Enhanced mechanical properties of SiO _2f /SiO ₂ composites via sol–gel fabrication of Al ₂ O ₃ coatings on quartz fiber

Abstract In order to improve the mechanical properties of the SiO 2f /SiO 2 composites, the uniform and complete Al 2 O 3 coatings were prepared on the quartz fibers via sol–gel method with aluminum isopropoxide as the precursor. The thickness of Al 2 O 3 coatings increases with concentration of aluminum isopropoxide precursor solution. The Al 2 O 3 coatings fabricated with 10 wt.% precursor solution were uniform and complete, and its thickness was approximately 430 nm. The SiO 2f /SiO 2 composites with Al 2 O 3 coatings achieve higher mechanical strength compared with the SiO 2f /SiO 2 composites without Al 2 O 3 coatings. The flexural strength of SiO 2f /SiO 2 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 /SiO 2 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 Al 2 O 3 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 /SiO 2 composites. The mechanical strength of SiO 2f /SiO 2 composites with Al 2 O 3 coatings was increased after not only short‐term but also long‐term heat treatment.