Patent ID: 7922917

Claim:
A method of making porous, ferro- or ferrimagnetic, glass particles comprising: a) providing a suspension of ferro- or ferrimagnetic iron oxide particles, b) adding a tetraalkoxysilane to the suspension of the ferro- or ferrimagnetic iron oxide particles at a pH between 6 and 8, c) hydrolyzing the tetraalkoxysilane and precipitating silica glass on the ferro- or ferrimagnetic iron oxide particles by adding a buffer having a pH lower than 6 or higher than 9 to the suspension to form ferro- or ferrimagnetic, porous glass particles, d) separating the resulting porous, ferro- or ferrimagnetic, glass particles from suspension, e) washing the separated porous, ferro- or ferrimagnetic, glass particles with an anhydrous alcohol, and f) drying the porous, ferro- or ferrimagnetic, glass particles at a temperature below the Curie temperature, wherein the drying is at 200° C. to about 500° C.