Strong permanent magnets made from ferrite powder - esp. flexible magnets, using inexpensive process to produce high energy prod.

摘要

A mixt. is made of Fe2O3; =1 carbonate of Ba, Sr, and/or Pb; and (a) 0.5-15%, pref. 1-10 wt.% of =1 alkali(ne earth) halide; plus (b) 0.2-7%, esp. 0.5-3% alkali(ne earth)borate. The mixt. is calcined at 850-1100 degrees C., pref. 900-1000 degrees C., for =15 minutes. The powder then has a magneto-plumbite structure, and is mixed with a thermoplastic or-setting binder (c) and aligned by mechanical and/or magnetic means. Cpd. (a) is pref. NaF; whereas cpd. (b) is pref. B4 O7 Na2, 10H2O, using wt. ratio a:b 2-5:1 and 3-10% NaF(a). After adding binder (c) and calendering, 15% by vol. of the grains pref. have an intrinsic coercive (iHc) below 300 Oe, and/or 30 vol.% have iHc 2500 Oe. Used for the inexpensive mfr. of rigid or flexible magnets with energy prod., BH max x 106 G-Oe rising up to 1.8.