Adhesion hydroxyapatite coatings

X-ray radiography of nickel-coated fibers, surface atoms of hydroxyapatite, coating analysis of silane treated hydroxyapatite, and composition of the failure area of an adhesive joint between rubber and metal. This review of applications shows that carbon fibers are the most frequently tested material by XPS. 

Kim etal. (1998) deposited about 0.5 pm thick homogeneous and dense hydroxyapatite coatings by IBAD on a-alumina substrates. The ACP layer crystallised to dense HAp after annealing at 500 °C for 2 h and immersion in deionised water for 72 h at room temperature. The adhesive strength between HAp and the a-alumina substrate was measured by a scratch test and the critical load was found to be around 43 N (4300 gf). The ion-beam sputtered coatings were used as control samples. The adhesion was found to be worse for IBSD than for IBAD. Indeed, using IBSD the critical load of HAp on alumina was measured to be only about 39 N (3900 gf). 

Table 5.4 Tensile adhesion strength (ASTM C633-13) of LPPS (VPS) hydroxyapatite coatings Cl (deposited from as-received powder) and C2 (deposited from powder sintered for 1 h at 1300°C) as a function of immersion time in HBSS (n = 5) (Heimann and Vu, 1997).

K. (2009) Adhesion study of pulsed laser deposited hydroxyapatite coating on laser surface nitrided titanium. Thin Solid Films, 517, 5496-5501. 

Adhesion of Plasma-Sprayed Hydroxyapatite Coatings 7.5.2.1 Modified Peel Test According to ASTM D3167-10... 

The procedure to evaluate adhesion strength of plasma-sprayed hydroxyapatite coatings has been described earlier. The presence of a thin plasma-sprayed titania bond coat (see Chapter 6.3.2.2) considerably enhances the adhesion strength to a Ti6Al4V substrate of titania/HAp tandem coatings compared to HAp coatings without a bond coat. 

Figure 7.32 Peel adhesion strength of plasma-sprayed hydroxyapatite coating on a Ti6AI4V foil without (circles) and with a titania bond coat (crosses). The size of the symbols reflect the statistical error of the measurements. Extension of the regression...

Based on its apparent simplicity, scratch testing is frequently applied to estimate the cohesive and adhesion bond strengths of hydroxyapatite coatings (for example Arias et al., 2003 Zhang et al., 2006 Dudek and Adamczyk, 2013). However, the interpretation of the recorded traces is difficult as the test results are affected by scores of intrinsic and extrinsic parameters that tend to falsify the conclusion drawn. 

Figure 7.40 Development of all-through cracks in a plasma-sprayed hydroxyapatite coating of about 200 pm thickness, 10 0.5 pm average surface roughness (fta), 5 1% porosity and 50 9 MPa tensile adhesion strength (Heimann et at., 2001).

Figure 7.49 Relation between adhesive failure and compressive residual stresses of plasma-sprayed hydroxyapatite coatings on Ti6AI4V. (Adapted from Yang and Chang (2001).)...

Measurements of residual stress and strain, Young s modulus and adhesive bonding strength of the hydroxyapatite coating after immersion in HBSS showed... 

Khor, K.A., Nivard, M., Berthe, L., Cuq-Lelandais, J.P., and Boustie, M. (2010) Bond strength determination of hydroxyapatite coatings on Ti-6A1-4V substrates using the Laser Shock Adhesion Test (LASAT). /. Biomed. Mater. Res. A, 95 (4), 1096-1104. 

A.R. (2014) Comparative investigation on the adhesion of hydroxyapatite coating on H-6A1-4V implant a review paper. Int. J. Adhes. Adhes., 48, 238—257. 

Yang, S., Man, H.C., Xing, W., and Zheng, X.B. (2009) Adhesion strength of plasma-sprayed hydroxyapatite coatings on laser gas nitrided pure titanium. Surf. Coat. Technol., 203 (20-21), 3116-3122. 

Zhang, S., Zong, X.T., Wang, Y.S., Cheng, I<., and Weng, W.J. (2006) Adhesion strength of sol-gel derived fluoridated hydroxyapatite coatings. Surf. Coat. Technol., 200 (22-23), 6350-6354. 

Hydroxyapatite coatings prepared by plasma spraying typically contain considerable amounts of amorphous calcium phosphate and small amounts of other crystalline phases. Heat treating the coating can increase crystallinity and also improve the adhesion to the substrate. However, this process is not usually done because of economic factors and concerns about the adverse effects it might have on the mechanical properties of the substrate. 

Implants are coated with hydroxyapatite to obtain biomimetically grown hydroxyapatite coating. The number of nucleation sites in HA composition is important not with the focus of speeding up the process, but to increase the coating adhesion and/or to change the textrrre and morphology of the coating. The microwave catalyzes the HA nucleation and results in the faster HA crystal formation. ... 

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