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Electrodeposition of carrier-free 57Co on rhodium as an approach to the preparation of Mössbauer sources
Applied Radiation and Isotopes 69 (2011) 142–145
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
Electrodeposition of carrier-free 57Co on rhodium as an approach to the ¨ preparation of Mossbauer sources Izabela Cieszykowska, Ma"gorzata Z˙o´"towska, Mieczys"aw Mielcarski n Institute of Atomic Energy Polatom, Radioisotope Centre, 05-400 Otwock-S´wierk, Poland
a r t i c l e in f o
a b s t r a c t
Article history: Received 23 March 2010 Received in revised form 7 May 2010 Accepted 1 September 2010
¨ Electrodeposition of carrier-free 57Co on a rhodium matrix as the first step of preparing Mossbauer sources was studied. To optimize the plating parameters, the influences of current density, volume and pH of the electrolyte solution, shape, thickness, and surface area of the rhodium cathode, mode of cathode pretreatment, concentration of 57Co and duration of electrolysis were investigated. & 2010 Elsevier Ltd. All rights reserved.
Keywords: Electroplating 57 Co Rhodium ¨ Mossbauer sources
1. Introduction ¨ Mossbauer spectroscopy requires sources that emit narrow unsplit lines. Most frequently such sources are prepared by deposition of the required radioactive isotope on the surface of the chosen matrix metal followed by diffusion at high temperature into its crystal lattice. For applications that require an unsplit source at 4.2 K, a rhodium matrix is considered as a good choice (Longworth and Window, 1971). In these experiments the metal matrix used was rhodium in the form of thin foils to reduce natural absorption and scattering of the gamma rays due to the thickness of the foil. Well-known methods (Kongstein et al., 2007; Garcia et al., 2008; Santos et al., 2007; Ko"odziej et al., 2002) developed for the electrodeposition of macroquantities of cobalt are inadequate for the deposition of carrier-free isotopes. Such techniques require the deposition of sub-microgram quantities of the isotope from a bulk electrolyte containing no other deliberately introduced metal ions. For the deposition of such minute quantities of cobalt, optimization of the electrolysis parameters is required. From the data reported (Mustachi, 1964; Stephen, 1964; De´zsi and Molna´r, 1967; Gonza´les-Ramı´rez et al., 1993) it follows that for the electrodeposition of 57Co most frequently citrate electrolytes were used. Except ammonium citrate, these electrolytes contained hydrazine hydrate for the reduction of the oxidation products at the anode and ammonia solution for adjusting the pH.
n
Corresponding author. Tel.: + 4822 718 07 06; fax: +4822 718 03 50. E-mail address: [email protected] (M. Mielcarski).
0969-8043/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2010.09.003
In some cases, the electrolytes used (Stephen, 1964) for the deposition of 57Co on different metals contained additionally ammonium sulfate although in other contributions (De´zsi and Molna´r, 1967) it was found to be pointless and even decreased the rate of deposition. The deposition efficiency obtained by Stephen (1964) was 70–80% at current density 100 mA/cm2. Electroplating 57Co onto stainless steel and copper from an electrolyte of similar composition gave an efficiency of 80–90% after 2 h at 10 mA/cm2 (Mustachi, 1964). The yield of deposition on stainless steel obtained by Gonza´les-Ramı´rez et al. (1993) was 74% after the electrolysis lasted up to 25 h at an applied current density of 10–60 mA/cm2. The pH of the electrolytes varied from 5.5 to 11. ¨ Preparation of Mossbauer sources on rhodium matrices is described in two patent documents. Pen’kov and Dobrovol’skij (1997), using a typical electrolyte bath, obtained an efficiency of 89–98% after electrolysis lasting 4–12 h at current density 150 mA/cm2. The rhodium matrix used by Silin (2004) was prepared by sputtering rhodium on graphite or beryllium oxide discs. Except ammonium citrate and hydrazine, the electrolyte solution also contained ammonium sulfate. The current density was 100 mA/cm2, time of electrolysis 2.5 h and efficiency 95–98%. As follows from above, optimization of the electroplating parameters for the deposition of 57Co on rhodium was considered as indispensable. Therefore the influences of current density, volume and pH of the electrolyte, shape, thickness and surface area of the cathode, cathode pretreatment, concentration (activity) of 57Co and time of electrolysis were investigated and are described in this paper.
