Synthesis of barium hexaferrite nano-platelets for ethylene glycol ferrofluids

Abstract

Recently discovered barium hexaferrite (BaFe₁₂O₁₉)-based nanoplatelets form a ferromagnetic–ferrofluid which exhibits interesting magnetic properties. Manufacturing the barium hexaferrite nano-platelets via hydrothermal synthesis remains of fundamental interest and allows for optimisation of structural, magnetic, and morphological properties, which impact on ferrofluid properties. This report describes a surfactant assisted manufacturing method for an ethylene glycol based ferrofluid using hexadecyltrimethylammonium bromide (CTAB) with barium hexaferrite nano-platelets. A hexagonal nano-platelet morphology with a typical diameter up to 200 nm and thickness of a few nanometres was observed by transmission electron microscopy (TEM) with stable concentrations between 10–200 mg ml⁻¹, while saturation magnetisation of dry particles was measured at 32.8 A m² kg⁻¹ using a vibrating sample magnetometer (VSM). The manufactured barium hexaferrite–ethylene glycol ferrofluid exhibits improved thermal properties compared to previously used butanol based ferrofluids, opening the way into new applications in the field of colloidal suspensions.