High-temperature Oxidation Kinetics Research Articles

Improved oxidation resistance of boron nitride nanotubes with protective alumina nano-coatings

Boron nitride nanotubes (BNNTs) are gaining interest for high temperature applications due to their thermal stability at elevated temperatures. Although BNNT temperature limits are well studied, there remains a gap in quantifying the high temperature failure mechanisms and oxidation kinetics. This study characterizes the oxidation mechanisms and kinetics of BNNTs and Al2O3-coated BNNTs, via atomic layer deposition (ALD), at temperatures between 850 and 1000 °C. ALD Al2O3 surface coatings improved BNNT oxidation resistance by over an order of magnitude for coating thicknesses between 7 and 56 nm. However, the improved oxidation resistance of Al2O3-coated BNNTs decayed after prolonged exposure to oxygen at elevated temperatures, gradually reaching the same extent of oxidation as uncoated BNNTs after approximately 200 min at 900 °C. This behavior is attributed to the crystallization of as-deposited amorphous Al2O3 coatings at elevated temperatures leading to densification, cracking, and exposure of BNNTs to the oxidizing environment. While Al2O3 coatings did not completely prevent oxidation, a significant improvement in oxidation resistance was observed, extending the thermal stability of BNNTs.

Surface morphology and oxidation products of DOP-26 iridium alloy upon high-temperature exposure to air

The DOP-26 Ir alloy is employed for fuel sealing in isotope batteries and exhibits superior oxidation resistance at high temperatures under low oxygen conditions. This study investigated the oxidation behavior of the DOP-26 Ir alloy in air, focusing on the correlation between the oxidation temperature and time. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were conducted to examine the phase, morphology, and valence of the alloy upon oxidation. The findings provide a comprehensive understanding of the high-temperature oxidation kinetics of DOP-26 Ir alloy in the air, and these results could potentially be applied to the design and application of radioisotope thermoelectric generators.

A thermogravimetric comparative study of the high temperature steam oxidation of bare and pre-oxidized Zircaloy-4, M5Framatome and Optimized ZIRLO™

For Loss of Coolant Accident (LOCA) analysis, high-temperature oxidation kinetics in steam of Zircaloy-4 and the two Nb-bearing alloys used in French Pressurized Water Reactors (PWRs), M5Framatome11M5 and M5Framatome are trademarks or registered trademarks of Framatome or its affiliates, in the USA or other countries. and Optimized ZIRLO™22Optimized ZIRLO is a trademark or registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners., have been studied using Thermo-Gravimetric Analysis (TGA) technique in the temperature range of 900–1200 °C. A specific test procedure allowing the use of a high steam flow rate and good steam supply to the whole specimen surface, as well as fast heating of the specimen, has been developed. Clean kinetic data, not affected by steam starvation, were obtained on the bare, as-received alloys. For as-received claddings, oxidation kinetics are comparable and close to parabolic for the three alloys at 1100 °C and above. Below 1100 °C, a significant deviation from the parabolic kinetic regime was observed, and M5 Framatome oxidizes slower than Zircaloy-4 and Optimized ZIRLO. Thanks to the fast-heating protocol, the influence of pre-oxidation, simulating corrosion in normal reactor operation, could be investigated, avoiding evolution of the pre-oxidation scale during a slow, long heating phase. Pre-oxidized Zircaloy-4 and M5 Framatome were investigated. A strong protective effect is observed below 1200 °C, while at 1200 °C, the pre-oxidation layer appears to be much less protective, possibly due to the monoclinic to tetragonal zirconia phase transformation.

