Study on the growth morphology and induction mechanism of strontium hydroxyapatite controlled by anionic and cationic surfactants

• Published in: Journal of alloys and compounds Vol. 835; p. 155385
• Main Authors: Huang, Jiangsheng, Chen, Changlian, Huang, Zhiliang, Wu, Changsheng, Cheng, Yilin, Chen, Song
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.09.2020; Elsevier BV
• Subjects: Ammonium bromides; Benzene; Cations; Crystal growth; Crystal morphology; Crystal structure; Crystals; Free energy; Growth models; Heat of formation; Hexagonal column; Hydroxyapatite; Induction mechanism; Interfacial energy; Low temperature; Morphology; Plate-like; Scanning electron microscopy; Sodium dodecylbenzenesulfonate; Sodium phosphate; Strontium hydroxyapatite; Surfactants; Strontium hydroxyapatite; Induction mechanism; Hexagonal column; Plate-like; Surfactants
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.155385

Using Sr(NO3)2, NaH2PO4 and urea as the raw starting materials, under the induction of anionic/cationic surfactants (sodium dodecyl benzene sulfonate (SDBS) and dodecy dimethyl benzyl ammonium bromide (DDBAB)), strontium hydroxyapatite (SrHAp) crystals with different morphology were successfully synthesized at low temperature (85 °C). The XRD patterns analysis showed that both surfactants could induce the growth of pure SrHAp crystals. The SEM images showed that the SrHAp crystals grew under DDBAB induction was one-dimensional hexagonal column along c-axis. The SEM and HRTEM images provided that the growth of SrHAp crystal induced by SDBS generated two-dimensional plate-like structure, along both a- and b-axis. It is indicated that the ionic structures of DDBAB and SDBS affect the crystal growth and development of the SrHAp hexagonal system. According to the crystal plane formation energy (Gibbs-Thomson formula) and the crystal plane normal growth rate formula, the crystal-induced directional growth model was obtained and its formation mechanism was analyzed. Our results revealed that the surface active fragment C21H38N+ of DDBAB and the fragment C18H29SO3− of SDBS could change the interfacial energy (γ(hkl)) of the crystal plane, affect the normal growth rate of the crystal plane (І(hkl)), and finally control the crystal morphology of SrHAp. Therefore, under the induction of C21H38N+, γc{001} < γm{100} and Іc{001} > Іm{100} enable the crystal grow along the c-axis resulting in the hexagonal column morphology of SrHAp crystal. However, the induction of C18H29SO3− gives γc{001} > γm{100}, Іm{100} > Іc{001}, which drives the crystals grow along both a- and b-axis generating plate-like morphology of SrHAp crystal. •The morphology of SrHAp crystal is hexagonal column under the induction of C21H38N+.•The morphology of SrHAp crystal is plate-like under the induction of C18H29SO3−.•The crystal-induced directional growth model was obtained.•The formation mechanism of crystal induced-directional growth model was analyzed.