A5059989559- Energetic Materials and Combustion
- High-pressure geophysics and materials
- Diamond and Carbon-based Materials Research
- Calcium Carbonate Crystallization and Inhibition
- Force Microscopy Techniques and Applications
- Ion-surface interactions and analysis
- Minerals Flotation and Separation Techniques
- Additive Manufacturing Materials and Processes
- Iron oxide chemistry and applications
- Combustion and Detonation Processes
- Carbon Nanotubes in Composites
- Machine Learning in Materials Science
- Advanced Electron Microscopy Techniques and Applications
- Polymer Surface Interaction Studies
- Nuclear Physics and Applications
- Particle Accelerators and Free-Electron Lasers
- Molecular Junctions and Nanostructures
- Aerogels and thermal insulation
- Bone Tissue Engineering Materials
- Crystallization and Solubility Studies
- Laser Material Processing Techniques
- Particle accelerators and beam dynamics
- Paleontology and Stratigraphy of Fossils
- Boron and Carbon Nanomaterials Research
- X-ray Spectroscopy and Fluorescence Analysis
Lawrence Livermore National Laboratory
2011-2024
Aarhus University
2023
General Atomics (United States)
2021
Argonne National Laboratory
2021
Lawrence Livermore National Security
2019
Lawrence Berkeley National Laboratory
2012-2014
University of California, Berkeley
2012-2014
University of California System
2013
University of California, Davis
2009
The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism crystal growth many materials, yet the alignment process have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe iron oxyhydroxide nanoparticles. particles undergo continuous rotation interaction until they find perfect lattice match. A sudden jump contact then occurs over less than 1 nanometer,...
Watching nucleation pathways in calcite The initial stage of crystallization, the formation nuclei, is a critical process, but because length and time scales involved, hard to observe. Nielsen et al. explored crystallization calcium carbonate, well-studied material one with multiple theories. Different carbonate solutions were mixed inside fluid cell imaged using liquid transmission electron microscope. Competing operated during nucleation, both direct association ions into nuclei from...
Circumventing spatter Laser powder bed fusion is an additive manufacturing technique that laser-melts layer by to build a three-dimensional (3D) part. Khairallah et al. used experiments and multiphysics model determine the origin of melt defect formation degrade properties built parts (see Perspective Polonsky Pollock). Informed modulation laser power important avoid disturbing creating shadowing. This reduces pore formations leads more uniform 3D-printed parts. Science , this issue p. 660 ;...
Nucleation in the natural world often occurs presence of organic interfaces. In mineralized tissues, a range macromolecular matrices are found contact with inorganic phases and believed to direct mineral formation. geochemical settings, surfaces, which covered or biological films, surround volume within nucleation occurs. classical picture nucleation, such interfaces is expected have profound effect on rates, simply because they can reduce interfacial free energy, controls height...
Advanced in situ characterization is essential for determining the underlying dynamics of laser-material interactions central to both laser welding and rapidly expanding field additive manufacturing. Traditional techniques leave a critical experimental gap understanding complex subsurface fluid flow metal evaporation inherent laser-induced heating metal. Herein, ultra-high-speed transmission X-ray imaging revealed be bridging this information gap, particularly via comparison with validation...
Developing three-dimensional (3D) graphene assemblies with properties similar to those individual sheets is a promising strategy for graphene-based electrodes. Typically, the synthesis of 3D relies on van der Waals forces holding together, resulting in bulk that do not reflect reported sheets. Here, we report use sol−gel chemistry introduce chemical bonding between and control aerogels. Adjusting synthetic parameters allows wide range over surface area, pore volume, size, as well nature...
Abstract Recent ex situ observations of crystallization in both natural and synthetic systems indicate that the classical models nucleation growth are inaccurate. However, can provide direct evidence for alternative have been lacking due to limited temporal spatial resolution experimental techniques observe dynamic processes a bulk solution. Here we report results from liquid cell transmission electron microscopy studies Au, CaCO 3 , iron oxide nanoparticles. We show how these data be used...
Abstract Transit through the carbon liquid phase has significant consequences for subsequent formation of solid nanocarbon detonation products. We report dynamic measurements condensation and solidification into nano-onions over ∽200 ns by analysis time-resolved, small-angle X-ray scattering data acquired during a hydrogen-free explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts direct to graphite transition products ~200 post-detonation. Solid...
Abstract Carbon nanoallotropes are important nanomaterials with unusual properties and promising applications. High pressure synthesis has the potential to open new avenues for controlling designing their physical chemical characteristics a broad range of uses but it remains little understood due persistent conceptual experimental challenges, in addition fundamental physics chemistry questions that still unresolved after many decades. Here we demonstrate sub-nanosecond nanocarbon through...
Significance Whether water is produced by solar wind (SW) radiolysis has been debated for more than four decades. In this paper, we exploit the high spatial resolution of electron microscopy and sensitivity valence energy-loss spectroscopy to detect (liquid or vapor) in vesicles within (SW-produced) space-weathered rims on interplanetary dust particle (IDP) surfaces. Water implications origin airless bodies like Moon asteroids, delivery surfaces terrestrial planets, production other...
