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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Frustrated Heisenberg J 1 – J 2 model within the stretched diamond lattice of LiYbO 2

We investigate the magnetic properties of LiYbO 2 , containing a three-dimensionally frustrated, diamondlike lattice via neutron scattering, magnetization, and heat capacity measurements. The stretched diamond network of Yb 3+ ions in LiYbO 2 enters a long-range incommensurate, helical state with an ordering wave vector k = (0.384,±0.384,0) that “locks-in” to a commensurate k = (1/3,±1/3,0) phase under the application of a magnetic field. The spiral magnetic ground state of LiYbO 2 can be understood in the framework of a Heisenberg J 1 –J 2 Hamiltonian on a stretched diamond lattice, where the propagation vector of the spiral is uniquely determined by the ratio of J 2 /|J 1 |. Here, the pure Heisenberg model, however, fails to account for the relative phasing between the Yb moments on the two sites of the bipartite lattice, and this detail as well as the presence of an intermediate, partially disordered, magnetic state below 1 K suggests interactions beyond the classical Heisenberg description of this material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Elastic moduli of hexagonal diamond and cubic diamond formed under shock compression

The relative stiffnesses and strengths of hexagonal diamond and cubic diamond constitute long standing unresolved issues, because relevant experimental results are lacking. Laser interferometry was used to experimentally determine the longitudinal sound speeds and moduli in hexagonal diamond and cubic diamond formed during the shock compression of graphite. The hexagonal diamond longitudinal moduli are significantly larger than the cubic diamond longitudinal moduli, and even exceed averaged cubic diamond single crystal values. Here, the measured hexagonal diamond longitudinal moduli, combined with high-pressure bulk moduli for cubic diamond single crystals, show that shock-formed hexagonal diamond shear moduli are larger than the shear moduli for cubic diamond single crystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1991

Piezoresistive sensors for measurement of thermally-induced stresses in microelectronics

The general theory of conduction in a piezoresistive material subjected to temperature change is derived and the basic equations needed to design and apply test chips for thermal stress measurement are established. A general expression is obtained for the resistance changes which occur in an arbitrarily oriented 1D filamentary conductor subjected to general 3D stress states and arbitrary temperature changes. The derived formula is valid for crystals such as silicon which have cubic symmetry and diamond lattice structures. Basic equations are presented for the resistance changes experienced by stressed in-plane resistors fabricated on (100) silicon wafers. The established theory is applied to a simple two-element sensor rosette. A test chip containing this rosette configuration is designed and fabricated, and a suitable calibration system is constructed.

Suhling, J. C.↗
NASA NTRS2004

Very High Efficiency, Miniaturized, Long-Lived Alpha Particle Power Source Using Diamond Devices for Extreme Space Environments

A power source that converts a-particle energy into electricity by coulomb collision in doped diamond films is described. Alpha particle decay from curium-244 creates electron-hole pairs by free- ing electrons and holes inside the crystal lattice in N- and P-doped diamond films. Ohmic contacts provide electrical connection to an electronic device. Due to the built-in electric field at the rectifying junction across the hT- and P-doped diamond films, the free electrons are constrained to traveling in generally one direction. This one direction then supplies electrons in a manner similar to that of a battery. The radioactive curium layer may be disposed on diamond films for even distribution of a-particle radiation. The resulting power source may be mounted on a diamond substrate that serves to insulate structures below the diamond substrate from a-particle emission. Additional insulation or isolation may be provided in order to prevent damage from a-particle collision. N-doped silicon may be used instead of N-doped diamond.

