Zn- Co (1)

Journal of Electroanalytical Chemistry 505 (2001) 5461www.elsevier.nl/locate/jelechem

Characterisation of zinc+cobalt alloy phases obtained byelectrodeposition

E. Gomez a, X. Alcobe b, E. Valles a,*a Laboratori de Cie`ncia i Tecnologia Electroqumica dels Materials (LCTEM), Departament de Qumica Fsica, Uniersitat de Barcelona,

Mart i Franque`s 1, 08028 Barcelona, Spainb Sereis Cientificote`cnics, Uniersitat de Barcelona, Lluis Sole i Sabaris 1-3, 08028 Barcelona, Spain

Received 8 November 2000; received in revised form 12 February 2001; accepted 20 February 2001

Abstract

The anomalous codeposition of Zn+Co alloys on vitreous carbon, copper and nickel substrates in a chloride bath was studied.The results indicate that the substrate influences both the initial electrodeposition stages and the alloy formation. For the sameelectrodeposition conditions, vitreous carbon and copper substrates favour the formation of deposits richer in zinc than thoseobtained over a nickel substrate. In the stripping analysis of deposits obtained during anomalous codeposition, up to three majoroxidation peaks were observed, the two corresponding to the more negative potentials are attributable to the zinc oxidation in thealloy and the more positive one to the oxidation of the remaining porous cobalt matrix of the alloy. Under our experimentalconditions, two kinds of deposits have been analysed using X-ray diffraction (XRD). XRD analysis showed that deposits withvery low cobalt percentage (less than 3%) and a hexagonal platelet structure had a distorted hcp zinc -phase. Polyhedral-graineddeposits with between 4 and 10% cobalt were made up of quasi-pure zinc and a Zn+Co -phase of bcc structure. A correlationbetween the stripping curve and the type of deposit has been found. 2001 Elsevier Science B.V. All rights reserved.

Keywords: Zinccobalt alloys; Electrodeposition; X-ray diffraction; Stripping; Anomalous codeposition

1. Introduction

Zn+Co coatings have attracted interest becausetheir corrosion resistance is higher than that of purezinc coatings, the improvement in corrosion resistancebeing similar to that of the Zn+Ni alloy, with theadded advantage that only about 1 wt% Co is necessary[17].

In our laboratory, the Zn+Co alloy deposition onvitreous carbon from chloride solutions with low totalmetal concentration has been studied [810]. Zinc-richalloy phases were favoured by low potentials (i.e. lownegative current densities), high [Zn(II)]/[Co(II)] ratiosin solution, and stirring. Stripping analysis, morpholog-ical and compositional analysis and a comparison withrelated studies of the same or similar alloys [11] allowedus to relate tentatively the different stripping peaks todifferent types of deposits obtained.

It is well known that the codeposition of zinc withiron-group metals is anomalous, preferential depositionof zinc being observed under a wide range of conditions[12]. Considerable efforts have been made to determinethe cause of this anomaly, the hydroxide suppressionmechanism [13], already proposed for Zn+Ni deposi-tion [14], appearing to be most popular. In this modelanomalous deposition occurs due to the formation andadsorption of a zinc hydroxide film which inhibitscobalt electrodeposition while favouring that of zinc.However, with vitreous carbon the formation of zinchydroxides and their initial adsorption is uncertain. Ina previous paper we analysed the very initial stages ofdeposition, and the results suggested that an initialdeposition of cobalt did not progress as a consequenceof Zn(II) adsorption on the cobalt nuclei [10]. Amodified hydroxide oscillation model has also beenproposed, in which repeating layers of (Zn, ZnO andCo) would be deposited after an initial cobalt deposi-tion [15].

* Corresponding author. Fax: +34-93-4021231.E-mail address: [email protected] (E. Valles).

0022-0728/01/$ - see front matter 2001 Elsevier Science B.V. All rights reserved.PII: S00 2 2 -0728 (01 )00450 -8

E. Gomez et al. / Journal of Electroanalytical Chemistry 505 (2001) 5461 55

The aim of the present study was the analysis andcharacterisation of different Zn+Co alloy phases andto test whether the proposed mechanism for the begin-ning of the anomalous deposition on vitreous carbonalso holds for metallic substrates in baths of highermetallic concentration. Vitreous carbon, copper andnickel substrates and different [Zn(II)]/[Co(II)] ratioswere used. No additives were used since they caninfluence the composition and morphology of thedeposits.

