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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Conductive Tether Coating for Electrodynamic Tethers

The Propulsive Small Expendable Deployer System (ProSEDS), which is an on-orbit demonstration of the propulsion capabilities of electrodynamic tethers in space, is a secondary payload on a Delta 11 unmanned expendable booster. The ProSEDS tether consists of a 5 km bare electrodynamic tether and a 1 0-km non-conductive leader tether. Near the Delta 11, 160 m of the conductive tether is insulated to prevent plasma electron collection from the plasma contactor and for other science requirements. The remainder of the 5-km conductive tether is coated with a new conductive coating to collect plasma electrons. A bare metal tether easily collects electrons from the plasma, but thermal concerns preclude this design. A highly emissive conductive polymer developed by Triton Systems, Inc. has been optimized for both conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven individually coated strands of 28 AWG aluminum wire, coated with an atomic oxygen-resistant conductive polymer composed of a mixture of COR (Colorless Oxygen Resistant) and polyanaline (PANI) known as C-COR (Conductive-Colorless Oxygen Resistant). The conductive-coated wire strands are cold-welded to individually coated strands of the insulated tether. The insulated tether is coated with 1 mil of polyimide and an atomic oxygen resistant polymer TOR-BP. The insulated tether must stand off the entire voltage of the tether (1 200 V) at various times during the mission. All seven wires are twisted around a Kevlar-29 core using the Hi-wire design. Extensive testing has been performed at the Marshall Space Flight Center to qualify both the conductive coating and insulating coating for use on the ProSEDS tether. The conductive coating has been exposed to a plasma to verify the coatings ability to collect electrons from the space plasma from 0 to 1500 V, and to verify the coatings ability to collect electrons after atomic oxygen exposure. The insulated coating has been tested to verify its dielectric strength both in a vacuum and air. Thermal optical properties on both coatings have been measured before and after atomic oxygen testing. The results of these tests will be presented.

Jason A Vaughn↗
NASA NTRS1975

Evaluation of the present theoretical basis for determination of planetary surface properties by earth-based radar

Spaceflight programs such as the planned Viking landing on Mars require the determination of planetary surface slopes and surface dielectric constants by earth-based methods. Heavy reliance is often placed on radar backscattering data for estimation of these surface properties. An assessment is presented of the basic theory by which the raw radar data are interpreted, and it is shown that serious difficulties and internal inconsistencies are present in the available theoretical formulas. The discussion brings into question the reliability of the presently available results for these surface properties as obtained by earth-based radar methods.

Staton, L. D.↗
NASA NTRS1974

The nature of the subsurface of Mercury from microwave observations at several wavelengths

Interferometric observations of Mercury at 3.71 cm are used to determine the dielectric constant of the subsurface material at a depth of 50 cm to be 2.4 plus or minus 0.3. The surface emissivity in the radio range is determined by the value of the dielectric constant which is thus necessary in order to interpret the thermal properties of the regolith. New integrated-disk data at 6- and 18-cm wavelengths are found to be consistent with a regolith of particulate geological material in which radiative transfer of heat is important. The results are very similar to the lunar case where regolith density, dielectric constant, and loss tangent are observed to increase smoothly with depth in the subsurface.

Cuzzi, J. N.↗
NASA NTRS1989

The tapered slot antenna - A new integrated element for millimeter-wave applications

Tapered slot antennas (TSAs) with a number of potential applications as single elements and focal-plane arrays are discussed. TSAs are fabricated with photolithographic techniques and integrated in either hybrid or MMIC circuits with receiver or transmitter components. They offer considerably narrower beams than other integrated antenna elements and have high aperture efficiency and packing density as array elements. Both the circuit and radiation properties of TSAs are reviewed. Topics covered include: antenna beamwidth, directivity, and gain of single-element TSAs; their beam shape and the effect of different taper shapes; and the input impedance and the effects of using thick dielectrics. These characteristics are also given for TSA arrays, as are the circuit properties of the array elements. Different array structures and their applications are also described.

Yngvesson, K. Sigfrid↗
DOE OSTI2020

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

Capacitance-based techniques were previously used to measure the electrical properties of halide perovskite solar cells (PSCs) such as defect activation energy and density, carrier concentration, and dielectric constant, which provide key information for evaluating the device performance. Herein, we show that capacitance-based techniques cannot be used to reliably analyze the properties of defects in the perovskite layer or at its interface, since the high-frequency capacitance signature is due to the response of charge carriers in the hole-transport layer (HTL). For HTL-free PSCs, the high-frequency capacitance can be considered as the geometric capacitance for analyzing the dielectric constant of the perovskite layer, since there is no trapping and de-trapping of charge carriers in the perovskite layer. We also find that the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer, but the overlapping effects with charge transport materials must be avoided.