Elizabeth A Kolawa↗
DOE OSTI2024

Response of fs-Laser-Irradiated Diamond by Ultrafast Electron Diffraction

Structural details of the proposed solid–liquid phase transition of carbon have remained elusive, despite years of study. While it is theorized that novel carbon materials form from a liquid precursor, experimental studies have lacked the temporal and spatial resolution necessary to fully characterize the purported liquid state. Here, in this work, we utilize megaelectronvolt-ultrafast electron diffraction (MeV-UED) to study laser irradiated submicron diamond thin films in a pump–probe scheme with picosecond time resolution to visualize potential structural changes of excited diamond. We probe the structure of diamond using a combination of fluences (13, 40 J/cm 2 ) and time delays (10, 25, 100 ps), but observe negligible changes in the static diffraction pattern of diamond and an overall decrease in diffraction intensity up to 100 ps after the excitation pulse. We thus conclude that no appreciable amount of liquid or graphitized carbon is present and highlight the structural resilience of bulk diamond to intense 800 nm ultrafast laser pulses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2022

TransHab Tapered Diamond Stitch Methods - Crewed Inflatable Softgoods Structures

The NASA TransHab project was a flight development program of a crewed inflatable habitat designed for in-space use. Through the course of the development, several novel technologies were developed and patented by NASA. One of these patents included information regarding a custom seam stitch that was used in the TransHab restraint layer design. As the patent protection has ended, the details of the custom seam stitch are being disclosed. The seam stitch developed during the TransHab program is known as the ‘tapered diamond stitch’ and includes both a ‘single’ and ‘double’ tapered diamond pattern for ‘end termination’ and ‘continuous’ webbing components respectively. It was designed for 1-in wide Kevlar webbings with load ratings of 6,000 lbf and 12,500 lbf. The stitch pattern was designed to gradually transfer load along the length of the seam using a tapered diamond geometry. The diamond stitch has been shown in tensile testing to provide greater than 85% load strength efficiency, compared to the pristine webbing.

transhab↗
NASA NTRS1998

Structures and Mechanical Properties of Natural and Synthetic Diamonds

A revolution in the diamond technology is in progress, as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear-resistant, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly regarding solid lubricants and lubricating materials and systems. This paper reviews the structures and properties of natural and synthetic diamonds to gain a better understanding of the tribological properties of diamond and related materials. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

Miyoshi, Kazuhisa↗
NASA NTRS1998

Structures and Mechanical Properties of Natural and Synthetic Diamonds

A revolution in diamond technology is in progress as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly solid lubricants and lubricating materials and systems. This chapter reviews the structures and properties of natural and synthetic diamond to gain a better understanding of the tribological properties of diamond and related materials to be described in the following chapters. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

Miyoshi, Kazuhisa↗
DOE OSTI2022

Melting diamond in the diamond cell by laser-flash heating

The phase behavior of carbon at high pressure and the search for carbon structures denser than diamond has been explored for decades showing large discrepancies, with many fundamental questions remaining unresolved. Here we show evidence of melting above the graphite-diamond-liquid (GDL) triple point (~13 GPa, 4000 K) up to 50 GPa on samples recovered from single flash-heating events using spectroscopic and electron microscopic methods. The results show that for all pressures, diamond melts below the triple point temperature contradicting previous studies, most of which predict a positive slope of the melting curve.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Highly ordered graphite (HOPG) to hexagonal diamond (lonsdaleite) phase transition observed on picosecond time scales using ultrafast x-ray diffraction

Here, the response of rapidly compressed highly oriented pyrolytic graphite (HOPG) normal to its basal plane was investigated at a pressure of ~80 GPa. Ultrafast x-ray diffraction using ~100 fs pulses at the Materials Under Extreme Conditions sector of the Linac Coherent Light Source was used to probe the changes in crystal structure resulting from picosecond timescale compression at laser drive energies ranging from 2.5 to 250 mJ. A phase transformation from HOPG to a highly textured hexagonal diamond structure is observed at the highest energy, followed by relaxation to a still highly oriented, but distorted graphite structure following release. We observe the formation of a highly oriented lonsdaleite within 20 ps, subsequent to compression. This suggests that a diffusionless martensitic mechanism may play a fundamental role in phase transition, as speculated in an early work on this system, and more recent static studies of diamonds formed in impact events.