2. Experimental

A conventional three electrode cell and a poten-tiostat/galvanostat EG&G 273 were used. The mor-phology of the deposits was examined with a Hitachi

2300 scanning electron microscope. The deposit compo-sition was analysed with an electron microprobe,Cameca SX-50. In some cases an X-ray photoelectronspectrometer (XPS, PHI 5600 multitechnique systemusing standard AlK radiation, resolution 0.1 eV) wasused.

X-ray diffraction (XRD) phase analysis was per-formed on a Philips MRD diffractometer using its lowresolution parallel beam optics. The CuK radiation(=1.5418 A ) was selected by means of a diffractedbeam flat graphite crystal. 2/ diffractograms wereobtained in the 20100 range with a step of 0.05 anda measuring time of 5 s per step.

The solutions were freshly prepared with analyticalgrade ZnCl2 and CoCl26H2O. In all the experiments[Zn(II)]+ [Co(II)] was maintained at 0.5 mol dm3 andthe solution pH was adjusted to 4 in order to minimisehydrogen evolution.

All chemicals were of Merck analytical grade and thewater was first doubly distilled and then treated with aMillipore Milli-Q system.

Vitreous carbon, copper and nickel were in the formof rods 2 mm in diameter. Vitreous carbon was fromMetrohm, and Cu and Ni, 99.99% pure, from JohnsonMatthey. Both vitreous carbon and copper were pol-ished with alumina, and nickel was polished with dia-mond paste of 6, 1 and 0.25 m. An Ag AgCl NaCl 1mol dm3 reference electrode was mounted in a Luggincapillary. All potentials were referred to this electrode.The counter electrode was a platinum helix.

Stripping analysis were performed immediately afterpotentiostatic or galvanostatic deposition in situ, with-out removing the electrode from the solution, andselecting in each case an initial potential at whichdeposition did not occur.

3. Electrochemical results

3.1. Voltammetric results

The electrodeposition of Zn+Co over different sub-strates was studied first by cyclic voltammetry. In thenegative scan, an increase of the zinc(II) concentrationadvanced the start of the main electrodeposition pro-cess, this advance being higher for a nickel substrate(Fig. 1A) than for vitreous carbon (Fig. 1B). Severaloxidation peaks appeared in the positive scan, theirrelative size depending on the solution composition, thetype of substrate and stirring conditions. For the threesubstrates higher zinc(II) concentrations increased themore negative oxidation peaks (Fig. 1A and B, curvesa), which according to the previous work [8] correspondto the zinc-rich deposits. At lower zinc(II) concentra-tions only the more positive peaks appeared in thepositive scan (Fig. 1A and B, curves b). In all cases the

Fig. 1. Cyclic voltammograms at 50 mV s1 in the following solu-tions: (a) 0.15 mol dm3 ZnCl2+0.35 mol dm

3 CoCl2; (b) 0.05mol dm3 ZnCl2+0.45 mol dm

3 CoCl2. =1000 rpm. (A) Nickelelectrode and (B) vitreous carbon electrode.

E. Gomez et al. / Journal of Electroanalytical Chemistry 505 (2001) 546156

Fig. 2. Cyclic voltammograms at 50 mV s1 in a 0.15 mol dm3

ZnCl2+0.35 mol dm3 CoCl2 solution. Nickel electrode. Rotation

speed: (a) =1000 and (b) =0 rpm.

current densities causing a clear decrease of peak ABand an increase of peaks C and D, although withcopper, as with vitreous carbon, a very high currentdensity was necessary to minimise peak AB. For thethree substrates, increasing current densities, even un-

Fig. 3. Stripping voltammograms at 50 mV s1 of deposits obtainedgalvanostatically at =1000 rpm in a 0.15 mol dm3 ZnCl2+0.35mol dm3 CoCl2 solution at different current densities. (A) Nickelelectrode. Current density: (a) 28.7; (b) 63.7; and (c) 86.0mA cm2. Q=5 mC. (B) Copper electrode. Current density: (a)28.7; (b) 63.7; and (c) 318.5 mA cm2. Q=5mC.

solution was moderately stirred during the electrodepo-sition to ensure alloy formation, since in quiescentsolutions the depletion of zinc(II) near the electrodecould lead to normal cobalt deposition [9].

The comparison of voltammograms of vitreous car-bon and copper showed that, as in the usual behaviour,stirring of the solution hindered the nucleation process.However, with nickel the opposite behaviour was ob-served, electrodeposition being clearly enhanced by stir-ring (Fig. 2).

