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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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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Bifacial CdTe Solar Cells with Copper Chromium Oxide Back-Buffer Layer

Bifacial solar cells have the potential to maintain energy output higher than monofacial devices under unfavorable weather conditions. A transparent back-buffer layer which can passivate the interface and improve the minority carrier lifetime is critical in CdTe-based bifacial devices. Herein, solution-processed Cu x Cr y O z as a promising back-buffer for CdTe/CdS solar cells is demonstrated. The carrier lifetimes measured at the front and back of the device are 31.2 and 3.1 ns, respectively, which correspond to an increase of ≈38% and 138%, respectively, compared to the reference device. This dramatic improvement in lifetime results in a 100% increase in short-circuit current measured with backside illumination. The best bifacial device has efficiencies 7.6% and 12.5%, respectively, from back and front illumination, yielding a bifaciality factor of 0.60.

14 SOLAR ENERGY↗
NASA NTRS1973

Friction, wear, and transfer of carbon and graphite to copper, chromium, and aluminum metal surfaces in vacuum

Sliding friction experiments were conducted with amorphous and fully graphitized carbons sliding on copper and on films of chromium and aluminum on copper. Auger emission spectroscopy analysis was used to monitor carbon transfer to the metal surfaces. Friction and wear were also measured. Metal surfaces were examined both in the clean state and with normal oxides present. Results indicate that different metals have an important effect on friction, wear, and transfer characteristics. With amorphous carbon, the least chemically active metal gave the highest wear and amount of carbon transfer. Both forms of carbon gave lower friction and wear and lower transfer rates when in contact with clean, as opposed to oxide-covered, chromium surfaces. With copper, the reverse was true; cleaning was detrimental.

Buckley, D. H.↗
NASA NTRS1974

Process for the production of star-tracking reticles

Reticles designed with quartz bases are masked with desired pattern and then are coated with highly adherent layers of chromium, chromium silver alloy, silver, copper, and black chromium (mixture of chromium and chromium oxides). Black chromium final layer produces required nonreflective surface.

Toft, A. R.↗
NASA NTRS2003

NiAl Coatings Investigated for Use in Reusable Launch Vehicles

As part of its major investment in the area of advanced space transportation, NASA is developing new technologies for use in the second- and third-generation designs of reusable launch vehicles. Among the prototype rocket engines being considered for these launch vehicles are those designed to use liquid hydrogen as the fuel and liquid oxygen as the oxidizer. Advanced copper alloys, such as copper-chromium-niobium (Cu-8(at.%)Cr- 4(at.%)Nb, also referred to as GRCop-84), which was invented at the NASA Glenn Research Center, are being considered for use as liner materials in the combustion chambers and nozzle ramps of these engines. However, previous experience has shown that, in rocket engines using liquid hydrogen and liquid oxygen, copper alloys are subject to a process called blanching, where the material undergoes environmental attack under the action of the combustion gases. In addition, the copper alloy liners undergo thermomechanical fatigue, which often results in an initially square cooling channel deforming into a dog-house shape. Clearly, there is an urgent need to develop new coatings to protect copper liners from environmental attack inside rocket chambers and to lower the temperature of the liners to reduce the probability of deformation and failure by thermomechanical fatigue.

Raj, Sai V.↗
DOE OSTI2025

Overcoming the thermal conductivity versus oxidation resistance barrier in high-temperature steels

Heat-resistant steels with high chromium additions (≥5 weight percent) are critical for many high temperature energy and manufacturing applications, including heat exchangers, pistons for engines, and dies for metal working and casting. However, while high chromium additions increase oxidation resistance at elevated temperatures, they also compromise thermal conductivity, resulting in a metallurgical trade-off between these two important properties. Here we show that a microstructure with both higher thermal conductivity and improved oxidation resistance at elevated temperatures is achieved in a unique steel with only 1 weight percent chromium, thereby overcoming the long-standing metallurgical trade-off. This is accomplished through a tailored thermal treatment that produces a tempered martensitic matrix with low solute content and a fine dispersion of copper precipitates and molybdenum enriched carbides. A further discovery is that the resultant thermally grown oxide includes an iron-copper-manganese-enriched outer layer that provides high-temperature oxidation protection equivalent to heat-resistant steels with five times the chromium content and 25% lower thermal conductivity.

Pierce, Dean T. [Oak Ridge National Laboratory (OR↗
DOE OSTI2023

The Reductive Leaching of Chalcopyrite by Chromium(II) Chloride for the Rapid and Complete Extraction of Copper

A hydrometallurgical process is developed to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. The unique feature of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Chalcopyrite reduction by chromium(II) ion is described for the first time and superior kinetics are shown. At high concentrate loadings of 39, 78, and 117 gL –1 , chalcopyrite reacted completely within minutes at room temperature and pressure. The XRD, SEM-EDS, and XPS measurements indicate that chalcopyrite reacts to form copper(I) chloride (CuCl). After the reductive treatment, the mineral products are leached by iron(III) sulfate to demonstrate the complete extraction of copper. The chromium(II) ion may be regenerated by an electrolysis unit inspired by an iron chromium flow battery in a practical industrial process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Deposition and material response from Mach 0.3 burner rig combustion of SRC 2 fuels

Collectors at 1173K (900 C) were exposed to the combustion products of a Mach 0.3 burner rig fueled with various industrial turbine liquid fuels from solvent refined coals. Four fuels were employed: a naphtha, a light oil, a wash solvent and a mid-heavy distillate blend. The response of four superalloys (IN-100, U 700, IN 792 and M-509) to exposure to the combustion gases from the SRC-2 naphtha and resultant deposits was also determined. The SRC-2 fuel analysis and insights obtained during the combustion experience are discussed. Particular problems encountered were fuel instability and reactions of the fuel with hardware components. The major metallic elements which contributed to the deposits were copper, iron, chromium, calcium, aluminum, nickel, silicon, titanium, zinc, and sodium. The deposits were found to be mainly metal oxides. An equilibrium thermodynamic analysis was employed to predict the chemical composition of the deposits. The agreement between the predicted and observed compounds was excellent. No hot corrosion was observed. This was expected because the deposits contained very little sodium or potassium and consisted mainly of the unreactive oxides. However, the amounts of deposits formed indicated that fouling is a potential problem with the use of these fuels.