Enhancing AISI 321 stainless steel's high-temperature oxidation resistance at 600 °C through surface nanocrystallization and pre-oxidation synergy

This study explores the high-temperature oxidation behavior of AISI 321 austenitic stainless steel (ASS) at 600 °C in an Ar-21vol.%O2 atmosphere, considering nanometer-sized surface grain size and pre-oxidation conditions. After initial solution annealing at 1050 °C, AISI 321 ASS samples were water-quenched for homogenized microstructure (SAed samples). Moreover, the surface nanocrystallization of AISI 321 ASS was performed through high-energy shot peening (SNCed samples), reducing the surface grain size to ~75 ± 5 nm. Pre-oxidation occurred at 400 °C for 150 h in Ar-21%O2 for both SAed and SNCed samples. High-temperature oxidation kinetics was analyzed at 600 °C for 150 h using thermal gravimetric analysis (TGA) on pre-oxidized and non-preoxidized SAed and SNCed samples. FESEM/GDOES and GI-XRD revealed that SNCed samples exhibited improved oxidation resistance, showing no Cr depletion in the subsurface oxide layer up to 100 h, and only minor signs after 150 h. Pre-oxidized SNCed samples demonstrated superior oxidation performance, showing no Cr depletion and subsurface Kirkendall pore formation even after 150 h. These findings are coupled with diffusion relationships, and propose potential mechanisms for enhancing the oxidation behavior of pre-oxidized SNCed AISI 321 stainless steel.

Unveiling high-temperature oxidation kinetics of PODE2: Theoretical studies on the H-abstraction, isomerization, and β-dissociation reactions

Polyoxymethylene dimethyl ether (PODEn) is a promising fuel additive to reduce soot emissions. In this work, a theoretical study on the H-abstraction reaction from PODE2 (CH3OCH2OCH2OCH3) by the H atom and CH3 radical, as well as the subsequent isomerization and β-dissociation reactions of PODE2 radicals were carried out. The geometry optimization and frequency analysis for all the stationary points on the potential energy surfaces (PESs) were performed at the M08-HX/6-311+G(2df,2p) level of theory. Single point energies were calculated using the CCSD(T)-F12 method together with the cc-pVTZ basis set. The high-pressure limit rate constants of the H-abstraction reactions from PODE2 were determined through the multistructural canonical variational transition state theory (MS-CVT) with small-curvature tunneling (SCT) correction. The temperature and pressure dependent rate constants for the unimolecular reactions of radicals produced by the H-abstraction reactions from PODE2 were calculated by solving the energy-dependent master equation using the Tsinghua University Minnesota Master Equation (TUMME) program. For the H-abstraction channels of PODE2, reaction pathways initiated via H atom attack are more energetically and kinetically favored over those via CH3 radical within the studied temperature range. The PODE2 radicals with H atoms abstracted from CH3 and CH2 sites are denoted as PODE2A (CH3OCH2OCH2OCH2) and PODE2B (CH3OCH2OCHOCH3), respectively. For unimolecular reaction channels of PODE2A radical, with increased temperatures, the dominant reaction shifts from isomerization to the decomposition process. In the case of the PODE2B radical, the two decomposition channels are consistently preferred across all temperature ranges, resulting in a competitive relationship between them. The thermodynamic properties of PODE2 and its associated radicals were calculated using the isodesmic reaction method in conjunction with multistructural torsional partition functions. Based upon the newly calculated rate constants and existing literature models, an updated kinetic model describing PODE2 combustion chemistry is developed in this work. This model incorporates the latest findings and contributes to a more comprehensive understanding of the oxidation and auto-ignition characteristics of PODE2.

Foundational Fuel Chemistry Model 2 – iso-Butene chemistry and application in modeling alcohol-to-jet fuel combustion

The Hybrid Chemistry (HyChem) approach is applied to model the combustion chemistry of Gevo’s alcohol-to-jet (ATJ) fuel, a conventional Jet A fuel, and their blends. The focus of the current study is on the foundational fuel chemistry submodel in the HyChem approach. Specifically, the newly developed Foundational Fuel Chemistry Model 2 (FFCM-2) is used as the base model for describing the high-temperature pyrolysis and oxidation kinetics of hydrogen, carbon monoxide, formaldehyde, and C1-4 hydrocarbons. Key issues addressed and resolved include difficulties of a previous kinetic model in accurately predicting the pyrolysis kinetics and combustion properties of iso-butene, which is the key intermediate in the combustion of the ATJ fuel. Additionally, we show that FFCM-2, being fully assessed for its kinetic uncertainty, enables us to quantify the uncertainties of the HyChem models of both real fuels.

