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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Growth of single crystal III-V semiconductors on amorphous substrates

This disclosure provides systems, methods, and apparatus related to the growth of single crystal III-V semiconductors on amorphous substrates. In one aspect, a shape of a semiconductor structure to be formed on an amorphous substrate is defined in a resist disposed on the amorphous substrate. A boron group element is deposited over the amorphous substrate. A ceramic material is deposited on the boron group element. The resist is removed from the amorphous substrate. The ceramic material is deposited to cover the boron group element. The amorphous substrate and materials deposited thereon are heated in the presence of a gas including a nitrogen group element to grow a single crystal semiconductor structure comprising the boron group element and the nitrogen group element.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Imprinting bulk amorphous alloys at room temperature

A technique is disclosed for straining an amorphous alloy at ambient temperature to plastically and homogeneously deform the amorphous alloy, such that at least an exterior surface of the deformed amorphous alloy is substantially free of shear bands. An amorphous alloy may be strained at a rate of less than about 9×10−5 s−1 or by multiple passes of cold rolling. A pattern from a die may be imprinted into the amorphous alloy when strained, and the amorphous alloy may be used as a die to plastically strain other materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Direct observation of 3D atomic packing in monatomic amorphous materials

Liquids and solids are two fundamental states of matter. Although the structure of crystalline solids has long been solved by crystallography, our understanding of the 3D atomic structure of liquids and amorphous materials remained speculative. In 1952, Frank hypothesized that icosahedral order is the prevalent atomic motif in monatomic liquids. Over the past six decades, there have been a great deal of experimental, computational and theoretical studies to understand the structure of liquids and amorphous materials. A polytetrahedral packing model was proposed to explain the 3D atomic structure of monatomic liquids and amorphous materials, in which icosahedral order is a key feature. The icosahedral order has also been found to play an important role in the structure of metallic glasses and quasicrystals. Here we advance atomic electron tomography to determine for the first time the 3D atomic positions in monatomic amorphous materials, including a Ta thin film and two Pd nanoparticles. Despite the different chemical composition and synthesis methods, we observe that pentagonal bipyramids are the most abundant atomic motifs in these amorphous materials. Contrary to the traditional understanding, the pentagonal bipyramids do not assemble full icosahedra, but are closely connected with each other to form networks that extend to medium-range scale. Our molecular dynamic simulations, coupled with experimental results, further reveal that the 3D atomic structure of monatomic liquids is similar to the experimental amorphous material. Moreover, we find that the pentagonal bipyramid networks, prevalent in monatomic liquids, rapidly grow in size and form a fraction of full icosahedra during the quench from a liquid to a metallic glass state, providing a possible new picture of structural evolution through the glass transition.

Yuan, Yakun↗
DOE OSTI2024

Highly disordered amorphous Li-battery electrolytes

"Medium-entropy" highly disordered amorphous Li garnets, with ≥4 unique local bonding units (LBUs), hold promise for use as solid-state electrolytes in hybrid or all-solid-state batteries owing to their grain-boundary-free nature and low-temperature synthesis requirement. Through this work, we resolved the local structure of amorphous Li garnet and understood their implication for Li dynamics. These medium-entropy amorphous structures possess unique characteristics with edge- and face-sharing LBUs, not conforming to the classic Zachariasen glass formation rules, and can be synthesized in a wide but processing-friendly temperature range (<680°C). Within these amorphous structures, Li and Zr are identified as the network formers and La as network modifier, with maxima in Li dynamics observed for smaller Li-O and Zr-O coordination; this structure understanding serves as a baseline for identifying additional network formers to further modulate Li transport. In conclusion, our insight provides fundamental guidelines for the structure and phase design for amorphous Li garnets and paves the way for their integration in next-generation batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Fast Neutron Irradiation Embrittlement-ductilitization of an Iron-based Amorphous Alloy using In Situ Synchrotron X-ray Diffraction

Amorphous Fe-based nanostructured alloy coatings thermally sprayed on bcc steel substrate, were subjected to neutron irradiation doses up to 2 × 10 19 n/cm 2 . It is shown that the interplay between embrittlement and recovery of ductility is governed by amorphous to crystallization transition and phase decomposition in which temperature and irradiation dose have reciprocal effects. Microscopic (X-ray diffraction) observations on the behavior of the amorphous Fe-based alloy are correlated with relevant macroscopically observed mechanical behavior. It is shown that amorphous Fe-based alloy coatings maintain and even enhance their amorphous structure with irradiation, exhibit radiation-induced restoration of thermally-induced embrittlement and finally exhibit resistance to ductility loss up to the fluence of 2 × 10 18 n/cm 2 and good thermal stability up to 350 °C. The latter is deduced from X-ray diffraction experiments of in-situ tensile strain application on the irradiated coating.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Amorphization of Pseudocapacitive T−Nb 2 O 5 Accelerates Lithium Diffusivity as Revealed Using Tunable Isomorphic Architectures

