Hydroxyapatite coatings, measurement

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). 

Residual stress measurement in thermal sprayed hydroxyapatite coatings. 

Figure 7.23 Concentration of Ca2+ and P043 ions and pH development measured in protein-free SBF during incubation of plasma-sprayed hydroxyapatite coatings (Gotze et ai, 2001).

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...

Photoluminescence piezospectroscopy is an accurate measurement method to determine nanoscale stress distributions and surface defects that control device performance and reliability, that is performance over the service life of biomaterials such as hydroxyapatite coatings and implants. 

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

The effect of residual stress on the dissolution of hydroxyapatite coatings was investigated on plasma-sprayed coatings of 80, 110 and 200 pm thickness (Han, Xu and Lu, 2001). Residual stresses in the coatings were measured with a holedrilling method. Dissolution of the coatings was monitored along with an examination of the phase composition. The results showed that both tensile residual... 

Fahad Hasan, Wang and Berndt (2014) investigated the Vickers microhardness of the cross- section as well as the top surface of plasma-sprayed polished hydroxyapatite coatings. The effects of applied load, measurement direction and indent location (Figure 7.55) on the microhardness were investigated. Indentation was performed on dense and porous areas of the coatings. After Vickers indentation,... 

Lodini, A. (2004) Thermal residual stresses near the interface between hydroxyapatite coating and titanium substrate finite element analysis and synchrotron radiation measurements. /. Biomed. Mater. Res. Part A, 70, 20-27. 

Fogarassy, P., Cofino, B., Millet, P., and Lodini, A. (2005) Residual stress in hydroxyapatite coating nonlinear analysis and high energy synchrotron measurements. IEEE Trans. Biomed. Eng., 22 (7), 1161-1166. 

Yang, Y.C. and Chang, E. (2005) Measurement of residual stresses in plasma-sprayed hydroxyapatite coatings on titanium alloy. Surf. Coat. Technol., 190... 

An SEM equipped with EDS and ultra-thin window SiLi detector was used for X-ray measurement of electrodeposited hydroxyapatite coatings on Ti6Al4V substrates [57]. X-ray spectra were acquired at a primary beam energy of 30 kV, a current of 5nA and an acquisition time of 180 s. The stoichiometric molar ratio for pure hydroxyapatite is 1.67. X-ray spectra captured in this work showed CaP ratios of 1.51 corresponding to a Ca-deficient hydroxyapatite. 

Kurzweg, H., Heimann, R.B., Troczynski, T., (1998), Adhesion of thermally sprayed hydroxyapatite-bond-coat systems measured by a novel peel test , J. Mat. Sci. Med., 9(1), 9-16. 

Separation for measurement The basis of measurement depends on the ability to separate the unbound or free" Ag from the Ab-Ag complex, which itself relies on differences in properties between the two components while maintaining (that is not disrupting) the Ab-Ag complex (Figure 10.6). There are a number of reagents used for separation including charcoal, hydroxyapatite, ammonium sulfate and polyethylene glycol, but the method that will be considered here relies on the use of dextran-coated activated charcoal (see Figure 10.7). With inherent... 

To counteract the high corrosion rate of Mg alloy implants electrochemically deposited coatings of fluorine-doped hydroxyapatite (FHAp) and brushite (DCPD) were developed by Bakhsheshi-Rad et al. (2014). As shown in Table 5.2 potentiodynamic polarisation measurements of uncoated and coated Mg-Ca alloys subjected to electrochemical corrosion in Kokubo s SBF (Table 7.8) confirmed the corrosion-resistant nature of the coatings. The anodic polarisation curve of the uncoated specimen shows a breakdown immediately after the... 

The scratch test is a standard method to provide a measure of the coating-to-substrate adhesion and was found to be a useful method to test thin HAp coatings deposited on implant surfaces. Forsgren et al. (2007) estimated the critical load of a biomimetically deposited hydroxyapatite layer on a cp-Ti substrate to be 2.4 O.IGPa. 

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