Preparation Of Graphene Reinforced Wood Ceramics Composite And Its Ballistic Performance Ballistic Performance

Silicon carbide wood ceramics have high strength to weight ratio and good mechanical properties.They can be used in biomedicine,wear-resistant parts and bulletproof materials.However,low toughness is one of its application bottlenecks.Therefore,ceramic materials with higher toughness are needed in many engineering fields.Industrial lignin can be used as carbon source to prepare biomass graphene and promote its high-value utilization.Graphene has excellent mechanical properties and is a good reinforcement in ceramic composites.However,in order to give full play to the reinforcing effect of graphene,it is necessary to ensure the stability of graphene in reactive sintering environment.The purpose of this study is to solve the disadvantage of ceramic brittleness by developing ceramic nanocomposites using nanostructured fillers.Kraft lignin was selected to prepare biomass graphene.Graphene reinforced Si C wood ceramics were prepared by using graphite nano platelets（GNPs）as reinforcing filler,and their mechanical properties were characterized.The thermal stability of graphene in inert atmosphere was investigated,and the nano Si C protective layer was prepared for GNPs by modifying with polycarbosilane（PCS）.The bulletproof properties of graphene reinforced Si C wood ceramics were characterized and analyzed.The main conclusions are as follows:（1）The results showed that graphene laminated structure was obtained after 90 min heat treatment when the ratio of lignin to iron particles was 3:1.Compared with commercial redox graphene,the prepared graphene has better lamellar integrity,but the yield is low,there are many impurities and it is difficult to separate,which limits its application in reinforced composite wood ceramics.The formation mechanism of lignin-based graphene includes the formation and decomposition of Fe₃C and the dissolution and precipitation of C atoms in iron particles.（2）GO/Bio Si C and r GO/Bio Si C composites were prepared by slip casting and reactive sintering technology.The effects of the amount and type of graphene on the properties of composites were studied.Adding 1.0 wt.%GO to Bio Si C matrix can increase the bending strength from 150 MPa to 239 MPa,and adding 1.5 wt.%GO can increase the fracture toughness by 33%.It is observed that the pull out of graphene and its distribution along the grain boundary are the reasons for the increase of fracture toughness.（3）To explore the effect of high temperature on the quality of graphene in reactive sintering,the effect of temperature on the stability of graphene in inert atmosphere was studied for the first time.The results show that The main defects of single layer graphene at 600℃are carbon bond deformation,SP3 hybridization or molecular adsorption defects.At 800℃and above,it is etched into dispersed and isolated graphene islands,and the boundary defects increase.Multilayer graphene has good stability.High temperature heat treatment will not cause obvious structural damage to multilayer graphene.（4）Nano Si C protective layer was prepared for GNPs by introducing PCS,which can prevent the erosion of molten silicon during silicon infiltration sintering.It was found that the GNPs modified by PCS have a firm interface with Bio Si C matrix.The toughness and hardness of the composites were further improved.（5）Bulletproof ceramics were prepared using GNPs and GNPs-PCS as reinforcement.Its bulletproof performance and mechanism were studied.The results show that only GNPs-PCS/Bio Si C resist 53mm armor piercing projectile at high temperature shows the improvement of bulletproof performance.The failure modes of ceramic materials are transgranular fracture and intergranular fracture.Graphene improves the toughness of composite ceramics through a variety of toughening effects,and plays a role in consuming fracture energy in the process of ceramic crushing.