Graphene Toughening Alumina Matrix Composite Ceramic Material By Microwave Sintering

Al₂O₃ composite ceramics materials received extensive concern due to its excellent properties, such as high mechanical properties, good electrical insulation, wear resistance, corrosion resistance and high temperature resistant, etc, and be widely used in the covering high speed cutting tools, dental implants, chemical and electrical insulators, were resistance parts and various coatings. However, the weakness that its high brittleness is greatly restricting the scope of its application, sudden changes in environmental temperature could have an influence on its performance. Therefore, how to solve the problem low fracture toughness has become the priority in the ceramic application of Al₂O₃. In this paper, The preparation of Al₂O₃ composite ceramic reinforced with graphene platelets with addition of 0, 0.2, 0.4, 0.6 and 0.8vol.% was synthesized using a microwave sintering apparatus. Composite powders were obtained by ball milling of graphene platelets and alumina powders using yttria stabilized ZrO₂ balls. The influence of graphene proportion and sintering process on phase composition, microstructure and mechanical properties of Al₂O₃ ceramics was investigated by X-ray diffraction?XRD?, scanning electron microscopy?SEM?, three-point bending test and single-edge notched beam method. The effects of graphene on the microstructure of Al₂O₃ matrix were observed, the effects of different sintering processes on the properties were analyzed. The mechanism of strengthening and toughening by grapheme on Al₂O₃ material was investigated. What is more, many kinds of surfactants was used to disperse graphene in order to solve the problem of grapheme go together in the Al₂O₃ substrate.The results show that with the modification of 1-Methyl-2-pyrrolidinone?NMP?, uniform and stable graphe ne solution can be obtained. The addition of suitable amount of graphene could significantly increase the properties of Al₂O₃ based composite ceramic material, such like relative density, micro hardness, fracture toughness as well as bending strength. When graphene content comes to 0.4vol.%, comprehensive performance is better, when the graphene content exceeds 0.4vol.%, the comprehensive performance decreased with the increase of graphene content. The relative density, microhardness, bending strength, fracture toughness of the ceramic composite increased at first and then decreased with the increase of sintering temperature and holding time, peaked at 1500 ?and 30 min, respectively. The performance indicators of composite samples after microwave sintering are superior to pure Al₂O₃ ceramics, the relative density of 0.4vol.% graphene composite ceramics reached 98.76% by microwave sintering in 1500 ? for 30 min, and hardness was 19.58 GPa, fracture toughness was 6.19 MPa ·m1/2 and bending strength was 365.10 MPa. Compared with pure Al₂O₃ ceramics, fracture toughness and bending strength increased by 79% and 12%, respectively. Graphene wraps and bundles Al₂O₃ grains together, forming the anchoring effect. The anchoring effect is more excel ent than traditional crack deflection and crack bridging.