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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

ZrB{sub 2}-SiC-Ta{sub 4}HfC{sub 5}/Ta{sub 4}HfC{sub 5} Oxidation-Resistant Dual-Layer Coating Fabricated by Spark Plasma Sintering for C/C Composites

In this work, a ZrB{sub 2}-SiC-Ta{sub 4}HfC{sub 5}/Ta{sub 4}HfC{sub 5} oxidation-resistant dual-layer coating was fabricated to improve the oxidation resistance of carbon–carbon (C/C) composites. The coating was prepared by pack cementation combined with the slurry paste method. Spark plasma sintering was used in the procedure. The as-prepared dual-layer coating was approximately 110 μm, and no distinct interface was observed between the coating and the matrix. The isothermal oxidation test results showed that the dual coating effectively prevented C/C composites from oxidizing. The weight loss of the coated samples was only 3.3 and 9.5% after oxidation at 1773 K for 20 h and ten thermal shock cycles between 1773 K and room temperature in air, respectively. The pores and microcracks were the main reason for the failure of the coating.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Bioceramic Coating Produced on AZ80 Magnesium Alloy by One-Step Microarc Oxidation Process

A self-sealing bioceramic coating was prepared on AZ80 magnesium alloy by one-step microarc oxidation (MAO) in an alkaline silicate solution in the presence of HA nanoparticles and K{sub 2}TiF{sub 6}. The influence of oxidation time on the microstructure and corrosion resistance was investigated. The surface and cross-sectional morphologies of the coatings were characterized by scanning electron microscopy, while their phase structure and chemical composition were obtained by x-ray diffraction analysis and energy-dispersive spectroscopy, respectively. The corrosion behavior of the coatings was evaluated by electrochemical measurements in a simulated body fluid. The results show that the self-sealing bioceramic coatings are mainly composed of MgO, MgF{sub 2}, Ti{sub 3}O{sub 5}, Mg{sub 2}SiO{sub 4}, and HA phases, which effectively improve the corrosion resistance of the AZ80 magnesium alloy. The added K{sub 2}TiF{sub 6} plays a key role in producing self-sealing coating, while the HA nanoparticles improve the bioactivity of the coating. Thus, the self-sealing bioceramic coating obtained by the one-step MAO process may develop into a suitable surface treatment technology for bone implants in clinical application.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Improved Corrosion Resistance of Ni-Co Coatings Prepared by Electrodeposition with Large Centrifugal Acceleration

A higher Co content in Ni-Co coatings leads to better corrosion resistance to a certain degree. In this paper, centrifugal acceleration was introduced in the electrodeposition of Ni-Co coatings in order to obtain improved Ni-Co coatings with high Co content. With different centrifugal accelerations, the Co content, morphology, preferred coating orientation, microhardness, and wear and corrosion resistance were examined. Under large centrifugal acceleration, a maximal Co content of 38.25% was obtained according to the EDS results, which was higher than that obtained using normal electrodeposition. The SEM images indicated that the morphology of the prepared Ni-Co coatings with the highest Co content was smoothened. In addition, the microhardness of Ni-Co coatings with increased Co content was improved to about 530HV, which was hardly achieved under normal electrodeposition. Most of all, based on the polarization curve and EIS results, the corrosion resistance was significantly enhanced as the Co content reached the maximum. In general, corrosion resistance of the deposited Ni-Co coatings can be improved with large centrifugal acceleration.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure and Properties of AlCoCrFeNiTi High-Entropy Alloy Coating on AISI1045 Steel Fabricated by Laser Cladding

AISI1045 steel is widely used in mechanical engineering. In spite of the favorable toughness and strength, the surface properties of AISI1045 steel, such as hardness, wear resistance and corrosion resistance, are not ideal. Therefore, surface modification of AISI1045 is necessary, especially for the parts suffering severe work condition. Laser cladding is a promising surface modification technology. In this work, the AlCoCrFeNiTi high-entropy alloy (HEA) coatings were prepared on the AISI1045 steel to improve its surface properties. Metallurgical bonding is obtained between the coating and the substrate. The microstructure and surface properties of the coating were characterized by scanning electron microscope, energy-dispersive spectrometry, x-ray diffraction, electrochemical workstation, microhardness tester and pin-on-ring wear tester. The microstructure of the coating produced by laser cladding is dendritic. The AlCoCrFeNiTi HEA coating is mainly composed of disordered body-centered cubic phase (Fe-Cr), ordered B2 phase (AlNi) and intermetallic phase (Ti-rich). The coating shows excellent abrasion resistance and corrosion resistance in comparison with the substrate. The maximum microhardness of the coating reaches approximately 865 HV, which is 4.5 times of AISI1045 steel.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure and Corrosion Behavior of Cr Coating on M50 Steel Fabricated by Electrospark Deposition

