## 3 Results  
The surface of the D1 and D2 Ti4 Al4 Zr samples, processed through chemical roughening, were investigated using electron microscopy; Figure 2 presents the surface of the samples after chemical attack: (a,b) sample D1 and (c,d) sample D2. The samples were also analyzed and characterized from a 3D point of view using the analysis software VegaTescan. These results are presented in Table 1. The software analysis was able to detect modifications of the surface different from those obtainable by mechanical means. The microscopy results revealed partial contamination of the surface with impurities following the chemical attack of the surface, although these impurities were not stable on the metallic surface and were easily removed via alcohol washing. Figure 2: SEM micrographs of the sample surfaces: (**a**) sample D1-500x, (**b**) sample D1-5000x, (**c**) sample D2-500x, and (**d**) sample D2-5000x. The chemical analysis of the surfaces did not reveal the contamination of the material surface; the traces of chemical attack were removed via a wash with distilled water. The modifications of the Ti\(A\)Al4 Zr sample surface through chemical processes can be classified into two types: those that modify the surface at the micron level (D1) and those that modify the surface at the nanometric level (D2). The layers of HA deposited on the metallic material were of the level of microns (5-10 \(\upmu\)m), which led to an influence of its properties at this level. The surfaces engraved at the nanometric level were more appropriate for nanometric layers and those at micron sizes for micron layers, which can cover and homogenize the surface after deposition. Figure 3 presents the 3D microscopy images of the samples' chemically treated surfaces. Using the 3D microscopes, the performance of the chemical attack methods was assessed. This information is organized in Table 1 (including the minimum, medium, and maximum depths of the traces on the surface). The effects of the chemical etching were observed on sample D1 at a maximum 6.33 \(\upmu\)m depth in an isolated case, with all the other samples having values between 0.81 and 2.4 \(\upmu\)m. The standard deviations were at the submicron level and confirmed a good general homogenization of the sample via the chemical processing applied on the surface. Figure 3c,d presents the surface state in terms of the distribution of luminous intensity (surface roughness indicator) on the chemically processed metallic surface. The associated values are shown in Table 1. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Sample/Dimensions** & \multicolumn{4}{c}{**Radius (\(\upmu\)m)**} & \multicolumn{4}{c}{**Area (\(\upmu\)m\({}^{2}\))**} \\
**(from 2D images)** & **min** & **med** & **max** & **StDev** & **min** & **med** & **max** & **StDev** \\ \hline D1 & 1.86 & 3.19 & 4.79 & 0.74 & 10.83 & 33.70 & 72.18 & 15.87 \\ D2 & 1.24 & 2.41 & 5.44 & 0.71 & 4.87 & 19.91 & 92.97 & 13.87 \\ \hline
**Sample/Dimensions** & \(\mathbf{H_{min}}\) & \(\mathbf{H_{med}}\) & \(\mathbf{H_{max}}\) & **StDev** & **Minimum variation** & **Maximum variation** & **Differences variation** (ADU)** & **(ADU)** \\ \hline D1 & 2.38 & 3.90 & 6.33 & 1.01 & 60 & 68.5 & 8.5 \\ D2 & 1.08 & 1.33 & 1.87 & 0.21 & 59.6 & 63.4 & 3.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Surface characteristics of samples D1 and D2 (values were obtained from Figure 3 using VegaT software). Figure 3: 3D images of sample surfaces: (**a**) D1 and (**b**) D2. Surface roughness distribution: (**c**) D1 and (**d**) D2. Figure 3 also shows a noticeably compact longitudinal distribution of the surfaces modified through a chemical attack in the case of sample D2, while sample D1 showed deeper effects and a greater roughness. The surface state influences the quality of the deposited HA layers through an electrophoretic process based on the correlation between the surface roughness and the layer thickness [21; 22].