Thermal Oxidation Treatment Research Articles

Metal Organic Frameworks‐Derived NiO/NiCo2O4 Heterostructures for Effective Methanol Oxidation Reaction

AbstractThe electrochemical process of methanol oxidation reaction (MOR), which is closely associated with electrochemical production of formate and hydrogen, is considered a highly viable avenue for advancing renewable energy technologies. Nevertheless, the development and creation of affordable, effective, and durable electrocatalysts for MOR continue to present significant obstacles. In this study, a hierarchical porous NiO/NiCo2O4/NF electrode is fabricated through the integration of solvothermal and thermal oxidation treatments of Ni‐MOF‐74 and NiCo‐Asp. After thoroughly assessing the electrochemical performance for MOR, NiO/NiCo2O4/NF demonstrates a significant current density of 140 mA cm−2 at 1.6 V (vs. RHE) and a tafel slop of 45.0 mV·dec−1 in 1 M KOH and 0.5 M methanol. The excellent performance of MOR can be ascribed to the hierarchical porous nature that enhances mass and electron transport while offering numerous active sites for electrocatalytic reactions. Additionally, the hetero interface between NiO and NiCo2O4 could further enhance electron transfer rate and reaction kinetics for the MOR. The developed NiO/NiCo2O4/NF electrode shows potential as a viable and economical alternative to Pt‐based electrocatalysts for MOR‐based applications.

Manufacturing of heavy tungsten alloys from nano-sized metal oxides via simultaneous reduction-sintering powder treatments

Heavy tungsten alloys are of great importance in the engineering and mining industries as well as the military and medical applications because of their stability at high temperatures, high strength and dense structures. The present study develops a novel technology for the production of heavy tungsten alloys via thermal treatment of nano-sized metal oxides based on simultaneous reduction and sintering processes. Heavy tungsten alloy (95W-3Ni-2Fe) was produced from the reduction of mixed nano-sized metal oxides precursor in H2 at 1000 o C followed by sintering at 1350–1450 o C for 30–90 min. The reduced and sintered samples were characterized by XRD to follow up the crystallinity, total porosity measurement was used to find out the densification properties, the grain structure and morphology were examined by RLM and SEM attached with EDAX. Micro-hardness tester was also used to investigate the influence of sintering conditions on the grain densification. A fundamental study on the kinetics of reduction of mixed nano-sized metal oxides precursor was performed by isothermal and non-isothermal techniques. Both results from isothermal and non-isothermal tests were used to calculate the activation energy which was correlated with macro- and micro-structures to predict the corresponding reduction mechanism. However, the influence of sintering temperature and time on the crystallinity of the produced phases, grain structure, morphology, total porosity, pore-size distribution, bulk and apparent densities, and the hardness of sintered compacts was extensively investigated. The results revealed that the presence of NiO and/or Fe2O3 in the mixed metal oxides precursor was very important to ease the reducibility of WO3 as the metallic phases of Ni and/or Fe act as a catalyst for the reduction of WO3. The rate of reduction proceeds faster in the following order: NiO > Fe2O3 > mixed oxide > WO3. In non-isothermal experiments, it was found that the heating rate has a considerable effect on the reduction of precursor, i.e., the lower the heating rate, the higher the degree of reduction. It might be reported that the use of nano-sized metal oxides particles in the fabrication of heavy tungsten alloys greatly affects the main properties of the produced alloy. With the increase in sintering time, larger sizes of dense grains were developed, and the matrix became denser as a result of sintering and re-crystallization effects. The higher the sintering time, the higher the grain densification and the less pores formed in the matrix. On the other hand, with the increase in the sintering temperature, the grain boundaries were well defined in which the grains were composed of tungsten metal and surrounded by inter-metallics. The higher the temperature, the higher the XRD peak intensities of metallic tungsten and intermetallics as a result of sintering and re-crystallization.

Formation of a protective oxides-nitrides compound layer with enhanced wear properties, corrosion resistance, and cytocompatibility on novel Ti-Zr-Nb-Ta-Mo multi-principal element alloy

The insufficient surface properties of multi-principal element alloys (MPEAs) hinder their potential biomedical applications. Here, a facile thermal oxidation plus nitridation treatment is conducted to fabricate a protective layer on a novel Ti-Zr-Nb-Ta-Mo MPEA. The total surface layer of NT5-ON consists of a top compound layer, including TiO2, TiN, TiON, ZrO2, and ZrN, and an underneath N-diffusion zone, leading to an exceptionally high wear performance. Also, electrochemical testing and in-vitro evaluations demonstrated enhanced corrosion resistance and cytocompatibility of NT5-ON. As a result, thermal oxidation plus nitridation treatment is an effective technique for designing high-performance hip implant materials.

