On-line electrolytic dissolution of alloys in flow-injection analysis. Part 3. Multi-elemental analysis of stainless steels by inductively coupled plasma atomic emission spectrometry

The simultaneous determination of chromium, nickel, manganese, silicon and iron in stainless steels was achieved by inductively coupled plasma atomic emission spectrometry (ICP-AES) after on-line electrodissolution using an improved flow-through electrolytic cell. The solution containing the electrodissolved ions was impelled by an air carrier stream in a flow-injection manifold towards a mixing-dilution chamber. From this chamber, the diluted and homogenized solution was aspirated and nebulized into the ICP torch. A quantification procedure is proposed for direct solid analysis without the use of certified reference materials. Under the proposed electrolysis conditions, up to 60 solid samples can be analysed per hour. Results obtained for alloying elements in austenitic and ferritic stainless steels were in good agreement with the certified values.     

Preparation and characterization of metallic membrane using wire arc spraying

Metallic membranes can be prepared by various techniques. This work introduces a novel method for the preparation of metallic membranes using wire arc spraying. The formed metallic membranes were characterized by metallographic techniques such as microscopy image analysis. The distance between gun and the substrate surface, which is called spray distance or gun distance, was selected as the variable of metal spraying. The effects of gun distance on coating properties and membrane performance were investigated. The metallographic and performance data showed that the range of 35–40 cm is the optimum gun distance for spraying. Ion rejection capability of the prepared membrane was tested using saline water as the feed. Moreover the filtration capability of the prepared membranes for blue indigo dye particles was investigated. Energy dispersive X-ray (EDX) analysis and SEM technique were used for the investigation of filtration mechanism. The results indicate that the prepared stainless steel membrane is able to efficiently remove particles from water.     

Catalytic Oxidation of Toluene, Acetone and Ethyl Acetate on a New Pt-Pd/Stainless Steel Wire Mesh Catalyst

A new volatile organic compound (VOC) combustion catalyst of 0.1%Pt-0.5%Pd/stainless steel wire mesh (SSWM) was prepared via anodic oxidation treatment. The result of activity tests for complete oxidation of toluene, acetone, and ethyl acetate showed that 0.1%Pt-0.5%Pd/stainless steel wire mesh catalyst had good catalytic activity and thermal stability. The total oxidation temperature for toluene, acetone, and ethyl acetate was at 220, 260, and 280 °C for the catalyst calcined at 500 °C, respectively. The catalyst and stainless steel wire mesh support were characterized by means of scanning electron microscopy (SEM), X-ray photoelectron spectrum (XPS), and ultrasonic vibration tests. The SEM results indicated that a typical donga structure layer appeared on the surface of stainless steel wire mesh support after anodic oxidation procedure. This typical anodic oxidation film was favorable for dispersing Pd and Pt components.     

Enhanced Adsorption of Epoxy-Functional Nanoparticles onto Stainless Steel Significantly Reduces Friction in Tribological Studies

Epoxy-functional sterically-stabilized diblock copolymer nanoparticles (ca. 27 nm) are prepared via RAFT dispersion polymerization in mineral oil. Nanoparticle adsorption onto stainless steel is examined using a quartz crystal microbalance. Incorporating epoxy groups within the steric stabilizer chains results in a two-fold increase in the adsorbed amount, Γ, at 20 °C (7.6 mg m⁻²) compared to epoxy-core functional nanoparticles (3.7 mg m⁻²) or non-functional nanoparticles (3.8 mg m⁻²). A larger difference in Γ is observed at 40 °C; this suggests chemical adsorption of the nanoparticles rather than merely physical adsorption. A remarkable near five-fold increase in Γ is observed for ca. 50 nm epoxy-functional nanoparticles compared to non-functional nanoparticles (31.3 vs. 6.4 mg m⁻², respectively). Tribological studies confirm that chemical adsorption of the latter epoxy-functional nanoparticles leads to a significant reduction in friction between 60 °C and 120 °C.     

High lithiophilic nitrogen-doped carbon nanotube arrays prepared by in-situ catalyze for lithium metal anode

Lithium metal has a very outstanding theoretical capacity(3860 mAh/g) and is one of the most superior anode materials for high energy density batteries.However,the uncontrollable dendrite growth and the fo rmation of "dead lithium" are the important hidden dangers of short cycle life and low safety.However,the uncontrollable dendrite growth and the fo rmation of dead lithium leads to short cycle life and hidden dange r,which hinder its practical application.Controlling the nucleation and growth process of lithium is an effective strategy to inhibit lithium dendrite.Herein,a simple in situ self-catalytic method is used to construct nitrogen doped carbon nanotube arrays on stainless steel mesh(N-CNT@SS) as a lithium composite anode.The N-doped CNTs provide a great number of N-functional groups,which enhance the lithiophilic of anode and provide a large number of uniform nucleation sites,hence it has excellent structural stability for cycles.The arrays provide neat lithium-ion transport channels to uniform lithiumion flux and inhibits dendrite generation,revealed by the COMSOL multi-physics concentration field simulation.The N-CNT@SS composite anode sustain stable at 98.9% over 300 cycles at 1 mA/cm2.NCNT@SS as the anode is coupled LiFePO_4(LFP) as the cathode construct a full battery,demonstrating excellent cycling stability with a capacity of 152.33 mAh/g and capacity retaining ratio of 95.4% after 100 cycles at 0.5 C.     

