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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Scalable Al 2 O 3 –TiO 2 Conductive Oxide Interfaces as Defect Reservoirs for Resistive Switching Devices

Abstract Resistive switching devices herald a transformative technology for memory and computation, offering considerable advantages in performance and energy efficiency. Here, a simple and scalable material system of conductive oxide interfaces is employed, and their unique properties are leveraged for a new type of resistive switching device. An Al 2 O 3 –TiO 2 ‐based valence‐change resistive switching device, where the conductive oxide interface serves both as the bottom electrode and as a reservoir of defects for switching, is demonstrated. The amorphous–polycrystalline Al 2 O 3 –TiO 2 conductive interface is obtained following the technological path of simplifying the fabrication of the 2D electron gases (2DEGs), making them scalable for practical mass integration. Physical analysis of the device chemistry and microstructure with comprehensive electrical analysis of its switching behavior and performance is combined. The origin of the resistive switching is pinpointed to the conductive oxide interface, which serves both as the bottom electrode and as a reservoir of oxygen vacancies. The latter plays a key role in valence‐change resistive switching devices. The new device, based on scalable and complementary metal–oxide–semiconductor (CMOS)‐technology‐compatible fabrication processes, opens new design spaces toward increased tunability and simplification of the device selection challenge.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Identifying the Catalytic Active Site for Propylene Metathesis by Supported ReO x Catalysts

A series of supported ReO x catalysts were investigated that allowed identifying the unique surface anchoring sites on oxide supports responsible for activating the surface ReO 4 sites for propylene metathesis (the catalytic active site). The catalysts were synthesized by incipient-wetness impregnation of aqueous HReO 4 onto the oxide supports (Al 2 O 3 , ZrO 2 , TiO 2 , SiO 2 and CeO 2 ), characterized under dehydrated and propylene metathesis reaction conditions with in situ spectroscopy (Raman, DRIFTS, UV-Vis and NAP-XPS), and chemically probed (CH 3 CH=CH 2 -TPSR, CH 2 =CH 2 /CH 3 CH=CHCH 3 titration and steady-state self-metathesis of propylene to ethylene and 2-butene). The initially calcined supported rhenia species anchor as isolated surface Re 7+ O 4 sites on the oxide supports by reacting with the surface hydroxyls (terminal S-OH, bridged S-OH-S and tricoordinated S 3 -OH) of the oxide supports. The specific oxide support was found to control the number of activated sites (Al 2 O 3 >> ZrO 2 > CeO 2 > TiO 2 > SiO 2 ) and propylene metathesis activity (Al 2 O 3 >> ZrO 2 >> TiO 2 ~ CeO 2 ~ SiO 2 ) revealing that the oxide support action is a potent ligand for the surface ReO x sites. The activation and specific activity of the surface ReO x sites depend on several factors (nature of surface hydroxyls (S 3 -OH > S-OH-S > S-OH), coordination of the oxide support surface cation (ZrO 7 , AlO 6 , CeO 4 ) and electronegativity of the oxide support cation (SiO 2 > Al 2 O 3 > TiO 2 > ZrO 2 > CeO 2 ). No relationships exist between olefin metathesis activity and acid strength of surface Lewis and Brønsted sites. Here, prior studies primarily focused on supported ReO x /Al 2 O 3 and the lack of examination of non-Al 2 O 3 supported rhenia catalysts precluded comparison between efficient and inefficient olefin metathesis catalysts, which prevented identifying the catalytic active site for olefin metathesis by supported ReO x catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Tailoring the Interfacial Interactions of Porous Polymer Membranes to Accelerate Atomic Layer Deposition: The Latent Path to Antifouling Membranes

