Study On The Effect Of Surfactants On The Synthesis Of Hydroxyapatite Nanowire

Hydroxyapatite (HA) is the mainly inorganic composition of bones and teeth of humans and animals, with good bioactivity and biocompatibility. It can combine with bones firmly and is the main substitute materials of human bones and teeth. As the growing acknowledgement of hydroxyapatite research in recent years, people have synthesized various kinds of HA crystal structures. For instance, HA non-crystalline materials, HA microspheres materials, HA mesoporous materials, HA whiskers, HA fibers and etc..This paper illustrated a kind of biomaterial nano fiber-HA nano fiber/nanowire. This research work focused on three kinds of anionic surfactants (sodium lauryl sulfate, sodium dodecyl benzene sulfonate and sodium dodecylsulphate) and one kind of cationic surfactants (Cetyl trimethylammonium bromide, CTAB), the purpose of which is to find a feasible route of preparing HA nanowires.This paper adopted two kinds of technological routes, they were co-titration method and chemical precipitation method in seperate. The raw materials were calcium chloride (CaCl2) and disodium hydrogen phosphate (Na2HPO4), the initial Ca/P was5:3, the hydroxyapatite crystals prepared in co-titration method using anionic surfactants (sodium lauryl sulfate, sodium dodecyl benzene sulfonate and sodium dodecylsulphate) were short-rod like and granular, with the length to diameter ratio lower than10. The raw materials were calcium nitrate (CaNO3) and diammonium phosphate ((NH4)2HPO4), the initial Ca/P was5:3, the hydroxyapatite crystals prepared in chemical method using anionic surfactants (sodium lauryl sulfate, sodium dodecyl benzene sulfonate and sodium dodecylsulphate) were mostly short-rod like, and some were longer. When the concentration of surfactants was low, the surfactants reacted as dispersants; as the concentration increased, the dispersion effect became limited, with the size of HA showed a growing trend.The raw materials were calcium chloride (CaCL2) and disodium hydrogen phosphate (Na2HPO4), the initial Ca/P was5:3, the hydroxyapatite crystals prepared in co-titration method using cationic surfactants (CTAB), were short-rod like and granular, with the length to diameter ratio lower than10, severe agglomeration and poor crystallinity. The raw materials were calcium nitrate (CaNO3) and diammonium phosphate ((NH4)2HPO4), the initial Ca/P was5:3, the hydroxyapatite crystals prepared in chemical method using cationic surfactants (CTAB) were short-rod like, with fascicled agglomeration. By altering the initial Ca/P to4:3, the HA prepared in chemical method were like long fibers, with length more than2μm and diameter around50nm. The size distribution was homogeneous. HA nanowires were staggered and disorderd. The dispersion and crystallinity were good. HA nanowires was single crystal. The blank control was leaf like and the raw materials were calcium nitrate (CaNO3) and diammonium phosphate ((NH4)2HPO4), the initial Ca/P was5:3.When the heat treatment temperature of the HA nanowires was above600℃, HA partial melted and decomposed into Ca3(PO4)2and Ca9HPO4(PO4)5OH. When the heat treatment temperature of the HA nanowires was lower than600℃, HA did not decompose and the crystallinity turned better.Finally, this paper analysed and discussed the reaction mechanism of HA nanowire, and illustrated the template effect of surfactants. When the concentration of surfactants is higher than the critical micelle concentration (cmc), surfactants tend to form ordered micelle structures. We can consider the micelle structure as a new phase. Take CTAB for example, excessive CTAB can form hexangular micelle structure in water. The exchange of excessive PO43-ions and Br-can form CTA-PO43-structure. HA nanowires grows along the axial direction of the template-CTAB hexangular micelle structure.