Research On Preparation And Properties Of Low Dimensional Material Reinforced SiC Ceramics

With the rapid development in aerospace,new energy or other scientific and technological fields,the demand for structural materials used in extreme conditions(high temperature,acid and alkali corrosion)was increasing.Silicon carbide(SiC)was widely used in various fields for its excellent physical and mechanical properties,such as high hardness,wear resistance,high temperature resistance,low density.However,the flexural strength under room temperature and fracture toughness of SiC were poor,which greatly limited its development and application in various fields.To enhance the fracture toughness of SiC ceramics,the second phase particles were often introduced into the matrix,mainly including particles,whiskers or fiber toughening.In this paper,the method of composite toughening was adopted.The PDA-CNTs@f-Ti₃C₂ and PDA-CNTs@f-GNPs were prepared by selected the two-dimensional materials(GNPS,Ti₃C₂)and carbon nanotubes(CNTs)as raw materials while the Silane coupling agent KH560 and polydopamine(PDA)were used as modifiers respectively.To prepare SiC-based composite and improve the flexural strength and fracture toughness of SiC,the research results were as follows:(1)Preparation and characterization of PDA-CNTs@f-Ti₃C₂.Firstly,the CNTs and Ti₃C₂ were modified,and the modified materials were bonded together to prepare PDA-CNTs@f-Ti₃C₂ composites.The experimental results showed that the CNTs were successfully modified by PDA and bonded with the modified Ti₃C₂ particles.Sedimentation experiments showed that the PDA-CNTs@f-Ti₃C₂ composite was more uniformly and stably dispersed in water than CNTs and Ti₃C₂.(2)The PDA-CNTs@f-Ti₃C₂ was added in SiC matrix to prepare SiC composites,and its morphology,structure and another properties were detected by scanning electron microscopy,EDS and universal testing machine.Compared with the pure SiC,the hardness of SiC composites with 3 wt.%reinforcement filler was increased by6.8%.In addition,the bending strength of SiC matrix composites was increased by89%(from 228.99 MPa to 433.55 MPa).According to the experiments of three-point bending strength and single-side cut beam,the fracture toughness of SiC composite was improved by 62%(from 3.97 MPa·m^1/2 to 6.44 MPa·m^1/2)while the content of reinforcement filler was 3 wt.%.(3)Carbon nanotubes(CNTs)modified by PDA were bonded with GNPs modified by KH560 to form a novel PDA-CNTs@f-GNPs composite material.Then the novel PDA-CNTs@f-GNPs were mixed with pure SiC powder to prepare composites.The results indicated that when the content of the toughening filler increased from 0 wt.%to 5 wt.%,the density and hardness of the composite material gradually decreased,and the hardness decreased by 8.5 wt.%.In addition,the three-point flexural strength and single-side notched beam experiments indicated that the flexural strength and fracture toughness of SiC composites both increased first and then decreased while the content of toughening fillers increased.When the content of toughening filler was 3 wt.%,the flexural strength and fracture toughness of SiC composites reached the maximum,which were 370 MPa and 5.78 MPa·m^1/2,respectively.