Production of redispersible metal (hydr)oxide nanoparticles, especially magnetic metal oxide for ferrofluid, involves precipitation from aqueous metal salt solution with base in presence of polymeric carboxylic acid

摘要

Production of redispersible metal (hydr)oxides (I) with a volume-weighted average crystallite size of 1-20 nm comprises precipitating (I) from aqueous solutions of metal salts by increasing the pH with a base in the presence of polymeric carboxylic acid (II); and separating (part of) the aqueous phase from (I). Independent claims are also included for (a) redispersible (I) produced in this way; (b) a process for controlling the volume-weighted average crystallite size of (I) in the 1-30 nm range.