A5019240085- Nuclear Materials and Properties
- Nuclear and radioactivity studies
- Lubricants and Their Additives
- Metal and Thin Film Mechanics
- Hydrogen embrittlement and corrosion behaviors in metals
- Nuclear reactor physics and engineering
- Electrical Contact Performance and Analysis
- High-Temperature Coating Behaviors
- Mechanical stress and fatigue analysis
- Non-Destructive Testing Techniques
- Gear and Bearing Dynamics Analysis
- Fatigue and fracture mechanics
- Tribology and Wear Analysis
- Metal Alloys Wear and Properties
- Diamond and Carbon-based Materials Research
- Nuclear Physics and Applications
- High Entropy Alloys Studies
- Fusion materials and technologies
- Microstructure and mechanical properties
- Corrosion Behavior and Inhibition
- Adhesion, Friction, and Surface Interactions
- Materials Engineering and Processing
- Magnetic Bearings and Levitation Dynamics
- Advanced materials and composites
- Force Microscopy Techniques and Applications
Sandia National Laboratories
2014-2025
Sandia National Laboratories California
2015-2023
Recent work suggests that thermally stable nanocrystallinity in metals is achievable several binary alloys by modifying grain boundary energies via solute segregation. The remarkable thermal stability of these has been demonstrated recent reports, with many exhibiting negligible growth during prolonged exposure to near-melting temperatures. Pt-Au, a proposed alloy consisting two noble metals, shown exhibit extraordinary resistance wear. Ultralow wear rates, less than monolayer material...
Diamond-like carbon (DLC) films were tribochemically formed from ambient hydrocarbons on the surface of a highly stable nanocrystalline Pt-Au alloy. A sliding contact between an alumina sphere and coated steel exhibited friction coefficients as low μ = 0.01 after dry in environments containing trace (ppb) organics. Ex situ analysis indicated that change coefficient was due to formation amorphous films, Raman spectroscopy elastic recoil showed these consist sp2/sp3 with much 20% hydrogen....
Abstract We present evidence of inverse Hall-Petch behavior for a single-phase high entropy alloy (CoCrFeMnNi) in ultra-high vacuum and show that it is associated with low friction coefficients (~0.3). Grain size measurements by STEM validate recently proposed dynamic amorphization model accurately predicts grain size-dependent shear strength the regime. Wear rates initially soft (coarse grained) material were shown to be remarkably (~10 –6 mm 3 /N-m), lowest any HEA tested an inert...
The natural convection boundary layer ( <?CDATA ${\delta }_{nc}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>δ</mml:mi> </mml:mrow> <mml:mi>n</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> ) and its influence on cathodic current in a galvanic couple under varying electrolytes as function of concentration (1 − 5.3 M NaCl) temperature (25 °C−45 °C) were understood. Polarization scans obtained quiescent conditions at defined...
The effects of gamma radiation on the performance two corrosion-resistant coatings applied to stainless-steel 304L (SS304L) surfaces are presented. Specifically, ability mitigate corrosion SS304L as a function dose received (0–1300 Mrad) and rate (176 compared 1054 rad/s) is evaluated using electrochemical methods, spectroscopy, microscopy. Coating A, an organic/inorganic hybrid coating consisting two-part silica ceramic component polymer linker was in comparison B, which utilized A topcoat...
We demonstrate inverse Hall-Petch behavior (softening) in pure copper sliding contacts at cryogenic temperatures. By kinetically limiting grain growth, it is possible to generate a quasi-stable ultra-nanocrystalline surface layer with reduced strength. In situ electrical contact resistance measurements were used determine size evolution the interface, agreement reports of softening highly nanotwinned copper. also show evidence direct correlation between and friction coefficient, validating...
Abstract The member stiffness and pressure distribution in a bolted joint is significantly influenced by the contact area of mechanical interface under prescribed preload force. This research explores influence as-built surface profiles for nominally flat interfaces C-Beam assembly with two well-defined regions. A high-fidelity finite element model created such that uncertainty minimized updating calibrating piece parts prior to procedure. then assembled preloaded evaluate stresses both...
Low friction is demonstrated with pure polycrystalline tantalum sliding contacts in both molecular dynamics simulations and ultrahigh vacuum experiments. This phenomenon shown to be correlated deformation occurring primarily through grain boundary can explained using a recently developed predictive model for the shear strength of metals. Specifically, low associated sizes at interface being smaller than critical, material-dependent value, where crossover from dislocation mediated plasticity...
Large-scale molecular dynamics simulations are used by Nicolas Argibay and co-workers in article number 1802026 to investigate the stress-dependent microstructural evolution of highly stable nanocrystalline alloys. They illustrate how an alloy Pt with 10 at% Au shows suppression grain growth at high tensile strains, resulting cohesive failure boundaries as primary mechanism.
Internal residual stresses and overall mechanical properties of thermoset resins are largely dictated by the curing process. It is well understood that fiber Bragg grating (FBG) sensors can be used to evaluate temperature cure induced strain while embedded during curing. Herein, an extension this work whereby we use FBGs as a probe for minimizing internal stress unfilled filled Epon 828/DEA resin. Variables affecting including cycle, mold (release), adhesion promoting additives will...
<title>Abstract</title> In this study we present a replication method to determine surface roughness and identify features when sample cannot be directly analyzed by conventional techniques. As demonstration, was applied an unused spent nuclear fuel dry storage canister variation across different features. study, initial material down-selection performed the best molding agent determined that non-modified Polytek PlatSil23-75 provided most accurate representation of while providing good...
The degradation in electrical contact resistance of a pair sliding while submerged silicone fluid has been investigated. While the contamination contacts by vapors or migrating species at elevated temperature due to decomposition electric arcs is well known, present mechanism appears arise from chemical reactions room temperature, catalyzed presence freshly-abraded metal surface. As result these reactions, deposit containing Si, C and O forms vicinity mechanical contact. specific metals...