Highly adhesive calcium phosphate layer on UHMWPE prepared by IBAD

A study has been made on adhesive strength and chemical states of calcium phosphate layer deposited on the surface of ultra-high molecular weight polyethylene (UHMWPE) by ion beam assisted deposition (IBAD). IBAD is well known to be able to give an atomic intermixed zone at layer/substrate interface during deposition. The X-ray diffraction (XRD) results demonstrated that the main structure is amorphous calcium phosphate (ACp) in the layer. Tape test and scratch test were used to measure the adhesive strength between layer and substrate. Both results show that the adhesive strength between layer and substrate of samples prepared by IBAD is much stronger than that of contrast samples prepared by ion beam sputtering deposition (IBSD). It has been found by XPS that there are much more stable covalent bonds between layer and substrate in IBAD samples than that in IBSD samples. The results above lead us to a conclusion that besides the atomic intermixed zone at the interface, the increment of covalent bonds between layer and substrate also enhanced the adhesive strength between layer and substrate in IBAD samples.