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At least 163 records · Page 9

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DOE OSTI2026

Mechanical characterization of fine-grain dispersion-strengthened tungsten as a plasma facing material

Field-Assisted Sintering Technology (FAST) was used to produce fine-grained, dispersion-strengthened tungsten (W) materials. Investigated materials 4138, 4353, and 4355 composed of 3 wt% ZrC sintered at 1800 °C, 5 wt% ZrC sintered at 1800 °C, and 3 wt% ZrC sintered at 2000 °C, respectively. They were compared against ITER-grade W. A series of mechanical and thermal property testing and microstructure studies were conducted to study them as a potential plasma facing material (PFM) for fusion reactors. Hardness testing showed that manufacturing conditions substantially altered hardness. Material 4355 had an average HV10 value of 497.2 ± 16.8, slightly higher than ITER-grade at 378.5 ± 40.3. However, material 4353 was substantially higher with an HV10 value of 738.9 ± 31.7 over the investigated temperature range. Electron Backscatter Diffraction (EBSD) analysis showed that FAST produced substantially smaller grains than the hot-rolled ITER-grade W material, offering notable control over grain size. Materials 4353 and 4355 had grain sizes of 0.44 ± 0.20 µm and 3.67 ± 0.89 µm, respectively, whereas ITER-grade 27.14 ± 19.76 µm at room temperature. The fine grain structures showed no net coarsening after 1 hr. anneals up to 1800 °C, several hundred degrees above the 1100 – 1500 °C recrystallization range reported for conventional W. Inverse application of the Zener pinning relationship to the measured grain sizes indicates that these two FAST sintering conditions produce markedly different effective dispersoid populations, with effective particle diameters of approximately 90 nm at a peak sintering temperature of 1800 °C and approximately 460 nm at 2000 °C, respectively. This result demonstrates that the FAST thermal condition itself, and not the nominal ZrC content alone, governs the pinning effectiveness of the dispersion. Thermal diffusivity measurements support this finding independently. Materials of identical composition sintered at different temperatures differ by approximately 19% in measured thermal diffusivity with statistically indistinguishable density, while materials of different composition and sintering temperature converge to within approximately 2%. At a representative divertor heat flux of 10 MW/m², the lower thermal conductivity of the fine-grained materials corresponds to approximately 28 to 33 °C per millimeter of armor thickness relative to ITER-grade W, traded against a substantially larger margin to recrystallization-driven degradation. While high temperature tensile testing revealed likely contamination that motivates refinement of the manufacturing process, FAST-produced, fine-grained, dispersion-strengthened W offers process-controlled microstructural stability well above the operating temperatures of conventional W and supports its continued development as a PFM for economically viable commercial fusion power.

Parker, Gabe [ORNL] (ORCID:0000000190394100)↗

DOE OSTI2026

Dispersion of high oxygen permeability ionomers in water-propanol solutions

There is a growing interest in high oxygen permeability ionomers (HOPI) for better-performing proton exchange membrane fuel cell (PEMFC) catalyst layers. In this study, we used small-angle x-ray scattering (SAXS) to analyze dispersions of two types of perfluorinated sulfonic acid (PFSA) ionomers and a HOPI in water and propanol solvents, at concentrations between 1 wt% and 15 wt%. HOPI dispersions exhibited the interference peak typical of ionomers; by separately fitting the peak and higher- q regions with several models, we demonstrated that HOPI aggregates have a closer average spacing than conventional PFSA ionomers, and smaller aggregate size when assuming a cylindrical geometry. By measuring conventional PFSA ionomers with two side chain lengths and several equivalent weights, we showed that these side chain parameters alone did not explain the differences in aggregate spacing or size. In addition, the pattern was present whether samples were prepared in a 50/50 water/propanol or a more propanol-rich mixture. As such, the structural differences of HOPI could be due to its different backbone monomer. A better understanding of the influence of the HOPI chemistry on dispersion properties could help explain the ink structure and drying characteristics of HOPI observed in prior work. Future study of ionomer-catalyst mixtures, such as measuring ionomer adsorption to carbon, would help elucidate the role of ionomer from ink formulation to the cast electrode.