Atomic layer deposition (ALD) is a powerful strategy to engineer hybrid organic-inorganic membranes with emergent functionalities. The combination of atomic-level thickness control, a wide materials palette, and unprecedented conformality allows the physiochemical properties (e.g., hydrophilicity) of mesoporous polymer membranes to be precisely tuned. The nucleation of ALD material growth on polymer surfaces relies on Lewis acid-base interactions and remains an overlooked motif with tremendous potential to accelerate ALD nucleation and growth. Strategies to enhance these interactions could enable desirable properties such as antifouling behavior to be imparted on inert polymer surfaces that lack the necessary functional groups for ALD nucleation. Here, in this study, we demonstrate that the reactivity of polyacrylonitrile (PAN) membranes toward ALD metal oxide (MO) precursors with Lewis acid characteristics is enhanced by introducing strong Lewis base functional groups (amidoxime: Am) on the PAN backbone (Am-PAN). The resulting Lewis acid-base interactions accelerate the MO nucleation in Am-PAN and reduce the number of deposition cycles required to achieve hydrophilicity compared with the untreated PAN membrane. Unveiling the reaction mechanism, in situ Fourier transform infrared (FTIR) spectroscopy measurements established enhanced interaction dynamics between the ALD MO precursors and the Am-PAN membrane, unlike the PAN membrane. Spectroscopic ellipsometry and thermogravimetric analysis measurements revealed higher MO loadings in Am-PAN membranes compared to PAN membranes for the same number of ALD cycles. We found that strong Lewis acid-base interactions accelerated the ALD for a range of materials including Al 2 O 3 , TiO 2 , SnO 2 , and ZnO. More broadly, our work demonstrates that tailoring metal-precursor-polymer interactions is a powerful strategy to accelerate and modulate the ALD. We used this design strategy to fabricate Al 2 O 3 -Am-PAN hybrid membranes that showed 2-fold higher antifouling capability compared to pristine PAN membranes prepared with an equivalent number of Al 2 O 3 ALD cycles. Our approach expands the scope of design options for fouling-resistant porous hybrid inorganic-organic membranes and may ultimately reduce the operational costs of water treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Vapor-phase grafting of a model aminosilane compound to Al 2 O 3 , ZnO, and TiO 2 surfaces prepared by atomic layer deposition

Atomic layer deposition (ALD) is a highly versatile surface functionalization technique that can conformally coat both planar and porous substrates. Here we use ALD metal oxide layers to establish a well-defined starting surface for vapor-phase surface organic modification. Vapor-phase (3-aminopropyl)triethoxysilane (APTES) surface silanization of ALD Al 2 O 3 , ZnO and TiO 2 surfaces were studied at 100 °C, 150 °C and 200 °C. In situ quartz crystal microbalance (QCM) and Fourier-transform infrared (FTIR) spectroscopy measurements, and ex situ atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) measurements showed uniform monolayer silane formation through self-limiting APTES reaction. We observed a higher surface density of grafted APTES species following silanization at 100 °C compared to 200 °C, and we attribute this to the temperature-dependent reactivity of the surface hydroxyls and changes in the mode of APTES reaction. The FTIR and XPS measurements revealed that APTES reacts with Al 2 O 3 and ZnO exclusively through metal siloxy bond formation. However, APTES reacts with TiO 2 through both siloxy bond formation and ammonium salt formation via the amine group.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Post-landing major element quantification using SuperCam laser induced breakdown spectroscopy

The SuperCam instrument on the Perseverance Mars 2020 rover uses a pulsed 1064 nm laser to ablate targets at a distance and conduct laser induced breakdown spectroscopy (LIBS) by analyzing the light from the resulting plasma. SuperCam LIBS spectra are preprocessed to remove ambient light, noise, and the continuum signal present in LIBS observations. Prior to quantification, spectra are masked to remove noisier spectrometer regions and spectra are normalized to minimize signal fluctuations and effects of target distance. In some cases, the spectra are also standardized or binned prior to quantification. To determine quantitative elemental compositions of diverse geologic materials at Jezero crater, Mars, we use a suite of 1198 laboratory spectra of 334 well-characterized reference samples. The samples were selected to span a wide range of compositions and include typical silicate rocks, pure minerals (e.g., silicates, sulfates, carbonates, oxides), more unusual compositions (e.g., Mn ore and sodalite), and replicates of the sintered SuperCam calibration targets (SCCTs) onboard the rover. For each major element (SiO 2 , TiO 2 , Al 2 O 3 , FeO T , MgO, CaO, Na 2 O, K 2 O), the database was subdivided into five “folds” with similar distributions of the element of interest. One fold was held out as an independent test set, and the remaining four folds were used to optimize multivariate regression models relating the spectrum to the composition. We considered a variety of models, and selected several for further investigation for each element, based primarily on the root mean squared error of prediction (RMSEP) on the test set, when analyzed at 3 m. In cases with several models of comparable performance at 3 m, we incorporated the SCCT performance at different distances to choose the preferred model. Shortly after landing on Mars and collecting initial spectra of geologic targets, we selected one model per element. Subsequently, with additional data from geologic targets, some models were revised to ensure results that are more consistent with geochemical constraints. The calibration discussed here is a snapshot of an ongoing effort to deliver the most accurate chemical compositions with SuperCam LIBS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Ultrathin Free-Standing Oxide Membranes for Electron and Photon Spectroscopy Studies of Solid–Gas and Solid–Liquid Interfaces

