High-temperature Oxidation Of Nickel Research Articles

High-temperature oxidation of nickel using oxidative constructing approach

The kinetics and structural-phase behavior of the high-temperature oxidation of nickel are considered. It is found that the kinetics of high-temperature oxidation of nickel using the oxidative constructing approach is described by a parabolic law. The resulting compact bunsenite ceramic has a high adhesion to the metal surface. The presence of a gradient penetration of oxide inclusions in the porous structure of metal leads to a blurring of the phase boundary. It is shown that the limiting stage of the nickel oxidation process in the range of 1250–1400°С is nickel oxide dissociation with formation of free ions.

Influence of Superficial Y2O3 Coatings on High-Temperature Oxidation of Ni

Abstract The effects of superficial Y2O3 coatings on the high-temperature oxidation of nickel at 900 °C in air were evaluated. For comparison, Ni substrates with and without superficial CeO2 coating were also prepared in the same condition. The results indicate that Y2O3 or CeO2 coatings result in a significant decrease in the oxidation rate of Ni, especially the former; however the oxidation mechanisms are essentially unaffected. The thickness of Y2O3 or CeO2 coatings has little influence on the oxidation rate of Ni. The beneficial effects of Y2O3 or CeO2 on the oxidation rate of Ni were discussed.

The Effect of Copper and Ceria Additions on the High Temperature Oxidation of Nickel

In this study, the effects of alloying with Cu and external doping with CeO2 on the oxidation of nickel were evaluated. The materials studied were pure Ni, Ni-5wt% Cu, and Ni with the surface doped with CeO2 by pulsed laser deposition (PLD). The oxidation kinetics were measured using thermogravimetric analysis (TGA). The oxidation microstructures were observed by scanning electron microscopy (SEM) compositional analysis was performed with energy dispersive x-ray analysis (EDS) and sputtered neutrals mass spectrometry (SNMS). Phase identification was performed using X-ray diffraction (XRD). The Cu additions had a negligible effect on the oxidation kinetics but Cu was found to be present in the outer portions of the scale in significant concentrations. Doping with CeO2 resulted in a significant decrease in the NiO growth rate. The scales on doped Ni grew primarily inward whereas those on the undoped Ni grew primarily outward. Deposition of the CeO2 dopant onto Ni with a thin, preformed NiO layer produced a similar reduction in the subsequent NiO growth rate. This suggests that the poisoned interface model, proposed by Pieraggi and Rapp, does not describe the effect of the CeO2 dopant. Mechanisms are presented to attempt to describe the above observations.

Quantitative Prediction of Voids Formation in a Growing Nickel Oxide Scale at 1373 K

Voids which form in oxide scales strongly influence the mechanical properties of the scale and the adherence between the metal substrate and the scale. The purpose of this study is to demonstrate a method for quantitative estimation of voids formation in NiO scale, and compare the microstructure of the scale formed on nickel at 1373 K with the estimation. Calculations of ion fluxes and their divergence in NiO scales can predict the annihilation of the oxides which mostly occurs in the vicinity of the metal/oxide interface and the volume fraction of the voids. These predictions are in good agreement with the observed morphology of NiO scale obtained in high temperature oxidation of nickel at 1373 K. [doi:10.2320/matertrans.MER2007122]

Oxygen Transport during the High Temperature Oxidation of Pure Nickel

The high temperature oxidation of nickel has been investigated in air under atmospheric pressure in the temperature range 600–900°C. The oxidation kinetic curves deviate from the parabolic law for temperatures over 800°C. The observation of scale morphologies and the use of two stage oxidation experiments under 16O2/18O2 atmospheres showed that oxygen transport through the NiO scale had to be taken into consideration during the oxidation process. Despite the main outward diffusion of Ni species through the oxide scale, the inward oxygen diffusion at lower temperatures (<800°C) or the oxygen transport, probably as molecular species, via pores or micro-cracks were found to play a major role in the formation of duplex oxide scales, made of small equiaxed oxide grains at the metal/oxide interface overgrown by larger columnar grains at the gas/oxide interface. Oxygen diffusion coefficients into thermally grown NiO scales were determined and compared to the values of Ni diffusion coefficients from the literature.

On the effects of surface coatings on the high-temperature oxidation of nickel

Ni and Ni coated with superficial oxide coatings including SiO 2, CeO 2 and La 2O 3 have been oxidized in the temperature range 500–1200 °C in 10 −4–1 atm oxygen. The oxidation kinetics and the surface kinetics have been determined, and the microstructure and the composition of the oxide coatings and the thermally grown NiO scales have been characterized by a range of different microscopy and spectroscopy techniques. At 800–900 °C, the coatings decrease the oxidation rate by approximately one order of magnitude. The oxide coatings increase the relative growth inside the scale compared to uncoated Ni. Still, the major growth mechanism is governed by outward Ni diffusion, which indicates that the reason for the improved oxidation resistance is due to a decrease in the overall outward flux of Ni across the scales.

