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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Absorbable-susceptor joining of ceramic surfaces

An assembly of ceramic surfaces particularly refractory metal oxides and carbides, abutting a thin sheet of metal susceptor material are placed in a chamber of an enclosure containing inert gas. An RF coil is activated by power supply to melt the susceptor and adjacent zones of the ceramic. Reactive gas such as oxygen or a carbonizing gas is then fed to the chamber and reacts with the susceptor to form compounds which disperse and dissolve in the zones. On cooling, a strong joint is formed. The susceptor may contain inner perforations and outer perforations to aid in distribution of heat.

Schroeder, J. E.↗
NASA NTRS1986

Overcash, D. R.

The objectives of this investigation were to determine the characteristics of semiconductor devices at low temperatures. The output characteristics of several currently available semiconductor devices and devices fabricated at Marshall Space Flight Center were measured over a range of gate voltages. Large variations in low-temperature performance, not only from type to type, but from field effect transistor (FET) to FET of the same type were obtained. By increasing the carrier concentrations at low temperatures through extra heavy doping, metal oxide semiconductor field effect transistor (MOSFET) device was fabricated that operated at 4.2K. To verify the low-temperature operation of a heavily doped device, this procedure was repeated. Their noise spectrum was analyzed at 4.2K. Suggestions were made as to possible fabrication methods, techniques, and other semiconductor materials that might improve the device charactersitics at low temperatures. A procedure for using an electric field to drift dopants through the insulating oxide to produce a very thin, heavily doped region under the gate of a MOSFET was initiated. Capacitance s a function of voltage plots was suggested as a method for determining the level of dopant drift.

Source record↗
NASA NTRS1987

Protective Coatings for Spacecraft Polymers

Thin films of metal-oxide/polymer applied by ion-beam sputtering. Report describes experiments in development of coatings to protect polymers from bombardment by atomic oxygen.

Banks, Bruce A.↗
NASA NTRS1988

Long-lived thermal control materials for high temperature and deep space applications

Considerable effort has been put into developing thermal-control materials for the Galileo space-craft. This paper presents a summary of these findings to date with emphasis on requirements, testing and results for the post-Challenger Galileo mission. Polyimide film (Kapton), due to its inherent stability in vacuum, UV, and radiation environments, combined with good mechanical properties over a large temperature range, has been the preferred substrate for spacecraft thermal control materials. Composite outer layers, using Kapton substrates, can be fabricated to meet the requirements of severe space environments. Included in the processing of Kapton-based composite outer layers can be the deposition of metal oxide, metallic and/or polymeric thin-film coatings to provide desirable electrical, optical and thermo-optical properties. In addition, reinforcement of Kapton substrates with fabrics and films is done to improve mechanical properties. Also these substrates can be filled with varying amounts of carbon to achieve particular electrical properties. The investigation and material development reported on here has led to improved thermo-gravimetric stability, surface conductivity, RF transparency, radiation and UV stability, flammability and handle-ability of outer layer thermal control materials for deep space and near-sun spacecraft. Designing, testing, and qualifying composite thermal-control film materials to meet the requirements of the Galileo spacecraft is the scope of this paper.

Whitt, Robin↗
NASA NTRS1991

Precautions toward XTEM of Si3N4/SiO2

Severe difficulties are encountered in the preparation of oxidized Si3N4 specimens for XTEM transmission electromicroscopic inspection, in virtue of the extreme difference between Si3N4 and SiO2 mechanical properties. Attention is presently given to a preparation method in which an overlayer of the nitride is always occluded; this protects the oxide through most of the thinning that specimen preparation entails. An XTEM image of the oxide/nitride interface is presented.