Abstract Intercalation pseudocapacitance can combine capacitor‐like power densities with battery‐like energy densities. Such surface‐limited behavior requires rapid diffusion where amorphization can increase solid‐state diffusivity. Here intercalation pseudocapacitive materials with tailored extents of amorphization in T‐Nb 2 O 5 are first reported. Amorphization was characterized with WAXS, XPS, XAFS, and EPR which suggested a peroxide‐rich (O 2 2− ) surface that was consistent with DFT predictions. A series of tunable isomorphic architectures enabled comparisons while independently varying transport parameters. Through process of elimination, solid‐state lithium diffusion was identified as the dominant diffusive‐constraint dictating the maximum voltage sweep rate for surface‐limited kinetics ( v SLT ), termed the Surface‐Limited Threshold (SLT). The v SLT increased with amorphization however stable cycling required crystalline T‐Nb 2 O 5 . A current‐response model using series‐impedances well‐matched these observations. This perspective revealed that amorphization of T‐Nb 2 O 5 enhanced solid‐state diffusion by 12.2 % and increased surface‐limitations by 17.0 % (stable samples). This approach enabled retaining 95 % lithiation capacity at ∼800 mV s −1 (1,600 C‐rate equivalent).

25 ENERGY STORAGE↗
DOE OSTI2019

Study on Magnetic Properties and Degradability of Gas Atomization Fe-Based (Fe-Si-B-P) Amorphous Powder

Fe-based amorphous materials have attracted extensive attention in the application of organic pollutant degradation due to their excellent chemical properties. In this work, a novel Fe-based (Fe-Si-B-P) amorphous powder prepared by gas atomization is employed to decompose azo dyes for wastewater treatment. Its crystalline structure, distribution of particle size, and soft magnetic properties are characterized. The experimental results show that the Fe-based (Fe-Si-B-P) powder is amorphous morphology which might bring many benefits for decomposing organics in waste water. The particle size of the micro-sized spheroidal powder distributes mainly from 10 to 50 μm, and most are about 17~19 μm. The magnetic properties are also investigated. Its saturation magnetization (M{sub S}) and coercivity (H{sub C}) are, respectively, 55 emu/g and 19.6 Oe, which present superb soft magnetic properties. Finally, we studied the degradability of the Fe-based amorphous powder by decomposing the methylene blue in waste water, and the results show that 0.05-g Fe-based amorphous powder can completely degrade the 50 ml methylene blue solution with the concentration of 3 × 10{sup −5} M within 15 min in weak acidic environment, which shows great degradability for wastewater treatment.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Synthesis of amorphous Pd-based nanocatalysts for efficient alcoholysis of styrene oxide and electrochemical hydrogen evolution

Amorphous nanomaterials with long-range disordered structures could possess distinct properties and promising applications, especially in catalysis, as compared with their conventional crystalline counterparts. It is imperative to achieve the controlled preparation of amorphous noble metal-based nanomaterials for the exploration of their phase-dependent applications. Here, in this work, we report a facile wet-chemical reduction strategy to synthesize various amorphous multimetallic Pd-based nanomaterials, including PdRu, PdRh, and PdRuRh. The phase-dependent catalytic performances of distinct Pd-based nanomaterials towards diverse catalytic applications have been demonstrated. Specifically, the usage of PdRu nanocatalysts with amorphous and crystalline face-centered cubic (fcc) phases can efficiently switch the ring-opening route of styrene oxide to obtain different products with high selectivity through alcoholysis reaction and hydrogenation reaction, respectively. Moreover, when used as an electrocatalyst for hydrogen evolution reaction (HER), the synthesized amorphous PdRh nanocatalyst exhibits low overpotential and high turnover frequency values, outperforming its crystalline fcc counterpart and most of the reported Pd-based HER electrocatalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermodynamics of radiation induced amorphization and thermal annealing of Dy 2 Sn 2 O 7 pyrochlore

