Rapid hydrothermal synthesis of submillimeter ultralong flexible hydroxyapatite fiber using different pH regulators

Abstract

Hydroxyapatite fiber (HAF) was fabricated via a one-step hydrothermal route by using urea (CA), acetamide (AA) and propanamide (PA) as pH regulators, respectively, and the reaction time was only 0.5 h. The HAF synthesized by CA as the pH regulator was agglomerated with irregular morphology, while using AA or PA as the pH regulator, the HAF was composed of well-dispersed fibers with lengths larger than 200 μm. Two different morphologies form mainly due to the different hydrolysis rates of the pH regulators. Most of the fibers synthesized by the three pH regulators showed curving appearance, implying their outstanding flexibility. The technique in this paper allows the rapid formation of flexible HAF and may have wider applications in the restorations and reinforcement composites.