Reoxidation Process Research Articles

Binder-enhanced reversible photochromic films by tungsten oxide hybrid composites for advanced applications

In this study, we developed binder-enhanced reversible photochromic tungsten oxide (WO3) films for advanced applications. Expanding on previous research, we used tungsten oxide hybrid composites as the base material and incorporated various binders, specifically polyethylene glycol (PEG), polysorbate 80 (PS 80), and carboxymethyl cellulose (CMC), to evaluate their effects on reversible photochromic reactions. Our experiments demonstrated that the inclusion of CMC significantly improved the photochromic properties and exhibited the fastest reversible reactions when compared to PEG and polysorbate 80. This enhancement is attributed to the high density of hydroxyl groups and the network structure of CMC, which facilitate efficient proton transfer and oxygen permeability, both crucial for the reoxidation process in WO3. Density functional theory (DFT) calculations supported these findings by indicating that CMC has a suitable bandgap and electron mobility, which enhance charge injection and transport. Additionally, the fabricated films showed consistent and stable performance under both heat treatment and natural ambient conditions. These results underscore the potential of CMC as an effective binder for developing high-performance, reversible photochromic films suitable for applications in smart windows, displays, and optoelectronic devices.

Reestablishment of dielectric and nonlinear properties for Bi3+ doped CaCu3Ti4O12 ceramics prepared by reduction-reoxidation method

Multilayer ceramics with base metal internal electrodes should be prepared through reduction sintering to avoid the oxidation of the electrodes, followed by a reoxidation process. In this study, Ca1-xBixCu3Ti4-x/4O12 + 0.03 BN ceramics were fabricated using the reduction-reoxidation method and the reestablishment of dielectric and nonlinear characteristics was investigated. It was observed that the dielectric and nonlinear properties depended crucially on the grain size and the second phases at the grain boundaries. The reoxidation behavior was remarkably improved when grain growth was suppressed and second phases were introduced. Optimal electrical properties were obtained for samples with x = 0.1 sintered at 1050 °C and reoxidized at 800 °C. The dielectric loss decreased to a value of about 0.14, while the permittivity remained a relatively large value of about 9.9 × 103 at 103 Hz. Additionally, the nonlinear coefficient and breakdown field were improved to a value of 2.2 and 981.8 V/cm, respectively. This study illustrates an efficient approach to enhance the reestablished dielectric and nonlinear properties for Bi3+ doped CaCu3Ti4O12-based ceramics fabricated through the reduction-reoxidation method.

Reduction behaviour in neodymium doped ceria

Doped cerium oxides are technologically relevant materials and used as electrolytes in intermediate temperature solid oxide fuel cells. An important issue for these materials is the reduction of ceria at low oxygen partial pressures which leads to mixed ionic electronic conduction. In the present work, reduction behaviour in Ce0.8Nd0.2O1.9-δ is examined under inert and strongly reducing conditions. Even under inert conditions, ca. 3.5 % of the Ce is redox active up to around 800 °C, which appears to be correlated with non-linear behaviour in the Arrhenius plot of conductivity and thermal expansion of the lattice. Under more strongly reducing conditions, a secondary partial reduced phase is formed related to triclinic Ce11O20, which introduces significant electronic conductivity into the system. The dynamics of the re-oxidation process are examined using X-ray powder diffraction and electrochemical impedance spectroscopy.

Sulfidation−reoxidation enhances heavy metal immobilization by vivianite

Iron minerals in nature are pivotal hosts for heavy metals, significantly influencing their geochemical cycling and eventual fate. It is generally accepted that, vivianite, a prevalent iron phosphate mineral in aquatic and terrestrial environments, exhibits a limited capacity for adsorbing cationic heavy metals. However, our study unveils a remarkable phenomenon that the synergistic interaction between sulfide (S2−) and vivianite triggers an unexpected sulfidation−reoxidation process, enhancing the immobilization of heavy metals such as cadmium (Cd), copper (Cu), and zinc (Zn). For instance, the combination of vivianite and S2− boosted the removal of Cd2+ from the aqueous phase under anaerobic conditions, and ensured the retention of Cd stabilized in the solid phase when shifted to aerobic conditions. It is intriguing to note that no discrete FeS formation was detected in the sulfidation phase, and the primary crystal structure of vivianite largely retained its integrity throughout the whole process. Detailed molecular-level investigations indicate that sulfidation predominantly targets the Fe(II) sites at the corners of the PO4 tetrahedron in vivianite. With the transition to aerobic conditions, the exothermic oxidation of CdS and the S sites in vivianite initiates, rendering it thermodynamically favorable for Cd to form multidentate coordination structures, predominantly through the Cd-O-P and Cd-O-Fe bonds. This mechanism elucidates how Cd is incorporated into the vivianite structure, highlighting a novel pathway for heavy metal immobilization via the sulfidation−reoxidation dynamics in iron phosphate minerals.

