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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Room‐Temperature Skyrmion Thermopower in Fe 3 Sn 2

Abstract We present the room‐temperature thermoelectric signature of skyrmion bubbles. This is observed in Fe 3 Sn 2 , a Kagome Dirac crystal with massive Dirac fermions that features a high‐temperature skyrmion phase. The room‐temperature skyrmion bubbles show magnetic‐field dependence of the wavevector whereas the thermopower is dominated by the electronic diffusion mechanism, allowing for the skyrmionic bubble detection. The results pave the way for future skyrmion‐based devices based on the manipulation of the thermal gradient.

Du, Qianheng↗
DOE OSTI2016

Instrument-Aided Assessment of the Effect of Natural and Technogenic Factors on the Geomechanical State of a Massif Enclosing an HPP Turbine Room

A package of geophysical criteria has been developed using seismic spatiotemporal tomography (SST) of a rock massif to perform an instrument-aided assessment of the effect of natural and technogenic factors on the geomechanical state of a rock massif enclosing an underground turbine room at an HPP. Results are presented for a detailed assessment for the underground turbine room at the Verkhnyaya Tuloma HPP on the Kola peninsula.

13 HYDRO ENERGY↗
DOE OSTI2018

Antiferromagnetic Ordering at Room Temperature in Co-Doped Sb{sub 2}Te{sub 3} Topological Insulators

Structural and magnetic properties of Co-doped Sb{sub 2}Te{sub 3} topological insulators have been investigated. Surface morphology was studied using scanning electron microscope (SEM) and atomic force microscope (AFM). X-ray photo electron spectroscopy (XPS) study reveals the mixed states of Co in Co{sup 2+} and Co{sup 3+}. Magnetic study indicates that the substitution of Co in Sb{sub 2}Te{sub 3} not only tune the materials from diamagnetic to antiferromagnetic (even at room temperature) but also propose a promising materials for antiferromagnetic TI which may be useful even for room temperature applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Tunable Optical Behaviour and Room Temperature Ferromagnetism of Cobalt-Doped BaSnO{sub 3} Nanostructures

In this work, the effect of Co doping on the structural, vibrational, morphological, optical and magnetic behaviour of BaSnO{sub 3} nanostructures is reported. Pure and Co (1,3, and 5%)-doped barium stannate (BSO) nanostructures were prepared by conventional hydrothermal technique followed by calcination at 900 °C for 5 h. The single crystalline cubic phase was identified by XRD analysis and structural distortions associated with Co doping were evidenced by variation in microstarin and crystallite size. FTIR and Raman studies further confirm the structural quality of the prepared samples. FESEM analysis revealed the mixed morphology of prepared samples, and the chemical compositions of all the samples were analysed using EDAX studies. The absorption studies revealed the incorporation of dopant ions and their effect on the bandgap subsequently in samples. The presence of defects and paramagnetic centres in the samples were confirmed by PL and EPR analyses. Magnetization studies demonstrated that pure BSO exhibits characteristic diamagnetism at room temperature and the addition of Co into Ba–Sn–O lattice drives the F-centre exchange interactions which results in the ferromagnetic behaviour. Hence, the occurrence of diamagnetic to ferromagnetic transition at room temperature with addition of Co as a dopant was identified.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Room Temperature Adsorptive Removal of Thiophene over Zinc Oxide-Based Adsorbents

This study investigated the room temperature adsorptive removal of thiophene over zinc oxide adsorbents in the presence of hydrogen. The bulk zinc oxide was prepared by precipitation method and calcined at different temperatures in the range of 300-550 °C. Supported zinc oxide was prepared by co-precipitation of 30 wt.% ZnO with alumina and calcined at 550 °C. Properties of the adsorbents were determined by various characterization techniques such as surface area and pore volume analysis, XRD, FESEM, EDX and TPR. The desulfurization process was carried out in a down-flow packed bed reactor at room temperature (30 °C). The BET surface area of bulk zinc oxide adsorbents decreased with the increase in calcination temperature from 300 to 550 °C. The surface area of bulk zinc oxide adsorbents was 30.5 and 14.6 m{sup 2}/g when calcined at 300 and 550 °C, respectively. The surface are of supported zinc oxide adsorbents was 177 m{sup 2}/g. The highest average pore size was obtained for bulk ZnO calcined at 550 °C (45 nm) compared to that calcined at 300 °C (42 nm) and supported ZnO (27 nm). The XRD peaks corresponded to the hexagonal structure of zinc oxide. The removal of thiophene was most significant for bulk ZnO calcined at 550 °C. The higher removal efficiency for this adsorbent in spite of lower surface area may be attributed to its higher percentage of larger pores and higher average pore size.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Constitutive Behavior and Forming Limit of Mg-Al-Ca-Gd Alloy Sheets at Room and Elevated Temperatures

