| 摘要 |
<p>Stabilisation of ferromagnetic CrO2 consists of dispersing CrO2 particles in water and pptg. on it an orphosphate, or hydroxide of Zn, Al or Cr, sepg. the coated particles, treating them with H3PO4 in an amt. calculated to give a molar ratio between the ZnO introduced in the first step to the P2O5 introduced in the two subsequent steps of 0.286-0.667 a ratio of Al2O3: P2O5 of 0.225-0.500 or a polyphosphate of Cr where the Cr2O3 to P2O5 ratio is 0.143-0.333, so that the coating formed is a corresp. hydrate of the appropriate phosphate. The prod. is then heat treated at 100-350 degrees C when zinc is used and 275-350 degrees C using Al or Cr. The stability in water and wrt. oxidisable organic substances esp. those used with as functional gps. in magnetic recording tapes, such as hydroxy and amino gps. is improved. Hence the loss of residual magnetism after a lapse of time is reduced. This is effected without consumption of part of the CrO2 during this stabilisation as in prior art.</p> |
