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Results for “High-temperature oxidation”

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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Modeling a High-Temperature Electrochemically Driven Water-Gas-Shift Process Using a Mixed-Conducting Membrane without External Electrical Power

This paper develops a model to predict and interpret the performance of an elevated-temperature, electrochemical, membrane-assisted, water-gas-shift process. The process uses separated feed streams of H 2 O and CO to produce separated streams of H 2 and CO 2 , without an external electrical power source. The dense ceramic membrane is mixed ionic-electronic-conducting (MIEC) gadolinium-doped ceria (GDC) and the porous composite electrodes are Ni-YSZ. At elevated temperature, GDC conducts both oxygen ions and small polarons. The present process uses chemical potential to drive the process. Electrochemical oxidation of CO proceeds within the composite anode and H 2 O reduction proceeds within the composite cathode. At high temperature (e.g., T > 700 °C), GDC has significant electronic leakage in the form of a reduced-cerium small polaron, which supports the charge-transfer reactions. In a typical electrolyzer or fuel cell, this leakage is significantly problematic. However, the present process depends on the leakage current to complete the electrochemical circuit. Model development and validation is based on measured material properties and reactor performance. Potential applications include using CO-rich blast-furnace off gases in steel processing, producing separated streams of H 2 and CO 2 .

Zhu, Huayang↗
DOE OSTI2025

Direct Conversion of MnO2 into Atomic Mn Sites for Oxygen Reduction

Development of platinum group metal (PGM)-free catalysts has been investigated to replace the platinum group metal catalyst in future inexpensive polymer electrolyte membrane (PEM) fuel cells. Usually, synthetic methods for these PGM-free catalysts involve introducing transition-metal salts or molecules. Herein, we demonstrate a facile synthetic method to prepare PGM-free Mn-N-C catalysts by directly converting manganese oxides into highly active MnN4 sites. Typically, MnO2 is used as a Mn source. Ammonium chloride and benzimidazole are introduced during high-temperature treatment to enhance catalytic activity and stability further. Ammonia generated from the decomposition of ammonium chloride can improve the intrinsic ORR activity of MnNx moieties through chemical or electronic effects by introducing additional nitrogen groups. The Mn-N-C catalyst exhibits promising ORR activity, achieving a half-wave potential of 0.83 V in 0.5 M H2SO4, outperforming most PGM-free ORR catalysts. The robust carbon structure resulting from organic-molecule treatment is also verified by electrochemical and physical characterization, thereby improving the catalyst's durability.

Yang, Xiaoxuan↗
DOE OSTI2024

AOI [1] Advanced Manufacturing of Ceramic Anchors with Embedded Sensors for Process and Health Monitoring of Coal Boilers

Researchers at West Virginia University (WVU) developed methods to fabricate and test ceramic anchors with an embedded sensor technology for monitoring the health and processing conditions within pulverized coal (PC) and fluidized-bed combustion (FBC) boiler systems. The technology included the development of advanced manufacturing processes for 2D/3D printing electroceramic (conductive ceramic) sensor designs within the ceramic anchor microstructure during the manufacturing process. This advanced manufacturing process would allow for the precise control of local microstructure and composition in order to engineer layer-by-layer any protective and electrically active materials within the refractory anchor. This 3D printing technology would permit the rapid and controlled design of the refractory microstructure and embedded sensor design throughout the volume of the ceramic anchor. The work also included a method to interconnect the sensors to boiler shell through the anchor clamp, where the sensor signals will be processed by low-power electronics and transmitted wirelessly to a central processing hub. The end-goal of the program was to produce a ceramic anchor sensor system which would be ready for implementation within a coal boiler, and/or other similar refractory liner systems (such as that in the glass and metal manufacturing areas). The project objectives were to: 1) Define the chemical and microstructural stability, in addition to the electrical properties, of oxide and non-oxide ceramic composites to be embedded within the ceramic anchor compositions that may operate up to 1400ºC; 2) Develop and implement the 2D/3D printing technology to pattern and control the microstructure of the ceramic anchor and embedded sensor circuits; 3) Develop an interconnect technology which will permit easy installation of the ceramic anchors and signal collection at the boiler shell; 4) Develop low power analog electronics and wireless communication hardware to efficiently collect the sensor signal at each processing unit and transmit data to a central hub for data analysis; 5) Demonstrate the smart ceramic anchor system for temperature and liner fracture within a high-temperature processing unit, such as a boiler furnace or glass melting furnace floor/wall liner.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2025