Effect of Sc2O3 doping on YSZ TBCs: Morphologies, phase composition, mechanical properties, and high-temperature oxidation resistance

Y2O3 stabilized ZrO2 thermal barrier coatings (YSZ TBCs) and Sc2O3 and Y2O3 co-stabilized ZrO2 thermal barrier coatings (ScYSZ TBCs) were prepared by atmospheric plasma spraying technology, and then a high-temperature oxidation experiment was carried out at 1100 °C. Whereupon the morphologies, phase composition, and mechanical properties of YSZ ceramic coating and ScYSZ ceramic coating after different high-temperature oxidation time, as well as the high-temperature oxidation resistance of YSZ TBCs and ScYSZ TBCs, were comparatively studied. The results showed that after high-temperature oxidation, ScYSZ ceramic coating presented slighter cracking and exhibited better sintering resistance. After high-temperature oxidation, the phase composition of both YSZ ceramic coating and ScYSZ ceramic coating was still a single T' phase, and their interplanar spacing became larger; nevertheless, the interplanar spacing of ScYSZ ceramic coating was smaller than that of YSZ ceramic coating. After high-temperature oxidation, ScYSZ ceramic coating had higher hardness, smaller elastic modulus, and smaller fracture toughness. In addition, ScYSZ TBCs exhibited better high-temperature oxidation resistance according to the morphology, equivalent thickness, high-temperature oxidation kinetics, and high-temperature oxidation thermodynamics of TGO.

Strong correlation between high temperature oxidation resistance and nitrogen mass gain during near alpha titanium alloys exposure in air

Nitrogen is known to play a role in the oxidation of titanium and titanium alloys in air. This paper shows the strong correlation between the high temperature oxidation kinetics of eight near-alpha titanium alloys, in the class of Ti6242S, exposed for 3000 h in air at 650 °C. Nuclear reaction analysis (NRA) was used to quantify and locate the nitrogen inside the material. An excellent linear correlation between the total mass gain measured by gravimetry and the nitrogen mass gain measured by NRA is revealed: less the alloys oxidize, more the nitrogen in involved in the oxidation process.

High-temperature oxidation kinetics of a metastable dual-phase diboride and a high-entropy diboride

The processing of multicomponent (Ti0.25V0.25Zr0.25Hf0.25)B2 ultra-high temperature hexagonal transition metal diboride in dual-phase and single-phase microstructures and investigation of oxidation behavior in the air at 1000 and 1500 °C are reported. The dual-phase diboride is a metastable phase composed of Hf-Zr-rich and Ti-V-rich phases that undergo phase transformation to a single-phase high-entropy diboride after thermal annealing. At 1000 °C, a B2O3 layer was formed on the material's surface, and the oxidation kinetics followed a para-linear behavior. At 1500 °C, a porous oxide layer was formed, facilitating oxygen diffusion and reaction with the diboride, resulting in linear oxidation kinetics. The prediction of the lifetime of the materials during high-temperature oxidation suggested that the high-entropy material outperforms the dual-phase diboride, making it most suitable for related applications. The superior performance of the high-entropy single-phase diboride was associated with the high-entropy and sluggish diffusion effects.

Mechanism and kinetics of high-temperature oxidation of medium- and high-entropy carbides in air

Medium- and high-entropy carbides (MECs and HECs) have a wide range of advanced applications and, in many cases, outperform monocarbides. However, the behavior, oxidation mechanisms, and factors defining oxidation resistance of some popular HECs at high temperatures have not been studied in detail yet. In this study, the oxidation behavior of MEC and HECs including (Ta,Ti,Nb,Zr)C, (Ta,Ti,Nb,Zr,Mo)C, (Ta,Ti,Nb,Zr,Hf)C, and (Ta,Ti,Nb,Zr,W)C was investigated under both non-isothermal and isothermal conditions at temperatures up to 1200 °C, and a possible oxidation path was described. It was found that under non-isothermal heating conditions, the oxidation of HECs occurred in three stages, each governed by first-order chemical reactions, and was limited by the formation of ZrO2, Me2Me6O17, and MeMe2O7 oxides, respectively. In the case of isothermal heating, the oxidation of (Ta,Ti,Nb,Zr)C, (Ta,Ti,Nb,Zr,Mo)C, and (Ta,Ti,Nb,Zr,Hf)C follows a logarithmic law and was limited by the formation of a protective Me2Me6O17 layer. In contrast, isothermal oxidation of (Ta,Ti,Nb,Zr,W)C followed a linear law due to the formation of volatile WO3. The results of the study have a high potential for practical application for the production of HEC ceramics for various high-temperature purposes and could be used for further understanding of functional characteristics and development of the new ceramic compositions.