I. Cieszykowska et al. / Applied Radiation and Isotopes 69 (2011) 142–145
2. Experimental A series of experiments were performed in order to determine the optimal conditions for electrodeposition of cobalt on rhodium foils 6 and 50 mm thick and of different shapes as shown in Fig. 1. In the case of the strip-shaped cathode, only a part of it was immersed in the electrolyte bath so that the surface area exposed for deposition was about 0.5 cm2. Circular cathodes 5 mm in diameter were immersed entirely. The circular cathode shown in Fig. 2b was hot pressed onto the surface of the acrylic support. The electrical contact was assured by a foil strip placed on the reverse side of the disc. Easy separation of these parts proceeds after heating the assembly to about 100 1 C. The clips were made of stainless steel. The composition of alkaline electrolyte was ammonium citrate 25 g/l, hydrazine hydrate 25 g/l and ammonia solution (25%) for adjusting the pH to 10. The acidic electrolyte contained 0.01 M HCl and 0.1 M NaCl in such proportions so as to assure the pH 1–3. The volumes of the electrolytes were 5 and 10 ml. Carrier-free 57Co as Co(II) in 0.1 M HCl solution was used. The specific activity was 259 GBq/mg (7 Ci/mg) and the radioactive concentration 1.85 GBq/ml (50 mCi/ml). The concentrations of cobalt in the electrolytes used in these experiments were 10 5–10 4 mg/ml. The electrolytic cell was a cylindrically shaped glass vial 3 cm in diameter and 3.5 cm in height. A platinum foil was used as the anode.
143
A few methods of cathode pretreatment, comprising etching and pickling (Stephen, 1964; De´zsi and Molna´r, 1967; Mustachi, 1964), were verified. In these experiments for etching a mixture of hydrochloric and sulfuric acid (1:1) was used. Although rhodium is a noble metal, the etching process must be performed carefully so as to avoid over-etching, which can cause deterioration of thin foils. The pretreatment of non-etched rhodium foils was restricted to simple degreasing in an organic solvent and cleaning in a surfactant solution followed by rinsing in deionized water (Gonza´les-Ramı´rez et al., 1993). The deposition rate of 57Co was determined by measuring the gamma-activities of aliquot samples of the electrolyte before, during and after electrolysis in a well-type scintillation chamber. For comparison, the same method was applied for determining the activity of the cathode after deposition under nearly similar geometrical conditions.
3. Results and discussion The deposition rate of 57Co on a rhodium foil 50 mm thick as a function of current density is shown in Fig. 2. As follows from the results obtained, an increase of deposition yield with increasing current density is observed. The efficiencies for 20 and 50 mA/cm2 are basically similar although the rate of deposition at 50 mA/cm2 is a bit higher. After the process lasting 11 h, almost 100% efficiency was achieved. The influence of electrolyte volume on rate of 57Co deposition is shown in Fig. 3. The rate of deposition increases more rapidly when the volume of the electrolyte bath is smaller. A yield of 90% is achieved at twice the rate in a smaller volume of the electrolyte as compared to the greater one. This is perhaps due to the higher concentration of 57Co in the electrolyte of smaller volume. The influence of cobalt concentration on deposition yield is illustrated in Table 1. For higher concentrations, marked with asterisk, stable cobalt traced with 57Co was used, whereas solutions with lower concentrations contained carrier-free 57Co.
Fig. 1. Shapes of rhodium cathodes: (a) strip-shaped, (b) circular shaped on an acrylic support and (c) disc shaped.
Electrodeposition yield [%]
100 80 60 40 electrolyte volume 5ml
20 0
100 Electrodeposition yield [%]
electrolyte volume 10ml
0
5
10
15
20
Time [h]
80
Fig. 3. Influence of electrolyte volume on deposition rate.
60 5 mA/cm2 20 mA/cm2 50 mA/cm2
40 20
Table 1 Effect of cobalt concentration in the electrolyte bath on deposition efficiency. Concentration of cobalt (mg/ml)
0 0
5
10
15
20
25
30
Time [h] Fig. 2. Deposition rate of densities.
