As an important chemical product, magnesium hydroxide nanomaterials have been widely used in ceramics, flame retardant, catalytic, pharmaceutical and environmental protection fields. The morphology, size and dispersion of MgOH micro- and nanomaterials affect their application properties, so they need to be controlled.
In this paper, the morphology, size and dispersion of magnesium hydroxide products were successfully controlled by regulating the synthesis conditions. The aluminum-magnesium composite coating was prepared by plasma spraying technique with this magnesium hydroxide powder as one of the starting materials.
(1) A process was designed for the preparation of magnesium hydroxide micro- and nano-powder materials by ammonia diffusion method under room temperature conditions. Under the guidance of S042- ions and additive PEG, the magnesium hydroxide micro-nanoparticles could crystallize into well-shaped spherical crystals. The effects of reaction concentration, reaction time, solvent and additives on the final morphology of the spherical products were investigated by different comparative tests. The average diameter of the spherical crystals can be adjusted by varying the additive type to suit the specific application requirements. By changing the type of magnesium salt reactant and the type of additive in the same ammonia diffusion system, it is possible to obtain magnesium hydroxide products with different spherical morphology, i.e. flakes of magnesium hydroxide with good dispersion.
(2) Using the synthesized magnesium hydroxide product as raw material, the aluminum-magnesium composite ceramic coating was prepared on the surface of Q235 steel substrate by plasma spraying equipment using the melting point difference between magnesium hydroxide and magnesium oxide. The phase composition and microstructure of the composite coating were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The Al-Mg composite ceramic coatings are mainly composed of a-A1203.γ-A1203 and MgO, and the magnesium hydroxide is applied in the field of composite coatings with better economic benefits.