High Temperature Oxidation Treatment Research Articles

Enhanced Corrosion Resistance of CuAl/BN Coatings through the Addition of Rare Earth Elements and High-Temperature Oxidation Treatment

Enhanced Corrosion Resistance of CuAl/BN Coatings through the Addition of Rare Earth Elements and High-Temperature Oxidation Treatment

Remarkable enhancement of the corrosive-wear resistance for Ti-Zr-Hf-Nb-Fe high-entropy alloys by a facile high-temperature oxidation treatment

The surface performances of TiZrHfNbFe refractory high-entropy alloys (RHEAs) were improved by a facile oxidation treatment at 1000 °C. Results indicated that the anomalous retarded oxidation behavior of the RHEA enabled the formation of a dense and robust oxide layer, demonstrating superior wear and corrosion resistance. The oxidation resistance of the RHEA was related to the development of Ti2ZrO6 on the surface and acicular HfO2 in the inner oxide layer. Additionally, the oxidation mechanism of the RHEA was elucidated, based on principles of oxidation thermodynamics and kinetics, providing foundations for applications as implant materials.

High-Temperature Oxidation of the 304/6061 Welding–Brazing Joint and Its Effects on Corrosion Characteristics

Laser–MIG hybrid welding–brazing was used to weld 304 stainless steel and 6061-T6 aluminum alloy with a thickness of 2 mm. The microstructure, morphology, chemical composition and corrosion behavior of the samples after high-temperature oxidation were investigated. The results reveal that the 304/6061 dissimilar joint had a thicker intermetallic compound layer (7–8 μm) during high-temperature oxidation (HTO) treatment than the sample without HTO treatment (2–3 μm). The oxide film thickness of the 6061 side of the weld joint treated by HTO (2401 nm) increased compared to the samples (181.1 nm) without HTO treatment. Unlike other metals treated by high-temperature oxidation, the high-temperature treatment process in this paper can reduce the corrosion resistance of the base metal and dissimilar joints, and the sequence of the corrosion current density was weld (HTO) >weld>6061 (HTO) >6061>304 (HTO) >304.

Structural control and mechanical properties optimization of porous SiC foams with three-dimensional network structure

In this paper, a new process for preparing porous SiC foam with three-dimensional network structure is presented. A certain thickness of SiC coating is deposited on the surface of ultra-light carbon skeleton by CVD process, so as to achieve effective control of its structure and mechanical properties. The effects of CVD deposition time on the density, porosity and skeleton thickness rates of SiC foams were explored. By increasing the CVD deposition time, the structure of SiC foams can be effectively regulated, and the mechanical properties of SiC foams can be significantly improved. The porosity of the prepared SiC foam can be adjusted in a wide range (26.9%∼94.68%). When the density of SiC foam increases from 0.67 g/cm3 to 2.36 g/cm3, its bending strength increases from 27.4 MPa to 136.9 MPa, which is significantly improved. After high temperature oxidation treatment (800–1200 °C), the mechanical properties of SiC foam will be further improved. However, when the oxidation temperature reaches 1400 °C, its mechanical properties will be reduced. This research provides a new idea for the preparation of high-performance porous SiC ceramics, and lays a foundation for its structural design, manufacture and application.

Optimization and Simulation Analysis of Furnace Structure for Regenerative Thermal Oxidizer

Volatile Organic Compounds (VOCs) significantly threaten the atmospheric environment. Currently, common methods for the recovery and treatment of VOCs include adsorption, solution absorption, photocatalytic oxidation, and high-temperature oxidation. Among them, the Regenerative Thermal Oxidizer (RTO) is a scheme for high-temperature oxidation treatment of VOCs, which applies aerospace heat transfer and combustion technology to the treatment of VOCs, and the removal efficiency of VOCs can reach over 99%. Considering the high temperature and possible instantaneous overpressure during the combustion process, a three-dimensional flow model of the bottom air distribution chamber and heat storage chamber was established to solve the technical difficulties of the gas flow field in the existing RTO and improve the safety and stability of the overall flow. Simulated the gas flow field and analysed the distribution pattern of the gas flow rate. In response to the uneven distribution of airflow caused by the pipeline layout, orifice plates were installed at the bottom of the furnace, and various orifice plate designs were considered. The results indicate that adding slanted orifice plates can improve flow conditions and enhance safety while meeting practical needs.

