Hydroxyapatite coatings adhesion strength

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).

Gas detonation spraying of hydroxyapatite yielded thick coatings with remarkable properties (Klyui et al., 2011). The coating thickness reached during only 20 s of spraying was 280 pm. Adhesion strength to a titanium substrate was up to 80 MPa, and no decomposition phases were observed by XRD. The stems of hip endoprosthetic implants and acetabular cups as well as dental implants... 

In the realm of dentistry, restoration and protection of tooth enamel are of great importance in operative and conservative dentistry. Yamamoto et al. (2013) used PLD to create a freestanding flexible double-layered sheet composed of a 4 pm thin hydroxyapatite (HAp) layer coated with a 0.5 pm thin TCP layer. The adhesive strength between the HAp/TCP sheet and enamel was 5.7 MPa, decidedly higher than that between the monolayered HAp sheet and enamel (1.9 MPa). Electron microscopical observation revealed that the HAp/TCP sheet was largely fused with the enamel. Therefore, the double-layered HAp/TCP sheet can be used as a material to promote the repair of tooth eruption and to maintain healthy dentine. 

Figure 6.2 shows cross-sectional SEM images of coating type I with maximum surface roughness (a), type II with maximum porosity (b) and type III with maximum tensile adhesion strength (c). The (crystalline) phase contents of the as-sprayed coatings are shown in Table 6.5. Coating type I has a maximum hydroxyapatite content of 66 3 mass%, followed by type III with 61 3 mass%. The... 

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).

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

Cheng, I< Zhang, S Weng, W Khor, K.A., Miao, S.P., and Wang, Y.S. (2008) The adhesion strength and residual stress of colloidal-sol gel derived fi-tricalcium phosphate/fluoridated hydroxyapatite biphasic coatings. Thin Solid Films, 516, 3251-3255. 

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. 

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. 

CAS 3290-92-4 EINECS/ELINCS 221-950-4 Uses Monomer for anaerobic adhesives, coatings, high strength cements, and rubber/PVC/mixed polyester-PVC resins modifier, in biomedical field for prosthetic materials with nat. hydroxyapatite and mtg. of dental base resins... 

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