Aquivion↗

DOE OSTI2026

In-situ synchrotron X-ray investigation of phase evolution in gas atomized powder enabling manufacturing of nanoscale oxide-dispersion strengthened ferritic steels

Here, we present an investigation of Fe-14Cr-3W-0.4Y-0.4Zr-0.18Ti (wt.%) as a reduced-activation oxide-dispersion strengthened (ODS) ferritic steel, an alternative to the “14YWT” structural alloys designed for nuclear energy applications. Gas atomization reaction synthesis (GARS) was used to produce these Zr-modified powders with a non-equilibrium (metastable) phase that enable a heat treatment (delayed) route for producing nanoscale oxide-dispersion strengthening. In situ synchrotron X-ray diffraction and transmission electron microscopy were used to analyze phase evolution as a function of temperature and time, revealing formation of highly dispersed oxide nanoprecipitate phases at temperatures above those needed for powder consolidation and shaping of components. This would allow fabrication of net-shape parts using conventional powder-processing methods prior to thermal activation of a reaction producing nanocrystalline Y-(Ti, Zr)-O particles, with a size of 20 ± 7 nm. These results can inform processing of tubes, cladding, sheets, and plates for use in advanced fission and fusion reactors.

In-situ synchrotron X-ray diffraction↗

DOE OSTI2025

Adsorption and Chromatographic Behavior of Dispersed Sodium Bismuthate Systems for the Separation of Americium from Curium

The selective partitioning of americium (Am) and curium (Cm) is integral for nuclear science areas such as the nuclear fuel cycle, stockpile stewardship, and isotope production but remains a long-standing radioanalytical challenge due to nearly identical chemical properties. Differences in redox chemistry can be exploited since Am can be oxidized to the hexavalent oxidation state. Sodium bismuthate (NaBiO 3 ) exhibits favorable oxidation and ion exchange characteristics conducive to a rapid and efficient Am/Cm chromatographic separation. Contact of nitric acid with NaBiO 3 was shown to significantly decrease the nitric acid concentration and solution volume. The adsorption, kinetic, and chromatographic behavior of Am and Cm in systems that disperse NaBiO3 in filter aids was evaluated. Further, dispersion of NaBiO 3 increased separation factors to over 100, with rapid kinetics achieved within 1 min of contact and sustained for at least 2 h. The adsorption capacity was more than doubled from 0.066 mequiv g –1 for solid NaBiO 3 alone to 0.149(6) and 0.156(9) meq g –1 when dispersed in Celite 545 and silica gel, respectively. Complete separation was achieved in all systems with ~100% recovery in the respective eluted fractions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Dispersion Relations Alone Cannot Guarantee Causality

We show that linear superpositions of plane waves involving a single-valued, covariantly stable dispersion relation ω ( k ) always propagate outside the light cone unless ω ( k ) = a + b k . This implies that there is no notion of causality for individual dispersion relations since no mathematical condition on the function ω ( k ) (such as the front velocity or the asymptotic group velocity conditions) can serve as a sufficient condition for subluminal propagation in dispersive media. Instead, causality can only emerge from a careful cancellation that occurs when one superimposes all the excitation branches of a physical model. This happens automatically in local theories of matter that are covariantly stable. Hence, we find that the need for nonhydrodynamic modes in relativistic fluid mechanics is analogous to the need for antiparticles in relativistic quantum mechanics. Published by the American Physical Society 2024

Physics↗

DOE OSTI2025

Dispersion Leverage Coronagraph: a nulling coronagraph for use on primary objective grating telescopes

