Two-step hydrolysis of amygdalin in molds

Mucor circinelloides LU M40 and Penicillium aurantiogriseum P 35, characterized by extracellular beta-glucosidase activity on cyanogenic glycosides, hydrolyse amygdalin by a two-step reaction mechanism being the first step of hydrolysis, from amygdalin to prunasin, very rapid (15 min) and the second one, from prunasin to mandelonitrile, much slower (120 min).     

PM soft magnets in new applications

Both hard and soft magnetic materials were discussed in several presentations and posters at the EURO PM 2001 conference in Nice. The present article summarises some of the key aspects relating to soft magnetic properties of ferrous PM materials and composites for automotive and other applications.     

Anisotropy of rare-earth magnets

Rare-earth intermetallics such as Nd₂Fe₁₄B and Sm-Co are widely used as high-performance permanent magnets, because they combine high magnetocrystalline anisotropy with reasonable magnetization and Curie temperature. The anisotropy is a combined effect of spin-orbit coupling and electrostatic crystal-field interactions. The main contribution comes from the rare-earth 4f electrons, which are well-screened from the crystalline environment but exhibit a strong spin-orbit coupling. In this limit, the magnetocrystalline anisotropy has a very transparent physical interpretation, the anisotropy energy essentially being equal to the energy of Hund's-rules 4f ion in the crystal field. The corresponding expression for the lowest-order uniaxial anisotropy constant K₁ is used to discuss rare-earth substitutions, which have recently attracted renewed interest due to shifts in the rare-earth production and demand. Specific phenomena reviewed in this article are the enhancement of the anisotropy of Sm₂Fe₁₇ due to interstitial nitrogen, the use of Sm-Co magnets for high-temperature applications, and the comparison of rare-earth single-ion anisotropy with other single-ion and two-ion mechanisms.     

New ways with magnets

Bonded iron composite material used in conjunction with high-energy neodymium-iron-boron permanent magnets provides an opportunity to custom-engineer performance characteristics to meet specific electromagnetic requirements…     

High field NMR magnets

Impressive progress has been made during past decades in many research fields which apply NMR, pushing the proton resonance frequency from 30 MHz (0.7 T) to about 800 MHz (19 T). In this overview we analyze different technologies for generation of the required fields and their potential for future developments toward even higher resonance frequencies of up to 2 GHz.     

Additive manufacturing of Sm-Fe-N magnets

Isotropic Sm-Fe-N bonded magnets were obtained by additive manufacturing(AM). The technique used was the so-called powder bed fusion(PBF) and the feedstock was composed of a polymeric binder(PA-12) and Sm-Fe-N flake particles(Nitroquench-P). The AM set-up equipment uses a computer-controlled CO_2 laser beam to melt the binder and constructs magnets layer-by-layer. In order to develop this study, a cylinder with 10 mm of both height and diameter was selected as the shape of samples. Specimens were analyzed by scanning electron microscopy(SEM) and X-ray diffraction(XRD). Magnetic properties were measured in a hysteresis graph. XRD results indicate that there is no degradation of the main magnetic phase(SmFe_7 N_x). In the AM component, porous regions were identified on SEM micrographs, as well as magnetic particles and polymeric binder. Remanence values(B_r) as great as 0.3 T are achieved, while intrinsic coercivities remain in the range from 616 up to 642 kA/m. An additional isostatic compression of the parts results in greater remanence, which is directly proportional to the density increase. Coercivity is also sensitive to the porosity decrease, probably due to a better interlocking of particles. Current results indicate AM as a promising route for near net-shape manufacturing of Sm-Fe-N permanent magnets, a market niche yet to be widely explored.