The constitutive behavior and forming limit of a newly developed magnesium alloy sheet containing rare earth elements (Mg-Al-Ca-Gd) were investigated. Anisotropic constitutive constants were obtained through tensile tests at various temperatures and strain rates. A modified Grosman equation was adopted to describe the constitutive behavior of the magnesium alloy, taking into account the effects of temperature and strain rate. Results revealed that the proper forming temperature and the strain rate for the newly developed magnesium alloy were 210 °C and 0.001 s{sup −1}, respectively. Forming limit curves at room temperature and 210 °C were, respectively, established by the combination of hemispherical punch tests and theoretical predictions using a modified Marciniak–Kuczynski model. The accuracy of the theoretical prediction of FLD was discussed. The forming limit of Mg-Al-Ca-Gd alloy sheet increased when heated from room temperature to 210 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Simultaneous Detection and Removal of Formaldehyde at Room Temperature: Janus Au@ZnO@ZIF-8 Nanoparticles

The detection and removal of volatile organic compounds (VOCs) are of great importance to reduce the risk of indoor air quality concerns. Our study reports the rational synthesis of a dual-functional Janus nanostructure and its feasibility for simultaneous detection and removal of VOCs. The Janus nanostructure was synthesized via an anisotropic growth method, composed of plasmonic nanoparticles, semiconductors, and metal organic frameworks (e.g., Au@ZnO@ZIF-8). It exhibits excellent selective detection to formaldehyde (HCHO, as a representative VOC) at room temperature over a wide range of concentrations (from0.25 to 100 ppm), even in the presence of water and toluene molecules as interferences. Additionally, HCHOwas also found to be partially oxidized into non-toxic formic acid simultaneously with detection. The mechanism underlying this technology was unraveled by both experimental measurements and theoretical calculations: ZnO maintains the conductivity, while ZIF-8 improves the selective gas adsorption; the plasmonic effect of Au nanorods enhances the visible-light-driven photocatalysis of ZnO at room temperature.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Decoding anomalous grain growth at room temperature during pressure-induced phase transformations

Significant grain growth is observed during the high-pressure phase transformations (PTs) at room temperature in various materials. The main focus here is grain growth from a few hundred nanometers to 10 μm within an hour during α → ω PT in Zr. No existing theory explains this phenomenon since without PT, Zr nanocrystals do not grow at room temperature even for up to 10 years. Here, in this study, a multistep mechanism for the grain growth during α → ω PT in Zr is suggested. Phase interfaces (PI) and grain boundaries (GBs) coincide and move together as a combined PI-GBs under the action of the combined thermodynamic driving force. Such a combined motion changes the diffusional grain growth mechanism to the transformational one and the martensitic mechanism of PT to a reconstructive one via an intermediate disordered phase. The primary condition is that the GB energy of the ω phase is smaller than that of the α phase, which promotes the nucleation of ω-Zr and is consistent with the absence of the reverse PT and reduction in the PT pressure with reducing grain size. Several intermediate steps for such motion are suggested and justified kinetically. Nonhydrostatic stresses due to volume reduction in the growing ω grain promote continuous growth of the existing ω grain instead of a new nucleation at other GBs. In situ synchrotron Laue diffraction experiments confirm the main predictions of the theory. The suggested mechanism provides a new insight into synergistic interaction between PTs and microstructure evolution.

anomalous grain growth during phase transformation↗
DOE OSTI2022

Ambient pressure X-ray photoelectron spectroscopy study of room-temperature oxygen adsorption on Cu(1 0 0) and Cu(1 1 1)

We investigated the room-temperature chemisorption of oxygen on Cu(1 0 0) and Cu(1 1 1) using ambient-pressure X-ray photoelectron spectroscopy (APXPS). A shoulder-to-shoulder comparison between the oxygen-gas titration on the two surfaces reveals that Cu(1 0 0) is the more active for oxygen dissociative chemisorption when the surfaces are clean. The (2 $\sqrt{2}$ × $\sqrt{2}$)R45o missing-row reconstruction appears in Cu(1 0 0)’s LEED image after about 10 4 Langmuir of oxygen exposure, whereas on Cu(1 1 1), no long-range ordering was observed throughout the whole experiment. An oxide layer consisting of cuprous and cupric oxide shows up on Cu(1 1 1) at an oxygen exposure that is significantly lower than for Cu(1 0 0). This observation suggests that the presence of (2 $\sqrt{2}$ × $\sqrt{2}$)R45o missing-row reconstruction layer slows down Cu(1 0 0) oxidation. Literature has widely reported that surface morphology influences the copper oxidation process. This study provides an XPS demonstration that copper surface oxide formation in O 2 at room temperature depends on the surface crystallographic orientation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Coupling AFEX and steam-exploded sugarcane residue pellets with a room temperature CIIII-activation step lowered enzyme dosage requirements for sugar conversion

