A5004457047- Molecular Junctions and Nanostructures
- Diamond and Carbon-based Materials Research
- Supercapacitor Materials and Fabrication
- Quantum Dots Synthesis And Properties
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Graphene research and applications
- Hydrogen Storage and Materials
- Boron and Carbon Nanomaterials Research
- Energetic Materials and Combustion
- Chalcogenide Semiconductor Thin Films
- Superconductivity in MgB2 and Alloys
- Ion-surface interactions and analysis
- Thermal and Kinetic Analysis
- X-ray Spectroscopy and Fluorescence Analysis
- Force Microscopy Techniques and Applications
- Additive Manufacturing Materials and Processes
- Calcium Carbonate Crystallization and Inhibition
- High-pressure geophysics and materials
- Advancements in Battery Materials
- Semiconductor materials and devices
- Magnetic Properties of Alloys
- Laser Material Processing Techniques
- Polymer Surface Interaction Studies
- Fuel Cells and Related Materials
Lawrence Livermore National Laboratory
2015-2024
Material Sciences (United States)
2022
University of Giessen
2007-2021
SLAC National Accelerator Laboratory
2021
Mount Vernon Hospital
2018
Lawrence Livermore National Security
2017
Physical Sciences (United States)
2012
University of Cambridge
2001-2010
Diamond Light Source
2009
Argonne National Laboratory
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,...
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 ;...
A new class of castable cerium strengthened aluminum alloys has phenomenal high temperature properties without the need for heat treatment.
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...
We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra the diamondoid exhibited peak at low-kinetic energy threshold; up to 68% all emitted electrons were within this single peak. The intensity emission is indicative diamondoids being negative affinity materials. With an distribution width less than 0.5 volts, source may find application in technologies such as microscopy, beam...
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...
Aerogels are used in a broad range of scientific and industrial applications due to their large surface areas, ultrafine pore sizes, extremely low densities. Recently, number reports have described graphene aerogels based on the reduction oxide (GO). Though these GO-based represent considerable advance relative traditional carbon aerogels, they remain significantly inferior individual sheets poor crystallinity. Here, we report straightforward method synthesize highly crystalline via...
The exciton binding energy (EBE) in CdSe quantum dots (QDs) has been determined using X-ray spectroscopy. Using absorption and photoemission spectroscopy, the conduction band (CB) valence (VB) edge shifts as a function of particle size have combined to obtain true gap QDs (i.e., without an exciton). These values can be compared excitonic obtained optical spectroscopy determine EBE. experimental EBE results are with theoretical calculations on show excellent agreement.
Polymer-derived, monolithic three-dimensional nanographene (3D-NG) bulk material with tunable properties is produced by a simple and inexpensive approach. The mass-producible, combines chemical inertness mechanical strength hierarchical porous architecture graphene-like surface area. This provides an opportunity to control its electron transport dynamically means of electrochemical-induced interfacial electric fields.
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...
All-inorganic CsPbI3 perovskite has emerged as a promising candidate for next-generation solar cells. However, owing to the poor structural stability of black phase at room temperature, it spontaneously transforms yellow, photoinactive, nonperovskite limiting further development To better understand mechanism driving such undesirable transformation, we examine thermodynamics and kinetics associated with γ-to-δ transformation using density functional theory calculation. A solid-state nudged...
Chemical functionality is localized at the entrance of single nanopores using controlled growth an oxide ring. Nanopores fabricated by focused-ion-beam machining on silicon platforms (see Figure and Cover) are locally functionalized ion-beam-assisted deposition followed immobilization DNA probes via silane chemistry. Ion-current measurements used to demonstrate nanopore functionalization.
Formation of biomineral structures is increasingly attributed to directed growth a mineral phase from an amorphous precursor on organic matrix. While many in vitro studies have used calcite formation organothiol self-assembled monolayers (SAMs) as model system investigate this process, they generally focused the stability calcium carbonate (ACC) or maximizing control over order final phase. Little known about early stages formation, particularly structural evolution SAM and mineral. Here we...
HMX-based explosives LX-10 and PBX-9501 were heated through the β-δ phase transition. Ultra-small angle x-ray scattering (USAXS) molecular diffraction simultaneously recorded as HMX was heated. Mesoscale voids structure dramatically change promptly with transition, rather than other thermal effects. Also, induced damage, observed in USAXS, occurs more readily at elevated temperatures; such, dose reduced to mitigate this effect. Optical microscopy performed during a similar heating cycle...
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...
Static electric dipole moments of nondegenerate systems probe mass scales for physics beyond the Standard Model well those reached directly at high energy colliders. Discrimination between different models, however, requires complementary searches in atomic-molecular-and-optical, nuclear and particle physics. In this report, we discuss current status prospects near future a compelling suite such experiments, along with developments needed encompassing theoretical framework.
We show that the deposition of solid-state electrolyte LiPON onto films V2O5 leads to their uniform lithiation up 2.2 Li per V2O5, without affecting concentration in and its ionic conductivity. Our results indicate incorporation occurs during deposition, contrast earlier mechanisms proposed explain postdeposition transfer between LiCoO2. use our discovery demonstrate symmetric thin film batteries with a capacity >270 mAh/g, at rate 20C, 1600 cycles only 8.4% loss capacity. also how...
Abstract Hot‐spot models of initiation and detonation show that voids or porosity ranging from nanometer to micrometer in size within highly insensitive energetic materials affect initiability properties. Thus, the knowledge void distribution, how it changes with volume expansion seen temperature cycling, are important understanding properties explosive 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB). In this paper, distributions 2 nm μm regime, obtained small‐angle X‐ray scattering...
Boron-doped and defect-engineered graphene aerogels are prepared using triphenyl boron as a precursor subsequent heat treatments. The chemistry concentration in the lattice found to be highly dependent on temperature used activate boron. At 1500 °C, is incorporated at 3.2 atom % through combination of B–C, B–N, B–O bonds. 1750 decreases 0.7 predominantly B–N bonding. Higher temperatures result complete expulsion from lattice, leaving behind defects that beneficial for NO2 gas detection....
X-ray absorption spectroscopy has been used to characterize the evolution in conduction band (CB) density of states CdSe quantum dots (QDs) as a function particle size. We have unambiguously witnessed QD CB minimum (CBM) shift higher energy with decreasing size, consistent confinement effects, and directly compared our results recent theoretical calculations. At smallest evidence for pinning CBM is presented. Our observations can be explained by considering size-dependent change...
We report evidence that paramagnetism in CdSe QDs can be induced via manipulation of the surface chemistry. Using SQUID magnetometry and X-ray absorption spectroscopy, we demonstrate paramagnetic behavior varied by changing ligand end-group functionality passivating layer. Contrary to previous reports, no for ferromagnetism was observed. The results suggest is π back-bonding between Cd 4d orbtials ligands with empty π* orbitals.
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...
Internal interfaces in the Li3N/[LiNH2 + 2LiH] solid-state hydrogen storage system alter hydrogenation and dehydrogenation reaction pathways upon nanosizing, suppressing undesirable intermediate phases to dramatically improve kinetics reversibility. The key role of solid determining thermodynamics suggests a new paradigm for optimizing complex hydrides by engineering internal microstructure.