Microwave-Assisted Pyrolysis of Carbon Fiber-Reinforced Polymers and Optimization Using the Box-Behnken Response Surface Methodology Tool.

This article introduces an eco-friendly method for the reclamation of carbon fiber-reinforced polymers (CFRP). The research project involved numerous experiments using microwave-assisted pyrolysis (MAP) to explore a range of factors, such as the inert gas flow, the power level, the On/Off frequency of rotation, and the reaction duration. To design the experiments, the three-level Box-Behnken optimization tool was employed. To determine the individual and combined effects of the input parameters on the thermal decomposition of the resin, the data were analyzed using least-squares variance adjustment. The results demonstrate that the models developed in this study were successful in predicting the direct parameters of influence in the microwave-assisted decomposition of CFRPs. An optimal set of operating conditions was found to be the maximum nitrogen flow (2.9 L/min) and the maximum operating experimental power (914 W). In addition, it was observed that the reactor vessel's On/Off rotation frequency and that increasing the reaction time beyond 6 min had no significant influence on the resin elimination percentage when compared to the two other parameters, i.e., power and carrier gas flow rate. Consequently, the above-mentioned conditions resulted in a maximum resin elimination percentage of 79.6%. Following successful MAP, various post-pyrolysis treatments were employed. These included mechanical abrasion using quartz sand, chemical dissolution, thermal oxidative treatment using a microwave (MW) applicator and thermal oxidative treatment in a conventional furnace. Among these post-treatment techniques, thermal oxidation and chemical dissolution were found to be the most efficient methods, eliminating 100% of the carbon black content on the surface of the recovered carbon fibers. Finally, SEM evaluations and XPS analysis were conducted to compare the surface morphology and elementary constitution of the recovered carbon fibers with virgin carbon fibers.

Study on the decay behavior of a flexible sensor based on silver fiber fabrics

Abstract Flexible sensors are affected by various external factors during their use, such as water, thermal oxidation, and ultraviolet light, which causes a decrease in their sensitivity, but little research has been done in this area. This paper investigates the effects of washing, acid, ultraviolet, and thermal oxidation treatments on flexible sensors made of silver fiber fabrics, and the sensitivity and sensing performance before and after the treatments are compared. The findings show that the flexible sensor in use has a broad response range (0–70%) and strong stability (>1000 cycles). The sensitivity decreased significantly after washing, acid treatment, UV treatment, and thermal oxidation treatment but maintained good stability after 1000 tensile cycle tests.

Oxidation Study and Mechanism Analysis of Desulfurization Ash in Dense-Phase Tower

Dense-phase-tower desulfurization technology is an emerging semi-dry flue-gas desulfurization ash process, i.e., the flue gas is allowed to enter the desulfurization tower from the bottom up and, at the same time, is sprayed with a desulfurizing agent that undergoes an acid–base reaction with the flue gas in the ascent process. The calcium sulfite and calcium sulfate produced by the reaction and the part of the desulfurization agent that is not involved in the reaction will enter the subsequent dust removal system, and what is retained is the by-product desulfurization ash. This desulfurization ash contains a large amount of calcium sulfite, which leads to its unstable nature; it is easily oxidized and expands in volume, and, if used in the field of building materials, it will lead to cracking and other problems, so it is difficult to effectively use it. In order to solve this problem, XRF, XRD, and iodometric and other analytical methods were used to determine the specific composition of desulfurization ash, and the muffle furnace and vertical tube furnace were used to study the thermal oxidative modification of calcium sulfite in desulfurization ash, to investigate the effects of the oxygen content, reaction temperature, medium flow rate, and chloride content on the oxidation of calcium sulfite, and to analyze the thermodynamics in the high-temperature oxidation reaction. The results showed that the oxidation rate of calcium sulfite increased with higher reaction temperatures. Increased oxygen content promoted the oxidation rate, particularly at low oxygen levels. The oxidation rate of calcium sulfite correlated positively with the medium flow rate until a rate of 75 mL·min− was reached. At a reaction temperature of 420 °C and a gas flow rate of 85 mL·min−1, the oxidation conversion efficiency exceeded 89%. Chloride content significantly reduced the oxidation rate of calcium sulfite, although this inhibition weakened at temperatures above 500 °C. Kinetic analysis suggested that the oxidation reaction of calcium sulfite predominantly occurred below 500 °C. These findings have both theoretical and practical implications for the thermal oxidation treatment and disposal of desulfurization ash.