Investigation of microstructure evolution and redox behavior of Ni-GDC cermet by cyclic re-oxidation in CO2

The microstructure and reactivity of Ni-GDC cermet under cyclic oxidation in CO2 conditions were investigated using temperature-programmed reduction (TPR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The XRD results revealed that NiO was formed during the re-oxidation process in CO2. SEM and TPR results demonstrated that nanostructured NiO aggregates were formed on the surface of the sample after being re-oxidized at 400 °C for 1200 min, resulting in an α peak with high reduction activity and a conversion of only 16% from Ni to NiO. In contrast, the samples re-oxidized at 600 °C for 600 min and 800 °C for 240 min were completely oxidized, resulting in reconstructed and sintered NiO with larger particle size, and a β peak with lower reactivity and a conversion of 100%. Redox cycling was further conducted on completely oxidized samples, which showed a decrease in β peak temperature from the first to seventh cycle. The migration and redistribution of sintered NiO towards the exterior were confirmed by comparing SEM images after the first and fourth cycles, which favored an increase in the reactive area. Therefore, this study reveals that lower re-oxidation temperatures (≤400 °C) and an appropriate increase in redox cycles are beneficial for forming surficial nanostructures while hindering the formation of large sintered NiO particles.

Reoxidation dynamics of the methylene blue reduced by laser-synthesized silver nanoparticle

The catalytic reduction of methylene blue (MB) by metal nanoparticles and subsequent reoxidation is widely recognized and often referred to as a "redox reaction." The reduction mechanism of MB has been extensively studied and is well understood but its reoxidation has received little attention. Here we report an experimental study on the reoxidation dynamics of MB reduced by silver nanoparticles (Ag NPs). Ag NPs synthesized using the Pulsed Laser Ablation (PLAL) technique are used to reduce MB in the presence of the reducing agent NaBH4. The reduction/reoxidation dynamics are monitored using UV−Vis spectroscopy through the decrease/increase of characteristic MB absorbance peak and color switching between methylene blue and leucomethylene (LMB). The influence of the various volumetric concentrations of Ag NPs and NaBH4 on reoxidization dynamics of reduced MB is investigated. The reoxidation of reduced MB exhibited almost linear growth over time for different concentrations of both Ag NPs and NABH4 used in the reduction process. Higher NaBH4 concentrations appeared to decelerate the reoxidation process, while the concentration of Ag NPs had no discernible impact on the reoxidation rate. The reduction of reoxidized MB after adding additional amounts of Ag NPs and NaBH4 revealed that Ag NPs remained stable in the reaction medium but NaBH4 deteriorated. Therefore, the deterioration of the NaBH4 is identified as the major cause of the reoxidation of the reduced MB. A series of reduction-reoxidation experiments using chemically synthesized Ag NPs indicated that MB reoxidation is not limited to laser-synthesized Ag NPs.

Multi-Stimuli Operando Transmission Electron Microscopy for Two-Terminal Oxide-Based Devices.

The integration of microelectromechanical systems (MEMS)-based chips for in situ transmission electron microscopy (TEM) has emerged as a highly promising technique in the study of nanoelectronic devices within their operational parameters. This innovative approach facilitates the comprehensive exploration of electrical properties resulting from the simultaneous exposure of these devices to a diverse range of stimuli. However, the control of each individual stimulus within the confined environment of an electron microscope is challenging. In this study, we present novel findings on the effect of a multi-stimuli application on the electrical performance of TEM lamella devices. To approximate the leakage current measurements of macroscale electronic devices in TEM lamellae, we have developed a postfocused ion beam (FIB) healing technique. This technique combines dedicated MEMS-based chips and in situ TEM gas cells, enabling biasing experiments under environmental conditions. Notably, our observations reveal a reoxidation process that leads to a decrease in leakage current for SrTiO3-based memristors and BaSrTiO3-based tunable capacitor devices following ion and electron bombardment in oxygen-rich environments. These findings represent a significant step toward the realization of multi-stimuli TEM experiments on metal-insulator-metal devices, offering the potential for further exploration and a deeper understanding of their intricate behavior.

