Preparation And Properties Simulation Of SpHerical Alumina Powder

Aluminium oxide has many properties that make it useful in a variety of industrial applications,where the requirements for powder materials are closely related to the shape and size of the product.SpHerical alumina is one of the many forms of alumina that play a vital role in the field of inorganic powders.As an inorganic powder material,spHerical alumina has a broader future in chemical applications.Therefore,the preparation of alumina powders with small average particle size,uniform product particles and good spHerical morpHology is of great research significance.In this thesis,spHerical alumina powders were prepared by three methods:sol-gel-spray drying,hydrothermal method and ball-mill-radio frequency plasma method.The relevant properties ofα-Al₂O₃ were also simulated and the differences between precursors in terms of energy band and density of states,Bourget analysis,refractive index,reflectivity and complex dielectric function were analysed and studied.The experiments and the results of the study are as follows:SpHerical alumina precursors were prepared using the sol-gel-spray drying method with Al（NO₃）₃·9H₂O as the raw material and ammonia as the precipitant,and the effect of different calcination temperatures of the precursors on the products was investigated.It was found that when the concentration of the raw material did not exceed 0.2 mol/l,the reaction time was 2h,the dispersant was sodium dodecyl sulfate,and then the reaction temperature was increased to 80℃,the solution pH value was 8.8,and the ammonia dropping dosage was 50 ml,the alumina precursors were better dispersed,and when the precursor products were calcined,it was found that there was basically no change in the morpHology of the products after the calcination temperature.Al₂（SO₄）₃·18H₂O was used as the raw material and sodium hydroxide was chosen as the precursor for the precursor of the alumina product using the hydrothermal method.The investigation revealed that when the ratio of raw material to precipitant was 1:2,the hydrothermal time was 4h and the hydrothermal temperature was 120℃-140℃ the precursor of the product particles made,with the increase of the solution pH NaAlO₂·1.25 H₂O began to transform into Na₉[Al（OH）₆]₂（OH）₃·6H₂O.after calcination,the spHericity of the alumina powder particles prepared by the hydrothermal method was poor and the product had an irregular lumpy morpHology.Using industrial grade alumina as raw material,alumina powders with high spHericity and average particle size between 1-100μm were prepared by combining the traditional ball milling method with the popular RF plasma method in recent years.It is known that when the ratio of raw material to agate balls is 1:7,the ball mill is running at 600 r/min and the ball milling time is 90 min,then the ball milling product is spHeroidised by the RF plasma equipment,it is known that at a feed rate of 2 g/min,an internal gas flow rate of 1-2 L/min and a system pressure of 95 kPa,a more complete crystalline alumina powder with a higher spHericity can be prepared.The powdered alumina can be prepared with a more complete crystalline form and higher spHericity at a feeding rate of 2 g/min,an internal gas flow rate of2-2 L/min and a system pressure of 95 kPa.In the preparation of alumina powders,different types of alumina precursors are prepared,and the properties of the different precursors can vary.The order of stability of the crystal microstructures of the different alumina precursors can be reflected by exploring different aspects such as energy bands,density of states and bonding residence:β₁-Al（OH）₃<β₂-Al（OH）₃<α-AlO（OH）<γ-AlO（OH）;and the order of pHotosensitivity by optical properties:α-AlO（OH）<β₂-Al（OH）₃<β₁-Al（OH）₃<γ-AlO（OH）.