Preparation And Characterization Of High Dispersion Hexagonal Magnesium Hydroxide

In the contemporary world,the development of science and technology lies in innovation.Novel materials research has gradually developed into an important scientific field.Nano-magnesium hydroxide is a kind of high-functional fine inorganic material.It not only has the properties of common magnesium hydroxide,but also possesses the properties of light,heat,electricity and magnetism due to its surface effect,volume effect,quantum size and macroscopic quantum tunneling effect,Mechanical and chemical properties,so the nano-magnesium hydroxide is widely used in antimicrobial,catalysis,adsorption and inorganic flame retardants and other fields,which is the focus of inorganic materials and hot spots.In this paper,hexagonal flake magnesium hydroxide with good flame retardancy was prepared by three different chemical processes.The first chemical process is mainly the use of magnesia hydration hydrothermal two-step preparation,.At first,the hydration method is the preparation of magnesium hydroxide hydrothermal precursor.That is,the raw material magnesium oxide hydrate in the sodium hydroxide as a catalyst environment,then add a certain concentration of a weak base such as sodium acetate,sodium citrate,synthesis of magnesium hydroxide hydrothermal treatment.We have found hydrothermal high temperature and pressure can increase the solubility of magnesium hydroxide.After a long time dissolution-crystallization process,second precipitated nano-magnesium hydroxide particles hexagonal has more regular morphology,small surface polarity,good dispersion,small particle size,which is in line with the requirements of flame-retardant magnesium hydroxide.In addition,the effects of different surfactants on the grain size and crystal growth behavior of nano-MgO were investigated.We found that after the addition of the surfactant,hexagonal platelets were found to be more regular and the dispersibility was significantly improved.Different types of surfactants,the amount of different morphologies have varying degrees of impact.Different surfactants have different mechanism of action.Through comparison,we find that PVP has the best molecular effect because of its dual function,which has steric hindrance and coordination with magnesium ions.The second process is mainly the use of magnesia hydration hydrothermal two-step preparation of hexagonal sheet-like nano-magnesium hydroxide,The first chemical process is mainly the use of magnesia hydration hydrothermal two-step preparation,.At first,the hydration method is the preparation of magnesium hydroxide hydrothermal precursor,then adding a certain concentration of organic medium.The effect of adding organic solvent to the pressure of the system is very obvious,and the pressure of the system has an obvious effect on the chemical reaction speed.In this system,a variety of organic solvents play a regulatory system pressure to regulate the reaction rate,but also because the organic solvent is more viscous,but also affect the speed of ions involved in the reaction rate of the system,thus controlling the reaction time.Amine and alcohol amines have the ability of complexing with Mg²⁺and can promote the continuous dissolution of Mg?OH?₂ during hydrothermal treatment.The better the dissolution,the higher the crystallinity of the resulting crystals.The basic size of the organic solvent-water mixed solution,A certain concentration of OH-promoted the formation of Mg?OH?₆^4-,which is the basic unit of Mg?OH?₂.The polarity of the solvent was different.The two reasons can work together to increase the degree of crystallinity of magnesium hydroxide,the crystal morphology tends to rule.The third process which calcined the hexagonal plate-shaped magnesium hydroxide prepared in the first process and calcined the prepared hexagonal plate-shaped magnesium hydroxide investigate the effect of different calcining time and calcining temperature on the product magnesia grains Diameter and morphology of the calcined magnesium oxide will be hydrated to explore whether the different time and temperature magnesium oxide can be directly converted into hexagonal sheet of magnesium hydroxide.We conclude that as the calcination temperature increases,the grain size gradually increases,but the growth rate is different.When the temperature is increased from 650?to 750?,the grain size of magnesium oxide changes from the previous slow increase to significant increase.Calcination time is short,the decomposition is incomplete,However if time is too long,will form a dead burned and lost the activity of magnesium oxide,whith can not be rehydrated to hexagonal sheet of magnesium hydroxide.Therefore,to select a suitable calcination temperature,suitable time is key important,.We have found the calcination temperature of 550?and the time of 6h are the most conducive to a step into hexagonal magnesium hydroxide.