3.2. Stripping results

Stripping analysis allows the in situ characterisationof the deposits. The electrodeposits were obtained po-tentiostatically or galvanostatically under stirring, so asto favour the alloy formation. The galvanostatic de-posits were mostly used because of the ease of reachinga given electrodeposition charge. Fig. 3 shows the influ-ence of both the electrode nature (nickel or copper) andthe galvanostatic current density. Galvanostatic tran-sients show the typical nucleation spike followed by apotential plateau (Fig. 3A and B). In previous work onvitreous carbon [8], the stripping peaks were assigned asfollows: peaks AB and C correspond to zinc oxidationfrom different Zn+Co alloys phases, peak D to cobaltmatrix oxidation of these phases, and peak E to theoxidation of pure cobalt. The stripping results withmetallic substrates were similar to those with vitreouscarbon, showing well-defined oxidation peaks AE thatpreceded in all cases the massive substrate oxidation(Fig. 3A and B). The relative predominance of thesepeaks depended both on the substrate and on thecurrent density. In general, low electrodeposition cur-rent densities favoured the appearance of the first peakAB (where peak B was a shoulder of peak A), higher


Fig. 4. Galvanostatic deposition transients for 30 s at 22.3mA cm2 and =1000 rpm and stripping voltammograms at 50mV s1 of the corresponding deposits, in a 0.05 mol dm3 ZnCl2+0.45 mol dm3 CoCl2 solution. Q=21 mC. (a) Nickel electrodeand (b) copper electrode.

der stirring, brought about the appearance of peak E,corresponding to pure cobalt.

Differences were observed between copper and nickelsubstrates. With the same electrodeposition currentdensity nickel favoured the formation of the alloy thatoxidises mainly under peaks C and D (curve a in Fig.4), whereas copper favoured the formation of alloysthat oxidise mainly in peak A (curve b).

4. Characterisation of deposits

In order to characterise the deposits formed underthe different condition, deposits at long depositiontimes were prepared, after having checked that thestripping curves, and, therefore, the composition of thedeposits, did not change at longer deposition times(Fig. 5). In order to identify each oxidation peak,deposits were prepared under chosen experimental con-ditions (bath composition, current density and sub-strate) that produced different, well-defined strippingcurves.

Electrodeposits obtained with solution I (0.15 MZnCl2+0.35 M CoCl2), a copper electrode, and lowelectrodeposition current densities oxidised mainly inpeak A and in a small peak D, and were made up ofhexagonal platelets (Fig. 6A). XRD showed that theyhad a very modified hexagonal zinc -phase, althoughthey contained only around 1% cobalt (Fig. 6B).

The cell parameter modification affected mainly the ccrystallographic axis, which was clearly lower than thatof pure zinc. The cell parameters of this deposit werea=2.681(2) and c=4.839(4) A , whereas those of purezinc are a=2.665 and c=4.947 A .

Deposits were obtained from solution I, but at highercurrent densities produced stripping curves showingpeaks A, C and D, the charge under peak C beinghigher with nickel than with copper. These depositswere homogeneous and polyhedral grained (Fig. 7A),with no hexagonal morphology, and with a cobaltcontent between 4 and 10%, this being always higherwith nickel. XRD showed, together with the lines of thesubstrate, the lines of an undistorted hexagonal zinc-phase, and additional lines that can be indexed con-sidering a Zn+Co -phase of bcc structure with theparameter a=9.03 A (Fig. 7B). The position of thesethree lines did not depend on the composition of thedeposit. XRDs of these samples were recorded both forthe freshly prepared deposit and for the same depositafter different times from 7 to 14 days, in order todetect possible zinc segregation. Identical diffrac-tograms were obtained in all cases.

X-ray photoelectron spectra (XPS) showed a narrow,well-defined Co2p peak with a binding energy of 778 eV(Fig. 7C), in good agreement with the presence in thedeposit of metallic cobalt only, since it is well separated

Fig. 5. Galvanostatic deposition transient on nickel at 22.3mA cm2 and =1000 rpm, and stripping voltammograms at 50mV s1 of deposits obtained after: (a) 2 s; (b) 3.33 s; and (c) 5 s, ina 0.15 mol dm3 ZnCl2+0.35 mol dm

3 CoCl2 solution.


from the cobalt oxides, located at around 780 eV. AZn2p peak appears at around 1022 eV, but unfortu-nately the peaks of metallic zinc (1022 eV) and of zincoxides (10221022 5 eV) overlap, so that XPS cannotthrow light on the oxidation state of Zn. However,since XPS showed that oxygen was detected at thebeginning of sputtering only, the presence of metallicoxides in the bulk of the deposits can be disregarded.