Corrosion behavior of metallic coatings on titanium bipolar plates of proton exchange membrane water electrolysis

The corrosion resistance, conductivity, and cost of the metallic bipolar plates are the main limitations for the Proton Exchange Membrane Water Electrolysis (PEMWE) commercialization. In the present study, Ta, Nb, and Ti non-precious metallic coatings were deposited by closed-field unbalanced magnetron sputtering to increase the corrosion resistance and conductivity of titanium bipolar plates in PEMWE, respectively. The coating samples suffer from corrosion in a simulated extreme anode operating environment of PEMWE (0.5 M H2SO4 + 5 ppm HF, 80 °C, O2). The surface of the Ti coating forms the micropores due to the high dissolution rate in initial formation stage of the passivation film, resulting in a higher current density (1.41 × 10−6 A cm−2). The hydrolysis reaction of Ta coating causes the adsorption of sulfide ions, thereby affecting the density of the passivation film. Despite the Ta coating exhibiting a favorable current density (4.82 × 10−7 A cm−2), ICR (463.11 mΩ cm2) is lamentably poor. The surface of Nb coating has been completely covered by Nb2O5 and NbO2 in the simulated PEMWE environment. The reoxidation process of NbO2 promotes the rate of passivation film formation and provides excellent conductivity. Therefore, Nb coating exhibits the lowest current density and interfacial contact resistance of 2.23 × 10−8 A cm−2 and 119.78 mΩ cm2, respectively, which is very low compared to the bare titanium bipolar plates.

Understanding the rapid reoxidation process and the electrical properties of Spark Plasma sintered pyrochlores

Pyrochlore structures with composition Pr2−xSmxZr2O7 (x = 0, 1, and 2) were synthetized and studied. Spark Plasma Sintering (SPS) was employed to produce ceramics with over 95% of relative density. The reoxidation behavior and the influence of the sintering process on the electrical properties were studied by Electrochemical Impedance Spectroscopy. The overall conductivity of the materials is higher for the samples with Pr, while the introduction of Sm induced an additional electrical contribution. The reoxidation of the samples presented fast kinetics and increased conductivity, particularly in the PrSmZr2O7 (PSZO) sample. PSZO also exhibits a total conductivity comparable to that of the reference materials used as ionically conductive solid electrolytes. The prepared ceramics, especially the PSZO sample, demonstrate excellent relative density, good conductivity, and fast oxidation, holding promise for applications such as Solid Oxide Fuel Cells, gas sensors, and clean energy technologies that require thermal and physical stability, as well as rapid oxidation-reduction processes.

Nonmicrobial mechanisms dominate the release of CO2 and the decomposition of organic matter during the short-term redox process in paddy soil slurry

Both biotic and abiotic mechanisms play a role in soil CO2 emission processes. However, abiotically mediated CO2 emission and the role of reactive oxygen species are still poorly understood in paddy soil. This study revealed that OH promoted CO2 emission in paddy soil slurries during short-term oxidation (4 h). OH generation was highly hinged on active Fe(II) content, and the OH contribution to CO2 efflux was 10%–33% in topsoil and 40%–77% in deep-soil slurries. Net CO2 efflux was higher in topsoil slurries, which contained more dissolved organic carbon (DOC). CO2 efflux correlated well with DOC contents, suggesting the critical role of DOC. Microbial mechanisms contributed 9%–45% to CO2 production, as estimated by γ-ray sterilization experiments in the short-term reoxidation process. Solid-aqueous separation experiments showed a significant reduction in net CO2 efflux across all soil slurries after the removal of the original aqueous phase, indicating that the water phase was the main source of CO2 emission (>50%). Besides, C emission was greatly affected by pH fluctuation in acidic soil but not in neutral/alkaline soils. Fourier transform ion cyclotron resonance mass spectrometry and excitation-emission matrix results indicated that recalcitrant and macromolecular dissolved organic matter (DOM) components were more easily removed or attacked by OH. The decrease in DOM content during the short-term reoxidation was the combined result of OH oxidation, co-precipitation, and soil organic matter release. This study emphasizes the significance of the generally overlooked nonmicrobial mechanisms in promoting CO2 emission in the global C cycle, and the critical influence of the aqueous phase on C loss in paddy environments.

