Hierarchically nanostructured barium sulfate fibers

BaSO₄ nanostructures with controlled morphologies were successfully produced via one-step process through precipitation of BaSO ₄ in aqueous and organic media. The synthesis is carried out by mixing solutions of BaCl₂ and Na₂SO₄ in presence of EDTA (disodium ethylenediaminetetraacetic acid) at room temperature. The influence of the reaction conditions such as initial reactants concentration, pH, EDTA/[Ba²⁺] ratio and aging on the BaSO ₄ nanoparticles organization is studied. Using EDTA in aqueous media, spherical secondary particles of 500 nm diameter are obtained, which are formed by 4 nm size primary particles. With dimethyl sulfoxide and small amounts of water (5%) and EDTA, the aging process allows the production of long homogeneous fibers, related to hierarchical organization of BaSO₄ nanoparticles. Direct observation of self-assembling of primary particles by HRTEM allows proposing a mechanism for fiber formation, which is based on multipolar attractions that lead to a brick-by-brick organization along a preferential orientation. Results evidence the role of EDTA as controlling agent of the morphology and primary and secondary mean particle size.