Hard Magnetic Properties of Sm-Fe-C Based Alloys Prepared by Mechanical Alloying

The structure and magnetic properties of SmyFe100-1.5yC0.5y(y=8～20) alloys prepared by mechanical alloying (MA) from Sm, Fe and graphite have been investigated systematically. In order to improve hard magnetic properties of the alloys prepared by mechanical alloying, a new method consisting of re-milling and re-annealing was developed. After being re-milled and re-annealed, the Curie temperature TC of the Sm-Fe-C alloys changes. The TC of 2:17 phase increases, whereas the TC of 2:14:1 phase decreases. After being re-annealed at low temperatures, the grain sizes of hard phases are smaller than those in the alloys annealed at high temperatures. The effects of Co or Ti substitution for Fe are studied.

Crystalline Behavior and Magnetic Properties of Nd_(60) Fe_(30-x)Al_(10)Co_x (x=0,5,10) Bulk Amorphous Alloys

Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity ( i H c) increases while the saturation magnetization( σ s) and remanence ( σ r) decrease. The Curie temperature for the as cast Nd 60 Fe 30- x Al 10 Co x alloys increases from 451 K for x =0 to 468 K for x =10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.

High coercivity cobalt carbide nanoparticles as electrocatalysts for hydrogen evolution reaction

Cobalt carbide nanoparticles(NPs),as a typical carbide material,have attracted extensive attention in the fields of magnetism and electrochemistry.Herein,we adopted a modified solution route by pyrolysis long-chain amines at high temperatures to obtain Co_(2)C NPs,in which different forms of Co NPs were used as precursors.The results reveal that no matter what the structure of the precursor and the type of long-chain amine,single-phase Co_(2)C NPs with good crystallinity are obtained.At the same time,carbonization of hexagonal close packed(hcp)cobalt as the precursor gives the materials high magnetic anisotropy,exhibiting a large coercivity(~1,300 Oe)on the nanoscale.In terms of catalytic properties,benefiting from intrinsically high activity of Co_(2)C NPs,the material demonstrates superior hydrogen evolution reaction(HER)performance,with optimal overpotential as low as 73 mV at the current density of 10 mA·cm^(-2).This provides new ideas for the further development of transition metal carbides(TMCs)and the improvement of their magnetic and electrocatalytic properties.