Synthesis of Nd2Fe14C compound by high-energy ball-milling Nd-Fe alloy in heptane and annealing under vacuum

A simple synthesis route for the Nd2Fe14C compound with good permanent magnetic properties is presented. Being high-energy ball-milled in heptane (C7H16) for 8 h, the NdFe3.5 alloy consisting of Nd2Fe17 and Nd phases disproportionates into NdH2+delta d and alpha-Fe. Subsequently, NdH2+delta decomposes when annealed from room temperature to 900 degrees C under vacuum, and H-2 is released. Meanwhile Nd2Fe14C, NdC and little alpha-Fe phases are formed in the final product. H and C atoms come from the decomposition of heptane. Coercivity of 1.39 T and maximum magnetic energy product of 62.7 kJ m(-3) have been achieved. Too short a ball-milling time results in the insufficient disproportionation of NdFe3.5 alloy and the residue of Nd2Fe17 phase in the final product. Too long a ball-milling time results in the appearance of NdC2 and more alpha-Fe phases besides Nd2Fe14C and NdC phases. Hexane (C6H14), octane (C8H18) and nonane (C9H20) have been proved to have a similar effect to heptane.