Observation of Structural Changes during Oxidation of Black and Brown Soot Using Raman Spectroscopy

In this study, Raman spectroscopy has been used to evaluate the evolution of the structural modification of soot during oxidation processes at various preset temperatures up to 700 °C. Two types of well-characterized mini-CAST soot, representing black soot and brown soot, were examined. The major difference between the signals from the two types of soot was the higher photoluminescence (PL) signal for brown soot compared with black soot, in addition to some variations in the first-order Raman signatures such as oxygenated groups and their evolutions during thermal oxidation treatment. An interesting observation was the increase in the PL signal for brown soot at increasing temperatures up to 150 °C probably due to the formation of small oxidized polycyclic aromatic hydrocarbon and defects, followed by a decrease in the PL signal until the soot was fully oxidized. We also demonstrated that brown soot is prone to oxidation in ex situ measurements, a factor that should be considered in the Raman analysis of soot.

Study on High-Temperature, Ultra-Low Wear Behaviors of Ti6Al4V Alloy with Thermal Oxidation Treatment

Thermal oxidation (TO) is a simple and economical way to enhance the wear resistance of the Ti6Al4V alloy. The TO temperature has a very important effect on the tribological properties of the TiO2 layer formed. However, the impact of the oxidation temperature on the high-temperature tribological behavior of a TO-treated Ti6Al4V alloy is not clear. Therefore, the Ti6Al4V alloy was oxidized at 400 °C, 600 °C, and 700 °C for 36 h, and the sliding friction experiments were conducted at room temperature (RT) and 400 °C with a Si3N4 ball as the counter body to comparatively study the effect of the oxidation temperature on the high-temperature friction behavior of the TO-treated Ti6Al4V alloy. The results show that the TO treatment can effectively improve the wear resistance of the samples at both room and high temperatures. Among them, the oxidation-treated samples at 700 °C show the best wear resistance, with a reduction of 92.6% at high temperatures; the amount of wear loss at room temperature was so small that it was almost incalculable. At room temperature, the friction surface formed uneven agglomerate formations, resulting in an elevated coefficient of friction (CoF) compared to the untreated samples. At a high temperature, however, the CoF is reduced compared to the untreated samples due to the formation of a homogeneous transfer film in the wear area that is caused by the interaction of Si3N4 and oxygen.

Deposition of FeOOH Layer on Ultrathin Hematite Nanoflakes to Promote Photoelectrochemical Water Splitting.

Hematite is one of the most promising photoanode materials for the study of photoelectrochemical (PEC) water splitting because of its ideal bandgap with sufficient visible light absorption and stability in alkaline electrolytes. However, owing to the intrinsically high electron-hole recombination, the PEC performance of hematite is still far below that expected. The efficient charge separation can be achieved via growth of FeOOH on hematite photoanode. In this study, hematite nanostructures were successfully grown on the surface of iron foil by the simple immersion deposition method and thermal oxidation treatment. Furthermore, cocatalyst FeOOH was successfully added to the hematite nanostructure surface to improve charge separation and charge transfer, and thus promote the photoelectrochemical water splitting. By utilizing the FeOOH overlayer as a cocatalyst, the photocurrent density of hematite exhibited a substantial 86% increase under 1.5 VRHE, while the onset potential showed an apparent shift towards the cathodic direction. This can be ascribed to the high reaction area for the nanostructured morphology and high electrocatalytic activity of FeOOH that enhanced the amount of photogenerated holes and accelerated the kinetics of water splitting.

Efficient water oxidation performance of CdxZn1-xIn2S4 /(S, N)-TiO2 modulated with sulfur vacancies

We developed an efficient photoelectrochemical system with high photoconversion ability and long-term stability based on a type-II heterojunction between (S and N) co-doped TiO2 (SNT) and CdxZn1−xIn2S4 (CZIS) via a two-step hydrothermal process. The optimization of the Cd-to-Zn ratio improved the water oxidation rate and thermal treatment was conducted to introduce sulfur vacancies into the CZIS crystal structure. Theoretical investigations confirmed the improved water oxidation tendency of CZIS owing to the deterioration of the water oxidation kinetics. The effect of doping, presence of sulfur vacancies, and coupling with SNT resulted in superior charge separation and hole-injection tendencies. The optimized SNT/CdxZn1−xIn2S4 (Vs) sample exhibited a high photocurrent density of 3.1 mA cm−2 at 1.23 V vs. RHE, which was 2.4 times that of SNT. The photoconversion efficiency of the prepared heterostructure was further augmented by the deposition of a co-catalyst, resulting in a maximum photoconversion efficiency of 1.5 %, H2 gas evolution rate of 60 μmol/h, and 99 % faradic rate efficiency after 5 h of photoelectrochemical water-splitting reaction. The detailed band alignment between the two semiconductors was investigated using different techniques to determine the charge-transfer mechanism and verify the role of each component.