Cr coatings are deposited on M50 steel by electrospark deposition with different parameters (100 V-60 μF, 100 V-90 μF, 100 V-120 μF, 150 V-60 μF, 150 V-90 μF and 150 V-120 μF). Influences of the depositing parameters on the microstructure and the corrosion behavior of the coatings were experimentally investigated. There is a linear trend of growth between the mass gain per area and the deposition cycles before reaching the maximum values. The voltage has more influence on the mass gain per area than the capacitance. The coatings display a splash-like pattern decorated with a few of micro-cracks. The micro-cracks are more sensitive to the voltage than the capacitance. The anti-corrosion ability of the coating is significantly better than the M50 steel. Local corrosion occurs in the coating when there are through-coating cracks. The coating deposited under 150 V-60 μF has the minimum defect density and the best anti-corrosion behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2019

DLC-coating Application to Improve the Durability of Ceramic Tools

The work is devoted to the experimental study of the efficiency of Arc-PVD and PACVD industrial technologies for the application of diamond-like carbon (DLC) coatings on ceramic cutting plates based on Al{sub 2}O{sub 3} + TiC to increase the wear resistance of the tool when turning of bearing hardened steel 102Cr6. The authors conducted a set of studies and tests as the study of the structure of DLC coatings (correlation between sp{sup 3} and sp{sup 2} bonds) using photoelectron spectroscopy; evaluation of roughness, microhardness and adhesive bond strength of DLC coatings with the ceramic base; study of coated ceramics wear under fretting conditions; and experimental evaluation of the effect of DLC coatings on the resistance of ceramic plates during turning of hardened steel. The durability of ceramic plates was increased by 1.6 times by applying PACVD DLC coatings. A slightly smaller effect in 1.4 times was achieved by applying DLC coatings using Arc-PVD technology.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of CeO{sub 2} on the Microstructure and Properties of Laser Cladding 316L Coating

Laser cladding was used to distribute a CeO{sub 2}-modified 316L powder coating onto a 316L stainless steel surface. The cladding layer phase composition was evaluated through x-ray diffraction. An analysis of the microstructure was conducted using an optical microscope and scanning electron microscope, while the micro-hardness was measured using a tester. The coating corrosion behavior in response to 3.5% NaCl solution was analyzed by polarization curves and electrochemical impedance spectroscopy. Finally, the overall performance of coatings with different CeO{sub 2} concentrations, 1, 2, and 3%, was compared. Results showed that adding CeO{sub 2} significantly refined the grains, reduced the coating porosity, and effectively limited the appearance of local corrosion. Also, additive CeO{sub 2} shifted the coating’s electrode potential in a positive direction, minimizing the current density of corrosion, creating a stable passivation film, and improving the coating’s corrosion resistance. The coating performance (hardness and corrosion behavior) was optimal when 2% CeO{sub 2} was employed as the powder mass.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Solderability of AZ31B Magnesium Alloy Coated by Copper and Strength of the Solder Joints

Magnesium alloys are promising as light materials, while their high chemical reactivity makes them difficult to be soldered. In this study, the AZ31B alloy was pretreated by zincification and coated by an electrodeposited Cu layer, and then soldered with Sn-58Bi solder in air furnace. The microstructure and properties of the AZ31B/Cu(Zn)/SnBi solder joints were characterized to evaluate the solderability of the Cu-coated Mg alloy and the influence of soldering on the Cu coating. It was found that the Cu coating is dense, and little defect exists along the Cu(Zn)/AZ31B interface. The soldering process has little negative effect on the bonding between the Cu coating and the AZ31B substrate, and the AZ31B/Cu(Zn)/SnBi solder joints of high metallurgical quality were obtained. Tensile fracture of the solder joint occurs mainly in the solder, with no peeling of the Cu coating. Under shear loading, cracks initiate inside the SnBi solder and the final fracture of the joint occurs around the Cu{sub 6}Sn{sub 5}/solder interface or along the Cu(Zn)/AZ31B interface. The tensile and shear strength of the AZ31B/Cu(Zn)/SnBi solder joints are close to that of the SnBi/Cu solder joints. It is demonstrated that the Cu-coated Mg alloy shows superior solderability and can be soldered by the Sn-based low-melting solder in air.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Characteristics and Tribological Behaviors of TiAlN/Cr-Ni Composite Coatings at Elevated Temperatures

