Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “single crystal materials”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Oxide perovskite crystals for HTSC film substrates microwave applications

The research focused upon generating new substrate materials for the deposition of superconducting yttrium barium cuprate (YBCO) has yielded several new hosts in complex perovskites, modified perovskites, and other structure families. New substrate candidates such as Sr(Al(1/2)Ta(1/2))O3 and Sr(Al(1/2)Nb(1/2))O3, Ba(Mg(1/3)Ta(2/3))O3 in complex oxide perovskite structure family and their solid solutions with ternary perovskite LaAlO3 and NdGaO3 are reported. Conventional ceramic processing techniques were used to fabricate dense ceramic samples. A laser heated molten zone growth system was utilized for the test-growth of these candidate materials in single crystal fiber form to determine crystallographic structure, melting point, thermal, and dielectric properties as well as to make positive identification of twin free systems. Some of those candidate materials present an excellent combination of properties suitable for microwave HTSC substrate applications.

Bhalla, A. S.↗
DOE OSTI2024

Eliminating chemo-mechanical degradation of lithium solid-state battery cathodes during >4.5 V cycling using amorphous Nb2O5 coatings

Abstract Lithium solid-state batteries offer improved safety and energy density. However, the limited stability of solid electrolytes (SEs), as well as irreversible structural and chemical changes in the cathode active material, can result in inferior electrochemical performance, particularly during high-voltage cycling (>4.3 V vs Li/Li + ). Therefore, new materials and strategies are needed to stabilize the cathode/SE interface and preserve the cathode material structure during high-voltage cycling. Here, we introduce a thin (~5 nm) conformal coating of amorphous Nb 2 O 5 on single-crystal LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode particles using rotary-bed atomic layer deposition (ALD). Full cells with Li 4 Ti 5 O 12 anodes and Nb 2 O 5 -coated cathodes demonstrate a higher initial Coulombic efficiency of 91.6% ± 0.5% compared to 82.2% ± 0.3% for the uncoated samples, along with improved rate capability (10x higher accessible capacity at 2C rate) and remarkable capacity retention during extended cycling (99.4% after 500 cycles at 4.7 V vs Li/Li + ). These improvements are associated with reduced cell polarization and interfacial impedance for the coated samples. Post-cycling electron microscopy analysis reveals that the Nb 2 O 5 coating remains intact and prevents the formation of spinel and rock-salt phases, which eliminates intra-particle cracking of the single-crystal cathode material. These findings demonstrate a potential pathway towards stable and high-performance solid-state batteries during high-voltage operation.

Science & Technology - Other Topics↗
DOE OSTI2023

Self-selecting vapor growth of transition-metal-halide single crystals

Transition-metal halides can host a large variety of novel phenomena, such as magnetism in the monolayer limit, quantum spin liquid and spiral spin liquid states, topological magnons, and chiral phonons. Sizable high-quality single crystals are necessary for investigations of magnetic and lattice excitations by, for example, inelastic neutron scattering. In this paper, we review a less well-known vapor transport technique, self-selecting vapor growth, and report our growths of transition-metal halides using this technique. We report the growth and characterizations of sizable single crystals of α–RuCl 3 , CrCl 3 , Ru 1–x Cr x Cl 3 , and CrBr 3 . In order to expedite the conversion of starting powder to single crystals, we modified the technique by cooling the growth ampoule through an appropriate temperature range. Our work shows that the self-selecting vapor transport technique can provide large single crystals of transition-metal halides, demonstrating its potential for providing high-quality single crystals of quantum materials.

2-dimensional systems↗
NASA NTRS1985

Materials for advanced rocket engine turbopump turbine blades

A study program was conducted to identify those materials that will provide the greatest benefits as turbine blades for advanced liquid propellant rocket engine turbines and to prepare technology plans for the development of those materials for use in the 1990 through 1995 period. The candidate materials were selected from six classes of materials: single-crystal (SC) superalloys, oxide dispersion-strengthened (ODS) superalloys, rapid solidification processed (RSP) superalloys, directionally solidified eutectic (DSE) superalloys, fiber-reinforced superalloy (FRS) composites, and ceramics. Properties of materials from the six classes were compiled and evaluated and property improvements were projected approximately 5 years into the future for advanced versions of materials in each of the six classes.

