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In this study, different Cobalt–Copper mixed oxides compositions for supercapacitor electrodes have been prepared, by means of electrodeposition and thermal annealing. The chemical–physical and electrochemical characterization of electrodes, as well as the effect of different Co/Cu in the ratios on the crystal lattice, electrode morphologies, and electrochemical performance of the electrodes, were investigated using X-ray diffraction (XRD), scanning electron microscopic (SEM) and cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) tests. The results indicated that the electrode prepared from 0.06 M CoSO4·7H2O + 0.04 M CuSO4·5H2O solution (CC4) had a better electrochemical performance. The initial capacity of the CC4 electrode was 28.3 mAh/g at a scan rate of 5 mV/s with a coulombic efficiency of 94%. CC4 electrode featured capacity retention of 79.2% at a constant current density of 1 A/g after 5000 cycles.

A novel method is established that improves the shortcoming of embedding low volume fraction of reinforcements in Ni–P electroless coating. Experimental design of the present study is based on 5 steps: (1) electrophoretic deposition (EPD) of titanium carbide core inside the Ni–P shell particles (2) pre-sintering of as-EPD layer (3) electroless deposition of Ni–P top layer on as-EPD layer (4) heating the multilayer structure and (5) infiltration of the Ni–P melt phase through porous EPD layer. Anchoring TiC particles inside a Ni–P shell was done for catalyzing electroless Ni–P deposition on as-EPD layer and improving the high-temperature wettability of the EPD layer. By infiltration sintering on EPD layer (20 V for 2 min) a composite coating of Ni–P/TiC with a volume fraction of ~49% TiC was successfully produced. According to wear test results, embedding TiC into Ni–P significantly increases hardness (972–1460 VHN) and reduces friction coefficient (0.45–0.23).

ABSTRACTA novel method is established that improves the shortcoming of embedding low volume fraction of reinforcements in Ni–P electroless coating. Experimental design of the present study is based on 5 steps: (1) electrophoretic deposition (EPD) of titanium carbide core inside the Ni–P shell particles (2) pre-sintering of as-EPD layer (3) electroless deposition of Ni–P top layer on as-EPD layer (4) heating the multilayer structure and (5) infiltration of the Ni–P melt phase through porous EPD layer. Anchoring TiC particles inside a Ni–P shell was done for catalyzing electroless Ni–P deposition on as-EPD layer and improving the high-temperature wettability of the EPD layer. By infiltration sintering on EPD layer (20 V for 2 min) a composite coating of Ni–P/TiC with a volume fraction of ∼49% TiC was successfully produced. According to wear test results, embedding TiC into Ni–P significantly increases hardness (972–1460 VHN) and reduces friction coefficient (0.45–0.23).

• High performance binder free single crystalline tin nano-platelets electrodes was prepared by surfactant-assisted electrodeposition. • Preferential adsorption of triton X100 on {022} planes promotes anisotropic growth of tin along [100] direction that results in formation of 2-D tin platelets. • Two-dimensional platelets electrode delivers high specific capacity of 820 mA h g−1 for 100 cycles and more. • Nanostructures architecture of tin facilitates high rate capability up to 5 C with ability to be operated up to 20 C. A template free, single-step process is developed for fabrication two-dimensional tin nano-platelets by electrochemical deposition in the presence of Triton X100 (TX100). Electrochemical studies combined with structural characterization revealed that during electrodeposition, TX100 molecules adsorb preferentially on {022} planes of Sn and highly anisotropic growth promotes in [200] direction which results in the formation of platelet morphology. The deposited platelets exhibit a high aspect ratio of 30 (width to thickness) and thickness of 25 ± 5 nm that uniformly covered the substrate with a high platelet density of 9 × 108 cm−2. The electrochemical performance of nano-platelets for lithium storage was studied in detail and compared with other morphologies of tin. Tin nano-platelets exhibited high reversible capacity and excellent cycling performance, the capacity was maintained at 820 mA h g−1 for 100 cycles and more, far superior to the other structures. Excellent rate capability was also observed for nano-platelets up to 5 C, with the ability to be operated at 20 C without damage. The superior electrochemical performance of tin platelets is mainly attributed to its two-dimensional structure that efficiently distributes strain, allowing high mechanical stability even after 100 cycles, as confirmed by Scanning Electron Microscopy (SEM). [ABSTRACT FROM AUTHOR]

Different thicknesses of Ni films were deposited on Si substrates and heat treated at 973 and 1073 K. The results showed that Ni nanoparticles with different diameters and shapes were formed from different thicknesses. To find the mechanisms of the Ni nanoparticle formation from Ni nanofilms, our previous model on the heterogeneous transformation of Ni nanofilms to nanoparticles and geometrical and kinetic calculations were used and compared with the experimental results. It was found that the mechanism for formation of particles is a stepwise melting of layers of specific thickness, dependent upon the working temperature, e.g., 0.5 nm thick layers at 1073 K. Nanofilms transform to nanoparticles which do not exceed 150 nm in diameter and 40° in wetting angle. Films with a thickness of more than 12.9 nm show a different behavior. The predictions are in excellent agreement with the experimental results.

Size dependent thermodynamic parameters (Gibbs free energy, entropy, enthalpy, and surface energy) have been calculated for the heterogeneous transition of Ni nanofilms to nanoparticles. Such particles are often used as catalysts for carbon nanotube formation, and particle size controls the carbon nanotube diameter. The resultant equations are based upon the size dependent melting temperature of nanosolids derived in our previous works, and the results are compared with our recent calculations on the homogeneous formation of Ni catalyst particles. Using this thermodynamic approach, a relation between the minimum diameter of Ni particles and the thickness of the original film is found, and we predict the optimum Ni film thickness to form particles with diameter 20−30 nm. We illustrate that the calculated critical and stable sizes of Ni heterogeneously formed nanoparticles are a function of the wetting angle. For further comparison, a 5 nm Ni film was deposited on a Si substrate and heat treated at 923 K. Atomic force microscopy showed that Ni nanoparticles with spherical cap diameters of 20−200 nm were formed, and their wetting angles were used to confirm the derived equations. The predictions are in good agreement with the experimental results.

The dependency of the surface-to-volume coordination number upon particle size has been obtained by an analytical function based upon our previous work, and a model for melting temperature as a function of size is presented. This expression for the melting temperature is a nonlinear relation in terms of the reciprocal of size. Also, the geometrical characteristics of nanoclusters have been applied to our general equation for the melting temperature of nanoparticles. It was found that the results of considering the geometrical characteristics of nanoclusters are in good agreement with the melting temperature achieved by the derived analytical function. Finally, this model has been compared with other theoretical models as well as the available experimental data. The predictions are consistent with the experimental data.