Technology for Electrically Enhanced Thermochemical Hydrogen (TEETH)

This is the Final Technical Report for the TEETH project. The TEETH concept couples high-temperature solar-thermochemical water splitting (TCWS) with electrochemical H 2 pumping through a proton conducting membrane (PCM) and capitalizes on the benefits of the individual technologies to synergistically providing new benefits. That is, TEETH is a coupled thermochemical/electrochemical process to produce H 2 from steam using solar energy. This approach is thermodynamically equivalent to other hybrid electrolytic processes but is unique in that the equilibrium of the reaction is driven forward by close coupling an electrically driven proton-conducting-membrane to the H 2 -producing reoxidation step. The process uniquely provides and benefits from the necessary H 2 /steam separation and, also unlike other hybrid processes, benefits thermodynamically from the use of readily generated high pressure steam. The concept also satisfies the objectives of previous concepts: 1) decreasing the reduction enthalpy (the reduction temperature), of the working metal-oxide (MO); 2) eliminating the need for a windowed receiver; and 3) widening the scope of material candidates, while also obviating the need for electrical connections to the working MO and avoiding the use of aqueous electrolytes and hydrated redox species (there is no liquid phase), without increasing mechanical complexity.

08 HYDROGEN↗
DOE OSTI2025

Correlating Nb-SRF Surface Processing with Evolution of Surface Electronic States

The few nanometers of the surface exposed to RF field plays a major role in defining the RF performance of superconducting cavities. Over the past two decades, several pioneering surface treatment and processing methods have emerged, enabling remarkable improvements in cavity performance by simultaneously achieving high Q with increasing Eacc. These processing methods include: thermal treatment under ultra-high vacuum (UHV) conditions across lo¬¬¬¬¬¬¬w-, mid-, and high-temperature ranges and high temperature treatments under controlled N2 atmosphere. These processes also produce distinct surface oxide configurations with different valence states, thicknesses, and uniformity, as well as different oxygen concentration profiles in bulk Nb. In this work, we are trying to understand how do surface-processing methods and the resulting oxide/oxygen profiles affect the electronic structure of surface and the mechanism of superconductivity? With the help of Fermilab’s in-house X-ray photoemission facility and, in collaboration with the synchrotron-based angle-resolved photoemission (ARPES) facility at Argonne National Laboratory, we are investigating how the valence band structure and density of states (DoS) near the Fermi level modify with different surface treatments. Our observations show that different surface-processing methods lead to distinct evolutions of the valence-band states near the Fermi level during the superconducting transition. This behavior suggests variations in Nb-O orbital hybridizations and points towards the possibility of different underlying mechanisms of superconductivity governed by the surface chemistry and oxide configuration. We also correlate these distinct superconducting mechanisms with RF cavity performance, specifically focusing on measured surface resistance, the nature of the Q-slope, and quench fields observed in SRF measurements. These results will enable us to identify the potential limiting factors and relevant controllable parameters that can be further optimized to improve the performance of SRF cavities.

Tripathi, Malvika [Fermilab]↗
DOE OSTI2024

Evaluating Nuclear Forensic Signatures for Advanced Reactor Deployment: A Research Priority Assessment

The development and deployment of a new generation of nuclear reactors necessitates a thorough evaluation of techniques used to characterize nuclear materials for nuclear forensic applications. Advanced fuels proposed for use in these reactors present both challenges and opportunities for the nuclear forensic field. Many efforts in pre-detonation nuclear forensics are currently focused on the analysis of uranium oxides, uranium ore concentrates, and fuel pellets since these materials have historically been found outside of regulatory control. The increasing use of TRISO particles, metal fuels, molten fuel salts, and novel ceramic fuels will require an expansion of the current nuclear forensic suite of signatures to accommodate the different physical dimensions, chemical compositions, and material properties of these advanced fuel forms. In this work, a semi-quantitative priority scoring system is introduced to identify the order in which the nuclear forensics community should pursue research and development on material signatures for advanced reactor designs. This scoring system was applied to propose the following priority ranking of six major advanced reactor categories: (1) molten salt reactor (MSR), (2) liquid metal-cooled reactor (LMR), (3) very-high-temperature reactor (VHTR), (4) fluoride-salt-cooled high-temperature reactor (FHR), (5) gas-cooled fast reactor (GFR), and (6) supercritical water-cooled reactor (SWCR).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1972

Method of simultaneous measurement of radiative and lattice thermal conductivity.