Chandler, W. T.↗
DOE OSTI2023

Synthesis and physical properties of a new layered ferromagnet Cr 1.21 Te 2

Single crystals of a new layered compound, Cr 1.21 Te 2 , were synthesized via a vapor transport method. The crystal structure and physical properties were characterized by single crystal and powder x-ray diffraction, temperature- and field-dependent magnetization, zero-field heat capacity, and angle-resolved photoemission spectroscopy. Cr 1.21 Te 2 , containing two Cr sites, crystalizes in a trigonal structure with a space group P-3 (No. 147). The Cr site in the interstitial layer is partially occupied. Physical property characterizations indicate that Cr 1.21 Te 2 is metallic with hole pockets at the Fermi energy and undergoes a ferromagnetic phase transition at ~ 173 K. The magnetic moments align along the c axis in the ferromagnetic state. Based on low-temperature magnetization, the spin stiffness constant, D, and spin excitation gap, Δ , were estimated according to Bloch's law to be D = 94 ± 17 meV Å 2 and Δ = 0.45 ± 0.33 meV, suggesting its possible application as a low dimensional ferromagnet.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Enabling high energy lithium metal batteries via single-crystal Ni-rich cathode material co-doping strategy

High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi<:sub>0.88 Co 0.09 Mn 0.03 O 2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg- 1 at 0.1 °C and 25 °C.

25 ENERGY STORAGE↗
DOE OSTI2025

Ferromagnetic moment in the magnetoelectric antiferromagnet Co 4 ⁢Ta 2 ⁢O 9 : Evidence of the 𝑃⁢1 magnetic space group

Exploring ferromagnetic moments in magnetoelectric materials is of both fundamental and technological importance. It enables the control of the correlated state using an uncompensated moment. However, its material realization is challenging owing to its exclusive microscopic mechanisms. Here, we report a nearly isotropic ferromagnetic moment in the magnetoelectric antiferromagnet Co 4 ⁢Ta 2 ⁢O 9 , by performing dc and ac magnetic susceptibility, magnetization, and neutron diffraction measurements on identical single crystals. Combined with the group theory analysis, we demonstrate a 𝑃⁢1 magnetic space group. This implies that physical activities can occur along any crystallographic direction, which explains the unusual magnetoelectric property of Co 4⁢ Ta 2⁢ O 9 . The ground state is classified as the M-type altermagnet based on the magnetic point group. Our study provides essential information to resolve the debate on the magnetic ground state and understand the magnetoelectric properties of the related compound with the prospect of observing and examining the 𝑃⁢1 magnetic space group or ferromagnet in ferroelectrics.

Antiferromagnets↗
DOE OSTI2022

Fluctuating Ru trimer precursor to a two-stage electronic transition in RuP

Superconductivity in binary ruthenium pnictides occurs proximal to and upon suppression of a non-magnetic ground state, preceded by a pseudogap phase associated with Fermi surface instability, and its critical temperature, T c , is maximized around the pseudogap quantum critical point. By analogy with isoelectronic iron based counterparts, antiferromagnetic fluctuations became ''usual suspects" as putative mediators of superconducting pairing. Here we report on a high temperature local symmetry breaking in RuP, nonsuperconducting parent of the maximum- T c branch of these novel superconductors, revealed by combined nanostructure-sensitive powder and single crystal X-ray total scattering analyses. Large local distortions of Ru chains associated with orbital-charge trimerization, further assembled into hexamers, exist above the two-stage electronic transition in RuP. In the pseudogap regime the precursors order with distortions retaining their strength, whereas they acquire spin-singlet characteristics which dramatically enhances the distortion as the nonmagnetic ground state establishes. The precursors enable the nonmagnetic ground state and presumed complex oligomerization, and the relevance of pseudogap fluctuations for superconductivity emerges as a distinct prospect. As a transition metal system in which partial d-manifold filling combined with high crystal symmetry promotes electronic instabilities, this represents a further example of local electronic precursors underpinning the macroscopic collective behavior of quantum materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Nanoscale heterogeneity induced by nonmagnetic Zn dopants in the quantum critical metal CeCoIn 5 : 115 In NQR/NMR and 59 Co NMR study

We report antiferromagnetism in a prototypical quantum critical metal CeCoIn 5 is known to be induced by slight substitutions of nonmagnetic Zn atoms for In. In nominally 7% Zn-substituted CeCoIn 5 , an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn-doped CeCoIn 5 by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates 1/T 1 indicate that the AFM state is locally nucleated around Zn substituents in the matrix of a heavy fermion state, and percolates through the bulk at the AFM transition temperature T N . At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature Tc, and the SC state permeates through the AFM regions via a SC proximity effect. Applying an external magnetic field induces a spin-flop transition near 5T, reducing the volume of the AFM regions. Consequently, a short-ranged inhomogeneous AFM state survives and coexists with a paramagnetic Fermi liquid state at high fields.

