Increasing Oxidation Temperature Research Articles

Preparation of Copper Oxide/TiO2 Composite Films by Mechanical Ball Milling and Investigated Photocatalytic Activity

The Cu/Ti composite coatings were prepared by the mechanical ball milling, the CuO/TiO2 and Cu2O/TiO2 composite photocatalytic films were obtained by the subsequent oxidation process. The microstructure of the composite films was analyzed by X-ray Diffraction (XRD）and scanning election microscope (SEM). The photocatalytic activity was evaluated, the effects of ball milling time on the formation of the Cu/Ti coatings were investigated, and the effects of the oxidation temperature and oxidation atmosphere on microstructure and photocatalytic activity of the films were studied. The results illustrate that the ball milling time has significant effects on the formation of the coatings and the coatings are continuous and compact by ball milling for 15 h. The photocatalytic activity of the CuO/TiO2 composite films is increased first and then decreased with the oxidation temperature increases, and the photocatalytic activity is the best at 500 °C. The CuO/TiO2 composite films are obtained by the oxidation of Cu/Ti coatings at 500 °C for 15 h in the air, while the Cu2O/TiO2 composite films are oxidized in carbon atmosphere. Photocatalysis efficiency of the films is obviously enhanced with the help of the p-n junction heterostructure in the Cu2O/TiO2 composite films.

Surface properties of oxidized lignite and its application in congo red dye adsorption

ABSTRACT Lignite is easily oxidized, and spontaneous combustion occurs during its storage, which greatly reduces its calorific value and affects its quality and economic benefits. The surface properties of the oxidized lignite including pore structure and oxygen-containing functional groups were investigated by N2 adsorption/desorption isotherms and Fourier transform infrared spectroscopy. The adsorption of Congo red dye in aqueous solution by oxidized lignite was carried out. It was observed that due to oxidation, the specific surface area and total pore volume of the Huolinhe lignite samples decreased, and the average pore size increased. As oxidation temperature increased, the number of microporous and mesoporous structures decreased, resulting in the decrease of fractal dimension. The hydroxyl content was negatively correlated with the oxidation temperature, but the carbonyl content showed an opposite trend. At the initial stage of oxidation, the rate of hydroxyl consumption is higher than that of formation. The reaction to generate carbonyl, such as the oxidation of aliphatic hydrocarbons, alcohol hydroxyl groups and ethers, requires a higher reaction temperature, so the carbonyl content increased when the temperature was higher than 70 °C. Oxidized lignite was used to adsorb Congo red dye in aqueous solution, and the removal increased significantly with increasing oxidation temperature. Therefore, oxidized lignite can effectively remove Congo red dye from aqueous solution, so as to improve the economic benefit of oxidized lignite.

Oxidation Mechanism of Al-Sn Bearing Alloys.

Oxidation of Al-Sn bearing alloy occurs during production, processing and use, which reduces both alloy performance and performance of coatings applied to the alloy surface. Therefore, the oxidation mechanism of Al-Sn bearing alloy is studied at 25, 180, 300, and 500 °C. The oxidation morphologies of the alloy were observed by scanning electron microscopy (SEM), and the oxidation products were determined by X-ray diffraction (XRD). The oxidation weight gain curves were obtained by thermogravimetric analysis. The experimental results show that: Al-Sn bearing alloy is oxidized quickly to form Al2O3. As the oxidation temperature increases, Sn phase start to precipitate along the grain boundary and form networked spheroids of Sn on the alloy surface. The amount of precipitation increases with further increase of the oxidation temperature. Cracks and holes are left in the alloy. The oxide layer is mainly composed of Sn, SnO2, and Al2O3. At 25 °C, oxidation rate of Al-Sn alloy approach zero. At 180, 300, and 500 °C, the oxidation rate increases quickly conforming to a power function, and eventually remains stable at about 3 × 10−6 mg·mm−2·s−1.