A TiAlN/Cr-Ni composite coating was fabricated on H13 hot work mold steel using a cathode ion arc plating and laser cladding. The surface and cross-sectional morphologies, chemical compositions, phases and surface roughness of obtained coating were analyzed using a scanning electron microscope, energy disperse spectroscopy, x-ray diffraction and atomic force microscope, respectively, and the bonding strength was measured using a scratch test. The friction-wear properties of TiAlN/Cr-Ni coating at 400, 500 and 600 °C were investigated using a ball-on-disc wear test. The results show that the TiAlN coating is primarily composed of c-TiN and c-AlN hard phases, and the bonding strength of TiAlN coating with the Cr-Ni coating is 22.15 N. The average coefficients of friction of TiAlN/Cr-Ni coating at 400, 500 and 600 °C are 0.458, 0.318 and 0.449, respectively, and the corresponding wear rates are 0.329 × 10{sup −3}, 0.384 × 10{sup −3} and 0.205 × 10{sup −3} mm{sup 3} N{sup −1} s{sup −1}, respectively, and the wear mechanism includes adhesive wear and oxidation wear.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of Cr/Zircaloy-4 coating qualities for enhanced accident tolerant fuel cladding

Cr-coated zirconium alloys represent a modern approach to enhance cladding safety during accident scenarios. Two high-power impulse magnetron sputtered Cr-coated Zry-4 systems were subjected to simulated loss-of-coolant accident conditions to investigate cladding performance. The first Cr-coating (4.8 µm thick) was deposited onto Zry-4 cladding and exhibited through-thickness cracking while the second Cr-coating (6.8 µm thick) was deposited with improved deposition parameters onto polished Zry-4 and exhibited no cracking. During burst testing, the coating with a higher density of defects failed to consistently reduce oxidation and exhibited similar burst behavior as Zry-4. In contrast, the second Cr-coating reduced ZrO 2 formation through formation of Cr 2 O 3 and displayed enhanced burst temperatures by ~80 °C compared to Zry-4. Utilizing an empirical relation for burst behavior of zirconium alloys, the 6.8 µm Cr/Zry-4 system displayed enhanced burst temperatures equivalent to an effective 0.464 mm increase in Zry-4 wall thickness, highlighting the value of continuous Cr coatings for accident scenarios.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Fuel performance analysis of Cr-coated Zircaloy-4 cladding during a prototypical LOCA event using BISON

Here, deformation and failure of chromium (Cr) coated Zircaloy-4 (Zry-4) were studied in loss-of-coolant accident (LOCA) conditions using the BISON fuel performance code. The BISON validation model simulating Halden research reactor experiments was extended to include Cr coatings and higher rod internal pressures to simulate high-burnup fuel. The transient simulations show Cr coatings help relieve stress in the Zry-4 substrate during the transient, delaying the onset of high-temperature creep, which leads to ballooning and bursting of the cladding. A nominal Cr coating thickness of 30 µm delays clad failure by 26 seconds and increases the clad burst temperature by 40 K. A parametric study showed that time to failure and burst temperature both increase with coating thickness, and Cr-coated cladding offers burst resistance under a wide range of rod internal pressures simulating high-burnup fuel. Results indicate that a thin Cr coating provides resistance against ballooning and bursting of cladding during LOCA events.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Effect of Thickness on the Structure, Composition and Properties of Titanium Nitride Nano-Coatings

Titanium nitride (TiNx) coatings were grown by magnetron sputtering onto Si(1 0 0) substrates by varying time of deposition to produce coatings with variable thickness (dTiN) in the range of 20-120 nm. TiNx coatings were characterized by studying their structure, composition, and mechanical properties. Nuclear reaction analysis (NRA) combined with Rutherford backscattering spectrometry (RBS) analyses indicate that the grown coatings were stoichiometric TiN. Grazing incidence X-ray diffraction (GIXRD) measurements indicate that the texturing of TiN coatings changes as a function of dTiN. The (1 1 1) and (0 0 2) peaks appear initially; (1 1 1) becomes intense while (0 0 2) disappears with increasing dTiN. Dense, columnar grain structure was evident for all the coatings in electron microscopy analyses. The residual stress for TiN coatings with dTiN~120 nm was 1.07 GPa in compression while thinner samples exhibit higher values of stress.

