Preparation And Properties Of Lightweight Bulk Carbon

In modern material design,designing and manufacturing high-strength,large elastic deformation,and low-density high-performance materials is a long-term goal and challenge.In aerospace materials,while ensuring the material’s relatively high strength,the lower density of the material,the less its additional energy consumption.Almost all structural materials have two pairs of obvious conflicts:one is the conflict between high strength and large elastic deformation;the other is the conflict between high strength and low density.Some light element compounds,such as silicon carbide and boron carbide,have become the materials of choice for military armors,aviation protective covers,and some important equipment protection devices due to their combination of low density and high strength.However,most ceramics can only undergo small elastic deformation(<1%),and brittle fracture occurs immediately after exceeding the elastic limit.Because carbon has the flexibility to form sp,sp~2,and sp~3 hybrid bonds,carbon may become a material with excellent comprehensive properties,such as low density,high strength,high hardness,high elasticity and adjustable electronic properties.In this paper,diamond nano-powders with different particle sizes(6 nm,10 nm,35 nm,80 nm,230 nm)are selected as raw materials,and the spark plasma sintering method(SPS)is used to study diamond nano-powders at 40 MPa and different temperatures.The particle size of the sintered lightweight bulk carbon is inherently related to the microstructure and mechanical properties.Among them,the carbon block prepared by sintering diamond powder with an average particle size of 6 nm at 1500℃has better overall performance.The density of the bulk carbon is 0.85 g/cm~3 and the compressive strength reaches 312MPa.,The ultimate elastic strain reaches 6.5%.The microstructure of this bulk carbon is formed by the chaotic arrangement of curved graphene fragments,and a large number of closed pores are generated between the graphene fragments;the raw material particle size is 35 nm and The bulk carbon material obtained by sintering 80 nm powder has a different organizational structure from the bulk carbon material obtained by sintering diamond powder of 6 nm and 10 nm.It is composed of onion-like multilayer graphene entangled with each other.The raw material The bulk carbon material obtained by sintering diamond powder with a particle size of 35 nm has the highest compressive strength,and its compressive strength reaches 537 MPa;we have selected a lightweight bulk carbon material obtained by sintering diamond nano-powder with a raw material particle size of 6nm Nanomechanics experiments have been carried out.The test results show that the compression behavior of lightweight bulk carbon has obvious size effects.By reducing the sample size to the order of micrometers,the compressive strength of the synthesized lightweight carbon materials can be further improved.When the size of the micro-pillars is reduced to 1μm,the compressive strength reaches 0.8 GPa,and the total compressive strain is close to 30%,accompanied by obvious plastic deformation.