Investigation of Electro-Kinetic Behavior of Cysteine on Electrodeposition of Ni Through the AC and DC Techniques
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Niþ ad þ e ! Ni
INTRODUCTION
ORGANIC molecules containing nitrogen, oxygen, and sulfur have been widely used as additives in the electrodeposition of metals and their alloys.[1–5] Among the additives are the amino acids from a class of nontoxic organic compounds which are mostly soluble in aqueous media. Furthermore, they are commercially available with high purity and low cost. Amino acids containing carboxylic acid and amino functional groups can be adsorbed on the copper surface and act as a barrier layer against corrosion and against further metal deposition. Cysteine, a sulfur-containing amino acid (HSCH2CHNH2COOH), is an interesting additive which has been used in the electrodeposition process of metals.[6–10] Cyclic voltammetry (CV) was used by Reynaud et al.[11] and Ralph et al.[12] to study the electrochemical behavior of cysteine. Nickel electrodeposition or the electro-reduction of Ni involves two steps[13]: Ni2þ þ e ! Niþ ad
ðfastÞ
½1
MEHDI EBADI, Lecturer, is with the Department of Chemistry, Faculty of Sciences, Islamic Azad University-Gorgan Branch, Gorgan 49147-39975, Iran. Contact e-mail: [email protected] WAN J. BASIRUN, Professor, is with the Institute of Nanotechnology & Catalysis (NanoCat), IPS, University of Malaya, 50603 Kuala Lumpur, Malaysia, and also with the Department of Chemistry, Faculty of Science, University of Malaya. YOKE-L. SIM, Lecturer, is with the Department of Chemical Science, Faculty of Science, University Tunku Abdul Rahman, Jalan Universiti, Bandar Barat, 31900 Kampar, Perak, Malaysia. MOHAMMAD R. MAHMOUDIAN, Lecturer, is with the Department of Chemistry, University of Farhangian, 15916 Tehran, Iran. Manuscript submitted July 10, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS A
ðslowÞ
½2
The metastable Ni electro-reduction can be shown by Eq. [2]. However, the metastable reaction is yet to be clearly defined. The metastable reaction involves redox behavior, depends on surface coverage, and requires energy[14] where both steps can be affected by the types of additive agents. For better understanding of the reduction mechanism, linear sweep voltammetry (LSV),[15,16] AC impedance,[14,16] CV, and chronoamperometry[17–19] techniques have been used by numerous researchers. Burke et al.[20] have reported that the shapes (Nyquist plots) could change due to the different applied potentials, different types and concentrations of additives in the electrodeposition solution. Cyclic voltammetry and chronoamperometry were used by Torabi and Dolati[21] and Mentar et al.[22] to determine the mechanisms of transition metal electrodeposition. In addition, the LSV technique was used to investigate the electro-kinetic behavior of metal deposition.[15] Researchers have found that the additives, i.e., cysteine, can affect the smoothness and uniformity of the deposition surface.[23] In this work, the influence of cysteine as an additive on the morphology of Ni electrodeposition is studied. The electro-kinetics, nucleation, and growth of Ni electrodeposition with the presence of cyst
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