Bao Jianchun

Chemical composition and magnetism of Ag doped LaMnO3

By using a sol-gel clue, a set of polycrystalline perovskite samples La1−xAgxMnO3 with a nominal doping level x ranging from 0.05 to 0.45 has been synthesized. The chemical composition and the magnetism of the samples were investigated. A little Ag was found seeping from the samples in the sintering process when the doping level exceeded 0.05 and the sintering temperature was higher than 700°C resulting in the samples being in multiphase. The magnetic transition points of the samples have been found to decrease with increasing sintering temperature. A concentration-dependent Tc similar to that of bivalent metal ion doped perovskite, has been obtained. We believe that the Ag seeping in the sintering process is responsible for those magnetic characteristics.

Synthesis of spherical porous Pd nanoparticle superstructure and its catalytic oxidation of formic acid

Spherical porous Pd nanoparticle superstructures with the diameter in the range of 30-50 nm were obtained by the reaction of PdCl42- with hydrazine using hexadecylpyridinium chloride as a structure-directing agent in the mixed acetone/water solution. It was found that hexadecylpyridinium chloride had significant influence on the formation of the spherical porous Pd nanoparticle superstructure. Only solid spherical structure was formed in the absence of the surfactant. In addition, acetone had an effect on the size of the micelles modified. The electrocatalytic activity of the spherical porous Pd nanoparticle superstructure electrode for the formic acid oxidation in 0.5 mol/L H2SO4+0.5 mol/L HCOOH was also investigated. The results displayed that electrocatalytic activity and stability of the spherical porous Pd nanoparticle superstructure catalyst were better than that of the solid Pd catalyst.

Intergranular Tunnelling and Field-Induced Percolation Fluctuation of Granular Composites (La1−zAgzMnO3)/(MnO2/Mn2O3)

We investigate the giant magnetoresistance of composites (La1−zAgzMnO3)1−y(MnO2/Mn2O3)y. The magnetoresistive property of the composites shows the characteristics of intergranular tunnelling. A conductivity leap has been observed around y = 0.7. The composite (La0.926Ag0.074MnO3)0.698(MnO2/Mn2O3)0.302 has been found to show the greatest magnetoresistance in the samples. Its room-temperature MR ratio reaches 24% under a field of 1.8 T. These phenomena suggest a percolation transformation and a kind of field-induced fluctuation in percolation in the samples investigated.