Effect of oxidation temperature on the properties of NiOx layers for application in optical sensors

Thin NiOx layers were prepared by oxidation at 400, 500 and 600 °C of metallic Ni deposited by electron beam evaporation. The bandgap of NiOx determined from optical measurements increases from 3.6 to 3.7 eV with the increase of oxidation temperature from 400 to 500°C. Higher temperature leads to larger grain sizes, 12.6 nm at 400 °C, 15.3 nm at 500 °C and 16.1 nm 600 °C. Photodiodes based on NiOx/Si heterostructure were fabricated by evaporation of semitransparent Au top contacts. The structures with NiOx obtained at 500 °C showed superior diode characteristics compared to the other two types of devices with dark current < 3.5 × 10-8 A (current density J < 3.9 × 10−4 A/cm2) for reverse biases between 0 and -2 V and forward current of 3.3 × 10−5 A (J = 0.36 A/cm2) at bias of 1.5 V. The responsivity of these devices at 0 V is between 0.85 and 0.55 A/W for wavelengths in the 365 – 635 nm range, values higher than those previously reported for self-powered NiOx/Si photodiodes. The responsivity at reverse bias of -1.5 V increases more than 60 times to values of 33, 32, 50 and 59 A/W for red, green, blue, and ultraviolet light, values among the highest reported for broadband photodetectors. The excellent properties of the photodiodes with NiOx obtained at 500 °C are the result of a higher quality of the Si/NiOx interfacial region, which leads to lower recombination rate of the photogenerated carriers.

The variations of free radical and index gas CO in spontaneous combustion of coal gangue under different oxygen concentrations

SummaryIn order to study the effect of oxygen concentrations on the change of active groups in the oxidation process of coal gangue, the airflows of different oxygen concentrations were prepared to simulate the oxidation and heating process of coal gangue under oxygen concentrations of 0%, 5%, 10%, 15%, and 21%. During the oxidation and heating process, the free radical parameters were measured at different temperatures in real time. The results show that in the early stage of coal gangue oxidation, the g factor remains at a lower level and do not start to increase until certain temperatures are reached. Besides, the higher the oxygen concentration is, the lower the temperature at which the g factor begins to increase. When the oxygen concentrations are 0%, 5%, 10%, 15%, and 21%, the corresponding temperatures are 225, 200, 150, 150, and 125°C, respectively. Furthermore, with the increase of oxidation temperature, the free radical concentrations experience four stages, namely, the slow increase stage, the rapid increase stage, the stagnant increase stage, and the final increase stage. And the higher the oxygen concentration is, the shorter the free radical stagnant increase stage is. During the oxidation of coal gangue, the line widths decrease slowly before 150°C, and then start to plunge and finally stabilize near the minimum at 350°C. Moreover, the higher the oxygen concentration is, the smaller the minimum values of line widths are. In the oxidation process of coal gangue, the gas product CO amounts are first at a lower level, and then begin to increase rapidly after 150°C. At the same temperature, the increased rates of CO production in coal gangue under the oxygen concentrations of 10%, 15%, and 21% are significantly higher than those under the oxygen concentrations of 0% and 5%. Based on the variation law of free radical parameters in coal gangue under different oxygen concentrations, the actual spontaneous combustion of gangue hills was analyzed and the free radical reaction mechanism of spontaneous combustion of gangue hills was discussed. The research results are of guiding significance for the treatment of spontaneous combustion of coal gangue.

Compositional evolution of lignite during spontaneous combustion under low-temperature oxidation

In order to better explore the spontaneous combustion characteristics of lignite, a low-temperature heating experimental device was used to study the changes in the physical and chemical structure of lignite in an air atmosphere of 50–350°C. Through FTIR, XRD and SEM, the coal sample's chemical structure and surface microstructure change at low temperature are correlated and analysed, and the physical and chemical fabric change law of the coal sample at low temperature is obtained. The results show that in the water loss stage, the hydroxyl content in the coal sample increases, and the surface pores of the coal sample become larger. As the oxidation temperature increases, the pores further expand, secondary cracks appear, and gas escapes. In the decarboxylation stage, the coal sample is further coked, the methyl group increases, the oxygen-containing functional group increases, and the coal sample crystallisation degree increases, which accelerates the spontaneous combustion of the coal sample. The result of our study offers useful guide for early coal spontaneous combustion prediction on site.

The reaction of free radicals and functional groups during coal oxidation at low temperature under different oxygen concentrations

