Magnesium hydroxide flame retardant is colorless, non-toxic, odorless, non-corrosive and other properties, and is a green environmentally friendly polymer material additive. Magnesium hydroxide having a good flake or fibrous crystal shape can be better matched with raw materials without affecting physical properties such as strength of the raw material, and effectively improves the flexural strength and elongation of the polymer material. Therefore, magnesium hydroxide flame retardants with special morphology have more excellent properties and wider application.
As an important chemical product, magnesium hydroxide micro-nano materials have been widely used in ceramics, flame retardant, catalysis, medicine and environmental protection. The morphology, size and dispersibility of magnesium hydroxide micro/nano materials affect their application properties and therefore need to be regulated. Taking magnesium hydroxide as the research object, the morphology, size and dispersibility of magnesium hydroxide products were successfully controlled by controlling the synthesis conditions. An aluminum-magnesium composite coating was prepared by plasma spraying technique using this magnesium hydroxide powder as one of the starting materials.
(1) A process for preparing magnesium hydroxide micro-nano powder materials by ammonia diffusion method under room temperature conditions was designed. Under the guidance of S042-ion and additive PEG, magnesium hydroxide micro-nano particles can crystallize into spherical crystals with good morphology. The effects of reaction concentration, reaction time, solvent and additives on the final morphology of the globular product were investigated by different comparative experiments. By changing the type of additives, the average diameter of the globular crystals can be adjusted to suit the requirements of each specific application. Also using an ammonia gas diffusion system, by changing the kind of the magnesium salt reactant and the type of the additive, it is possible to obtain a magnesium hydroxide product different from the spherical morphology, that is, a sheet-like magnesium hydroxide having good dispersibility.
(2) Using the synthesized magnesium hydroxide product as raw material, the aluminum-magnesium composite ceramic coating was prepared on the surface of the Q235 steel substrate by plasma spraying equipment by using the difference in melting point between magnesium hydroxide and magnesium oxide. The phase composition and microstructure of the composite coatings were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The aluminum-magnesium composite ceramic coating is mainly composed of a-A1203.γ-A1203 and MgO. Magnesium hydroxide is used in the field of composite coatings, with better economic and social benefits and wider application prospects.