Ogbuji, Linus U. J. T.↗
NASA NTRS1991

Oxygen plasma ashing effects on aluminum and titanium space protective coatings

Using variable angle spectroscopic ellipsometry and atomic force microscopy (AFM), the surface roughness and oxidation of aluminum and titanium thin films have been studied as a function of substrate deposition temperature and oxygen plasma exposure. Increasing substrate deposition temperatures affect film microstructure by greatly increasing grain size. Short exposures to an oxygen plasma environment produce sharp spikes rising rapidly above the surface as seen by AFM. Ellipsometric measurements were made over a wide range of plasma exposure times, and results at longer exposure times suggest that the surface is greater than 30% void. This is qualitatively verified by the AFM images.

Synowicki, R.↗
NASA NTRS2004

Precipitation of Secondary Phases from the Dissolution of Silicate Glasses

Basaltic and anorthositic glasses were subjected to aqueous weathering conditions in the laboratory where the variables were pH, temperature, glass composition, solution composition, and time. Leached layers formed at the surfaces of glasses followed by the precipitation of X-ray amorphous iron and titanium oxides in acidic and neutral solutions at 25 C over time. Glass under oxidative hydrothermal treatments at 150 C yielded a three-layered surface; which included an outer smectite layer, a Fe-Ti oxide layer and an innermost thin leached layer. The introduction of Mg into solutions facilitated the formation of phyllosilicates. Aqueous hydrothermal treatment of anorthositic glasses (high Ca, low Ti) at 200 C readily formed smectite, whereas, the basaltic glasses (high Ti) were more resistant to alteration and smectite was not observed. Alkaline hydrothermal treatment at 2000e produced zeolites and smectites; only smectites formed at 200 C in neutral solutions. These mineralogical changes, although observed under controlled conditions, have direct applications in interpreting planetary (e.g., meteorite parent bodies) and terrestrial aqueous alteration processes.

Ming, Douglas W.↗
NASA NTRS2012

In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

Nesbitt, James A.↗
DOE OSTI2024

Silicon-carbide-on-insulator via photoelectrochemical etching

Silicon carbide on insulator is provided by bonding bulk silicon carbide to a substrate with an oxide-oxide fusion bond, followed by thinning the bulk silicon carbide as needed. A doping-selective etch for silicon carbide is used to improve thickness uniformity of the silicon carbide layer(s).

Lukin, Daniil M.↗
DOE OSTI2023

Engineering of niobium surfaces through accelerated neutral atom beam technology for quantum applications

A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLSs). Native oxides present on the surfaces of superconducting metals used in quantum devices are acknowledged to be a source of TLS that decrease qubit coherence times. Reducing microwave loss by “surface engineering” (i.e., replacing the uncontrolled native oxide of superconducting metals with a thin, stable surface with predictable characteristics) can be a key enabler for pushing performance forward with devices of higher intrinsic quality factor. In this work, we present a novel approach to replace the native oxide of niobium (typically formed in an uncontrolled fashion when its pristine surface is exposed to air) with an engineered oxide, using a room-temperature process that leverages accelerated neutral atom beam (ANAB) technology at 300 mm wafer scale. This ANAB is composed of a mixture of argon and oxygen, with tunable energy per atom, which is rastered across the wafer surface. The ANAB-engineered Nb-oxide thickness was found to vary from 2 to 6 nm depending on ANAB process parameters. The modeling of variable-energy x-ray photoelectron spectroscopy data confirms the thickness and compositional control of Nb surface oxide by the ANAB process. Furthermore, these results correlate well with those from transmission electron microscopy and x-ray reflectometry. Since ANAB is broadly applicable to material surfaces, the present study indicates its promise for modification of the surfaces of superconducting quantum circuits to achieve longer coherence times.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Organic-semiconducting hybrid solar cell

The embodiment of this invention lies on experimental evidence of photoconductivity activity of a hybrid solar cell, organic/chalcogenide. The device is made of thin layers of conductive indium-tin-oxide (ITO) on glass with a 100 nm layer of chalcogenide molybdenum di-sulfide (MoS 2 ) and a thin layer of about ˜50 nm of complex organic compound assembled at room temperature. The device was tested to conventional electrical transport measurements in the regime of −1V to 1V under electromagnetic radiation simulator at 100 mW/cm 2 . Results indicate solar conversion efficiency of 2.48% and current density of 6.35 mA/cm 2 .