On the high-temperature oxidation of nickel

This paper summarizes on some of the extensive experimental data and corresponding models suggested to account for the oxidation mechanism of Ni in the temperature range 500–1400 °C. In addition it reports on in-house experimental data from investigations related to the oxidation of high-purity Ni from 500 to 1300 °C in the oxygen pressure range 1×10 −4–1 atm based on TG, measurements of surface kinetics, two-stage oxidation, scanning electron microscopy, atomic force microscopy, secondary ion mass spectroscopy etc. The main part of this paper focuses on the more complex models suggested to account for experimental observations of the oxidation kinetics and the oxide morphology below 1000 °C.

Electrical properties of the oxide film formed on nickel during high-temperature oxidation

The electrical properties of the oxide film formed from the high-temperature oxidation of nickel have been evaluated using impedance spectroscopy. The impedance measurements were carried out on already oxidised films at temperatures ranging from 100 to 300°C. The conductivity of the oxide film, σ, was obtained as σ=0.19 exp[−0.39 eV/( kT)] Ω −1 m −1, with an activation energy of 0.39 eV close to that of the NiO published in literatures. The dielectric constant ε was found to be nearly independent of temperature with a value of 0.95, significantly lower than that of the bulk NiO. It was believed that some difficulty in achieving a full contact between the electrode and the oxide film during the measurements might have contributed some error in the measurements of both dielectric constant and electrical conductivity. However, the measured relaxation frequency of f R=2.99×10 9 exp[−0.43 eV/( kT)] Hz should be accurate because f R is independent of the specimen geometry and electrode/oxide contact area.

Characterization and growth of oxide films

Surface-analytical techniques are useful to characterize oxide films and to study growth processes on metals and semiconductors. This paper will summarize work at the National Research Council of Canada on the high temperature oxidation of nickel, chromium, FeCrAl alloys (with and without yttrium additions), β-NiAl and silicon. The application of secondary ion mass spectrometry, reflection high energy electron diffraction, and transmission electron microscopy is emphasized. Also considered is the thermal oxidation of III–V semiconductors, indium phosphide and gallium arsenide. X-ray photoelectron spectroscopy provides additional useful information on the chemical composition of the oxides. The often complementary information provided by the various techniques leads to (i) a better understanding of oxidation processes and of oxide growth mechanisms on an atomic scale, (ii) interfacial segregation phenomena, and (iii) the role of reactive elements like yttrium in modifying transport processes in oxides.

High‐temperature oxidation of nickel and chromium studied with an in‐situ environmental scanning electron microscope

AbstractInvestigations of the morphology of metal oxide scales formed at high temperatures in oxidative environments are usually undertaken after exposure of the samples is completed. In this study, an environmental scanning electron microscope (ESEM) was used as a tool for the in‐situ observation of oxide scale formation. Pure nickel and chromium samples were oxidized at a temperature of 973 K in either pure oxygen or water vapour at a pressure of 667 Pa. The evolution of an oxide scale was followed in‐situ for up to 3 h. The morphology of the developing oxide scales was found to be a function of the metal substrate and the gaseous species. The growth mechanisms of the different metal oxide scales are reviewed and related to the analysed in‐situ images. Emphasis is placed on the relationship between oxidation mechanism and scale morphology. Nickel is seen to oxidise by outward diffusion of nickel probably on oxide grain boundaries when exposed to oxygen. Water vapour changes the scale morphology and a duplex‐type scale arises due to preferential overgrowth. The scale which develops due to chromium oxidation in oxygen is a fine‐grained, thin, and dense layer. In contrast, water vapour leads to whisker growth on chromium and an open, felt‐like structure forms. The applicability of the ESEM to the study of such systems is demonstrated, and its limitations are outlined. The results are encouraging examples of the possibilities which the in‐situ ESEM technique possesses.

Microstructural evolution of the oxide film formed during high temperature oxidation of nickel evaluated by means of impedance spectroscopy

Microstructural evolution of the oxide film formed during high temperature oxidation of nickel evaluated by means of impedance spectroscopy

The effect of palladium on the high temperature oxidation of nickel and niobium based superalloys

The effect of palladium on the high temperature oxidation of nickel and niobium based superalloys

ニッケルの高温酸化に及ぼす微量の塩化水素の影響

ニッケルの高温酸化に及ぼす微量の塩化水素の影響

A study of high temperature oxidation of nickel after ion implantation

Both polycrystalline and single-crystal nickel samples were implanted with 100 keV magnesium or krypton to doses of 1 × 10 17 ions cm -2 and oxidized at 700 °C in dry O 2. The effects of implantation on the oxidation properties were studied using Rutherford backscattering spectrometry and channelling, secondary ion mass spectrometry and optical microscopy. Results showed different oxidation behaviour between implanted single-crystal and polycrystalline samples. Post-implantation annealing also changed the oxidation results. A major conclusion is that the chemical effect of implanted magnesium in single-crystal nickel is to retard short-term oxidation at 700 °C after a post-implantation anneal. Possible mechanisms are discussed.

