Metals, including austenitic steels and alloys, have been extensively applied in industrial and engineering applications. Passive films on metal surfaces are very important for corrosion protection. However, localized attack, such as passive film breakdown and the initiation of pits, is found upon exposure of such metals to aggressive ion-containing environments, leading to material failure and prominent adverse economic and safety concerns. For several decades, the mechanism of passivity breakdown and pit nucleation during pitting corrosion has been widely studied. The present article provides a detailed review of passive film breakdown on metal surfaces and the effects of complicated conditions, such as chloride- and sulfide-ion concentrations, temperature, and solution pH, on passivity breakdown. The possible mechanism for passivity breakdown is reviewed and discussed. The composition, structure, and electronic properties of passive layers are of conclusive importance to understand the leading corrosion mechanism, and they have been investigated with different techniques. Furthermore, we aim to present the structure, chemical composition, and electronic properties of passive films on metal surfaces by using X-ray photoelectron spectroscopy and energy-dispersive spectroscopy. Additionally, the surface morphology of passive films is analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) techniques. Finally, the effect of chloride- and sulfide-ion concentrations, pH, and temperature on passivity breakdown is discussed in detail.

The future photovoltaic technologies based on perovskite materials are aimed to build low tech, truly economical, easily fabricated, broadly deployable, and trustworthy solar cells. Hole transport material (HTM) free perovskite solar cells (PSCs) are among the most likely architectures which hold a distinctive design and provide a simple way to produce large-area and cost-effective manufacture of PSCs. Notably, in the monolithic scheme of the HTM-free PSCs, all layers can be printed using highly reproducible and morphology-controlled methods, and this design has successfully been demonstrated for industrial-scale fabrication. In this review article, we comprehensively describe the recent advancements in the different types of mesoporous (nanostructured) and planar HTM-free PSCs. In addition, the effect of various nanostructures and mesoporous layers on their performance is discussed using the electrochemical impedance spectroscopy (EIS) technique. We bring together the different perspectives that researchers have developed to interpret and analyze the EIS data of the HTM-free PSCs. Their analysis using the EIS tool, the limitations of these studies, and the future work directions to overcome these limitations to enhance the performance of HTM-free PSCs are comprehensively considered.

The electrospinning technique has been successfully used to prepared micro-fibers of the poly(lactic acid)/polyaniline–zinc oxide (PLA/PANI–ZnO) composite. The polyaniline–zinc oxide (PANI–ZnO) nanocomposites are synthesized by hydrothermal and in situ polymerization methods. X-ray diffraction techniques are used to study the structural properties of the PLA/PANI–ZnO composite fibers and the PANI–ZnO nanocomposite. The average crystallite size of the PANI–ZnO nanocomposite is found to be 36 nm. The morphology and diameter of the composite fibers are analyzed by scanning electron microscopy (SEM). The average fiber diameter of the pure poly(lactic acid) (PLA) fiber is around 2.5 μm and that of the PLA/PANI–ZnO composite fiber is around 1.4 μm. Differential scanning calorimetry (DSC) provides the thermal properties of the PLA/PANI–ZnO composite fibers. The melting temperature (T_m) for the pure PLA is observed at 149.3 °C, and it is shifted to 153.0 °C for the PLA/PANI–ZnO composite fibers. The enhanced thermal properties of the composite fibers are due to the interaction between the polymer and the nanoparticles. The water contact angle measurements probe the surface hydrophilicity of the PLA/PANI–ZnO composite fibers. The role of the PANI–ZnO nanocomposite on the sensing behavior of PLA fibers has also been investigated. The humidity sensing properties of the composite fiber based sensor are studied in the relative humidity (RH) range of 20–90% RH. The experimental results show that the composite fiber exhibited good response (85 s) and recovery (120 s) times. These results indicate that the one-dimensional (1D) fiber structure enhances the humidity sensing properties.

A flexible thin membrane made of a graphene–PANI nanocomposite decorated PS electrospun fibre as a highly sensitive carbon dioxide gas sensor.

Over the past decade, piezoelectric nanogenerator have attracted much attention to harvest mechanical energy from abundant resources in nature. Here, the ZnS microspheres is prepared by hydrothermal method and core-shell structured PANI/ZnS microspheres are synthesized by in situ polymerization method and then used as filler for the preparation of flexible [P(VDF-HFP)] based piezoelectric nanogenerator. The flexible P(VDF-HFP)/PANI-ZnS piezoelectric nanogenerator is prepared by Electrospinning technique. The core-shell PANI/ZnS composite improves the content of electroactive phase in [P(VDF-HFP)] and significantly improves the interfacial polarization between the PANI/ZnS particles and polymer matrix. Among all the samples, [P(VDF-HFP)]/2 wt% PANI-ZnS composite nanofibers exhibited the high piezoelectric peak-to-peak output voltage of 3 V compared with the neat [P(VDF-HFP)] (~ 120 mV). In addition, the high dielectric constant is observed for the [P(VDF-HFP)]/2 wt% PANI-ZnS composite nanofibers. These results implies that the fabricated flexible and efficient piezoelectric nanogenerator can be utilized for energy harvesting system.