Preparation Of Ultrafine MgO Powder And Its Suspension Properties

The preparation of ultrafine powder materials is a dominant part of the current research in ultrafine materials science,and the new development and control of the process has an extremely important influence on the microstructure and macroscopic properties of ultrafine powder materials.Among them,ultrafine Mg O powder as a new and highly functional fine inorganic materials,with high purity,large specific surface area,non-toxic and odourless,good dispersion and suspension properties,easy to use,high hardness,high purity and high melting point and other excellent characteristics,while ultrafine Mg O light transmission,insulation properties and antibacterial properties also benefit from other inorganic materials.The suspension properties of ultrafine Mg O are often used in ceramics,catalysis,coatings and paper making.Therefore,the preparation of ultrafine Mg O powders with excellent suspension properties has been a major research direction in recent years.In this paper,the properties,applications and current status of ultrafine Mg O are introduced,its preparation methods are analysed,a modified direct precipitation method is proposed for the preparation of ultrafine Mg O,and the influencing factors for the preparation of ultrafine Mg O powders are investigated,and the dispersion stability of ultrafine Mg O suspensions under water,acid and alkali systems is discussed.In this study,magnesite was used as raw material,and lightly burned Mg O was obtained by high-temperature calcination in a box-type resistance furnace.Magnesium chloride solution was prepared by adding hydrochloric acid dropwise,and then the ultrafine Mg O powder was prepared by liquid-phase precipitation method with ammonia as precipitant and ethanol and water as solvent system.Ultra-fine Mg O powder particles with narrow particle size distribution,homogeneous particle size and less agglomeration were obtained.Based on the preliminary preparation experiments,the factors influencing the formation and particle size of ultrafine magnesium oxide were analysed,and seven influencing factors were determined: solvent ratio,surfactant type and concentration,ammonia drop acceleration rate,stirring time,stirring speed,reaction temperature and calcination temperature.It was proved by means of particle size analyzer,XRD,TGDTA that the deionized water to ethanol ratio was 2 : 1,10% polyvinyl alcohol was added as surfactant,the ammonia drop acceleration rate was 0.5m L/min,the magnetic stirring speed was 1500 m L/min,the reaction temperature was 70℃,the calcination temperature was 600℃,the Mg O particles had a more regular shape,the particles were more dispersed and the particle size was smaller.more dispersed,the particle size is smaller.Since ultrafine particles are very prone to agglomeration and secondary particle formation,their suspension properties can be studied by a combination of physical and chemical methods.The surface properties,wettability and interfacial compatibility of the ultrafine Mg O are improved by the addition of appropriate surfactants during mechanical stirring,so that it is uniformly dispersed in water,acid and alkali systems.The paper analyses the dispersion stability of ultrafine Mg O powders in different systems and investigates the effects of dispersant type,dispersant dosage,p H,Mg O powder volume,stirring time and phosphoric acid and sodium hydroxide concentrations on the stability of the suspensions.By UV spectrophotometer,Fourier infrared spectrometer,particle size analyzer and zeta potential meter,we obtained that in the water system,the mass fraction ratio of sodium pyrophosphate to Mg O solid content was 1.5 : 22,the p H value of the system was 3 or 9 and the stirring was 10 h,a more stable suspension system could be formed;under the acidic environment,the mass fraction ratio of ultrafine Mg O powder,phosphoric acid and sodium pyrophosphate was18 : 3 : 2;under alkaline conditions,the ratio of the mass fraction of ultrafine Mg O powder,sodium hydroxide and sodium pyrophosphate is 18 : 0.02 : 2,which can achieve the dispersion stability of ultrafine MgO suspension.