Additive manufacturing of isotropic NdFeB PPS bonded permanent magnets

Extrusion based additive manufacturing of polymer composite magnets can increase the solid loading volume fraction with greater mechanical force through the printing nozzle as compared to traditional injection molding process. About 63 vol% of isotropic NdFeB magnet powders were compounded with 37 vol% of polyphenylene sulfide and bonded permanent magnets were fabricated while using Big Area Additive Manufacturing without any degradation in magnetic properties. The polyphenylene sulfide bonded magnets have a tensile stress of 20 MPa, almost double than that of nylon bonded permanent magnets. Additively manufactured and surface-protective-resin coated bonded magnets meet the industrial stability criterion of up to 175 °C with a flux-loss of 2.35% over 1000 h. They also exhibit better corrosion resistance behavior when exposed to acidic (pH = 1.35) solution for 24 h and also annealed at 80 °C over 100 h (at 95% relative humidity) over without coated magnets. Thus, polyphenylene sulfide bonded, additively manufactured, protective resin coated bonded permanent magnets provide better thermal, mechanical, and magnetic properties

Additive Manufacturing of Isotropic NdFeB PPS Bonded Permanent Magnets

Extrusion based additive manufacturing of polymer composite magnets can increase the solid loading volume fraction with greater mechanical force through the printing nozzle as compared to traditional injection molding process. About 63 vol% of isotropic NdFeB magnet powders were compounded with 37 vol% of polyphenylene sulfide and bonded permanent magnets were fabricated while using Big Area Additive Manufacturing without any degradation in magnetic properties. The polyphenylene sulfide bonded magnets have a tensile stress of 20 MPa, almost double than that of nylon bonded permanent magnets. Additively manufactured and surface-protective-resin coated bonded magnets meet the industrial stability criterion of up to 175 °C with a flux-loss of 2.35% over 1000 h. They also exhibit better corrosion resistance behavior when exposed to acidic (pH = 1.35) solution for 24 h and also annealed at 80 °C over 100 h (at 95% relative humidity) over without coated magnets. Thus, polyphenylene sulfide bonded, additively manufactured, protective resin coated bonded permanent magnets provide better thermal, mechanical, and magnetic properties

Investigation of phase transformations and corrosion resistance in Co/CoCo2O4 nanowires and their potential use as a basis for lithium-ion batteries

The paper is devoted to the study of the effect of thermal annealing on the change in the structural properties and phase composition of metal Co nanostructures, as well as the prospects of their use as anode materials for lithium-ion batteries. During the study, a four-stage phase transition in the structure of nanowires consisting of successive transformations of the structure (Со-FCC/Co-HCP) → (Со-FCС) → (Со-FCC/СоСо2О4) → (СоСо2О4), accompanied by uniform oxidation of the structure of nanowires with an increase in temperature above 400 °C. In this case, an increase in temperature to 700 °C leads to a partial destruction of the oxide layer and surface degradation of nanostructures. During life tests, it was found that the lifetime for oxide nanostructures exceeds 500 charge/discharge cycles, for the initial nanostructures and annealed at a temperature of 300 °С, the lifetimes are 297 and 411 cycles, respectively. The prospects of using Co/CoCo2O4 nanowires as the basis for lithium-ion batteries is shown. © 2019, The Author(s)

Solution Combustion Synthesis, Characterization, and Photocatalytic Activity of CuBi₂O₄ and Its Nanocomposites with CuO and α‑Bi₂O₃

The ternary compound, CuBi₂O₄, a 1:1 stoichiometric derivative of the two component oxides CuO and Bi₂O₃, has attracted attention from the solar water splitting and photocatalysis communities as a <i>p</i>-type semiconductor responsive to visible light. This study demonstrates that solution combustion synthesis (SCS) can be used to prepare powders not only of this compound but also nanocomposites with either CuO or Bi₂O₃ in excess. This was simply done by tuning the SCS precursor mixture composition. The synthesized crystalline samples were characterized by powder X-ray diffraction (with Rietveld refinement for phase purity), diffuse reflectance UV–visible spectroscopy, electron microscopy, and photoelectrochemical (PEC) techniques. The band structure and photoactivity of these oxides were probed by linear sweep voltammetry and by measuring their photoaction spectra (internal photon-to-electron conversion efficiency vs wavelength). The photoactivity (attributed to hydrogen evolution and CO₂ photoreduction) was considerably improved in the CuO/CuBi₂O₄ nanocomposites because of electron transport of the photogenerated charge carriers between the CuBi₂O₄ and the CuO nanoparticles