Internal Oxidation Research Articles

Effect of α-to-γ transformation on internal oxidation in FeCr-base alloys in dry and wet gases

Aging of asphalt binder is a main cause of damage in asphalt mixture during the long-term service. However, the correlations between decrease of rheological properties and fatigue damage at microscale are not clear especially for highly-aged materials. In this work, diverse rheological parameters have been utilized to characterize the linear viscoelastic (LVE) and non-linear viscoelastic (NLVE) behavior of asphalt binders. Microscale structure migration was correlated with rheological properties characterized by the optimal Glover-Rowe parameter (GRP) after aging ratio comparison. Small molecules were coalesced into long carbon-chain structures while internal chemical bonds produced during aging. Specific functional groups are oxidized into oxides such as sulfoxides. Sf and Nf from simplified-viscoelastic continuum damage (S-VECD) model were gradually reduced by conversion of micro-molecules. The internal micromolecular polymerization and oxidation caused by aging will potentially lead to the weakening of rheological properties. The objectives of the research are to obtain typical LVE and NLVE parameters via comparing aging sensibility, and link the internal microscale structure to rheological properties.

This study investigates the effects of ultrasonic surface rolling process (USRP) parameters—static load, indentation depth—on the surface integrity, mechanical properties, and high-temperature oxidation properties of laser-clad NiCrAl coatings. Comprehensive experimental results demonstrate that USRP treatment effectively eliminates surface cracks and significantly enhances surface integrity. The process simultaneously improves mechanical properties, with microhardness increasing by 24.6% due to grain refinement-induced strengthening and elevated dislocation density. Under constant preload, increasing the ultrasonic rolling indentation depth effectively transforms residual tensile stress into beneficial compressive stress (from +69.8 MPa to −1315.3 MPa), with higher preload further enhancing this effect. Moreover, USRP-treated coatings achieve complete oxidation resistance at elevated temperatures by forming a denser and more continuous oxide layer while effectively suppressing internal oxidation, resulting in markedly improved high-temperature oxidation performance. Quantitative analysis confirms that the enhancement in surface mechanical properties is primarily attributed to microstructural refinement and dislocation strengthening mechanisms.

Simulation study of channel structural design for direct internal reforming methane solid oxide fuel cell

In this study, the high-temperature oxidation resistance of six variants of S30403 austenitic stainless steel, differing in V content, was investigated at 700 and 800 °C under air atmosphere using the static discontinuous oxidation weight gain method. The results demonstrate that V exhibits a negative impact on the high-temperature oxidation resistance of austenitic stainless steel at 700 and 800 °C. As the V content in the steel rises, the oxidation rate also tends to elevate, with the highest values recorded at 0.1138 g m−2 h−1 at 700 °C and 0.4707 g m−2 h−1 at 800 °C, respectively. The V element in the V-containing steel is uniformly distributed in the matrix and oxide film, which promotes the internal oxidation of Cr and Si elements. The content of Cr2O3 and SiO2 oxides on the surface decreases, and the Mn and Fe elements diffuse outward through the oxide film to form spinel structure MnCr2O4. The oxide film on the steel’s surface experiences a gradual decline in its continuity and compactness, which consequently leads to a decrease in the steel’s high-temperature oxidation resistance.

A self-catalyzed phototandem trifluoromethylation/cyclization of N-methacryloyl aldehyde hydrazones with trifluoromethyl thianthrenium triflate (TT-CF3+OTf-) in ethanol has been developed. This method provides access to various trifluoromethylated pyrazolin-5-ones under mild, exogenous catalyst- and organic oxidant-free conditions. The readily prepared TT-CF3+OTf- serves a dual role as both the CF3 radical source and an internal oxidant, greatly simplifying the reaction system. The thianthrene byproduct is efficiently recovered and reused, enhancing economic viability and reducing chemical waste, in line with green chemistry principles.

