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At least 235 records · Page 13

Effect of nickel on the oxidation behavior of FeCrAl alloy in simulated PWR and BWR conditions

FeCrAl alloys are being investigated as candidate materials for light water reactor fuel claddings. The chemical composition of FeCrAl determines its resistance to corrosion under normal operating conditions. The purpose of this paper is to investigate the effect of 0, 1, 3 wt% Ni addition on the passivation characteristics of Fe17Cr5.5Al in oxygenated and hydrogenated simulated reactor waters for 3-month immersion. Current results show that Ni addition improves the passivation of FeCrAl under oxygenated condition and decreases the mass loss under hydrogenated conditions.

36 MATERIALS SCIENCE↗

Roll-To-Roll Atomic Layer Deposition of Titania Nanocoating on Thermally Stabilizing Lithium Nickel Cobalt Manganese Oxide Cathodes for Lithium Ion Batteries

Conformal coating of ceramic layers (nm-thick) on Ni-rich layered cathode materials is an effective strategy for improving high-temperature longevity of Li-ion batteries (LIBs). In this work, we develop a roll-to-roll atomic layer deposition (R2R ALD) apparatus for growing uniform nanolayers of TiO 2 . We explore the effect of ALD parameters (temperature: 120–180 °C and line speed: 2–40 mm s –1 ) on the TiO 2 surface coating and subsequently investigate the electrochemical performance of the as-prepared cathodes. The capacity retention of TiO 2 -coated porous electrodes is substantially improved compared to that of the pristine cathode material for high-temperature cycling. Electrochemical impedance spectroscopy confirms that the ALD-TiO 2 coating suppresses the undesired side reactions initiated at the electrode/electrolyte interface, reduces charge transfer resistance, and ultimately facilitates the Li + transport through the composite cathode nanostructure. The robust design of the ALD-TiO 2 cathode material enables high-temperature operation (>55 °C) with enhanced specific capacity, superior rate capability, excellent cyclability, and ultra-high coulombic efficiency within a wide potential window (3.0–4.35 V). Furthermore, the R2R ALD technique developed in this work paves the way for large-scale fabrication of ceramic-coated cathode sheets with a production rate reaching 2.4 m min –1 for a continuous coating operation.

25 ENERGY STORAGE↗

Mach 1 oxidation of thoriated nickel chromium at 1204 C (2200 F)

TD NiCr was exposed to a Mach 1, 1-atmosphere gas stream at 1204 C for times up to 50 hours. Weight change, metal thickness loss, X-ray diffraction, metallographic, and electron microprobe analyses were made. Neither surface preparation nor thermal cycling had an appreciable effect on the results. Initially, Cr2O3 formed and volatilized, allowing a rapid metal loss rate of 40 microns per hour. After about 1 hour the Cr2O3 broke down, resulting in an NiO overgrowth. The metal loss rate then slowed to 2.5 microns per hour and remained constant to 50 hours.

Lowell, C. E.↗

Oxidation resistant iron and nickel alloys for high temperature use

Iron-base and nickel-base alloys exhibit good oxidation resistance and improved ductility with addition of small amounts of yttrium, tantalum /or hafnium/, and thorium. They can be used in applications above the operating temperatures of the superalloys, if high strength materials are not required.

Hill, V. L.↗

Transverse and longitudinal tensile properties at 760 C of several oxide dispersion strengthened nickel-base alloys

The transverse and longitudinal tensile properties of the oxide dispersion strengthened nickel-base alloys were determined at 760 C. The alloys with small amounts of gamma prime have strength levels suitable for turbine vane applications, while other highly alloyed, gamma prime strengthened superalloys have strengths typical of turbine blade materials. These alloys were produced by mechanical alloying and extrusion and the turbine blade alloys were also directionally recrystallized. Resultant grain aspect ratios varied from 1:1 to over 20:1. Longitudinal tensile strengths ranged from 285 to 1175 MPa, while longitudinal elongations were in excess of 4 percent for all alloys. Transverse tensile strengths were comparable to longitudinal strengths, but transverse ductility levels were generally less than 2 percent elongation. Tensile and yield strengths increased with increasing strain rate over the range 0.001 to 0.05 per second. Ductility in both orientations was not strain rate sensitive but could be related to grain size and grain aspect ratio.

