Abstract: In order to improve the mechanical properties of the inorganic composites in service environment, the carbon fiber reinforced aluminum phosphate composites were prepared by filling ultra-fine kaolin and B₄C particles with self-made aluminum dihydrogen phosphate as matrix and carbon fiber as the reinforcement. The composites was characterized by mechanical universal testing machine, differential scanning calorimetry(DSC), X-ray diffraction(XRD), and scanning electron microscopy(SEM). The results showed that with the addition of two kinds of aggregate particles, the maximum density of carbon fiber reinforced aluminum phosphate composite reaches 1.871 g/cm³, and the bending strength increases first and then decreases at room temperature. Kaolin particles crack to form Al₂O₃ and SiO₂ at high temperature, and form a certain amount of SiC and molten substances composed of BPO₄ and B₂O₃ with B₄C, filling the pores generated by matrix cracking and reducing the structural defects of composite materials. When m[Al(H₂PO₄)₃]∶m(kaolin)∶m(B₄C) is 100∶35∶15, the maximum average bending strength is up to 129.5 MPa, and the bending strength is 65.47 MPa after 60 min heat treatment at 600 ℃. The mechanical strength retention rate reaching 50.56%, the mechanical strength retention rate was improved.

Key words: ultrafine kaolin, B₄C, phosphate composite material, mechanical properties, strength retention rate