Synthesis and mechanism of a new environment-friendly flame retardant (anhydrous magnesium carbonate) by hydrothermal method

In this study, the synthesis and formation mechanism of anhydrous magnesium carbonate (AMC) using hydrothermal method is proposed from the perspective of ionic reaction. Validation experiments were conducted, and the effect of the pH of the reaction solution and the form of carbon source on AMC preparation was investigated. It is found that HCO3− can accelerate crystal growth and reduce crystal size, and the preparation conditions of AMC can be quantified. The AMC particles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The AMC prepared using urea as carbon source has a small particle size in the presence of ion pairs of Na+/Cl− or K+/SO42−. AMC prepared using magnesium chloride as magnesium source has smaller composition units than those prepared using magnesium sulfate as magnesium source. The effects of ions types, reaction temperature, reaction time and filling degree on the phase transition and crystal growth of AMC are also discussed.