Metal-catalyzed C(sp3)-N coupling remains a formidable synthetic challenge, especially with alkyl electrophiles, due to competing pathways such as slow oxidative addition, β-hydride elimination, and alkyl isomerization. While alkyl halides are commonly used, their limitations have spurred interest in alternative coupling partners. Alkyl boronic pinacol esters (Bpins), though stable and widely accessible, are underutilized in C-N coupling due to their poor transmetalation reactivity and susceptibility to protodeborylation and isomerization. Here, we report a dual catalytic strategy that merges copper catalysis with photocatalytically enabled amino radical transfer (ART) to achieve C(sp3)-N coupling of nonactivated alkyl Bpins under mild, redox-neutral conditions. Readily available morpholino benzoate acts both as an aminyl radical precursor and as an internal oxidant, circumventing the need for external oxidants and enabling efficient coupling between two nucleophiles. This strategy delivers a general and regioselective platform for C(sp3)-N bond formation, accommodating a broad array of amines (12 classes), including indoles, indazoles, pyrazoles, anilines, and sulfonamides. The synthetic utility is further exemplified through the late-stage functionalization of complex drug molecules and a one-pot hydroamination of alkenes.

Aziridination of olefins using nonprotected primary amines as nitrogen donors under oxidative conditions is highly desirable but poses challenges due to the incompatibility of nonprotected amines with oxidants. To address this issue, a strategy to leverage an internal oxidant is proposed. This method enables nucleophilic α- and β-additions of amines to conjugated hydroxamates, allowing for the assembly of complex aziridines from simple and safe building blocks. Benefiting from this internal oxidant concept, electron-rich anilines are directly employed to access N-aryl aziridines. Beyond aziridination, olefin 1,2-diamination can also be achieved when secondary amines are used. Mechanistic studies suggest that an α-lactam intermediate is involved in this aziridination to enable the redox-transposition. In a broader context, this transformation represents a novel type of nucleophilic α-addition, which is rare compared to the more common β-addition (the Michael addition).

This study investigates the effect of surface oxide control on the phosphatability of ultra-high-strength steel (UHSS) for automotive applications. Surface oxides were manipulated by adjusting the dew point to -50 °C and 0 °C during the annealing process, and the corresponding changes in phosphating behavior were examined. The surface characteristics of the samples were analyzed using X-ray photoelectron spectroscopy (XPS) and field-emission transmission electron microscopy (FE-TEM), while the phosphatability of the samples was evaluated through electrochemical measurements. The sample annealed at a dew point of -50 °C formed continuous Si and Mn oxide films (~10 nm), which significantly suppressed the phosphatability. In contrast, when annealed at 0 °C, internal oxidation occurred along the grain boundaries to a depth of about 3 μm, resulting in the formation of discontinuous Si and Mn oxides on the surface, which greatly enhanced phosphatability. This difference was also supported by OCP measurements: the -50 °C specimen showed a gradual increase in potential, whereas the 0 °C specimen rapidly reached -0.59 V and then stabilized. The findings of this study demonstrate that optimizing the annealing atmosphere provides an effective approach to enhance the phosphating performance of UHSS without the need for additional surface treatments.

