Search NASA⌕ Search

SEARCH · Search NASA

Results for “Transport Properties”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Deciphering the effect of traps on electronic charge transport properties of methylammonium lead tribromide perovskite

Halide perovskites have undergone remarkable developments as highly efficient optoelectronic materials for a variety of applications. Several studies indicated the critical role of defects on the performance of perovskite devices. However, the parameters of defects and their interplay with free charge carriers remain unclear. In this study, we explored the dynamics of free holes in methylammonium lead tribromide (MAPbBr 3 ) single crystals using the time-of-flight (ToF) current spectroscopy. By combining ToF spectroscopy and Monte Carlo simulation, three energy states were detected in the bandgap of MAPbBr 3 . In addition, we found the trapping and detrapping rates of free holes ranging from a few microseconds to hundreds of microseconds. Contrary to previous studies, we revealed a strong detrapping activity of traps. We showed that these traps substantially affect the transport properties of MAPbBr 3 , including mobility and mobility-lifetime product. Our results provide an insight on charge transport properties of perovskite semiconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Completion of Transport Property Measurements on Multiple Actinide Fluoride Mixtures

One of the missions of the US Department of Energy’s Office of Nuclear Energy (DOE-NE) Molten Salt Reactor (MSR) Campaign under the Advanced Reactor Technology program has been to experimentally measure thermophysical properties of MSR-relevent salt systems, with the intent of supporting the development of the Molten Salt Thermal Properties Database (MSTDB). This database is jointly funded by the DOE-NE Nuclear Energy Advanced Modeling and Simulation Program and the MSR Campaign. Multiple DOE national laboratories, including Oak Ridge National Laboratory (ORNL), have been conducting measurements of thermophysical properties to support MSTDB development and provide MSR developers with access to new data that has been measured using modern methodologies and more advanced sample characterization techniques. These data may either fill gaps in the database or provide updated higher quality data to replace legacy data. Researchers at ORNL have recognized significant gaps in the transport property data of actinide-bearing fluoride salt systems of MSR industry interest. Moreover, for the data present in MSTDB in this category, the uncertainty margins are generally high, leading to questionability in our current understanding of the thermophysical characterization of actinide fluoride mixtures. As such, the focus of this study has been to generate new transport property data of actinide fluoride mixtures that are of immediate interest to MSR developers. Specifically, the mixtures NaF-UF 4 (78 - 22 mol%) and NaF-KF-UF 4 (57-16.04-26.91 mol%) have been studied—NaF-UF 4 for thermal conductivity and viscosity and NaF-KF-UF 4 for viscosity. Thermal conductivity measurements have been conducted with a variable gap apparatus, whereas viscosity has been measured with a rolling ball viscometer. Methodological and calibration details are provided for both measurement processes, along with measurement system updates that have enabled easier manufacturing of components and fewer challenges associated with conducting the measurements themselves. The resultant data collected for NaF-UF 4 (78–22 mol%) and NaF-KF-UF 4 (57-16.04-26.91 mol%) have been compared with relevant mixture data within the thermophysical arm of the MSTDB (MSTDB-TP).

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Relationship of the Molecular Structure and Transport Properties of Imide-Based Lithium Salts of “Acetonitrile/Water-in-Salt” Electrolytes

“Water-in-salt” (WIS) electrolytes exhibit excellent safety and electrochemical performance. However, they possess high concentrations, relatively low diffusion coefficient, and high viscosity. “Acetonitrile/water in salt” (AWIS) electrolytes can overcome the disadvantages of WIS electrolytes. Under relatively low concentrations, AWIS electrolytes show good electrochemical performance comparable to WIS electrolytes and low conductivity. Herein, we investigate the relationship between the solvation structures and the transport properties using small-angle X-ray scattering and molecular dynamics simulation. We observed two solvation behaviors of AWIS: anions dissolved in acetonitrile forming small acetonitrile/anion clusters and additional water further dissolving the small acetonitrile/anion clusters. The introduction of acetonitrile weakens the water–solute interaction and enhances the cation–anion interaction, which results in an enhanced dynamical slowdown as the concentration increases. In conclusion, this work provides molecular-level understanding of the connection between two-stage solvation structures and transport properties for imide-based lithium salt solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Tuning the Charge Transport Property and Photocatalytic Activity of Anthracene-Based 1D π–d Conjugated Coordination Polymers by Interlayer Stacking