14 SOLAR ENERGY↗
DOE OSTI2022

Atomic layer deposition of lithium zirconium oxides for the improved performance of lithium-ion batteries

Recently there has been increasing interest to develop lithium-containing films as solid-state electrolytes or surface coatings for lithium-ion batteries (LIBs) and related systems. Here, in this study, we for the first time investigated the thin film growth of lithium zirconium oxides (Li x Zr y O or LZOs) through combining two individual atomic layer deposition (ALD) processes of ZrO 2 and LiOH, i.e., sub-ALD of ZrO 2 and LiOH. We revealed that the hygroscopic nature of the LiOH component has a big impact on the growth of LZOs. We found that an increased temperature to 225 °C was more effective than an elongated purge to mitigate the adverse effects of physisorbed H 2 O. We further discovered that, during the resultant LZO super-ALD processes, the growth of sub-ALD LiOH has been promoted while the growth of sub-ALD ZrO 2 has been inhibited. In this study, a suite of instruments has been applied to characterize the LZO super-ALD processes and the resultant LZO films, including in situ quartz crystal microbalance (QCM), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), atomic force microscopy (AFM), synchrotron-based X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, we applied the resulting LZO films over LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) cathodes in LIBs and demonstrated that the LZO coating films could evidently improve the lithium-ion insertion and extraction rates of the NMC622 electrodes up to 3.4 and 2.6 times, respectively. The LZO-coated NMC622 cathodes exhibited much better performance than the uncoated NMC622 ones.

36 MATERIALS SCIENCE↗
NASA NTRS1988

RF surface resistance of YBa2Cu3O(7-x) thin films

The excitement engendered by the discovery of the new T sub c oxide superconductors has led to much speculation about practical applications of thin films of these materials in digital and analog electronic devices. Most of these envisioned applications involve high frequency signals for which a detailed knowledge of the surface impedance of the novel superconductors is very important. We have measured the surface resistance of thin films of YBaCuO in the frequency range 0.5 less than f less than 17 GHz using a stripline-resonator method. The stripline procedure also was used to measure the surface resistance of high quality gold and aluminum films; the resistance values obtained agree with values predicted from the measured dc resistance using the Pippard formalism for the anomalous skin effect. The YBaCuO were produced by a multilayer deposition process. The films are formed by e-beam evaporation of 24 layers of Y, Ba, and Cu. Films with the highest transition temperature were obtained using yttria-stabilized zirconia (YSZ) substrates. After deposition, the films are transferred to a furnace where they are annealed in flowing O2 at 850 C for 2h. The furnace then is turned off and allowed to cool to 100 C in about 16 h. Auger profiling of the films made by this process shows that the concentrations of Y, Ba, Cu, and O are uniform to within 1 percent throughout the thickness of the film.

Source record↗
DOE OSTI2022

Direct utilization of gaseous fuels in metal supported solid oxide fuel cells

Direct utilization and internal reforming of gaseous fuels is investigated on symmetric-architecture metal supported solid oxide fuel cells (MS-SOFCs) with thin ceramic electrolyte and scaffold backbone layers, and low cost ferritic stainless steel supports on both sides. Infiltrated Pr-oxide and Ni/samarium-doped ceria catalysts are added to the cathode and anode electrodes, respectively. Initial performance and durability is evaluated for MS-SOFCs operating with natural gas, propane, ammonia, and dimethyl ether at 700 °C. Cells for natural gas and propane utilize a novel high entropy alloy (HEA) catalyst for internal reforming with performance and degradation rates similar to H 2 (0.5W cm -2 and ~12%/100 h). In conclusion, initial testing with sulfur shows reversible degradation for levels found in natural gas and irreversible degradation for higher levels found in commercial propane. Overall, MS-SOFCs show successful fuel flexibility.