57
2.9 10 1.1 10 1.4 10 2.8 10
4 3 3a 3a
Co on a 50 mm thick rhodium foil at different current a
Traced with
57
Co.
Corresponding activity (mCi/ml)
Yield of deposition (%)
10 40 50 100
68 70 89 91
I. Cieszykowska et al. / Applied Radiation and Isotopes 69 (2011) 142–145
100 80
100 Electrodeposition yield [%]
The time of electrolysis was 6.5 h. Slight increase of deposition yield with increasing concentration of cobalt in the electrolyte solution can be observed. It should be mentioned that at higher cobalt concentrations, dark spots on the cathode appeared. A similar effect was reported in other contributions (De´zsi and Molna´r, 1967; Mustachi, 1964). The effect of cathode pretreatment on deposition rate at different current densities is presented in Fig. 4. At current densities 20 and 50 mA/cm2 negligible higher rate of deposition on the etched cathodes is observed. This is presumably due to some degree of surface roughening during etching. Taking into account this insignificant influence on deposition rate, and the risk of deterioration of the thin rhodium foil, the etching step can be omitted. Therefore the pretreatment of the cathode can be limited to degreasing and cleaning. The influence of rhodium foil thickness on deposition rate is shown in Fig. 5. Deposition proceeds faster and with greater yield on the 50 mm thick foil than on the 6 mm one. Rolling to a smaller thickness can cause some changes in the metallurgical state of the thinner foil. Elasticity of the thin foil was greater as compared to that of the thicker foil. It cannot be excluded that overplating at the edges of the thicker foil can contribute to higher deposition yield.
80 60 40 50 µm 6 µm
20 0 5
0
10
Fig. 5. Effect of rhodium cathode thickness on deposition rate of
Co.
100 80 60 40 20
chloride electrolyte solution citrate electrolyte solution
0
5
10
15 Time [h]
40 5mA/cm2
0
5
10
15
20
25
30
Fig. 6. Deposition rates for different electrolytes.
20
Electrodeposition yield [%]
57
0
60
0
20
15
Time [h]
Electrodeposition yield [%]
144
20
Table 2 Effect of rhodium cathode shape on
57
Co deposition yield.
100 80 60
Shape of cathode
Deposition yield (%)
Strip Disc Disc in acryl
89 90 43
40 20mA/cm2
20 0 0
5
10
15
20
100 80 60 40
Rate of deposition of 57Co from different electrolyte solutions is shown in Fig. 6. Definitely lower values have been obtained for a chloride electrolyte (pH 1–3) than for a citrate electrolyte (pH 10). The influence of cathode shape on yield of deposition is shown in Table 2. About twice as much 57Co was deposited on the stripand-disc shaped cathodes than on a disc in an acrylic support. This can be caused by the edge effect resulting in the densification of current flow at the edges of the cathode. The edges of the cathode in the acrylic support are insulated. Such an effect was confirmed by cutting a disc from the strip-shaped cathode after 57Co deposition. The trims after cutting showed higher activity than the disc itself.
50mA/cm2
20
4. Conclusions
0 0
5
10 Time [h]
15
20
Fig. 4. Effect of cathode pretreatment on 57Co deposition rate at different current densities:—’— etched and —~— non-etched.
The experiments performed allow making an optimum choice of the electrodeposition parameters of carrier-free 57Co on rhodium matrices. The highest efficiency approaching 100% and the best rate of deposition were obtained using a citrate
I. Cieszykowska et al. / Applied Radiation and Isotopes 69 (2011) 142–145
electrolyte with pH adjusted to 10 with ammonia. The volume of the electrolyte was 5 ml and the current density 50 mA/cm2. Final verification of the method described above will take place after finishing the experiments comprising thermal diffusion of 57 Co into the structure of the rhodium matrix.
Acknowledgement This work was financially supported by the Polish Ministry of Science and Higher Education within the Research Project R05 0007 04. References ¨ De´zsi, I., Molna´r, B., 1967. On the preparation of 57Co Mossbauer sources. Nuclear Instruments and Methods 54, 105–108. Garcia, E.M., Santos, J.S., Pereira, E.C., Freitas, M.B., 2008. Electrodeposition of cobalt from spent Li-ion battery cathodes by the electrochemistry quartz crystal microbalance technique. Journal of Power Sources 185, 549–553.
