Bulk orientational anisotropy without spatial anisotropy due to powder compaction in Al–Ti–B compacts

Gurumurthy, Ashok; Gonzales, Manny; Gokhale, A.M.; Thadhani, Naresh N.

doi:10.1016/j.scriptamat.2014.04.024

Cited by 4 publications

(1 citation statement)

References 6 publications

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“…However, shock intensity measurements are complicated by material moving around during the shock. The fast translational 25 (several μm•ns −1 ) and rotational 26 motions of the microstructure, and shock-induced changes in emissivity, make it difficult to interpret intensity changes in a dynamically evolving shocked medium. The singlet lifetime may be directly related to the chemical and physical environment, and it is insensitive to the intensity of the excitation pulses or changes in the geometry or emissivity that affects the detection efficiency, 1 provided the pump pulses are kept at reasonable intensities below the thresholds for stimulated emission or singlet annihilation, as we did here.…”

Section: Introductionmentioning

confidence: 99%

Emission Lifetimes of a Fluorescent Dye under Shock Compression

et al. 2015

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The emission lifetimes of rhodamine 6G (R6G) were measured under shock compression to 9.1 GPa, with the dual intents of better understanding molecular photophysics in extreme environments and assessing the usefulness of fluorescence lifetime microscopy to measure spatially dependent pressure distributions in shocked microstructured media. R6G was studied as free dye dissolved in poly(methyl methacrylate) (PMMA), or dye encapsulated in silica microparticles suspended in PMMA. Thin layers of these materials in impedance-matched geometries were subjected to planar single-stage shocks created by laser-driven flyer plates. A synchronized femtosecond laser excited the dye at selected times relative to flyer plate arrival and the emission lifetimes were measured with a streak camera. Lifetimes decreased when shocks arrived. The lifetime decrease was attributed to a shock-induced enhancement of R6G nonradiative relaxation. At least part of the relaxation involved shock-enhanced intersystem crossing. For free dye in PMMA, the lifetime decrease during the shock was shown to be a linear function of shock pressure from 0 to 9 GPa, with a slope of -0.22 ns·GPa(-1). The linear relationship makes it simple to convert lifetimes into pressures. Lifetime measurements in shocked microenvironments may be better than emission intensity measurements, because lifetimes are sensitive to the surrounding environment, but insensitive to intensity variations associated with the motion and optical properties of a dynamically changing structure.

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Section: Introductionmentioning

confidence: 99%

Emission Lifetimes of a Fluorescent Dye under Shock Compression

et al. 2015

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Challenges in Understanding the Dynamic Behavior of Heterogeneous Materials

Gonzales

Thadhani

2020

Integrated Computational Materials Engineering (ICME)

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Isotropic Growth on Cartesian Voxel Grids with von Neumann Neighborhoods for Rapid Generation of Synthetic Microstructures

Payton,

Coutinho,

Gerlt

et al. 2024

Metallogr. Microstruct. Anal.

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Randomized instantiations of synthetic microstructures are needed to assess the statistical significance of microstructure variability. Algorithms that use Voronoi tessellations of random points produce synthetic polycrystalline microstructures with a less realistic appearance than random packing of spheroidal particles followed by growth-until-impingement. Additionally, Voronoi tessellations offer limited control of morphological parameters and are challenging to implement when the desired volume fraction is less than unity. However, unless additional physics-based constraints are applied, growth on a Cartesian voxel grid utilizing a von Neumann neighborhood element results in anisotropic growth that is generally not observable along the primary axes. The present work describes both analytical and empirically optimized corrections for directional growth rates and a framework for their inclusion in a synthetic microstructure generation algorithm. The presented algorithm can produce synthetic microstructures similar to those produced by random seed Monte Carlo techniques in a fraction of the computational time.

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Bulk orientational anisotropy without spatial anisotropy due to powder compaction in Al–Ti–B compacts

Cited by 4 publications

References 6 publications

Emission Lifetimes of a Fluorescent Dye under Shock Compression

Emission Lifetimes of a Fluorescent Dye under Shock Compression

Challenges in Understanding the Dynamic Behavior of Heterogeneous Materials

Isotropic Growth on Cartesian Voxel Grids with von Neumann Neighborhoods for Rapid Generation of Synthetic Microstructures

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