Oxidation of the silicon carbide surface in Watts' plating bath

Abstract

An important problem in metal-matrix composite production by electrochemical co-deposition of SiC particles with nickel is the large variation of the SiC concentration in the composite. One of the possible reasons is the change of SiC surface properties due to its oxidation during contact with the plating bath. X-ray photoelectron spectroscopy was applied to study the surface oxidation of the [0001] basal plane of a-SiC crystals contacted with Watts' plating bath at 55• C. It was shown that the growth of silica at the surface is preceded by the formation of a silicon oxycarbide species (SiO x C y ). The formation of graphite-type carbon at the surface was also observed. The equivalent layer thickness of the main species at the oxidized surface was calculated.

Hardening effect induced by incorporation of SiC particles in nickel electrodeposits

“…In Ni/micron SiC deposits the grain size was reduced to the 10.3-15.0 nm range and a significant increase in the hardness values was evident in comparison with pure Ni deposits [7]. Electrochemical impedance spectroscopy measurements [20] revealed that the embedding of partly hydrophobic SiC particles blocked a part of the metallic surface causing a current decrease, and thus new growth centers were produced, resulting in smaller Ni crystal size.…”

“…Several researchers [8,20] propose that codeposition of SiC particles perturbs the crystal growth of the Ni matrix by inducing an increase in the number of the nucleation sites and, consequently, a reduction in the crystallite size occurs. This effect cannot be explained only by the simple presence of SiC particles, if they are considered as physico-chemically inert particles.…”

“…It is noteworthy that, as mentioned above, although there is a plenty of research work concerning either the effect of operating conditions on the amount of codeposited SiC particles or and the resulting mechanical properties of composite coatings, the effect of the embedded particles on the microstructure of the coatings and, consequently, the relation between structure and properties has been investigated to a limited extent [9,12,20]. In the present study, the electrolytic codeposition of micronor nano-sized SiC particles with Ni from an additive free nickel Watts solution by applying either direct or pulse electroplating, was investigated.…”

“…Thus, it seems that the particle size plays an important role in the electrocodeposition process and hence in the mechanical properties of the Ni/SiC composite coatings. Moreover, recent research has pointed out that the physico-chemical properties of the SiC particles are crucial to the understanding of the codeposition mechanism [10][11][19][20][21].…”

“…Considerable research has been mainly focused on the impact of the electrodepostion parameters: electrolysis conditions (composition of the electrolytic bath, presence of additives, pH value), current conditions (type of imposed current and values of the current density) and properties of the reinforcing particles (size, surface properties, concentration and type of dispersion in the bath) on the electrolytic codeposition process of SiC with Ni, as well as the properties of the composite electrocoatings [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. In general, it has been observed that the amount of embedded SiC particles increases with both increasing concentration of suspended SiC particles and surfactant or organic additives in the electrolyte [14][15][16][17][18].…”