Blending Powder Process for Recycling Sintered Nd-Fe-B Magnets

The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.

Impact of Sr on the performance of BaTi0.9Zr0.1O3–BaTiO3 dielectric powders

BaTi 0.9 Zr 0.1 O 3– Ba 1-x Sr x TiO 3 fine-powders are synthesized by two-step liquid phase method. Phase analysis and microstructure evaluation conducted by X-ray diffraction and scanning electron microscopy confirm the perovskite structure of the ceramic grain. Different Sr content is considered to optimize the density and dielectric performance. The dielectric constant increases and dielectric loss decreases with the rising of Sr content until x = 0.05. At the doping content of 5%, the dielectric constant maximum of 42,430 and excellent Y5V dielectric material can be obtained due to composition inhomogeneity and compact properties. Its dielectric properties are as follows: ε RT = 36,914, tan δ < 0.09, ΔC/C 20° C at -30° C and 80°C are -58.98% and 14.94%, respectively, and the breakdown strength Eb ≥ 5.2 kV ⋅ mm -1.

SINTERING BEHAVIOR AND DIELECTRIC PROPERTIES OF Ba0.985Bi0.01TiO3-Ba0.9955La0.003TiO3 FINE-POWDERS

Ba 0.985 Bi 0.01 TiO 3- Ba 0.9955 La 0.003 TiO 3 fine-powders were synthesized by two-step soft chemistry method. Phase analysis and microstructure evaluation conducted by X-ray diffraction and scanning electron microscopy confirmed the provskite structure of the ceramic grain. Different sintering temperatures were considered to optimize the density and dielectric properties. The maximum dielectric constant decreased first, and then increased before dropping again, reflecting the change of relative density. Samples sintered at 1270°C exhibited the best temperature stability due to composition inhomogeneity and compact properties. The dielectric properties of the sample sintered at 1270°C were: ε = ~8,960, tan δ < 0.28, ΔC/C20° C at -55°C, 110°C and 150°C were -5.2%, 13.8% and -12.8%, respectively.