Cattail spike-like Co(OH)[email protected]3O4 nanoporous arrays were successfully prepared on nickel foam by hydrothermal method and calcination treatment. The Co(OH)[email protected]3O4 nanoarrays, combining the advantages of the Co(OH)F and the Co3O4, exhibit ultrahigh structural stability and excellent electrochemical performance. The specific capacitance of Co(OH)[email protected]3O4 is 543F g−1 at the current density of 1A g−1 and could maintain 88.34 % specific capacitance after 5000 cycles at 10 A g−1. Moreover, a two-electrode system assembled by Co(OH)[email protected]3O4 and reduced graphene oxide exhibits a peak energy density of 30.155 Wh kg−1 at the power density of 800 W kg−1 and possesses an excellent cycling retention of 84.88 % after 5000 cycles at 10A g−1. These results indicate that the prepared Co(OH)[email protected]3O4 composite is a promising positive electrode material for supercapacitors. 

Cattail spike-like Co(OH)F@Co3O4 nanoarrays for high-performance supercapacitors

In this work, unique Co3O4/N‐doped reduced graphene oxide (Co3O4/N‐rGO) composites as favorable sulfur immobilizers and promoters for lithium–sulfur (Li–S) batteries are developed. The prepared Co3O4 nanopolyhedrons (Co3O4‐NP) and Co3O4 nanocubes mainly expose (112) and (001) surfaces, respectively, with different atomic configurations of Co2+/Co3+ sites. Experiments and theoretical calculations confirm that the octahedral coordination Co3+ (Co3+Oh) sites with different oxidation states from tetrahedral coordination Co2+ sites optimize the adsorption and catalytic conversion of lithium polysulfides. Specially, the Co3O4‐NP crystals loaded on N‐rGO expose (112) planes with ample Co3+Oh active sites, exhibiting stronger adsorbability and superior catalytic activity for polysulfides, thus inhibiting the shuttle effect. Therefore, the S@Co3O4‐NP/N‐rGO cathodes deliver excellent electrochemical properties, for example, stable cyclability at 1 C with a low capacity decay rate of 0.058% over 500 cycles, superb rate capability up to 3 C, and high areal capacity of 4.1 mAh cm−2. This catalyst's design incorporating crystal surface engineering and oxidation state regulation strategies also provides new approaches for addressing the complicated issues of Li–S batteries.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/advs.202202352

Oxidation States Regulation of Cobalt Active Sites through Crystal Surface Engineering for Enhanced Polysulfide Conversion in Lithium–Sulfur Batteries

In order to obtain a nitriding layer with thicker ductile diffusion layer and thinner brittle compound layer, plasma nitriding with titanium addition was carried out at 540 °C for 4 h for 42CrMo steel, the characteristic of titanium modified nitriding layer and the enhanced properties were systematically investigated by optical microscope (OM), scanning electron microscope (SEM), XRD, hardness tester and wear tester etc. The results show that titanium addition can effectively modify the characteristics of nitrided layer, and thus a plasma nitrided layer owning thicker ductile diffusion layer and thinner brittle compound layer and higher surface hardness can be obtained. Titanium addition can significantly decrease the compound layer and increase the effective hardening layer, and also greatly enhance the surface hardness, especially with the optimal amount of 0.8 g, the compound layer can be reduced from 19 μm to 10 μm, while the effective hardening layer can be increased from 225 μm to 370 μm. And the surface hardness can be enhanced from 703HV 0.05 to 889HV 0.05 , more importantly, both wear resistance and toughness can be greatly promoted by the novel titanium modified plasma nitrided layer, attributed to the formation of dispersedly distributed TiN particles with very high hardness in the nitriding layer. 

Titanium-modified Plasma Nitriding Layer and Enhanced Properties for 42CrMo Steel

The microstructure and corrosion behavior of metastable austenitic stainless steel (MASS) 14Cr10Mn in acidic 1 wt.% NaCl solution were investigated by X-ray diffraction (XRD), electron back scatter diffraction (EBSD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurement techniques. Cold rolling deformation noticeably increases the contents of martensites and microdefects in the steel. All specimens show active–passive transition during the anodic polarization process. With changing the cold rolling reduction from 0% to 20%, the active corrosion rate markedly increases about 55%, whereas the pitting potential slightly decreases about 80 mV. The cold rolling deformation clearly facilitates the preferential dissolution of Fe and Cr as well as the enrichment of Cu on the metal surface in the corrosion process. The small shallow grooves and pits form at the deformation band regions. 

Corrosion behavior of cold-rolled metastable Cr-Mn-Ni-N austenitic stainless steel in acidic NaCl solution

The effect of dry/wet ratios on the corrosion process of the 6061 Al alloy in simulated Nansha marine atmosphere

Corrosion evolution and stress corrosion cracking behavior of a low carbon bainite steel in the marine environments: effect of the marine zones

In order to enhance the plasma nitriding efficiency and improve the hardness and wear resistance of 316L austenitic stainless steel, severe plastic deformation was adopted prior to plasma nitriding. The microstructure, phase constituents, hardness and wear resistance samples after plasma nitriding were determined by metallographic microscope, X-ray diffractometer, microhardness tester and universal friction and wear tester. The results showed that severe plastic deformation had significant enhancement effect on plasma nitriding efficiency. Under the same plasma nitriding parameters of 420 °C and 4 h, the thickness of nitriding layer was increased from 6.36 μm to 14.10 μm, more than twice thicker enhanced by severe plastic deformation. XRD confirmed that the nitriding layer is consisted of S phase. Meanwhile, the surface hardness was improved from 990HV to 1110 HV and with moderated gradient of cross sectional hardness; more valuably, the wear resistance was greatly enhanced by severe plastic deformation.

Heng Ma

Papers

Corrosion evolution and stress corrosion cracking behavior of a low carbon bainite steel in the marine environments: effect of the marine zones

Enhanced plasma nitriding efficiency and properties by severe plastic deformation pretreatment for 316L austenitic stainless steel

Oxidation States Regulation of Cobalt Active Sites through Crystal Surface Engineering for Enhanced Polysulfide Conversion in Lithium–Sulfur Batteries

Defect-rich porous tubular graphitic carbon nitride with strong adsorption towards lithium polysulfides for high-performance lithium-sulfur batteries

Performance enhancement by novel plasma boron-nitriding for 42CrMo4 steel