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Results for “insulation resistance”

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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Colloidal superionic conductors

Nanoparticles with highly asymmetric sizes and charges that self-assemble into crystals via electrostatics may exhibit behaviors reminiscent of those of metals or superionic materials. Here, we use coarse-grained molecular simulations with underdamped Langevin dynamics to explore how a binary charged colloidal crystal reacts to an external electric field. As the field strength increases, we find transitions from insulator (ionic state), to superionic (conductive state), to laning, to complete melting (liquid state). In the superionic state, the resistivity decreases with increasing temperature, which is contrary to metals, yet the increment decreases as the electric field becomes stronger. Additionally, we verify that the dissipation of the system and the fluctuation of charge currents obey recently developed thermodynamic uncertainty relation. Our results describe charge transport mechanisms in colloidal superionic conductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Resistive heating in an electrified domain with a spherical inclusion: an ALEGRA verification study

A verification study is conducted for the ALEGRA software, using the problem of an electrified medium with a spherical inclusion, paying special attention to resistive heating. We do so by extending an existing analytic solution for this problem to include both conducting and insulating inclusions, and we examine the effects of mesh resolution and mesh topology, considering both body-fitted and rectangular meshes containing mixed cells. We present observed rates of convergence with respect to mesh refinement for four electromagnetic quantities: electric potential, electric field, current density and Joule power.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Fluoropolymer Aging Phenomena

This project aims to investigate structural and morphological changes in fluoropolymers induced by both processing and aging phenomena such as heat, time, and irradiation. Fluoropolymers are an important class of thermoplastics that are broadly used in industry as o-rings and seals when chemical resistance and thermal performance are important. They are also often used in thin film geometries as binders in batteries, insulation layers, water barriers, and anti-fouling coatings. For all of these applications, mechanical integrity and aging are important aspects of their use. Changes in the crystalline morphology are known to impact the mechanical properties of the polymer and can lead to failure. The broad goals of this project are to correlate compositional changes, morphological changes, and mechanical changes. report focuses on the morphological changes that are correlated with nuclear magnetic resonance (NMR), calorimetry and mechanical testing. We plan to compare structure and morphology measurements across complementary bulk and surface techniques. We use in situ atomic force microscopy (AFM) to measure domain shape and crystallization kinetics; in situ NMR to measure crystalline composition; and differential scanning calorimetry (DSC) to measure melting temperatures.

36 MATERIALS SCIENCE↗
NASA NTRS1983

New method of determining the onset of ring cracking

A technique is developed for the detection of the onset of circumferential ring cracks in a flat brittle piece of an electrically insulating material. Thin metal films were deposited on both the insulating indentor (diamond) and the insulating brittle flat. The initiation of a ring crack was signified by a step in the monitored electrical contact resistance between the indentor and flat metal films versus the applied force. It was determined by tests performed on polished glass slides using diamond indentors that this technique is both sensitive and reproducible. The onset of crack formation as observed by optical means was found to occur at the same time as the step in the contact resistance when both experiments were carried out simultaneously.

Grzybowski, T. A.↗
NASA NTRS1987

Coaxial cable connector

A coaxial cable connector is provided, which resists radio frequency breakdown in coaxial cables used in the vacuum of outer space. The connector body surrounds an insulator which includes an easily compressible elastomeric portion. An insulated coaxial cable is prepared so that its insulation projects beyond the outer conductor and compresses the elastomeric portion of the connector insulator.

Caro, Edward R.↗
NASA NTRS1990

Solid-state reprogrammable analog resistive devices for electronic neural networks

The fabrication and performance of WO3-based, solid-state, three-terminal device configurations as programmable analog memory elements are reported. These transistorlike device structures exhibit good resistance progammability with a remarkable resolution of a few percent of the resistive strength over a four orders of magnitude dynamic range. The most critical component of these devices is an insulating layer between the active WO3 and the cation donor layer. The progamming characteristics and operation mechanisms of the device are described, and probable reaction mechanisms critical to the device stability are discussed.

