Characterization of Carbon Nanomaterials Dispersions: Can Metal Decoration of MWCNTs Improve Their Physicochemical Properties?

A suitable dispersion of carbon materials (e.g., carbon nanotubes (CNTs)) in an appropriate dispersant media, is a prerequisite for many technological applications (e.g., additive purposes, functionalization, mechanical reinforced materials for electrolytes and electrodes for energy storage applications, etc.). Deep eutectic solvents (DES) have been considered as a promising “green” alternative, providing a versatile replacement to volatile organic solvents due to their unique physical-chemical properties, being recognized as low-volatility fluids with great dispersant ability. The present work aims to contribute to appraise the effect of the presence of MWCNTs and Ag-functionalized MWCNTs on the physicochemical properties (viscosity, density, conductivity, surface tension and refractive index) of glyceline (choline chloride and glycerol, 1:2), a Type III DES. To benefit from possible synergetic effects, AgMWCNTs were prepared through pulse reverse electrodeposition of Ag nanoparticles into MWCNTs. Pristine MWCNTs were used as reference material and water as reference dispersant media for comparison purposes. The effect of temperature (20 to 60 °C) and concentration on the physicochemical properties of the carbon dispersions (0.2–1.0 mg cm−3) were assessed. In all assessed physicochemical properties, AgMWCNTs outperformed pristine MWCNTs dispersions. A paradoxical effect was found in the viscosity trend in glyceline media, in which a marked decrease in the viscosity was found for the MWCNTs and AgMWCNTs materials at lower temperatures. All physicochemical parameters were statistically analyzed using a two-way analysis of variance (ANOVA), at a 5% level of significance.

Electrocatalytic Properties of Pulse-Reverse Electrodeposited Nickel Phosphide for Hydrogen Evolution Reaction

Nickel phosphide (Ni-P) films as a catalytic cathode for the hydrogen evolution reaction (HER) of a water splitting were fabricated by a pulse-reverse electrodeposition technique. The electrochemical behaviors for the electrodeposition of Ni-P were investigated by the characterization of peaks in a cyclic voltammogram. The composition of the electrodeposited Ni-P alloys was controlled by adjusting duty cycles of the pulse-reverse electrodeposition. The HER electrocatalytic properties of the Ni-P electrodeposits with an amorphous phase as a function of phosphorous contents existing in Ni-P were electrochemically characterized by the analysis of overpotentials, Tafel slopes, and electrochemical impedance spectrometry. Additionally, the elemental Ni-embedded crystalline Ni3P was prepared by an annealing process with the amorphous Ni69P31 electrodeposit with high contents of phosphorus. The crystalline structure with Ni inclusions in the matrix of Ni3P was formed by the precipitation of excess Ni. The electrocatalytic properties of crystalline Ni3P with elemental Ni inclusions were also investigated by electrochemical characterization.

Production of Nano-Composite Hydroxyapatite-Based Coatings through Reverse Pulse Electroplating

Since the discovery of synthetic HAp in the 1950s, hydroxyapatite is becoming a significant covering material for bio implants. A regulated surface roughness/porosity, appropriate chemical resistance, and a desirable tri-biological behavior are required for HAp coatings. On substrates with a variety of structure, composition, size, and shape, the coating process must be applied at varied scales and at a fast enough rate. There is a full description of both dry and wet coating procedures included in this article. Cathode efficiency fell as tc- increased, although it was still better than DC coatings. In this paper, the mechanism of HAp electrodeposition is examined, as well as the effect of operational variables on deposit characteristics. Recent advances in the field are critically examined. HAp composite coatings, including those reinforced with metallic, ceramic, and polymeric particles, as well as nanotubes, modified graphene’s, chitosan, and heparin, are discussed in depth. On the other hand, a glance towards the future in the field of electrodeposited HAp coatings is taken. Different experimental parameters were explored to establish the optimal reaction conditions for HA-Ag nanocomposites. Pulse reverse plating (PRP) in combination with an anionic surfactant, sodium dodecylsulphate (SDS), was utilized for the first time to generate nanocomposite Co-Al2O3 electrodeposited coatings, using a technique similar to that used for Co – IF WS2 deposition in prior work. The optimal plating setups in the pulse-reverse electroplating (PRP) mechanism for non-anomalous plating of Co–Ni deposits (i.e., the metal composition of deposits equals that of the plating solutions) from chloride solutions were determined using experimental strategies such as fractional factorial design (FFD), path of steepest ascent, and central composite design (CCD) combined with the response surfaces (RSM). The FFD research found that the potentials and time duration of pulse-plating had a significant impact on the composition of Co–Ni deposits. The two parameters were the sharpest ascending route and the best circumstances for non-anomalous plating of Co–Ni layers. NiFe thin films produced by pulse reverse (PR) electrodeposition are potential alternatives for the next phase of core magnetic materials that will be utilized in high shifting frequency magnetic elements. For statistical modeling and analysis of the nickel electroplating process outcomes, the central composite experimental design and response surface technique were used. The empirical models developed in terms of design variables (current density J (A/dm2), temperature T (C), and pH) were found to be statistically adequate to describe the process responses, namely cathode efficiency Y%, coating thickness U (m), brightness V%, and hardness W%. (HV). The response surfaces were explored and analyzed using graphical representations consisting of 2D contour plots and 3D surface plots in order to determine the main, quadratic, and interaction effects. The desirability function method was used to do multi-response optimization of the nickel electroplating process. To this aim, a genetic algorithm was employed to solve the multi-response issue mathematically. The optimization method resulted in the Pareto optimum set, which is a collection of similar solutions.

Pulsed Reverse Potential Electrodeposition of Carbon-Free Ni/NiO Nanocomposite Thin Film Electrode for Energy Storage Supercapacitor Electrodes

A combined cyclic voltammetry and pulse reverse potential electrodeposition technique has been used to synthesize carbon-free Ni/NiO nanocomposite thin film supercapacitor electrode. The structural and morphological analyses have revealed the presence of crystalline phases of both Ni and NiO in the form of nanospheres of size ~ 50 nm. The electrochemical analysis of the Ni/NiOna nocomposite electrode has shown a remarkable performance by delivering a high specific capacitance of 2000 Fg−1 at an applied current load of 1 Ag−1 and a capacitance retention of 98.6%, after over 800 cycles under a high current load of 20 Ag−1.