A5004125539- Nuclear Materials and Properties
- Metallic Glasses and Amorphous Alloys
- Fusion materials and technologies
- Nuclear reactor physics and engineering
- Diamond and Carbon-based Materials Research
- Glass properties and applications
- Energetic Materials and Combustion
- Quantum Dots Synthesis And Properties
- Theoretical and Computational Physics
- Radioactive element chemistry and processing
- Metal and Thin Film Mechanics
- Silicon Nanostructures and Photoluminescence
- High-pressure geophysics and materials
- Nuclear Physics and Applications
- Polymer crystallization and properties
- High-Temperature Coating Behaviors
- Semiconductor materials and devices
- biodegradable polymer synthesis and properties
- Semiconductor materials and interfaces
- Thermal and Kinetic Analysis
- Advanced Materials Characterization Techniques
- Crystallography and molecular interactions
- Chemical Thermodynamics and Molecular Structure
- nanoparticles nucleation surface interactions
- X-ray Diffraction in Crystallography
Lawrence Livermore National Laboratory
2012-2023
Lawrence Livermore National Security
2021
California Institute of Technology
2019
Atomic Weapons Establishment
2017
Argonne National Laboratory
1984-2006
Southern University and Agricultural and Mechanical College
2006
Louisiana State University
2006
University of Bonn
2006
University at Albany, State University of New York
2006
Lawrence Berkeley National Laboratory
2004
Co nanoparticles with three different crystal structures were synthesized in a microfluidic reactor through manipulation of reaction times, flow rates, and quenching procedures. Cobalt face-centered cubic (β) phase obtained from high rate the reactants followed by situ reaction. hcp ε-cobalt at low delayed quenching, respectively. The characterized using K-edge X-ray absorption near edge structure (XANES) spectroscopy, diffraction (XRD), selected area electron (SAED). In XANES measurements...
We present a two-step synthesis route that yields nanometer-size crystalline germanium in the form of black powder. It relies on high temperature decomposition tetraethylgermane (TEG) organic solvents. The presence pure with diamond structure is unambiguously attested by powder XRD measurements. Low-resolution TEM indicates particles are between ∼5 to 30 nm size, depending conditions. as-synthesized Ge powders can be stored air for months and no oxidation occurs. sparingly soluble...
Amorphous metal and ceramic thermal spray coatings have been developed with excellent corrosion resistance neutron absorption. These coatings, further development, could be cost-effective options to enhance the of drip shields waste packages, limit nuclear criticality in canisters for transportation, aging, disposal spent fuel. Iron-based amorphous formulations chromium, molybdenum, tungsten shown believed necessary such applications. Rare earth additions enable very low critical cooling...
In the present study, structural and morphological development during melt spinning of polyethylene poly(vinylidene fluoride) fibers was studied using simultaneous in-situ synchrotron small- wide-angle X-ray scattering (SWAXS) techniques. The apparatus consisted a single screw extruder, which mounted on horizontal platform that could be translated in vertical direction allowing different spinneret distances to sampled with beam. Effects take-up speed (10.6−61.0 mpm) distance (30−87.5 cm)...
We are working to perfect the growth of divalent Eu-doped strontium iodide single crystals and optimize design SrI<sub>2</sub>(Eu)-based gamma ray spectrometers. SrI<sub>2</sub>(Eu) offers a light yield in excess 100,000 photons/MeV proportionality surpassing that Ce-doped lanthanum bromide. Thermal x-ray diffraction analyses SrI<sub>2</sub> EuI<sub>2</sub> indicate an excellent match melting crystallographic parameters, very modest thermal expansion anisotropy. have demonstrated energy...
Ge nanoparticles with sizes from 1 to 15 nm were synthesized by thermal decomposition of the germane precursors trichlorogermane, tetraethylgermane, and tetrabutylgermane. Experiments performed in organic solvents trioctylamine, squalene, octacosane, which have boiling points temperature range 380 429 °C. The use high-boiling-point extended reactions, thus enabling experiments be conducted organogermane high above 400 Characterization X-ray diffraction transmission electron microscopy showed...
We report experimental and computational studies of shock wave dynamics in single-crystal β-HMX on an ultrafast time scale. Here, a laser-based compression drive (∼1 ns duration; stresses up to ∼40 GPa) is used propagate waves normal the (110) (010) lattice planes. Ultrafast time-domain interferometry measurements reveal distinct, time-dependent relationships between velocity particle for each crystal orientation, which suggest evolving physical processes sub-nanosecond To help interpret...
Abstract We report on fabrication and characterization of layered, tungsten doped, spherical about 2 mm diameter microcrystalline diamond ablator shells for inertial confinement fusion (ICF) experiments at the National Ignition Facility. As previously reported, ICF can be fabricated by chemical vapor deposition (CVD) solid silicon mandrels using an ellipsoidal microwave plasma reactor. In present work, we further developed these embedding a W -doped layer sandwiched between two undoped...
Abstract “Row nucleated lamellar” structures are formed when highly crystalline polymers melt‐extruded and recrystallized under high stress. Polyethylene (PE) polypropylene (PP) films with row lamellar have been utilized to produce microporous membranes. Birefringence measurements of PE show that improved film orientation can be achieved by annealing, extruding at higher speed, using molecular weight polymers. Images from scanning tunneling, atomic force, field emission electron microscopy...
Structural phase transitions in the rare-earth metal dysprosium have been studied a diamond anvil cell to 119 GPa by x-ray diffraction. Four transformations following sequence hcp→Sm-type→dhcp→hR24 (hexagonal)→bcm (monoclinic) are observed at 6, 15, 43, and 73 GPa, respectively. The hexagonal monoclinic transformation is accompanied 6% reduction volume, which attributed delocalization of 4f electrons, similar that seen Ce, Pr, Gd.
An iron-based amorphous metal with good corrosion resistance and a high absorption cross section for thermal neutrons has been developed is reported here. This alloy the approximate formula Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 known as SAM2X5. Chromium, molybdenum, tungsten were added to provide resistance, while boron was promote glass formation of neutrons. Since this higher content than conventional borated stainless steels, it provides nuclear engineer design advantages criticality...
The hydrogen uptake kinetics of 1,4-bis(phenylethynyl)benzene, or DEB, mixed with palladium (Pd) on activated carbon in a rubber matrix coating top porous silicone foam substrate are investigated. First, isothermal isobaric hydrogenation experiments were performed under different temperatures and H2 pressures to extract the kinetics. models based measured kinetic parameters then employed investigate/simulate performance getter dynamic application environments. actual characteristics this...
In an oxidizing environment, the oxide formed on plutonium (Pu) metal is composed of a dioxide (PuO2) top layer and thin cubic sesquioxide (Pu2O3) middle layer. reducing PuO2 auto-reduces to Pu2O3. The speed extent this conversion depend combination temperature time. While provides strong diffusion barrier against unwanted Pu corrosion by gaseous species (like hydrogen), Pu2O3 does not, since its crystal structure has chains oxygen vacancies. kinetics reduction are, therefore, fundamental...
Single-crystal germanium nanowires have been synthesized in the temperature range 380–430 °C without use of any metal catalysts. Tetraethylgermane was used as a precursor combination with different organic solvents to produce controlled diameter ranging from 5 nm 700 nm. The growth direction is along <011> direction. method based on vapor-liquid-solid mechanism, classical liquid-metal catalyst replaced by droplets high-boiling-point hydrocarbons.