145
˜ ez-Regil, E., Gonza´les-Ramı´rez, R., Jime´nez-Domı´nguez, H., Solorza-Feria, O., Ordo´n Cabral-Prieto, A., Bulbulian, S., 1993. Electrodeposition of cobalt on stainless 57 ¨ steel foils. Preparation of Co sources for Mossbauer experiments. Journal of Radioanalytical and Nuclear Chemistry 174, 291–298. Ko"odziej, B., Adamski, Z., W"odek, T., 2002. Investigations on obtaining cathodic cobalt in a diaphragm type electrolyser. Physicochemical Problems of Mineral Processing 36, 289–298. Kongstein, O.E., Haarberg, G.M., Thonstad, J., 2007. Current efficiency and kinetics of cobalt electrodeposition in acid chloride solutions. Part I and II. Journal of Applied Electrochemistry 37, 669–680. ¨ Longworth, G., Window, B., 1971. The preparation of narrow-line Mossbauer sources of 57Co in metallic matrices. Journal of Physics. D 4, 835–839. 57 ¨ Mustachi, A., 1964. The preparation of sources of Co for Mossbauer experiments having narrow unsplit emission lines. Nuclear Instruments and Methods 26, 219–220. ¨ Pen’kov, J.P., Dobrovol’skij, V.F., 1997. Method for producing Mossbauer cobalt-57 source in metal rhodium matrix. Patent document RU 2 084 981. Santos, J.S., Matos, R., Trivinho-Strixino, F., Pereira, E.C., 2007. Effect of temperature on Co electrodeposition in the presence of boric acid. Electrochimica Acta 53, 644–649. ¨ Silin, M.J., 2004. Method for producing Mossbauer source of cobalt-57 in metal matrix. Patent document RU 2 254 629. ¨ Stephen, J., 1964. An electrolytic method of preparing Mossbauer sources and absorbers. Nuclear Instruments and Methods. 26, 269–273.
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
Electrodeposition of carrier-free 57Co on rhodium as an approach to the ¨ preparation of Mossbauer sources Izabela Cieszykowska, Ma"gorzata Z˙o´"towska, Mieczys"aw Mielcarski n Institute of Atomic Energy Polatom, Radioisotope Centre, 05-400 Otwock-S´wierk, Poland
a r t i c l e in f o
a b s t r a c t
Article history: Received 23 March 2010 Received in revised form 7 May 2010 Accepted 1 September 2010
¨ Electrodeposition of carrier-free 57Co on a rhodium matrix as the first step of preparing Mossbauer sources was studied. To optimize the plating parameters, the influences of current density, volume and pH of the electrolyte solution, shape, thickness, and surface area of the rhodium cathode, mode of cathode pretreatment, concentration of 57Co and duration of electrolysis were investigated. & 2010 Elsevier Ltd. All rights reserved.
Keywords: Electroplating 57 Co Rhodium ¨ Mossbauer sources
1. Introduction ¨ Mossbauer spectroscopy requires sources that emit narrow unsplit lines. Most frequently such sources are prepared by deposition of the required radioactive isotope on the surface of the chosen matrix metal followed by diffusion at high temperature into its crystal lattice. For applications that require an unsplit source at 4.2 K, a rhodium matrix is considered as a good choice (Longworth and Window, 1971). In these experiments the metal matrix used was rhodium in the form of thin foils to reduce natural absorption and scattering of the gamma rays due to the thickness of the foil. Well-known methods (Kongstein et al., 2007; Garcia et al., 2008; Santos et al., 2007; Ko"odziej et al., 2002) developed for the electrodeposition of macroquantities of cobalt are inadequate for the deposition of carrier-free isotopes. Such techniques require the deposition of sub-microgram quantities of the isotope from a bulk electrolyte containing no other deliberately introduced metal ions. For the deposition of such minute quantities of cobalt, optimization of the electrolysis parameters is required. From the data reported (Mustachi, 1964; Stephen, 1964; De´zsi and Molna´r, 1967; Gonza´les-Ramı´rez et al., 1993) it follows that for the electrodeposition of 57Co most frequently citrate electrolytes were used. Except ammonium citrate, these electrolytes contained hydrazine hydrate for the reduction of the oxidation products at the anode and ammonia solution for adjusting the pH.
n
Corresponding author. Tel.: + 4822 718 07 06; fax: +4822 718 03 50. E-mail address: [email protected] (M. Mielcarski).
