Additives Applied for Preparation of Superfine Mg(OH)2 Particles by Light-Burned MgO at Low Temperature

Due to its buffer property, activity, absorbability and safety, magnesium hydroxide is widely used in environmental protection, pharmaceutics, pulp and paper industry, and as flame-retardant filling in composite materials. The hydrothermal synthesis of magnesium hydroxide at low temperature (< 100?) needs only simple equipment and is environmentally friendly and energy-saving, so the process is promising and easy for industrialization. In this study, we have investigated the effects of hexamethylenetetramine and ammonia additives on the hydrating synthesis of superfine Mg (OH)₂ particles at 70?. Mg (OH)₂ particles formed were of platelet shape and the mean diameter was approximately 200nm. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to characterize the crystal phase, size distribution and morphology of the crystal particles. Different morphologies of Mg (OH)₂ particles were formed in hexamethylenetetramine and ammonia solutions. The generation velocity of hydroxyl (OH^-) was found to play an important role in the distribution and morphology of Mg (OH)₂ particles.