Nanocrystals to Nanorods:  A Precursor Approach for the Synthesis of Magnesium Hydroxide Nanorods from Magnesium Oxychloride Nanorods Starting from Nanocrystalline Magnesium Oxide

Abstract

Nanorods of magnesium oxychloride (Mg x (OH) y Cl z ·nH2O) and magnesium hydroxide (Mg(OH)2) have been produced from crystalline MgO. Concentrated aqueous magnesium chloride (MgCl2·6H2O), when allowed to react with MgO, yields oxychloride nanorods that can be converted into Mg(OH)2 nanorods using NaOH, with retention of the nanorod morphologies. A comparison of powdered MgO starting materials has shown that, by proper choice of reagent concentrations, temperature, and aging time, nanorods can be obtained in all cases, but nanocrystalline (NC)−MgO gives the highest yields and the highest aspect ratios (aspect ratios of about 60−90 in the oxychloride system). The higher surface area and higher reactivity of NC−MgO allow the rapid formation of nucleation sites in large numbers that subsequently grow into thin (∼170 nm) oxychloride nanorods. The nanorods of Mg x (OH) y Cl z ·nH2O and Mg(OH)2 were characterized by powder X-ray diffraction and transmission electron microscopy measurements.

Synthesis of magnesium oxide particles with stacks of plates morphology

“…It was not possible to get the FE-SEM images for the magnesium oxychloride gel since it was found to decompose on drying to yield hygroscopic magnesium chloride. However, it is known from literature [23] that magnesium oxychloride possesses rod-like morphology and it is proposed that such morphology exists for the magnesium oxychloride gel prepared in the present study. The gel which consists of rods, on reaction with ammonium oxalate, produces magnesium oxalate dihydrate with stacks of plates morphology.…”

“…The gel is known to be made up of magnesium oxychloride [23]. For the preparation of magnesium oxalate dihydrate, about 5 ml of the gel was added into about 100 ml of 0.1 M ammonium oxalate aqueous solution and the contents were kept for 24 h for equilibrium at room temperature.…”

“…Various synthetic methods such as chemical vapor deposition, template synthesis, precursor decomposition, ion-sputtering, homogeneous precipitation, sol-gel processing, precipitation pyrolysis, epitaxial growth and melt synthesis have been developed for the controlled synthesis of MgO particles [13][14][15][16][17][18][19][20]. The commonly observed morphologies of magnesium oxide include cubes [17], whiskers/fibers [20], nanosheets/nanoplates/nanoflakes [21], flower-like [22], nanorods [23], nanotubes/microtubes [24,25], spheres [26], nanobelt [27], lamella-like [28], corraline [29], rectangular parallelepiped [30], rectangular sheets [31], tubular tetrapod [32], and columnar structure [33]. In the present study, magnesium oxide with a unique morphology of stacks of plates has been synthesized using a precursor approach and to the best of authors' knowledge, this is the first time such a morphology is reported.…”

Novel surfactant-free synthesis of MgO nanoflakes

“…A detailed study for the synthesis of magnesium hydroxide nanorods starting from MgO has been carried out by Jeevanandam et al, wherein the conversion of compounds have been explained [28]. Comparing with those methods using MgCl 2 as precursor or using a mixture of MgO powder and carbon powder as starting materials, Mg is the only reactant in this technique, which is more direct and easy.…”

Facile preparation and application of magnesium hydroxide assembly spheres

“…In recent years, Mg(OH) 2 with different morphology has been successfully synthesized by different approaches or by use of different preparation conditions, e.g. hydrothermal [9], ultrasound-assisted [10], and direct synthesis [11,12], by in-situ preparation [13], in water-in-oil microemulsions [14], and by the spinning disk reactor method [15], etc [16][17][18]. Among the products obtained, assembly spheres with very large surface area have become the focus of much interest, because of their good suspension properties and high surface activity [19,20].…”