One-dimensional (1D) π–d-conjugated coordination polymers (CCPs) with charge delocalization have attracted significant attention due to their potential application in energy conversion and storage. However, the fundamental understanding of the correlation of their structural parameters with photophysical and photocatalytic properties remains underexplored. Herein, we report three novel Cu-node anthracene-based 1D π–d CCPs with systematic variation of steric groups (Ph > Me > H) at the 9 and 10 position of anthracene (denoted as An Ph , An Me , and An H ), which is aimed at altering the stacking of the polymer chains and its impact on the inter-chain charge transport property. Here, by using the combination of steady-state X-ray absorption spectroscopy, optical transient absorption spectroscopy, X-ray transient absorption spectroscopy, and electrochemical impedance spectroscopy, we show that the linear ligands (An Ph , An Me , and An H ) with different degrees of steric groups (Ph > Me > H) introduced at the 9 and 10 position of anthracene can alter the stacking of the polymer chains and thus impact their crystallinity, charge separation, and charge transport property, which in turn impacts their photocatalytic performance for hydrogen evolution reaction.

1-D-polymer↗
DOE OSTI2024

Interfacial charge transfer and its impact on transport properties of LaNiO 3 /LaFeO 3 superlattices

Charge transfer or redistribution at oxide heterointerfaces is a critical phenomenon, often leading to remarkable properties such as two-dimensional electron gas and interfacial ferromagnetism. Despite studies on LaNiO 3 /LaFeO 3 superlattices and heterostructures, the direction and magnitude of the charge transfer remain debated, with some suggesting no charge transfer due to the high stability of Fe 3+ (3d 5 ). Here, we synthesized a series of epitaxial LaNiO 3 /LaFeO 3 superlattices and demonstrated partial (up to ~0.5 e - /interface unit cell) charge transfer from Fe to Ni near the interface, supported by density functional theory simulations and spectroscopic evidence of changes in Ni and Fe oxidation states. The electron transfer from LaFeO 3 to LaNiO 3 and the subsequent rearrangement of the Fe 3d band create an unexpected metallic ground state within the LaFeO 3 layer, strongly influencing the in-plane transport properties across the superlattice. Moreover, we establish a direct correlation between interfacial charge transfer and in-plane electrical transport properties, providing insights for designing functional oxide heterostructures with emerging properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1975

Computer program for calculating thermodynamic and transport properties of fluids

Computer code has been developed to provide thermodynamic and transport properties of liquid argon, carbon dioxide, carbon monoxide, fluorine, helium, methane, neon, nitrogen, oxygen, and parahydrogen. Equation of state and transport coefficients are updated and other fluids added as new material becomes available.

Hendricks, R. C.↗
NASA NTRS1988

Transport properties for the oxygen system - O2, O, O(+), and e

The transport properties of the oxygen system, O2, O, O(+), and the electron, e, are calculated and their applications are discussed. The possible two-body interactions in the oxygen system are examined and the exponential repulsive potential is used to determine collision integrals for these interactions. Values are presented for the viscosity of the pure gases, the self-diffusion coefficient of the pure gases at 1 atm pressure, the translational thermal conductivity of the pure gases, and the internal thermal conductivity of O2.

Biolsi, Louis↗
NASA NTRS2001

Radiation Transport Properties of Potential In Situ-Developed Regolith-Epoxy Materials for Martian Habitats

We will evaluate the radiation transport properties of epoxy-martian regolith composites. Such composites, which would use both in situ materials and chemicals fabricated from elements found in the martian atmosphere, are candidates for use in habitats on Mars. The principal objective is to evaluate the transmission properties of these materials with respect to the protons and heavy charged particles in the galactic cosmic rays which bombard the martian surface. The secondary objective is to evaluate fabrication methods which could lead to technologies for in situ fabrication. The composites will be prepared by NASA Langley Research Center using simulated martian regolith. Initial evaluation of the radiation shielding properties will be made using transport models developed at NASA-LaRC and the results of these calculations will be used to select the composites with the most favorable radiation transmission properties. These candidates will then be empirically evaluated at particle accelerators which produce beams of protons and heavy charged particles comparable in energy to the radiation at the surface of Mars.

Miller, J.↗
DOE OSTI2020

Magnetic and transport properties of amorphous, B 2 and L 2 1 Co 2 MnGa thin films

