Iron-silicon-oxide particles with improved heating rate in magnetic and electromagnetic alternating fields

摘要

Iron-silicon-oxide particles comprises: a core comprising iron-oxide modifications of maghemite, magnetite and hematite; and an outer shell made of amorphous silicon dioxide, where (a) H 0 . 2 nm/H 0 . 2 5nm is = 0.2 and H 0 . 2nm is brightness of Debye-Scherrer diffraction ring with a lattice spacing of 0.20 +- 0.02 nm, comprising hematite and magnetite, and H 0 . 2 5nm is brightness of Debye-Scherrer diffraction ring with a lattice spacing of 0.25 +- 0.02 nm, and (b) the crystallite diameter of the hematite, as determined by X-ray diffraction is greater than 120 nm. Iron-silicon-oxide particles comprises an core including iron-oxide modifications of maghemite, magnetite and hematite and an outer shell, which is made of amorphous silicon dioxide, where (a) H 0 . 2 nm/H 0 . 2 5nm is = 0.2 and H 0 . 2nm is brightness of Debye-Scherrer diffraction ring determined by electron diffraction with a lattice spacing of 0.20 +- 0.02 nm, comprising hematite and magnetite, and H 0 . 2 5nm is brightness of Debye-Scherrer diffraction ring determined by electron diffraction with a lattice spacing of 0.25 +- 0.02 nm, comprising maghemite, magnetite and hematite, and (b) the crystallite diameter of the hematite, as determined by X-ray diffraction is greater than 120 nm. Independent claims are also included for: (1) producing the iron-silicon-oxide particles having a core-shell structure comprising (a) igniting and reacting a mixture containing (a1) 0-30% of the total amount of at least one hydrolyzable and/or oxidizable silicon compound, (a2) at least one oxidizable and/or hydrolyzable iron compound, (a3) at least one hydrogen-containing fuel gas, or (a4) at least one oxygen-containing gas, in a first zone 1 of a flow reactor, (b) adding 70-100% of total amount of at least one hydrolyzable and/or oxidizable silicon compounds to the reaction mixture into a second zone 2 of the flow reactor, (c) optionally cooling the reaction mixture in the zone 3 of the flow reactor, subsequently separating the solids from gaseous or vaporous substances and, optionally treating the solids with a surface modifier; and (2) a silicone rubber comprising the iron-silicon-oxide particles.