Preparation And Research Of Ramie Fabric Remnant Ceramics And Its Cu-based Composite Materials

Ceramic/metal matrix composites with the advantages of hardness,modulus,strength,heat conduction,electrical conductivity,high temperature resistance and wear resistance have great potential applications in the fields of automobiles,high speed trains,rail transit,aerospace,bullet protection materials,nuclear power engineering and electronic packaging.With the natural inspiration,a new type of biomorphic ceramic/metal matrix composite was developed to improve the strength and stiffness of the metal matrix composites and to reduce the plasticity and damage tolerance by enhancing the synergism,coupling effect and multi-function response mechanism between the metal phase and the ceramic phase.The low enhancement efficiency of traditional metal matrix composites has been solved,which becomes a new hot spot.It is particular advantage in enhancement that combined configuration design and the natural fiber structure ceramic.Ramie fabric morph-genetic SiC and Al₂O₃ porous ceramics were prepared from ramie fibers based on the adjustable morphic structure and the controllable reticular texture by template concersion method and template substitution method respectively,it is from the view of artificial reconstruction of template structure to explore the configuration reinforced metal matrix composites.And the morph-genetic ceramic/metal matrix composites were prepared using ramie fabric morph-genetic ceramic by pressureless infiltration controlling the technological parameters,such as atmosphere,temperature,infiltration time and cooling modes.The phase composition,microstructure,specific surface area,pore size distribution and foundation properties of ramie fabric morph-genetic ceramic were tested and characterized by SEM?XRD?TEM?EDS?TG?Specific surface meter to research the morph-genetic mechanism.And the prepared morph-genetic ceramic/metal matrix composite was studied to reveal the pressureless infiltration mechanism for Cu alloy to lay the foundation for the preparation of high-performance ceramic/metal matrix composites.The main research contents and results are as follows:The ramie fabric morph-genetic SiC ceramic was fabricated by textile technology and liquid phase in situ reaction sintering.The influence of morphic-genetic process parameters on the microstructure and physical properties was studied.And the morph-genetic mechanism for thin walled template was explores.The prepared morphic-genetic ceramic maintains the ramie fabric macrostructure and replicates the microscopic tubular structure,which possesses high porosity and low density for the fabric void,ramie tubular and grain pore.The morph-genetic mechanism of ramie fabric morph-genetic SiC ceramic is the solid liquid solid?SLS?mechanism of carbon in the melt reaction of SiC.The final SiC particle size,nucleation and growth is determined by the mass ratio of C and Si and thickness of template.It is found that the morphic-genetic conversion process parameters including sintering temperature,preservation time and mass ratio of C and Si reduce the composite precursor volume shrinkage,and surpress cracking and warpage of the composite precursor during pyrolysis to minimize the rearrangement of template.The microstructure,morph-genetic conversion process,resistivity and flexural strength for the morph-genetic SiC significantly are affected by the sintering temperature,preservation time and mass ratio of C and Si.The ramie fabric morph-genetic Al₂O₃ ceramic was prepared by textile technology and template substitution method.The organizational structure of the ramie fabric morph-genetic Al₂O₃ ceramic was discussed and the mechanism of impregnation and morphic-genetic of inorganic polymers was revealed.The prepared ramie fabric morph-genetic Al₂O₃ ceramic is high porosity?76.5-78.8%?,low thermal conductivity(0.070-0.087W·m^-1·K^-1)and stable dielectric properties.The morphic-genetic concersion process for removing template includes the adsorption,networking,decomposition of organic oxidation and polyaluminum compounds,shrinkage of morph-genetic structure,phase transition and growth of Al₂O₃.The aluminum content of the impregnated polymer not only affects the structure of the morph-genetic ceramic,but also affects the apparent porosity,specific surface area,pore size distribution and thermal conductivity.A rapid pressureless infiltration process of Cu alloy into textile structural ceramic was developed to prepare the ramie fabric morph-genetic Al₂O₃/Cu composite.The microstructure and infiltration process parameters including the content of O,infiltration temperature,infiltration time and cooling modes were discussed,and the influence of infiltration process parameters on the microstructure,densification degree and properties were revealed.The microstructure rcombination,organizational transition and performance changes of the ramie fabric morph-genetic Al₂O₃/Cu composite as the variation of infiltration parameters was explored.It was found that the oxygen content determines the infiltration rate of Cu.The infiltration temperature and time affect the infiltration rate,densification and microstructure.And the cooling rate has effect on both the microstructure of the metal phase and the distribution of the reinforcement.The property results of the ramie fabric morph-genetic Al₂O₃/Cu composite showed that the hardness represents zoning characteristics.Rapid cooling,high infiltration temperature and long infiltration time can improve the hardness of the composite.The main fracture of the composite material is intergranular brittle fracture.The low flexural strength of composite is due to the mechanical weak interface and pore defects,which is determined by the Cu volume fraction and infiltration time.The reaction thermodynamics and infiltration kinetics of Cu-Al-O system were studied to reveal the action mechanism of O and infiltration mechanism.The oxygen improves the viscosity of copper melt by adsorption and diffusion to enhance the flow ability of the melt,and participates in chemical reaction of Cu and Al₂O₃ to improve the wettability to enhance its permeability.The infiltration rate of metal Cu with oxygen element is estimated by the modified kinetic model for the reaction infiltration system.The inconsistency of the experimental value and the theoretical value indicates that capillary wetting infiltration is not the only way for metal infiltrating into reinforcements with the nonuniform pore structure.The Cu-O rapid infiltration model,including oxidation wetting,influent rapid infiltration and structural reorganizationinfiltration,is proposed.The oxygen is combined with Cu through chemical reaction and diffusion process.The formed Cu-O melts fill the macropores as influent,and small pores as capillary infiltration with the critical size of the pore is 6?^1/3/??^1/3.The subsequent closed pores or micropore-macropore structure were capillary infiltration that is determined by capillary wetting size.