Thermodynamics and annealing behavior of swift heavy ion amorphized Dy 2 Sn 2 O 7 pyrochlore were studied. Its amorphization enthalpy, defined as the total energetic difference between the irradiation amorphized and undamaged Dy 2 Sn 2 O 7 states, was determined to be 283.6 ± 6.5 kJ/mol by high temperature oxide melt drop solution calorimetry. It has been an enigma that stannate and some other pyrochlores do not follow the general r A /r B -radiation resistance relation seen in most pyrochlore systems. In this paper, we use the amorphization enthalpy, which reflects all the complex chemical and structural characteristics, as a more effective parameter to correlate the radiation damage resistance of pyrochlores with their compositions. It successfully explains the superior radiation damage resistance of the stannate pyrochlores compared with titanate pyrochlores. Differential scanning calorimetry (DSC) reveals a strong exothermic event starting at 978 K, which is attributed to long-range recrystallization based on X-ray diffraction (XRD) analysis, similar to the effect previously observed in Dy 2 Ti 2 O 7 . A second pronounced heat event beginning at ~1148 K, which results from local structural rearrangement, is clearly decoupled from the first event for irradiated Dy 2 Sn 2 O 7 . Both the heat releases measured by DSC on heating to 1023 and 1473 K, and the excess enthalpies of the annealed samples indicate that the recovery to the original, ordered state was not fully achieved up to even 1473 K, despite XRD showing the apparent restoration of crystalline pyrochlore structure. The remaining metastability may be attributed to local disorder in the form of weberite-like short-range domains in the recrystallized material. Intriguingly, the second event for different pyrochlores generally starts at similar temperatures while the onset of the long range recrystallization is compositionally dependent. Finally, the amorphization and thermal annealing behavior observed in irradiated Dy 2 Sn 2 O 7 may provide insights into the general mechanisms of radiation damage and recovery of pyrochlores relevant to their nuclear applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The existence of amorphous phase in Portland cements: Physical factors affecting Rietveld quantitative phase analysis

Rietveld quantitative phase analysis has become a widespread tool for the characterization of Portland cement, both for research and production control purposes. One of the major remaining points of debate is whether Portland cements contain amorphous content or not. This paper presents detailed analyses of the amorphous phase contents in a set of commercial Portland cements, clinker, synthetic alite and limestone by Rietveld refinement of X-ray powder diffraction measurements using both external and internal standard methods. A systematic study showed that the sample preparation and comminution procedure is closely linked to the calculated amorphous contents. Particle size reduction by wet-grinding lowered the calculated amorphous contents to insignificant quantities for all materials studied. No amorphous content was identified in the final analysis of the Portland cements under investigation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Selective Brookite Polymorph Formation Related to the Amorphous Precursor State in TiO 2 Thin Films

A wide variety of brookite TiO 2 synthesis methods have been published over the past several decades, but few studies discuss the underlying mechanism that stabilizes brookite over its stable counterparts, rutile and anatase. Here in this study, we investigate of the effect of pulsed laser deposition parameters on the as-deposited amorphous precursor titania thin films, which subsequently crystallize into stable and metastable TiO 2 polymorphs upon annealing. We find that oxygen pressure in the deposition chamber strongly influences the non-equilibrium state of the amorphous precursor, which ultimately allows for selective polymorph formation. Rutile forms as the dominant phase at low pO 2 < 0.1 mTorr, while anatase is favored at high pO 2 > 5 mTorr. Brookite forms primarily at intermediate pO 2 (0.5-1.0 mTorr). Controlling the amorphous structure (i.e. Ti - O bonding and polyhedral arrangement) of the precursors via oxygen deficiency is therefore likely for the selective formation of crystalline TiO 2 polymorphs from sub-stoichiometric amorphous precursors. Lastly, directing phase selectivity by manipulating the structure and internal energy of the precursor amorphous state may have tremendous potential for synthesis of metastable crystalline phases that exhibit more desirable properties in comparison to their stable counterparts.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing the high-pressure densification of amorphous silica nanomaterials using SBA-15: An investigation into the paradoxical nature of the first sharp diffraction peak

The densification and X-ray scattering of mesoporous silica (SBA-15) were measured simultaneously under gigapascal (GPa) pressures. The results are compared to previous work on amorphous silica (aSiO 2 ) and demonstrate the feasibility of measuring the densification of aSiO 2 nanomaterials with small angle X-ray scattering (SAXS) in-situ in a diamond anvil cell. Compared to fused silica, the position of the SBA-15 first sharp diffraction peak (FSDP) is 7 times more sensitive to pressure and has a transition in its pressure dependance at a lower pressure (~2 GPa vs.~13 GPa). SBA-15 has two densification regimes, low-density amorphous and highdensity amorphous, which have equations of state comparable to low-density amorphous and high-density amorphous fused silica. Further, the transition between these two regimes occurs at a lower pressure than for fused silica (~1.5 GPa vs.~13 GPa). The results suggest that there is no direct relationship between the FSDP position and the aSiO 2 density during compression.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