Free-standing ultrathin (~2 nm) films of several oxides (Al 2 O 3 ,TiO 2 , and others) have been developed, which are mechanically robust and transparent to electrons with E kin ≥ 200 eV and to photons. We demonstrate their applicability in environmental X-ray photoelectron and infrared spectroscopy for molecular level studies of solid-gas (≥1 bar) and solid-liquid interfaces. These films act as membranes closing a reaction cell and as substrates and electrodes for electrochemical reactions. The remarkable properties of such ultrathin oxides membranes enable atomic/molecular level studies of interfacial phenomena, such as corrosion, catalysis, electrochemical reactions, energy storage, geochemistry, and biology, in a broad range of environmental conditions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Materials and methods for improved pyrolysis processing

The present disclosure relates to a catalyst that includes a support that includes a metal oxide and a metal deposited on the support, where the metal oxide includes at least one of TiO 2 , Al 2 O 3 , SiO 2 , CeO 2 , and/or ZrO 2 , the metal includes at least one of Pt, Pd, Ru Rh, Ni, and/or Mo, the metal is in the form of a particle, and the metal is present on the support at a concentration between about 0.1 wt % and about 5.0 wt %.

Griffin, Michael Brandon↗
DOE OSTI2021

Temperature-Dependent Communication between Pt/Al 2 O 3 Catalysts and Anatase TiO 2 Dilutant: the Effects of Metal Migration and Carbon Transfer on the Reverse Water–Gas Shift Reaction

In heterogeneous catalysis, unexpected effects from the supposedly inert reactor dilutant are not rare, but related understanding is lacking and inconsistent. Here we report investigations of the impacts of the anatase TiO 2 dilutant on the reverse water-gas shift (rWGS) reaction over Pt/Al 2 O 3 catalysts. Combining detailed kinetic data with microscopic and spectroscopic results, we demonstrate that the catalyst-dilutant communication depends on temperature. At high temperature (400 °C), Pt migrate from Al 2 O 3 to TiO 2 , resulting in higher dispersion and activity, without changing reaction mechanisms. The Pt migration is general to catalysts of different Pt nuclearity and various oxide dilutants. In contrast, at low temperature (250 °C), carboxylic acids (in particular acetic acid) present in the ambient air and adsorbed on TiO 2 are transferred onto Al 2 O 3 in close contact, effectively blocking the formate rWGS pathway. As a result, the rWGS can only proceed through the carboxyl pathway, and hence is significantly slower. The acetate transfer affects catalysts of different Pt nuclearity and support, but is unique to anatase TiO 2 dilutant. As the acetate layer is slowly removed under H 2 or the rWGS stream, the activity recovers. This work elucidates the complicated communication between catalysts and dilutants, which has general implications in heterogeneous catalysis, and resolves inconsistency in related reports in the literature. Finally, the impacts that anatase TiO 2 dilution has on the rWGS also unveil mechanistic understanding that further confirms the two co-existing rWGS pathways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Alumina–Titania Nanolaminate Condensers for Hot Programmable Catalysis

Nanolaminates composed of thin alternating layers of Al2O 3 and TiO 2 (ATO) were engineered by using atomic layer deposition as the dielectric material for a Pt-on-carbon catalytic condenser. Investigation assessed synthesis parameters including the deposition temperature, Al 2 O 3 and TiO 2 layer thicknesses, total number of layers, and a capping Al 2 O 3 layer on the maximum charge accumulation in the Pt catalyst. The highest capacitance ATO configuration demonstrated a specific capacitance of ∼1200 nF/cm 2 with working voltages of ±5 V, enabling the storage of 4 × 10 13 electrons or holes per cm 2 at room temperature. The ATO devices exhibited enhanced capacitance at elevated temperatures of up to 400 °C, suggesting the suitability of these materials for high-temperature applications. Adsorption of carbon monoxide on the Pt/C-ATO device characterized by grazing incidence infrared spectroscopy showed changes in the surface binding energy of 13.1 ± 0.8 kJ/mol for an applied external voltage bias of ±1 V.

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

Effective medium approximation for the refractive index of stratified metal oxide composites synthesized by atomic layer deposition

