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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.

Multi-walled carbon nanotubes (MWCNTs) have been recently applied on the surface of carbon-bonded alumina filters in order to influence the reactions occurring during the first contact with the steel melt. They could potentially accelerate the deposition of endogenous particles, which would in turn result in a better filtration process. In the present work, the performance of MWCNTs-coated carbon-bonded alumina filters was assessed in comparison to uncoated filters, using a special steel casting simulator under controlled atmosphere. Short immersion times were used in order to better compare the behavior of these samples and check the microstructure evolution at the beginning of the filtration process. The microscope investigations indicated a better performance of the MWCNTs-coated filters, both after 10 and 30 s of immersion.