基于木质素基石墨烯的反应烧结碳化硅制备及其在防弹领域应用

Biomorphic silicon/silicon carbide ceramic has been used as combat bulletproof materials due to its low density, high hardness and high strength. However, the ceramic is readily fracture when a strong impact coming from a bullet because of its low fracture toughness, which limits its application as a bulletproof armor. The recent research found that graphene has a lamellar structure. The lamellar features can be maintained when reaction with silicon at high temperatures to produce silicon carbide. A complex internal interface in the reaction bonded silicon carbide can be formed due to the lamellar structure. It could increase its impact resistance significantly. The project intends to prepare structure-controlled lignin-based graphene with low-cost and high efficiency using lignin. Compounding graphene and wood carbon powder with certain proportions to produce green body with homogeneous porous structure by dry compress molding. The Biomorphic silicon/silicon carbide ceramic will be manufactured when reaction between the green body and melted silicon occurred at high temperature. The preparing parameters will be determined by investigating the compositions, structures and sintering process of the ceramics. The bulletproof mechanism of the graphene-based biomorphic silicon/silicon carbide ceramics will be revealed based on the microstructures, mechanical properties and ballistic performances. This project will study on graphene-based biomorphic silicon/silicon carbide ceramics with high performance and apply it as bulletproof armor. The results of this study will lay a theoretical foundation for newly bulletproof materials studies.

碳化硅木质陶瓷作为单兵防弹材料具有密度低、硬度高、强度高的特点，但断裂韧性较低，受到强烈冲击时易发生碎裂，限制了其在防弹领域的应用。最新研究发现，石墨烯具有层片结构，与硅在高温下反应生成的碳化硅晶粒可保持层片结构，在碳化硅内部形成复杂的界面，从而大幅提高木质陶瓷的抗冲击性能。本项目拟以木质素为原料，经高温石墨化工艺制备低成本、高得率、结构可控的木质素基石墨烯；将石墨烯与木质碳粉以一定的比例混合，通过模压成型制备具有多孔结构的素坯；素坯在高温下与熔融单质硅反应生成碳化硅陶瓷；通过研究碳化硅陶瓷坯体组成、结构及反应烧结工艺，确定高性能反应烧结碳化硅陶瓷制备技术条件；根据对石墨烯基碳化硅陶瓷显微结构、力学性能和弹道性能的测试分析，探索其防弹机理。本项目开展以木质素基石墨烯和木质碳粉为原料制备高性能碳化硅陶瓷研究并用作单兵防弹材料，为新型防弹材料的研究和应用奠定理论基础。

碳化硅木陶瓷具有质量轻、比表面积大、硬度高的特点，但存在断裂韧性低的问题，为实现其高性能、成本低、质量轻、可靠性好的性能统一，项目以工业木质素为原料，经高温石墨化工艺制备低成本、结构可控的木质素基石墨烯并解析了其构建机制。系统表征木质素基石墨烯的宏观形貌、微/纳观结构、表面化学特性等，揭示木质素基石墨烯的结构与特征。通过模压成型工艺制备木质碳粉-石墨烯成型预制体，通过烧结渗硅工艺使石墨烯与单质硅发生化学反应，制备反应烧结碳化硅，阐明C、Si 反应机理和石墨烯与硅在高温下的反应机制。分析表征反应烧结碳化硅木质陶瓷的组成与微观结构，测试其力学性能，包括弯曲强度、显微硬度、弹性模量、断裂韧性、动态抗冲击性能，揭示其组成、结构与性能之间的相互关系。研究晶粒尺寸对反应烧结碳化硅力学性能特别是对冲击韧性的影响。测试了石墨烯增强碳化硅木质陶瓷防弹性能，分析表征基于木质素基石墨烯的反应烧结碳化硅陶瓷的纤维结构、力学性能和防弹性能，揭示其防弹机理。研究表明：在铜箔表面的化学气相沉积(CVD)法制备木质素基石墨烯缺陷密度为0.54，具有较好的均一性。铁粒子催化制备木质素基石墨烯，热处理温度为1200℃，保温时间为90分钟，碳源与催化剂比为3:1，石墨烯层数为4到8层，为寡层石墨烯，具有良好的褶皱结构。采用氧化石墨烯粉体、氧化石墨烯浆料和热还原氧化石墨烯分别作为SiC木陶瓷的增强相，研发表明，石墨烯增强碳化硅的主要晶相结构为 Si、α-SiC 和 β-SiC，相同工艺下，石墨烯增强碳化硅具有较好的机械性能，弯曲强度提高了58%。氧化石墨烯通过原位还原，可与陶瓷基体具有良好的相容性。防弹性能测试表明，改性石墨烯增强的SiC陶瓷，在高温下对53mm穿甲弹具有较好的防弹性能，与未添加石墨烯的碳化硅防弹陶瓷相比，凹陷深度降低了4mm。在抵御5.8mm钢芯弹时，石墨烯与改性石墨烯复合的碳化硅陶瓷防弹性能相差不大。