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Large scale processing of HDDR powders

Research has been carried out in order to assess the critical factors in the production of neodymium-iron-boron hydrogenation - disproportionation - desorption - recombination (HDDR) powder.

With respect to isotropic neodymium-iron-boron HDDR optimization, the most critical parameters of the HDDR process, applied to neodymium-iron-boron magnets have been assessed. Particularly, the importance of disproportionation temperature and time and the importance of the recombination temperature and time.

With respect to anisotropic neodymium-iron-boron HDDR powder production, a technique for examining regions of common orientation using the Kerr effect has been used extensively, to aid determination of the optimum processing route for the production of anisotropic material.

With respect to production of hot pressed neodymium-iron-boron HDDR magnets, large quantities of hot pressed HDDR magnets have been produced using industrial equipment. It was found that the HDDR powder hot presses in a similar fashion to MQ powder and so the equipment in use for hot pressing MQ material need not be adapted to hot press HDDR powder.

With respect to large scale production of neodymium-iron-boron HDDR powder and samarium-iron-nitrogen powder, it was determined that the best means to carry out large scale production of HDDR powder was to split the process into two halves. The hydrogenation - disproportionation stages being carried out in batch sizes of up to 30 Kg in an adapted vacuum chamber furnace, whilst the sensitive desorption - recombination stages were carried out in the rotating reactor, developed for this project.

A full economic analysis of the magnets found that HDDR powder, particularly when hot pressed, compared very favourably in economic terms when compared with MQ magnets. Anisotropic HDDR powder would also compare very favourably with powdered MQ3 material.

Reported by

University of Birmingham
B15 2TT Birmingham
United Kingdom
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