Oxidation and Electrical Property Studies on Ferritic Steels as Potential Interconnects in Electrochemical Devices for Energy Conversion

This work presents the results of oxidation studies on commercially available Nirosta 4016/1.4016 ferritic steel, which contains 16.3 wt.% chromium, as well as the electrical properties of steel/scale layer systems in order to determine the usefulness of this steel for constructing metallic interconnects in solid oxide fuel cell (SOFC) and solid oxide electrolyzer cell (SOEC) stacks. The E-Brite ferritic steel, consisting of up to 26 wt.% chromium, was chosen as a reference material. High-temperature isothermal oxidation kinetics studies were carried out on both steels at 1073 K for 255, 505, 760 and 1010 h in air atmosphere. These conditions are representative of those present in the cathode compartment of a SOFC and the anode compartment of a SOEC. Area specific resistance (ASR) measurements were performed on steel/scale layer systems, obtained after the previous oxidation of both steels in the above-mentioned conditions, in the air in the temperature range of 573–1073 K using the pseudo-DC four-probe method. On the basis of these studies, complemented by morphology observations, as well as chemical and phase composition analysis of the oxidation products, the usefulness of Nirosta 4016/1.4016 ferritic steel for manufacturing interconnects in energy conversion electrochemical devices operating at 1073 K was confirmed.

Experimental and kinetic modeling study of the low- temperature and high-pressure combustion chemistry of straight chain pentanol isomers: 1-, 2- and 3-Pentanol

Pentanols have received significant attention as a potential alternative fuel or fuel additive owing to their high energy densities and low vapor pressure. The development of robust chemical kinetic models for alternative fuels which can provide accurate and efficient predictions of combustion performance across a wide range of engine relevant conditions is important in developing cleaner, more efficient combustors. Although the high temperature oxidation kinetics of pentanol isomers has been researched considerably, their low temperature combustion chemistry needs further investigation. While previously proposed low temperature mechanisms for 1-pentanol based on analogy and rate rules need further refinement, the low temperature oxidation kinetics of 2-pentanol and 3-pentanol has not been studied previously by any means, experimentally or theoretically. A newly developed kinetic mechanism is presented in this work for the three straight chain pentanol isomers: 1-, 2- and 3-pentanol. Low temperature kinetics is based on a recent study by Lockwood et al., 2022 [20] involving theoretical calculations at the CCSD(T)/cc-pV∞Z level of theory for the oxidation pathways involving alcohol peroxy radicals. Rate of production analyses performed in this study highlight the importance of the newly added pressure-dependent reactions of the α-alcohol peroxy radical forming an RȮ2 adduct. While the α-alcohol fuel radical reacts with O2 to directly decompose via a chemically activated pathway at low pressures, the formation of the RȮ2 adduct is favored at high pressures. The detailed model is comprehensively validated against new ignition experiments at low temperature and high pressure, together with the wide range of data available in the literature. Both qualitative and quantitative predictions of the experimental data using the proposed kinetic model are satisfactory for all three pentanol isomers studied here.

High temperature oxidation kinetics of Fe-10Al-4Cr-4Y2O3 ODS alloy at 1200–1400 °C

The high temperature oxidation kinetics of the Fe-10Al-4Cr-4Y2O3 ODS alloy (FeAlOY) with excellent creep and oxidation resistance at temperatures exceeding 1100 °C is investigated at 1200 °C, 1300 °C and 1400 °C. A compact layer with columnar grain microstructure consisting of α-Al2O3 and YAG (Y3Al5O12) grains is grown at the surface. The oxidation resistance of FeAlOY is compared with other Fe-Cr-Al alloys. The oxidation mechanism and roles of individual elements in the FeAlOY are discussed in detail. Despite containing 3–4 times less Cr, the FeAlOY has the same or even better oxidation resistance when compared with classical Fe-Cr-Al alloys.

