Study On The Controlled Synthesis Of Spherical Magnesium Oxide

MgO,as an inorganic functional material,has a wide range of applications in many fields.Among them,MgO with spherical morphology has good application prospects in the fields of thermal conductivity,antibacterial,adsorption,catalysis,and liquid chromatography.Spherical magnesium oxide cannot be directly prepared.Generally,a precursor with a spherical morphology,Mg（OH）₂ or Mg₅（CO₃）₄（OH）₂·4H₂O,is prepared first,and a spherical morphology of MgO is obtained by calcining the precursor with a spherical morphology.At present,when Mg（OH）₂ is used as a precursor to prepare MgO,MgSO₄ is mainly used as the raw material;China has rich reserves of magnesium chloride.MgCl₂ is an inexpensive magnesium-containing raw material.The new process has very important economic significance and application prospects.Based on previous research work,this thesis studies the process of preparing spherical magnesium oxide using Mg（OH）₂ as a precursor.Using MgCl₂,NaOH and NH₃·H₂O as raw materials,the optimum experimental conditions of the ammonia gas diffusion method are explored by adding a suitable crystal form control agent,spherical magnesium hydroxide is prepared,and the prepared spherical Mg（OH）₂ is calcined at high temperature to obtain Spherical morphology MgO.The specific research content is:（1）Using MgCl₂,NaOH and NH₃·H₂O as raw materials,the precursor spherical magnesium hydroxide was synthesized by the method of gas phase diffusion by adding a crystal form control agent.In order to explore the best conditions of this gas-phase diffusion method,the control factors,dosage,reactant concentration and ratio,and reaction time were used as control factors to change the above factors,and the products obtained under different reaction conditions were subjected to XRD,SEM characterization and analysis.Through characterization analysis,it was found that under normal temperature and pressure,the control agent was polyvinylpyrrolidone,the addition amount was 1.0%dry weight of MgCl₂,the concentration of MgCl₂ was 1.0 mol/L,the concentration of NaOH was 0.25mol/L（the molar ratio of sodium is 4:1）,and the reaction time is 24h,the prepared spherical magnesium hydroxide particles are uniform in size,good in dispersibility,high in sphericity,and dense and compact spheres,which are the best synthesis conditions,And the yield of spherical magnesium hydroxide reached 77.8%.（2）Using the spherical Mg（OH）₂ obtained under the above optimal synthesis conditions,calcined at room temperature to 600℃for 2h at a heating rate of 10℃/min to obtain spherical magnesium oxide MgO.It was characterized by scanning electron microscopy,X-ray diffraction,specific surface and particle size analysis,which showed that the spherical MgO prepared by ammonia diffusion had a uniform particle size distribution,high sphericity,good dispersion,and an average particle size of 4.53μm.