Safety and environmental problems caused by coal mining and utilization are becoming increasingly severe. The air leakage and uneven oxygen distribution in goaf seriously affect coal’s natural oxidation. Therefore, an in-depth understanding of the changes of free radicals and functional groups in coal under different oxygen concentrations during low-temperature oxidation is essential for dynamically preventing and controlling the spontaneous combustion of residual coal in goaf, which is of great significance for mine safety and environmental protection. Based on Electron spin resonance (ESR) and Fourier transform infrared (FTIR) spectroscopy, an analysis was made on the influence of different oxygen concentrations on the reaction activity of micro-groups during low-temperature coal oxidation. The results show that with increasing oxidation temperature in a range of 30℃–230℃, the concentration of free radicals Ng improves. When the oxygen concentration exceeds 9 %, the production of free radicals Ng significantly accelerates. The content of −CH2 and −CH3 and −OH, major reaction groups in coal oxidation, declined to various degrees with the gradual increase of temperature. The reaction rate of CO and −COOH was positive in the whole heating range (30℃–230℃), indicating that CO and −COOH are the products. During the entire oxidation heating process, when the oxygen concentration reaches 3% and 21 %, the CO content increases by 38.65 % and 59.71 %, respectively, and the −COOH content increases by 32.74 % and 51.96 %. At low oxygen concentrations (O2≤9 %), the range of each active group’s change is relatively small, which implies that low-oxygen conditions can inhabit the coal-oxygen reaction. At high oxygen concentrations (O2 > 9 %), active groups are more likely to react. The rise of temperature ushers in a rapid oxidation stage of coal. Besides, it is necessary to strengthen the fire extinguishing and cooling efforts in goaf deep low-oxygen area.

Effect of oxidation temperature and oxygen concentration on macro characteristics of pre-oxidised coal spontaneous combustion process

Coal fire disasters occur frequently in exposed or underground coal zones or gobs, which usually triggered by pre-oxidised coal spontaneous combustion (PCSC). The thermal mass loss characteristics and thermal effects of pre-oxidised coal with the oxidation temperature and oxygen concentration were investigated. The thermogravimetry (TG) results revealed that the oxidation reaction occurred earlier for the pre-oxidised coal than for raw coal. The pre-oxidised coal had a poor ignition performance and burnout capacity than that of raw coal. In addition, the comprehensive combustion performance of pre-oxidised coal is weaker than that of raw coal, but its combustion rate and short-term combustion intensity are higher than raw coal. The differential scanning calorimetry (DSC) results indicated that the temperature at which the thermal release of pre-oxidised coal increases rapidly lags behind that of raw coal. Moreover, the maximum thermal release power and thermal release for the pre-oxidised coal were less than those for raw coal. The risk of PCSC changes with the increase of oxidation temperature, and there is a critical value of oxidation temperature. When the oxidation temperature was less than the critical value the risk of PCSC is higher than that of raw coal. Furthermore, the critical value decreases with the increase of oxygen concentration.

Fabrication of in-situ self-reinforced Si3N4 ceramic foams for high-temperature thermal insulation by protein foaming method

To meet demand for lightweight and high-strength ceramic foams, in-situ self-reinforced Si3N4 ceramic foams, with compressive strength of 13.2–45.9 MPa, were fabricated by protein foaming method combined with sintered reaction-bonded method. For comparison, ordinary protein foamed ceramics with irregular block microstructure were fabricated via reaction-bonded method, which had compressive strength of 3.6–20.5 MPa. Physical properties of these two types of samples were systematically compared. When open porosity was about 80%, both types of Si3N4 ceramic foams had excellent thermal insulation properties (<0.15 W m−1 K−1), while compressive strength of in-situ self-reinforced samples increased by more than 158% compared with ordinary samples. Under high-temperature oxidation conditions, microstructures of both types of samples were deformed with increase in oxidation temperature. Moreover, after oxidation temperature was increased to 1400 °C, oxidation weight gain decreased from 18.07% for ordinary samples to only 2.18% for self-reinforced samples. Thus, high-temperature oxidation resistance of Si3N4 ceramic foams was greatly improved.

Structure and properties of graphene oxide during the synthesis process at fixed temperatures

Graphene oxide (GO) is the most versatile derivative of graphene; however, the choice of oxidation temperature in the synthesis of GO varies from person to person. In this article, various spectroscopy techniques have been used to characterize carbon and oxygen structure of GO synthesized at fixed oxidation temperatures. Our results show that GO synthesized at a relatively low temperature possesses a decreased D-to-G peak intensity ratio (ID:IG) and obvious single-crystal lattice with a six-fold pattern. As the oxidation temperature increase, a polycrystalline ring structure forms, accompanied by an increasing ID:IG, which indicates that the disorder of the basal plane of GO increases with increasing temperature. Notably, the layer spacing of GO decreases with an increase in temperature, which does not show the expected proportional relationship to the degree of oxidation. Furthermore, chemical composition analysis shows that moderate temperatures contribute to the formation of C–O–C and ≥CO bonds, while the contents of C–OH and sp2 domains decreases, and the content of COOH does not change with temperature. Interestingly, GO is successfully synthesized at 75 °C, indicating that Mn2O7 is not the only oxidant playing a dominant role in the oxidation stage of GO. This work can provide in-depth insight into the viable selection of the oxidation temperature of GO for industrial applications.

