Morphology preservation and crystallinity improvement in the thermal conversion of the hydrothermal synthesized MgBO2(OH) nanowhiskers to Mg2B2O5 nanowhiskers

Preservation of one-dimensional (1D) morphology and improvement of crystallinity in the thermal conversion route to magnesium borate (Mg2B2O5) nanowhiskers at a relatively low temperature as 650-700 deg C (200-350 deg C lower than that of the literature) based on the hydrothermal synthesis of magnesium borate hydroxide (MgBO2(OH)) nanowhiskers were investigated; the results indicated that thermal conversion at appropriate temperature with a slow heating rate was favorable for the morphology preservation and crystallinity improvement. A specific heating procedure was developed according to the recrystallization phenomenon existing in the thermal conversion of the MgBO2(OH) nanowhiskers to produce Mg2B2O5 nanowhiskers with uniform morphology, improved crystallinity and fewer pores, in which Mg2B2O5 nanowhiskers (15.0-45.0 nm in diameter, 0.2-2.0 mum in length) were synthesized by heating MgBO2(OH) nanowhiskers (1.0 deg C min-1) to 650 deg C for 2.0 h of isothermal condition first to preserve the 1D morphology, and thereafter to 700 deg C (1.0 deg C min-1) for another 2.0 h of isothermal state to recrystallize. The designed specific heating procedure to reduce the mesopores and deformation could also benefit synthesis of other 1D anhydrous nanostructures via the wet chemistry-based thermal conversion route.