Double peaks on ac magnetization in a superconducting Pb-porous glass nanocomposite

Studies of temperature dependences of ac magnetization were carried out for a superconducting lead-porous glass nanocomposite. Double peaks were found on the imaginary part of ac magnetization which were accompanied with double steps on the real part. The lower-temperature anomalies in ac magnetization differed noticeably when they were obtained upon cooling and warming. The double peaks were treated as two phase transitions in the vortex system: the liquid-solid transition which occurs close to the onset of superconductivity and solid-solid one which is triggered by superconductivity in confined lead islands.     

An efficient approach to derive hydroxyl groups on the surface of barium titanate nanoparticles to improve its chemical modification ability

Highly hydroxylated barium titanate (BaTiO(3)) nanoparticles have been prepared via an easy and gentle approach which oxidizes BaTiO(3) nanoparticles using an aqueous solution of hydrogen peroxide (H(2)O(2)). The hydroxylated BaTiO(3) surface reacts with sodium oleate (SOA) to form oleophilic layers that greatly enhance the dispersion of BaTiO(3) nanoparticles in organic solvents such as tetrahydrofuran, toluene, and n-octane. The results of Fourier transform infrared spectroscopy confirmed that the major functional groups on the surface of H(2)O(2)-treated BaTiO(3) nanoparticles are hydroxyl groups which are chemically active, favoring chemical bonding with SOA. The results of transmission electron microscopy of SOA-modified BaTiO(3) nanoparticles suggested that the oleate molecules were bonded to the surfaces of nanoparticles and formed a homogeneous layer having a thickness of about 2 nm. Furthermore, the improved dispersion capability of the modified BaTiO(3) nanoparticles in organic solvents was verified through analytic results of its settling and rheological behaviors.     

Electrochemical Determination of Cu(II) Ions in Chloride‐Rich Environment Using Polyviologen‐Modified Glassy Carbon Electrodes

Polyviologen was formed on glassy carbon electrodes using potentiostatic electropolymerization in pH 4.2 Britton‐Robinson buffer solution. The polyviologen‐modified glassy carbon electrode (PVGCE) was employed to determine Cu(II) in chloride‐rich solutions in order to demonstrate the electroanalytical application of polyviologen. The PVGCE was found capable of enhancing the detection limit of Cu(II) in chloride‐rich environment because of the anion‐exchange feature of the polymer film. Cathodic stripping square‐wave voltammetry (CSSWV) was employed to determine Cu(II). The dependence of the cathodic stripping current on the concentration of Cu(II) was linear from 0.06 ppm to 9.53 ppm with a regression coefficient of 0.999. The detection limit is 0.02 ppm (σ = 3). Regeneration of the PVGCE can be achieved by simply immersing the electrode in a stirred 0.5 M NaCl solution.     

The first three anisotropy constants of nickel

The technique of ferromagnetic resonance at 23 GHz has been used to determine the first three anisotropy constants of pure Ni down to 4.2K. A temperature and orientation dependent linewidth has also been observed.