14 SOLAR ENERGY↗
DOE OSTI2023

Discovery of Nanoscale Electric Field‐Induced Phase Transitions in ZrO 2

Abstract The emergence of ferroelectric and antiferroelectric properties in the semiconductor industry's most prominent high‐k dielectrics, HfO 2 and ZrO 2 , is leading to technology developments unanticipated a decade ago. Yet the failure to clearly distinguish ferroelectric from antiferroelectric behavior is impeding progress. Band‐excitation piezoresponse force microscopy and molecular dynamics are used to elucidate the nanoscale electric field‐induced phase transitions present in ZrO 2 ‐based antiferroelectrics. Antiferroelectric ZrO 2 is clearly distinguished from a closely resembling pinched La‐doped HfO 2 ferroelectric. Crystalline grains in the range of 3 – 20 nm are imaged independently undergoing reversible electric field induced phase transitions. The electrically accessible nanoscale phase transitions discovered in this study open up an unprecedented paradigm for the development of new nanoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Extraction of intrinsic contact resistance in organic thin-film transistors with single channel length and high capacitance density

Accurate characterization of the intrinsic contact resistance is important for the optimization of organic thin-film transistors (OTFTs), especially in devices with high gate capacitance density. This study reports on a method for the extraction of the intrinsic, or gate-voltage independent, contact resistance from OTFTs. In contrast to the transfer length method (TLM), this method can be applied to devices with a single geometry. The method is an extension of the previously reported Y-function method and combines the model proposed by S. Luan et al. to analyze the effect of the gate voltage on the contact resistance. Here, this method is first applied to OTFTs with a bottom-gate top-contact geometry having varying gate capacitance density values. The intrinsic contact resistance is found to decrease with increased gate capacitance density with values ranging between 4 kΩcm and under 1 kΩcm when the gate capacitance is changed from 36.6 nF/cm 2 to 231.7 nF/cm 2 , respectively. These values are in good agreement with those obtained using TLM experiments. The new method is also shown to be applicable to OTFTs with top-gate bottom contact geometry.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing electromagnetic nonreciprocity with quantum geometry of photonic states

Reciprocal and nonreciprocal effects in dielectric and magnetic materials provide crucial information about the microscopic properties of electrons. However, experimentally distinguishing the two has proven to be challenging, especially when the associated effects are extremely small. To this end, we propose a contactless detection using a cross-cavity device where a material of interest is placed at its center. We show that the optical properties of the material, such as Kerr and Faraday rotation, or birefringence, manifest in the coupling between the cavity's electromagnetic modes and in the shift of their resonant frequencies. By calculating the dynamics of a geometrical photonic state, we formulate a measurement protocol based on the quantum metric and quantum process tomography that isolates the individual components of the material's complex refractive index and minimizes the quantum mechanical Cramér-Rao bound on the variance of the associated parameter estimation. Our approach is expected to be applicable across a broad spectrum of experimental platforms including Fock states in optical cavities, or coherent states in microwave and THz resonators. Published by the American Physical Society 2025

Petrides, Ioannis (ORCID:0000000174842444)↗
NASA NTRS1988

Environment of Mars, 1988

A compilation of scientific knowledge about the planet Mars is provided. Information is divided into three categories: atmospheric data, surface data, and astrodynamic data. The discussion of atmospheric data includes the presentation of nine different models of the Mars atmosphere. Also discussed are Martian atmospheric constituents, winds, clouds, and solar irradiance. The great dust storms of Mars are presented. The section on Mars surface data provides an in-depth examination of the physical and chemical properties observed at the two Viking landing sites. Bulk densities, dielectric constants, and thermal inertias across the planet are then described and related back to those specific features found at the Viking landing sites. The astrodynamic materials provide the astronomical constants, time scales, and reference coordinate frames necessary to perform flightpath analysis, navigation design, and science observation design.

Kaplan, David I.↗
NASA NTRS1996

Polyimides That Contain Pendent Siloxane Groups

Polyimides containing pendent siloxane groups (PISOXs) synthesized from polyimides containing hydroxy groups (PIOHs) according to either of two alternative approaches. Addition of pendent siloxane groups to polyimide decreases dielectric constant, and decreases absorption of moisture: these changes in properties advantageous in some electronic applications. Also enhance resistance to atomic oxygen in that they undergo slight degradation to form thin protective silicon oxide coats when exposed to atomic oxygen.

