Wettability effect of graphene-based surfaces on silicon carbide and their influence on hydrophobicity of nanocrystalline cerium oxide films.

We investigate the water-repellent ability of graphene-based surfaces stabilized on silicon carbide (SiC) and the nanocrystalline cerium oxide (CeO2) films electrodeposited on them. Water contact angle is revealed strongly dependent on the number of graphene monolayers on SiC, indicating partial permeability of graphene on SiC. Fluctuations in the roughness of textured surfaces as well as variations of oxygen vacancy content in CeO2 electrodeposits are determinant for the hydrophobicity of the interaction between water droplets and nanocrystalline CeO2 electrodeposits on monolayers graphene on SiC.

Nickel nanoparticles obtained by a modified polyol process: synthesis, characterization, and magnetic properties.

The synthesis of nickel nanoparticles using poly(N-vinilpyrrolidone) (PVP) as protective agent was studied. The nanoparticles were prepared in air according to a modified polyol route, using nickel chloride as precursor and sodium borohydride as reducing agent. Samples with different nickel/PVP ratio were obtained. The X-ray diffraction and transmission electron microscopy (TEM) measurements indicate the occurrence of face-centered cubic metallic nickel nanoparticles with a medium diameter of 3.8 nm and good size dispersion. Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) data show an effective interaction between the nickel nanoparticles surface and the carboxyl oxygen atoms of PVP. Magnetic measurements show single-domain nonideal superparamagnetism behavior due to dipolar magnetic coupling between particles.

Structural and magnetic properties of Fe and Co nanoparticles embedded in powdered Al2O3.

The structural and magnetic properties of powdered composites consisting of nanosized Fe and Co particles embedded in alumina grains have been investigated. The composites were synthesized by a novel and simple method using co-precipitation from a hybrid gel solution containing layered double hydroxide and aluminium hydroxide. After a vacuum annealing procedure, the Fe composites have a negligible number of Fe(+3) ions and a high concentration of crystalline alpha-Fe nanoparticles having truncated polyhedron shapes with an average diameter of 20 nm that are physically well separated from each other. Magnetization measurements as a function of temperature revealed a superparamagnetic-like behavior characteristic of an assembly of fine particles. A spurious ferromagnetism related to surface interaction between magnetic particles from different powder grains and the formation mechanism of the composites are also discussed.