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Results for “phase separation”

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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Modeling Henry's law and phase separations of water–NaCl–organic mixtures with solvation and ion-pairing

Empirical measurements of solution vapor pressure of ternary acetonitrile (MeCN) H 2 O–NaCl–MeCN mixtures were recorded, with NaCl concentrations ranging from zero to the saturation limit, and MeCN concentrations ranging from zero to an absolute mole fraction of 0.64. After accounting for speciation, the variability of the Henry's law coefficient at vapor–liquid equilibrium (VLE) of MeCN ternary mixtures decreased from 107% to 5.1%. Solute speciation was modeled using a mass action solution model that incorporates solute solvation and ion-pairing phenomena. Two empirically determined equilibrium constants corresponding to solute dissociation and ion pairing were utilized for each solute. When speciation effects were considered, the solid–liquid equilibrium of H 2 O–NaCl–MeCN mixtures appear to be governed by a simple saturation equilibrium constant that is consistent with the binary H 2 O–NaCl saturation coefficient. Further, our results indicate that the precipitation of NaCl in the MeCN ternary mixtures was not governed by changes in the dielectric constant. Our model indicates that the compositions of the salt-induced liquid–liquid equilibrium (LLE) boundary of the H 2 O–NaCl–MeCN mixture correspond to the binary plateau activity of MeCN, a range of concentrations over which the activity remains largely invariant in the binary water–MeCN system. Broader comparisons with other ternary miscible organic solvent (MOS) mixtures suggest that salt-induced liquid–liquid equilibrium exists if: (1) the solution displays a positive deviation from the ideal limits governed by Raoult's law; and (2) the minimum of the mixing free energy profile for the binary water-MOS system is organic-rich. Finally, this work is one of the first applications of speciation-based solution models to a ternary system, and the first that includes an organic solute.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Reconstruction of the “phase separation – ordering” type and specific heat in carbon nanotubes

The low-temperature behavior of the specific heat in disordered nanotubes strongly depends on structure changes and was not explained by the phonon contribution. Expression for electronic specific heat was carried out taking into account the multiple elastic scattering of electrons on impurities and structural inhomogeneities of short-range order type, it includes dependence on diameter of nanotube, concentration of impurities, parameters of short-range order (structural heterogeneity) and temperature. Anomalous low-temperature behavior of the specific heat of disordered CNT is shown to have electronic nature and may be associated with the electrons that are involved in restructuring.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Low field colossal anisotropic magnetoresistance in spatially confined electronically phase separated La{sub 0.3}Pr{sub 0.4}Ca{sub 0.3}MnO{sub 3} microbridges

Colossal in-plane anisotropic magnetoresistance (AMR) of >16 000% has been engineered in spatially confined La{sub 0.3}Pr{sub 0.4}Ca{sub 0.3}MnO{sub 3} films. Recalling that typical AMR values in films are only a few percent, these results mark an astonishing increase that might potentially lead to fabrication of manganite-based switching and sensor devices. The unique colossal behavior is discussed within the context of anisotropic domain growth.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Development of a scanning time of flight microscope and its application to the study of charge transport in phase separated structured organic semiconductors

We describe a tool for studying the two-dimensional spatial variation in electronic properties of organic semiconductors: the scanning time-of-flight microscope (STOFm). The STOFm simultaneously measures the transmittance of polarized light and time-of-flight current transients with a pixel size <30 μm, making it especially valuable for studies of the correlations of structure with charge generation and transport in liquid crystalline organic semiconductors (LC OSCs). Adapting a previously developed photopolymerization technique, we characterize the instrument using patterned samples of a LC OSC bounded by a non-semiconducting polymer matrix.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Optically transparent, mechanically durable, nanostructured superhydrophobic surfaces enabled by spinodally phase-separated glass thin films

Inspired by highly non-wetting natural biological surfaces (e.g., lotus leaves and water strider legs), artificial superhydrophobic surfaces that exhibit water droplet contact angles exceeding 150o have previously been constructed by utilizing various synthesis strategies.[ , , ] Such bio-inspired, water-repellent surfaces offer significant potential for numerous uses ranging from marine applications (e.g., anti-biofouling, anti-corrosion), anti-condensation (e.g., anti-icing, anti-fogging), membranes for selective separation (e.g., oil-water, gas-liquid), microfluidic systems, surfaces requiring reduced maintenance and cleaning, to applications involving glasses and optical materials.[ ] In addition to superhydrophobic attributes, for integration into device systems that have extended operational limits and overall improved performance, surfaces that also possess multifunctional characteristics are desired, where the functionality should match to the application-specific requirements.

Nano-structure↗
DOE OSTI2014

Two spatially separated phases in semiconducting Rb 0.8 Fe 1.5 S 2

We report neutron scattering and transport measurements on semiconducting Rb 0.8 Fe 1.5 S 2 , a compound isostructural and isoelectronic to the well-studied A 0.8 Fe y Se 2 (A = K, Rb, Cs, Tl/K) superconducting systems. Both resistivity and DC susceptibility measurements reveal a magnetic phase transition at T = 275 K. Neutron diffraction studies show that the 275 K transition originates from a phase with rhombic iron vacancy order which exhibits an in-plane stripe antiferromagnetic ordering below 275 K. In addition, the stripe antiferromagnetic phase interdigitates mesoscopically with an ubiquitous phase with √5 x√5 iron vacancy order. This phase has a magnetic transition at T N = 425 K and an iron vacancy order-disorder transition at T S = 600 K. These two different structural phases are closely similar to those observed in the isomorphous Se materials. Based on the close similarities of the in-plane antiferromagnetic structures, moments sizes, and ordering temperatures in semiconducting Rb 0.8 Fe 1.5 S 2 and K 0.81 Fe 1.58 Se 2 , we argue that the in-plane antiferromagnetic order arises from strong coupling between local moments. Superconductivity, previously observed in the A 0.8 Fe y Se 2₋ z S z system, is absent in A 0.8 Fe 1.5 S 2 , which has a semiconducting ground state. We discuss the implied relationship between stripe and block antiferromagnetism and superconductivity in these materials as well as a strategy for further investigation.

36 MATERIALS SCIENCE↗