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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

High hardness and oxidation-resistant Cr-containing medium entropy ZrTaW diboride

This study reports the successful synthesis of a Cr-containing (Zr 0.30 Ta 0.34 Cr 0.06 W 0.30 )B 2 medium-entropy boride (MEB) via an in-situ reactive borothermal reduction route from oxide precursors. High-energy ball milling was employed to homogenize the precursor mixture prior to reactive densification. X-ray diffraction confirmed the formation of a predominantly AlB₂-type hexagonal diboride structure together with a secondary (W X , M 1-X )B monoboride phase. Microstructural characterization revealed compositional heterogeneity and localized W-rich regions associated with the secondary phase. The synthesized medium-entropy boride exhibited enhanced mechanical properties, which are attributed to lattice distortion and solid-solution strengthening effects. Thermogravimetric analysis revealed complex multistage oxidation behavior, and the oxidation resistance was compared with conventional ultra-high-temperature diborides. The results demonstrate the strong relationship between oxide-derived processing, compositional complexity, phase evolution, and oxidation behavior, highlighting the potential of medium-entropy borides for high-temperature structural applications

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of alloying with Sc, Nb and Zr on reduction-diffusion synthesis of magnetically hard Sm(Fe,Co,Ti) 12 -based monocrystalline powders

Powders of Sm(Fe,Co) 11.2 Ti 0.8 alloys modified with Sc, Nb and Zr, as well as with additional Ti were prepared by reducing mechanically activated raw oxides with Ca metal in the furnace preheated to 990–1250 °C. Expansion of the crystal lattice upon introduction of Nb or additional Ti implies that atoms of these elements replace the smaller Fe atoms in the tetragonal ThMn 12 -type structure. On the other hand, contraction of the lattice upon introduction of Sc or Zr was smaller than what was expected for replacement of the Sm atoms, which suggests that the Sc and Zr atoms replace both the Sm and Fe atoms. Washing away the reduction byproducts expands the crystal lattice of the 1:12 particles and increases their coercivity. The lattice expansion associated with the washing is believed to be caused by interstitial H atoms; more research, however, is needed to establish the mechanism(s) of the washing effect on the coercivity. The earlier reported development of a high coercivity in zirconium-modified monocrystalline particles achieved by increasing the reduction annealing temperature to ≈1200 °C was similarly characteristic of the particles modified with Sc (the coercivity reaches 11.5 kOe) and Nb (8.1 kOe), but not for the particles prepared with additional Ti where the maximum coercivity of 8.3 kOe develops for a lower annealing temperature. Furthermore, it is concluded that Sc, Nb and Zr modify the high-temperature phase equilibria of the Sm(Fe,Co) 11.2 Ti 0.8 alloys allowing for an effective high-temperature processing, whereas the alloy coercivity increases with the synthesis temperature through a different, still unknown mechanism which may involve suppression of the defects specific to the 1:12 crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of magnetic field annealing on the hard magnetic properties of milled Nd-Fe-B powders

In this study, we report the effect of magnetic field annealing (MA) in relieving the stress induced during the milling of Nd-Fe-B sintered magnets. The effect of MA processing parameters and particle size on the magnetic properties were investigated. Based on the results, magnetic field annealing is more effective in improving the magnetic properties of larger size particles, compared to finer particles. Our computational study on the role of particle surface defects in bi-modal particle distribution agrees with results obtained experimentally. In conclusion, magnetic field annealed powder has been successfully used to develop 4.6 g.cm -3 density bonded magnets with 75 vol% of magnetic powder and polyamide 12 (nylon 12) polymer binder resulting in 11.3 MGOe energy product.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Countdown to perovskite space launch: Guidelines to performing relevant radiation-hardness experiments

Perovskite photovoltaics (PVs) are under intensive development for promise in terrestrial energy production. Soon, the community will find out how much of that promise may become reality. Perovskites also open new opportunities for lower cost space power. However, radiation tolerance of space environments requires appropriate analysis of relevant devices irradiated under representative radiation conditions. We present guidelines designed to rigorously test the radiation tolerance of perovskite PVs. We review radiation conditions in common orbits, calculate nonionizing and ionizing energy losses (NIEL and IEL) for perovskites, and prioritize proton radiation for effective nuclear interactions. Low-energy protons (0.05-0.15 MeV) create a representative uniform damage profile, whereas higher energy protons (commonly used in ground-based evaluation) require significantly higher fluence to accumulate the equivalent displacement damage dose due to lower scattering probability. Furthermore, high-energy protons may "heal" devices through increased electronic ionization. These procedural guidelines differ from those used to test conventional semiconductors.

14 SOLAR ENERGY↗
DOE OSTI2020

Transverse spin effects in hard semi-inclusive collisions

The nucleons (protons and neutrons) are by far the most abundant form of matter in our visible Universe; they are composite particles made of quarks and gluons, the fundamental quanta of Quantum Chromo Dynamics (QCD). The usual interpretation of the nucleon dynamics in high energy interactions is often limited to a simple one-dimensional picture of a fast moving nucleon as a collection of co-linearly moving quarks and gluons (partons), interacting accordingly to perturbative QCD rules. However, massive experimental evidence shows that, in particular when transverse spin dependent observables are involved, such a simple picture is not adequate. The intrinsic transverse motion of partons has to be taken into account; this opens the way to a new, truly 3-dimensional (3D) study of the nucleon structure. A review of the main experimental data, their interpretation and understanding in terms of new transverse momentum dependent partonic distributions, and the progress in building a 3D imaging of the nucleon is presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