0969-8043/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2010.09.003
In some cases, the electrolytes used (Stephen, 1964) for the deposition of 57Co on different metals contained additionally ammonium sulfate although in other contributions (De´zsi and Molna´r, 1967) it was found to be pointless and even decreased the rate of deposition. The deposition efficiency obtained by Stephen (1964) was 70–80% at current density 100 mA/cm2. Electroplating 57Co onto stainless steel and copper from an electrolyte of similar composition gave an efficiency of 80–90% after 2 h at 10 mA/cm2 (Mustachi, 1964). The yield of deposition on stainless steel obtained by Gonza´les-Ramı´rez et al. (1993) was 74% after the electrolysis lasted up to 25 h at an applied current density of 10–60 mA/cm2. The pH of the electrolytes varied from 5.5 to 11. ¨ Preparation of Mossbauer sources on rhodium matrices is described in two patent documents. Pen’kov and Dobrovol’skij (1997), using a typical electrolyte bath, obtained an efficiency of 89–98% after electrolysis lasting 4–12 h at current density 150 mA/cm2. The rhodium matrix used by Silin (2004) was prepared by sputtering rhodium on graphite or beryllium oxide discs. Except ammonium citrate and hydrazine, the electrolyte solution also contained ammonium sulfate. The current density was 100 mA/cm2, time of electrolysis 2.5 h and efficiency 95–98%. As follows from above, optimization of the electroplating parameters for the deposition of 57Co on rhodium was considered as indispensable. Therefore the influences of current density, volume and pH of the electrolyte, shape, thickness and surface area of the cathode, cathode pretreatment, concentration (activity) of 57Co and time of electrolysis were investigated and are described in this paper.
I. Cieszykowska et al. / Applied Radiation and Isotopes 69 (2011) 142–145
2. Experimental A series of experiments were performed in order to determine the optimal conditions for electrodeposition of cobalt on rhodium foils 6 and 50 mm thick and of different shapes as shown in Fig. 1. In the case of the strip-shaped cathode, only a part of it was immersed in the electrolyte bath so that the surface area exposed for deposition was about 0.5 cm2. Circular cathodes 5 mm in diameter were immersed entirely. The circular cathode shown in Fig. 2b was hot pressed onto the surface of the acrylic support. The electrical contact was assured by a foil strip placed on the reverse side of the disc. Easy separation of these parts proceeds after heating the assembly to about 100 1 C. The clips were made of stainless steel. The composition of alkaline electrolyte was ammonium citrate 25 g/l, hydrazine hydrate 25 g/l and ammonia solution (25%) for adjusting the pH to 10. The acidic electrolyte contained 0.01 M HCl and 0.1 M NaCl in such proportions so as to assure the pH 1–3. The volumes of the electrolytes were 5 and 10 ml. Carrier-free 57Co as Co(II) in 0.1 M HCl solution was used. The specific activity was 259 GBq/mg (7 Ci/mg) and the radioactive concentration 1.85 GBq/ml (50 mCi/ml). The concentrations of cobalt in the electrolytes used in these experiments were 10 5–10 4 mg/ml. The electrolytic cell was a cylindrically shaped glass vial 3 cm in diameter and 3.5 cm in height. A platinum foil was used as the anode.
143
A few methods of cathode pretreatment, comprising etching and pickling (Stephen, 1964; De´zsi and Molna´r, 1967; Mustachi, 1964), were verified. In these experiments for etching a mixture of hydrochloric and sulfuric acid (1:1) was used. Although rhodium is a noble metal, the etching process must be performed carefully so as to avoid over-etching, which can cause deterioration of thin foils. The pretreatment of non-etched rhodium foils was restricted to simple degreasing in an organic solvent and cleaning in a surfactant solution followed by rinsing in deionized water (Gonza´les-Ramı´rez et al., 1993). The deposition rate of 57Co was determined by measuring the gamma-activities of aliquot samples of the electrolyte before, during and after electrolysis in a well-type scintillation chamber. For comparison, the same method was applied for determining the activity of the cathode after deposition under nearly similar geometrical conditions.