The impact of thermal treatment parameters on the preservation of carbon fiber mechanical properties after reclamation

Carbon fiber, despite its exceptional properties, remains underutilized due to monetary and environmental concerns. Concurrently, the imminent challenge associated with rising quantities of End-of-Life CFRP (carbon fiber reinforced polymer) demands the further development of recycling strategies. This study focuses on optimizing the recycling process parameters of pyrolysis and oxidation thermal treatment to maximize the retention of mechanical properties in the recycled fibers in the shortest process time. To assess the result of the pyrolysis, single fiber tensile tests were executed to measure strength and stiffness. Additionally, microscopy and spectroscopy studies were carried out to evaluate fiber geometry as well as surface quality. At the laboratory scale, experiments demonstrated that the combination of pyrolysis and oxidation yields clean, reusable fibers with mechanical properties suitable for secondary applications. The influence of various treatment parameters on the strength and stiffness of the recycled fibers was explored, establishing a clear correlation. The outcome is a set of optimized parameters that contribute to mechanical property retention, including a novel recycling method that allows for reduced processing times, as short as 10 min. This work paves the way for a more eco-friendly and cost-effective approach to harnessing the potential of carbon fiber in a wide range of applications while mitigating environmental concerns associated with landfill disposal.

Selective synthesis of soft and hard carbons from a single precursor through tailor-made stabilization for anode in sodium-ion batteries

A major factor in classifying carbon materials is their degree of graphitization, which is defined as a structural transition from an amorphous to an ordered crystalline state. Previous studies have shown that graphitization depends on the intrinsic properties of precursors for carbon materials. Thus, these studies on graphitization have been mainly limited to modulating precursors. Herein, we demonstrate the degree of graphitization that can be governed by a stabilization process using polyethylene (PE) as a single precursor, as PE is a non-graphitizable material. PE is stabilized by e-beam irradiation and subsequent thermal oxidation or sulfuric acid treatments to investigate the effects of stabilization methods. The resulting thermally and acid-stabilized PEs are graphitized up to 2,000 °C, and surprisingly, they diverge from a single precursor into soft and hard carbons, respectively. We also confirm that laser desorption/ionization time-of-flight mass spectrometry is a powerful analytical tool for revealing the different structures of thermally and acid-stabilized PEs at the early stage of graphitization based on the formation patterns of carbon cluster ions. In addition, the distinct electrochemical performances of soft and hard carbons are investigated by applying them as anode materials into sodium ion batteries, respectively. We believe that this study provides fundamental insights and practical tools to develop tailor-made carbon materials from a single and common precursor.

Nanoporous ALD-modified oxygen-deficient NiO flakes as anodes for lithium-ion batteries

The flake-like nature of materials possessing continuous porous skeletons makes them naturally suited for energy storage and other applications. Nickel oxide (NiO) stands out as a highly attractive anode material for lithium-ion batteries due to its relatively high theoretical specific capacity. Nevertheless, the sluggish kinetics of its reactions and significant volume variations during cycling curtail its rate capability and electrochemical stability. In this work, we successfully fabricate nanoporous oxygen-deficient NiO@Al2O3 flakes by a multi-step process involving magnetron sputtering deposition, subsequent thermal oxidation treatment, and a particle atomic layer deposition surface coating technique. The resultant nanoporous oxygen-deficient NiO@Al2O3 flakes demonstrate the potential to establish an intricate network that facilitates efficient charge transfer, rapid ion diffusion, and mechanical robustness throughout electrochemical processes. Particularly noteworthy is the role of the ultrathin Al2O3 coating, which greatly bolsters the cycle life. When employed as lithium storage materials, the nanoporous NiO@Al2O3 flakes exhibit remarkable attributes, including high specific capacity (720 mAh g−1 at 25 mA g−1), superior rate capability (300 mAh g−1 at 5000 mA g−1) and sustained cycling ability, showcasing a reversible capacity of 413 mAh g−1 after 500 cycles at 150 mA g−1 (equivalent to a duration exceeding 4 months). Moreover, the distinctive morphologies and compositions observed after extended cycles definitively corroborate the efficacy of the nanoporous flake architecture. Finally, we present a full-cell configuration comprising a NiO@Al2O3 flakes anode paired with a LiNi0.8Mn0.1Co0.1O2 cathode, which notably exhibits remarkable cycle stability, retaining 84.2 % of its capacity after 100 cycles at 200 mA g−1. This effective and versatile strategy might hold promise for extension to alternative anode and cathode materials, potentially enabling enhanced specific capacity and rendering them suitable for energy storage applications.