In this study, the potential integration of steam explosion (StEx) and ammonia fiber expansion (AFEX) with existing sugar/ethanol mills to form decentralized pre-processing depots was explored. Both StEx and AFEX pretreatment facilitated the production of sugarcane bagasse (SCB) and cane leaf matter (CLM) pellets with significantly higher bulk density, mechanical durability, and hydrophobicity relative to their untreated biomass pellet controls. However, ethanol production from standalone StEx and AFEX-treated SCB and CLM pellets required enzyme dosages greater than 21 mg/g glucan to achieve enzymatic hydrolysis sugar yields of 75% and ethanol titres greater than 40 g.L -1 . Coupling AFEX-treated SCB or CLM pellets with a room temperature CIII I -activation step using liquid ammonia lowered enzyme dosage requirements by more than 50% without affecting ethanol titers and production yields (greater than300 L per Mg residual dry matter raw dry biomass (RDM)). In contrast, treating StEx-treated pellets with CIIII-activation using liquid ammonia did not result in similar enzyme dosage reductions, due to pseudo-lignin formation, leading to enzyme deactivation and/or lignin blockage that retarded enzymatic hydrolysis at low enzyme dosages. A gross energy conversion assessment revealed that low enzyme dosage (3-4 mg enzyme/g RDM) ethanol and electricity co-production from AFEX and CIII I -activated SCB and CLM can recover up to 73% of the energy in the untreated biomass, compared to 54% recovered by StEx and CIII I -activation. The results from this work suggest that StEx or AFEX based pre-processing depots can produce dense and mechanically durable biomass pellets. The AFEX-treated pellets can be easily upgraded using a room temperature CIII I -activation step at the biorefinery to significantly reduce bioconversion enzymes.

42 ENGINEERING↗
DOE OSTI2022

Room temperature slot-die coated perovskite layer modified with sulfonyl-γ-AApeptide for high performance perovskite solar devices

Perovskite solar cells (PSCs) exhibited remarkable progress for small aperture area cells, however, the performance of its counterpart, large aperture area cells, lags due to non-uniform and defective perovskite layers. Here, we fabricate reproducible large area homogeneous perovskite films at room temperature and without controlling humidity (up to 40 % RH) with a slot die coater on a c-TiO 2 layer deposited using a large area chemical bath. A new artificial peptide – sulfonyl-γ-AApeptide (F-GLU-S) was employed to modify the slot-die coated perovskite surface, grain boundaries and electronic defects. The multi-functional F-GLU-S with carbonyl, carboxyl, sulfonyl, benzene, and chloro groups was capable of strongly interacting with the perovskite layer and repairing the uncoordinated Pb 2+ ions and halide vacancies. As a result, both the electron and hole densities of defects were significantly suppressed; consequently, the non-radiative recombination was effectively suppressed for the modified device which can be explicitly seen in the device performance where both V oc and FF of the modified device improved considerably. Therefore, F-GLU-S modified slot-die coated MAPbI 3 – based devices demonstrated outstanding performance of 21.44 % PCE with a V oc of 1.13 V, J sc of 24.64 cm –2 , and FF 76.99 %. Furthermore, F-GLU-S passivation impeded the infiltration of moisture and oxygen due to its hydrophobic nature and defect repair potential. As a result, the modified device retained above 92 % of its original PCE after 720 h in air (room temperature and 40–60 % RH).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Room-temperature MBE deposition, thermoelectric properties, and advanced structural characterization of binary Bi[subscript 2]Te[subscript 3] and Sb[subscript 2]Te[subscript 3] thin films

