Effect of Annealing on Microstructure and Corrosion Behavior of Interstitial Free Steel

Interstitial free steels with various grain sizes and textures were prepared by cold-rolling followed by an annealing process. The effect of grain size, crystallographic orientations and stored energy on corrosion behavior of interstitial free steel was investigated. It was found that the deformed microstructure and dislocation boundaries were consumed by recrystallizing grains during annealing. The average grain size increase ranging from 0.61 μm to 11 μm and the volume fraction of recrystallized grains was about 96% after annealing for 64 h; meanwhile, the γ fiber was the dominated recrystallized texture component. The stored energy gradually decreased due to the reduction in dislocation density by annealing. The potentiodynamic polarization and Nyquist plots show that the corrosion potential exhibits a more positive shift and depressed capacitive semicircle radius increase with rising annealing time. The 64 h annealed specimens had the biggest depressed semicircle in the Nyquist plots and the highest positive corrosion potential, which indicates the enhancement of corrosion resistance. Such an improvement of corrosion resistance is attributed to the increase in the volume fraction of the γ fiber and decrease in the stored energy.

Model Electrochemical Biosensor for the Detection of Methanol in Aqueous Solutions with Yeast Cells

An electrochemical device that serves as a model biosensor and contains yeast Saccharomyces cerevisiae as the active biological element was developed. Different configurations of the electrochemical cells were assembled and tested. Stainless steel was used in the electrochemical cell composition process and the surface of this metal electrode was modified with a thin layer of WO3 if necessary. The yeast Saccharomyces cerevisiae was adhered to the working electrode. The resulting model biosensor was then used to monitor the response to a 10% CH3OH. For detection of biological activity, the electrochemical impedance spectroscopy (EIS) method was applied with a portable potentiostat/galvanostat, where the Bode and the Nyquist plots were interpreted. The stability of the device was beforehand determined by measuring the open circuit potential (OCP). The topography of the electrodes was inspected using the techniques of scanning electron microscopy and optical microscopy. The investigated model biosensor as a case study for the development of more complex biosensors that utilize living cells as the active layer.

Study on the Perspective of Mechanical Properties and Corrosion Behaviour of Stainless Steel, Plain and TMT Rebars

In the present research, the effects of various alloying elements and microstructural constituents on the mechanical properties and corrosion behaviour have been studied for four different rebars. The microstructures of stainless steel and plain rebar primarily reveal equiaxed ferrite grains and ferrite-pearlite microstructures, respectively, with no evidence of transition zone, whereas tempered martensite at the outer rim, followed by a narrow bainitic transition zone with an internal core of ferrite-pearlite, has been observed for the thermomechanically treated (TMT) rebars. The hardness profiles obtained from this study display maximum hardness at the periphery, which decreases gradually towards the centre, thereby providing the classical U-shaped hardness profile for TMT rebars. The tensile test results confirm that stainless steel rebar exhibits the highest combination of strength (≈755 MPa) and ductility (≈27%). It has been witnessed that in Tafel plots, the corrosion rate increases for all the experimental rebars in 1% HCl solution, which is well expected because the acid solutions generally possess a higher corrosive environment than seawater (3.5% NaCl) due to their acidic nature and lower pH values. However, all the experimental results obtained from Tafel and Nyquist plots correlate well for both 1% HCl and 3.5% NaCl solutions.

Elevated Electrochemical Performance of LiNi0.1Mg0.1Co0.8O2 and LiFePO4 Cathodes with Tris(2,2,2-trifluoroethyl) Phosphite as an Efficient Electrolyte Additive

The significant role of Tris(2,2,2-trifluoroethyl) phosphite (TTFP) as an efficient additive during cycling of the layered nanostructured LiNi0.1Mg0.1Co0.8O2 and olivine LiFePO4 cathode materials in EC/DMC and 1M LiPF6 electrolyte for Li-ion battery are extensively investigated in this work. The electrochemical characterization techniques such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy show that TTFP improves cycling stability and reduces the irreversible capacity of LiNi0.1Mg0.1Co0.8O2 and LiFePO4 electrodes. Also, the presence of TTFP in electrolyte solution reduces the impedance in LiNi0.1Mg0.1Co0.8O2 and LiFePO4 cathode materials at room temperature. A family of Nyquist plots was obtained from LiNi0.1Mg0.1Co0.8O2 and LiFePO4 electrodes for various potentials during the course of charging. The addition of TTFP in the electrolyte reduces the surface impedance of lithiated LiNi0.1Mg0.1Co0.8O2 and LiFePO4 which can be attributed to the reaction of the additive on the electrode’s surface. Also, the presence of the additive TTFP in LiNi0.1Mg0.1Co0.8O2 and LiFePO4 cell enhances the lithium diffusion rate and improves the electronic conductivity of the cathode material.