Anglin, A. E., Jr.↗

Zinc-Doped High-Nickel, Low-Cobalt Layered Oxide Cathodes for High-Energy-Density Lithium-Ion Batteries

High-Ni layered oxides with Ni contents greater than 90% are promising cathode candidates for high-energy-density Li-ion batteries. However, drastic electrode-electrolyte reactions and mechanical degradation issues limit their cycle life and practical viability. We demonstrate here that LiNi 0.94 Co 0.04 Zn 0.02 O 1.99 (NCZ), obtained by incorporating 2 mol% Zn 2+ into an ultrahigh-Ni baseline cathode material LiNi 0.94 Co 0.06 O 2 (NC), delivers superior cell performance. NCZ retains 74% of the initial capacity after 500 cycles in full cell assembled with graphite anode, outperforming NC (62% retention). NCZ also possesses a higher average discharge voltage relative to NC with an outstanding average voltage retention of over 99% after 130 cycles in half cells. Bulk structural investigations unveil that Zn doping promotes a smoother phase transition, suppresses anisotropic lattice distortion, and maintains the mechanical integrity of cathode particles. Furthermore, NCZ shows an enhanced interphase stability after long-term cycling, in contrast to the seriously degraded surface chemistry in NC. Finally, this work provides a practically viable approach for designing higher-energy-density high-Ni layered oxide cathodes for lithium-ion batteries.

25 ENERGY STORAGE↗

Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

Hotzler, R. K.↗

Rates and mechanisms of the atomic oxygen reaction with nickel at elevated temperatures

The oxidation of nickel by atomic oxygen at pressure from 1 to 45 N/sq m between 1050 and 1250 K was investigated. In these ranges, the oxidation was found to follow the parobolic rate law, viz., K sub p = 0.0000114 exp(-13410/T) g squared/cm4/sec for films of greater than 1 micron thickness and was pressure independent. The activation enthalpy for the oxidation reaction was 112 + or - 11 kj/mole (27 + or - 3 kcal/mole). Of a number of possible mechanisms and defect structures considered, it was shown that the most likely was a saturated surface defect model for atomic oxidation, based on reaction activation enthalpies, impurity effects, pressure independence, and magnitudes of rates. A model judged somewhat less likely was one having doubly ionized cationic defects rate controlling in both atomic and molecular oxygen. From comparisons of the appropriate processes, the following enthalpy values were derived: enthalpy of activation (Ni diffusion in Ni0) = 110 + or - 30 kj/mole and standard enthalpy change for reaction formation (doubly ionized cation vacancies in Ni0 from atomic oxygen)= -9 + or - 25 kj/mole.

Christian, J. D.↗

The Role and Substitution of Cobalt in the Cobalt‐Lean/Free Nickel‐Based Layered Transition Metal Oxides for Lithium Ion Batteries

Here, the Nickel-based layered transition metal oxide cathode represented by NCM (LiNi x Co y Mn z O 2 , x+y+z=1) and NCA (LiNi x Co y Al z O 2 , x+y+z=1) is widely used in the electric vehicle market due to its specific capacity and high working potential, in which Cobalt (Co) plays a huge role in improving the structural stability during the cycle. However, the limited supply of Co, due to its scarcity and the influence of geopolitics, poses a significant constraint on the further advancement of the Nickel-based layered transition metal oxide cathode in the field of energy storage. In this paper, the mechanism of Co in the Nickel-based layered transition metal oxides is reviewed, including its critical role for structural stability such as the inhibition of cationic mixing and the release of lattice oxygen et al. Subsequently, it outlines various strategies to enhance the performance of Co-lean/free materials, such as ion doping, including single-ion doping and multi-ion co-doping, and various surface coating strategies, so as to eliminate the adverse effects of Co loss on materials. Ultimately, this paper offers a glimpse into the promising future of Cobalt-free strategies for high performance of Nickel-based layered transition metal oxides.

25 ENERGY STORAGE↗

Substrate-Controlled Electronic Properties of Perovskite Layer in Lateral Heterojunction Configuration

In this work, we fabricated halide perovskite-based lateral heterojunction devices with nickel oxide/titanium oxide all back contacts, allowing us to access the perovskite surface directly for analysis with various advanced techniques, including ultraviolet and X-ray photoemission spectroscopy (UPS/XPS), Kelvin probe force microscopy (KPFM), and surface photovoltage (SPY), to discern the role of selective contacts. Specifically, by tuning of the selectivity of the contacts, e.g., through varying the level of nickel oxidation, we show that the selectivity of the contacts induces a gradient in carrier concentration across the surface of the active layer that is connected to carrier extraction at the buried interface and hence to device functionality.

carrier concentration↗

Additive Manufacturing of Oxide Dispersion Strengthened (ODS) Nickel-Based Superalloys

Additive manufacturing of oxide dispersion strengthened (ODS) Ni-based superalloys, via powder bed techniques, could enable near-net-shape manufacturing of intricately shaped components for aerospace applications. This has the potential to transform the design and manufacturing of hot sections of engines which face demands for ever-rising operating temperatures. The goal of this project is to lay the scientific foundation for additive manufacturing of ODS alloys. The objective of this poster is to present work to date as well as proposed future work.

Wilson, Laura G.↗