Enhanced reliability of ultra-thin multilayer ceramic capacitors (MLCCs) based on re-oxidation process

Enhanced reliability of ultra-thin multilayer ceramic capacitors (MLCCs) based on re-oxidation process

The Electrodegradation Process in PZT Ceramics under Exposure to Cosmic Environmental Conditions.

Long-time electric field action on perovskite piezoelectric ceramic leads to chemical degradation. A new way to accelerate the degradation is the exposure of the ceramic to DC electric fields under a vacuum. A high-quality commercial piezoelectric material based on PbZr1-xTixO3 is used to study such impacts. To avoid the influence of ferroelectric properties and possible removal of oxygen and lead oxides during the degradation process, the experiments are in the temperature interval of 500 °C > T > TC. Changes in resistance during the electrodegradation process is an electrically-induced deoxidation, transforming the ceramic into a metallic-like material. This occurs with an extremely low concentration of effused oxygen of 1016 oxygen atoms per 1 cm3. Due to this concentration not obeying the Mott criterion for an isolator-metal transition, it is stated that the removal of oxygen mostly occurs along the grain boundaries. It agrees with the first-principle calculations regarding dislocations with oxygen vacancies. The decrease in resistivity during electrodegradation follows a power law and is associated with a decrease in the dislocation dimension. The observed reoxidation process is a lifeline for the reconstructing (self-healing) properties of electro-degraded ceramics in harsh cosmic conditions. Based on all of these investigations, a macroscopic and nanoscopic model of the electrodegradation is presented.

Crucial role of H and O spillover in VOx/CeO2 catalysts reduction and re-oxidation during the ODH reaction

Ceria-supported monomeric vanadia (VOx/CeO2) catalysts show outstanding activity in oxidative dehydrogenation (ODH) in the CO2 atmosphere. This work reports the density functional theory calculations exploring the reduction and reoxidation mechanisms in the Mars-van-Krevelen cycle for the ODH over VOx/CeO2(111). Intriguingly, a new phenomenon was observed in the reduction of VO2/CeO2(111), the H species generated by CH bond activation on the VOx cluster could spill over to CeO2 with a minimum barrier, enabling the reduction to occur at CeO2 substrate. Subsequently, the formed H2O releases and causes a structure evolution, resulting in VO2/CeO2(111) reduction to VO/CeO2(111). However, this H spillover is hard to be detected at the interface of VO/CeO2(111), VOx/TiO2(101), and VOx/α-Al2O3(001) due to a higher barrier, indicating that the H spillover is related to the electron acceptability of substrate and the structure of VOx cluster. Moreover, O spillover from CeO2 is noticed at the interface of VOx/CeO2(111) in the reoxidation process, causing the V oxidation to VO. However, VO reoxidation to VO2 is thermodynamically and dynamically unfavorable. Therefore, the structure VO/CeO2(111) seems to be conserved in the steady-state reaction process. This paper would provide key insights for understanding the structure evolution of catalyst in the ODH.

Electron transfer routes in nitrate-pentavalent vanadium co-contaminated system of oligotrophic microbiology niche

Microbial techniques have been extensively used for the remediation of nitrate and V(V) co-contaminations, but the mechanisms of electron and substances transport and metabolism of co-contaminations under oligotrophic niche have been largely overlooked. This study quantified the electron transfer and consumption, substance transfer, and metabolic pathways in the nitrate and V(V) co-contamination system under oligotrophic condition to explore the underlying mechanisms by characterizing the products and elucidating conventional cognitive pathways. This study compared the composition of the precipitates under the conditions of sufficient and insufficient carbon sources using energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and discovered the re-oxidation process of the already reduced V(IV). Electronic evidence for the re-oxidation process of V(IV) was also provided by electron transfer and quantitative analysis. Besides, this study found that the electron contribution ratio of NO3−-N → NO2−-N and V(V) → V(IV) reduction was 40.2:1. In addition, based on the functional prediction of PICRUSt 2, it was found that the utilization of intracellular reserve carbon source and enzymes in the transport chain were enhanced in oligotrophic microbiology niche. These results provide new insights into the stability of co-contamination reduction in oligotrophic microbiology niche and demonstrate a new mobilization pathway for V(V) in oligotrophic systems.

