Superconductivity at 57.3 K in La-Doped Iron-Based Layered Compound Sm<Subscript>0.95</Subscript>La<Subscript>0.05</Subscript>O<Subscript>0.85</Subscript>F<Subscript>0.15</Subscript>FeAs

Here, we report the synthesis and super- conductivity of the La-doped iron-based compound Sm_0.95La_0.05O_0.85F_0.15FeAs; the resistivity and magnetic measurement indicate that the onset transition temperature as high as 57.3 K. This compound has the same crystal structure as ZrCuSiAs type tetragonal layered structure. The higher T _c compares to SmO_0.85F_0.15FeAs was attributed to partly La-substitution.     

Characterization of Fe–Zn–R (R = rare earth metal) crystalline alloys as electrocatalysts for hydrogen evolution

The electrocatalytic properties of some Fe–Zn–R crystalline alloys (R=rare$\mathrm{R}=\mathrm{rare}$ earth metals), _Fe80Zn10La10${\mathrm{Fe}}_{80}{\mathrm{Zn}}_{10}{\mathrm{La}}_{10}$, _Fe80Zn10Y10${\mathrm{Fe}}_{80}{\mathrm{Zn}}_{10}{\mathrm{Y}}_{10}$, _Fe80Zn10Gd10${\mathrm{Fe}}_{80}{\mathrm{Zn}}_{10}{\mathrm{Gd}}_{10}$ and _Fe80Zn10MM10${\mathrm{Fe}}_{80}{\mathrm{Zn}}_{10}{\mathrm{MM}}_{10}$ (MM=mischmetal$\mathrm{MM}=\mathrm{mischmetal}$: 50.2% Ce, 26.3% La, 17.5% Nd, 6.0% Pr, at%), were investigated for the hydrogen evolution reaction (HER) in 1 M NaOH solution at 298 K. The microstructure of the electrodes was examined by optical microscopy and scanning electron microscopy coupled with electron probe microanalysis; X-ray diffraction measurements were also performed. The performances towards the HER were investigated by dc polarization and ac   impedance techniques and the results were compared with those obtained on polycrystalline nickel. The microstructural features play an important role in determining the electrocatalytic activity of the investigated alloys. The overall experimental data indicate that interesting electrocatalytic performances are displayed by the _Fe80Zn10Gd10${\mathrm{Fe}}_{80}{\mathrm{Zn}}_{10}{\mathrm{Gd}}_{10}$ electrode, which exhibits the highest activity towards the HER.     

Strategies to improve the catalytic activity of Fe-based catalysts for nitrogen reduction reaction

Electrochemical ammonia synthesis from N₂ under mild condition is considered a promising strategy to store energy produced by renewable sources, but it is affected by the lack of efficient catalysts for nitrogen reduction. In this work Fe-based nanoparticles with different morphology are deposited on carbon cloth via drop-casting and chemical reduction. The catalyst activity has been evaluated by cyclic voltammetry and chronoamperometry, using a 0.01 M phosphate buffered electrolyte (PBS). The produced ammonia has been determined through the indophenol method. As effective strategy to improve the catalytic activity, the morphology and particle size have been optimized and an electrochemical activation procedure has been implemented. Activation increases the available active sites and is related to higher amount of oxygen vacancies and Fe⁺²/Fe⁺³ ratio. Catalysts with optimized morphology produce ammonia at −0.35 V vs RHE with yield of 26.44 μg mg_cat⁻¹h⁻¹ and Faradaic efficiency of 20.4%, more than five times higher than without activation.     

Microstructural evolution of worn surface and subsurface of high Mn additive iron-based hardfacings subjected to repetitive impacts and sliding

In this article, a new impact-sliding wear test setup was developed to investigate the impact-sliding tribological/wear behavior of manganese (Mn) additive iron-based hardfacings. The effect of increased Mn content from 0 to 13 wt% on the wear characteristics was examined for a constant load of 200 N, 1000 impacts and 50 strokes/min speed. Hardness evaluation tests revealed that the hardness was increased after the impact-sliding wear tests. The worn surfaces of hardfacings/alloys/hardfacing alloys containing 0 and 8 wt% Mn presented a similar mechanism of micro-abrasion, but the damage caused by the abrasion in 8 wt% Mn additive hardfacings was not so effective in comparison to the hardfacing containing 0 wt% Mn. Above 8 wt% Mn addition, oxidative wear became the dominant wear mechanism with the formation of protective tribo-oxide layers and the wear trend exhibited enhancement in the wear resistance of hardfacings. On the other hand, subsurface analysis showed severe damage under the tribo-oxide layer, which revealed that the wear trend is not an exact indicator of wear resistance of the material. Wear behavior of the hardfacings has been successfully correlated with the hardness, morphology of the worn surfaces and subsurfaces.