We have studied the magnetic and transport properties of Co 2 MnGa (CMG) thin films grown on MgO(100) substrates in terms of their chemical evolution from amorphous to ordered L 2 1 phases at the substrate temperature T s during the thin film deposition. Interestingly, the chemical order and magnetic properties sharply change depending on T s . The CMG film deposited at T s = 550 °C exhibits the L 2 1 -ordered structure and the magnetization of 3.5 μ B /f.u., while the CMG film deposited at T s = 300 °C shows a B 2-ordered structure and a relatively lower magnetization of 3 μ B /f.u., possibly due to the Mn–Mn antiferromagnetic interactions. A metallic behavior of the electrical resistivity appeared in the CMG film deposited at T s = 550 °C, whereas the semiconducting behavior appeared in the CMG films deposited at 300 °C and room temperature. Moreover, we found that the absolute value of α = d(Δ ρ )/d( T 1/2 ) in the low-temperature range below about 20 K is a measure to evaluate the degree of the chemical disorder. In a Hall effect measurement, the L 2 1 -ordered CMG film obtained at T s = 550 °C shows a sizable anomalous Hall resistivity of 15 µ Ω cm. This study unveils the relation between T s and atomic ordering, providing a new pathway for optimizing the chemical order.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Synthesis, Structures, and Transport Properties of Quaternary Ba–Ag– Tr –As Materials ( Tr = Ga, In)

The synthesis, structures, and properties of two quaternary barium–arsenide materials are presented. The first, Ba 4 Ag 2.3 In 1.7 As 8 , is a novel material with the monoclinic unit cell ( P 2 1 / m space group). The layered crystal structure of Ba 4 Ag 2.3 In 1.7 As 8 may be considered a lower‐symmetry, distorted analog of the LaCuSb 2 structure. The structure features a rare As fragment, cis‐trans As chains along the [010] direction. Large crystals of Ba 4 Ag 2.3 In 1.7 As 8 can be grown from Bi flux and are used for subsequent transport property measurements. Electrical resistivity and heat capacity properties are reported, establishing Ba 4 Ag 2.3 In 1.7 As 8 as a metallic phase. The second material, Ba 4 AgGa 5 As 8 , is a 3D material that crystallizes in the orthorhombic unit cell (noncentrosymmetric and polar Iba 2 space group). Expanding upon its original discovery, the optimized synthetic profile for single‐phase polycrystalline samples as well as transport properties relevant to thermoelectric applications are presented. Ba 4 AgGa 5 As 8 exhibits a high Seebeck coefficient of 290 μV K −1 at room temperature, indicative of lower carrier concentrations typical for nonmetallic phases. Electrical resistivity measurements also affirm conventional semiconducting behavior for Ba 4 AgGa 5 As 8 .

Kyveryga, Victoria [Department of Chemistry Iowa S↗
NASA NTRS1983

Transport properties of ground state nitrogen atoms

In view of the dependence of the transport properties of dilute monatomic gases on the two-body, atom-atom interaction potential, any one of four potential energy curves corresponding to the N2 molecule can be followed when two ground state N atoms interact. Transport collision integrals for the 1Sigma(+)g and 3Sigma(+)u states have been calculated by representing their potentials with the Hulburt-Hirschfelder (1941, 1961) potential. The 5Sigma(+)g state has a large local maximum requiring changes in a previously used computational procedure, and its potential has also been represented by a Hulburt-Hirschfelder potential. Collision integrals for the 7Sigma(+)u state have been obtained through the direct use of a recently proposed theoretical potential for this state. The collision integrals are compared with results gathered from previous studies.

Rainwater, J. C.↗
NASA NTRS1993

Computing Thermodynamic And Transport Properties

CET89 calculates compositions in chemical equilibrium and properties of mixtures of any chemical system for which thermodynamic data available. Provides following options: obtains chemical-equilibrium compositions and corresponding thermodynamic mixture properties for assigned thermodynamic states; calculates dilute-gas transport properties of complex chemical mixtures; obtains Chapman-Jouguet detonation properties for gaseous mixtures; calculates properties of incident and reflected shocks in terms of assigned velocities; and calculates theoretical performance of rocket for both equilibrium and frozen compositions during expansion. Rocket performance based on optional models of finite or infinite area combustor.

Mcbride, B.↗
DOE OSTI2020

α Irradiation Response on the Electronic Transport Properties of p -B 12 P 2

B 12 P 2 , a wide bandgap semiconductor, has been previously reported to self-heal from high-energy electron bombardment as determined from transmission electron microscopy. However, the effect of irradiation on the electronic transport properties of B 12 P 2 has not been studied. We report electrical transport measurements on B 12 P 2 after α irradiation. The temperature-dependent Hall effect was measured on p-type B 12 P 2 after successive α irradiation from 210 Po over a fluence range of 1 × 10 11 –1 × 10 13 α/cm 2 to test for self-healing of B 12 P 2 to α bombardment. Prior to irradiation, B 12 P 2 displayed electrical transport characteristics of both hopping and impurity/defect band conduction due to background impurities and growth-induced defects. Fluences of 5 × 10 12 α/cm 2 or greater caused a decrease in the hole mobility and an increase in defect band conduction, suggesting defect accumulation in B 12 P 2 .

36 MATERIALS SCIENCE↗