Atomic layer deposition (ALD) is a unique method for synthesizing conformal layers with precise composition. It is especially useful for the synthesis of mixed metal oxides for functional materials. One application of interest is the use of ALD for tailoring the refractive index of coatings. In homogeneously distributed composites of metal oxides, the refractive properties can be approximated as the average of the indices of the components. This is known as an effective medium approximation (EMA) and can be used to design the macroscopic properties of composites. ALD produces layered, anisotropic films, so the validity of an EMA in describing these films is not clear. Here, we use optical simulations and experimental characterization of stratified composites of TiO 2 and Al 2 O 3 to study the application of an EMA to the transmission and reflection behavior of ALD-prepared mixed metal oxide thin films. We found that when the characteristic layer thickness is smaller than roughly 10 nm, the optical spectra of theoretical and experimental ALD films match the equivalent theoretical spectra for a material with a refractive index calculated from a simple, compositionally weighted EMA. Hence, this EMA could describe the transmission and reflectance spectra in ALD-derived TiO2–Al 2 O 3 nanolaminates when the films were sufficiently stratified even without thorough characterization of the real layers in the films. As a result, we demonstrated that ALD can be used to prepare effectively homogenous mixed metal oxide films with a predictable, tailorable refractive index of any value between those of the TiO 2 and Al 2 O 3 component materials.

42 ENGINEERING↗
DOE OSTI2021

Al 2 O 3 /TiO 2 coated separators: Roll-to-roll processing and implications for improved battery safety and performance

Heat generation is one of the major concerns with lithium-ion batteries (LIB) while charging them at higher currents, which could inadvertently impact the rate performance and reduce the safety of the cell. Polymer separator is one of the least thermal conductive components of a LIB. In addition, commercial separators for LIB are made from polyolefin membranes that tend to shrink and curl at higher temperatures due to their lower melting temperature (~130 °C). Developing separators with improved thermal stability and higher electrolyte uptake is essential for enhancing the safety as well as the performance of the LIB. In this work, a thin layer of ceramic coatings (Al 2 O 3 and TiO 2 ) is applied on propylene (PP) membrane to improve the thermal stability and electrolyte affinity without compromising the rate performance. A slurry with 100% Al 2 O 3 coated on the polypropylene separator exhibited the best improvement in thermal stability ( shrinkage of 0.6% vs 6.0% for uncoated membrane) and excellent rate performance with 92% capacity retention at 2C. The Al 2 O 3 coated separator demonstrated excellent electrolyte wettability compared to the uncoated membrane. The cross-plane thermal conductivity of the ceramic coated separators is analyzed to understand their heat transfer behavior. The thermal conductivity of the separator is improved by ~3.2 times with the Al 2 O 3 coating.

25 ENERGY STORAGE↗
DOE OSTI2024

Single-Atom Manganese-Based Catalysts for the Oxidative Dehydrogenation of Propane

Combinatorial screening of 150 supported metal oxide (manganese and additives) catalysts was carried out via a high-throughput synthesis platform and parallel reactors for the oxidative dehydrogenation (ODH) of propane to propylene. Specifically, an organomanganese (0.05-2.5 Mn atoms/nm 2 ) complex was grafted on metal oxide supports (Al 2 O 3 , SiO 2 , TiO 2 , and ZrO 2 ) premodified with either Lewis acid (Al, Ti, Zn, and Zr) or redox-active (Cu, Cr, Ga Ni, V) additives at various surface coverages (25, 50, and 75%). Catalysts were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and UV-vis spectroscopy. Catalysts 0.05 Mn/V(50%)/Al 2 O 3 and 0.05 Mn/Ni(50%)/ZrO 2 showed the highest combined propane conversion and propylene selectivities (31/41% and 15/85%), with excellent stability at 500 degrees C for 25 h. The presence of Ni in Mn/Ni/ZrO 2 resulted in a 6-fold increase in turnover frequency (TOF) over the Mn/ZrO 2 . HRTEM identified single Mn atoms after 500 degrees C heat treatment. For the Mn/Ni/ZrO 2 system, Mn was incorporated into the support lattice due to the similar ionic radius of Mn 2+ and Zr 4+ , which was also enhanced by the presence of Ni. For the Mn/V/Al 2 O 3 system, highly active MnO was prevalent as observed by Raman. Both V and Mn contributed to an increase in mutual dispersion, but both species remained on the surface. Finally, it is proposed that the highly dispersed atom and interactions between Mn with either Ni or V are responsible for the ODH performance and stability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Transformations of Ti-5Al-5V-5Cr-3Mo powder due to reuse in laser powder bed fusion: A surface analytical approach

Reactive Ti-5Al-5 V-5Cr-3Mo (Ti5553) alloy feedstock powder is used in laser powder-bed fusion (LPBF). Due to the large quantity of powder necessary for LPBF, powder is reused numerous times under oxidizing environments. Transformations to the powder’s native surface oxide may impact the LPBF process and lead to deviations from expected behavior of printed parts. In this work, we present a multimodal characterization of new and reused powder by combining X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and transmission electron microscopy (TEM) of focused ion beam (FIB)-prepared cross sections of individual powder particles to understand how the surface oxide composition changes, grows, and becomes hydroxylated and hydrated due to reuse. We show that the native oxide film of Ti5553 powder is a hydroxylated mixed oxide composed of TiO 2 and Al 2 O 3 that grows from 5.6 +/- 0.7 nm to 8.3 +/- 1.1 nm due to reuse. Al oxide regions of the surface oxide become more hydroxylated during reuse in comparison to Ti oxide regions. This indicates that an outer oxide of pure TiO 2 may enhance recyclability of Ti5553 powder while the presence of Al oxides may decrease recyclability. Further characterization of surface transformations due to recyclability may eliminate unnecessary variation in LPBF.