Improved passivation effect of additively manufactured WE43 porous scaffolds treated by high temperature oxidation in pure oxygen atmosphere

WE43 is a well-recognized magnesium alloy and has been successfully used in clinical biodegradable implants. High temperature oxidation (HTO) has been developed to inhibit fast degradation of WE43 alloy fabricated by laser powder bed fusion (L-PBF). This study involves constructing WE43 porous scaffolds via L-PBF, followed by HTO treatment using air (abbreviated as HTO-A) and pure oxygen (abbreviated as HTO-O) respectively. Electrochemical and immersion tests are performed to evaluate the oxidizing atmosphere’s influence on degradation. Compared with HTO-A, HTO-O achieves a denser and more continuous oxide layer and a thicker transition layer. The weight loss of HTO-O scaffold was 20.13 % after 14 days of immersion in Hank's solution, which was much lower than that of HTO-A scaffold (53.70 %), indicating that undergoing HTO treatment in pure oxygen markedly enhances the scaffold's corrosion resistance.

Synergistic selective photocleavage of lignin C–C bonds by triazine-rich tubular carbon nitride and high-temperature oxidation treatment

The key issue in lignin conversion depends on cutting the β-O-4 linkage bonds between units while keeping the aromatic ring intact. Triazine-heptazine homopolymers of carbon nitride are more prone to break the Cβ-H bond in the β-O-4 bond and generate the critical Cβ radical compared to the triazine or heptazine structure. Triazine-rich g-C3N4 was successfully prepared by ball milling-thermal polycondensation of melamine and cyanuric acid, which has the advantage of low cost and no desalting compared to the conventional eutectic salt method. The triazine-rich g-C3N4 has higher photocurrent density, lower photogenerated electron-transfer resistance, and less electron-hole recombination. Combined with high-temperature oxidation treatment, g-C3N4-O-Q-A5 has an excellent selective photocleavage efficiency of lignin β-O-4 bonds, which is 340 % higher than that of untreated g-C3N4. This paper reveals that the localization of holes in the photocleavage β-O-4 bond reaction, and the amount of superoxide radical generation are the main factors limiting the photocleavage efficiency.

High temperature oxidation treated 3D printed anatomical WE43 alloy scaffolds for repairing periarticular bone defects: In vitro and in vivo studies

Reconstruction of subarticular bone defects is an intractable challenge in orthopedics. The simultaneous repair of cancellous defects, fractures, and cartilage damage is an ideal surgical outcome. 3D printed porous anatomical WE43 (magnesium with 4 wt% yttrium and 3 wt% rare earths) scaffolds have many advantages for repairing such bone defects, including good biocompatibility, appropriate mechanical strength, customizable shape and structure, and biodegradability. In a previous investigation, we successfully enhanced the corrosion resistance of WE43 samples via high temperature oxidation (HTO). In the present study, we explored the feasibility and effectiveness of HTO-treated 3D printed porous anatomical WE43 scaffolds for repairing the cancellous bone defects accompanied by split fractures via in vitro and in vivo experiments. After HTO treatment, a dense oxidation layer mainly composed of Y2O3 and Nd2O3 formed on the surface of scaffolds. In addition, the majority of the grains were equiaxed, with an average grain size of 7.4 μm. Cell and rabbit experiments confirmed the non-cytotoxicity and biocompatibility of the HTO-treated WE43 scaffolds. After the implantation of scaffolds inside bone defects, their porous structures could be maintained for more than 12 weeks without penetration and for more than 6 weeks with penetration. During the postoperative follow-up period for up to 48 weeks, radiographic examinations and histological analysis revealed that abundant bone gradually regenerated along with scaffold degradation, and stable osseointegration formed between new bone and scaffold residues. MRI images further demonstrated no evidence of any obvious damage to the cartilage, ligaments, or menisci, confirming the absence of traumatic osteoarthritis. Moreover, finite element analysis and biomechanical tests further verified that the scaffolds was conducive to a uniform mechanical distribution. In conclusion, applying the HTO-treated 3D printed porous anatomical WE43 scaffolds exhibited favorable repairing effects for subarticular cancellous bone defects, possessing great potential for clinical application.