Highly Efficient and Stable Bifunctional Electrocatalyst with Alloy/Oxide Heterostructures for a Rechargeable Zinc–Air Battery

Constructing heterogeneous interfaces between transition metal alloys and oxides in a carbon-based composite catalyst is an effective strategy for boosting the oxygen evolution reaction and oxygen reduction reaction (OER and ORR). Inspired by this concept, a carbon-coated MnCoNi alloy/oxide catalyst (Ox-MnCoNi-C) was synthesized by carbonization of metal–organic frameworks (MOFs) and controllable reoxidation process. Owing to the synergetic interaction between abundant active sites on the heterogeneous interface and the good electron transfer rate of graphitic carbon, Ox-MnCoNi-C exhibits a low potential gap (ΔE) of 0.79 V. Meanwhile, the assembled liquid zinc–air batteries exhibit high power density (125 mW cm–2), superior primary discharge specific capacity (822 mAh gZn–1), and no less than 100 h of steady charging and discharging operation running at 5 mA cm–2. This approach will provide a generic template for the preparation and extension of MOF-derived carbon composite catalysts applied in oxygen electrocatalysis.

Release and mobilization of Ni, Co, and Cr under dynamic redox changes in a geogenic contaminated soil: Assessing the potential risk in serpentine paddy environments

The release dynamics and mobilization of geogenic Ni, Co, and Cr in serpentine paddy soils under fluctuating redox conditions have not yet been well studied. Here we investigated the release dynamics of Cr, Co, and Ni and controlling factors (e.g., Fe, Mn, Mg, Cl−, PO43−, SO42−, and dissolved organic carbon (DOC)) in a geogenic-contaminated serpentine soil under wide range of redox potential (EH) changes. The effects of re-oxidation process have been also investigated. The soil was incubated for 28 days and EH was controlled from oxidation (+200 mV) to reduction (−200 mV) and re-oxidation (+240 mV) using a microcosm setup in duplicates. The slurry pH increased, along with decreasing EH. The average concentration of dissolved Co (17.1–23.6 μg L−1) decreased under low EH/high pH and vice versa. The average concentration of dissolved Cr decreased sharply from 624 μg L−1 to 54.4 μg L−1 with decreasing EH from +200 mV to 0 mV and the associated increase of pH from 7.8 to 8.5; then, it was constant around 24.5 μg L−1. Concentration of dissolved Ni was lower (73.5–84.6 μg L−1) under high EH at the first week of incubation; then, increased to 108.5 μg L−1 under low EH (−200 mV); thereafter, increased more at the end up to 124.5 μg L−1 at high EH (+240 mV), because of the pH decrease. A factor analysis identified that Cr and Co formed one group with Mn and Mg, while Ni was clustered together with Cl−, DOC, and SO42−. This indicates that the redox-induced release dynamic of Cr and Co was mainly governed by MnMg compounds, while the release of Ni was mainly affected by the aliphatic compounds of DOC and the redox chemistry of chlorides and sulfur in this soil. The re-oxidation increased the mobilization of Ni and Co and did not affect the release of Cr. These findings suggest that the redox-induced mobilization of geogenic Co, Ni, and Cr from soil to water in serpentine rice soils should be considered due to the high solubility and thus the associated bioavailability and potential environmental and human health risks, when such metal-enriched soils will be used for agricultural flood-dry cycle systems.

SO2-tolerant NOx reduction over SO42--coordinated Cu-SAPO-34 catalysts via protecting the reduction and re-oxidation of Cu sites

Selective catalytic reduction of NOx from mobile source over Cu-SAPO-34 catalysts always suffer from sulfur poisoning in practical applications. The pore blockage and loss of active Cu species after sulfur poisoning seriously damage the NOx reduction ability of Cu-SAPO-34 catalysts. In this work, we used SO42--coordinated Cu-SAPO-34 catalysts to improve the sulfur resistance, which can still maintain over 90% NO conversion after 24 h of reaction in an SCR feed with high concentration of SO2. A series of characterization revealed that the process of CuII species being reduced to CuI and the reoxidation of CuI species to CuII is usually inhibited after SO2 poisoning in Cu-SAPO-34 catalysts, which in turn leads to the accumulation of ammonium bisulfate species (ABS) and the sulfation of Cu sites. The directed coordination of SO42- on Cu sites in Cu-SAPO-34 catalyst decreases the adsorption of SO2, hence the deposition of ABS is reduced and the sulfation of Cu sites is inhibited as well. This SO42--coordinated Cu-SAPO-34 catalyst can still carry out a complete SCR reaction cycle under the poison of SO2, which is resulted from the well-maintained reduction and re-oxidation process of Cu active sites. This work paves a way for the development of highly efficient anti-poisoning SCR catalysts in practical applications.

