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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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Yttrium Manganese Oxide Phase Stability and Selectivity Using Lithium Carbonate Assisted Metathesis Reactions
Abstract not provided
Phase Stability and Electronic Structure of Tin Sulfide Compounds for Li-ion Batteries
Not provided.
Linker Length-Dependent Control of Gemini Surfactant Aqueous Lyotropic Gyroid Phase Stability
Abstract not provided
Surface Phase Stability of Fe 2 O 3 (001) in Hydrogen Reducing Environments: A DFT and XPS Analysis
Here, this study combines density functional theory (DFT) and ab initio thermodynamics calculations with X-ray photoelectron spectroscopy (XPS) investigations to identify the reduction properties of the Fe 2 O 3 (001) surface with implications for corrosion resistance, hydrogen transport, and energy safety. Ab initio thermodynamics modeling predicts fully hydroxylated surface stability across a broad range of pressures (1 × 10 –23 to 1 × 10 5 mbar) and temperatures below 700 K, consistent with previous experimental studies. Above 800 K, exposures to 1 × 10 –4 mbar H 2 , 1 × 10 –4 mbar O 2 , or 1 × 10 –4 mbar H 2 + 1 × 10 –4 mbar O 2 each yield unique XPS signals indicating a loss of −OH coverage, aligning with DFT predictions. Insight into the mechanism of reduction as a function of H 2 exposure is provided, as well as conditions that promote further reduction toward Fe 3 O 4 . Theoretical and experimental investigations indicate the ability to maintain the Fe 2 O 3 protective layer of iron oxides that have been exposed to H 2 environments by including trace amounts of aqueous O2.
Decreasing Structural Dimensionality of Double Perovskites for Phase Stabilization toward Efficient X-ray Detection
Not provided.
Insights into the Growth Orientation and Phase Stability of Chemical-Vapor-Deposited Two-Dimensional Hybrid Halide Perovskite Films
Chemical vapor deposition (CVD) offers a large-area, scalable, and conformal growth of perovskite thin films without the use of solvents. Low-dimensional organic–inorganic halide perovskites, with alternating layers of organic spacer groups and inorganic perovskite layers, are promising for enhancing the stability of optoelectronic devices. Moreover, their multiple quantum-well structures provide a powerful platform for tuning excitonic physics. Here, in this work, we show that the CVD process is conducive to the growth of 2D hybrid halide perovskite films. Using butylammonium (BA) and phenylethylammonium (PEA) cations, the growth parameters of BA 2 PbI 4 and PEA 2 PbI 4 and mixed halide perovskite films were first optimized. These films are characterized by well-defined grain boundaries and display characteristic absorption and emission features of the 2D quantum wells. X-ray diffraction (XRD) and a noninteger dimensionality model of the absorption spectrum provide insights into the orientation of the crystalline planes. Unlike BA 2 PbI 4 , temperature-dependent photoluminescence measurements from PEA 2 PbI 4 show a single excitonic peak throughout the temperature range from 20 to 350 K, highlighting the lack of defect states. These results further corroborate the temperature-dependent synchrotron-based XRD results. Furthermore, the nonlinear optical properties of the CVD-grown perovskite films are investigated, and a high third harmonic generation efficiency is observed.
Crystallization, Phase Stability, Microstructure, and Chemical Bonding in Ga 2 O 3 Nanofibers Made by Electrospinning
Not Available
Phase stability and dynamics of entangled polymer-nanoparticle composites
Nanoparticle–polymer composites, or polymer–nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.
Phase stability, electronic, mechanical, lattice distortion, and thermal properties of complex refractory-based high entropy alloys TiVCrZrNbMoHfTaW with varying elemental ratios
This study examines the intricate area of refractory-based high entropy alloys (RHEAs), focusing on a series of complex compositions involving nine diverse refractory elements: Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.
Evidence of improved ferroelectric phase stabilization in Nd and Sc co-substituted BiFeO{sub 3}
Polycrystalline BiFeO{sub 3} and Bi{sub 0.9}Nd{sub 0.1}Fe{sub 1−x}Sc{sub x}O{sub 3} (x = 0, 0.05, and 0.10) multiferroic compounds were prepared using conventional solid-state route. X-ray diffraction studies and Raman measurements indicated that the compounds were crystallized in rhombohedral structure with R3c space group. Weak ferromagnetism was induced due to the suppression of canted spin structure in the substituted compounds. Both remanent magnetization (M{sub r}) and coercive field (H{sub c}) were enhanced in Nd and Sc substituted compounds. Further, Néel temperature T{sub N} was decreased from 644 K for BiFeO{sub 3} to 550 K for Bi{sub 0.9}Nd{sub 0.1}Fe{sub 0.9}Sc{sub 0.1}O{sub 3} compound due to weakening of magnetic exchange interactions between B-site cations in the substituted compounds. Enhanced and nearly well saturated electrical polarizations were observed in Sc substituted compounds, which are attributed to the strengthening of covalent hybridization between Bi and O ions and reduction in oxygen vacancies. The remnant polarization was enhanced to 12.5 μC/cm{sup 2} in Bi{sub 0.9}Nd{sub 0.1}Fe{sub 0.9}Sc{sub 0.1}O{sub 3} compound. Impedance studies revealed that insulating character of substituted compounds is enhanced and electrical relaxations are of non-Debye type.