At lower zinc concentrations in the bath (solutions II(0.10 M ZnCl2+0.40 M CoCl2), and III (0.05 MZnCl2+0.45 M CoCl2)), deposits which oxidisedmainly in peaks C and D were obtained on both copperand nickel electrodes. Deposits obtained with low elec-trodeposition current densities were polyhedral grainedand with a Zn -phase and Zn+Co -phase bcc, asthose deposited from solution I at higher current densi-ties. However, with current densities more negativethan 15 mA cm2, peak E appeared in the strippingcurve together with peaks C and D. Deposits obtainedunder these conditions were inhomogeneous, showingtwo distinct zones, a predominant zinc-rich polyhedral-

Fig. 7. (A) SEM micrograph of a deposit obtained galvanostaticallyon nickel at 62.7 mA cm2 for 650 s in a 0.15 mol dm3 ZnCl2+0.35 mol dm3 CoCl2 solution. =1000 rpm. Cobalt percentage:7%. (B) X-ray diffractogram corresponding to the deposit of Fig. 7A.

Fig. 6. (A) SEM micrograph of a deposit obtained galvanostaticallyon copper at 22.3 mA cm2 for 1800 s in a 0.15 mol dm3

ZnCl2+0.35 mol dm3 CoCl2 solution. =1000 rpm. Cobalt per-

centage: 1.3%. (B) X-ray diffractogram corresponding to the depositof Fig. 6A.

grained zone, and a second zone with a cobalt contentgreater than 70% (Fig. 8).

5. Initial stages of alloy deposition

Since alloys deposited on nickel showed some differ-ences with respect to those deposited on vitreous car-bon or copper, possible differences in the initialdeposition stages were investigated. With vitreous car-bon, more positive potentials and long deposition timeswere necessary in order to detect the formation of theinitial deposit. Upon stepping the potential to 1030mV the current density increased slowly, nearly reach-ing a plateau of about 40 A cm2 (Fig. 9). Thestripping curve of the deposit obtained during 170 sunder these conditions (curve a) showed only one peakat around 200 mV, probably corresponding to purecobalt. When the deposition time was increased to 375s (curve b) a large peak of cobalt oxidation, now at100 mV, appeared together with a small peak centredat 500 mV, related to the start of the alloydeposition.


Fig. 7C. Co2p XPS spectrum of the deposit of Fig. 7A at different sputtering times.

When nickel was used as substrate, less negativepotentials than on vitreous carbon were necessary toallow the deposition process, i.e. with an electrodeposi-tion potential of 735 mV the current densityrecorded in the j t transient, although low (Fig. 10,curve a), and although the deposition potential usedwas 300 mV more positive, was always higher than thatdetected on vitreous carbon at the start of the process.These deposits oxidised at about 350 mV, as corre-sponds to a fresh cobalt deposit (Fig. 10, curve b), morenegative potentials being required to attain alloydeposition.

6. Discussion

It has been shown that the stripping technique is anuseful tool to characterise in situ the Zn+Co electrode-posits formed in chloride medium on metallic susbtrates(copper and nickel), as had been shown to be the casefor vitreous carbon. The number of stripping peaks andtheir positions were unaffected by the nature of thesubstrate. Moreover, the stripping peaks of depositsobtained with a total metallic concentration of 0.5 Mwere similar to those of deposits previously obtainedfrom more dilute concentrations [8], whose strippingpeaks had been tentatively assigned by combining theelectrochemical and compositional results with the dataof the thermal phase diagram. The study was restrictedto conditions under which anomalous codepositiontakes place. Although the general trends of depositionare similar, the substrate influences the alloy formationand the corresponding stripping curve. In general, forthe same electrodeposition conditions, vitreous carbonand copper favour the formation of deposits that oxi-

dise at potentials more negative than those obtained onnickel substrates.

The second goal of this work was to determinewhether a given stripping peak corresponded to a givenphase, independently of the substrate, used. For thethree substrates, the deposits that oxidised under peakAB (zinc oxidation) and under a small peak D (cobaltmatrix oxidation) had less than 3% cobalt, had a hexag-onal platelet structure, and XRD analysis allowed aclear assignment to a hcp zinc -phase with cellparameters clearly different from those of pure zinc andcontinuously varying c/a (ratio of c-axis and a-axis)with cobalt content. Under these conditions of lowcobalt content metallic zinc can incorporate the cobalt

Fig. 8. SEM micrograph of a deposit obtained galvanostatically oncopper at 22.3 mA cm2 for 1800 s in a 0.05 mol dm3 ZnCl2+0.45 mol dm3 CoCl2 solution. =1000 rpm. Cobalt percentage:70%.


