A5077932967- Nuclear Materials and Properties
- X-ray Diffraction in Crystallography
- Rare-earth and actinide compounds
- Nuclear Physics and Applications
- High-pressure geophysics and materials
- Thermodynamic and Structural Properties of Metals and Alloys
- Microstructure and mechanical properties
- Aluminum Alloys Composites Properties
- Titanium Alloys Microstructure and Properties
- Intermetallics and Advanced Alloy Properties
- Shape Memory Alloy Transformations
- Thermal Expansion and Ionic Conductivity
- High Entropy Alloys Studies
- Advanced ceramic materials synthesis
- Nuclear reactor physics and engineering
- Crystallization and Solubility Studies
- Superconducting Materials and Applications
- Magnetic Properties of Alloys
- Microstructure and Mechanical Properties of Steels
- Radiation Detection and Scintillator Technologies
- Radioactive element chemistry and processing
- High Temperature Alloys and Creep
- Fusion materials and technologies
- Optimization and Search Problems
- Advanced materials and composites
University of Genoa
2019
Los Alamos National Laboratory
1997-2008
Joyce Foundation
2001
Office of Scientific and Technical Information
1996-1998
AC Immune (Switzerland)
1997
Menlo School
1997
Princeton Plasma Physics Laboratory
1990
Princeton University
1990
We report results of the TFTR fission detector calibration performed in December 1988. A NBS-traceable, remotely controlled 252Cf neutron source was moved toroidally through vacuum vessel. Detection efficiencies for two 235U detectors were measured 930 locations point toroidal scans at 16 different major radii and vertical heights. These effectively simulated volume-distributed plasma volume-integrated detection efficiency found to be insensitive position. The Campbell mode is useful due its...
Abstract In this paper, we apply the Lindemann melting rule to analysis of Debye-Waller factor data obtained by neutron powder diffraction for several light actinide phases. The anomalous points actinides can be understood in terms temperature dependences their elastic properties. We have extended include temperature-induced softening.
Abstract We present a statistical mechanical model for the anomalous thermodynamic properties of fcc δ-phase Pu and Pu–Ga alloys. The is based on addition two-level 'Invar'-like electronic energy structure to ordinary Debye lattice, there no assumption magnetic character these levels. Together with usual temperature Θ lattice Grüneisen constant γ includes two additional parameters, spacing ΔE an Γ. 1400 K, Γ negative depends strongly Ga content. accounts satisfactorily thermal expansion, it...
The Ms temperature of the ω, `diffuse ω', and α phases in Zr-Nb alloys have been studied by recording thermal arrests obtained on rapid cooling electrical resistance measurements. Details apparatus which permits heat treatment specimens high vacuum, followed gas quenching, are given together with transformation its dependence rate cooling. is depressed all increasing rate, this depression being 100 degC at 3000 sec-1 for pure zirconium. Proof ω formation given. Hypothetical (Ms, Mf) curves...
Abstract We show that the anomalous thermal expansion behaviour of Pu-Ga alloys can be explained by an Invar effect, which is modelled assuming transfer Pu atoms from a lower-energy higher-volume Δ1, state to higher-energy lower-volume Δ2 state. The energy separation these states found 1400 K fit available neutron diffraction data on lattice constants alloys. model enables precise evaluation coefficient and Grüneisen constant. addition Ga forces stabilization suppresses negative expansion.
Abstract We attempted to characterize by neutron powder diffraction the monoclinic α′ phase that is known form at low temperatures in dilute Pu–Ga alloys. This attempt was unsuccessful, as we did not detect any transformation phase, but instead observed a line-broadening effect fcc δ phase. large enough be visible raw data and highly anisotropic crystal space. The onset temperature of line broadening (150 K) coincides with previous observations δ–α′ transformation. Bulk observed. believe...
Metal-ceramic microstructures were formed in situ by the partial reduction (i.e. of only one metallic elements) spinel compound NiAl2O4. Depending on conditions, these consist Ni particles embedded an α-Al2O3 or a multiphase matrix called 'defect spinel'. The volume shrinkage that accompanies reaction generates residual stresses which profoundly affect microstructure evolution. Conversely, formation metastable, intermediate phases, generation porosity and cracking are all observed may act to...
Abstract We show that the anomalous thermal expansion behaviour of Pu-Ga alloys can be explained by an Invar effect, which is modelled assuming transfer Pu atoms from a lower-energy higher-volume Δ1, state to higher-energy lower-volume Δ2 state. The energy separation these states found 1400 K fit available neutron diffraction data on lattice constants alloys. model enables precise evaluation coefficient and Grüneisen constant. addition Ga forces stabilization suppresses negative expansion.
Abstract In an earlier paper (Lawson et al., 2000, Phil. Mug. B, 80, 53) we described the measurement and interpretation of Debye–Waller factors in a δ-phase Pu0.98Ga0.02 alloy. We concluded that measurements could be using Debye model with strongly temperature-dependent Debye-Waller temperature. those experiments, observed significant diffuse scattering neutron powder diffraction patterns. this describe new technique for analysing based on Rietveld analysis, apply to data Pb. The results...
Neutron powder-diffraction experiments on polycrystalline hexagonal zinc (pow- der specimen with internally powder particles) show considerable tempera- ture-dependent line broadening. Whereas as-received exhibits narrow reflections at 300 K, during cooling to a minimum temperature of 10 K line-broadening appears, which largely disappears reheating. The broadening can be ascribed mi- crostrains induced by thermal microstresses due the intrinsic anisotropy expansion (shrinkage) zinc....
Abstract In October 1995, with the closeout of nuclear physics user program and increased national need for neutrons, Los Alamos National Laboratory refocused mission its linear accelerator complex. The new called development use spallation neutron sources research applications. As a result, complex formerly known as Meson Physics Facility (LAMPF) is now Neutron Science Center (LANSCE). LANSCE, an acronym that referred to Manuel Lujan Jr. Scattering (now Center), consists high-power 800–MeV...
A series of 'short' radial collimators have been implemented in the 90 degree scattering geometries on neutron powder diffractometer at Los Alamos. The capability to perform macrostain measurements has improved by commensurate ability rapidly select a sampling volume appropriate specimen. compact design was dictated need fit them cylindrical vacuum chamber as well providing space which manipulate specimen three dimensions. Collimators different vane lengths were fabricated give 4 resolutions...
We discuss the impact of strong absorption for thermal neutrons on data analysis and compare corrections in GSAS MAUD Rietveld codes texture structural parameter refinement. Diffraction were collected neutron powder diffractometer HIPPO at LANSCE from dysprosium erbium, which are moderate-to-strong absorbers with cross sections 159 barns Er 994 Dy λ =1.8 Å. Both elements have hexagonal-close-packed (hcp) crystal structures, samples various thicknesses rolled foils. The orientation...