Santoro, G. J.↗
DOE OSTI2024

Enhancing nitrogen fixation efficiency in glow-like discharge by reducing cathode-fall voltage

In plasma nitrogen fixation devices, discharge electrodes are crucial yet susceptible to oxidation and corrosion due to plasma’s high temperatures and oxygen content, which could alter discharge modes. This research evaluates the impact of different electrode materials, including iron, chromium, nickel, copper, and 304 stainless steel, on nitrogen fixation efficiency in glow-like discharges driven by high-voltage DC power. Notably, iron and 304 stainless steel cathodes undergo a mode transition at increased currents, evident from plasma color shifts and significant voltage reductions. Fourier transform infrared spectroscopy analyses reveal that such mode changes minimally affect nitrogen oxide production rates, leading to a notable decrease in energy consumption for nitrogen fixation by up to 40%. OES and SEM-EDS measurements suggest that iron oxide, with its higher secondary electron emission, replaces metal as the cathode material, facilitating mode transitions and maintaining discharge current at lower voltages. Further, this voltage change is largely attributed to the cathode voltage drop, highlighting the minimal role of the cathode fall region in NO x synthesis. These findings underscore the potential for improving plasma nitrogen fixation energy efficiency by choosing suitable cathode materials to lower the cathode-fall voltage.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2000

Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners while maintaining the superior CuCrNb properties are also presented.

Zimmerman, Frank↗
NASA NTRS1960

Oxidation Behavior of Binary Niobium Alloys

This investigation concludes a study to determine the effects of up to 25 atomic percent of 55 alloying additions on the oxidation characteristics of niobium. The alloys were evaluated by oxidizing in an air atmosphere for 4 hours at 1000 C and 2 hours at 1200 C. Titanium and chromium improved oxidation resistance at both evaluation conditions. Vanadium and aluminum improved oxidation resistance at 1000 C, even though the V scale tended to liquefy and the Al specimens became brittle and the scale powdery. Copper, cobalt, iron, and iridium improved oxidation resistance at 1200 C. Other investigations report tungsten and molybdenum are protective up to about 1000 C, and tantalum at 1100 C. The most important factor influencing the rate of oxidation was the ion size of the alloy additions. Ions slightly smaller than the Nb(5+) ion are soluble in the oxide lattice and tend to lower the compressive stresses in the bulk scale that lead to cracking. The solubility of the alloying addition also depends on the valence to some extent. All of the elements mentioned that improve the oxidation resistance of Nb fit this size criterion with the possible exception of Al, whose extremely small size in large concentrations would probably lead to the formation of a powdery scale. Maintenance of a crack-free bulk scale for as long as possible may contribute to the formation of a dark subscale that ultimately is rate- controlling in the oxidation process. The platinum-group metals, especially Ir, appear to protect by entrapment of the finely dispersed alloying element by the incoming Nb2O5 metal-oxide interface. This inert metallic Ir when alloyed in a sufficient amount with Yb appears to give a ductile phase dispersed in the brittle oxide. This scale would then flow more easily to relieve the large compressive stresses to delay cracking. Complex oxide formation (which both Ti and Zr tend to initiate) and valence effects, which probably change the vacancy concentration in the scale, are masked by the overriding tendency for a porous scale.

Barrett, Charles A.↗
NASA NTRS1977

Oxidation and corrosion behavior of modified-composition, low-chromium 304 stainless steel alloys

The effects of substituting less strategic elements than Cr on the oxidation and corrosion resistance of AISI 304 stainless steel were investigated. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of at least 33%. Two alloys containing 12% Cr and 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified as most promising for more detailed evaluation.

Stephens, J. R.↗
NASA NTRS1978

Substitution for chromium in 304 stainless steel

An investigation was conducted to determine the effects of substituting less strategic elements for Cr on oxidation and corrosion resistance of AISI 304 stainless steel. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of 33 percent. Two alloys containing 12% Cr plus 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified which exhibited oxidation and corrosion resistance comparable to AISI 304 stainless steel.

Stephens, J. R.↗
NASA NTRS1998

Creep of Uncoated and Cu-Cr Coated NARloy-Z

Stress rupture creep tests were performed on uncoated and Cu-30vol%Cr coated NARloy-Z copper alloy specimens exposed to air at 482 C to 704 C. The results showed that creep failure in air of unprotected NARloy-Z was precipitated by brittle intergranular surface cracking produced by strain assisted grain boundary oxidation (SAGBO) which in turn caused early onset of tertiary creep. For the protected specimens, the Cu-Cr coating remained adherent throughout the tests and was effective in slowing down the rate of oxygen absorption, particularly at the higher temperatures, by formation of a continuous chromium oxide scale. As the result of reducing oxygen ingress, the coating prevented SAGBO initiated early creep failure, extended creep deformation and increased the creep rupture life of NARloy-Z over the entire 482 C to 704 C test temperature range.

Walter, R. J.↗