Fig. 9. Potentiostatic transient and stripping voltammograms at 50mV s1 of deposits on vitreous carbon obtained potentiostatically at1030 mV in a 0.05 mol dm3 ZnCl2+0.45 mol dm

3 CoCl2solution. =1000 rpm. Deposition time: (a) 170 and (b) 375 s.

ing the same variation of parameter a as reported forthis phase in the phase diagram. It seems that, inelectrodeposition, the crystalline lattice of zinc cannotincorporate all the cobalt, and consequently a heteroge-neous deposit of zinc and a Zn+Co alloy forms.Although the thermal diagram of Zn+Co indicatesthat the solubility of cobalt in zinc is around 78% [16],under electrodeposition conditions the zinc can incor-porate only up to 3% cobalt, a different phase formingat higher cobalt contents The (Zn+Co -phase) phaseis obtained directly during the electrodeposition, sincethe stripping peak C, corresponding to the oxidation ofzinc of this -phase, appears even for low depositiontimes. Therefore, peak A-B corresponds to the zincoxidation of the -phase and the peak C corresponds tothe oxidation of zinc from the Zn+Co -phase. Thepossibility of zinc segregation was discarded, since theXRD results of fresh and aged deposits were identical.

Previously, Yan et al [15] found that the electrode-posits of similar cobalt contents (6.6%) obtained froman acidic sulphate bath are also heterogeneous, andcontained Zn, ZnO and -Co. Under our conditions theexistence of a non-distorted Zn phase is clearly de-tected, but the lines corresponding to -Co do notappear. Moreover, the presence of both zinc and cobaltoxides is discounted from XPS results.

Fig. 10. Potentiostatic transient and stripping voltammograms at 50mV s1 of deposits on nickel obtained potentiostaticaly at 735 mVfrom a 0.05 mol dm3 ZnCl2+0.45 mol dm

3 CoCl2 solution.=1000 rpm. Deposition time: (a) 70 and (b) 150 s.

atoms in its crystalline lattice, although the inclusion ofcobalt causes a significant distortion of the hexagonalstructure, as can be inferred from the variation of thecell parameters with respect to those of pure zinc.Although the formation of this Zn-rich phase is fa-voured by higher zinc(II) concentrations in the bathand by low electrodeposition current densities, with anickel substrate very low current densities are required.

Deposits that oxidise mainly under peaks A and C(corresponding to oxidation of zinc) and peak D (oxi-dation of cobalt matrix) are favoured on a nickelsubstrate and with cobalt contents ranging between 4and 10%, are very different from those discussed above.Although they appear homogeneous under SEM, XRDshows that they are constituted by two phases, zinc anda bcc Zn+Co -phase. The assignation of the addi-tional lines in the diffractograms to a -phase of bccstructure has been possible thanks to the phase diagraminformation, where a bcc structure of the -brass typewith a parameter a between 8.91 and 8.99 A is de-scribed [16]. Moreover, the patterns of the -brassphase of the JCPDS (PDFc25-1228, 71-397) [17]match well with the observed positions and intensitiesof the additional peaks if the corresponding a parame-ter of 9.03 A is used. This value of the parameter aleads to a composition of around 89.7% in zinc assum-


Therefore, deposits of 410% cobalt obtained fromthese electrodeposition conditions are formed by the-phase of zinc and -phase of Zn+Co alloy. Similarresults were obtained by Hayashi et al. [18] that de-tected, from a sulphate bath, the presence of the -phase in deposits when the cobalt percentage is greaterthan around 7%. Koura et al. [19,20] found that frommolten-salt electrolytes the Zn+Co deposits consist inZn and an intermetallic compound (Co5Zn2) at lowcobalt percentage in the deposits.

On the other hand, in previous work [10] from resultsobtained at low total metallic concentration, it wasproposed that the very initial stage of the Zn+Coanomalous codeposition on vitreous carbon consistedof an initial cobalt deposition that could be blockedlater by the adsorption of zinc(II) species. The resultspresented here confirmed this proposal on vitreouscarbon and show that cobalt deposition also occursinitially on nickel electrodes, less negative potentialsbeing necessary, as is normal, to attain the depositionprocess. Moreover, a study of the stripping curves ofthe deposits obtained on nickel and vitreous carbonshows that initial cobalt deposition is favoured onnickel, so much so that it can be easily detected bystripping from the first deposition times. A catalyticeffect for cobalt deposition on the nickel electrodecompared with other substrates was also reported pre-viously [21].