Laser powder bed fusion (LPBF) additive manufacturing and laser welding are powerful metal processing techniques with broad applications in advanced sectors such as the biomedical aerospace industries. One common process variable that can tune laser-material interaction dynamics these two is adjustment of composition pressure atmosphere which conducted. While some physical mechanisms governed by ambient well known from literature, it remains unclear how extend to distinct conditions LPBF. In...
Detonation nanodiamond (DND) is known to form aggregates that significantly reduce their unique nanoscale properties and require postprocessing separate. How when DND an important question has not been answered experimentally could provide the foundation for approaches limit aggregation. To answer this question, time-resolved small-angle X-ray scattering was performed during detonation of high-explosives are expected condense particulates in diamond, graphite, liquid regions carbon phase...
Herein we report the fabrication of ultralight gold aerogel monoliths with tunable densities and pore structures. Gold nanowires are prepared at gram scale by substrate-assisted growth uniform size, ultrathin diameters, high purity, a aspect ratio. Freeze-casting suspensions these produces free-standing, monolithic aerogels from 6 to 23 mg/cm3, which best our knowledge represents lowest density material. We also demonstrate that geometries created during freeze-casting can be systematically...
Improved understanding of structural and chemical properties through local experimental probes, such as X-ray absorption near-edge structure (XANES) spectroscopy, is crucial for the design functional materials. In recent years, significant advancements have been made in development data science approaches automated interpretation XANES structure–spectrum relationships. However, existing studies primarily focused on crystalline solids small molecules, while fewer efforts devoted to disordered...
Through the process of biomineralization living organisms use macromolecules to direct nucleation and growth nanophases a variety inorganic materials. Evidence shows this is widespread strategy for controlling timing, polymorphism, morphology, crystallographic orientation CaCO3 nuclei. In past decade, self-assembled monolayers (SAMs) alkanethiols have been used as simple model reproduce controls organic substrates. However, despite importance phenomena in crystallization materials our...
Characterization of the initial morphology detonation nanodiamond (DND) has been focus many research studies that aim to develop a fundamental understanding carbon condensation under extreme conditions. Identifying pathways DND formation potential for significant impact on controlled synthesis nanoscale with tailored functionality; currently, wide range possible (and conflicting) mechanisms nucleation and growth have proposed, further is essential. Building comprehensive challenging because...
We explore the structural evolution of highly oriented pyrolytic graphite (HOPG) under detonation-induced shock conditions using in situ synchrotron x-ray diffraction ns timescale. observe formation hexagonal diamond (lonsdaleite) at pressures above 50 GPa, qualitative agreement with recent gas gun experiments. First-principles density functional calculations reveal that uniaxial compression, energy barrier for transition toward is lower than cubic diamond. Finally, no indication was...
Abstract Soot generated from the detonation of nine explosives was investigated with Raman microspectroscopy and high‐resolution transmission electron microscopy (HRTEM). The first order bands, located at approximately 1,580 (G), 1,350 (D1), 1,620 cm −1 (D2), 1,500 (D3), 1,200 (D4), are used to provide information on carbon allotropes defects. intensity ratios full‐width half‐maximum an indication disorder in material. spectra soot acquired showed differences which can be identify precursor...
Precise determination of atomic structural information in functional materials holds transformative potential and broad implications for emerging technologies. Spectroscopic techniques, such as X-ray absorption near-edge structure (XANES), have been widely used material characterization; however, extracting chemical from experimental probes remains a significant challenge, particularly disordered materials. We present an integrated approach that combines simulations, data-driven measurements...
Herein is reported a method for fabricating <10 mg/cm3 silver aerogels via the freeze casting of aqueous nanowire suspensions followed by substitution and supercritical drying. This overcomes limitations traditional drying yields highly uniform, crack-free monoliths that undergo no measurable shrinkage with excellent mold reproduction. Significantly, enables use high concentrations cryoprotectants to control freezing process and, hence, pore architecture resulting aerogels. Due its...
Gold-tantalum alloy films are of interest for biomedical and magnetically-assisted inertial confinement fusion applications. Here, we systematically study the effects substrate tilt (0°–80°) negative bias (0–100 V) on properties ≲3-μm-thick deposited by high-power impulse magnetron sputtering (HiPIMS) from a Au–Ta target (with 80 at. % Ta). Results reveal that, all values studied, an increase in leads to monotonic decrease film thickness, density, residual compressive stress, electrical...
Self-assembled monolayers (SAMs) prepared from organic thiol molecules on metal substrates are known to exert substantial influence over mineralization and, as such, provide model systems for investigating the mechanisms of templated crystallization by matrices. Characterizing structural evolution at organic/inorganic interface in SAM/crystal is paramount importance understanding these mechanisms. In this study, X-ray absorption spectroscopy used characterize SAMs purpose-synthesized thiols,...