材料期刊网

Influence of Rare-Earth Elements on Electrical Properties of Pd

Fei WEN , Yuantao NING , Huaizhi ZHAO and Deguo DENG(Kunming Institute of Precious Metals , Kunming , 650221 , China)

材料科学技术（英文）

The influence of RE (RE = La, Ce. Pr. Nd, Sm, Eu, Gd. Tb. Dy, Er, Yb) additives with dilute concentrations on the electrical properties of Pd has been studied. All RE elements increase the specific resistivity (ρ) and decrease the resistance temperature coefficient (α) of Pd. and (ρ.α) Pd-RE ls equal to (ρ· α)Pd.The RE elements before Gd reduce the thermo-emf of Pd on Cu. other heavy RE enhance the thermo-emf.The experimental data of normalized Pd-0.1 at.-%RE alloys indicate that the effect of light RE additives on the specific resistivity of Pd is larger than that of heavy RE and Ce. Eu and Yb show anomalous strong effect. The valence and atomic size are main factors influencing the electrical properties.

关键词:

Improving the electrochemical properties of natural graphite spheres by coating with a pyrolytic carbon shell

新型炭材料

Two kinds of modified natural graphite (MNG) spheres with a pyrolytic carbon shell on smooth or granular surface were obtained using fluidized bed chemical vapor deposition of acetylene by adjusting the reaction parameters. The core of the NING has a highly ordered graphite structure and the shell has a disordered structure. Compared with natural graphite (NG) spheres, MNG with a core-shell structure shows improved first cycling efficiency and cyclability. Especially, the NING spheres with a granular surface possess 84% retention of the first discharge capacity after 41 cycles, owing to effective decrease of the contact resistance and increase of contact area between the NING spheres.

关键词: fluidized bed chemical vapor deposition;core-shell structure;pyrolytic;carbon;modified natural graphite;lithium ion secondary battery;lithium-ion batteries;chemical-vapor-deposition;1st-cycle charge loss;anode material;encapsulated graphite;surface-area;infiltration;performance;improvement;pyrocarbon

STUDIES ON PRIMARY CRYSTALLIZATION OF RAPIDLY QUENCHED Al-Ni-Cu-Nd METALLIC GLASS BY USING HIGH RESOLUTION TRASMISSION ELECTRON MICROSCOPY

Y.D.Xiao , W.X.Li , D.Jacovkis , M.T.Clavaguera-Mora , J.Rodriguez-Viejo , N.Clavaguera

金属学报(英文版)

Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous rib-bon and the annealed samples were closely examined by means of differential scan-ning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in pri-mary crystallization into α-Al nanocrystalline particles, in order to understand struc-tural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of α-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at 110℃ for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃/min consist of large amount of α-Al fec crystal nanoparticles dispersed uni-formly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crustal is soft impinaement, instead of geometric impinqement.

关键词: rapid solidification , null , null