3. Results and discussion The deposition rate of 57Co on a rhodium foil 50 mm thick as a function of current density is shown in Fig. 2. As follows from the results obtained, an increase of deposition yield with increasing current density is observed. The efficiencies for 20 and 50 mA/cm2 are basically similar although the rate of deposition at 50 mA/cm2 is a bit higher. After the process lasting 11 h, almost 100% efficiency was achieved. The influence of electrolyte volume on rate of 57Co deposition is shown in Fig. 3. The rate of deposition increases more rapidly when the volume of the electrolyte bath is smaller. A yield of 90% is achieved at twice the rate in a smaller volume of the electrolyte as compared to the greater one. This is perhaps due to the higher concentration of 57Co in the electrolyte of smaller volume. The influence of cobalt concentration on deposition yield is illustrated in Table 1. For higher concentrations, marked with asterisk, stable cobalt traced with 57Co was used, whereas solutions with lower concentrations contained carrier-free 57Co.
Fig. 1. Shapes of rhodium cathodes: (a) strip-shaped, (b) circular shaped on an acrylic support and (c) disc shaped.
Electrodeposition yield [%]
100 80 60 40 electrolyte volume 5ml
20 0
100 Electrodeposition yield [%]
electrolyte volume 10ml
0
5
10
15
20
Time [h]
80
Fig. 3. Influence of electrolyte volume on deposition rate.
60 5 mA/cm2 20 mA/cm2 50 mA/cm2
40 20
Table 1 Effect of cobalt concentration in the electrolyte bath on deposition efficiency. Concentration of cobalt (mg/ml)
0 0
5
10
15
20
25
30
Time [h] Fig. 2. Deposition rate of densities.
57
2.9 10 1.1 10 1.4 10 2.8 10
4 3 3a 3a
Co on a 50 mm thick rhodium foil at different current a
Traced with
57
Co.
Corresponding activity (mCi/ml)
Yield of deposition (%)
10 40 50 100
68 70 89 91
I. Cieszykowska et al. / Applied Radiation and Isotopes 69 (2011) 142–145
100 80
100 Electrodeposition yield [%]
The time of electrolysis was 6.5 h. Slight increase of deposition yield with increasing concentration of cobalt in the electrolyte solution can be observed. It should be mentioned that at higher cobalt concentrations, dark spots on the cathode appeared. A similar effect was reported in other contributions (De´zsi and Molna´r, 1967; Mustachi, 1964). The effect of cathode pretreatment on deposition rate at different current densities is presented in Fig. 4. At current densities 20 and 50 mA/cm2 negligible higher rate of deposition on the etched cathodes is observed. This is presumably due to some degree of surface roughening during etching. Taking into account this insignificant influence on deposition rate, and the risk of deterioration of the thin rhodium foil, the etching step can be omitted. Therefore the pretreatment of the cathode can be limited to degreasing and cleaning. The influence of rhodium foil thickness on deposition rate is shown in Fig. 5. Deposition proceeds faster and with greater yield on the 50 mm thick foil than on the 6 mm one. Rolling to a smaller thickness can cause some changes in the metallurgical state of the thinner foil. Elasticity of the thin foil was greater as compared to that of the thicker foil. It cannot be excluded that overplating at the edges of the thicker foil can contribute to higher deposition yield.
80 60 40 50 µm 6 µm
20 0 5
0
10
Fig. 5. Effect of rhodium cathode thickness on deposition rate of
Co.
100 80 60 40 20
chloride electrolyte solution citrate electrolyte solution
0
5
10
15 Time [h]
40 5mA/cm2
0
5
10
15
20
25
30
Fig. 6. Deposition rates for different electrolytes.
20
Electrodeposition yield [%]
57
0
60
0
20
15
Time [h]
Electrodeposition yield [%]
144
20
Table 2 Effect of rhodium cathode shape on
57
Co deposition yield.