Ramesham, R.↗
NASA NTRS1984

Thermal Insulation

Commercially known as Solimide, Temptronics, Inc.'s thermal insulation has application in such vehicles as aircraft, spacecraft and surface transportation systems (i.e. rapid transit cars, trains, buses, and ships) as acoustical treatment for door, wall, and ceiling panels, as a means of reducing vibrations, and as thermal insulation (also useful in industrial equipment). Product originated from research conducted by Johnson Space Center on advanced flame-resistant materials for minimizing fire hazard in the Shuttle and other flight vehicles.

Source record↗
NASA NTRS2003

Eroding Potentiometers

Eroding potentiometers have been devised for measuring the time-dependent positions of char fronts advancing through layers of insulating material subject to intense heating from one side. In the original application, the material layers of interest are thermal insulators in rocket motors and the heat comes from firing of the motors, but the principle of operation is equally applicable to other insulating materials subject to intense heating (e.g., ablative fire-retardant materials). Measuring the thickness decrement of propellant (in hybrid motors in particular) is another possible application of this transducer. Telemetry informs mission control of the propellant left after each burn. An eroding potentiometer could be characterized, more precisely, as an eroding two-wire resistor. It includes a twisted pair of thin, insulated wires oriented along the thickness of, and embedded in, the layer of thermal-insulation material to be tested (see figure). The electrical insulation material on the wires should be one for which the charring temperature is about the same as (or perhaps slightly less than) that of the thermal- insulation material to be tested. In the original rocket-motor application, the wires have a diameter of 0.003 in. (.0.08 mm), are made of manganin, and are coated with polyimide for electrical insulation. Outside the thermal insulation on the cold side, the wire leads are connected to a Wheatstone bridge circuit for measurement of electrical resistance change.

Eggett, Mark↗
DOE OSTI2023

Probing FeSi, a d -electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves

Recently, evidence for a conducting surface state (CSS) below 19 K was reported for the correlated d -electron small gap semiconductor FeSi. In the work reported herein, the CSS and the bulk phase of FeSi were probed via electrical resistivity ρ measurements as a function of temperature T , magnetic field B to 60 T, and pressure P to 7.6 GPa, and by means of a magnetic field-modulated microwave spectroscopy (MFMMS) technique. The properties of FeSi were also compared with those of the Kondo insulator SmB 6 to address the question of whether FeSi is a d -electron analogue of an f -electron Kondo insulator and, in addition, a “topological Kondo insulator” (TKI). The overall behavior of the magnetoresistance of FeSi at temperatures above and below the onset temperature T S = 19 K of the CSS is similar to that of SmB 6 . The two energy gaps, inferred from the ρ( T ) data in the semiconducting regime, increase with pressure up to about 7 GPa, followed by a drop which coincides with a sharp suppression of T S . Several studies of ρ( T ) under pressure on SmB 6 reveal behavior similar to that of FeSi in which the two energy gaps vanish at a critical pressure near the pressure at which T S vanishes, although the energy gaps in SmB 6 initially decrease with pressure, whereas in FeSi they increase with pressure. The MFMMS measurements showed a sharp feature at T S ≈ 19 K for FeSi, which could be due to ferromagnetic ordering of the CSS. However, no such feature was observed at T S ≈ 4.5 K for SmB 6 .

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Temperature dependence of the energy band gap in ZrTe 5 : Implications for the topological phase

Using Landau level spectroscopy, we determine the temperature dependence of the energy band gap in zirconium pentatelluride (ZrTe 5 ). We find that the band gap reaches E g = (5±1) meV at low temperatures and increases monotonously when the temperature is raised. So this implies that ZrTe 5 is a weak topological insulator, with non-inverted ordering of electronic bands in the center of the Brillouin zone. Our magneto-transport experiments performed in parallel show that the resistivity anomaly in ZrTe 5 is not connected with the temperature dependence of the band gap.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Electronic and magnetic properties of the RuX3 (X = Cl, Br, I) family: two siblings—and a cousin?