Coatings↗
DOE OSTI2025

Investigation of MO x (M = Cr, Mn, Re, and Mo) coated stainless-steel electrodes for oxygen evolution reaction in natural seawater electrolysis

Seawater electrolysis is considered a potential strategy for large-scale of affordable H 2 production. However, poor durability of the anode for oxygen evolution reaction (OER) in natural seawater is a remaining concern due to chloride-induced reaction. Herein, the effect of various MO x (M = Mn, Cr, Re, and Mo) coated stainless steel (SS) electrodes on OER in direct natural seawater electrolysis was comprehensively studied. It is found that the Mo-coated SS electrode is superior to all others in terms of durability, followed by Re-coated SS, while the Cr and Mn-coated SS electrodes show the poorest durability. Additionally, the durability and activity of the Mo/SS electrode can be boosted remarkably in 1 M KOH/seawater compared to the natural seawater, resulting in an overpotential at 10 mA cm −2 decrease from 830 to 399 mV. Meanwhile, no degradation is observed at 1000 mA cm −2 for 100 h in 1 M KOH seawater, which is among the best stability, based on the literature review. Moreover, the improved durability and activity with Mo coating were extended to the Inconel 718 substrate, and around 40 % improvement in durability and 25 mV overpotential decrease at 10 mA cm −2 are observed, which indicates that Mo coating can be considered as a universal approach to improve the anode durability and activity. The improved performance with Mo coating may be attributed to the continuous Mo oxide layer formation or in situ generated MoO 4 2− in the OER process. In conclusion, this work provides a holistic strategy to enhance the anode durability and activity under harsh conditions, offering valuable insights for designing corrosion-resistant electrodes in direct seawater electrolysis.

Direct seawater electrolysis↗
DOE OSTI2013

Wear resistance and microstructural properties of Ni–Al/h-BN/WC–Co coatings deposited using plasma spraying

Hexagonal boron nitride (h-BN) and tungsten carbide cobalt (WC–Co) were added to nickel aluminum alloy (Ni–Al) and deposited as plasma sprayed coatings to improve their tribological properties. The microstructure of the coatings was analyzed using a scanning electron microscope (SEM). Following wear test, the worn surface morphologies of the coatings were analyzed using a SEM to identify their fracture modes. The results of this study demonstrate that the addition of h-BN and WC–Co improved the properties of the coatings. Ni–Al/h-BN/WC–Co coatings with high hardness and favorable lubrication properties were deposited. - Highlights: • We mixed Ni–Al, h-BN and WC–Co powders and deposited them as composite coatings. • Adding WC–Co was found to increase the hardness and reduce the wear volume loss. • Adding h-BN was found to decrease the hardness and reduce the friction coefficient. • This composite coating was shown to have improved wear properties at 850 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Morphological and electrochemical characterization of electrodeposited Zn–Ag nanoparticle composite coatings

Silver nanoparticles with an average size of 23 nm were chemically synthesized and used to fabricate Zn–Ag composite coatings. The Zn–Ag composite coatings were generated by electrodeposition method using a simple sulfate plating bath dispersed with 0.5, 1 and 1.5 g/l of Ag nanoparticles. Scanning electron microscopy, X-ray diffraction and texture co-efficient calculations revealed that Ag nanoparticles appreciably influenced the morphology, micro-structure and texture of the deposit. It was also noticed that agglomerates of Ag nanoparticles, in the case of high bath load conditions, produced defects and dislocations on the deposit surface. Ag nanoparticles altered the corrosion resistance property of Zn–Ag composite coatings as observed from Tafel polarization, electrochemical impedance analysis and an immersion test. Reduction in corrosion rate with increased charge transfer resistance was observed for Zn–Ag composite coatings when compared to a pure Zn coating. However, the particle concentration in the plating bath and their agglomeration state directly influenced the surface morphology and the subsequent corrosion behavior of the deposits. - Highlights: • Synthesis of Ag nanoparticles with an average size of 23 nm • Fabrication of Zn/nano Ag composite coating on mild steel • Composite coatings showed better corrosion resistance. • Optimization of particle concentration is necessary.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Multilayered vacuum-arc nanocomposite TiN/ZrN coatings before and after annealing: Structure, properties, first-principles calculations

