Preparation And Performance Study Of SiC Ceramics Of Camellia Oleifera Shell-based

Silicon carbide ceramics have excellent high-temperature mechanical properties and are used in a wide range of applications.However,in the preparation process,it is difficult to sinter densification due to its strong covalent bonding compound and low diffusion coefficient,which leads to high cost.With its unique pore structure,biomass-based SiC ceramics can reduce the sintering temperature required for preparation and reduce production costs.Biomass-based SiC ceramics not only have the unique microstructure of the raw material itself,but also have the excellent properties of traditional silicon carbide,such as good oxidation resistance,high permeability,and excellent mechanical strength,and their raw materials are widely sourced,renewable,and low-pollution,which have broad application prospects in automotive exhaust gas filtration,semiconductor materials,bulletproof materials,and catalyst carriers.Camellia is an important cash crop in China,and in order to solve the environmental problems caused by its processing residues,biomassbased SiC ceramics are prepared from camellia oleifera shells.In this paper,SiC ceramics of camellia oleifera shell-based were prepared by warm press molding and reactive sintering processes using different mixing ratio schemes with camellia oleifera shells as the biomass template.The effect of the mass ratio of camellia oleifera shell powder:phenolic resin:silicon on the structure,components and properties of the ceramics was investigated.The relationship between the forming process and sintering process and the properties of SiC ceramics was analyzed.The optimal combination of parameters for the temperature and pressure forming process of SiC ceramics was investigated by response surface testing.The main work and innovations accomplished are as follows:(1)By studying the proportioning scheme between camellia oleifera shell powder,phenolic resin and silicon powder,it was found that:with the increase of Si content,the Si diffraction peak in the ceramics gradually enhanced,while the graphite diffraction peak gradually weakened to disappear;the porosity and compressive strength of SiC ceramics both showed a trend of increasing and then decreasing with the increase of Si powder;the pore structure of SiC ceramics of camellia oleifera shell-based was well-developed,with uniform pore size distribution and regular shape,and when the mass ratio of silicon powder:camellia oleifera shell powder:phenolic resin was 3:2:2,the overall microscopic morphology of SiC ceramics was clearer and more regular,and its main crystalline phase was β-SiC.(2)The effects of forming temperature,forming pressure and holding pressure time on the porosity,density,compressive strength and elastic modulus of SiC ceramics of camellia oleifera shell-based were investigated by single-factor tests.The results showed that when the forming temperature was 160℃,the mechanical properties of the ceramics had the maximum value,the compressive strength was 27.7 MPa and the elastic modulus was 6.27 GPa;the density and porosity were 1.07 g/cm3 and 58%,respectively;the porosity of the SiC ceramics of camellia oleifera shell-based showed an obvious decreasing trend with the increase of forming pressure,the density of the ceramics gradually increased,the compressive strength and elastic modulus When the forming pressure was 50 MPa,the compressive strength of SiC ceramics was 26.1 MPa and the elastic modulus was 6.27 GPa.When the holding time was between 10 min and 30 min,the porosity of the prepared SiC ceramics varied from 52.74%to 60.81%,and the density was 1.01 g/cm3～1.19 g/cm3,and the compressive strength and elastic modulus had maximum values at 20 min.(3)The effects of carbonization rate and sintering temperature on the porosity and compressive strength of SiC ceramics of camellia oleifera shell-based were analyzed.The results showed that the sintering process has an important influence on the properties and structure of SiC ceramics,and too high a carbonization rate will cause deformation or even cracking of the specimens,and in order to prepare SiC ceramics with good properties,the temperature rise rate is controlled between 5℃/min and 7.5℃/min,and the reaction temperature is 1550℃ The reaction temperature is about 1550℃.(4)The process parameters of warm pressing forming of SiC ceramics were optimized with the help of response surface test design and analysis method.The optimal combination of process parameters was forming temperature 153℃,forming pressure 35 MPa and holding time 30 min.The predicted values of compressive strength and porosity of SiC ceramics reached 26.56 MPa and 56.14%,respectively.