Abstract Motivated by reports of metallic behavior in the recently synthesized RuI 3 , in contrast to the Mott-insulating nature of the actively discussed α -RuCl 3 , as well as RuBr 3 , we present a detailed comparative analysis of the electronic and magnetic properties of this family of trihalides. Using a combination of first-principles calculations and effective-model considerations, we conclude that RuI 3 , similarly to the other two members, is most probably on the verge of a Mott insulator, but with much smaller magnetic moments and strong magnetic frustration. We predict the ideal pristine crystal of RuI 3 to have a nearly vanishing conventional nearest-neighbor Heisenberg interaction and to be a quantum spin liquid candidate of a possibly different kind than the Kitaev spin liquid. In order to understand the apparent contradiction to the reported resistivity ρ , we analyze the experimental evidence for all three compounds and propose a scenario for the observed metallicity in existing samples of RuI 3 . Furthermore, for the Mott insulator RuBr 3, we obtain a magnetic Hamiltonian of a similar form to that in the much-discussed α -RuCl 3 and show that this Hamiltonian is in agreement with experimental evidence in RuBr 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hydrophobic, Thermal-shock Resistant Lightweight Cement Composites in Hybrid Thermal Energy-Storage Geothermal Well System

Under the DOE EERE Geothermal Technology Office (GTO)-funded project in FY 2019-2022, Brookhaven National Laboratory (BNL) aimed to develop hydrophobic thermal-shock resistant lightweight well cement composites suitable for temporarily storing a curtailed hot working fluid incurred from excess geothermal-, solar-, and wind-generated energies in underground reservoirs thermal energy storage sites. This storage energy systems are designed to provide energy during the periods between energy-harvesting and -requiring periods. One key factor to the success of this project was hydrophobicity of cement composites. The hydrophobic composites not only upgrade thermal insulating properties of water-saturated composites for minimizing heat loss in upper well surface regions, but also provide improved mechanical properties related to thermal-shock resistance and the protection of carbon steel (CS) casing against corrosion.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

Dynamics of voltage-driven oscillating insulator-metal transitions

Recent experiments demonstrated emerging alternating insulator and metal phases in Mott insulators actuated by a direct bias voltage, leading to oscillating voltage outputs with characteristic frequencies. Here, we develop a physics-based nonequilibrium model to describe the dynamics of oscillating insulator-metal phase transitions and experimentally validate it using a VO 2 device as a prototype. The oscillation frequency is shown to scale monotonically with the bias voltage and series resistance and terminate abruptly at lower and upper device-dependent limits, which are dictated by the nonequilibrium carrier dynamics. Here, we derive an approximate analytical expression for the dependence of the frequency on the device operating parameters, which yields a fundamental limit to the frequency and may be utilized to provide guidance to potential applications of insulator-metal transition materials as building blocks of brain-inspired non-von Neumann computers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Electrically-driven IMT and volatile memristor behavior in NdNiO 3 films

Abstract Transition metal oxides with insulator-metal transitions (IMTs) are uniquely suited for volatile memristor devices that mimic the spiking of biological neurons. Unlike most non-volatile memristors, which often operate via ion migration into filaments, volatile devices utilize a reversible phase change that returns to a ground state in the absence of applied stimulus. In these devices, Joule heating triggers the IMT and changes the bulk resistivity rather than influencing conduction through defects, as in previous studies. This volatile resistive switching behavior has previous been leveraged in niobium and vanadium oxides, but not in rare-earth nickelates, despite their tunable transition temperatures. This study demonstrates an electrically driven IMT in the prototypical rare-earth nickelate, NdNiO 3 , in large area devices. While previous work examining the electrically-driven IMT in NdNiO 3 suggests defect-dominated conduction, this study shows clear s-type negative differential resistance (NDR) consistent with temperature-dependent resistivity measurements. The NDR peak-to-valley voltage scales linearly with temperature as expected for conductivity pathways dominated by bulk IMT behavior. Unlike other transition metal oxides, which are modeled using the insulator-metal phase fraction as the internal state variable, a thermoelectric model with temperature as the internal state variable is found to more accurately describe the current–voltage characteristic of NdNiO 3 volatile memristors. Overall, we report the synthesis, fabrication, and characterization of NdNiO 3 volatile memristors with resistivity dominated by bulk-like IMT behavior which is scalable and not dependent upon oxygen vacancy migration or defect mediated conduction pathways.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Optimization of well design and CO 2 injection strategy for risk reduction in Class VI geological carbon sequestration wells

