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Potentiodynamic and cyclic voltammetric studies were carried out on nickel in borate buffered saline (pH = 8.49). The anodic excursion spans of nickel in borate buffer solution do not involve active/passive transition. The passive film starts to break down in the presence of Cl-ions, which causes pitting damage. The data reveal that the increasing Cl− concentration and solution temperature shifts the Epit to the active direction while the increasing in scan rate shifts the Epit to the positive direction. The pitting potential (Epit) shifted in a positive direction when increasing concentrations of Wo4−2 and MoO4−2 anions were added to a borate buffer solution containing Cl− ions, showing that the additional anions had an inhibitory influence on the pitting corrosion. While the NO3− anion is ineffectual as an inhibitor and rather speeds up pitting corrosion, the NO2− anion has a slight inhibitory impact on pitting corrosion. [ABSTRACT FROM AUTHOR]

In this study, a high-density ZrN/ZrSi2 composite reinforced with ZrO2 as an inert phase was synthesized under vacuum starting with a Zr-Si4N3-ZrO2 blend using combustion-synthesis methodology accompanied by compaction. The effects of ZrO2 additions (10–30 wt%) and compression loads (117–327 MPa) on the microstructure, porosity and hardness of the samples were studied. The process was monitored using XRD, SEM, EDS, porosity, density and hardness measurements. Thermodynamic calculations of the effect of ZrO2 addition on the combustion reaction were performed including the calculation of the adiabatic temperatures and the estimation of the fractions of the liquid phase. The addition of up to 20 wt% ZrO2 improved the hardness and reduced the porosity of the samples. Using 20 wt% ZrO2, the sample porosity was reduced to 1.66 vol%, and the sample hardness was improved to 1165 ± 40.5 HV at 234 MPa. [ABSTRACT FROM AUTHOR]