## 3 Results and Discussion
### Electro-Precipitation Efficiency  
The alpha-particle activity of \({}^{241}\)Am deposited was further measured. This value was calculated to 49.7 and 59.7% for \({}^{241}\)Am deposited in Na\({}_{2}\)SO\({}_{4}\) electrolyte solutions onto stainless steel and BDD respectively (see in Table 2, row a). This slight difference in the precipitation yield could be explained by the fact that there is a slight pH difference (3.97 vs. 3.85) for stainless steel and diamond, respectively. With the same current density applied, a less acidic pH induces a thicker hydroxyl layer, making actinide diffusion lesser on the cathode and thus lower precipitation efficiency [48]. Very close electro-precipitation efficiency values (71 and 70%) could be achieved in NaNO\({}_{3}\) electrolyte for BDD and stainless steel substrates (see in Table 2, row b). Generally, a slightly higher efficiency is observed when NaNO\({}_{3}\) is used with respect to Na\({}_{2}\)SO\({}_{4}\); even when the precipitation processes are onto either diamond or stainless steel substrate (Table 2) or even onto BDD film combined with a silicon detector in an ActiFind device [35]. This result confirms that BDD can be used as an alternative material for efficient electro-precipitation and that NaNO\({}_{3}\) electrolyte enables a higher efficiency than Na\({}_{2}\)SO\({}_{4}\) solution.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Experiment**} & \multirow{2}{*}{**Electrolyte**} & \multicolumn{3}{c}{**FWHM (keV)**} \\ \cline{3-5}  & & **Stainless Steel** & **BDD** & **Standard** \\ \hline
1 & Na\({}_{2}\)SO\({}_{4}\) & 13.8 & 13.2 & 12 \\ \hline
2 & NaNO\({}_{3}\) & 12.5 & 14.5 & 12 \\ \hline \hline \end{tabular}
\end{table}
Table 1: FWHM of 5.96 Bq \({}^{241}\)Am electro-precipitated for t = 90 min: (1) 0.3 M Na\({}_{2}\)SO\({}_{4}\) pH 3.97 electrolyte, current density = 8 mA.cm\({}^{-2}\), and (2) 0.3 M Na\({}_{2}\)SO\({}_{4}\) pH 3.0 electrolyte, current density = 3.3 mA.cm\({}^{-2}\), t = 90 min.  
Figure 6: Typical alpha-particle spectra: (**A**) \({}^{241}\)Am 5.96 Bq electro-precipitated in 0.3 M Na\({}_{2}\)SO\({}_{4}\) electrolyte solution at pH 3.85 with a current density of 8 mA.cm\({}^{-2}\) onto BDD during 90 min; (**B**) mixture of \({}^{239}\)Pu 5.13 Bq, \({}^{241}\)Am 5.96 Bq and \({}^{244}\)Cm 4.40 Bq electro-precipitated onto doped diamond substrate for 120 min in 0.3 M Na\({}_{2}\)SO\({}_{4}\) pH 4.0 electrolyte solution with a current density of 5 mA.cm\({}^{-2}\).  
Furthermore, electro-precipitation of actinides mixtures (\({}^{239}\)Pu, \({}^{241}\)Am, and \({}^{244}\)Cm) was also investigated onto BDD substrates for varying durations. Precipitation efficiencies were displayed in Figure 7 for both Na\({}_{2}\)SO\({}_{4}\) and NaNO\({}_{3}\) electrolytes. The result demonstrated that the precipitation efficiency values are approximately similar for \({}^{241}\)Am and \({}^{244}\)Cm in either Na\({}_{2}\)SO\({}_{4}\) or NaNO\({}_{3}\) and are slightly higher than for \({}^{239}\)Pu. The low precipitation yield of \({}^{239}\)Pu could be attributed to the complex chemistry of Pu existing in many oxidation states (III, IV, V, VI) in solution. Again, the result demonstrated a slightly more efficient precipitation in NaNO\({}_{3}\) than in Na\({}_{2}\)SO\({}_{4}\) electrolyte. The precipitation efficiency could be improved up more than 80% for \({}^{241}\)Am and \({}^{244}\)Cm and more than 40% for \({}^{239}\)Pu in NaNO\({}_{3}\) electrolyte solution after 2 h of precipitation.