Fe2 P-based magnetocaloric compounds are an important and industrially relevant material class for magnetic refrigeration, yet their microstructure and its influence on the magnetic properties is ...hardly discussed in literature. We prepared Mn-Fe-P-Si-based samples using a powder metallurgical process and analyzed their microstructural and thermomagnetic properties. XRD, SEM, EDX and EBSD analysis reveal a phosphorous depleted cubic secondary phase in many samples with distinct microstructural properties giving an insight into the phase formation process. A porous morphology was found, hindering the direct application of the materials a magnetocaloric heat exchanger in bulk-like structures. The “virgin” effect could be in-situ observed for the first time on a macroscopic scale using temperature-dependent optical microscopy. Thermomagnetic measurements reveal a difference in transition temperature Tt in comparison to literature values which is attributed to a processing induced deviation from the nominal composition. The isothermal entropy change ΔST and adiabatic temperature change ΔTad were studied as well as their cyclic behavior. The effect of secondary phases is discussed and the importance of the metal/non-metal (M/NM)-ratio is shown. The article presents a road map for the preparation of Mn-Fe-Si-P-based alloys with highest quality.
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The magnetic hardening of ARMCO® and FeCo17 in a severe plastic deformation and an incremental forming process is presented. The enhancement of the coercivity, which depends on the strain induced by ...the forming process, is investigated. Strain induced during the incremental forming process are analysed in FE-simulations.
A systematic study of the dependence of the Grain Boundary Diffusion Process (GBDP) on texture using Dy and Dy-Nd-Cu in microcrystalline sintered and nanocrystalline hot deformed Nd-Fe-B magnets was ...performed. Diffusion parallel or perpendicular to the texture direction, the nominal c-axes orientation in the polycrystals, was investigated. By measuring thin slices from the respective samples, coercivity as a function of (i) magnet thickness and (ii) diffusion depth was obtained showing that GBDP efficiency depends on the diffusion direction, diffusion source as well as the grain morphology originating from the magnet production route. In nanocrystalline hot deformed magnets perpendicular diffusion is superior due to the platelet-like shape of the grains. Microcrystalline sintered magnets consist of equiaxed grains hence the main effects originate in anisotropic lattice diffusion and pole surface hardening. The magnetic properties are correlated with a comprehensive analysis of microstructure, chemistry and magnetization reversal.
•Comparing texture's effect on GBDP in Dy, Dy-Nd-Cu in microcrystalline sintered & nanocrystalline hot deformed magnets.•GBDP efficiency relies on diffusion direction, source, and grain morphology from the magnet production route.•Perpendicular diffusion is more effective in hot deformed (nanocrystalline) magnets due to their platelet-like grain shapes.•Comprehensive analysis links magnetic properties with microstructure, chemistry, and magnetization reversal studies.
Ring-opening polymerization of ε-caprolactone (CL) and δ-valerolactone (VL) was carried out using the initiator system Sm2I(NPPh3)5(DME) in the presence of toluene. Experimental molecular weights ...were in good agreement with the theoretical molecular weights for CL0/10 up to 350. Polydispersities are low at 0−20 °C but increase at higher temperatures. Addition of small amounts of coordinating solvents such as THF and DME decreased the rate of polymerization and thereby reduced the polydispersity. The active polymer chain ends have been shown by sequential copolymerization of CL and VL, resulting in block copolymers.
As cyclopentadienide equivalents, the first homoleptic phosphoraneiminato complexes of rare earth elements with the very small coordination number four (see, for example, the ytterbium compound ...shown) are excellent initiators for the ring‐opening polymerization of lactones.
![Novel [Sm2I(NPPh3)5(DME)] I...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0024-9297/small "Novel [Sm2I(NPPh3)5(DME)] Initiator for the Living Ring-Opening Polymerization of ε-Caprolactone and δ-Valerolactone")
