A facile route for the flowerlike Mg7B4O13 · 7H2O nanostuctures: Synthesis, growth mechanism and thermal treatment

Abstract In the presence of the surfactant poly(vinyl pyrrolidone) (PVP), 3D hierarchical flower-shaped Mg 7 B 4 O 13  · 7H 2 O nanostructures were synthesized via a facile precipitation process using Mg(NO 3 ) 2  · 6H 2 O and Na 2 B 4 O 7  · 10H 2 O as the raw materials. The nanostructures with diameters of 0.8–1.2 μm are composed of numerous polycrystalline nanosheets with thickness of about 10 nm. The possible growth mechanism for the flower-shaped nanostructures was proposed based on the systematic structural and property characterizations including XRD, SEM, TEM, IR and N 2 adsorption–desorption. The phase transformation can be observed during the calcination process, and the flower-shaped nanostructures can be successfully maintained after calcination at 550 °C and 650 °C. The adsorption–desorption experiments show the appearance of mesopores before and after calcination co-existed with small amount of macropores. The highest surface area of 111 m 2 /g and largest pore volume of 0.37 cm 3 /g are obtained in these hierarchical porous Mg 3 B 2 O 6 nanoflowers. These novel porous borate-based materials could be applied in drug delivery, catalysis, environmental abatement, energy storage, etc.