The safety and durability of Class VI wells are critical for geological carbon sequestration (GCS). However, current GCS operations face unique challenges: unlike traditional Class II wells, Class VI CO 2 injection wells operate at rates up to 100 times higher, dramatically increasing the risk of wellbore leakage and structural compromise due to severe temperature drops and associated mechanical stresses. Despite existing guidelines on material selection, there remains a substantial gap in understanding how rapid CO 2 injection rates, low surface temperatures, and variable reservoir conditions interact to threaten long-term well integrity. This study presents a comprehensive, original workflow integrating advanced analytical and numerical models for both well flow and well integrity analysis. By systematically simulating a wide range of field-relevant scenarios—including variations in injection rate, CO 2 temperature, and reservoir pressure—this work provides the first cross-validated assessment of cooling effects on wellbore. The results reveal that extreme temperature drops, up to 60 °C, can occur under high injection rates, particularly in depleted reservoirs, significantly increasing the risk of cement failure. Building on these insights, the study proposes innovative, practical well design and operational strategies, including ductile cement formulations, pre-stressing techniques, advanced insulation coatings, and proactive management of injection rates. The safety of Class VI well extends beyond simply using CO 2 resistant materials. Cement materials should possess optimal thermo-hydraulic-mechanical-chemical properties for effective performance. This work provides a scientific basis for optimizing Class VI well designs, with direct benefits for minimizing environmental risk, lowering operational costs, and enhancing the long-term reliability of GCS.

25 ENERGY STORAGE↗
DOE OSTI2023

Evidence for Bootstrap Percolation Dynamics in a Photoinduced Phase Transition

Upon intense femtosecond photo-excitation, a many-body system can undergo a phase transition through a non-equilibrium route, but understanding these pathways remains an outstanding challenge. Here, we use time-resolved second harmonic generation to investigate a photo-induced phase transition in Ca 3 Ru 2 O 7 and show that mesoscale inhomogeneity profoundly influences the transition dynamics. We observe a marked slowing down of the characteristic time τ that quantifies the transition between two structures. τ evolves non-monotonically as a function of photo-excitation fluence, rising from below 200 fs to ~1.4 ps, then falling again to below 200 fs. To account for the observed behavior, we perform a bootstrap percolation simulation that demonstrates how local structural interactions govern the transition kinetics. Finally, our work highlights the importance of percolating mesoscale inhomogeneity in the dynamics of photo-induced phase transitions and provides a model that may be useful for understanding such transitions more broadly.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Enhancing Thermal Transport in Polymeric Composites Via Engineered Noncovalent Filler–Polymer Interactions

Understanding thermal transport mechanisms in polymeric composites allows us to expand the boundaries of thermal conductivity in them, either increasing it for more efficient heat dissipation or decreasing it for better thermal insulation. But, these mechanisms are not fully understood. Systematic experimental investigations remain limited. Practical strategies to tune the interfacial thermal resistance (ITR) between fillers and polymers and the thermal conductivity of composites remain elusive. Here, we studied the thermal transport in representative polymer composites, using polyethylene (PE) or polyaniline (PANI) as matrices and graphite as fillers. PANI, with aromatic rings in its backbone, interacts with graphite through strong noncovalent π–π stacking interactions, whereas PE lacks such interactions. We can then quantify how π–π stacking interactions between graphite and polymers enhance thermal transport in composites. PE/graphite and PANI/graphite composites with the same 1.5% filler volume fractions show a ∼22.82% and ∼34.85% enhancement in thermal conductivity compared to pure polymers, respectively. Calculated ITRs in PE/graphite and PANI/graphite are ~6 x 10 -8 m 2 KW -1 and ~1 x 10 -8 m 2 KW -1 , respectively, highlighting how π–π stacking interactions reduce ITR. Molecular dynamics (MD) simulations suggest that π–π stacking interactions between PANI chains and graphite surfaces enhance alignment of PANI's aromatic rings with graphite surfaces. This allows more carbon atoms from PANI chains to interact with graphite surfaces at a shorter distance compared to PE chains. Finally, our work indicates that tuning the π–π stacking interactions between polymers and fillers is an effective approach to reduce the ITR and enhance the thermal conductivity of composites.

atoms↗