Sb{sub 2}Te{sub 3} and Bi{sub 2}Te{sub 3} thin films were grown at room temperature on SiO{sub 2} and BaF{sub 2} substrates using molecular beam epitaxy. A layer-by-layer growth was achieved such that metallic layers of the elements with 0.2 nm thickness were deposited. The layer structure in the as-deposited films was confirmed by X-ray diffraction and was seen more clearly in Sb{sub 2}Te{sub 3} thin films. Subsequent annealing was done at 250 C for 2 h and produced the Sb{sub 2}Te{sub 3} and Bi{sub 2}Te{sub 3} crystal structure as confirmed by high-energy X-ray diffraction. This preparation process is referred to as nano-alloying and it was demonstrated to yield single-phase thin films of these compounds. In the thin films a significant texture could be identified with the crystal c axis being almost parallel to the growth direction for Sb{sub 2}Te{sub 3} and tilted by about 30{sup o} for Bi{sub 2}Te{sub 3} thin films. In-plane transport properties were measured for the annealed films at room temperature. Both films yielded a charge carrier density of about 2.6 x 10{sup 19} cm{sup -3}. The Sb{sub 2}Te{sub 3} films were p-type, had a thermopower of +130 {micro}V K{sup -1}, and surprisingly high mobilities of 402 cm{sup 2} V{sup -1} s{sup -1}. The Bi{sub 2}Te{sub 3} films were n-type, showed a thermopower of -153 {micro}V K{sup -1}, and yielded significantly smaller mobilities of 80 cm2 V{sup -1} s{sup -1}. The chemical composition and microstructure of the films were investigated by transmission electron microscopy (TEM) on cross sections of the thin films. The grain sizes were about 500 nm for the Sb{sub 2}Te{sub 3} and 250 nm for the Bi{sub 2}Te{sub 3} films. In the Bi{sub 2}Te{sub 3} thin film, energy-filtered TEM allowed to image a Bi-rich grain boundary phase, several nanometers thick. This secondary phase explains the poor mobilities of the Bi{sub 2}Te{sub 3} thin film. With these results the high potential of the nano-alloying deposition technique for growing films with a more complex layer architecture is demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Pd-promoted reduction and restructuring of an In 2 O 3 -based catalyst for CO 2 hydrogenation at room temperature

An unconventional reaction mechanism in an In 2 O 3 /Pd(1 1 1) inverse model catalyst for the CO 2 hydrogenation reaction has been uncovered: In 2 O 3 is partially reduced at room temperature in a reaction atmosphere as a result of its direct contact with Pd(1 1 1), which is an efficient H 2 splitter. The reduction induces changes in surface free energy, leading to a dynamical restructuring at the In 2 O 3 /Pd(1 1 1) interface via formation of InO x and outward diffusion of Pd, as revealed by ambient pressure X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and density functional theory simulations. This dynamical restructuring eventually promotes the growth of 2D InPd y O x nanodomains as the catalytically active phase and the exclusive formation of methanol upon hydrogenation of CO 2 at room temperature. A comparable high selectivity toward CH 3 OH was found in more realistic bulk catalytic systems (2 wt% Pd/In 2 O 3 catalyst and commercial CZA catalyst). Scanning tunneling microscopy under ultrahigh vacuum and ambient pressure reaction atmospheres further reveals the structural dynamics at the InO x /Pd(1 1 1) interface, where we follow in situ the evolution of the InO x particles on Pd(1 1 1) and the mobility of the InPd y O x nanodomains in a CO 2 + H 2 environment. The present findings of the formation of a mixed oxide phase in a dynamically restructuring metal/reducible-oxide interface indicate further implications for other heterogeneous catalytic systems beyond the present CO 2 hydrogenation example and highlight the importance of in situ investigations.

36 MATERIALS SCIENCE↗
DOE OSTI2023

High-resolution absorption spectroscopy of room-temperature and jet-cooled ammonia between 59,000 and 93,000 cm -1

Here, we present new high-resolution photoabsorption spectra of ammonia spanning the region between 59,000 cm -1 and 93,000 cm -1 that were recorded by using the Fourier Transform Spectrometer at the Synchrotron SOLEIL. This region extends from just above the Franck-Condon envelope for the $\tilde{A}$ 1 $A$ 2 " ← $\tilde{X}$ 1 $A$ 1 ' transition to well above the NH 3 + $\tilde{X}$ + 2 $A$ 2 " ionization threshold. The spectra were recorded at a measured resolution of 0.23 cm -1 in both a room-temperature cell (293 K) and in a slit-jet supersonic expansion (~70 K). The absolute photoabsorption cross section with an uncertainty of ±5% is also reported for the room-temperature spectrum. The present resolution is a factor of 10 – 100 times higher than in other recently reported broad band spectra of ammonia, and many of the observed bands show partially resolved rotational structure. We have attempted to assign this structure for a number of these bands. The oscillator strengths extracted from the data are in good agreement with previous measurements but, in the case of structured bands, the present higher resolution measurements return higher peak absorption cross sections, that increase further when the sample is cooled. The present higher resolution spectra suggest that a number of previous vibronic band assignments that were based on quantum defect considerations may require some revision. Finally, we discuss the substantial differences between the photoabsorption and photoionization data just above the first ionization threshold.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Thermal properties measurement of TRISO particle coatings from room temperature to 900 °C using laser-based thermoreflectance methods

