Electrodeposition of Cu–Ni Composite Coatings

The electrodeposition of Cu–Ni incorporated with nano- to microparticles to produce metal matrix composites has been reviewed in this chapter. The inclusion of particles into the metal matrix produced enhanced properties in the areas of electronics, mechanics, electrochemistry, and corrosion. In electronics, an increase in the magnetic properties and durability for microactuators was observed. Measurements of the mechanical properties showed an increase in hardness, wear resistance, shear adhesion, and tensile strength for the material. The corrosion resistance of the metal matrix coatings was improved over that of pure Cu–Ni. As the accessibility of nanoparticles continues to increase, the interest in reduced cost and low-temperature electrodeposited metal matrix composites continues to rise. However, only a small number of articles have investigated Cu–Ni composite coatings; these composite coatings need further examination due to their advantageous properties

Influence of Bath Composition at Acidic pH on Electrodeposition of Nickel-Layered Silicate Nanocomposites for Corrosion Protection

Nickel-layered silicates were electrochemically deposited from acidic bath solutions. Citrate was used as a ligand to stabilize nickel (II) ions in the plating solution. The silicate, montmorillonite, was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta-potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The solution particles at pH 2.5 (−22.2 mV) and pH 3.0 (−21.9 mV) were more stable than at pH 1.6 (−10.1 mV) as shown by zeta-potential analysis of the nickel-citrate-montmorillonite plating solution. Ecorr for the films ranged from −0.32 to −0.39 V with varying pH from 1.6 to 3.0. The films were immersed in 3.5% NaCl and the open circuit potential monitored for one month. The coatings deposited at pH 3.0 were stable 13 days longer in the salt solution than the other coatings. X-ray diffraction showed a change in the (111)/(200) ratio for the coatings at the various pHs. The scanning electron microscopy and hardness results also support that the electrodeposition of nickel-montmorillonite at pH 3.0 (234 GPa) had improved hardness and morphology compared to pH 2.5 (174 GPa) and pH 1.6 (147 GPa)

Projections of climate conditions that increase coral disease susceptibility and pathogen abundance and virulence

Rising sea temperatures are likely to increase the frequency of disease outbreaks affecting reef-building corals through impacts on coral hosts and pathogens. We present and compare climate model projections of temperature conditions that will increase coral susceptibility to disease, pathogen abundance and pathogen virulence. Both moderate (RCP 4.5) and fossil fuel aggressive (RCP 8.5) emissions scenarios are examined. We also compare projections for the onset of disease-conducive conditions and severe annual coral bleaching, and produce a disease risk summary that combines climate stress with stress caused by local human activities. There is great spatial variation in the projections, both among and within the major ocean basins, in conditions favouring disease development. Our results indicate that disease is as likely to cause coral mortality as bleaching in the coming decades. These projections identify priority locations to reduce stress caused by local human activities and test management interventions to reduce disease impacts

Synthesis of Nickel and Nickel Hydroxide Nanopowders by Simplified Chemical Reduction

Nickel nanopowders were synthesized by a chemical reduction of nickel ions with hydrazine hydrate at pH ~12.5. Sonication of the solutions created a temperature of 54–65°C to activate the reduction reaction of nickel nanoparticles. The solution pH affected the composition of the resulting nanoparticles. Nickel hydroxide nanoparticles were formed from an alkaline solution (pH~10) of nickel-hydrazine complexed by dropwise titration. X-ray diffraction of the powder and the analysis of the resulting Williamson-Hall plots revealed that the particle size of the powders ranged from 12 to 14 nm. Addition of polyvinylpyrrolidone into the synthesis decreased the nickel nanoparticle size to approximately 7 nm. Dynamic light scattering and scanning electron microscopy confirmed that the particles were in the nanometer range. The structure of the synthesized nickel and nickel hydroxide nanoparticles was identified by X-ray diffraction and Fourier transform infrared spectroscopy

Electrodeposition of 70-30 Cu-Ni nanocomposite coatings for enhanced mechanical and corrosion properties

A copper-nickel alloy (70:30 ratio) was electrochemically deposited and compared to a composite coating incorporating layered silicate platelets to obtain copper-nickel-montmorillonite (MMT). The composite coatings were electrochemically deposited from a citrate bath to investigate the effects of MMT on the corrosion and mechanical properties of the coatings. Incorporation of MMT into the Cu–Ni alloy films was not affected by the deposition parameters such as applied voltage and pH. Scanning electron microscopy and atomic absorption spectroscopy confirmed the successful incorporation of the MMT into the coatings. Longer term stability in the presence of corroding solutions was noted for the copper-nickel composite films. The Tafel calculations showed an increase in polarization resistance, Rp, from 190.7 kΩ·cm2 for pure Cu–Ni to 314.3 kΩ·cm2 for Cu–Ni-0.2% MMT after soaking the coatings in 3.5% NaCl at 25 °C for two weeks, which was consistent with the resistance increase measured by electrochemical impedance spectroscopy. Microhardness test results showed about a 25% increase in the hardness for the copper-nickel coatings incorporated with the layered silicate platelets versus the pure Cu–Ni coating.This work was made possible by NPRP Grant 4-306-2-111 from the Qatar National Research Fund (a Member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors. The authors acknowledge the Center for Advanced Research and Technology (CART) at the University of North Texas.Scopu

Tuning Interfacial Electron Transfer in Nanostructured Cuprous Oxide Photoelectrochemical Cells with Charge-Selective Molecular Coatings

The coating of nanostructured films of cuprous oxide with electroactive molecules strongly affects their photoelectrochemical performance in nonaqueous photocells, with photocurrent density increased up to an order of magnitude relative to bare cuprous oxide films or almost completely suppressed, depending on the choice of molecular adsorbant. Among adsorbants that enhance photocurrent, a strong variance of photoelectrochemical behavior is observed with changes in the molecular structure of the sensitizer, associated with differences in the reorganization energy and molecular size, which are interpreted to enhance forward electron transport and impede electrolyte/photocathode recombination, respectively. These results demonstrate that nanostructured cuprous oxide is a promising cathode material for p-type dye-sensitized solar cells