The effect of citric acid addition on sol–gel preparation of apatite films

Apatite-coated bio-inert implants can provide well-behaved bone substitutes in bioactive and mechanical properties. In this work, citric acid (CiA) was added into a dipping solution of 1.67Ca(NO3)2–PO(OH)x(OEt)3−x to investigate its effect on wettability, apatite formation, and film morphology. The dipping solution with a CiA/Ca ratio of 0.5 led to a good wettability on alumina substrates, formation of oxy-hydroxyapatite phase in the film after 800 °C heat treatment, rough or porous surface morphology, and adhesive strength up to 10 MPa. CiA in the dipping solution has a strong gelation ability and gives rise to corresponding changes in the film.