The thermal properties of tristructural isotropic (TRISO) particle coatings have been measured using laser-based thermoreflectance methods from room temperature to 900 °C. At room temperature the pyrocarbon coatings have comparable thermal conductivities below 10 W·m -1 ·K -1 , whereas the SiC coating has a thermal conductivity around 90 W·m -1 ·K -1 . The thermal diffusivities of all coatings display significant reduction with increasing temperature. Finally, the thermal conductivity of SiC decreases by more than 25% above 800 °C and the thermal conductivities of pyrocarbons increase moderately with the temperature, displaying similar changes to that of amorphous graphite at elevated temperatures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Operando NMR and XRD study of chemically synthesized LiCx oxidation in a dry room environment

We test the stability of pre-lithiated graphite anodes for Li-ion batteries in a dry room battery processing room. The reaction between LiCx and laboratory air was followed using operando NMR and x-ray diffraction as these methods are sensitive to change in Li stoichiometry in graphite. There is minimal reactivity between LiC 6 and N 2 , CO 2 or O 2 ; however, LiC 6 reacts with moisture to form lithium (hydr)oxide. The reaction rate follows zero-order kinetics with respects to intercalated lithium suggesting that lithium transport through the graphite is fast. The reaction mechanism occurs by sequential formation of higher stages LiC 12 , then LiC 18 , and then LiC 24 as the hydrolysis proceeds to the formation of Li x OH y and graphite end products. Slowing down the formation rate of the Li x OH y passivation layer stabilizes of the higher stages.

25 ENERGY STORAGE↗
DOE OSTI2018

Elimination of active species crossover in a room temperature, neutral pH, aqueous flow battery using a ceramic NaSICON membrane

Flow batteries are an attractive technology for energy storage of grid-scale renewables. However, performance issues related to ion-exchange membrane (IEM) fouling and crossover of species have limited the success of flow batteries. In this work we propose the use of the solid-state sodium-ion conductor NaSICON as an IEM to fully eliminate active species crossover in room temperature, aqueous, neutral pH flow batteries. We measure the room temperature conductivity of NaSICON at 2.83–4.67 mS cm –1 and demonstrate stability of NaSICON in an aqueous electrolyte with conductivity values remaining near 2.5 mS cm –1 after 66 days of exposure. Charge and discharge of a full H-cell battery as well as symmetric cycling in a flow battery configuration using NaSICON as an IEM in both cases demonstrates the capability of the solid-state IEM. Extensive analysis of aged cells through electrochemical impedance spectroscopy (EIS) and UV–vis spectroscopy show no contaminant species having crossed over the NaSICON membrane after 83 days of exposure, yielding an upper limit to the permeability of NaSICON of 4 × 10 –10 cm 2 min –1 . As a result, the demonstration of NaSICON as an IEM enables a wide new range of chemistries for application to flow batteries that would previously be impeded by species crossover and associated degradation.

25 ENERGY STORAGE↗
DOE OSTI2012

Synthesis of manganese spinel nanoparticles at room temperature by coprecipitation

This paper is focused on a new route to synthesize Mn{sub 3}O{sub 4} nanoparticles by alkalisation by sodium hydroxide on a manganeous solution at room temperature. The precipitates obtained at different pH values have been characterized by XRD and TEM. Since the first addition of sodium hydroxide, a white Mn(OH){sub 2} precipitate appears. At pH=7, {gamma}-MnOOH phase is predominant with needle like shaped particles. At pH=10, hausmanite nanoparticles, which exhibits well defined cubic shape in the range 50-120 nm are obtained. This new precipitation route is a fast and easy environmentally friendly process to obtain well crystallized hausmanite nanoparticles. - Graphical abstract: TEM image showing Mn{sub 3}O{sub 4} particles after a precipitation at pH=10. Highlights: Black-Right-Pointing-Pointer A new route to synthesize Mn{sub 3}O{sub 4} nanoparticles has been demonstrated. Black-Right-Pointing-Pointer Synthesis has been performed by precipitation at room temperature. Black-Right-Pointing-Pointer The size of the Mn{sub 3}O{sub 4} nanoparticles is between 50 and 120 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