Size Effects in MgO Cube Dissolution

Abstract

Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution.

Optical and fluorescence properties of MgO nanoparticles in micellar solution of hydroxyethyl laurdimonium chloride

“…The XRD pattern of the synthesized MgO is shown in Figure 2a [20]. The crystallite size is determined using Scherrer's formula, d = 0.9 /ˇ cos Â, where d is the crystallite size, is wavelength of X-ray radiation, ˇ is full width at half maximum and  is the diffraction angle.…”

Deacidification of Acidic Books and Paper by Means of Non-aqueous Dispersions of Alkaline Particles: A Review Focusing on Completeness of the Reaction

“…Work by Sutcu et al (2009) showed that the (1 1 1) crystal face of MgO particles was most susceptible to hydration by exposure to water vapor and a relative humidity of 88% in the cited work. Research by Baumann et al (2015) has shown that the rate of dissolution of MgO particle increases with their decreasing size, and that dissolution takes place more slowly if a stable layer of Mg(OH)2 has formed on the particle surfaces.…”

Thin water films and magnesium hydroxide fiber growth

“…Furthermore, consistent with the crystallite domain size the particle sizes, as determined by TEM analysis, remain in the range below 10 nm. 19 Irrespective from the retained primary particle properties, the agglomerates have become more compact (upper micrographs of Fig. 5a and b) in comparison to MgO nanocube powders before functionalization (Fig.…”

“…Subsequently, the temperature is raised to 1173 K and, at pressures of p < 5 Â 10 À6 mbar, kept at this temperature for 1 h before cooling to room temperature. 19 As revealed by Transmission Electron Microscopy CVS MgO consists of highly dispersed monocrystalline nanocubes with a high portion of edge and corner features (Fig. S1a, ESI †).…”

“…(A detailed microstructural and morphological description of these hydroxides can be found in ref. 19.) A completely new microstructural situation, however, originates from water contact of chlorosiloxane covered MgO nanocube agglomerates for exposure times t $ 3 days 24 (lower panel in Fig.…”