Self-optimized and renewable Ni–Co alloy@Co–Co2C catalyst for higher alcohols synthesis from syngas

Higher alcohols synthesis (HAS) from syngas (CO/H2) has attracted widespread attention, while the low selectivity and poor stability of the catalysts mainly stumbled its industrial application. In the work, Ni–Co alloy nanoparticles (NPs) derived from Co1-xNixAl2O4 loaded on the SiO2 with large specific surface area were prepared; and during reaction, the highly dispersed Ni–Co alloys were self-optimized to Ni–Co alloy@Co–Co2C. Importantly, Ni–Co alloy@Co–Co2C can be regenerated through oxidation - reduction - self-optimization process. Characteristic results indicated that the structural liberalization during the reaction process inhibited the loss of Ni, regulated and balanced the dual active sites of the catalyst and the Ni–Co alloys were regenerated after the re-oxidation and re-reduction process. The optimized catalyst exhibited excellent catalytic performance, including a high total selectivity to alcohols of 39.3% and an excellent catalytic stability at 250 °C, 3.5 MPa (H2/CO = 2) and a space velocity of 6000 mL (gcat h)−1. In addition, the Ni–Co alloy@Co–Co2C catalyst after stability test could recover its original catalytic performance after re-oxidation and re-reduction. The renewable characteristics and superior catalytic performance of Ni–Co alloy@Co–Co2C made the catalyst to be one of the potential industrial catalysts for HAS.

In-situ surface reconstruction induced-significant performance promotion of Ca3Co4O9+δ cathode for solid oxide fuel cells

Surface morphology of cathode has a significant impact on the oxygen reduction reaction (ORR) activity as well as the performance of solid oxide fuel cells (SOFCs). Up to now, great efforts have been devoted to decorate the microstructure of SOFC cathode, such as changing synthesis method, infiltration, electrospinning and so on. Herein, we report an effective and feasible method to reconstruct the surface of Ca3Co4O9+δ (CCO) cathode by reduction and re-oxidation process, during which remarkable morphology change is observed as the surface is wrinkled with the formation of numerous small particles. ORR activity of CCO cathode is notably improved after surface reconstruction, since area specific resistance (ASR) of CCO cathode significantly decreases from 0.48 Ωcm2 to 0.19 Ωcm2 at 700 °C. Specific surface area of CCO increased and calcium and cobalt oxide nanoparticles are generated after the redox treatment. The oxygen adsorption ability of the CCO is largely enhanced, which contributes to the performance promotion of CCO cathode after the redox treatment. Overall, we propose a feasible method to reconstruct CCO surface to promote the ORR activity effectively and study the corresponding mechanism thoroughly, all of which make valuable improvements on the development of SOFC cathode.

Evolution of Inclusions and Cleanliness in Ti-Bearing IF Steel Produced via the BOF–LF–RH–CC Process

Owing to the insufficient converter heat, IF steel is produced via the BOF–LF–RH–CC process in Pangang Group Xichang Steel and Vanadium Co., Ltd. To clarify the evolution of inclusions and the control strategy to improve the cleanliness of molten steel in Ti-bearing IF steel produced via the long process, scanning electron microscopy with energy spectroscopy analysis and automatic scanning electron microscopy were employed to analyze the number, size, type and morphology of inclusions in IF steel from RH to tundish. The results show that the characteristics of inclusions are similar in two heats during RH treatment. In the tundish sample of Heat 2, the number density (ND) and area fraction (AF) of Al2O3 and Al2O3·TiOx inclusions increase significantly, and the size of Al2O3 inclusions decreases obviously, which is closely related to the serious reoxidation of molten steel caused by the slag with high oxidability during the holding process. Meanwhile, a new method of determining the number of cluster inclusions is used to evaluate the cleanliness of IF steel in this paper, and the obtained number of inclusion clusters is consistent with the trend of ND and AF of inclusions. The effects of reoxidation on the morphology, number and other indexes of Al2O3 and Al2O3·TiOx inclusions are discussed in detail, and there are two ways of forming Al2O3·TiOx inclusions in the case of serious reoxidation. To weaken the reoxidation process and enhance the cleanliness of IF steel produced via the long process, reducing the oxygen content in molten steel before Al deoxidation, minimizing the holding time and reducing the oxidability of slag after RH are helpful.