58 GEOSCIENCES↗
DOE OSTI2022

Machine learning the metastable phase diagram of covalently bonded carbon

Abstract Conventional phase diagram generation involves experimentation to provide an initial estimate of the set of thermodynamically accessible phases and their boundaries, followed by use of phenomenological models to interpolate between the available experimental data points and extrapolate to experimentally inaccessible regions. Such an approach, combined with high throughput first-principles calculations and data-mining techniques, has led to exhaustive thermodynamic databases (e.g. compatible with the CALPHAD method), albeit focused on the reduced set of phases observed at distinct thermodynamic equilibria. In contrast, materials during their synthesis, operation, or processing, may not reach their thermodynamic equilibrium state but, instead, remain trapped in a local (metastable) free energy minimum, which may exhibit desirable properties. Here, we introduce an automated workflow that integrates first-principles physics and atomistic simulations with machine learning (ML), and high-performance computing to allow rapid exploration of the metastable phases to construct “metastable” phase diagrams for materials far-from-equilibrium. Using carbon as a prototypical system, we demonstrate automated metastable phase diagram construction to map hundreds of metastable states ranging from near equilibrium to far-from-equilibrium (400 meV/atom). We incorporate the free energy calculations into a neural-network-based learning of the equations of state that allows for efficient construction of metastable phase diagrams. We use the metastable phase diagram and identify domains of relative stability and synthesizability of metastable materials. High temperature high pressure experiments using a diamond anvil cell on graphite sample coupled with high-resolution transmission electron microscopy (HRTEM) confirm our metastable phase predictions. In particular, we identify the previously ambiguous structure of n -diamond as a cubic-analog of diaphite-like lonsdaelite phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Magic Diamond: Covalent Bond Formation of Melamine and Other Amines on Nanodiamond Surfaces

High-temperature, high-pressure (HPHT) nanodiamond (ND) hosts nitrogen-vacancy (NV) centers, solid-state qubits that enable room-temperature quantum sensing by all-optical magnetometry, electrometry, and thermometry. However, the covalent surface functionalization of nanoscale diamond remains largely limited to carboxylate-based chemistries. Amine termination is particularly attractive because theoretical studies predict suppression of midgap states and extended electron-spin coherence times. Recently, chemical activation of alcohol-terminated NDs to alkyl bromides (ND-Br) using SOBr2 has enabled nucleophilic substitution through a carbocation intermediate, allowing formation of simple amine terminations. Here, we evaluate whether sterically demanding amines can form covalent diamond−nitrogen bonds on ND-Br surfaces. ND-Br was reacted with branched, linear, and cyclic amines, including polyethylenimine, diethylenetriamine, and melamine. X-ray spectroscopies were used to confirm successful and to probe the resulting electronic structure at the diamond−amine interface. These results expand the chemical toolbox for tuning diamond surface dipoles and electron affinity, providing new pathways for engineering nanodiamond surfaces for quantum sensing and photocatalysis applications.

Amines↗
DOE OSTI2021

Metastability of diamond ramp-compressed to 2 terapascals

Carbon is the fourth-most prevalent element in the Universe and essential for all known life. In the elemental form it is found in multiple allotropes, including graphite, diamond and fullerenes, and it has long been predicted that even more structures can exist at pressures greater than those at Earth’s core. Several phases have been predicted to exist in the multi-terapascal regime, which is important for accurate modelling of the interiors of carbon-rich exoplanets. By compressing solid carbon to 2 terapascals (20 million atmospheres; more than five times the pressure at Earth’s core) using ramp-shaped laser pulses and simultaneously measuring nanosecond-duration time-resolved X-ray diffraction, we found that solid carbon retains the diamond structure far beyond its regime of predicted stability. The results confirm predictions that the strength of the tetrahedral molecular orbital bonds in diamond persists under enormous pressure, resulting in large energy barriers that hinder conversion to more-stable high-pressure allotropes, just as graphite formation from metastable diamond is kinetically hindered at atmospheric pressure. In conclusion, this work nearly doubles the highest pressure at which X-ray diffraction has been recorded on any material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Structural, optical, and thermal properties of BN thin films grown on diamond via pulsed laser deposition

