Fabrication of electrospun Al2O3 fibers with CaO–SiO2 additive

Alumina fibers were fabricated by the sol–gel method combined with an electrospinning process using aluminum chloride hexahydrate (AlCl3·6H2O) and aluminum powder as raw materials in water solvent. Calcium oxide–silica (CaO–SiO2) was applied as two-component additive to retard the phase transformation of alumina and control the size of the grains during sintering. With the addition of the CaO–SiO2 in the system, the size of the particles that composed the fibers calcined at 1300 °C significantly decreased compared to that without additive, which might be due to the formation of θ-alumina in the samples. In addition, the fiber had low thermal conductivity and good flexibility, which favored its application in insulation.

► Flexible alumina nanofibers with CaO–SiO2 additive were fabricated.
► CaO–SiO2 additive could inhibit grain growth of the electrospun fibers.
► CaO–SiO2 additive retarded the phase transformation from γ-Al2O3 to α-Al2O3.
► Fiber calcined at 1300 °C with CaO/SiO2 ratio of 1:10 had low thermal conductivity.