## 3 Results and Discussion
### Characterization  
After the CaP solution was treated with LAB, CaP crystals were found on the surface. In addition, it was found that holes of different sizes affected the crystal shape and size (Figure 2). In pure titanium and alkali-treated test pieces, flake-like CaP crystals were observed, which was similar to the results of [PERSON] et al. [32]. CaP crystals treated with the same alkalinity were smaller than those of pure titanium, which may have been caused by the influence of nanopores on the surface of the test piece. CaP observed on the surface after anodization showed a plate-like crystal structure. CaP formed on the surface after acid treatment presented a flower-like crystal structure composed of needle-like crystals. The morphology of HA with different crystal structures is consistent with that reported by [PERSON] et al. [33]. LAB treatment of titanium flakes soaked in a CoHA solution showed different CoHA crystals (Figure 2). No crystals were observed on the untreated titanium piece. After anodic oxidation, it was observed that CoHA in the form of plate-like aggregates was consistent with the CaP synthesized by a hydrothermal method [34]. Surfaces treated with NaOH and those with HCl respectively exhibited flaky and plate-like crystal structures. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Atomic\%**} & \multicolumn{1}{c}{**C**} & \multicolumn{1}{c}{**Ti**} & \multicolumn{1}{c}{**O**} & \multicolumn{1}{c}{**Na**} & \multicolumn{1}{c}{**F**} & \multicolumn{1}{c}{**Ca**} & \multicolumn{1}{c}{**P**} & \multicolumn{1}{c}{**Ca/P**} & \multicolumn{1}{c}{**Co**} & \multicolumn{1}{c}{**Ca + Co/P**} \\ \hline \multirow{4}{*}{Original} & Ti & 12.88 & 87.12 & - & - & - & & & & & \\  & TNT & 7.92 & 29.83 & 48.57 & - & 13.68 & & & & & \\  & NaOH & 5.61 & 31.45 & 58.91 & 4.03 & - & & & & & \\  & HCl & - & 100 & - & - & - & & & & & \\ \hline \multirow{4}{*}{LAB} & Ti & 11.50 & 83.93 & 1.65 & - & - & 1.5 & 1.4 & 1.07 & & \\  & TNT & 3.00 & 16.10 & 37.16 & - & - & 2.18 & 1.81 & 1.20 & & \\  & NaOH & 7.01 & 6.69 & 68.32 & 1.14 & - & 8.65 & 7.37 & 1.17 & & \\  & HCl & 3.67 & 18.42 & 63.95 & - & - & 7.46 & 6.50 & 1.15 & & \\ \hline \multirow{4}{*}{CoHA solution} & Ti & 13.23 & 86.77 & - & - & - & - & - & - & - & - \\  & TNT & - & - & 69.31 & 1.50 & - & 12.52 & 15.81 & 0.79 & 0.41 & 0.82 \\ \cline{1-1}  & NaOH & - & - & 68.06 & 1.82 & - & 12.97 & 15.68 & 0.83 & 0.65 & 0.87 \\ \cline{1-1}  & HCl & 0.61 & - & 68.27 & 3.14 & - & 11.19 & 13.17 & 0.85 & 0.66 & 0.90 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Surface element analysis of the titanium sheet with different surface treatments and samples after LAB treatments by EDX. Surface element compositions of groups of CaP solution-treated titanium sheets were analyzed by EDX. The surface was mainly composed of oxygen, calcium, and phosphorus, which indicated that HA was deposited on the surface of the titanium sheet after LAB irradiation. The test piece treated with the CoHA solution, and LAB also revealed the presence of cobalt. This proved to be cobalt-containing HA crystals. Calculating the Ca/P ratio on the surface showed that Ca/P ratios of the CP solution and the CoHA solution were both \(<\)1.67, and both were calcium-deficient HA. Previous studies indicated that calcium-deficient hydroxyapatite have higher degradability. They are easily degraded in the body, allowing absorption by surrounding tissues [35]. Functional groups on the surface of the evaluation test pieces were analyzed by ATR-FTIR. No group had characteristic peaks of HA before LAB treatment (Figure 5A). After anodization treatment, tensile vibrations of amino groups (NH\({}_{3}\)\({}^{+}\)) were detected at 1072 and 1058 cm\({}^{-1}\) on titanium [36]. Peaks observed at 869 and 970 cm\({}^{-1}\) after alkali treatment were Ti-OH groups. This was the result of ion exchange between sodium titanate and H\({}_{3}\)O\({}^{+}\) produced during alkali treatment [37].