Coupled thermal analysis of novel alumina nanofibers with ultrahigh aspect ratio

• New alumina nanofibers (7 and 40 nm diameter) with ultra-high aspect ratio (>10,000,000) have been analysed using thermal analysis.
• Thermal effects, mass changes and gases evolution were studied with coupled TG, DSC and FTIR.
• Possible phase transformations were in parallel evaluated by high-temperature XRD and SEM.
• The changes observed are discussed vs. known literature data fro alumina phases.

The phase conversions and morphological changes of commercial alumina nanofibers (ANF) with 7 and 40 nm in diameter during heat treatment were investigated. These super-high aspect ratio (length-to-diameter ratio is ∼107) fibers are mostly composed of partially hydrated (2–6 wt.%) gamma-alumina phase. The transformations of the ANF during heating up to 1480 °C were studied simultaneous coupled thermal analysis (TG-DSC-FTIR) supported by XRD and SEM examinations. It was found that for ANF gamma-phase starts to transform into stable α-alumina from ∼1250 °C, but the water releases during most of the heating time at least in two stages. The behavior of the material and observed changes are discussed and compared with literature date for different alumina materials.