36 MATERIALS SCIENCE↗
NASA NTRS2014

Investigation of Backside Textures for Genesis Solar Wind Silicon Collectors

Genesis solar wind collectors were comprised of a suite of 15 types of ultrapure materials. The single crystal, pure silicon collectors were fabricated by two methods: float zone (FZ) and Czochralski (CZ). Because of slight differences in bulk purity and surface cleanliness among the fabrication processes and the specific vendor, it is desirable to know which variety of silicon and identity of vendor, so that appropriate reference materials can be used. The Czochralski method results in a bulk composition with slightly higher oxygen, for example. The CZ silicon array wafers that were Genesis-flown were purchased from MEMC Electronics. Most of the Genesis-flown FZ silicon was purchased from Unisil and cleaned by MEMC, although a few FZ wafers were acquired from International Wafer Service (IWS).

Gonzalez, C. P.↗
DOE OSTI2022

Enhancement of charge-neutral fermionic excitations near the spin-flop transition in the magnetic Kondo material YbIr 3 Si 7

The new Kondo material YbIr 3 Si 7 , similar to other Kondo insulators, has been reported to exhibit charge-neutral fermionic excitations through measurements of specific heat and thermal conductivity at low temperatures. We performed 29 Si-NMR on YbIr 3 Si 7 to investigate the magnetic response of charge-neutral fermions from a microscopic perspective. In low magnetic fields parallel to the c axis, a single NMR peak in the paramagnetic state splits into three peaks below TN. In contrast, only a slight shift of the single NMR peak was observed in high magnetic fields. This spectral change as a function of the c-axis magnetic field is interpreted as a spin-flop transition, at which the magnetic moments oriented along the c axis antiferromagnetic (AFM-I) phase are rotated to the ab plane with a ferromagnetic component along the c-axis (AFM-II phase). In the vicinity of the spin-flop magnetic field H M , the nuclear spin-lattice relaxation rate 1/T 1 was found to be proportional to temperature at low temperatures, indicating the existence of charge-neutral fermions. Furthermore, a peak of 1/T 1 versus the c-axis magnetic field suggests that the charge-neutral fermions in YbIr 3 Si 7 are closely related to its magnetic properties. Our findings shed light on the origin of charge-neutral fermions in insulators.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Chemo-Mechanics of α-V 2 O 5 During Lithiation and Implications for Rechargeable Battery Cathodes

Chemo-mechanical degradation of layered oxide electrodes is strongly influenced by crystallographic anisotropy, local stress evolution, and ion insertion, yet the intrinsic mechanical response of layered materials remains incompletely understood. Indeed, most prior studies have focused on polycrystalline materials but single crystals enable direct observation of coupling between anisotropic ion diffusion and mechanical response. This study aims to determine how crystallographic anisotropy and lithiation affect deformation, fracture, and mechanical properties in single-crystal V 2 O 5 , and compares this behavior with polycrystalline counterparts. Polycrystalline V 2 O 5 thin films and single-crystal α-V 2 O 5 were studied using nanoindentation, scanning electron microscopy, focused ion beam cross-sectioning, and Raman spectroscopy. Single crystals were tested in pristine and chemically lithiated states, including experiments in which crystals were first plastically deformed via nanoindentation and subsequently lithiated. Polycrystalline films exhibited significantly higher hardness and elastic modulus than single crystals. Single crystals indented normal to the exposed (001) basal plane exhibited pronounced anisotropic deformation, including directional slip, crystallographically-guided cracking, anisotropic crack propagation, interlayer separation, and shear localization. Lithiation caused substantial softening, reduced hardness and modulus, and suppressed displacement bursts during nanoindentation, while previously indented regions showed crack formation and growth upon lithiation. Mechanical behavior of α-V 2 O 5 is strongly governed by crystallographic anisotropy and further altered by lithiation, with pre-existing deformation serving as a strong driver of fracture during ion insertion. These findings illuminate the coupling among ion insertion, deformation, and fracture in layered oxides and provide a basis for understanding and mitigating mechanical failure in electrochemical energy-storage materials.

