Effect Of Initial Powder On Crystal Structure And Properties Of Sintered Alumina

The instability of raw materials has always been a major cause of instability in the use of products and various major industrial safety accidents,and researchers in the field of materials have been working to solve this major scientific problem.Sintered alumina is a commonly used refractory raw material in the high-temperature industry,especially in the field of refractory materials.Sintered alumina was formally investigated in China in the 1990s and certain research results were achieved.However,with the gradual upgrading of product standards and the gradual expansion of the sintered alumina industry in recent years,problems in the practical application process have come to the fore.In the process of comparing similar products,sintered alumina products from different sources show different property indicators,which significantly affect the service life of refractory products and increases the economic burden of enterprises.Therefore,as an important basic material in the field of refractories,it is of great significance to study and discuss the reasons for the differentiated performance of sintered alumina and to realise its stable application in the field of refractories for the industrial progress and economic development of the industry.In this paper,sintered alumina specimens were prepared at different temperatures using four different commercial alumina powders as raw materials and simulating the production process of sintered alumina.The physical composition of the specimens was determined using an X’Pert Pro X-ray diffractometer;the chemical composition of the specimens was analysed using an IRIS Advantage Radial inductively coupled plasma emission spectrometer;the particle size distribution of the powders was measured using a Mastersizer 2000 laser particle size analyser;the specific surface area of the powders was measured with an Auto Sorb-1 nitrogen adsorption analyser;the pore size distribution of the samples was measured with an Auto Pore IV 9500mercury piezometer;the microstructure of the specimens was observed with a JSM-6610 scanning electron microscope;and the erosion resistance of the specimens was thermodynamically simulated with Fact Sage 6.2 thermodynamic software.The main factors influencing the properties and microstructure of commercially available mainstream sintered alumina products were investigated,the mechanisms of action of the influencing factors were analysed and their effects on the property of the refractory products were discussed,with emphasis on the evaluation of the role of microstructure in the resistance to slag erosion.The following meaningful conclusions are drawn.1.Through tests and calculations on the chemical composition,particle size,specific surface area,microscopic morphology,physical composition,and sintering activation energy of four commercially available commercial alumina powders,it is found that the main characteristic differences between the current commercially available commercial alumina powders are microscopic morphology and physical composition.2.The sintering mechanism and sintering kinetic model of the pseudomorphic powders of commercial alumina powders are different from those of near-spherical powders,which affects the physical properties and microstructure of sintered alumina;With similar corundum content,γ-Al₂O₃ has a higher densification potential than other transitional alumina phases,resulting in better physical properties and larger grain size of sintered alumina.The presence of Na₂O in the pseudomorphic powder form enhances its application potential in porous materials;As an additive in the preparation of sintered alumina,single physical doping has no positive effect on the sintering property of AlF₃;Hydration pretreatment of the commercial alumina powder containing theγ-Al₂O₃ phase helps to achieve the sintering performance.3.The application of sintered alumina in Al₂O₃-SiC-C trough castables shows that:the density of sintered alumina aggregate affects the mechanical properties of products after firing;the pseudomorphic structure in the commercial alumina powder leads to the formation of porous clusters within the sintered alumina aggregate,thus improving the thermal shock resistance of the product.From the thermodynamic point of view,a medium number of pore clusters and a smaller grain size lead to a thicker and more complete spinel structure attached to the pore walls,which improves the erosion resistance of the material.From the kinetic point of view,the rounded pore structure and larger grain size make the material have lower dissolution rate and better corrosion resistance.Therefore,the selection of aggregate under erosion environment needs to be considered in combination with the leading role of actual erosion behavior.4.Through immersion erosion experiments of sintered alumina in different slag systems and different basicity environments,it is found that"MgO-Al₂O₃ spinel layer","MgO-Al₂O₃ spinel,and CA₆ composite layer"and"CA₂ and CA₆ composite layer"have slower dissolution rate than direct dissolution of alumina in the process of slag renewal and reaction to resist slag erosion.The difference of microstructure characteristics of sintered alumina aggregate has a certain influence on the anti-erosion behavior of aggregate in the process of slag erosion resistance.In the simulated erosion environment of blast furnace slag/refining ladle slag with low basicity,the microstructure characteristics of moderate dissolution activity are beneficial to the formation of thicker isolation layer size or more effective isolation layer morphology,thus having better anti-erosion effect;In the simulated erosion environment of blast furnace slag/refining ladle slag with high basicity,the microstructure characteristics of low dissolution activity are beneficial to the formation of thicker and more stable isolation layer size,thus having better anti-erosion effect.