Low-temperature synthesis of Magnesium aluminate spinel nanopowders using Mg and Al with glycine complex precursor

Abstract

Creation of optically transparent materials that are characterized by high durability, hardness and impact viscosity is one of the most urgent tasks of modern material science. Magnesium aluminate spinel is one  such compound that corresponds these requirements. A new technology of low-temperature synthesis of spinel nanocrystalline powders using a precursor based on glycine was proposed.

By means of glycine-nitrate method was obtained of precursor xerogel (pH = 5.5) for the synthesis of magnesium aluminate spinel powder. Pyrolysis of xerogel Mg: Al: glycine at t° = 240 °C followed by heat treatment (600 °C, 650 °C, 700 °C) of the obtained MgO-Al2O3-C composite particles (with and without pre-milling) was carried out. As a result of synthesis, nanopowders MgAl2O4 were obtained.

The method of XRD in samples of synthesized powders established the presence of one cubic phase (Fd-3m)

of aluminate spinel without impurities. A static adsorption-structural method based on the interpretation of isotherms of adsorption determined the specific surface of samples of powders. It has been shown that the most developed surface (SBET = 170 m2/g) and the smallest particle size (7 nm) have spinel powders obtained at 700 °C without pre-milling of the MgO-Al2O3-C precursor. From the results of studies of nanopowders by the method of transmission electron microscopy (TEM) it follows that the samples are strongly agglomerated, each part connected with adjacent contact isthmus. In general, the particles form a porous structure with an average pore diameter of 400-500 nm. The average size of nanoparticles is 5 - 10 nm. The polycrystalline phase at 700 °C was noted.