High Temperature Oxidation Behavior of New Martensitic Heat-Resistant Steel

The research focuses on the high temperature oxidation resistance of martensitic heat-resistant steel. A new type of martensitic heat-resistant steel was developed with the addition of Al and Cu, and the oxidation behavior of the new martensitic heat-resistant steel at 650 °C and 700 °C was analyzed. The high temperature oxidation kinetics curves of new martensitic heat-resistant steel at 650 °C and 700 °C were determined and plotted by cyclic oxidation experiment and discontinuous weighing method. XRD technique was applied to qualitatively analyze the surface oxide of the material after oxidation. The surface and cross-section morphology of the material were observed by field emission scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), and the oxidation mechanism at high temperature was analyzed. The results show that the oxide film can be divided into two layers after oxidation at 650 ºC for 200 h. The outer oxide film is mainly composed of Fe and Cu oxides, and the inner oxide film is mainly composed of Al2O3, SiO2 and Cr2O3. After oxidation at 700 ºC for 200 h, the outer layer is mainly composed of Fe, Cu, Mn oxides, and the inner layer is mainly composed of Cr, Al and Si oxides. The addition of a small amount of Cu promotes the diffusion of Al and Si elements, facilitates the formation of Al2O3 and SiO2, and improves the high-temperature oxidation resistance of martensitic heat-resistant steel.

Kinetic Study of Oxide Growth at High Temperature in Low Carbon Steel

High-temperature surface oxidation kinetics were determined for low-carbon steel using a Joule heating device on hollow cylindrical specimens. The growth of the oxide layer was measured in situ between 800 and 1050 ∘C under isothermal oxidation conditions and in an air laboratory atmosphere (O2 = 20.3% and humidity = 42%). Through a laser and infrared measuring system, the expansion and temperature were measured continuously. From the data acquired, the oxidation kinetic parameters were obtained at different temperatures with a parabolic-type growth model to estimate the rate of oxide layer generation. The convergence degree of the data fitted with the oxidation model was acceptable and appropriately correlated with the experimental data. Finally, comparisons were made between the estimated kinetic parameters and those reported in the literature, observing that the activation energy values obtained are in the range of the reported values.

Technical Note: Effect of High-Current Pulsed Electron Beam Processing of Zr-1%Nb Alloy on Its Oxidation Kinetics at 1,200°C in Air and Steam

The paper reports the effect of high-current pulsed electron beam (HCPEB) processing of the Zr-1%Nb alloy as one of the most widely used in water-cooled nuclear reactors, based on the kinetics of its oxidation at 1,200°C in air and steam (these conditions are typical for potential loss-of-coolant accidents). It was shown that HCPEB processing caused a change in the surface morphology of the samples. In particular, craters with diameters of about 100 μm were found on the modified surfaces. They had initiated at an energy density of 5 J/cm2 and were characterized by relevant reliefs with microcracks. After HCPEB processing at 10 J/cm2, the craters were deeper with fractured surface layers. In addition, a pronounced surface relief corresponding to quenched martensitic microstructures was observed on the modified sample surfaces that had formed due to high heating and cooling rates. Due to sufficient degradation of the sample surfaces after HCPEB processing at 10 J/cm2, the kinetics of high-temperature oxidation was estimated only for the as-received samples and ones treated at 5 J/cm2. It was found that the as-received samples showed slightly greater weight gain levels in both air and steam environments, which fully correlated with the thickness ratio of the oxide, α-Zr(O), and prior-β layers. These phenomena and further research directions were discussed.