Alloy formation over the initial cobalt deposit takesplace on both nickel and vitreous carbon, although thenature of the substrate influences alloy formation, vit-reous carbon and copper favouring the formation ofdeposits richer in zinc than those obtained with nickel.

7. Conclusions

In the oxidation of Zn+Co deposits obtained underconditions of anomalous codeposition, four strippingpeaks (AD) were detected. A relation between thesestripping peaks and the phases present in the depositwas found. Deposits with %Co3% corresponding tothe hcp -phase with a c/a ratio variable as a functionof cobalt percentage, oxidise under peak AB (zincoxidation) and a small peak D (porous cobalt matrixoxidation). Deposits formed by pure zinc and the bccZn+Co -phase oxidise in peaks A (zinc oxidationfrom -phase), C (zinc oxidation from -phase) and D(porous cobalt matrix oxidation). Therefore, the ap-pearance of peak C shows the presence of the -phasein the deposit.

At low deposition potentials or current densities, theformation of deposits of the -phase were favoured. Aninfluence of the substrate was observed. Nickel favours

the formation of the -phase and both copper andvitreous carbon maintain the deposition of the -phaseunder a wide range of conditions.

Results confirm that, independently of the substrate,the deposition process begins by cobalt deposition.Over some initial cobalt deposited, more favoured onthe nickel electrode, deposition becomes anomalousand formation of zinc-rich alloys takes place. The latercobalt deposition could be hindered by the adsorptionof zinc(II) species over the initial cobalt.

Acknowledgements

The authors thank the Serveis Cientfico-Te`cnics(Universitat de Barcelona) for equipment provision.This research was supported financially by contractMAT 2000-0986 of the Comision Interministerial deCiencia y Tecnologa (CICYT) and by the Comissionatof the Generalitat de Catalunya under Research ProjectSGR98-027.

References

[1] T. Adaniya, M. Omura, K. Matsudo, H. Naemura, Plat. Surf.Finish. 69 (1981) 96.

[2] V.M. Verberne, Trans. Inst. Met. Finish. 64 (1986) 30.[3] R. Fratesi, G. Roventi, Mater. Chem. Phys. 23 (1989) 529.[4] H.M. Wang, T.J. OKeefe, J. Appl. Electrochem. 24 (1994) 900.[5] R. Fratesi, G. Roventi, C. Branco, S. Simoncini, Surf. Coat.

Technol. 63 (1994) 97.[6] R. Fratesi, G. Roventi, G. Guiliani, J. Appl. Electrochem. 27

(1997) 1088.[7] I. Kirilova, I. Ivanov, St. Rashkov, J. Appl. Electrochem. 27

(1997) 1380.[8] M.L. Alcala, E. Gomez, E. Valles, J. Electroanal. Chem. 370

(1994) 73.[9] E. Gomez, E. Valles, J. Electroanal. Chem. 397 (1995) 177.

[10] E. Gomez, E. Valles, J. Electroanal. Chem. 421 (1997) 157.[11] C. Karwas, T. Hepel, J. Electrochem. Soc. 136 (1989) 1672.[12] A. Brenner, Electrodeposition of Alloys, Academic Press, New

York, 1963.[13] K. Higashi, H. Fukushima, T. Urakawa, T. Adaiya, K. Mar-

sudo, J. Electrochem. Soc. 128 (1981) 2081.[14] H. Dahms, I.M. Coll, J. Electrochem. Soc. 112 (1965) 771.[15] H. Yan, J. Downes, P.J. Boden, S.J. Harris, Philos. Mag. A 70

(1994) 373.[16] M. Hansen, Constitution of Binary Alloys, McGraw Hill, New

York, 1958.[17] Powder Diffraction File, version 2, Joint Committee of Powder

Diffraction Standards, Pennsylvania, 1998.[18] K. Hayashi, Z. Tanaka, K. Kondo, J. Iron Steel Inst. Jpn 85

(1999) 314.[19] N. Koura, T. Endo, Y. Idemoto, J. Non-Cryst. Solids 207 (1996)

650.[20] N. Koura, S. Matsumoto, Y. Idemoto, Hyomen Gijutsu 49

(1998) 913 (see also p. 1215).[21] E. Gomez, J. Ramirez, E. Valles, J. Appl. Electrochem. 28 (1998)

71.

.

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