Ni/ZrO2 composite electrodeposition in the presence of coumarin: textural modifications and properties

The Use of ZrO2 Waste for the Electrolytic Production of Composite Ni-P-ZrO2 Powder

Ni–P–ZrO₂ composite powder was obtained from a galvanic nickel bath with ZrO₂ powder. Production was conducted under galvanostatic conditions. The Ni–P–ZrO₂ composite powder was characterized by the presence of ZrO₂ particles covered with electrolytical nanocrystalline Ni–P coating. The chemical composition (XRF method), phase structure (XRD method) and morphology (SEM) of Ni–P–ZrO₂ and the distribution of elements in the powder were all investigated. Based on the analyses, it was found that the obtained powder contained about 50 weight % Zr and 40 weight % Ni. Phase structure analysis showed that the basic crystalline component of the tested powder is a mixed oxide of zirconium and yttrium Zr_0.92Y_0.08O_1.96. In addition, the sample contains very large amounts of amorphous compounds (Ni–P). The mechanism to produce the composite powder particles is explained on the basis of Ni²⁺ ions adsorption process on the metal oxide particles. Current flow through the cell forces the movement of particles in the bath. Oxide grains with adsorbed nickel ions were transported to the cathode surface. Ni²⁺ ions were discharged. The oxide particles were covered with a Ni–P layer and the heavy composite grains of Ni–P–ZrO₂ flowed down to the bottom of the cell.

Optimization of Microalga Chlorella vulgaris Magnetic Harvesting

Harvesting of microalgae is a crucial step in microalgae-based mass production of different high value-added products. In the present work, magnetic harvesting of Chlorella vulgaris was investigated using microwave-synthesized naked magnetite (Fe₃O₄) particles with an average crystallite diameter of 20 nm. Optimization of the most important parameters of the magnetic harvesting process, namely pH, mass ratio (m_r) of magnetite particles to biomass (g/g), and agitation speed (rpm) of the C. vulgaris biomass-Fe₃O₄ particles mixture, was performed using the response surface methodology (RSM) statistical tool. Harvesting efficiencies higher than 99% were obtained for pH 3.0 and mixing speed greater or equal to 350 rpm. Recovery of magnetic particles via detachment was shown to be feasible and the recovery particles could be reused at least five times with high harvesting efficiency. Consequently, the described harvesting approach of C. vulgaris cells leads to an efficient, simple, and quick process, that does not impair the quality of the harvested biomass.

Tribological behavior of a Ni matrix hybrid nanocomposite reinforced by titanium carbide nanoparticles during electro-codeposition

TiC nanoparticles (50 nm mean diameter) were successfully electro-codeposited with nickel to obtain Ni/nano-TiC hybrid nanocomposite layers on a 304L stainless steel support with increased properties of nanohardness and wear resistance.