Highlights: • Multilayer TiN/ZrN films were deposited using sequential vacuum-arc deposition of Ti and Zr targets in nitrogen atmosphere; • Several samples were annealed in air at the temperature 700 °C; • First-principles calculations of TiN(111), ZrN(111) structures and TiN(111)/ZrN(111) multilayer were carried out; • All deposited samples were highly polycrystalline with quite large 20–25 nm crystals; • The nanohardness and elastic modulus of non-annealed coatings reached 42 GPa and 348 GPa, respectively; • Deposited coatings demonstrate good wear and oxidation resistance; - Abstract: Nanoscale multilayered TiN/ZrN films were deposited using sequential vacuum-arc deposition of Ti and Zr targets in a nitrogen atmosphere. Studies of film's properties were carried out using various modern methods of analysis, such as XRD, STEM, HRTEM, SIMS combined with results of nanoindentation and tribological tests. To interpret the mechanical properties of the deposited multilayer films first-principles calculations of TiN(111), ZrN(111) structures and TiN(111)/ZrN(111) multilayer were carried out. To study the influence of thermal annealing, several samples were annealed in air at the temperature 700 °C. All deposited samples were highly polycrystalline with quite large 20–25 nm crystals. The crystalline planes were very ordinated and demonstrated an excellent coordinated growth. The nanohardness and elastic modulus of non-annealed coatings reached 42 GPa and 348 GPa, respectively. Annealing in air at the temperature 700 °C led to partial oxidation of the multilayered coatings, however hardness of the non-oxidized part of the coatings remained as high, as for initial coatings. All deposited coatings demonstrate good wear resistance.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Microstructure detection of Mg-Zi-Ti-Si amorphous composite coating prepared by SMAT

Highlights: • The Mg-Zn-Ti-Si amorphous composite coating was prepared on Mg alloy via SMAT. • Except for amorphous portion, the phases of coating include Zn, Mg{sub 7}Zn{sub 3}, and Si. • The coating was thick and rough but it was well combined with the matrix. • During SMAT, the matrix surface was also strengthened because of solid-solution and grain refinement. - Abstract: The Mg-Zn-Ti-Si coating was prepared on Mg alloy through surface mechanical attrition treatment (SMAT) which was simple and low-cost. The microstructure and phase composition of coating were detected through a scanning electron microscope (SEM), an X-ray diffractometer (XRD) and a high resolution transmission electron microscope (HRTEM). The results demonstrated that the layer thickness, which depended on the rotation speed, was 20–80 μm. Although the coating was rough, it was well combined with the matrix. The XRD pattern and HRTEM image analysis demonstrated that the coating contained both amorphous and crystalline phases (Zn, Mg{sub 7}Zn{sub 3} and Si). The process also led to matrix surface strengthening; the mechanisms are solid solution and grain refinement.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Glassy carbon formation from pyrolysis of polymeric coatings on fiber-optic sensors

Deploying fiber-optic sensors in nuclear reactors requires a detailed understanding of radiation effects on the fiber materials and the transmitted signals. Previous work has shown large wavelength shifts in the reflected spectra obtained from polymer-coated fiber-optic temperature sensors exposed to high neutron fluences. The sensor drift resulting from these wavelength shifts cannot be explained by radiation effects on fused silica glass. These shifts are hypothesized to be caused by the conversion of the polymeric fiber coating to a glassy carbon via radiolysis and/or pyrolysis and subsequent radiation-induced compaction. Here, thermal degradation of these polymeric coatings was studied to provide insight into the potential origins of the sensor drift phenomenon. Acrylate- and polyimide-coated fibers were heated under various temperatures (250–1300 °C) and environments (oxidative and inert), and the resulting coating products were characterized via mass-loss data, scanning electron microscope imaging, and Raman spectroscopy. Results suggest that the polymer decomposition product of both coating types, at least under inert conditions, is indeed a glassy carbon. Analytical models that account for radiation-induced glassy carbon coating compaction show significant compressive fiber strains and predicted wavelength shifts that agree well with experimental measurements, providing additional evidence that supports the hypothesized origins of the sensor drift.

36 MATERIALS SCIENCE↗