The facile synthesis, crystallization behavior and magnetic property of FeNiP amorphous nanoparticles

Highlights: • A facile chemistry method was proposed to synthesize amorphous FeNiP nanoparticle. • Phase transformation happened during sintering the amorphous nanoparticle. • Ni nanospheres and monoclinic (Ni,Fe){sub 3}[PO4]{sub 2} nanorods appeared at 800 °C. • Crystallization behavior is α-FeNiP → Ni + FeNi{sub 3} + Ni{sub 3}P → Ni + (Ni,Fe){sub 3}[PO{sub 4}]{sub 2}. • Sintered powders have varied magnetic properties due to phase proportion change. - Abstract: Amorphous FeNiP nanoparticles with homogeneous composition are synthesized by reduction of aqueous Fe{sup 2 +} and Ni{sup 2 +} with sodium borohydride (NaBH{sub 4}) and hypophosphite at room temperature. These amorphous nanoparticles can be crystallized by heating up to 300 °C to form FeNi{sub 3} and Ni{sub 3}P crystals. Ni phase appeared at the sintering temperature of 500 °C, and a special net structure was formed at 700 °C due to the joining and diffusion among different nanoparticles. At a higher temperature of 800 °C, phase transformation happened and only pure Ni nanospheres and monoclinic ((Ni, Fe){sub 3}[PO{sub 4}]{sub 2}) nanorods can be observed, which should be governed by the long-range diffusion in the net structure. The amorphous FeNiP nanoparticles have excellent soft magnetic property with Ms of 13.2 emu/g and Hc of 0.7 Oe. However, the sintered mixing nanoparticles show varied magnetic properties due to the phase transformation and proportion change among different phases involved in.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

E-beam-enhanced solid-state mechanical amorphization of α-quartz: Reduced deformation barrier via localized excess electrons as network modifiers

Under hydrostatic pressure, α-quartz (α-SiO 2 ) undergoes solid-state mechanical amorphization wherein the interpenetration of [SiO 4 ] 2- tetrahedra occurs and the material loses crystallinity. This phase transformation requires a high hydrostatic pressure of 14GPa because the repulsive forces resulting from the ionic nature of the Si–O bonds prevent the severe distortion of the atomic configuration. Herein, we experimentally and computationally demonstrate that e-beam irradiation changes the nature of the interatomic bonds in α-quartz and enhances the solid-state mechanical amorphization at nanoscale. Specifically, during in situ uniaxial compression, a larger permanent deformation occurs in α-quartz submicron pillars compressed during e-beam irradiation than in those without e-beam irradiation. Microstructural analysis reveals that the large permanent deformation under e-beam irradiation originates from the enhanced mechanical amorphization of α-quartz and the subsequent viscoplastic deformation of the amorphized region. Further, atomic-scale simulations suggest that the delocalized excess electrons introduced by e-beam irradiation move to highly distorted atomic configurations and alleviate the repulsive force, thus reducing the barrier to the solid-state mechanical amorphization. In conclusion, these findings deepen our understanding of electron–matter interactions and can be extended to new glass forming and processing technologies at nano- and microscale.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Amorphous electrocatalysts for oxygen and hydrogen evolution reactions: Advances in hydrogen production

The electrochemical splitting of water into oxygen and hydrogen is fundamental for renewable energy storage and conversion. The development of cost-effective and highly efficient electrocatalysts remains essential for industrial-scale implementation of this technology. Recent advances have highlighted the superior activity, stability and structural adaptability of amorphous electrocatalysts compared to their crystalline counterparts. This review critically examines synthesis strategies, characterisation techniques, and the electrochemical performance of amorphous materials for both oxygen evolution (OER) and hydrogen evolution (HER) reactions. Key factors influencing catalytic efficiency, including electronic structure and surface chemistry, are discussed in detail and contextualised with established literature. The review also highlights the critical role of enthalpic contributions in governing reaction energetics and catalyst performance, which aids in understanding and optimising electrocatalytic efficiency. Notably, ongoing research continues to reveal that amorphous catalysts consistently deliver improved performance in water-splitting applications, highlighting their growing relevance in electrocatalysis. The rationale for employing amorphous catalysts in water splitting is articulated, emphasising their unique advantages. By integrating recent findings and outlining future research directions, this review underscores the pivotal role of amorphous materials in advancing sustainable hydrogen production and identifies promising avenues for catalyst innovation.