Anisotropy↗
DOE OSTI2022

Positive spin Hall magnetoresistance in single-crystalline Pt/CoO(001) bilayers

Here, the spin Hall magnetoresistance (SMR) effect in single-crystalline Pt/CoO(001) bilayers has been systematically investigated. X-ray magnetic linear dichroism measurements prove that CoO antiferromagnetic (AFM) spins can be switched into the direction orthogonal to the applied field. We find the SMR signal is comprised of two components related to either the switching of CoO AFM Néel order or the applied strong field effect. Both SMR components show a “positive” angular dependence with $R_{∥} > R_{⊥}$, while $R_{∥} (R_{⊥})$ is defined as the resistance with the applied in-plane field parallel (perpendicular) to the current. The observed positive SMR is mainly attributed to the uncompensated spins at the Pt/CoO interface, instead of the CoO AFM spins. Our study may attract a great deal of interest to understand the complicated SMR effect in AFM spintronics materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1975

Glass-Si heterojunction solar cells

An increase in efficiency from 2% to over 7% was achieved by a solar cell that used polycrystal silicon heterojunction with SnO2 glass. For Single crystal substrates, efficiencies close to 10% were measured. These cells had the same structures as polycrystalline cells. Work on p+/n heterojunction using In2O3 glass resulted in cells of 3% efficiency on polycrystalline material and 4% efficiency on single crystal material.

Ahrons, R. W.↗
NASA NTRS2002

Generalized Reliability Methodology Applied to Brittle Anisotropic Single Crystals

A generalized reliability model was developed for use in the design of structural components made from brittle, homogeneous anisotropic materials such as single crystals. The model is based on the Weibull distribution and incorporates a variable strength distribution and any equivalent stress failure criteria. In addition to the reliability model, an energy based failure criterion for elastically anisotropic materials was formulated. The model is different from typical Weibull-based models in that it accounts for strength anisotropy arising from fracture toughness anisotropy and thereby allows for strength and reliability predictions of brittle, anisotropic single crystals subjected to multiaxial stresses. The model is also applicable to elastically isotropic materials exhibiting strength anisotropy due to an anisotropic distribution of flaws. In order to develop and experimentally verify the model, the uniaxial and biaxial strengths of a single crystal nickel aluminide were measured. The uniaxial strengths of the <100> and <110> crystal directions were measured in three and four-point flexure. The biaxial strength was measured by subjecting <100> plates to a uniform pressure in a test apparatus that was developed and experimentally verified. The biaxial strengths of the single crystal plates were estimated by extending and verifying the displacement solution for a circular, anisotropic plate to the case of a variable radius and thickness. The best correlation between the experimental strength data and the model predictions occurred when an anisotropic stress analysis was combined with the normal stress criterion and the strength parameters associated with the <110> crystal direction.

Salem, Jonathan A.↗
NASA NTRS1984

Low-cost single-crystal turbine blades, volume 2

The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through extensive mechanical property testing, rig testing, and 200 hours of endurance engine testing. These Program objectives were achieved. The exothermic casting process was successfully developed into a low-cost nonproperietary method for producing single-crystal castings. Single-crystal MAR-M 247 and two derivatives DS alloys developed during this project, NASAIR 100 and SC Alloy 3, were fully characterized through mechanical property testing. SC MAR-M 247 shows no significant improvement in strength over directionally solidified (DS) MAR-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. Firtree testing, holography, and strain-gauge rig testing were used to determine the effects of the anisotropic characteristics of single-crystal materials. No undesirable characteristics were found. In general, the single-crystal material behaved similarly to DS MAR-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined. These blades were successfully engine-tested.

Strangman, T. E.↗
DOE OSTI2024

Three-dimensional superconductivity induced by an extremely small amount of Li in Li x ⁢SnSe 2

Unconventional superconductivity occurs often in materials with low dimensionality. Furthermore, we report superconductivity observed in layered Li x SnSe 2 with the superconducting transition temperature T c ~ 6 K. Through L⁢i + intercalation in semiconducting SnSe 2 via electrochemical process, Li x ⁢SnSe 2 is formed with an extremely small x value as estimated from the c-axis lattice parameter, carrier concentration, and first-principles calculations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