Experimental investigation into the number, micromorphology, functional group composition, and oxidation activity of particles from diesel engine with biodiesel blend

Biodiesel is a promising alternative clean fuel for vehicles. In this paper, comprehensive particulate characteristics, including the particle number (PN), particle mass (PM), particle size distribution, particle micromorphology, chemical functional groups and particle oxidation activity from biodiesel blend B20 (20% biodiesel and 80% diesel by volume), were investigated based on a diesel bus using a heavy chassis dynamometer bench. Results showed that B20 could reduce the PN by 18.8% and the PM by 27.3%. The reduction efficiency of B20 on the accumulation mode particles was higher than that of the nucleation mode ones, which were 43.2 and 7.6%, respectively, thereby causing the proportion of the nucleation mode particles in B20 to increase from 54 to 66% in comparison with that of D100 (pure diesel). In terms of the particle micromorphology, the average fractal dimension of the particles from B20 was higher than that of D100, indicating that the particles from B20 were more compact. The proportion of typical core–shell structure particles in the basic carbon particles of B20 was higher than that of D100, and the coincidence degree between particles was also higher for B20; additionally, B20 preferred to produce basic carbon particles with a regular spherical shape. The graphitization degree of the particles increased with increasing oxidation temperature, but the lattice defect degree decreased. The Raman analysis reflected that the particles of B20 had a higher lattice defect degree but a lower graphitization degree compared with the particles of D100. The ratio of O/C, as well as the sp3/sp2 ratio of the B20 particles, were higher than those of the D100 particles, also indicating that more defects were present in the B20 particles. The particles from B20 exhibited higher oxidation activity in comparison with the particles from D100.

The Optical and Electrical Performance of CuO Synthesized by Anodic Oxidation Based on Copper Foam.

Metal oxide semiconductor materials have a wide range of applications in the field of solar energy conversion. In this paper, CuO was prepared directly on copper foam substrate by anodic oxidation. The effects of current density and anodizing temperature on sample preparation and performance were studied. Field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD) had been used to determine the morphology and phase structure of the sample, and its optical and electrical properties were discussed through UV-vis spectrophotometer and electrochemical tests. In addition, the influences of experimental conditions such as current density and reaction temperature on the morphology and properties of CuO were systematically discussed. The FESEM images showed that as the anodic oxidation temperature increase, the morphology of the prepared sample changed from nanowires to leaf-like CuO nanosheets. According to the results of XRD, the structure of prepared CuO was monoclinic, and the intensity of diffraction peaks gradually increased as anodizing temperature increased. We found that the optimum current density and anodizing temperature were 20 mA cm−2 and 60 °C, respectively. The results of electrochemical indicated that the CuO electrode based on copper foam (CuO/Cu foam) prepared at the optimum exhibited the highest specific capacitance (0.1039 F cm−2) when the scan rate was 2 mV s−1.

Simultaneous removal of NOx and SO2 using two-stage O3 oxidation combined with Ca(OH)2 absorption

This paper proposes two-stage O3 oxidation combined with Ca(OH)2 for simultaneous removal of NOx and SO2 (NOx: Nitrogen oxides including NO, NO2 and N2O5). In two-stage oxidation, NO was first oxidized to NO2 in an oxidation tube, and NO2 was further oxidized into N2O5 in the spray tower. NOx and SO2 were simultaneously removed in the spray tower. This method can effectively reduce the extra waste of O3 caused by the decomposition of N2O5, especially at high temperature. Effects of various factors on denitrification efficiency were investigated. The results showed that the NOx removal efficiency decreased and O3 extra consumption ratio increased with the increase of oxidation temperature or oxidation reaction time. When the O3/NO molar ratio was 1.8, one-stage O3 oxidation at 150 oC extra wasted 33.3% of O3. With the increase of O3 concentration at site 2, the NOx removal efficiency first increased and then stabilized. Compared with the one-stage O3 oxidation-absorption, the two-stage oxidation-absorption improved NOx removal efficiency from 62.5% to 89%. In addition, the increase of CaSO3 slurry concentration had little effect on the denitrification efficiency.

