jan Ilavsky
We report a harmonic rejection scheme based on the combination of Si (111) monochromator and Si (220) harmonic-rejection crystal optics. This approach is of importance to a wide range of X- ray applications in all three major branches of modern X-ray

Effect of Heat Treatment on the Microstructural Evolution of a Nickel-Based Superalloy Additive-Manufactured by Powder Bed Fusion Laser Sintering

June 15, 2018
Fan Zhang, Lyle E. Levine, Andrew J. Allen, Mark R. Stoudt, Greta Lindwall, Eric Lass, Maureen E. Williams, Yaakov S. Idell, Carelyn E. Campbell
Elemental segregation is a ubiquitous phenomenon in additive-manufactured (AM) parts due to solute rejection and redistribution during the rapid solidification process. Using electron microscopy, in situ synchrotron X-ray scattering and diffraction, and

Development of combined microstructure and structure characterization facility for in situ and operando studies at the Advanced Photon Source

June 1, 2018
Jan Ilavsky, Fan Zhang, Ross N. Andrews, Ivan Kuzmenko, Pete R. Jemian, Lyle E. Levine, Andrew J. Allen
Following many years of evolutionary development, first at the National Synchrotron Light Source, Brookhaven National Laboratory, and then at the Advanced Photon Source (APS), Argonne National Laboratory, the APS ultra-small-angle X-ray scattering (USAXS)

In situ Angstrom-to-Micrometer Characterization of the Structural and Microstructural Changes in Kaolinite on Heating using Ultra-Small-Angle, Small-Angle, and Wide-Angle X-ray Scattering (USAXS/SAXS/WAXS)

September 26, 2017
Fan Zhang, Andrew J. Allen, Greeshma Gadikota
In this study, synchrotron-based in-operando multi-scale X-ray scattering analyses are used to connect the microstructural changes to the phase changes in kaolinite on heating from 30 °C to 1150 °C. Combined ultra-small-angle and small-angle X-ray

Application of Finite Element, Phase-field, and CALPHAD-based Methods to Additive Manufacturing of Ni-based Superalloys

September 21, 2017
Trevor Keller, Greta Lindwall, Supriyo Ghosh, Li Ma, Brandon M. Lane, Fan Zhang, Ursula R. Kattner, Eric Lass, Yaakov S. Idell, Maureen E. Williams, Andrew J. Allen, Jonathan E. Guyer, Lyle E. Levine
Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element