[en] The magnetic and structural properties of the compounds R(Fe_1-xCo_x)₉Si₂C_1.0 (R=Ce, Nd, Sm; x=0.0, 0.1, 0.3, 0.5) were studied. Upon substitution of Co for Fe, the Curie temperature increases, but the magnetization decreases in all compounds. The easy magnetization directions of Ce(Fe_1-xCo_x)₉Si₂C_1.0 and Nd(Fe_1-xCo_x)₉Si₂C_1.0 lie in the basal plane. Sm(Fe_1-xCo_x)₉Si₂C_1.0 compounds have easy-axis anisotropy, and the anisotropy field at 1.5 K increases with increasing Co content. Moreover, a first-order magnetization process is observed at 1.5 K in Nd(Fe_1-xCo_x)₉Si₂C_1.0. Below 120 K, a spin reorientation and a spin-glass-like transition are observed in Nd(Fe_1-xCo_x)₉Si₂C_1.0, and the transition temperature decreases with increasing Co content

[en] Anisotropic SmCo_7-xCu_x (x=0-4.5) ribbons have been prepared by melt spinning at a low wheel speed of 5 m/s. Scanning electron microscopy results show that Cu-free and Cu-containing ribbons consist of equiaxed and columnar dendrite grains, respectively. The arrangement of columnar dendrite grains of the ribbons was found to be more ordered with increasing Cu content x. Together with the results of magnetic measurement, it is derived that Cu substitution is helpful to enhance the degree of preferred orientation of the c-axis of the columnar dendrite grains parallel to the longitudinal direction of the ribbons. In this way the rectangularity of demagnetization curves and the remanence ratio (defined as the ratio of remanent magnetization to saturation magnetization) of the samples are significantly improved. A remanence ratio of 0.90, which is close to that of sintered SmCo magnets, has been achieved in the ribbons with x=2.5. Because the domain-wall-energy gradient between the 1:5 and 2:17 phases, which determines the value of the coercive force arising from the domain wall pinning, may increase with x, the coercivity of the samples with x≤3.5 increases strongly with x. Without heat treatment, a coercive force (_iH_c) of up to 9.2 kOe is obtained in the ribbons with x=3.5

[en] We have succeeded in introducing moderate quantities of nitrogen into TbTiFe₁₁ and DyTiFe₁₁ compounds. X-ray diffraction showed that the ThMn₁₂-type structure is retained, but that the unit cell volume is slightly increased. More significantly, the nitrogenation has quenched the spin reorientations in TbTiFe₁₁ and DyTiFe₁₁, and has made the easy magnetization directions (EMD) of their nitrides along the c axis from 0 K to Curie temperatures. (orig.)

[en] Without annealing, Pr₁₃Fe_80-xCo_xC₅B₂ (x=0-20) ribbons with a coercive force of more than 1.0 T have been prepared by melt spinning. Due to Co addition, rectangularity of demagnetization curves is significantly improved. The remanence and maximum energy product of the samples are obviously increased with the increase of x (x≤15). A maximum energy product of 145.7 kJ/m³, which is the highest value among all that previously reported in the R₂Fe₁₄C-type (R=Nd or Pr) ribbons, has been achieved in the ribbons (x=15) prepared directly by melt spinning. The Curie temperatures of 2:14:1 carbides of the ribbons in the as-quenched state increase linearly with x at an average rate 12 K/at%Co. Similar to B and Cu, Co addition is found to accelerate the formation of 2:14:1 carbides

[en] Short communications only

[en] YBa₂(Cu_0.95M_0.05)₃O_7-δ were identified as single phase with M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn. Substitution of Fe, Co, Ni and Zn for Cu makes T_c decrease significantly, while at the same content, no destructive effect on T_C was observed in the replacement of Cu with Ti, V, Cr and Mn. The site occupation of Ti, Mn, Fe and Co ions has been investigated by using neutron diffraction technique, and strong site preference for these ions were observed. Based on these results, the two different Cu sites and their relatoinship to the superconductivity in YBa₂Cu₃O_7-δ are discussed. The substitution effect for copper on magnetic properties in YBa₂(Cu_0.-9₅M_0.05)₃O_7-δ and the correlation between magnetic and superconducting properties are reported

[en] Graphical abstract: Electrochemically cathodic exfoliation of graphite into few-layer graphene sheets in room temperature ionic liquids (RTILs) N-butyl, methylpyrrolidinium bis(trifluoromethylsulfonyl)-imide (BMPTF₂N). -- Highlights: • Few-layer graphene sheets were prepared through electrochemically cathodic exfoliation in room temperature ionic liquids. • The mechanism of cathodic exfoliation in ionic liquids was proposed. • The derived activated graphene sheets show enhanced electrochemical properties. -- Abstract: Electrochemically cathodic exfoliation in room temperature ionic liquids N-butyl, methylpyrrolidinium bis(trifluoromethylsulfonyl)-imide (BMPTF₂N) has been developed for few-layer graphene sheets, demonstrating low levels of oxygen (2.7 at% of O) with a nearly perfect structure (I_D/I_G < 0.05). The mechanism of cathodic exfoliation in BMPTF₂N involves the intercalation of ionic liquids cation [BMP]⁺ under highly negatively charge followed by graphite expansion. Porous activated graphene sheets were also obtained by activation of graphene sheets in KOH. Transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize these graphene materials. The electrochemical performances of the graphene sheets and porous activated graphene sheets for lithium-ion battery anode materials were evaluated using cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy

[en] Mn_3O_4/graphite powder (Mn_3O_4/GhP) composite was successfully obtained utilizing an alternating voltage induced electrochemical method. It was found that Mn_3O_4 particles (∼20 nm) resulted from Mn electrodes were well dispersed on the surface of GhP. The electrochemical performances of Mn_3O_4/GhP material as anode for lithium-ion batteries were investigated, demonstrating high specific capacity and excellent cycling stability with a high charge-discharge capacity of 1007.4 mAh g"−"1 after 50 cycles at a current density of 100 mA g"−"1

[en] High-purity ternary Pr₁₃Fe₈₀B₇ magnetic powder with high anisotropy is obtained by a modified hydrogenation disproportionation desorption recombination (HDDR) process in this work. This powder exhibits a record-high B_r of 1.05 T, and has a good crystal texture along the c axis. It is found that the formation of HDDR Pr₁₃Fe₈₀B₇ anisotropy is related to a rodlike disproportionation microstructure. We also show that by changing the HDDR conditions, an intrinsic coercivity of 800 kA/m and an energy product of 144 kJ/m³ are obtained on this powder. The details of the modified HDDR process are also presented in this paper

[en] Structure and magnetic properties of YFe₁₀Mo₂ and YFe₁₀Mo₂N compounds have been studied with neutron diffraction and self-consistent spin-polarized linear muffin-tin orbital (LMTO) band calculation. The diffraction results indicate that the nitrogen atoms are located at 2b sites with nearly 99% occupancy. The electronic structure calculations give excellent results for site-dependent Fe magnetic moments and hyperfine fields. The interstitial-atom effect on the local magnetic moments and hyperfine fields is explained with magneto-volume effect and chemical bonding effect. The contributions of the magneto-volume effect and the chemical bonding effect of the nitrogen to the magnetic moments (μ_Loc), Fermi-contact hyperfine fields (H_FC) and isomer shifts (IS) are reported. (author)