Here, we present the Dispersion Leverage Coronagraph (DLC), a variation of the Achromatic Interfero Coronagraph (AIC) that is designed for optical systems featuring large, dispersive primary objective gratings. DLC was originally designed for the Diffractive Interfero Coronagraph Exoplanet Resolver (DICER), a notional 20 m class infrared space telescope utilizing the enhanced one-dimensional angular resolution of large diffraction gratings to discover and characterize near-Earth exoplanets. Here we develop the theoretical foundation for DLC, and apply it to DICER as an example use case. We derive important properties of the DLC system, including focal plane transmission maps, stellar leakage, residual optical path difference tolerance, and pointing error/jitter considerations. Ultimately, we found that DLC effectively nulls an on-axis target across the entire spectrum in the focal plane, allowing for 2D/λ diffraction-limited imaging. It requires asymmetrical fine-guidance tolerances on pointing error/jitter. We work through a benchmark DICER design, explaining the need for a second disperser to reduce background from Zodiacal light, and showing that it could plausibly find and characterize ∼4 nearby, habitable exoplanets around Sun-like stars in a 7-year mission; about 30% of the habitable exoplanets within 8 pc were found in our simulation. The DLC may be useful for any application requiring extremely high-resolution, close companion spectroscopy.

AIC↗

DOE OSTI2024

Dispersive nonreciprocity between a qubit and a cavity

The dispersive interaction between a qubit and a cavity is ubiquitous in circuit and cavity quantum electrodynamics. It describes the frequency shift of one quantum mode in response to excitations in the other and, in closed systems, is necessarily bidirectional, i.e., reciprocal. Here, we present an experimental study of a nonreciprocal dispersive-type interaction between a transmon qubit and a superconducting cavity, arising from a common coupling to dissipative intermediary modes with broken time reversal symmetry. We characterize the qubit-cavity dynamics, including asymmetric frequency pulls and photon shot noise dephasing, under varying degrees of nonreciprocity by tuning the magnetic field bias of a ferrite component in situ. We introduce a general master equation model for nonreciprocal interactions in the dispersive regime, providing a compact description of the observed qubit-cavity dynamics agnostic to the intermediary system. Our result provides an example of quantum nonreciprocal phenomena beyond the typical paradigms of non-Hermitian Hamiltonians and cascaded systems.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2024

Nonlinear propagation of chirped laser pulses through a dispersive and turbulent atmosphere

The evolution of ultrashort laser pulses in dispersive, turbulent, nonlinear, and dissipative media is discussed in connection with nonlinear self-focusing collapse and the onset of laser filamentation. In quiescent air, a laser pulse propagating with a peak power greater than a critical power for self-focusing will undergo a catastrophic, transverse collapse until the intensity is large enough for photoionization. At this point, self-focusing is arrested and balanced by plasma refraction, forming a laser filament. By applying an appropriate chirp, the dispersive properties of the medium can be used to enhance this process and control its onset, and to counter dissipative effects such as molecular absorption and atmospheric scattering. This paper presents an analysis of the effect of atmospheric turbulence on the propagation of nonlinear pulses with dispersion compensation (chirp). Furthermore, the analytical results are compared with wave optics simulations and found to be in reasonable agreement as long as the pulse maintains a near-Gaussian spatiotemporal profile.

47 OTHER INSTRUMENTATION↗

DOE OSTI2026

Dispersion Suppression for Wedge-Based Final Cooling at a 10 TeV Muon Collider

Achieving a luminosity of $\gtrsim 10^{34} cm^{-2} s^{-1}$ in a $10 \text{ } TeV$ Muon Collider, given the short lifetime of a muon, requires reducing the 6D emittance of the muon beam through a process known as ionization cooling. In the final stage of this cooling process, the transverse emittance must be reduced to $22 \text{ } μm$, typically by allowing longitudinal emittance growth up to downstream acceptance limits. While the current International Muon Collider Collaboration designs involve $40 \text{ } T$ solenoids to reach the transverse emittance target, such high-field solenoids come with several challenges, including mechanical stress management, quench protection, and potential limitations in relying on High Temperature Superconductor technology. Designed as an alternative to using such solenoids while simultaneously reaching target transverse emittance, the previously proposed wedge-based, reverse emittance-exchange cooling scheme requires excellent dispersion suppression. In this study, we design and simulate a dispersion suppressor channel for the wedge-based final cooling design that reduces dispersion in the target direction to a target value of $D_x \sim 0.001 \text{ } m$.