Investigation of the post-treatment process for improving corrosion behaviors and adhesion strength of plasma electrolytic oxidation (PEO) coatings on pure copper

The post-treatment processes of plasma electrolytic oxidation (PEO) coatings for corrosion behaviors and adhesion strength are investigated by surface analysis and electrochemical measurements. When the PEO coating is treated with high-temperature oxidation (HTO), silane coupling agent (SCA) mixed with benzotriazole (BTA) exhibits the optimal corrosion behaviors and adhesion strength, the icorr decreases to 0.65 ± 0.35 μA/cm2, ip decreases to 4.37 ± 0.42 μA/cm2, the Epit increases to 369.6 ± 0.4 mVSCE and the bonding strength increases to 14.2 MPa. That was mainly attributed to the corrosive medium with a longer diffusion path to the interface. Moreover, only the HTO treatment at 150 °C showed superior properties for long-time service, the icorr was 2.00 ± 0.17 μA/cm2, ip was 12.30 ± 0.09 μA/cm2, the Epit was −4.7 ± 0.2 mVSCE and the bonding strength was 10.0 MPa. That was ascribed to both the outer hydroxide and the inner oxide depicted the higher compactness.

Metal-free oxidized carbon nitride for efficient sunlight-driven photocleavage of lignin β-O-4 bond

Benefitting from mild reaction conditions and good reusability, photocatalysis has industrial potential for high-value utilization of lignin waste. Commonly used metal sulfide photocatalysts present the risk of contamination of aromatic products by heavy metal ions due to photocorrosion. Here, a metal-free oxidized g-C3N4 photocatalyst was developed to selectively cleave the β-O-4 bond of lignin. Simple high-temperature oxidation treatment reduced carbon nitride size and scavenged the terminal NH2 groups, resulting in higher oxygen adsorption capacity and valence band potential. In the photoelectric effect, oxidized g-C3N4 exhibited lower carrier migration resistance and a longer photogenerated electron lifetime. The high oxygen adsorption and specific surface area led to a 160 % increase in superoxide radicals. Two routes for the photocatalytic cleavage β-O-4 bond in g-C3N4 are proposed. The catalytic activity of oxidized g-C3N4 is 8.5 times higher than that of untreated g-C3N4, the selective photocleavage reactivity attributed mainly to more OOH radicals and higher valence band potential. This work will provide a green and efficient strategy for the high-value conversion of lignin.

Boron nitride nanosheets: Large-scale exfoliation in NaOH-LiCl solution and their highly thermoconductive insulating nanocomposite paper with PI via electrospinning-electrospraying

The miniaturisation of electronic components requires high-performance materials with insulating and thermal conductive properties for electronic packaging and thermal management. Boron nitride nanosheets (BNNS) are a desirable thermal conductive filler due to their excellent thermal stability, chemical stability, and high thermoconductivity. However, it remains challenging to mass produce ultra-thin large-scale BNNS and combine them with small amounts of polymers to fabricate malleable thermoconductive composites for flexible electronic devices. Herein, we report a new method to prepare BNNS at high yield by high-temperature oxidation treatment followed by hydrothermal exfoliation in NaOH-LiCl solution. We further fabricated flexible, insulating, and highly thermoconductive BNNS/PI (polyimide) nanocomposite paper, via a scalable layer-by-layer process that involves electrospinning of PI fibres and eletrospraying of BNNS. The prepared BNNS have a transverse size of 1.18 µm and a thickness of 1–2.9 nm, with a high yield of 75.48% at a concentration of 3.38 mg mL− 1. The BNNS/PI nanocomposite paper exhibited an ultrahigh in-plane thermal conductivity (7.58 W m−1 K−1), 2005% higher than that of the pure PI nanofibre composite. This simple method has wide application potential in next-generation electronic devices to design thermal interface materials with excellent electrical insulation, thermostability, and flexibility.

Raman Spectroscopy of Nascent Soot Oxidation: Structural Analysis During Heating

The effect of oxidation on nascent soot particles is investigated in this work by means of Raman spectroscopy. Three different soot particle samples are produced in a lightly sooting ethylene/air laminar premixed flame and collected at different residence times. The samples are characterized by a different size of primary particles and a different degree of aging and hence graphitization, and they are representative of the early evolution of nascent soot in flames. Oxidation of particles is induced by exposing the samples to a high temperature oxidation treatment in air over a range of temperature 25–500°C. To this aim, a programmable heating microscope stage is used. Thermo-optical transmission (TOT) measurements are used to characterize the chemical composition of pristine particles in terms of organic and elemental carbon content, also providing the pyrolytic carbon fraction of the organic carbon. The TOT results show that the organic fraction is constant for the three conditions. On the other hand, the pyrolytic carbon fraction decreases and the elemental carbon increases when moving from the sample composed of just-nucleated particles to the sample mostly made of mature soot particles. Raman spectroscopy reveals that the thermal oxidation treatment performed on the sample of just-nucleated particles, with the highest organic carbon content, results in a reduction of the amorphous carbon component. Conversely, the sample of mature soot, with the highest elemental carbon content, shows an increase in the amorphous carbon phase after oxidation, which is attributed to fragmentation or the formation of point defects by O2 oxidation. Finally, the thermal oxidation procedure produces a strong reduction in the photoluminescence signal detected from Raman spectra.

