| abstract |
In each case a) a BET-surface area of 10 to 80 m 2 / g, b) a thickness of the shell of 2 to 30 nm and c) an iron oxide content of 60 to 90% by weight and 10 to 40 weight Iron-silicon oxide particles having a core-shell structure with a silicon dioxide content of%, wherein d) the proportion of iron, silicon and oxygen is at least 99% by weight based on the packed particles and e) the core is crystalline Iron oxide includes hematite, magnetite and magnetite, f) the shell consists of amorphous silicon dioxide, g) one or more compounds or a plurality of compounds of silicon, iron and oxygen elements are present between the shell and the core . |