Karaaslan, I. [Chicago U.] (ORCID:0000000337849879↗

DOE OSTI2024

Atomic Diffusivities of Yttrium, Titanium and Oxygen Calculated by Ab Initio Molecular Dynamics in Molten 316L Oxide-Dispersion-Strengthened Steel Fabricated via Additive Manufacturing

Oxide-dispersion-strengthened (ODS) steels have long been viewed as a prime solution for harsh environments. However, conventional manufacturing of ODS steels limits the final product geometry, is difficult to scale up to large components, and is expensive due to multiple highly involved, solid-state processing steps required. Additive manufacturing (AM) can directly incorporate dispersion elements (e.g., Y, Ti and O) during component fabrication, thus bypassing the need for an ODS steel supply chain, the scale-up challenges of powder processing routes, the buoyancy challenges associated with casting ODS steels, and the joining issues for net-shape component fabrication. In the AM process, the diffusion of the dispersion elements in the molten steel plays a key role in the precipitation of the oxide particles, thereby influencing the microstructure, thermal stability and high-temperature mechanical properties of the resulting ODS steels. In this work, the atomic diffusivities of Y, Ti, and O in molten 316L stainless steel (SS) as functions of temperature are determined by ab initio molecular dynamics simulations. The latest Vienna Ab initio Simulation Package (VASP) package that incorporates an on-the-fly machine learning force field for accelerated computation is used. At a constant temperature, the time-dependent coordinates of the target atoms in the molten 316L SS were analyzed in the form of mean square displacement in order to obtain diffusivity. The values of the diffusivity at multiple temperatures are then fitted to the Arrhenius form to determine the activation energy and the pre-exponential factor. Given the challenges in experimental measurement of atomic diffusivity at such high temperatures and correspondingly the lack of experimental data, this study provides important physical parameters for future modeling of the oxide precipitation kinetics during AM process.

Chemistry↗

NASA NTRS1971

Fog dispersal technology.

The state-of-the-art in fog dispersal technology is briefly discussed. Fog is categorized as supercooled fog, occurring in air temperatures below freezing, and warm fog, occurring at above-freezing temperatures. Operational techniques are available to disperse supercooled fog in the airport area. It is much more difficult to cope with warm fog. Various known concepts to disperse warm fog are evaluated as to their operational merits. The most effective concept for immediate use involves heating the air to cause fog evaporation. Use of helicopter downwash has some application, possibly complementing the promising concept of seeding with sized hygroscopic particles. These latter two concepts appear to have future application, pending further research. The concept using polyelectrolytes is of uncertain value, lacking both a scientific explanation and a substantive evaluation of reported operational successes.

Mcgowan, W. A.↗

NASA NTRS1973

Retrieval of dispersive and convective transport phenomena in fluids using stationary and nonstationary time domain analysis

Simultaneously occuring dispersive and convective components of fluid kinematics are obtained by a time domain analysis of optically retrieved temporal histories of the transport phenomena. Utilizing triangulation of collimated optical fields of view from two radiometers to obtain the temporal histories of the intensity fluctuations associated with the transport phenomena has enabled investigators to retrieve the local convective transport by employing correlation statistics. The location of the peak in the covariance curve determines the transit time from which the convection velocity is calculated; whereas, the change in shape of the peak in the covariance curve determines the change in average frequency of the wave packet from which the dispersion velocity is calculated. Thus, two-component analysis requires the maximum possible enhancement of the delineation for the transport. The convection velocity is the result of a fixed reference frame calculation whereas, the dispersion velocity is the result of a moving reference frame calcuation.