Connell, John W.↗
NASA NTRS2009

Extended Life PZT Stack Test Fixture

Piezoelectric stacks are being sought to be used as actuators for precision positioning and deployment of mechanisms in future planetary missions. Beside the requirement for very high operation reliability, these actuators are required for operation at space environments that are considered harsh compared to normal terrestrial conditions.These environmental conditions include low and high temperatures and vacuum or high pressure. Additionally, the stacks are subjected to high stress and in some applications need to operate with a very long lifetime durability.Many of these requirements are beyond the current industry design margins for nominal terrestrial applications. In order to investigate some of the properties that will indicate the durability of such actuators and their limitations we have developed a new type of test fixture that can be easily integrated in various test chambers for simulating environmental conditions, can provide access for multiple measurements while being exposed to adjustable stress levels. We designed and built two test fixtures and these fixtures were made to be adjustable for testing stacks with different dimensions and can be easily used in small or large numbers. The properties that were measured using these fixtures include impedance, capacitance, dielectric loss factor, leakage current, displacement, breakdown voltage, and lifetime performance. The fixtures characteristics and the test capabilities are presented in this paper.

test fixtures↗
NASA NTRS1992

Electrical properties of teflon and ceramic capacitors at high temperatures

Space power systems and components are often required to operate efficiently and reliably in harsh environments where stresses, such as high temperature, are encountered. These systems must, therefore, withstand exposure to high temperature while still providing good electrical and other functional properties. Experiments were carried out to evaluate Teflon and ceramic capacitors for potential use in high temperature applications. The capacitors were characterized in terms of their capacitance and dielectric loss as a function of temperature, up to 200 C. At a given temperature, these properties were obtained in a frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed in a temperature range from 25 to 200 C. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors studied for high temperature applications.

Hammoud, A. N.↗
NASA NTRS2005

Water as a matrix for life

Life is based on non-covalent interactions. They might be either specific (enzyme-substrate interactions, selective ion transport) or nonspecific (lipid-lipid and lipid-protein interactions needed for membrane integrity, fusion and division). Their strength needs to be properly tuned, and this is mediated by the solvent. If interactions are too weak, there might be undesired response to natural fluctuations of physical and chemical parameters. If they are too strong it could impede kinetics and energetics of cellular processes. Thus, the solvent must allow for balancing these interactions. Physical and chemical properties of solvent provide strong constraints for life. Water exhibits a remarkable trait that it promotes both solvophobic and solvophilic interactions. Solvophobic interactions; related to high dielectric constant of the solvent) are necessary for self-organization of matter whereas solvophilic interactions are needed to ensure solubility of polar species. Water offers a large temperature domain of stable liquid and the characteristics hydrophobic effects are a consequence of the temperature in sensitivity of essential properties of its liquid state. Water, however, is not the only liquid with these favorable properties. I will compare in detail properties of water and other pure liquids or their mixtures that have a high dielectric constant and simultaneously support self-organization. I will also discuss properties of water that are unfavorable to life (e.g. its chemical activity against polymerization reactions) and close with summarizing what are alternatives to water as a matrix of life in space.

Pohorille, Andrew↗
DOE OSTI2021

Probing phonon softening in ferroelectrics by scanning probe microwave spectroscopy

Microwave measurements have recently been successfully applied to measure ferroelectric materials on the nanoscale, including detection of polarization switching and ferroelectric domain walls. In this study we discuss the question of whether scanning probe microscopy operating at microwave frequency can identify the changes associated with the soft phonon dynamics in a ferroic. The analytical expressions for the electric potential, complex impedance, and dielectric losses are derived and analyzed, since these physical quantities are linked to experimentally measurable properties of the ferroic. As a ferroic we consider virtual or proper ferroelectric with an optic phonon mode that softens at a Curie point. We also consider a decay mechanism linked to the conductance of the ferroic, thus manifesting itself as the dielectric loss in the material. Our key finding is that the influence of the soft phonon dispersion on the surface potential distribution, complex impedance, and dielectric losses are evidently strong in the vicinity (~10–30 K) of the Curie temperature. Additionally, we quantified how the spatial distribution and frequency spectra of the complex impedance and the dielectric losses react on the dynamics of the soft phonons near the Curie point. These results set the stage for characterization of polar phase transitions with nanoscale microwave measurements, providing a complementary approach to well established electromechanical measurements for fundamental understanding of ferroelectric properties as well as their applications in telecommunication and computing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Low frequency, 100–600 MHz, searches with axion cavity haloscopes

We investigate reentrant and dielectric loaded cavities for the purpose of extending the range of axion cavity haloscopes to lower masses, below the range where the Axion Dark Matter experiment (ADMX) has already searched. Reentrant and dielectric loaded cavities were simulated numerically to calculate and optimize their form factors and quality factors. A prototype reentrant cavity was built and its measured properties were compared with the simulations. We estimate the sensitivity of axion dark matter searches using reentrant and dielectric loaded cavities inserted in the existing ADMX magnet at the University of Washington and a large magnet being installed at Fermilab. Published by the American Physical Society 2024

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