100 80 60
Shape of cathode
Deposition yield (%)
Strip Disc Disc in acryl
89 90 43
40 20mA/cm2
20 0 0
5
10
15
20
100 80 60 40
Rate of deposition of 57Co from different electrolyte solutions is shown in Fig. 6. Definitely lower values have been obtained for a chloride electrolyte (pH 1–3) than for a citrate electrolyte (pH 10). The influence of cathode shape on yield of deposition is shown in Table 2. About twice as much 57Co was deposited on the stripand-disc shaped cathodes than on a disc in an acrylic support. This can be caused by the edge effect resulting in the densification of current flow at the edges of the cathode. The edges of the cathode in the acrylic support are insulated. Such an effect was confirmed by cutting a disc from the strip-shaped cathode after 57Co deposition. The trims after cutting showed higher activity than the disc itself.
50mA/cm2
20
4. Conclusions
0 0
5
10 Time [h]
15
20
Fig. 4. Effect of cathode pretreatment on 57Co deposition rate at different current densities:—’— etched and —~— non-etched.
The experiments performed allow making an optimum choice of the electrodeposition parameters of carrier-free 57Co on rhodium matrices. The highest efficiency approaching 100% and the best rate of deposition were obtained using a citrate
I. Cieszykowska et al. / Applied Radiation and Isotopes 69 (2011) 142–145
electrolyte with pH adjusted to 10 with ammonia. The volume of the electrolyte was 5 ml and the current density 50 mA/cm2. Final verification of the method described above will take place after finishing the experiments comprising thermal diffusion of 57 Co into the structure of the rhodium matrix.
Acknowledgement This work was financially supported by the Polish Ministry of Science and Higher Education within the Research Project R05 0007 04. References ¨ De´zsi, I., Molna´r, B., 1967. On the preparation of 57Co Mossbauer sources. Nuclear Instruments and Methods 54, 105–108. Garcia, E.M., Santos, J.S., Pereira, E.C., Freitas, M.B., 2008. Electrodeposition of cobalt from spent Li-ion battery cathodes by the electrochemistry quartz crystal microbalance technique. Journal of Power Sources 185, 549–553.
145
˜ ez-Regil, E., Gonza´les-Ramı´rez, R., Jime´nez-Domı´nguez, H., Solorza-Feria, O., Ordo´n Cabral-Prieto, A., Bulbulian, S., 1993. Electrodeposition of cobalt on stainless 57 ¨ steel foils. Preparation of Co sources for Mossbauer experiments. Journal of Radioanalytical and Nuclear Chemistry 174, 291–298. Ko"odziej, B., Adamski, Z., W"odek, T., 2002. Investigations on obtaining cathodic cobalt in a diaphragm type electrolyser. Physicochemical Problems of Mineral Processing 36, 289–298. Kongstein, O.E., Haarberg, G.M., Thonstad, J., 2007. Current efficiency and kinetics of cobalt electrodeposition in acid chloride solutions. Part I and II. Journal of Applied Electrochemistry 37, 669–680. ¨ Longworth, G., Window, B., 1971. The preparation of narrow-line Mossbauer sources of 57Co in metallic matrices. Journal of Physics. D 4, 835–839. 57 ¨ Mustachi, A., 1964. The preparation of sources of Co for Mossbauer experiments having narrow unsplit emission lines. Nuclear Instruments and Methods 26, 219–220. ¨ Pen’kov, J.P., Dobrovol’skij, V.F., 1997. Method for producing Mossbauer cobalt-57 source in metal rhodium matrix. Patent document RU 2 084 981. Santos, J.S., Matos, R., Trivinho-Strixino, F., Pereira, E.C., 2007. Effect of temperature on Co electrodeposition in the presence of boric acid. Electrochimica Acta 53, 644–649. ¨ Silin, M.J., 2004. Method for producing Mossbauer source of cobalt-57 in metal matrix. Patent document RU 2 254 629. ¨ Stephen, J., 1964. An electrolytic method of preparing Mossbauer sources and absorbers. Nuclear Instruments and Methods. 26, 269–273.