Detailed tests and characterizations were used to investigate the corrosion degradation behaviors of Ti6Al4V alloys in simulated marine environments. These alloys suffered from very slight pitting and a miniscule weight loss of 0.018 mg/cm2 during the 50 cycle salt spray exposure but experienced significant oxygen erosion in the high-temperature oxidation test, resulting in a high weight gain of 2.657 mg/cm2 at 400 h. The oxidation and degradation reactions simultaneously occurred during the high-temperature hot salt test. The chlorine (Cl2) induced by the eutectic reaction of the mixed salts accelerated the degradation of the substrate and led to a higher weight gain of 4.265 mg/cm2 at 400 h. In contrast, this alloy suffered from severe corrosion damage during the high-temperature hot salt–water vapor synergy test. The degradation of TiO2, Al2O3, and V2O5 was aggravated by the synergistic action of chlorine salt and water. The reaction forming hydrochloric acid (HCl) further degraded the matrix metal and consequently led to a high weight loss of 16.358 mg/cm2 at 400 h. These current findings provide a comprehensive understanding for the degradation mechanisms of Ti alloys in these specific marine environments.
Pyrite (PR), as a representative sulfide mineral, possesses the advantages of abundant, thermodynamically stable, non-toxicity and semi-conductivity. In this study, an amperometric glucose biosensor (GOD/CS/PR/GCE) based on layer-by-layer of glucose oxidase (GOD), chitosan (CS) and pyrite (PR) on glassy carbon electrode (GCE) was fabricated through electrostatic force. In this research, PR suspension prepared in phosphate buffer (pH 5.5) was first immobilized on the GCE surface, which exhibits negative charge. Then, positively charged CS was adsorbed on PR/GCE by electrostatic force. Finally, negatively charged GOD was further modified on the CS/PR/GCE surface through electrostatic force again. The surface morphology and adsorbed mechanism were supported by field emission scanning electron microscopy (SEM), quartz crystal microbalance with dissipation (QCMD) and atomic force microscope (AFM). The step-by-step procedure gives both a strong adhesion ability and a good bioelectrocatalytic activity of GOD on the CS and PR modified electrode surface. The linear range of this GOD/CS/PR/GCE biosensor was achieved from 0.5 mM to 60 mM with the Linear regression equation of y = 0.897x -0.3016 (R 2 = 0.9996) and a limit of detection (LOD) value of 50 µM. This approach of using pyrite and chitosan as physical modified GOD to serve as electrostatic glues, which could be useful for designing better enzyme based biosensors for a wide variety of practical applications.
Low-grade magnesite is not effectively used mainly due to high silicon content, especially the separation of magnesite and hornblende. In this research, a novel mixture of sodium oleate and dodecyl phosphate collector was used to increase the flotation difference between magnesite and hornblende. Artificially mixed mineral concentrates grade 47.10% (MgO content) concentrate recovery of 84.45% was obtained by micro flotation test, the results showed that the mixed collector of sodium oleate and dodecyl phosphate played a better selective promotion role in the flotation of magnesite. The interaction mechanism of this mixed collector with hornblende and magnesite surfaces was investigated using Fourier transform infrared spectroscopy (FTIR), zeta potential, and X-ray photoelectron spectroscopy (XPS), which showed that the mixed collector in terms of magnesium selection was mainly adsorbed on these magnesium sites of magnesite, and the surface of magnesite thus became hydrophobic, allowing magnesite to float and separate from hornblende.
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