A new technique of high-temperature thermal-conductivity measurement is described. A CO2 gas laser is used to generate a low-frequency temperature wave at one face of a small disk-shaped sample, and an infrared detector views the opposite face to detect the phase of the emerging radiation. A mathematical expression is derived which enables phase data at several frequencies to be used for the simultaneous determination of thermal diffusivity and mean extinction coefficient. Lattice and radiative thermal conductivities are then calculated. Test results for sintered aluminum oxide at temperatures from 530 to 1924 K are within the range of error of previously existing data.

Schatz, J. F.↗
NASA NTRS1973

The preliminary design of bearings for the control system of a high-temperature lithium-cooled nuclear reactor

The design of bearings for the control system of a fast reactor concept is presented. The bearings are required to operate at temperatures up to 2200 F in one of two fluids, lithium or argon. Basic bearing types are the same regardless of the fluid. Crowned cylindrical journals were selected for radially loaded bearings and modified spherical bearings were selected for bearings under combined thrust and radial loads. Graphite and aluminum oxide are the materials selected for the argon atmosphere bearings while cermet compositions (carbides or nitrides bonded with refractory metals) were selected for the lithium lubricated bearings. Mounting of components is by shrink fit or by axial clamping utilizing differential thermal expansion.

Yacobucci, H. G.↗
NASA NTRS1972

The origin and stability of lunar goethite, hematite and magnetite.

Extra-lunar contamination, fumarolic activity, and exposure to oxidizing gases from comet or carbonaceous meteorite impacts have been previously proposed as the causes of magnetite, hematite, and goethite in lunar materials. However, these minerals can occur in the stable low-temperature gas-solid equilibrium assemblages of lunar rocks. Below 600 C magnetite is in equilibrium with C-O-H gases with compositions compatible with high-temperature equilibrium with metallic iron; below 150 C hematite is stable in these same gases. Goethite is not stable in carbonaceous gases at low total pressure, and thus gases from impacting carbonaceous material cannot have produced it. Goethite is stable at low temperatures and pressures in almost pure H2-H2O gases. Its minimum stability against hematite is 2 bars total pressure at 130 C and 0.001 bars at 30 C for H2 to H2O ratios compatible with the high-temperature redox state of lunar materials. Thus the traces of magnetite, hematite, and goethite in lunar materials may be the result of normal low-temperature processes indigenous to the moon and not special processes.

Williams, R. J.↗
NASA NTRS1973

Measurement of high-temperature thermal conductivity of Lucalox /Al2O3/ using a heat pipe technique.

The thermal conductivity of Lucalox, a high-purity form of aluminum oxide, has been measured over the temperature range from 870 to 1400 C. The technique employed is a novel one using a lithium-filled heat pipe in series with a gas-gap variable-heat-conductance unit as a heat source. The procedure makes it possible to measure heat flux through the sample directly. The measurements indicate that the thermal conductivity of high-purity aluminum oxide has a minimum value of about 0.05 W/cm deg C at 950 C and increases with higher temperatures to values in the range of 0.3 W/cm deg C at 1400 C.

Forman, R.↗
NASA NTRS1973

Metal-metal laminar composites for high-temperature applications.

A study was conducted to obtain indications of the potentialities of laminar metal-metal composites for elevated-temperature use. Most of the composites consisted of multiple layers or laminae of tungsten alternated with laminae of Nichrome V, a ductile, weaker, but oxidation-resistant alloy. Composites with 50 vol % of each phase made from 0.0025 cm, 0.0125 cm, or 0.050 cm laminae, were tested in tension and stress rupture at temperatures of 871 and 1093 C and in impact at 23 and 524 C. A tension and a short-time stress-rupture test was conducted on specimens of 77 vol % W-Re-Hf-C/23 vol % Inconel Alloy 600 at 1093 C.