Development of non-combustible weaveable yarn through oxidative control of a textile acrylic fibre

Acrylic fibre is considered to be artificial wool in the textile industry, but in contrast with natural wool, it vigorously burns producing black smoke and toxic gases. This not only has hindered its technical applications, but also poses safety risks to the end-users of acrylic-based products. This research aims at enhancing the fire-retardancy of acrylic yarns using a facile thermal stabilisation process which is based on controlling the oxidation temperature and residence period. To this end, acrylic yarns are thermally processed according to six different time and temperature profiles ranging from 220 to 280 °C, with residence periods ranging from 22 to 28 min. The oxidised yarns were characterised using FTIR, DSC, and TGA techniques and the effects of the oxidative thermal treatment on physical characterises, and surface morphology of yarns and fibres were discussed. The results showed that the acrylic yarn undergone the oxidation process based on 240–255–270–280 °C heating profile for 28 min at each step had a sufficiently high degree of cyclisation with an excellent fire retardancy. Furthermore, the stabilised acrylic yarn was strong enough to be woven into a plain weave fabric using a laboratory scale loom while displaying non-combustible behaviour during cyclic exposure to flame. These results present a novel pathway for the development of a low cost, non-combustible fabric ideally suited for applications in extreme environments.

Surface modified walnut shell derived carbon particles for anti-acne skin treatment

Applied materials from bio-wastes are becoming the center of attention for researchers due to convincing concerns for their effectiveness, bio-sustainability, affordability, and environmental friendliness. In this research, different forms of carbon particles (CP) were produced from walnut shells to check their response against acne. Surface chemistry of CPs was modified in two steps: first, by thermal or oxidative-thermal treatment, and second, by biochemical treatment with the drugs triamcinolone acetonide (TA) or hydrocortisone sodium succinate (HSS) at pH 4 and 7. Prepared CPs have been analyzed for their surface chemistry, morphology and bioactivity. With the exception of GTOT, surface modifications have decreased oil absorption capacity and drug release pattern while increasing dispersion, pH and base contents. The GTOT and PTOT-N1 samples exhibited highest oil absorption capacities of 0.137 g/0.05 g and 0.130 g/0.05 g, respectively. Additionally, thermal and thermo-chemical modifications have slightly decreased in-vitro anti-inflammatory activity but substantially decreased cytotoxicity (almost 5–6 folds in comparison to unmodified particles). Anti-inflammatory response has been checked against P. acnes. Among various prepared samples, it was observed that Bio-PUT-4 and Bio-PTOT-7 exhibited the most significant levels of anti-inflammatory activity, at 94.19 % and 93.54 % respectively. Thermally modified samples, additionally, have shown magnetic behavior.

Improved resistance to chloride-induced corrosion through the combined influence of surface nanocrystallization and thermal oxidation treatments on AISI 321 stainless steel

This study comparatively examines the impact of combined surface nanocrystallization (SNC) and thermal oxidation (TO) treatments on the corrosion performance of AISI 321 austenitic stainless steel under chloride-induced conditions, highlighting their synergistic effects. To achieve this goal, the SNC process was first carried out using the high energy shot peening technique and then the TO treatment was performed by exposing the samples to Ar–21% O2 at 400 °C. The oxide films grown on both solution annealed (SAed) and the high energy shot peened (HESPed) samples show a double-layered structure: an inner Cr-rich and an outer-Fe rich layer. However, high density and uniform distribution of the crystallographic defects on the HESPed sample remarkably increased the Cr diffusion/flux throughout the oxidation front, and consequently a thicker Cr-rich inner oxide layer formed on the surface, as compared with the SAed one. A number of electrochemical examinations were conducted to investigate the corrosion behavior of oxidized and non-oxidized SAed and HESPed samples in 3.5 wt% NaCl solution. It was found that the oxidized HESPed sample shows the best corrosion performance with the highest values of critical pitting potential (+590 mV vs. Ag/AgCl) and charge transfer resistance (356.7 kΩ cm2). A physical model based on the surface microstructural evolution caused by the TO and SNC treatments and their synergistic effect on the formation of Cr-rich phases is provided.

