The Influences Of Oxygen Content On The Structure And Properties Of Non Oxide Ceramics

In recent years,non-oxide ceramics have been widely used in gold chemical industry,mechanical seals,heating elements and many other fields.In particular,Al N,B₄C and Si C have broad application prospects in strategic emerging industries such as integrated circuits,aviation,aerospace,and national defense.In order to carry out in-depth research and application of it,the research on various powder preparation and ceramic preparation is also developing rapidly.There will be a small amount of impurity oxygen in the preparation process of ceramic powder,which may affect the sintering and properties of the material.In this paper,three typical non-oxide ceramics（Al N,B₄C,Si C）were selected to study the effect of oxygen content on their structure and properties.1.Use a muffle furnace to heat-treat the ceramic powder at different temperatures or times to obtain Si C powder samples with different oxygen contents.Silicon carbide ceramics were sintered at 2050℃with Al N and Zr B₂as sintering aids by pressureless sintering method.The densification mechanism and properties of the ceramics were studied by XRD,SEM,EDS,XPS,FT-IR and other characterization methods.The results show that the oxygen content affects the phase composition,grain boundaries and densification of Si C.In addition,the interaction between oxygen defects and aluminum nitride plays an important role in the sintering process.In addition,the physical properties of the densified Si C samples were characterized by nanoindentation,AC impedance and thermal conductivity tests to study the effect of oxygen content on the mechanical,electrical and thermal properties of the densified Si C ceramics.The results show that the oxygen content has an important effect on the mechanical,electrical and thermal properties of Si C ceramics.The study further found that the influence trends of oxygen content on the structure and properties of densified Si C were similar.2.Boron carbide ceramics with different oxygen contents were prepared by sintering in a pressureless sintering furnace at 2150℃with Si-Al binary additive as flux.The structure of boron carbide was analyzed by EDS,SEM,XRD and other means.The research results show that the Si-Al flux has a lower melting point and promotes ceramic densification through liquid phase sintering.Further structural analysis,the influence of B₂O₃impurity on the sintering process and grain growth was discussed.The test results based on Vickers hardness and nanoindentation show that the mechanical properties of boron carbide ceramics deteriorate due to increasing oxygen content.3.Analyze the high temperature oxidation mechanism of aluminum nitride powder,and control to obtain aluminum nitride powder with different oxygen content.Aluminum nitride ceramics were prepared by sintering at 1900℃with Ca F₂as sintering aid.The ceramic structure was analyzed by SEM,XRD,EDS and XPS,and the liquid phase sintering mechanism of Al N ceramics and the influence of oxygen impurities on sintering and structure were discussed.The properties of a series of aluminum nitride ceramics were analyzed by Vickers indentation,dielectric property testing and thermal diffusivity testing.It was found that with the increase of oxygen content,the mechanical properties,electrical properties and thermal properties of the ceramics gradually deteriorated.