Hoffman, C. A.↗
NASA NTRS1951

Study of Chromium-Frit-Type Coatings for High-Temperature Protection of Molybdenum

The achievement of more compact and efficient power plants for aircraft is dependent, among other factors, on the perfection of heat-resisting materials that are superior to those in current use. Molybdenum is one of the high-melting metals (melting point, 4750 F). It is fairly abundant and also can be worked into many of the shapes required in modern power plants. To permit its widespread use at elevated temperatures, however, some means must first be found to prevent its rapid oxidation. The application of a protective coating is one method that might be used to achieve this goal. In the present work, a number of chromium-frit-type coatings were studied. These were bonded to molybdenum specimens by firing in controlled atmospheres to temperatures in the range of 2400 to 2700 F.

CERAMICS↗
NASA NTRS1973

Ablation of ATJ Graphite at High Temperatures

Results of an extensive experimental program on the ablation of ATJ graphite in air at surface pressures of 0.3 to 4.4 atm and surface temperatures of 2570 to 4030 K are presented. The measured mass-loss rates are correlated with surface temperature, pressure, and effective nose radius. The results are compared with several equilibrium thermochemical ablation theories which differ basically in the chemical species that are considered and in the thermodynamic properties assigned to these species. All the theories predict about the same mass-loss rate in the diffusion-controlled oxidation regime and are in good agreement with the experimental results. At higher temperatures, however, the experimental and theoretical results do not agree. At temperatures above 3700 K, the experimental mass-loss rate becomes independent of pressure and an exponential function of temperature. A comparison of the high-temperature results with the theories indicates that all the theories, except the one based on the thermodynamic properties from the JANAF tables, are invalid because they overpredict the mass-loss rate. On the other hand, the theory based on the JANAF properties underpredicts the measured mass-loss rate by a factor of three at 4000 K. At least a portion of this difference between experiment and theory is attributed to particulate mass loss which is visually observed.

Thermochemical ablation↗
NASA NTRS1961

Titanium Nitride: An Oxidizable Coating for the High-Temperature Protection of Graphite

A titanium nitride coating for graphite, prepared by deposition process, protected test specimens for 60 seconds the vapors in a supersonic ceramic-heated air jet with a stagnation temperature of approximately 2,250 K. For the same test conditions, coated specimens showed no damage to the graphite body for the 60-second test, whereas uncoated specimens were very severely damaged after 20 seconds and were destroyed toward the end of the test. A discussion of the coating of these graphite specimens and of some of the conditions necessary for the utilization of oxidizable substances as oxidation-protective coatings for bodies facing high convective heat transfer in the atmosphere is presented.

Wakelyn, N. T.↗
NASA NTRSDate not supplied

Material Properties and Modeling of Room Temperature Vulcanizing Silicone

Room Temperature Vulcanizing silicone (RTV) is a high-temperature adhesive that has successfully been used as a gap-filler between Thermal Protection System (TPS) tiles for heatshields on numerous missions. It is also used to bond instrumentation plugs such as temperature and pressure sensors into the heatshields. While RTV has been traditionally assumed to be a non-porous and non-ablating material, numerous experiments have shown that RTV pyrolyzes and becomes highly porous as it is heated. Heating RTV has also shown swelling, or intumescence, which can pose unique problems that lead to roughness induced boundary-layer transition, surface oxide formation and contamination of heat shield sensors. Therefore, it is crucial to understand and model the intumescence phenomenon of RTV. As data for RTV material properties is limited, the first step in modeling RTV is to collect material properties such as pyrolysis mass-loss, microstructure change, virgin and char porosity, etc. which was performed in our initial study. Additionally, thermomechanical properties such as Young’s modulus and Poisson ratio are required for modeling the intumescence of RTV, which were taken from literature and the coefficient of thermal expansion was collected using in-situ heating and Micro Computed Tomography (µ-CT) in previous studies. Finally, numerous other properties such as pyrolysis gas properties, virgin and char thermal conductivity and specific heat were compiled from previous experiments and literature into a material database that can be used for simulations. In Porous Material Analysis Toolbox based on OpenFOAM (PATO) [4], structural mechanics coupled with material response was used for simulating the intumescence of RTV as it is heated. However, since the permeability of the material is very low, the pyrolysis gas creates an internal pressure build-up as the material is being heated, significantly contributing to the deformation of the material. To correctly characterize this phenomenon, additional physics models were implemented into PATO's stress analysis solver, and results were compared with RTV dilatometry test data as a preliminary verification case. Future work will include experiments of RTV at the Plasmatron X facility and the in-situ heating cell with µ-CT, and improvement of simulation tools to more accurately model RTV intumescence.

PATO↗