Copolymers and terpolymers of vinyl phosphonic acid, acrylonitrile, methyl acrylate, and vinyl acetate. Thermal oxidative stabilization and their nanofiber

ABSTRACT Copolymers and terpolymers of acrylonitrile (AN), methyl acrylate (MA), vinyl acetate (VA), and vinyl phosphonic acid (VPA) were synthesized. Thermal gravimetric analysis studies showed that the decomposition of PANMAVPA and PANVAVPA terpolymers started at lower temperatures than PANMA and PANVA copolymers. VPA and MA caused an increase in the ring formation of pendant nitrile groups and the total ash content of PANMAVPA terpolymer. During the thermal oxidative treatment (TOS) of PANVAVPA, the phosphonic acid moiety accelerated double bond formation via acetic acid elimination. 151–340 nm nanofibers were successfully produced from copolymers and terpolymers.

Improved wear and corrosion resistance of biomedical TiZrNbTaMo medium-entropy alloy by thermal oxidation treatment

Thermal oxidation treatment was carried out on novel TiZrNbTaMo biomedical Medium-entropy alloy (bio-MEAs) at 400∼600 °C for 2 h in air. The extracted results demonstrated that the oxide layer was mainly composed of oxides of Zr and Ti, in which the content of ZrO2 and TiO2 with high hardness increased with the increase of oxidation temperature, leading to enhanced wear resistance (wear rate reduced from ∼10−4 to ∼10−5 mm3/N⋅m). Likewise, the oxide layer also improves the corrosion resistance of the alloys. The results showed that thermal oxidation can be used as an effective surface treatment method to broaden the application prospects of bio-MEAs.

New strategies for the management of a primary refinery oily sludge: A techno-economical assessment of thermal hydrolysis, Fenton, and wet air oxidation treatments

Petroleum refinery wastewater treatment plants produce a significant amount of oily sludge, a hazardous waste that requires proper disposal. It is necessary to develop technologies to treat and valorise it, avoiding the current environmental problems associated with its landfill disposal. This work explores the application of different advanced technologies for the pre-treatment and further valorisation of this oily sludge, which includes thermal hydrolysis, Fenton oxidation, and wet air oxidation. These treatments reduce the solid content by 51–78%. Moreover, the increasing dewaterability and settleability facilitate phase separation, thus enabling further valorisation, obtaining an aqueous effluent more biodegradable (ca. 63%). A conceptual design based on experimental data obtained at bench scale has been developed for the three pre-treatment systems under study. Techno-economic analysis of the three advanced treatments gave unitary costs ranging from 78 €/m3 for thermal hydrolysis to 192 €/m3 for the Fenton treatment, which are all in the low range of the current management cost (70–350 €/m3). Thus, the techno-economic analysis developed in this study demonstrates its feasibility compared to the current management of oily sludge from API separators. Thermal hydrolysis can be a low-cost and suitable strategy for producing biodegradable effluent that can be directly treated in the conventional biological treatment plant of the refinery. However, WAO might be a more appropriate option to recover carbon and nutrients for further valorisation in advanced biological processes.

Femtosecond laser surface processing combined with thermal oxidation for enhancing corrosion resistance of AZ31B magnesium alloy in chloride solutions

A novel method of ultrafast femtosecond laser surface processing (FLSP) combined with the post thermal oxidation (TO) treatment was employed to improve the corrosion resistance of AZ31B magnesium (Mg) alloys. FLSP with laser powers (< 100 mW) mainly creates the nanostructures on AZ31B alloy surfaces, while the higher laser powers (> 200 mW) induce the hierarchical micro/nanostructures. According to the electrochemical results, the corrosion resistance of AZ31B alloys in Cl− solutions is weakened after the FLSP. However, an obvious enhancement in corrosion resistance is found when the femtosecond (fs) laser-processed samples subjected to the TO treatment in the temperature range from 100 °C to 280 °C. TO treatment actually supports the oxidation and growth of the nanostructure to form a dense film, considerably improving its protective ability and enhancing the corrosion resistance of Mg alloys in Cl− solutions. The uniform corrosion is evidently inhibited and localized corrosion emerges on laser-processed samples after the TO treatment.