The applications of Magnesium hydroxide nanomaterials in water treatment, flue gas desulfurization, paper preservation and solar cells have led to extensive research by materials researchers. Especially in the field of polymer flame retardants, Magnesium hydroxide are non-toxic, non-harmful, acid-resistant and thermodynamically stable. These applications are derived from the physical chemistry properties of Magnesium hydroxide crystals, which are determined by their morphology, size and dispersion. Because of its special structure, mechanical properties and dispersion, Magnesium hydroxide crystals with lamellar structure have the functions of both filling and halogen-free flame retardancy in thermoplastic polymers and fiber materials, and can increase the starting temperature of polymer combustion, increased thermal stability. Therefore, flaky Magnesium hydroxide crystal flame retardants have become a research hotspot, and the preparation of flaky Magnesium hydroxide is one of the most promising directions in the preparation of high-quality flame retardants.
In this thesis, we systematically studied the preparation of inorganic functional Magnesium hydroxide nanocrystalline materials using hydrothermal control techniques, the high crystallinity and regular hexagonal Magnesium hydroxide crystals were synthesized by the reaction of polyoxometalates. The glucose and potassium oxalate used contain multiple reactive oxygen species. Among them, glucose titrimetric precipitation stage, as a complexing agent, potassium oxalate in the hydrothermal treatment stage, as a structural modification. The average particle size of the Magnesium hydroxide crystals can be controlled by the type and concentration of the base used. The process of one-step hydrothermal synthesis of highly dispersed Magnesium hydroxide was designed. In hydrothermal system, potassium oxalate controls the growth of C axis and modifies the surface of Magnesium hydroxide crystals, while high concentration of sodium nitrate increases the chemical potential of the system and promotes the reaction, at the same time, it was found that sodium nitrate had a strong regulatory effect on morphology. With the increase of reaction time, the hexagonal Magnesium hydroxide changed into a round cake-like structure. Using the same ion principle, magnesium acetate was used as magnesium salt, and sodium acetate with the same anion was used in the titrimetric precipitation stage to affect the nucleation and growth of Magnesium hydroxide; Lamellar Magnesium hydroxide crystals were prepared by hydrothermal treatment of magnesium chloride solution with the same cationic Magnesium hydroxide.
The effects of other hydrothermal solvents, including ammonium acetate, water, ethanol, acetone, cetyltrimethylammonium bromide and Sodium lauryl sulfate, on the crystallinity and crystalline morphology of Magnesium hydroxide were also investigated. The experimental results show that ammonium acetate solution with different concentrations as hydrothermal modifier can mediate the hydrothermal dissolution-recrystallization process.