ABSTRACT
2,5-dihydroxy-1,4-dithiane (DDD) and 2,5-dimethy- [1.4] dithiane-2,5-diol (DTDD) two food flavors as environmentally-friendly inhibitors for Cu in 0.5 mol/L H2SO4 media were researched via theoretical calculation and experimental ways. Electrochemical measurement data showed that DDD and DTDD can exhibit high level anti-corrosion feature. The anti-corrosion efficiency of DDD and DTDD were as high as 99.6% and 98.9%, respectively. The atomic force microscope (AFM) and scanning electron microscope (SEM) tests showed that the Cu specimens were immersed in the H2SO4 with 5 mM DDD and DTDD for 30 h at the 298 K, and the Cu specimen surface was still smooth. Besides, the adsorption of DDD and DTDD at the interface of Cu/solution was comply with Langmuir adsorption. Theoretical calculation data showed that DDD exhibit more ascendant anti-corrosion feature than DTDD.
Subject(s)
Copper , Steel , Corrosion , Sulfuric AcidsABSTRACT
Magnesium-based materials are promising lightweight structural materials due to their excellent properties. However, their extensive application has been severely limited due to their high corrosion susceptibility. The inadequate corrosion resistance of Mg is mainly attributed to the porous and unprotective native surface film formed on Mg in aggressive environments. Here, we demonstrated a new environment-friendly route for the growth of a continuous nesquehonite (MgCO3·3H2O) protective film on the surface of pure Mg metal at a relatively low temperature via an in situ reaction of the Mg surface with gaseous phase CO2 in humid environments. The protective film consists solely of highly crystalline MgCO3·3H2O that is compact and has an umbrella-like structure. Electrochemical tests showed that compared to the untreated Mg substrate, the protective film can effectively improve the corrosion resistance of the substrate by nearly two orders of magnitude. Additionally, a possible formation mechanism of the nesquehonite film on the pure Mg was proposed and the effect of the carbonation time on the film was investigated. This environmentally-friendly surface treatment method is promising for use in the protection of magnesium-based materials.
ABSTRACT
A popular issue of recent scientific research is the surface modification induced by plastic deformation, such as ultrasonic shot peening (USP) on workpiece surface. USP is an efficient way to improve the mechanical behavior of specimens by inducing severe plastic deformation on their surface. Nevertheless, this surface treatment induced complex microstructural evolutions, such as grain refinement and phase transformation. In this work, the microstructure and properties of 347 austenite steel samples before and after USP for 5, 10, and 15 min treatments have been investigated. The affected layers show a significant hardness increase (~450 µm in depth) on the USP treated surface, and the 10 min USP treated specimen shows the best corrosion resistance in all tested specimens. The magnetic properties and microstructures of the tested specimens show gradient evolution during deformation.
ABSTRACT
Magnetoelectric multiferroic fluids composed of BaTiO3@CoFe2O4 composite nanoparticles dispersed in a highly insulating nonpolar oleic acid/silicone oil mixture have been developed. The effects of the particle volume fraction and a magnetic field, as well as an electric field, on the ferroelectric and magnetic properties, as well as the magnetoelectric coupling effect, have been systematically studied and discussed in this paper. Magnetic characterization shows an approximation to superparamagnetism, and both the remanent magnetization (Mr) and the coercive field (Hc) increase with increases in the volume fraction and applied electric field. Similarly, a superparaelectric state has been observed in the multiferroic fluids, in which both the remanent polarization (Pr) and the coercive field (Ec) are near zero, whereas they increase with increases in the applied magnetic field and volume fraction. High converse and direct magnetoelectric coupling coefficients are estimated to be αH = 8.16 × 10-4 (Oe cm) V-1 and αE = 1.58 × 104 V (cm Oe)-1, respectively. Further analysis indicates that the composite particles can be aligned under an external magnetic/electric field so that their magnetic/electric moments can be parallel to the external field, which in turn results in changes in the magnetization/polarization directions. These results imply that besides magnetoelectric fluids that consist of core/shell-structured nanoparticles, conventional multiferroic fluids based on composite particles may provide an opportunity to gain electrical control of magnetization and vice versa, which implies potential applications.