Amorphous catalysts↗
DOE OSTI2023

Probing Molecular Packing of Amorphous Pharmaceutical Solids Using X-ray Atomic Pair Distribution Function and Solid-State NMR

The structural investigation of amorphous pharmaceuticals is of paramount importance in comprehending their physicochemical stability. However, it has remained a relatively underexplored realm primarily due to the limited availability of high-resolution analytical tools. Here in this study, we utilized the combined power of X-ray pair distribution functions (PDFs) and solid-state nuclear magnetic resonance (ssNMR) techniques to probe the molecular packing of amorphous posaconazole and its amorphous solid dispersion at the molecular level. Leveraging synchrotron X-ray PDF data and employing the empirical potential structure refinement (EPSR) methodology, we unraveled the existence of a rigid conformation and discerned short-range intermolecular C–F contacts within amorphous posaconazole. Encouragingly, our ssNMR 19 F– 13 C distance measurements offered corroborative evidence supporting these findings. Furthermore, employing principal component analysis on the X-ray PDF and ssNMR data sets enabled us to gain invaluable insights into the chemical nature of the intermolecular interactions governing the drug–polymer interplay. These outcomes not only furnish crucial structural insights facilitating the comprehension of the underlying mechanisms governing the physicochemical stability but also underscore the efficacy of synergistically harnessing X-ray PDF and ssNMR techniques, complemented by robust modeling strategies, to achieve a high-resolution exploration of amorphous structures.

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

Synergistic Evolution of Segmental Motion and Cooperative Relaxation within the Amorphous Phase of Organic Mixed Ionic-Electronic Conductors

Organic mixed ionic-electronic conductors (OMIECs) facilitate a variety of electrochemical processes and feature a heterogeneous microstructure composed of both crystalline and amorphous phases. However, structural evolution in amorphous regions during electrochemical doping remains poorly understood, limiting our understanding of mixed conduction mechanisms. Here, in this work, we develop operando chip calorimetry to probe amorphous phase evolution in poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) under swelling and electrochemical (de)­doping. Our results reveal that amorphous regions providing ionic transport pathways and those within electronic transport channels undergo heterogeneous, yet synergistic, evolution during electrochemical modulation. The cooperative interplay between segmental motion and relaxation maintains ionic conductivity and intergrain electronic transport upon electrowetting and doping, while facilitating efficient ion hopping and adaptable chain conformations during dedoping. Such synergies are more pronounced in loose structures featuring a fibrillar morphology, which exhibit lower glass transition temperatures (T g ) and higher fragility (m). High-throughput robotic screening further establishes a strong correlation between elevated m/T g ratios and enhanced mixed conduction. These findings elucidate the role of the amorphous phase in the synthesis of OMIECs and underscore the potential of operando chip calorimetry in uncovering structure–property relationships in electroactive polymers.

amorphous phase↗
DOE OSTI2018

Evolution of short- and medium-range order in the melt-quenching amorphization of Ge 2 Sb 2 Te 5

Phase-change memory takes advantage of the fast phase transition between amorphous and crystalline phases of phase-change materials (e.g.,Ge 2 Sb 2 Te 5 or GST). To date, while the “SET” process (crystallization of GST glass) has been intensively studied, studies on the “RESET” process (melt-quenching amorphization of GST) are still limited. Here, we explore the structural changes of GST upon rapid cooling by ab initio molecular dynamics simulations and atomistic cluster alignment (ACA) analysis. Different from other methods which only focus on the nearest bonding atoms, the ACA method can study both the short- and medium-range order clusters containing atoms beyond the first-neighboring shell and enables us to explore the changes of cluster structures in a larger scale. The results reveal that low-coordinated octahedral clusters tend to become high-coordinated ones, and Ge-centered octahedral structures change to tetrahedrons whereas Sb-centered tetrahedrons transform to octahedral structures during the amorphization process. Interestingly, tetrahedrons show aggregation in liquid and supercooled liquid in contrast to 6-fold octahedrons which present notable aggregation in amorphous GST. Furthermore, our study showed that wrong bonds (Ge–Ge, Sb–Sb, Ge–Sb and Te–Te bonds) can promote the formation of large rings, and irreducible rings tend to separate into smaller and larger rings as the temperature is decreased. Our conclusions provide useful insights into the formation process and the structure of amorphous GST, which is valuable for facilitating the application of phase change materials.

36 MATERIALS SCIENCE↗