The influence of silicon on the high-temperature oxidation of nickel

An investigation of the oxidation of nickel-silicon alloys has been carried out in order to ascertain the mode of development of partially or fully protective SiO2 layers. The addition of 1% Si has little effect on the oxidation rate of nickel at 1000°C but is sufficient for partial-healing layers of amorphous SiO2 to be established. These layers are incorporated into the inner part of the duplex NiO scale but do not react with the oxide to form a double oxide. Increasing the silicon concentration to 4% or 7% facilitates the development of apparently continuous amorphous SiO2 layers at the base of the NiO scale, resulting in reduced rates of oxidation. However, these layers develop imperfections, possibly microcracks resulting from oxide growth stresses, and are unable to prevent some continued transport of Ni2+ ions into the NiO scale and oxygen into the alloy, particularly for Ni-4% Si. Although the formation of SiO2-healing layers can reduce the rate of oxidation of nickel, they provide planes of weakness that result in considerable damage under the differential thermal contraction stresses during cooling. In particular, severe scale spalling occurs for Ni-4% Si and Ni-7% Si as failure occurs coherently within the SiO2 layer.

High Temperature Oxidation of Nickel at 1373 K in CO ‐ CO 2 ‐ O 2 Atmospheres and Morphology Analysis on Scales

High temperature oxidation of nickel has been studied at 1373 K in atmospheres, at oxygen partial pressures between . The oxidation kinetics have been followed by continuous mass gain measurements using a thermobalance at the oxidation temperature and by measurements of the scale thickness in metallographic cross sections, after cooling. The grain growth of during oxidation has been also investigated. A double‐layered scale is formed near platinum markers, although only a single scale is observed away from the markers. The outer layer is identical in thickness to the scale formed away from markers, and the growth rate is controlled by the outward diffusion of nickel ions. The diffusivity of nickel ions is proportional to at oxygen partial pressures higher than ≈10 Pa. The oxygen pressure dependence of the diffusivity indicates that the predominant defect is a doubly‐charged nickel vacancy. At oxygen partial pressures lower than ≈10 Pa, the oxygen pressure dependence becomes smaller, suggesting extrinsic behavior. The formation of the inner layer is explained, assuming the inward oxygen transport along grain boundaries in the outer layer. The size of the oxide grains, away from markers, is almost the same as that of the nickel substrate, but the oxide near the markers is much smaller. Grains near the markers coarsen, and the cube of the grain size is proportional to time, and the rate constant is also proportional to .These results suggest that grain growth proceeds through the pore drag mechanism, and that the rate is determined by the lattice diffusion of nickel ions.

Kinetics of the oxidation of metals: Parallel circuit for point defects diffusion

A model is proposed for the oxidation of metals including both bulk crystal lattice diffusion and short-circuit diffusion paths. Assuming local equilibrium between point defects in the bulk and in grain boundaries, we obtain an effective parabolic rate constant keff=kbulk [1+θ exp-(ΔH/RT],where ΔH is the enthalpy for the reaction between point defects in the bulk and in short circuits, θ is the fraction of the short-circuit area, and T is temperature. In the case of the high-temperature oxidation of nickel coated with a thin film of vanadium pentoxide, this model yields to a rate law with a critical oxygen pressure Pc. The nickel vanadium oxide located in the short circuits of the growing oxide NiO is liquid below Pc, leading to a rapid short-circuit diffusion. Above this value, a vanadate precipitates and acts as diffusion blocks for migrating Ni ions.

Ceramic Electrolyte Cells in High Temperature Oxidation of Metals

Results on the high temperature oxidation of nickel, as obtained when the metal is the anode of an electrochemical cell with yttria stabilized zirconia (YSZ) as the electrolyte, are presented. Three‐electrode cyclic voltammetry was used to study oxide growth at the interface by a cell system where sintered iron‐wüstite electrodes act both as reference and counterelectrodes. The analysis of the voltammetric curve is carried out by considering that an oxygen producing charge transfer occurs at the interface and that the oxide grows under an external electric field which retards the oxidation kinetics. An approach for calculating the current/voltage curve of the growing oxide is also reported.

Influence of laser surface boronizing on the high-temperature oxidation of nickel

Laser nickel boronizing was performed by simultaneous melting of a predeposited boron powder and the nickel substrate and was shown to lead to the formation of a Ni 3B-rich coating. During oxidation, after a period during which B 2O 3 forms and evaporates, a protective scale of Ni 3B 2O 6 appears, inhibiting the formation of NiO.

Comment on “The mechanism of cavity formation during high temperature oxidation of nickel” (1)

Comment on “The mechanism of cavity formation during high temperature oxidation of nickel” (1)