Heterostructures based on ultrawide-bandgap (UWBG) semiconductors (bandgap > 4.0 eV), such as BN and diamond, hold significant importance for the development of high-power electronics in the next generation. However, achieving in situ heteroepitaxy of BN/diamond or vice versa remains exceptionally challenging due to the complex growth kinetics involved. In this work, we grew BN thin film on (100) single-crystal diamonds using pulsed laser deposition and investigated its structural, magnetic, optical, and thermal properties. Throughout this study, the structural analyses confirmed the growth of BN films, which exhibited diamagnetic behavior at room temperature. Notably, the film demonstrated anisotropic refractive index characteristics within the visible-to-near-infrared wavelength range. The room-temperature cross-plane thermal conductivity of BN is 1.53 ± 0.77 W/mK, while the thermal conductance of the BN/diamond interface is 20 ± 2 MW/m 2 ⁢K. These findings have significant implications for a range of device applications based on UWBG BN/diamond heterostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Regulating phase behavior of nanoparticle assemblies through engineering of DNA-mediated isotropic interactions

Self-assembly of isotropically interacting particles into desired crystal structures could allow for creating designed functional materials via simple synthetic means. However, the ability to use isotropic particles to assemble different crystal types remains challenging, especially for generating low-coordinated crystal structures. Here, we demonstrate that isotropic pairwise interparticle interactions can be rationally tuned through the design of DNA shells in a range that allows transition from common, high-coordinated FCC-CuAu and BCC-CsCl lattices, to more exotic symmetries for spherical particles such as the SC-NaCl lattice and to low-coordinated crystal structures (i.e., cubic diamond, open honeycomb). The combination of computational and experimental approaches reveals such a design strategy using DNA-functionalized nanoparticles and successfully demonstrates the realization of BCC-CsCl, SC-NaCl, and a weakly ordered cubic diamond phase. The study reveals the phase behavior of isotropic nanoparticles for DNA–shell tunable interaction, which, due to the ease of synthesis is promising for the practical realization of non-close-packed lattices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1996

On the Reaction of FNO2 with CH3, t-butyl, and C13H21

Theoretical studies are reported for the reaction of FN02 with the radicals CH3, t-butyl, and C13H21, which are templates for the radical site of a hydrogenated diamond surface. All structures axe fully optimized using density functional theory (DFT) based on the B3LYP functional. Calibration calculations axe performed for CH3 + FNO2 using the coupled cluster approach, the the internally contracted multireference configuration. interaction method, and second order perturbation theory based upon complete active space SCF (CASSCF) reference wave function. These calibration calculations support the B3LYP approach for the calculation of bond energies, but show the B3LYP barrier is too low. Combining the calibration calculations with the larger clusters yields our best estimate of a barrier of about 10 kcal/mol. for the reaction of FNO2 with a radical site on hydrogenated diamond.

Thuemmel, H. T.↗
DOE OSTI2024

Dataset of simulated vibrational density of states and X-ray diffraction profiles of mechanically deformed and disordered atomic structures in Gold, Iron, Magnesium, and Silicon

This dataset is comprised of a library of atomistic structure files and corresponding X-ray diffraction (XRD) profiles and vibrational density of states (VDoS) profiles for bulk single crystal silicon (Si), gold (Au), magnesium (Mg), and iron (Fe) with and without disorder introduced into the atomic structure and with and without mechanical loading. Included with the atomistic structure files are descriptor files that measure the stress state, phase fractions, and dislocation content of the microstructures. All data was generated via molecular dynamics or molecular statics simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code. This dataset can inform the understanding of how local or global changes to a materials microstructure can alter their spectroscopic and diffraction behavior across a variety of initial structure types (cubic diamond, face-centered cubic (FCC), hexagonal close-packed (HCP), and body-centered cubic (BCC) for Si, Au, Mg, and Fe, respectively) and overlapping changes to the microstructure (i.e., both disorder insertion and mechanical loading).

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