The Study On Preparation And Properties Of Alumina/Silicon Nitride Advanced Ceramic Materials

Alumina ceramic and silicon nitride ceramic are important components of advanced ceramic materials.Alumina ceramic has excellent optical properties,high temperature resistance and corrosion resistance,and alumina ceramic has been widely used in technical and environmental demanding fields such as military industry.With the development of technologies,thermal management plays an important role in the development of electronic power equipment.Silicon nitride ceramic has both reliable mechanical properties and excellent thermal conductivity.Therefore,silicon nitride ceramic will be applied to high-power circuit substrates,which is of great significance for solving the heat dissipation problem of high integrated circuits.This paper focuses on the preparation and performance research of silicon nitride and alumina advanced ceramic materials.The preparation of samples by various methods is used to obtain silicon nitride and alumina advanced ceramic materials with excellent performance and stable structure.The detailed research work and results are as follows:1.The Study on the Conversion of Alumina Polycrystal to Single Crystal by Spark Plasma Sintering TechnologyA solution containing calcium ions and silicon ions is prepared by sol-gel method using tetraethyl orthosilicate and calcium nitrate tetrahydrate.The solution of calcium ions and silicon ions is spin-coated on the surface of the alumina ceramic to form spin coating film.The precursor of tetraethyl orthosilicate and calcium nitrate tetrahydrate were used to control the content of silicon ions and calcium ions in the finally prepared solution.The influence of the amount of silicon ions and calcium ions on the grain boundary diffusion of the film was studied.The driving force and interface energy required for the movement of the ceramic grain boundary was also studied.With the increasing of the sintering temperature,it was to explore the effects on grain growth and grain boundary migration and the factors affecting grain boundary migration.2.The Study on Transformation of Alumina Polycrystalline to Single Crystal by Vacuum Tungsten FurnaceCalcium oxide and silica oxide are added to the deionized water to prepare a solution of calcium ions and silicon ions.The solution was used to drop to the surface of the high-purity alumina powder.A piece of single crystal and alumina powders were molded by manual press and cold isostatic press.The alumina powders were processed into green body and sintered in vacuum tungsten furnace.It was studied the effect of calcium ion and silicon ion content on the transition of polycrystal to single crystal.It was also studied the effect of prolonging the sintering time on the growth of single crystal and the interfacial energy.Grain boundary migration was researched systematically between spark plasma sintering technology and vacuum tungsten furnace.3.The Study on Preparation and Mechanical Properties of High Thermal Conductivity Silicon Nitride CeramicsTwo different powders?Powder A and Powder B?contain different powder characteristics,such as particle sizes,particle morphology,particle size,impurity and oxygen content.They were used as oxide sintering aids,such as Y₂O₃ and MgO.MgSiN₂ was used as non-oxide sintering aids.The difference between the thermal conductivity and mechanical properties?bending strength,fracture toughness,vickers hardness?of the two powders were compared.The oxygen content of the powder is an important factor which affect the thermal conductivity greatly.The oxygen content will cause vacancies of silicon ion which will cause the phonon diffusion and reduce the thermal conductivity.The non-oxide sintering aid MgSiN₂ can promote the compactness of the sample and promote transition of?phase to beta phase increasing the thermal conductivity.