Electrochemical Anodic Synthesis and Analysis of TiO2 Nanotubes for Biomedical Applications

Nowadays, titanium and alloy materials are encouraged for biomedical applications. Fabrication of the passive layer over the titanium materials is limited. Typically, a plain titanium sample is not suitable for bioimplant applications because the adhesion of biological elements like blood cells, tissues, and bones is poor. The use of surface-modified titanium resolves this issue. Surface modifications on titanium by electrochemical methods are simple and cost-effective. The addition of water to the ethylene-based electrolyte-enhanced the oxidation process to increase the length of the nanotubes. Surface morphological analysis shows that the length of the nanotubes has been increased, nanoindentation analysis delivers that increasing the length has been increased the hardness level, and corrosion analysis indicates that the length of nanotubes encouraged the corrosion resistance. Potentiodynamic polarization, Bode and Nyquist plots were models fit analyzed with equivalent electrical circuits. Sample cell viability was characterized with NIH-3T3 cells using an inverted microscopy analyzer.

Electrical properties of cation-substituted Ag7(Si1–xGex)S5I single crystals

High-quality single crystals of Ag7(Si1–xGex)S5I (x = 0.2, 0.4, 0.6, 0.8) solid solutions are grown from the solution–melt by vertical zone crystallization method. The measurements of electrical conductivity of Ag7(Si1–xGex)S5I solid solutions were performed using the impedance spectroscopy method within the frequency range from 10 Hz up to 2·106 Hz and temperature interval 293–383 K. Ionic and electronic components of electrical conductivity, as well as their ratios, were determined using the Nyquist plots.

Assimilation of Zinc Metal Ion With Hydroxyapatite for Formation and Dielectric Studies

The aim of the present work is to investigate the doping effect of Zn metal ions on hydroxyapatite for different concentrations (0.2, 0.4, 0.6, and 0.8). The samples for the pure and Zn doped HAp are synthesized by wet chemical precipitation method. The properties and the particle size are identified by using XRD. The functional bands of PO, CO and OH are analyzed through FTIR and the surface morphology and particle shapes are studied through SEM. The elemental analysis such as zinc, calcium and phosphates are analyzed by EDAX. All the designed elements are studied and confirm the (Ca+Zn)/PO ratio is nearly 1.67 and no other elements were identified in this study. The morphological particles of needle shape and the nanoscale particle size and shapes are studied by using TEM. The electrical conductivity of the synthesized ZnHAp ceramic is mainly related to width of the channel and the polarizability. The dielectric loss and nyquist plots were studied by using impedance spectroscopy.

Electrospun highly corrosion-resistant polystyrene–nickel oxide superhydrophobic nanocomposite coating

A key challenge in producing superhydrophobic coatings (SHC) is to tailor the surface morphology on the micro-nanometer scale. In this work, a feasible and straightforward route was employed to manufacture polystyrene/nickel oxide (PSN) nanocomposite superhydrophobic coatings on aluminum alloys to mitigate their corrosion in a saline environment. Different techniques were employed to explore the influence of the addition of NiO nanoparticles to the as-prepared coatings. PSN-2 composite with ~ 4.3 wt% of NiO exhibited the highest water contact angle (WCA) of 155° ± 2 and contact angle hysteresis (CAH) of 5°. Graphic abstract EIS Nyquist plots of 3 g of electrospun polystyrene coatings (a) without and with (b) 0.1, (c) 0.15, and (d) 0.2 g of NiO.

Tetragonal–Cubic Phase Transition and Low-Field Dielectric Properties of CH3NH3PbI3 Crystals

The frequency and temperature dependence of dielectric properties of CH3NH3PbI3 (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes’ interfaces.

Stability of negative feedback

“Stability of negative feedback” discusses the measures that must be taken to guarantee that a negative-feedback system is stable. Examples are given of frequency dependences using Bode and Nyquist plots. Safety margins are quantified by means of gain margins and phase margins; the desirability of a minimum-phase-lag network. A design procedure is formulated. There is discussion of Nyquist (conditional) stability, and how it may be achieved by judicious introduction of a non-linearity. A demonstration circuit shows that these measures can yield Nyquist stability with safety.