BEHAVIORS OF OXIDATION AND DECARBURIZATION ON SURFACE OF HIGH-CARBON STEEL WIRE RODS

The quality of high-carbon wire rods is subject to high requirements in terms of the size of the decarbonized layer, the amount and composition of the scale formed by the interaction of the oxidizing furnace atmosphere with the surface of steel. In this connection, studies of the kinetics of high-temperature oxidation of high-carbon steel are of great practical importance, both in the development of new and adjustment of existing modes of heat treatment of steel. The results of experimental studies of hightemperature oxidation and decarburization of the surface of high-carbon steel grade 80P on the synchronous thermal analysis device STA 449 F3 Jupiter presented. Temperature intervals of intensification of scale formation and decarburization of the surface in various media (weakly oxidizing and oxidizing) have been established. Phase transformations in high-carbon steel grade 80P have been studied by differential scanning calorimetry and the temperatures of the beginning and end of the formation of homogeneous austenite during heating have been established. It was noted that in the range of heating temperatures of steel 720‒950°C, along with phase transformations, the intensification of the processes of scale formation and depletion of the surface layers with carbon begins. The exponential dependence of steel loss on the heating temperature of the sample was obtained by thermogravimetric analysis. It was shown that the oxidation rate of the surface increases by 3 times with an increase in the temperature of the workpiece from 900 to 1000°C, and up to 1200°C ‒ by 8 times. It was noted that the temperature at which the oxidation rate of steel is minimal in the temperature range from 900 to 1000 °C is about 929 °C, in the range of 1100‒1250°C ‒ 1157°C. The obtained results can be used to select the main technological parameters of the heat treatment mode of wire rods made of 80P steel, which ensure the formation of a minimum amount of easily removed scale on the metal surface.

High-Temperature Surface Oxide Growth Kinetics of Al–Si–Zr Bulk Alloys and Ribbons

A typical modification technique of the functional properties of Al–Si based alloys is the addition of some third element in trace level. In the present work, ternary Al–Si–Zr bulk and ribbon alloys have been prepared. The kinetics of high-temperature surface oxidation has been studied by thermogravimetric method. It was found that at the start of the experiment the chemical reaction velocity is rate-controlling while for longer times the (oxygen) diffusion is the rate-controlling process. Activation energy of the two stages of oxidation has been obtained. Additional studies such as thermochemical analysis, optical and electron microscopy, and microhardness tests have been done.

Thermochemical Laser-Induced Periodic Surface Structures Formation by Femtosecond Laser on Hf Thin Films in Air and Vacuum.

Thermochemical laser-induced periodic surface structures (TLIPSS) are a relatively new type of periodic structures formed in the focal area of linear polarized laser radiation by the thermally stimulated reaction of oxidation. The high regularity of the structures and the possibility of forming high-ordered structures over a large area open up possibilities for the practical application for changing the optical and physical properties of materials surface. Since the mechanism of formation of these structures is based on a chemical oxidation reaction, an intriguing question involves the influence of air pressure on the quality of structure formation. This paper presents the results on the TLIPSS formation on a thin hafnium film with fs IR laser radiation at various ambient air pressures from 4 Torr to 760 Torr. Despite the decrease in the oxygen content in the ambient environment by two orders of magnitude, the formation of high-ordered TLIPSS (dispersion in the LIPSS orientation angle δθ < 5°) with a period of ≈700 nm occurs within a wide range of parameters variation (laser power, scanning speed). This behavior of TLIPSS formation is in agreement with experimental data obtained earlier on the study of the kinetics of high-temperature oxidation of hafnium at various oxygen pressures.

Data analytics approach to predict high-temperature cyclic oxidation kinetics of NiCr-based Alloys

Although of practical importance, there is no established modeling framework to accurately predict high-temperature cyclic oxidation kinetics of multi-component alloys due to the inherent complexity. We present a data analytics approach to predict the oxidation rate constant of NiCr-based alloys as a function of composition and temperature with a highly consistent and well-curated experimental dataset. Two characteristic oxidation models, i.e., a simple parabolic law and a statistical cyclic oxidation model, have been chosen to numerically represent the high-temperature oxidation kinetics of commercial and model NiCr-based alloys. We have successfully trained machine learning (ML) models using highly ranked key input features identified by correlation analysis to accurately predict experimental parabolic rate constants (kp). This study demonstrates the potential of ML approaches to predict oxidation kinetics of alloys over wide composition and temperature ranges. This approach can also serve as a basis for introducing more physically meaningful ML input features to predict the comprehensive cyclic oxidation behavior of multi-component high-temperature alloys with proper constraints based on the known underlying mechanisms.