Enhanced mechanical properties of SiO2f/SiO2 composites via sol–gel fabrication of Al2O3 coatings on quartz fiber

In order to improve the mechanical properties of the SiO_2f/SiO₂ composites, the uniform and complete Al₂O₃ coatings were prepared on the quartz fibers via sol–gel method with aluminum isopropoxide as the precursor. The thickness of Al₂O₃ coatings increases with concentration of aluminum isopropoxide precursor solution. The Al₂O₃ coatings fabricated with 10 wt.% precursor solution were uniform and complete, and its thickness was approximately 430 nm. The SiO_2f/SiO₂ composites with Al₂O₃ coatings achieve higher mechanical strength compared with the SiO_2f/SiO₂ composites without Al₂O₃ coatings. The flexural strength of SiO_2f/SiO₂ composites increases with concentration of aluminum isopropoxide precursor solution. And the compressive strength shows a slightly decreasing trend with concentration of aluminum isopropoxide precursor solution. The mechanical performance of the SiO_2f/SiO₂ composites fabricated from fibers coated with 10 wt.% aluminum isopropoxide precursor solution was excellent, and its compressive strength was 57.1 MPa, flexural strength was 28.6 MPa. And the reason was that the Al₂O₃ coatings effectively enhanced the interface isolation between the fiber and the matrix, optimizes the deflection path of the crack and increased the strength of the SiO_2f/SiO₂ composites. The mechanical strength of SiO_2f/SiO₂ composites with Al₂O₃ coatings was increased after not only short-term but also long-term heat treatment.