Effect of synthesis conditions on preparation of nickel metal nanopowders via hydrothermal reduction technique

Electrocatalytic Properties of Co Nanoconical Structured Electrodes Produced by a One-Step or Two-Step Method

One-dimensional (1D) nanostructures, such as nanotubes, nanopores, nanodots and nanocones, are characterized by better catalytic properties than bulk material due to their large active surface area and small geometrical size. These structures can be produced by several methods of synthesis including the one- and two-step methods. In the one-step method, a crystal modifier is added to the solution in order to limit the horizontal direction of structures growing during electrodeposition. In this work, NH4Cl was used as a crystal modifier. Another way of production of 1D nanocones is the electrodeposition of metal in porous anodic alumina oxide (AAO) templates, called the two-step method. In this case, the AAO template was obtained using a two-step anodization process. Nanocones obtained by the two-step method show smaller geometrical size. In this work, cobalt nanoconical structures were obtained from an electrolyte containing CoCl2 and H3BO3. The electrocatalytic properties of materials fabricated by one-step and two-step methods were measured in 1 M NaOH and compared with bulk material electrodeposited from the same electrolyte. There were several microshell structures in the case of Co deposits obtained by the one-step method. To solve this problem, different conditions of synthesis Co cones by the one-step method were applied. The electrocatalytic activity of these samples was checked as well.

Hydrazine assisted catalytic hydrogenation of PNP to PAP by NixPd100−x nanocatalyst

NiPd nanocatalyst assisted catalytic hydrogenation of PNP to PAP by hydrazine.

Controllable preparation of Ni nanoparticles for catalysis of coiled carbon fibers growth

The mass preparation of high-purity coiled carbon fibers (CCFs) remains challenging due to the high complexity and low controllability of reaction. In this work, a controllable growth of Ni particles was fulfilled by liquid phase reduction of nickel sulfate with hydrazine hydrate. The impacts of the reaction temperature, NaOH concentration, and reaction time on the particle size and purity were investigated. The as-deposited Ni particles were characterized by scanning electron microscopy and X-ray diffraction. In addition, these Ni particles were also applied in preparing high-purity CCFs both on graphite and ceramic substrates. The diameter of the as-grown carbon microcoil was about 500 nm, and the related growth mechanism was discussed.

GROWTH OF NICKEL NANOSTRUCTURED BEADS AND THIN FILMS

Ferromagnetic nickel metal beads, fibers, and thin films have been successfully grown from salt solution by a stepwise hydrazine reduction route with and without surfactants. XRD analyses showed that nickel was grown in the metallic phase and no other phases such as nickel oxide were detected in the prepared samples. SEM investigations showed that bead-like structures that agglomerated in the form of cloth- or net-like structures of about 1 μm size that composed of needle-like nanoparticles have been synthesized without using a surfactant. Sharp decrease in size was observed when sodium dodecyl benzene sulphonate (SDBS) and/or polyethylene glycol (PEG) were used. Bead-like morphology of nickel nanostructures of < 150 nm were deposited in this case. Free-standing nickel thin film structures that composed of needle-like nanoparticles of about 50 nm size were deposited by a stepwise reduction. Nickel nanostructures of < 100 nm showed higher coercivity (Hc) value of 184.6,Oe and lower saturation magnetization (Ms) value of 13.29 emu/g. This might be due to the anisotropic shape and size effects. It is strongly believed that nickel nanoparticles are self-assembled through a dipolar–dipolar interaction due to the magnetic property.

Effect of organic modifiers on the structure of nickel nanoparticles and catalytic activity in the hydrogenation of p-nitrophenol to p-aminophenol

Spherical nickel nanoparticles with different sizes and different structures were prepared starting from nickel oxalate and using hydrazine hydrate as a reductant in the presence of citric acid, cetyltrimethylammonium bromide, Tween 40, and d-sorbitol as organic modifiers. The size and structure of the resultant nickel nanoparticles were affected by using different organic modifiers. All of the nickel nanoparticles showed higher catalytic activity and selectivity than the conventional raney Ni catalyst in the hydrogenation of p-nitrophenol to p-aminophenol. Although the catalytic activities of the resultant nickel nanoparticles generally increased with decreasing particle size, the structure of nickel nanoparticles also had an important impact on the catalytic activity.