Rapid Biomimetic Coating of Calcium Phosphate on Titanium: Effect of Soaking Time, Temperature and Solution Refreshing

Abstract

The influence of employing three different solution temperatures (23, 37 and 50 °C), three soaking times (2, 4 and 6 h) and two solution refreshing methods (Refreshed or Non-refreshed) in rapid biomimetic coating process on phase composition, functional groups, coating content and microstructure of the resulted coating was studied. Increasing soaking times and temperature increased the coating content in all cases regardless of the use of refreshed or non-refreshed accelerated calcium phosphate solution. The use of non-refreshed solution resulted in the lower rate of coating than that of refreshed solution at all coating temperatures. However, all coatings similarly comprised octacalcium phosphate and hydroxyapatite as main phases and the microstructure consisted of sharp and interconnected plate-like crystals vertically grown on the surface of titanium. However, two types of crystal structure were produced. Low solution temperature resulted in isolated spheroids while uniform and distributed crystal structure was produced by using high solution temperature. This could be related to the difference in nucleation and precipitation rate formed in rapid biomimetic coating process as a result of the interplay between temperature and ionic strength of the solutions.