Effect of heat treatment conditions on magnesium borate fibers prepared via electrospinning

The influence of different heating rates as well as different atmospheres on magnesium borate fibers produced by electrospinning was investigated in this work. The green fibers were prepared from sol-gel precursors, using polyvinyl-pyrrolidone (PVP) as processing aid. Crystalline fibers with the typical necklace structure and average diameter in the range 300-500 nm were produced when heating up to 900 °C in air. The main phase detected by XRD analysis was in this case Mg2B2O5. On the other hand, the fibers slowly heated in reducing atmosphere to 800 °C exhibited similar dimension but a different morphology. The crystalline grains were presumably smaller, hence the necklace effect was absent. This sample also revealed a much higher specific surface area in comparison to the samples calcined in air. Mg3B2O6 was here the main crystalline phase, while a part of boron was lost during the thermal treatment.