ConspectusMethods that enable the selective functionalization of C-C bonds offer unique opportunities for the skeletal diversification of complex molecules and provide access to unique structures without the need for de novo synthesis. While considerable advances have been made in transition-metal-based approaches, much recent work has focused on alternative strategies for C-C bond cleavage enabled by transient free radicals. In particular, alkoxy radicals derived from simple alcohols are known to significantly destabilize adjacent C-C bonds, enabling spontaneous cleavage to eject a carbon-centered radical and afford carbonyl products via β-fragmentation. While this reactivity has long been recognized, its applications in synthesis have been limited, in part, by the challenges associated with generating the key alkoxy radical intermediates. The high bond dissociation free energies (BDFEs) of aliphatic alcohol O-H bonds (∼105 kcal/mol) preclude direct homolytic activation by hydrogen atom transfer, and most established strategies rely instead on stoichiometric prefunctionalization of the O-H bond. These approaches often further limit the scope of amenable chemistries that can be applied for postcleavage alkyl radical functionalization. Methods that could overcome these constraints have considerable synthetic potential, enabling straightforward access to reconfigured carbon frameworks from an abundant class of starting materials, as well as modular opportunities for radical functionalization. In this Account, we present our efforts toward the development of proton-coupled electron transfer (PCET) as a general mechanism for alkoxy radical generation from simple alcohols. In turn, this advance enabled us to develop a suite of novel methods for editing complex carbon frameworks via the cleavage and functionalization of C(sp3)-C(sp3) bonds. We first discuss the development of catalytic ring-opening isomerization reactions of cyclic benzylic carbinols to access linear aryl ketone products through a redox-relay approach. In these reactions, single electron oxidation of the substrate arene by an excited-state Ir(III) photocatalyst generates an arene radical cation that serves as an internal oxidant for an intramolecular PCET event, furnishing the alkoxy radical intermediate. This intermediate then undergoes C-C β-scission to provide the isomerized linear ketone products. We next present the discovery of an improved catalytic system for the direct activation of simple aliphatic alcohols. We then apply these chemistries for the light-driven depolymerization of lignin biopolymers, commercial phenoxy resins, hydroxylated polymers, and thiol epoxy thermosets. Notably, many of these redox isomerization reactions are thermodynamically unfavorable, providing isomerization products that are thermodynamically less stable than their corresponding starting materials. We then discuss the application of O-H PCET for the reconfiguration of saturated carbocyclic frameworks to provide expanded and contracted carbocyclic products. Applications of this reconfiguration strategy toward the 1,3-alkyl rearrangement of linear alcohols are also presented. Lastly, we discuss a method for the peripheral-to-core transposition of amine groups of saturated cyclic amino alcohols to access nitrogen-containing heterocyclic products. Taken together, these examples highlight how excited-state PCET can be leveraged for the catalytic generation of high energy O-centered radicals for regioselective C-C bond cleavage and enables the direct reconfiguration of complex carbon frameworks.

The purpose of this research was to determine the properties of humic acids isolated from soil samples taken from a 40-year static experiment—the experimental factors were fertilization with manure (30 t ha−1; FYM) and nitrogen at rates of 40, 60 and 120 t ha−1. From the soil samples (Luvisol), humic acids (HAs) were extracted and the following were determined: elemental composition, hydrophilic and hydrophobic properties and spectrometric properties in the UV–VIS and IR range. The HAs of the soil fertilized with manure and N compared to the HAs of the soil fertilized with N (without manure) were characterized by a higher degree of aliphaticity and, consequently, a higher share of hydrophilic fractions and lower values of internal oxidation. Based on the spectrometric parameters, it was indicated that the HA particles of the manure-fertilized soil are characterized by a higher share of undecomposed lignin fragments, a lower degree of humification and at the same time, a higher susceptibility to oxidation. The obtained relationships showed that the aromaticity and hydrophobicity of the HA molecules of the manure-fertilized soil can be increased at certain N doses (60 and 120 t ha−1), which is particularly important in terms of the role that humic substances play in carbon sequestration.

Effect of Al on Surface Oxide Scale and Internal Oxidation in Hot-Rolled Coil of Fe–Mn–Si-Based Alloys

Abstract The SiO2 thermally grown oxide (TGO) is a life‐limiting factor for environmental barrier coatings (EBCs). EBCs in aeroengines face a variety of operating temperatures so the resulting effect on SiO2’s crystallinity and growth are necessary to better understand EBC failure. Here, the temperature effect of steam oxidation on SiO2 crystallinity, SiO2 growth and silicon bond coat residual stress are investigated by coupling electron microscopy image analysis and Raman spectroscopy stress mapping. This novel characterization approach offers a new perspective for microstructure and stress evolution in EBCs. From this study, image analysis reveals the internal oxidation of SiO2 on air plasma spray splat boundaries and the faster growth of an amorphous SiO2 compared to β‐cristobalite SiO2. Consequently, stress mapping characterizes the greater inhomogeneity in the residual stress distribution in the silicon bond coat with an amorphous SiO2 and the effect of cracking on stress relief. As a result, silicon bond coat cracks near amorphous SiO2 TGO are expected to result in an EBC with a reduced lifetime.

