▎ 摘　　要

NOVELTY - Hollow magnetic iron(II,III) oxide nano-doped microspheres is hollow microsphere, spherical wall of the hollow microspheres includes magnetic Fe3O4 nanoparticles and dopants, the dopant is graphene, graphene oxide, nano graphite sheet, single-walled carbon nanotubes, multi-wall carbon nanotubes. The dopant is 10-60% of the magnetic Fe3O4 nano-particles. USE - The hollow magnetic iron(II,III) oxide nano-doped microspheres is useful for magnetorheological fluid (claimed). ADVANTAGE - The hollow magnetic iron(II,III) oxide nano-doped microspheres further increase particle ratio surface area and to obtain higher magnetic susceptibility and increases using effect of the magnetic particle. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for (1) preparing magneto-rheological fluid hollow magnetic Fe3O4 nanometer doped microsphere comprising (1) preparing monodisperse silicon dioxide ball nanometer particles, (2) adding the ferrous source in de-ionized water to prepare the ferrous ion solution, (3) adding doping agent and dispersant into de-ionized water to prepare dispersion, (4) stirring, adding hydrofluoric acid control F atom and Fe atom is 1:1-1:5, slowly dropping ammonia to adjust the pH value to 3.0-10.0, adding monodisperse silicon dioxide ball nano grain, control ferrous ion 15-85 wt.% silicon dioxide, stirring and reacting at -90 degrees C at 45 degrees C water bath, carrying out centrifugal separating and washing with de-ionized water, drying to obtain powdery product A, (5) adding the powdery product A at 400-900 degrees C, roasting for 3-8 hours under a reducing atmosphere, cooling to obtain the powder-shaped product B, adding sodium hydroxide solution in the powder-shaped product B, reaction to remove the silicon dioxide core in -90 degrees C water bath at 60 degrees C, centrifugal separation and washing with de-ionized water, and drying to obtain hollow magnetic Fe3O4 nano doped microsphere; and (2) magneto-rheological fluid comprising hollow magnetic Fe3O4 nano doped microsphere.