Preparation And Related Characterization Of Cerium-doped Hydroxyapatite/polylactic Acid (or Graphene) Composites

Hydroxyapatite(Ca₁₀（PO₄）₆（OH）₂,HA)is the main inorganic component of the mineralized tissues such as bones and teeth in mammals,and has good bioactivityand biocompatibility,The prepared hydroxyapatite has been applied to the filling material of bone defect and the surface material of metal prosthesis.HA contains some other ions,such as Fe,Mg,Sr,Ce,in the field of the research,hydroxyapatite materials have been widely studied by doping trace metal ions,which can effectively improve itsphysicochemical properties and biocompatibility.This can finallyenhance the adaptability of HA application in bone repairs.However,the intrinsic brittleness of HA,low fracture toughness and low toughness-induced poor wear resistance,still restricts its clinical applications.Therefore,toughening of HA with a second phase GP has been extensively explored to overcome the deficiencies of the HA.The hydroxyapatite powders were successfully synthesized by chemical precipitation method under the condition of water bath,with calcium chloride as calcium source and sodium hydrogen phosphate as the source of phosphorus,respectively.HA/PLA composite coatingson stainless steel substrates werefabricated by HA/PLA suspension.Ce-doped HA powdersweresynthesized by chemical precipitation method with different Cemolar fractions（0（pure HA）,0.5 mol%,1 mol% and 2 mol%）.And Ce-doped HA/PLA composite coatings were fabricatedfor the first time on stainless steel substrates by spin coating technique.The results showed the preparedHA,Ce-HA powdersexhibit high crystallinity and purity without any impurity phase.HA/PLA composite coatings can achieve dense adhesion and crack-free effects through the heat treatment conditions of air atmosphere at 600 ℃.In the process,PLA is decomposed into a char residue which could inhibit the decomposition of hydroxyapatite into other impurities.Ce ions were doped into the crystal lattice of apatite successfully.The addition ofPLA could keep metal substrates from catalyzing the decomposition of HA.Ce-doped HA powder had high thermal stability,the surface topography of Ce-doped HA/PLA composite coatings was uniform and dense.When the Cemolar fraction was 2 mol%.XPS results indicated that the Ce ions doped in HA showed mixedvalences of Ce³⁺ and Ce⁴⁺.Graphene shows a lamellar structurelike folded paper,HA was scattered on its surface,where no serious agglomeration was shown.The composites exhibited good morphology when small amount of Ce ions was doped,whereasthe high proportion of Ce ion doping not only changed the morphology of HA,but also formed the amorphous phase and further caused the agglomeration.Meanwhile,the physical and chemical reactions between HA and GP occurred in the hydrothermal process.