Enhanced Mechanical and Tribological Capabilities of a Silicon Aluminum Alloy with an Electroplated Ni–Co–P/Si3N4 Composite Coating

Ni–Co–P/Si3N4 composite coatings were fabricated over an aluminum–silicon (Al–Si) substrate using a pulse-current electroplating process, in which the rapid deposition of an intermediate nickel–cobalt layer was used to improve coating adhesion. The microstructure, mechanical, and tribological behaviors of the electroplated Ni–Co–P/Si3N4 composite coating were characterized and evaluated. The results revealed that the electroplated Ni–Co–P/Si3N4 composite coating primarily consisted of highly crystalline Ni–Co sosoloid and P, and a volumetric concentration of 7.65% Si3N4. The electroplated Ni–Co–P/Si3N4 composite coating exhibited hardness values almost two times higher than the uncoated Al–Si substrate, which was comparable to hard chrome coatings. Under lubricated and dry sliding conditions, the electroplated Ni–Co–P/Si3N4 composite coating showed excellent anti-wear performance. Whether dry or lubricated with PAO and engine oil, the composite coating showed minimum abrasive wear compared to the severe adhesive wear and abrasive wear observed in the Al–Si substrate.

In Situ Reduced Multi-Core Yolk–Shell Co@C Nanospheres for Broadband Microwave Absorption

The preparation of yolk–shell microwave absorption materials with low density and excellent microwave absorption property requires reasonable design and economical manufacture. In this study, an efficient strategy without any templates or reducing gases has been designed to fabricate multi-core yolk–shell Co@C nanospheres by high temperature carbonization. The results showed that Co3O4 was completely reduced by the carbon shell to metal cobalt at temperatures above 750 °C. This unique multi-core yolk–shell structure with shell of 600 nm and multiple cores of tens of nanometers can provide sufficient interface and space to reflect and scatter electromagnetic waves. At the same time, the metal cobalt layer and carbon layer provide magnetic loss ability and dielectric loss ability, respectively, making the composite show good wave absorption performance. The minimal RL value of samples carbonized at 750 °C reaches −40 dB and the efficient absorption band reaches 9 GHz with the thickness ranges from 2–9 mm. Therefore, this is a facile, effective and economical strategy to prepare yolk–shell structure, which provides a new idea for the preparation of microwave absorption materials.

Электронная структура графена на карбиде кремния, интеркалированного атомами кремния и кобальта

The results of ab initio calculations of the spin-polarized band structure of graphene on silicon carbide intercalated with cobalt and silicon atoms are presented. It is shown that metal and silicon atoms during intercalation are localized between the substrate and the buffer layer of carbon atoms. Initially, the cobalt layer is strongly coupled with the buffer layer. The subsequent intercalation of silicon and the formation of cobalt silicide leads to a transition from hybridized state to the formation of quasi-freestanding bilayer graphene on the surface of the system due to the transformation of the buffer layer to the second graphene layer.

Магнитоиндуцированный нелинейно-оптический отклик плeнок на основе нанослоeв тяжeлых и ферромагнитного металлов

We present the results of the experimental studies of magnetization-induced effects in optical second harmonic generation (SHG) from three-layer W/Co/Pt films with different thicknesses of the cobalt layer (2-10 nm) influenced by longitudinal dc magnetic field. The intensity effect in the p-polarized second harmonic that is odd in magnetization was observed, which reveals an increase in the corresponding magnetic contrast of the SHG intensity with an increase of the cobalt layer thickness from 2 nm to 10 nm. A phenomenological description of the observed effects was carried out when considering the bulk nonlinear polarization at the SHG frequency, which is proportional to the magnetization gradient in the direction normal to the structure, as well as the interface contribution, which is proportional to the square of the magnetization of the films.

Magnetic Properties and Spin-Wave Excitations in Co/Mn Multilayers

Co/Mn multilayers were prepared using evaporation technique under ultra-high vacuum conditions and their structural and magnetic properties were studied. The temperature dependence of the spontaneous magnetization [Formula: see text] was recorded for different cobalt layer thickness ([Formula: see text]) ranging from 19[Formula: see text]Å to 70[Formula: see text]Å. Bloch’s law describes satisfactory the thermal change of magnetization for all samples. In addition, the change of the spin-wave (SW) parameter [Formula: see text] versus [Formula: see text] was discussed. The torque magnetometry was utilized to extract the effective anisotropy ([Formula: see text]) and the interlayer coupling constant ([Formula: see text]) was determined from the in-plan M–H loops. An updated model based on SW theory was applied to describe the [Formula: see text] variation and to calculate the approximate values of exchange interactions for samples with different Co-layer thicknesses.

Strength Determination Based on the Results of Modeling the Crack Propagation in a Nanostructured Hard Alloy

The process of crack propagation from the initial pore in the microstructures of WC-Co alloys with different volume fraction of the cobalt phase was studied by simulation of the stressed state by the finite element method. A calculation of the energy release rate during the propagation of crack through sections which consist of the carbide grains and the cobalt phase was made. It is shown that the strain energy release rate increases with crack propagation in WC grains and decreases with crack propagation in the intermediate layers of cobalt. The maximum stresses required for the destruction of the cobalt layer determine the strength of the entire microstructure. The strength of the alloy increases when decreasing pore diameter and increasing the cobalt phase fraction.

Water Electrolysis Anode Based on 430 Stainless Steel Coated with Cobalt Recycled from Li-Ion Batteries

In this paper, a new environmentally-friendly anode for hydrogen production was developed based on 430 stainless steel with an electrodeposited cobalt layer. The novelty of this work is the cobalt source once the electrodeposition bath was obtained from acid dissolution of a spent Li-ion battery cathode. The oxygen evolution reaction on electrodeposited cobalt in 1 M KOH is compatible with the E. Kobussen mechanism. The water discharge is related with reaction determinant step in low overpotential. The cobalt electrodeposition (3 Ccm−2) promotes a significant improvement of 430 stainless steel anodic properties for oxygen evolution reaction. When the overpotential reaches 370 mV, the density current for 430 stainless steel with electrodeposit cobalt is 19 mA·cm−2 against 0.80 mA·cm−2 for 430 stainless steel without cobalt. Thus, the anode construction described in this paper is an excellent option for Li-ion battery recycling.

The New Anode Environmentally Friendly for Water Electrolysis Based on 430 Stainless Steel Coated with Recycled Cobalt from Spent Lithium–Ion Batteries

In this paper, a new anode environmentally friendly for hydrogen production was developed based on 430 stainless steel with an electrodeposited cobalt layer. The novelty of this work is the cobalt source once the electrodeposition bath was obtained from recycling of spent Li-ion batteries cathode with composition LiCoO2. The electrodeposited cobalt behaves as supercapacitor in KOH 1M. In the linear voltammetry in KOH 1M, when the overpotential reaches 370 mV, the anodic density current for 430 SS/Co is 19 mA cm−2. Thus, the anode developed in this paper achieves the double of density current with half of production cost if compared with 316SS. Moreover the anode construction described in this paper is an excellent option for Li- ion battery recycling.