Magnetic and morphological characterization of Nd2Fe14B magnets with different quality grades at low temperature 5\ue2\u80\u93300\ue2\u80\uafK

An increasing number of cryogenic devices may benefit from the use of Nd2Fe14B permanent magnets. However, it is necessary to precisely know their behavior because magnetization varies significantly due to Spin Reorientation Transition. In this work, magnetic and morphological characterization of Nd2Fe14B commercial polycrystalline magnets with different quality grades from 5 to 300 K is provided. A set of magnets ranging from N35 to N52 quality have been analyzed. Mean grain dimension as well as material composition elements are provided. Higher quality magnets show smaller mean grain dimensions. Regarding cryogenic temperatures, the well know spin transition effect appears in all the magnets as expected, however, the transition temperature occurs at different temperatures in a range from 112 to 120 K which is lower than those obtained for single crystal samples. Moreover, the relative variation of the remanence from 300 to 5 K is lower than 4% while the maximum expected variation is in average 11%. As extra information, the same analyzes are provided for additional quality grades N40M, N40S, N40SH and N40UH

Magnetic non-contact harmonic drive

The MAGDRIVE project, granted by the Space program of the EU-FP7, is developing a gear able to produce reduction ratios from 1 to several hundreds by means of magnetic teeth. The teeth, unlike the conventional gears, do not touch one to other. This makes that this gear does not need any kind of lubrication. In case that the maximum torque is passed over the axle simply clutches, but nothing breaks down. Therefore, it has an intrinsic antijamming characteristic. It is also reversible: it can reduce but also multiply the velocity. It can also go clockwise or anticlockwise. Ratio, maximum torque, stiffness and damping can be customized. Even more it can also be customized to be direct or inverted (inverting the sense of the rotation). A low noise level is also a remarkable feature of this kind of device. These characteristics make this technology very attractive for a number of different fields like aerospace, automation, automotive and others. Two different prototypes have been developed: the first one is a "room-temperature prototype" for working temperature from -40\ub0C to 100\ub0C, while the second one is a "cryogenic prototype" that can work at temperature as low as 70 K. The results of the tests for the first prototype are shown in this work. Copyright \ua9 2013 by ASME