Stephens, J. B.↗

NASA NTRS1973

Dispersion and dilution of jet aircraft exhaust at high-altitude flight conditions

A method is presented for estimating the dispersion and dilution of jet aircraft exhaust from aircraft passage through times on the order of weeks thereafter. In the near wake of the aircraft, the solution is that for round turbulent jets in a parallel flow. More rapid dispersion due to atmospheric effects begins when the scale-dependent eddy viscosity becomes larger than the turbulent jet eddy viscosity. In the far wake region, the solution approaches that for scale-dependent dispersion from a point source moving with the aircraft. Calculations are presented for supersonic aircraft at high altitude flight conditions.

Holdeman, J. D.↗

NASA NTRS1974

Dispersion and dilution of jet aircraft exhaust at high-altitude flight conditions

Holdeman, J. D.↗

NASA NTRS1974

Studies of aircraft wake chemistry and dispersion

Use of aerospace technology to study aircraft wakes is reviewed. It is shown how aerospace vehicles can be used to provide data for increased understanding of the atmosphere and of aircraft exhaust trails where knowledge is inadequate to evaluate fully the potential impact of the engine emissions. Models of aircraft near-field exhaust wakes are characterized by jet, vortex, and dispersion regimes. Wake growth in the jet regime is self-determined and rapid, whereas further spreading is inhibited in the vortex regime because of circulating vortex motion. Wake diffusion in the dispersion regime is initially influenced by aircraft induced turbulence but is dominated later by small-scale atmospheric turbulence. Computed fluid mechanical results show the importance of effects such as wake buoyancy, wind shear, turbulence, and traffic corridor exhaust buildup on dispersion of the wake. In the jet regime the exhaust characteristics and thermochemistry serve to illustrate initial chemical changes involving potential pollutant species.

Poppoff, I. G.↗

NASA NTRS1976

Time dispersion of energetic solar particles, unexpected velocity and species dependence

The intensity-time behavior for protons and helium, as well as for carbon, oxygen and iron ions was measured following the 1974 September 19 solar flare for energies between 0.5 and approximately 5 MeV per nucleon. The profiles displayed a time dispersion which is inversely proportional to velocity for each individual species. In addition, at a given velocity the time dispersion also depended on the charge to mass ratio of the ion. Based on this latter dependence, it was concluded that while carbon and oxygen are essentially fully stripped, iron nuclei are not, having an effective charge Q = 10 + or - 5. The observed dispersion cannot be explained by purely rigidity dependent diffusive propagation.

Gallagher, J. J.↗

NASA NTRS1975

Velocity dispersions in galaxies. IV - The nucleus of NGC 1068

A high-resolution spectrum of the Seyfert galaxy NGC 1068, obtained with an integrating television system, is compared with the spectrum of a KO III star (delta Tau) to derive the line-of-sight velocity dispersion of the stars in the galactic nucleus. An Fe I absorption line observed at 4059.7 A yields a velocity dispersion of 150 (plus or minus 50) km/sec. An upper limit for the nuclear mass is derived in terms of this velocity dispersion, an estimated nuclear radius of 136 pc, and a Hubble constant of 50 km/sec per Mpc. The results, 14 (+10, -8) by 10 to the 8th power solar masses, is shown to be consistent with a number of quasar models scaled down in luminosity to provide the energy source for a Seyfert nucleus. Strong H and K interstellar absorption lines superposed on the spectrum of NGC 1068 are analyzed.-

Richstone, D. O.↗

NASA NTRS1976

Time dispersion of energetic solar particles - Unexpected velocity and species dependence

The intensity-time behavior for protons and alpha-particles, as well as for carbon, oxygen, and iron ions, has been measured following the solar flare of September 19, 1974, for energies between 0.5 and about 5 MeV per nucleon. The profiles display a time dispersion which is inversely proportional to velocity for each individual species. In addition, at a given velocity the time dispersion also depends on the charge-to-mass ratio of the ion. Based on this latter dependence, it is concluded that while carbon and oxygen are essentially fully stripped, iron nuclei are not, having an effective charge of 10 plus or minus 5. The observed dispersion cannot be explained by purely rigidity-dependent diffusive propagation.

Ogallagher, J. J.↗