Molten-salt assisted synthesis and characterization of Mg₂B₂O₅ and Al₁₈B₄O₃₃ whiskers

Abstract

In this work, magnesium borate (Mg 2 B 2 O 5 ) and aluminum borate (Al 18 B 4 O 33 ) whiskers with a high aspect ratio were successfully synthesized using a molten salt method. The phase transformation and morphology involution of the whiskers were studied by XRD, IR-FT, TG-DSC, and SEM-EDS with different boron/metal ratios and reaction temperatures. The results show a rich boron environment and appropriate reaction temperature to be the crucial factors with respect to the composition and morphology of the borate whiskers. Mg 2 B 2 O 5 whiskers with a diameter of several hundred nanometers and a 10-60 length-diameter ratio were obtained when the B/Mg ratio was 1.5:1 and the reaction temperature was 800°C. For Al 18 B 4 O 33 whiskers, a synthesis temperature of 1000°C and a B/Al ratio of 3:9 were found to be optimal with respect to the whisker morphology. A liquid-solid (LS) mechanism is proposed as the growth mechanism of the whiskers on the basis of the experimental phenomena.

Controllable fabrication of a hybrid containing dodecyl dihydrogen phosphate modified magnesium borate whisker/hydrated alumina for enhancing the fire safety and mechanical properties of epoxy resin

“…It can also be produced following the process of chemical synthesis. 20–23 According to previous reports, the mechanical properties of polymers can be improved by embedding MBW into them. The improvement can be primarily attributed to the near-perfect crystal structure and high tensile strength of the composites.…”

Magnesium Borates: The Relationship between the Characteristics, Properties, and Novel Technologies

“…The characteristic features of the samples associated with the composition, crystalline phases, and morphology are dependent on synthesis procedures. The magnesium borates can be fabricated in various morphologies of the rod, sphere, tube, whisker, belt, wire, porous, or multi-angular at both nanoscale and microscale [15,40].…”

“…Kumari et al [15], synthesized the nano-scale whiskers of magnesium borates in hydrothermal conditions without a capping agent [15]. Liu et al [40], prepared submicron rods of a dehydrated form of magnesium borates by calcination at higher temperatures than 600°C [40]. Guo et al [38], designed a hybrid method to fabricate the 3D hierarchical flower-like particles of magnesium borates [38].…”

“…In the phase diagram of Liu et al [40] for the solid-state synthesis of magnesium borates, the reaction commonly occurs at higher reaction temperatures than 800°C [40]. In this synthesis procedure, the main drawback of solid-state is the requirement of grinding and sieving processes after the solid-state reaction.…”

“…Figure 4.Examples of the different morphologies of magnesium borates (a) nano-scale whisker by Kumari et al[15], (b) sub-micron rod by Liu et al[40], and (c) flower-like particle byGuo et al [38].…”