Study On Biomimetic Preparation Of Graphene-Coated Reinforced Ceramic Tool

In order to enhance the mechanical properties and cutting properties of alumina ceramic tool material,Al₂O₃/Si C@G ceramic materials were prepared used the spark plasma sintering-high-frequency（SPS-HF）dual sintering method to further optimize the sintering process.Bionic graphene-coated silicon carbide（Si C@G）core-shell structure was fabricated by liquid phase laser irradiation technology,and utilizing the floatability of noctiluca scintillans in seawater.The technology not only introduces Si C@G as the reinforcement phase,but also further enhances the dispersion of graphene.The Si C@G core-shell structure in the ceramic material as a three-dimensional network structure enhances the bonding strength between the matrix.In this thesis,the optimal sintering process of SPS-HF dual sintering was studied,and the optimal content of graphene in the matrix was determined.Then,the content of core-shell powder was determined by calculating the graphene content in Si C@G powder.Finally,Al₂O₃/Si C@G ceramic material was prepared.By observed the mechanical properties,microstructure and wear morphology of the ceramic material,the mechanism of toughening,strengthening and reducing friction of Si C@G core-shell structure was analyzed.Al₂O₃/G ceramic material was prepared by SPS-HF dual sintering process.Under the sintering condition of a temperature of 1350°C,pressure of 35 MPa and holding time of 8 min,the optimal mechanical properties of Al₂O₃ ceramic tool materials were obtained.The optimal content of graphene in the ceramic material was determined to be 0.5 vol%G.Compared with Al₂O₃ ceramic material,the flexural strength and fracture toughness of Al₂O₃/G ceramic material increased by 15.3%（617 MPa）and 63.4%(6.7 MPa·m^1/2),respectively.Si C@G core-shell structure with graphene floating band was prepared by liquid phase laser irradiation technology and the bonding strength of Si C and graphene in Si C@G core-shell structure was tested.It was founded that graphene was closely bound to Si C,and the ultrasonic power and ultrasonic time have no effect on it,indicating that graphene has a strong bond with Si C in the core-shell structure.The TEM sample of Al₂O₃/Si C@G ceramic material was prepared,and it was found that Si C@G bonded closely with Al₂O₃ matrix.The graphene floating band is embedded in the matrix particles to enhance the mechanical properties of ceramic tool.The Si C@G core-shell structure with graphene floating band has a good dispersion effect.In addition,the powder was not damaged in the sintering process,and the complete core-shell structure was maintained.The Vickers hardness,fracture toughness and flexural strength of Al₂O₃/Si C@G ceramic material reach 22.3 GPa,7.1 MPa·m^1/2 and 709 MPa.Through observation the HRTEM of sample,it was founded that graphene and Al₂O₃ matrix formed a new substance Al₄O₄C,forming a weak interface bonding.The weak interface can induce graphene to pull out from the matrix and improve the fracture toughness of ceramic material.The toughening mechanism of Si C@G core-shell structure with graphene floating band was analyzed by model.In this thesis,40Cr was selected as the cutting workpiece,and the cutting performance of bionic Al₂O₃/Si C@G ceramic tool was studied.When the cutting speed is 300 m/min,the back-engagement amount is 0.2 mm,and the feed rate is 0.102 mm/r,the optimal cutting process is obtained,and the effective cutting distance of Al₂O₃/Si C@G ceramic tool is about 5200 m.Experimental results show that Al₂O₃/Si C@G ceramic tool has better cutting performance than Al₂O₃/Si C/G ceramic tool.Si C@G core-shell particles can effectively improve the cutting performance of ceramic tool by improving the dispersion of graphene,the strong and weak bonding between core-shell structure and matrix,and the friction-reducing effect of graphene.