Abstract Three different AgZnO contact materials with varying In2O3 contents were prepared using internal oxidation. The electrical life, welding force, arc energy, and arc ignition time of these three materials under AC220 V and 20 A resistive load conditions were tested using simulated electrical performance testing equipment. The test results and the arc erosion morphology on the contact surface after the test were analyzed. Research has found that when the In2O3 content is 0-3%, as the In2O3 content increases, the arc energy and arc time of the contact material gradually decrease, and the anti-welding performance gradually increases. Although it may cause changes in the physical properties of the material, it greatly helps the anti-welding performance of the material, thus reducing its impact on the material’s performance. The addition of In2O3 is beneficial for suppressing material transfer and splashing. When the amount of In2O3 added is 3%, the surface burn morphology and other electrical performance parameters of the material are better.

Unveiling the internal oxidation mechanism in Cantor alloys: Role of Laves phase and Ta variations

In this study, an innovative internal oxidation-powder metallurgy combined process was employed to controllably generate nano-sized Cr2O3 reinforcing phases within the Cu matrix. The Cu/Cr2O3 composites were successfully fabricated using the hot-press sintering (HP) method, and a systematic comparison was made between the microstructure and mechanical properties of composites prepared by internal oxidation and external addition methods. The results show that internal oxidation primarily occurs during the sintering process rather than ball milling. Compared with external addition, the internal oxidation method effectively prevents particle aggregation and achieves a uniform distribution of Cr2O3 particles in the Cu matrix. When the Cr content reaches 5 wt.%, the Cu-5%Cr composite exhibits optimal mechanical properties, with a yield strength of 282.7 MPa and ultimate tensile strength of 355 MPa, representing increases of 43% and 34% over pure copper, respectively, while maintaining an elongation of 12.6%. The Cr2O3 particles generated via internal oxidation enhance their strength through Orowan strengthening and dislocation pinning, thereby significantly improving mechanical performance without compromising plasticity. This research provides a novel process optimization approach for developing high-performance dispersion-strengthened copper matrix composites.

Investigation of the Internal Oxidation and Hot Rolling Deformation Behavior in Ni36

The oxidation behaviour of binary Ni-(3, 5)Al and ternary Ni-(3, 4, 5)Al-(15, 20)Cr alloys (all in wt%) was investigated in both Ar-20%O2 (dry oxygen) and Ar-20%O2-20%H2O (wet oxygen) at 750 °C. For Ni-3Al alloy, an external NiO and an internal oxidation zone (IOZ) were formed with an enhanced thickening kinetics in wet oxygen. Increasing Al to 5 wt% led to a partial protection of the surface by a thin alumina scale, together with non-protective NiO and IOZ as that for Ni-3Al. Adding Cr into Ni–Al alloys significantly increased oxidation protection. In dry oxygen, all ternary alloys formed mainly a thin protective alumina scale. This protective effect was significantly reduced in the presence of water vapour. For Ni-(3, 4)Al-15Cr, a complex multi-layered oxide structure was observed, with an external NiO, an inner oxide layer with a chromia band at the bottom, and an IOZ with alumina precipitates. Further increasing Cr to 20 wt% led to a dominant chromia band formation in the inner oxide region. For high Al (5 wt%) ternary alloys, a protective alumina scale was formed in most of the surface area. Oxide characterisation revealed that this thin layer of alumina was α-Al2O3. The effects of water vapour and alloy composition on oxide formation were discussed based on classic diffusion theory and oxidation kinetic analysis.

The samples of experimental dispersion-hardened aluminum matrix alloys obtained by internal oxidation are studied. The influence of the content of different chemical elements in the structure of the material on the microhardness of billets made of hardened aluminum alloys is established. Keywords aluminum alloy, testing, hardness, microhardness, copper, magnesium, iron, silicon mdsov@knastu.ru, mitya.valko@mail.ru, mrmylnikov@mail.ru

Inhibiting internal oxidation of lean FeAl alloys through minor addition of Si and preheating in H2