Yashar Behnamian

A-site deficient perovskite: the parent for in situ exsolution of highly active, regenerable nano-particles as SOFC anodes

Chemical deposition is widely used to enhance the performance of perovskite anodes for solid oxide fuel cells (SOFCs). However, the anodes thus produced still have unsatisfactory activity and experience reproducibility problems. For the first time, this paper reports that the in situ exsolution of nano-Ni could be facilitated on Ni-doped (La0.7Sr0.3)CrO3 (LSCNi) anodes with A-site deficiency, showing a maximum power density of 460 mW cm−2 in 5000 ppm H2S–H2 compared to only 135 mW cm−2 of fuel cells with stoichiometric LSCNi. Besides, the fuel cell also demonstrates desirable redox stability in sour fuel. The introduction of A-site deficiency can help the formation of highly mobile oxygen vacancies and remarkably enhance the reducibility of Ni nano-particles, thus significantly increasing electronic conductivity and catalytic activity simultaneously. Such fabricated perovskite has the potential to be decorated with diverse nano-active particles for a wide range of applications in industrial fields.

Detection of corrosion degradation using electrochemical noise (EN): review of signal processing methods for identifying corrosion forms

Electrochemical noise (EN), as one of the most promising in situ electrochemical methods in corrosion and electrochemical science, has been developing rapidly in recent years with the advancements in instrumentation and signal processing methods. One advantage of EN is its application in long-term or early stage corrosion process monitoring because it instantly detects corrosion rate and corrosion forms. Investigators have applied various mathematical methods to extract characteristic parameters from EN. In this paper, identifying corrosion forms using parameters obtained from time domain, frequency domain and time–frequency domain is reviewed, and the correlation between parameters and corrosion forms is discussed. Finally, other in situ techniques are recommended to be employed synchronously with EN measurement in order to obtain reliable analyses.

Electrochemical noise: a review of experimental setup, instrumentation and DC removal

The electrochemical noise (EN) experiment and instrumentation aspects are briefly summarized, and the direct current (DC) removal methods before EN analysis are illustrated. The results show that poly-nominal trend removal, wavelet analysis and Empirical mode decomposition are effective for DC removal whereas average trend removal and linear trend removal are not suitable for DC removal.

Semiconductivity of steam generator tubing alloys in simulated crevice chemistries containing lead and sulphur

Semiconductivity of passive films on steam generator (SG) tubing alloys, Alloys 690 and 800, in simulated crevice chemistries containing lead and sulphur was investigated using the Mott–Schottky analysis. The interaction of the above species with other ions on the properties of passive film and the correlation between the semiconductivity and the breakdown of passive film were discussed. Experimental results revealed that semiconductivity could be either n or p type semiconductor; both Pb and S can incorporate into the passive layer, depending on the solution pH and alloy compositions. For n type semiconductors formed on Alloy 800, they are easily broken down but more resistant to anodic dissolution; for p type passive films formed on Alloys 690 and 800, they are not easily broken down but more prone to anodic dissolution. It is concluded that the semiconductivity of passive film on SG tubing alloys was dependent on the alloy compositions, the solutions, temperature and film formation potentials.

Brief data overview of differently heat treated binder jet printed samples made from argon atomized alloy 625 powder.

Powder bed binder jet printing (BJP) is an additive manufacturing method in which powder is deposited layer-by-layer and selectively joined in each layer with binder. The data presented here relates to the characterization of the as-received feedstock powder, BJP processing parameters, sample preparation and sintering profile (“Effect of solutionizing and aging on the microstructure and mechanical properties of powder bed binder jet printed nickel-based superalloy 625” (A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016) [1], “Powder bed binder jet printed alloy 625: densification, microstructure and mechanical properties” (A. Mostafaei, E. Stevens, E. Hughes, S. Biery, C. Hilla, M. Chmielus, 2016) [2]). The data presented here relates to the characterization of the as-received feedstock powder, BJP processing parameters, sample preparation and sintering profile. Effect of post heat treatments including solutionizing and aging on the microstructure and mechanical properties of powder bed binder jet printed nickel-based superalloy 625 were compared to that of sintered samples.

