| 摘要 |
<p>Pyrogenic oxidic particles with a chloride content of 50-1000 ppm contain super paramagnetic metal oxide domains having a diameter of 3-20 nm in a non-magnetic matrix containing a metal oxide or metalloid oxide. An Independent claim is also included for processes for producing pyrogenic oxidic particles. Preferred Features: The carbon content is less than 500 ppm. The BET surface area is 10-600 m<2>/g. The blocking temperature is not more than 150 K. The amount of super paramagnetic metal oxide domains amount is 1-99.6 wt.%. The super paramagnetic metal oxide domains contain oxides of iron (Fe), chromium (Cr), europium (Eu), yttrium (Y), samarium (Sm) or gadolinium (Gd). The particles are made from gamma-ferric oxide ( gamma -Fe2O3), iron oxide (Fe3O4), mixtures of gamma -Fe2O3 and Fe3O4, and non-magnetic compounds containing iron.</p> |
