LAUSR

Abstract Surface enthalpy for magnesium gallate, MgGa 2 O 4 spinel, was directly measured using water adsorption microcalorimetry. The method relies on the Gibbs adsorption theory, using the heat involved when water molecules are adsorbed on the surface of the oxide to derive accurate surface enthalpy data. For this method to be efficient, high amounts of surfaces need to be probe, requiring the usage of nanoparticles. Therefore, in this study we initially propose a new method to synthesize MgGa 2 O 4 nanoparticles by controlling the pH of the precipitating solution during co-precipitation of Mg,Ga hydroxides, followed by calcination. The nanoparticles showed the spinel phase and were characterized in terms of composition before subjected to calorimetry. The surface energy of the studied MgGa 2 O 4 nanoparticles was found to be 1.44 ± 0.1 J/m 2 , consistently with surface energy data reported for other spinels.