High temperature oxidation pre-treatment of textured c-Si wafers passivated by a-Si:H

This work shows an alternative surface cleaning method for c-Si wafers to replace the standard chemical procedures as RCA or HNO3 which involve hazardous chemicals or unstable processes. The method consists in a high-temperature oxidation treatment (HTO) performed in a classical tube furnace that incorporates organic and metal particles present on the c-Si surfaces in the growing SiO2 layer. The result is as a reliable pre-treatment method for obtaining less defective c-Si surfaces ready for solar cell fabrication after SiO2 removal. To test the surface passivation quality obtained with our alternative cleaning method, we grow amorphous silicon (a-Si:H) layers by plasma enhanced chemical vapor deposition on both sides of the c-Si wafer and systematically compare the effective carrier lifetime (τeff) and implied VOC (iVoc) to the wafer treated with the standard cleaning in our laboratory. We optimize HTO treatment time reaching τeff of ∼6 ms and iVoc of 721 mV for the best sample. We ascribe the improved passivation quality using HTO to two concurrent factors. Firstly, the encapsulation of defects into SiO2 layer that is then etched prior a-Si:H deposition and secondly, to modification of the pyramids' morphology that facilitates the surface passivation. SEM pictures and reflection measurements support the latter hypothesis.

Lifetime Enhancement of 4H-SiC PiN Diodes Using High Temperature Oxidation Treatment

In this paper, the application of a high temperature thermal oxidation and annealing process to 4H-SiC PiN diodes with 35 μm thick drift regions is explored, the aim of which was to increase the carrier lifetime in the 4H-SiC. Diodes were fabricated using 4H-SiC material and underwent a thermal oxidation in dry pure O2 at 1550◦C followed by an argon anneal at the same temperature. Reverse recovery tests indicated a carrier lifetime increase of around 42% which is due to increase of excessive minority carriers in the drift region. The switching results illustrate that the use of this process is a highly effective and efficient way of enhancing the electrical characteristics of high voltage 4H-SiC bipolar devices.

EFFECTS OF YTTRIUM NITRATE ON MICROSTRUCTURE AND HIGH TEMPERATURE RESISTANCE OF ZrO2–Y2O3 CERAMIC COATINGS PREPARED BY A MODIFIED PEO PROCESS ON AN Al–12Si ALLOY

A ZrO2–Al2O3 ceramic coating and YSZ–Al2O3 coating were prepared on ZAlSil2Cu3Ni2 alloys by a modified plasma electrolytic oxidation (PEO) in zirconium salt solution. The microstructure, heat-insulating and high temperature oxidation properties were investigated by SEM, XRD and a fabricated heat insulation temperature testing device. The results showed that the surface of the YSZ–Al2O3 coating was composed of fine particles and had lower roughness. Yttrium partially stabilized the zirconia solid solution (Y[Formula: see text]Zr[Formula: see text]O[Formula: see text] which was formed in zirconium yttrium salt solution with a higher reaction temperature. The growth rate of the YSZ–Al2O3 coating was greater than the ZrO2–Al2O3 coating. Especially, the outward growth obviously improves. Furthermore, the heat insulation property of the coating enhances. The curves of the weight gains in the sample with YSZ–Al2O3 coating showed a logarithmic shape under the high temperature oxidation treatment of 400[Formula: see text]C. The weight gains of the sample with YSZ–Al2O3 coating were relatively lower than that of the as-coated sample. The ceramic layer had good high temperature stability.

