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The atomic interactions between Si and Mn during eutectoid transformation in high-carbon pearlitic steel were investigated. Atom probe tomography and first-principles calculations were applied to evaluate and analyze the atomic interactions at the ferrite/cementite interface. In the initial stage of eutectoid transformation, enrichment of Si and Mn occurred at the ferrite and cementite sides, respectively, of the interface. This interfacial segregation phenomenon gradually diminished as the transformation proceeded. Calculations of the cohesive energy and formation energy revealed a clear enhancement in the chemical bonding and stability of the pearlite system when the Si atom was moved from the ferrite layer to the cementite layer and the Mn atom was moved in the opposite direction. The interfacial segregation of the Mn and Si atoms was mainly responsible for the insufficient diffusion and high hybridization degree of Fe, Mn, Si, and C atoms. Furthermore, the partitioning ratio of Mn in high-Si steel was greater than that in low-Si steel, leading to greater partitioning of Mn into the cementite phase. Calculations of the electronic structure revealed that the enrichment of Si in the ferrite phase promoted the partitioning of Mn into the cementite phase owing to the strong repulsive force between Mn and Si at the pearlitic interface. [ABSTRACT FROM AUTHOR]

The M17-F aptamer sequences can significantly improve the affinity of cubic Ag 2 O nanoparticles to the substrate 2,4-dichlorophenol and then enhance their laccase-mimic activity, which facilitate to establish a novel and stable smartphone-integrated colorimetric biosensor for the monitoring of malathion residue in food. [Display omitted] • Enhancement effect of aptamer on laccase mimetics was first studied. • Aptamer accelerates the generation of semiquinone radicals in laccase-like system. • Smartphone-integrated biosensor enables the result to be recognized by naked eye. • The colorimetric biosensor is rapid, stable, cost-effective and selective. Malathion causes a serious threat to human health due to its widespread use in the environment. Herein, a novel and stable smartphone-integrated colorimetric biosensor for malathion detection is firstly established based on aptamer-enhanced laccase-mimicking activity. The results indicate that the M17-F aptamer can increase the affinity of Ag 2 O nanoparticles to the substrate 2,4-dichlorophenol and enhance their laccase-mimicking activity. Thus, abundant semiquinone radicals are produced in the catalytic system, which are combined with chromogenic agent to generate dark red products. The corresponding RGB values for the colour change of the solution can be easily obtained using smartphones, which is used for the rapid detection of malathion. The established biosensor for malathion has a limit of detection as low as 5.85 nmol·L−1, and displays good selectivity for other competitive pesticides. Moreover, further studies have verified the applicability of the biosensor in actual samples, indicating that it may have the potential for application in malathion detection in food. [ABSTRACT FROM AUTHOR]

The interlamellar spacings of pearlitic steels gradually increase as the isothermal transformation temperatures, correspondingly, the tensile strengths decrease, satisfying the Hall-Petch relationship. Si virtually completes its partitioning process during the eutectoid transformation. A depletion of Mn and an accumulation of Si are found in the concentration profiles of 0.95%-Si steel transformed at 793 K in the ferrite, but not in 0.22%-Si steel. It may attribute them to the Si-Mn diffusional flux couplings, which due to the strong interaction between Si and Mn atoms in the α-Fe. Transformation temperature increases to 873 K, a large amount of Mn atoms coming from ferrite cannot timely diffusion to cementite lamella core, forming a localised retention of Mn in the cementite phase side nearby the interface. This is part of a thematic issue on Pearlitic Steel Wires. [ABSTRACT FROM AUTHOR]

A larger overpotential being needed to drive overall water splitting, the poor stability of electrode materials and high cost caused by the scarcity of noble metal electrocatalysts are still important factors for restricting electrochemical water splitting. Developing high-activity, low-cost electrocatalysts to enhance hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a major challenge for overall water splitting. For this purpose, the S–Ni(Fe)OOH electrocatalyst was synthesized and used to perform HER and OER in 1.0 M KOH solution. The experimental results show that the overpotential of S–Ni(Fe)OOH is 22 mV and 198 mV, and the Tafel slope is 93.21 mV dec−1 and 17.50 mV dec−1 for HER and OER respectively. Electrochemical impedance spectroscopy (EIS) also shows that S–Ni(Fe)OOH has smaller R ct value of 2.71 Ω (HER) and 5.492 Ω (OER). The electrochemical active surface areas (ECSA) of S–Ni(Fe)OOH are 55.75 cm2 (HER) and 85.75 cm2 (OER), respectively. In addition, cyclic stability and chronoamperometry (i-t) tests prove that S–Ni(Fe)OOH catalyst has good stability with retention rates of 73.83% and 73.73% for HER and OER, respectively. In conclusion, the optimal S–Ni(Fe)OOH electrocatalyst exhibits a superior HER and OER activity, and can be used as a bifunctional electrocatalyst for the overall water splitting. [Display omitted] • S–Ni(Fe)OOH shows the ultra-low overpotential of 22 mV and 198 mV for HER and OER, respectively. • The cell voltage maintains ∼94.30% of the initial performance after the durability test. • The cell in two-electrode system shows a high energy efficiency in overall water splitting. [ABSTRACT FROM AUTHOR]

The effects of Si and Mn interactions on the spheroidization and coarsening behavior of cementite during annealing in severe cold-drawn pearlitic steel were studied. Spheroidization of cementite particles annealed at 873 K (600 °C) in heavily cold-drawn pearlitic steel was obviously retarded by higher Si contents. The coarsening kinetics of cementite particles in heavily cold-drawn and annealed pearlite obeyed a power-law relationship. The values of ECD increase steadily according to a temporal dependence of n (0.21 ± 0.02) for S87B and n (0.23 ± 0.06) for S87BM. The n values lie between 0.20 and 0.25, indicating that cementite particles coarsening occurs through a combination of dislocation diffusion ( n = 0.20) controlled and grain boundary diffusion ( n = 0.25) controlled coarsening mechanisms. Higher Si content in S87BM led to more pronounced partitioning of Mn than that in S87B, resulting in more significant suppression of alloying elements and lower coarsening rate constant K on the cementite particles coarsening behavior. [ABSTRACT FROM AUTHOR]

Heterogeneous interface engineering is an ideal method for designing low-cost and efficient electrocatalysts for oxygen evolution reaction (OER). NiCo-layered double hydroxide (LDH)/Co 9 S 8 with heterogeneous structure was prepared by a two-step hydrothermal method and employed for OER. The layered structure with a spherical base exhibited the lower overpotential (151 mV) and Tafel slope (100 mV dec−1) at a current density of 10 mA cm−2, which surpass commercially available IrO 2 and most reported non-precious metal electrocatalysts. The synergistic effect at the interface can increase the conductivity of the material, induce electron migration between NiCo-LDH and Co 9 S 8 , and decrease the energy barrier of the OER intermediate, thereby increasing the electrocatalytic activity. At the same time, heterostructures with rough surfaces and ultra-hydrophilic properties can provide the desired stability, promote ion penetration and the release of bubbles, improve the accessibility of the active site, and thus enhance the catalytic performance of OER. This work provides a feasible way to develop high performance OER electrocatalysts. [Display omitted] • Heterostructures composed of NiCo-LDH and Co 9 S 8 were constructed. • The heterointerface can lead to abundant exposed active sites and efficient interfacial charge transfer. • Heterostructures and hydrophilic properties can improve the accessibility of the active site. [ABSTRACT FROM AUTHOR]