Electrochemical noise monitoring of the atmospheric corrosion of steels: identifying corrosion form using wavelet analysis

ABSTRACT The early stage atmospheric corrosion of T91 and Q235B steels exposed to Tianjin’s urban atmosphere over 20 days was studied using two electrochemical probes via an electrochemical noise (EN) technique. To identify the corrosion process and the corrosion form of the two steels, EN data were analysed by statistics and wavelet transform. The results revealed that the wavelet energy of decomposed EN mainly located at high-frequency level for Q235B steel, whereas it mainly located at the low-frequency level for T91 steel. Analyses of surface images confirmed that Q235B steel underwent uniform corrosion whereas T91 steel suffered from localised corrosion. The obtained noise resistance correlated well with weight loss data. GRAPHICAL ABSTRACT

Pitting growth rate on Alloy 800 in chloride solutions containing thiosulphate: image analysis assessment

ABSTRACT The growth rate of pits formed on Alloy 800 in chloride solutions containing various thiosulphate concentrations was assessed by potentiostatic polarisation, in situ corrosion image observation, and image analysis. The pitting growth rate was a function of solution chemistry: in chloride solution pits were small but numerous, in chloride + thiosulphate solution, the pits were large. Competitive adsorption on Alloy 800 of chloride and thiosulphate ions affected the pitting potential and therefore the pitting growth rate on the metal. The reduction of thiosulphate to elemental sulphur accelerated the pitting growth rate in chloride + thiosulphate solutions.

An investigation into the dissolution characteristics of γ precipitates in Mg-3Al-Zn alloy

In non-equilibrium conditions, the coring phenomena may occur in the α-Mg solid solution and γ-Mg17Al12 phase forms in the microstructure of AZ magnesium alloy series. This eutectic phase may introduce detrimental effect on workability of wrought alloys. In the present work, the dissolution characteristics of γ phase have been investigated in AZ31 wrought magnesium alloy. Considering the eutectic temperature of AZ31 alloy, the homogenization treatment was executed in temperature range of 300-437 oC (i.e., somewhat below eutectic melting temperature of γ precipitate) and 437-500 oC (i.e., higher eutectic melting temperature of γ precipitate) for different durations. A thorough microstructural investigation and also thermodynamic calculations were executed. The results indicated that the dissolution rate of γ phase is very low even at temperatures just below the eutectic point of the alloy, whereas it dramatically increases at temperatures higher than eutectic point. Moreover, it is suggested that partial melting of γ phase due to eutectic melting reaction (α+γ→L) may lead to reduced formability.

Effect of Tricalcium Magnesium Silicate Coating on the Electrochemical and Biological Behavior of Ti-6Al-4V Alloys

In the current study, a sol-gel-synthesized tricalcium magnesium silicate powder was coated on Ti-6Al-4V alloys using plasma spray method. Composition of feed powder was evaluated by X-ray diffraction technique before and after the coating process. Scanning electron microscopy and atomic force microscopy were used to study the morphology of coated substrates. The corrosion behaviors of bare and coated Ti-6Al-4V alloys were examined using potentiodynamic polarization test and electrochemical impedance spectroscopy in stimulated body fluids. Moreover, bare and coated Ti-6Al-4V alloys were characterized in vitro by culturing osteoblast and mesenchymal stem cells for several days. Results demonstrated a meaningful improvement in the corrosion resistance of Ti-6Al-4V alloys coated with tricalcium magnesium silicate compared with the bare counterparts, by showing a decrease in corrosion current density from 1.84 μA/cm2 to 0.31 μA/cm2. Furthermore, the coating substantially improved the bioactivity of Ti-6Al-4Valloys. Our study on corrosion behavior and biological response of Ti-6Al-4V alloy coated by tricalcium magnesium silicate proved that the coating has considerably enhanced safety and applicability of Ti-6Al-4V alloys, suggesting its potential use in permanent implants and artificial joints.

In-situ Study the Corrosion Degradation Mechanism of Tinplate in Salty Water by Scanning Electrochemical Microscopy

In this work, the corrosion degradation of tinplate in contact with salty water is investigated by scanning electrochemical microscopy (SECM) electrochemical impedance spectroscopy (EIS). Experimental results indicate tin maintains at passive state during the exposure; however, pores and defects existed in tin coating leads to an exposure of carbon steel substrate to the electrolyte, in which localized corrosion tends to occur within the pore. A phenomenological model is proposed to interpret corrosion mechanism of tinplate in contact with salty food based on the proposed electrochemical equivalent circuit.