Effects of surface oxidation behavior of NiTi shape memory alloy on adhesion of epoxy resin/polytetrafluoroethylene composite coating

The nickel-titanium (NiTi) shape memory alloy (SMA) substrates were firstly subjected to different high-temperature oxidation treatments. Then they were sprayed by the polymer coating (epoxy resin (EP): polytetrafluoroethylene (PTFE) in a mass ratio of 3:1). Effects of the surface chemical composition, morphology, roughness and oxide thickness on adhesion between the NiTi SMA substrate and the coating were studied. The results demonstrated that the adhesion of the oxidized samples could be improved significantly as compared with that of the untreated sample. A heating temperature of 600 °C was determined to be optimal in the range of 300–700 °C for preparing the composite coating for NiTi SMA substrates. The highest adhesion strength was 6.76 MPa for the oxidized sample with a duration time of 30 min under 600 °C. It has been found that the adhesion was strongly depended on the high surface oxygen content, uniform morphology, appropriate roughness and oxide thickness.

In Situ Synthesis and Characterization of Fe-Based Metallic Glass Coatings by Electrospark Deposition Technique

Crystalline FeWMoCrBC electrode materials were prepared by conventional powder metallurgy. Metallic glass (MG) coatings were produced by electrospark deposition onto AISI 1035 steel in argon atmosphere. X-ray diffraction and scanning electron microscopy verified the amorphous structure of the as-deposited coatings. The coatings have a thickness of about 40 microns and a uniform structure. The results of dry sliding wear tests against high-speed steel demonstrated that Fe-based MG coatings had a lower friction coefficient and more than twice the wear resistance for 20 km sliding distance with respect to AISI 1035 steel. High-temperature oxidation treatment of the metal glass coatings at 1073 K in air for 12 h revealed that the oxidation resistance of the best coating was 36 times higher than that for bare AISI 1035 steel. These findings are expected to broaden the applications of electrospark Fe-based MG as highly protective and anticorrosive coatings for mild steel.

Influence of High-temperature Oxidation on Soft Magnetic Properties of Fe78Si9B13 Amorphous Alloy

Abstract The influence of high-temperature oxidation on soft magnetic properties of Fe78Si9B13 amorphous alloy was investigated using various analysis methods. The results reveal that a 10 μm thick iron oxide layer with high resistivity can be obtained on the surface of Fe78Si9B13 amorphous ribbons by high temperature oxidation treatment. It is found that the amorphous alloy magnetization becomes harder and the saturation induction density changes after the high-temperature oxidation. The saturation induction density value changes from Bs=1.42∼1.46 T without chemical oxidation, to Bs=1.29∼1.38 T after high-temperature oxidation. The factors which have a great effect on the magnetization difficulties of the amorphous ribbons were discussed.

Effect of strain relaxation of oxidation-treated SiGe epitaxial thin films and its nanomechanical characteristics

In this study, we examined the effect of high-temperature oxidation treatment on the SiGe epitaxial thin films deposited on Si substrates. The X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation techniques were employed to investigate the crystallographic structure, surface roughness, and hardness ( H) of the SiGe thin films, respectively. The high-temperature oxidation treatment led to Ge pileup at the surface of the SiGe thin films. In addition, strain relaxation occurred through the propagation of misfit dislocations and could be observed through the cross-hatch pattern (800–900 °C) and SiGe islands (1000 °C) at the surface of the SiGe thin films. Subsequent hardness ( H) measurement on the SiGe thin films by continuous penetration depth method indicated that the phenomenon of Ge pileup caused a slightly reduced H (below 50 nm penetration depth), while relaxation-induced defects caused an enhanced H (above 50 nm penetration depth). This reveals the influence of composition and defects on the structure strength of high-temperature oxidation-treated SiGe thin films.

La9.33Si6O26 electrolyte thin films for IT-SOFC application deposited by a HIPIMS/DC hybrid magnetron sputtering process

Apatite-type La9.33Si6O26 thin films were elaborated by co-sputtering of two metallic La and Si targets powered, respectively, by high power impulse magnetron sputtering and direct current sources, in pure Ar atmosphere, followed by a subsequent high temperature oxidation treatment in air. The structural and chemical features of these films have been assessed by X-ray diffraction and scanning electron microscopy (SEM). The film with near lanthanum silicate La/Si atomic ratio deposited on a porous Ni-YSZ cermet substrates was initially amorphous. After thermal oxidation at 1,173 K in air, the coating crystallised under the expected apatite structure. SEM observation revealed that both film compactness and thickness increased after thermal oxidation. The conductivity evolution with temperature of the pure apatite-like lanthanum silicate coatings, as measured by complex impedance spectroscopy, showed that the activation energy of is quite low compared to the literature data.