High-Temperature Oxidation Resistance of CrMoN Films

The CrMoN film is deposited on the surface of M2 tool steel using the closed-field unbalanced magnetron sputtering technology. We measured the surface morphology, composition, phase structure, hardness and film/base bonding strength of CrMoN film using a scanning electron microscope, x-ray diffractometer, nano-indenter and scratch tester after oxidation at room temperature, 500, 600, and 700 °C for 1 h. The results of this study demonstrated that the crystal structure and mechanical property of CrMoN film at room temperature are maintained after oxidation at 500 °C for 1 h. In addition, with the increase in oxidation temperature, there is an increase in the evaporation of MoO3 on the film surface and the oxidation degree of the film along with the appearance of fine pores. Moreover, the mechanical property and film/base bonding strength of CrMoN film significantly decrease after oxidization at 700 °C for 1 h.

The role of multi-elements and interlayer on the oxidation behaviour of (Hf-Ta-Zr-Nb)C high entropy ceramics

Isothermal oxidation of (Hf-Ta-Zr-Nb)C high entropy carbide (HEC4) was performed using thermo-gravimetric analysis at 800−1100 °C in air. Polycrystalline oxide layers with multi-element oxides were observed, and their thickness increased with increasing oxidation temperature. Particular attention was paid to the microstructure and role of the interface. An amorphous and compact oxycarbide interlayer was observed between the oxide layer and the bulk carbide in oxidized HEC4, providing an effective diffusion barrier during oxidation. There was a through thickness distribution of the metals in the oxide layer, because of the different oxidation rates and outward diffusion of the cations.

The Effect of the Stabilization and Carbonization Temperatures on the Properties of Microporous Carbon Nanofiber Cathodes for Fuel Cells on Polybenzimidazole Membrane

Materials based on pyrolyzed electrospun nanofiber polyacrylonitrile were studied by the method of standard contact porosimetry. An influence of oxidation and pyrolysis temperatures on specific surface area. It was shown that an increase of oxidation temperature from 300 to 350°C and of pyrolysis temperature from 900 to 1000°C leads to a decrease of pore specific surface area and to a decrease of a part of micropore specific surface area. Platinated samples showed sufficient values of electrochemically active platinum surface area (12‒35 m2 g $$_{{{\text{Pt}}}}^{{ - 1}}$$ ) and were tested as cathodes for high temperature polymer electrolyte membrane fuel cell. An increase in power density was found when a part of electrode micropore specific surface area was decreasing.

Isothermal Splitting of CO2 to CO Using Cobalt-Ferrite Redox Looping

Abstract Rising atmospheric CO2 levels from significant imbalance between carbon emissions from fossil fuel utilization, especially for energy and chemicals, and natural carbon sequestration rates is known to drive-up the global temperatures and associated catastrophic climate changes, such as rising mean sea level, glacial melting, and extinction of ecosystems. Carbon capture and utilization techniques are necessary for transition from fossil fuel infrastructure to renewable energy resources to help delay the dangers of reaching to the point of positive feedback between carbon emissions and climate change which can drive terrestrial conditions to uninhabitable levels. CO2 captured from the atmosphere directly or from flue gases of a power plant can be recycled and transformed to CO and syngas for use as energy and value-added chemicals. Utilizing renewable energy resources to drive CO2 conversion to CO via thermochemical redox looping can provide a carbon negative renewable energy conversion pathway for sustainable energy production as well as value-added products. Substituted ferrites such as Co-ferrite, Mn-ferrite were found to be promising materials to aid the conversion of CO2 to CO at lower reduction temperatures. Furthermore, the conversion of these materials in the presence of Al2O3 provided hercynite cycling, which further lowered the reduction temperature. In this paper, Co-ferrite and Co-ferrite-alumina prepared via co-precipitation were investigated to understand their potential as oxygen carriers for CO2 conversion under isothermal redox looping. Isothermal reduction looping provided improved feasibility in redox conversion since it avoids the need for temperature swinging which improves thermal efficiency. These efforts alleviate the energy losses in heat recovery while also reducing thermal stresses on both the materials and the reactor. Lab-scale testing was carried out at 1673 K on these materials for extended periods and multiple cycles to gain insights into cyclic performance and the feasibility of sintering, which is a common issue in iron oxide-based oxygen carriers. Cobalt doping provided with lowering of reduction temperature requirement at the cost of oxidation thermodynamic spontaneity that required increased oxidation temperature. At the concentrations examined, these opposing phenomena made isothermal redox operation feasible by providing high CO yields comparable with oxygen carriers in the literature, which were operated at different temperatures for reduction and oxidation. Significantly high CO yields (∼750 µmol/g) were obtained from Co-ferrite isothermal redox looping. Co-ferrite-alumina provided lower CO yields compared with Co-ferrite. The oxygen storage was similar to those reported in the literature on isothermal H2O splitting, but with improved morphological stability at high temperature, especially compared with ferrite. This pathway of oxygen carrier development is considered suitable with further requirement in optimization for scaling of renewable CO2 conversion into valuable products.