36 MATERIALS SCIENCE↗
DOE OSTI2020

First-principles predictions of temperature-dependent infrared dielectric function of polar materials by including four-phonon scattering and phonon frequency shift

Recently, first-principles calculations based on density functional theory have been widely used to predict the temperature-dependent infrared spectrum of polar materials, but the calculations are usually limited to the harmonic frequency (0 K) and three-phonon scattering damping for the zone-center infrared-active optical phonon modes, and fail to predict the high-temperature infrared optical properties of materials such as sapphire (α–Al 2 O 3 ), GaAs, TiO 2 , etc., due to the neglect of high-order phonon scattering damping and phonon frequency shift. In this work, we implemented first-principles calculations to predict the temperature-dependent infrared dielectric function of polar materials by including four-phonon scattering and phonon frequency shift. The temperature-dependent phonon damping by including three- and four-phonon scattering as well as the phonon frequency shift by including cubic and quartic anharmonicity and the thermal expansion effect are calculated based on anharmonic lattice dynamics method. The infrared dielectric function of α–Al 2 O 3 is parameterized, and then the temperature-dependent infrared optical reflectance is determined. We find that our predictions agree better with the experimental data than the previous density functional theory-based methods. Lastly, this work will help to effectively predict the thermal radiative properties of polar materials at elevated temperature, which is generally difficult to measure, and will enable predictive design of new materials for radiative applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Non-Oxidative Ethane Dehydrogenation in a Packed-Bed DBD Plasma Reactor

Abstract Plasma-assisted conversion of ethane (C 2 H 6 ) can produce value-added chemical building blocks using green electricity. Here we employ a simple packed-bed coaxial dielectric barrier discharge (DBD) reactor to convert C 2 H 6 at mild operating conditions unattainable by conventional thermocatalysis. Ethylene (C 2 H 4 ), acetylene (C 2 H 2 ), and methane (CH 4 ) are the main products along with small fractions of C 3 and C 4 hydrocarbons. Interestingly, the C 2 H 4 selectivity is primarily correlated to C 2 H 6 conversion, dominated by electron dissociation and recombination reactions irrespective of the dielectric properties of the packed bed material (SiO 2 , Al 2 O 3 , ZrO 2 , TiO 2 , and BaTiO 3 ), packing material size, supplied power, and C 2 H 6 concentration. While a distortion of the electric field and discharge propagation results in varying dissipated power as materials change, the C 2 H 4 energy yield remains constant. The particle size appears to affect conversion mainly due to pressure alterations. Pd/SiO 2 catalyst can change the selectivity, favoring saturated species by expending hydrogen.

Engineering↗
DOE OSTI2023

Chemical looping combustion oxygen carrier production cost study

The objective of this study was to estimate the cost of commercial production of oxygen carriers (OCs) for large-scale application in a mature, chemical looping combustion (CLC) power generation industry. Estimates of cost were made for two production facility scenarios: 1) build and operate an on-site, OC production facility located at a 550 MW CLC power plant site; and 2) build and operate a central production facility to produce and distribute OCs to the U.S. CLC power generation industry. Two OC production techniques were addressed: mechanical mixing and co-precipitation. Representative OCs that have production raw materials with sufficient commercial availability to support a CLC industry are ilmenite, a natural OC, and four engineered OC types, Fe 2 O 3 -based, CuO-based, NiO-based, and CuFeAlO 4 -based, with candidate OC support materials Al 2 O 3 and TiO 2 . The costs of the OC production raw materials represent the major portion of the OC product cost; the OC production cost, in dollars per kg, has been found to be nearly a linear function of the OC raw materials cost, in dollars per kg. In conclusion, the estimated OC product costs can be used to estimate the maximum OC loss rate yielding a designated CLC power plant cost-of-electricity (COE) target as a development guide, and it has been found that the maximum OC makeup rate, in kg per hour, achieving a designated COE reduction goal relative to a conventional pulverized coal (PC) power plant, will be nearly inversely proportional to the OC production raw materials cost, in dollars per kg.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