Formation of Mesoporous BaSO4 Microspheres with a Larger Pore Size via Ostwald Ripening at Room Temperature

Mesoporous microspheres with a larger pore size (diameter of pore: ca. 35 nm, Barrett−Emmett−Teller (BET) surface area: 25.6 m 2 /g), the radial arrangement of irregular BaSO 4 nanorods, were successfully synthesized by the radiolysis of an aqueous solution of K 2 S 2 O 8, Ba(NO 3 ) 2, and disodium ethylenediaminetetraacetate with an irradiation time of 1000 min (dose rate: 20 Gy/min) at room temperature. It was confirmed that the mesoporous microspheres with a larger pore size evolved from the mesoporous microspheres with a smaller pore size (diameter of pore: ca. 4 nm, BET surface area: 49.6 m 2 /g), which were generated at the early stage of the irradiation course and were mainly constructed by quasi-spherical nanoparticles, via Ostwald ripening at room temperature.