Investigation of oxide scale formation and internal oxidation of an Fe-based coating at 500 °C and 600 °C

In this study, we investigated an Fe-based coating that was produced on a cylindrical surface via an internal rotating plasma spray and was oxidized at different temperatures. For microstructural characterization, scanning electron microscopy and electron probe microanalysis were combined with energy dispersive X-ray spectroscopy and X-ray diffraction analyses. The Fe-based coating exhibits a dense structure with small amounts of internal oxides and pores after internal rotating plasma spraying. During the oxidation process, an iron oxide scale formed on the surface of the Fe-based coating, and the thickness of the oxide scale increased with increasing oxidation temperature and time. In addition, internal oxidation occurred in the alloy matrix and formed mixed oxides, mainly at the pores and the alloy particles' interface during the oxidation process. Compared to the Fe-based alloy, the oxidation behaviour of the Fe-based coating presented different results. The mechanisms of oxidation behaviour at different temperatures and time, including oxide scale formation and in-situ internal oxidation in the Fe-based coatings matrix, are discussed.

Effects of Bias Voltages on the Structural, Mechanical and Oxidation Resistance Properties of Cr–Si–N Nanocomposite Coatings

Cr–Si–N nanocomposite coatings were deposited by multi-arc ion plating under different bias voltages. The influences of bias voltage on composition, microstructure, surface morphology and mechanical properties of Cr–Si–N nanocomposite coatings were investigated in detail. The HR-TEM, XRD, and XPS results confirmed the formation of nanocomposite structure of nanocrystalline of CrN embedded into the amorphous phase of Si3N4. The particle radius of CrN can be calculated from the half-width of the diffraction peak of CrN (200) and the value was about 20–60 nm. In addition, no diffraction peaks of CrSi2, Cr3Si, or Si3N4 were found in all the Cr–Si–N coatings. With the increasing of bias voltages from 0 to −200 V, the number and size of large droplets on the coating surface decreased, and the growth mode of the coatings changed from loose to dense. However, with the increasing of bias voltages from 0 to −200 V, the micro-hardness of the coatings increased and then decreased, reaching its maximum value at negative bias voltages of 100 V. It was found that the friction coefficient of Cr–Si–N coatings is almost the same except for the Cr–Si–N coatings deposited under bias voltage of 0 V. When the oxidation temperature was at 800 °C, the Cr–Si–N coating was only partially oxidized. However, with the increase of oxidation temperature to 1200 °C, the surface of the coating was completely covered by the oxide generated. The results showed that the bias voltages used in multi-arc ion plating had effects on the structure, mechanical, and high temperature oxidation resistance properties of Cr–Si–N nanocomposite coatings.

Platinum group metal and base metal on a molecular sieve for PNA-SCR-ASC close-coupled system

The oxidation process of soot particles in O2 and NO2 atmospheres is investigated in a flow reactor at various temperatures. The particles are generated using an ethylene diffusion flame and sampled at the tip of the flame using an ejector diluter sampling system. Soot is oxidized by three kinds of diluted gas (pure N2, 10000 ppm O2 with N2 and 10000 ppm NO2 with N2) in the flow reactor and measured with DMS500, transmission electron microscopy (TEM), high-resolution TEM, Raman microscopy and thermogravimetric analysis (TGA). The results show that the particle size, primary particle diameter, agglomeration degree and concentration of soot particles decrease as the oxidation temperature increases. The overall oxidation capacity of NO2 is stronger than that of O2 at low temperatures (200 and 400 °C), whereas at high temperatures (600 and 800 °C) O2 is stronger. Both internal oxidation and external oxidation exist during the oxidation process of soot with O2 and NO2. The average fringe length of the lattice increases and the tortuosity of the lattice and the Id/Ig ratios of the soot particles decrease as temperature increases, meaning that the nanostructure of the soot particles becomes more ordered. The results of the multi-diagnostics above indicate three main forms of oxidation during the overall oxidation process: internal oxidation, external oxidation and internal collapse. The oxidation of O2 is dominated by internal oxidation and internal collapse at high temperatures (600 and 800 °C), whereas the oxidation of NO2 is dominated by external oxidation throughout the oxidation temperature range.