08 HYDROGEN↗
DOE OSTI2020

Nano-engineering the material structure of preferentially oriented nano-graphitic carbon for making high-performance electrochemical micro-sensors

Direct synthesis of thin-film carbon nanomaterials on oxide-coated silicon substrates provides a viable pathway for building a dense array of miniaturized (micron-scale) electrochemical sensors with high performance. However, material synthesis generally involves many parameters, making material engineering based on trial and error highly inefficient. Here, we report a two-pronged strategy for producing engineered thin-film carbon nanomaterials that have a nano-graphitic structure. First, we introduce a variant of the metal-induced graphitization technique that generates micron-scale islands of nano-graphitic carbon materials directly on oxide-coated silicon substrates. A novel feature of our material synthesis is that, through substrate engineering, the orientation of graphitic planes within the film aligns preferentially with the silicon substrate. This feature allows us to use the Raman spectroscopy for quantifying structural properties of the sensor surface, where the electrochemical processes occur. Second, we find phenomenological models for predicting the amplitudes of the redox current and the sensor capacitance from the material structure, quantified by Raman. Our results indicate that the key to achieving high-performance micro-sensors from nano-graphitic carbon is to increase both the density of point defects and the size of the graphitic crystallites. Our study offers a viable strategy for building planar electrochemical micro-sensors with high-performance.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Unraveling the Stable Cathode Electrolyte Interface in all Solid‐State Thin‐Film Battery Operating at 5 V

Abstract Spinel‐type LiNi 0.5 Mn 1.5 O 4 (LNMO) is one of the most promising 5 V‐class cathode materials for Li‐ion batteries that can achieve high energy density and low production costs. However, in liquid electrolyte cells, the high voltage causes continuous cell degradation through the oxidative decomposition of carbonate‐based liquid electrolytes. In contrast, some solid‐state electrolytes have a wide electrochemical stability range and can withstand the required oxidative potential. In this work, a thin‐film battery consisting of an LNMO cathode with a solid lithium phosphorus oxynitride (LiPON) electrolyte is tested and their interface before and after cycling is characterized. With Li metal as the anode, this system can deliver stable performance for 600 cycles with an average Coulombic efficiency >99%. Neutron depth profiling indicates a slight overlithiated layer at the interface prior to cycling, a result that is consistent with the excess charge capacity measured during the first cycle. Cryogenic electron microscopy further reveals intimate contact between LNMO and LiPON without noticeable structure and chemical composition evolution after extended cycling, demonstrating the superior stability of LiPON against a high voltage cathode. Consequently, design guidelines are proposed for interface engineering that can accelerate the commercialization of a high voltage cell with solid or liquid electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2021

Effect of capping layers on the near-surface region of SrVO 3 films

Surfaces of correlated-electron oxides are of significant interest both from fundamental and applied perspectives. Many such oxides feature a near-surface region (NSR) which differs from the bulk’s properties. The NSR can significantly affect the interpretation of the material’s electronic structure, especially for those in thin film form, and have detrimental effects for applications such as field effect devices and catalysts. In this work we study the changes in the composition and electronic structure of the NSR of SrVO 3 (SVO) thin films. We employ x-ray photoelectron spectroscopy (XPS) and compare TiOx-capped SVO films to identical uncapped films that were exposed to ambient conditions. The significant over-oxidation of the SVO surface in the bare film, illustrated by a primary V 5+ component, is prevented by the TiO x layer in the capped film. Furthermore, the capped film further exhibits a decrease in Sr surface phases. These results demonstrate the importance and potential of such capping layers in preserving the bulk properties of correlated oxides in their NSR, enabling more accurate probes for their underlying physics and offering a route for their integration into devices.

36 MATERIALS SCIENCE↗