Effect of helium concentration on irradiation damage of Fe-ion irradiated SIMP steel at 300℃ and 450℃

SIMP steel is newly developed fully martensitic steel for lead-cooled fast reactors and accelerator-driven systems.It is important to evaluate its radiation resistance via high flux neutron irradiation, where dense He atoms can be formed via(n, α) transmutation reaction. Co-irradiation with Fe and He ions, instead of neutron, was performed. Specimens were irradiated with 6.4-Me V Fe ions to the damage dose of 5 dpa at a depth of 600 nm. Three different helium injection ratios of 60-appm He/dpa(dpa: displacements per atom), 200-appm He/dpa and 600-appm He/dpa at a depth of 600 nm,were performed. Two different irradiation temperatures of 300℃ and 450℃ were carried out. The effect of helium concentration on the microstructure of Fe-irradiated SIMP steel was investigated. Microstructural damage was observed using transmission electron microscopy. The formed dislocation loops and bubbles depended on the helium injection ratio and irradiation temperature. Lots of dislocation loops and helium bubbles were homogeneously distributed at 300℃, but not at 450℃. The causes of observed effects are discussed.     

Graphene oxide decorated with silver nanoparticles as a coating on a stainless‐steel fiber for solid‐phase microextraction

A novel graphene oxide decorated with silver nanoparticles coating on a stainless‐steel fiber for solid‐phase microextraction was prepared. Scanning electron microscopy and X‐ray photoelectron spectroscopy were used to characterize the coating surface and showed that silver nanoparticles were dispersed on the wrinkled graphene oxide surface. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined in the headspace solid‐phase microextraction mode. The extraction parameters including adsorption time, adsorption temperature, salt concentration, desorption time and desorption temperature were investigated. Under the optimized condition, wide linearity with low limits of detection from 2 to 10 ng/L was obtained. The relative standard deviations for single‐fiber repeatability and fiber‐to‐fiber reproducibility were less than 10.6 and 17.5%, respectively. The enrichment factors were from 1712.5 to 4503.7, showing the fiber has good extraction abilities. Moreover, the fiber exhibited a good stability and could be reused for more than 120 times. The established method was also applied for determination of polycyclic aromatic hydrocarbons in two real water samples and the recoveries of analytes ranged from 84.4–116.3% with relative standard deviations less than 16.2%.     

Autocatalytic nature of the bainitic transformation in steels: a new hypothesis

To ensure improvements in predicting the kinetics of bainite formation, it is important to understand the autocatalytic nature of the transformation so that this accelerating effect can be rigorously incorporated in kinetic models. In the present paper, it is assumed that the broad faces of bainitic plates in particular provide new potential nucleation sites for autocatalytic nucleation. The dislocations in the austenite near a bainitic plate are thought to stimulate autocatalysis because carbon is assumed to pile up at these regions and thereby other austenite–bainite interface regions may contain less carbon which promotes nucleation. Based on these assumptions, it is derived that the autocatalytic contribution is proportional to the volume fraction of as-formed bainite, which is consistent with the dependence proposed by Entwisle [V. Raghavan and A.R. Entwisle, Special Report No. 93, The Iron and Steel Institute, London, 1965, p.30] on the basis of empirical knowledge. In addition, it is assumed that autocatalytic nucleation can also depend on the morphology of bainite due to the associated difference in cementite precipitation. This new hypothesis for autocatalysis offers a viable explanation for the irregular variation in kinetics associated with the transition from upper to lower bainite measured for an alloy with eutectoid composition. Furthermore, comparison with experimental data of a Si-rich steel demonstrates that the isothermal kinetics of bainite formation can only be satisfactorily described when the autocatalytic factor is inversely proportional to the thickness of bainitic plates, which is consistent with the model proposed.     

Evolution of dislocation loops in austenitic stainless steels implanted with high concentration of hydrogen

Abstract

It has been found that under certain conditions, hydrogen retention would be strongly enhanced in irradiated austenitic stainless steels. To investigate the effect of the retained hydrogen on the defect microstructure, AL-6XN stainless steel specimens were irradiated with low energy (100 keV) H₂⁺ so that high concentration of hydrogen was injected into the specimens while considerable displacement damage dose (up to 7 dpa) was also achieved. Irradiation induced dislocation loops and voids were characterised by transmission electron microscopy. For specimens irradiated to 7 dpa at 290 °C, dislocation loops with high number density were found and the void swelling was observed. At 380 °C, most of dislocation loops were unfaulted and tangled at 7 dpa, and the void swellings were observed at 5 dpa and above. Combining the data from low dose in previous work to high dose, four stages of dislocation loops evolution with hydrogen retention were suggested. Finally, molecular dynamics simulation was made to elucidate the division of large dislocation loops under irradiation.