Zn2+及びNi2+イオンとSiO2コロイドの共析挙動
1987 年 38 巻 6 号 p. 217-222
詳細
1987 年 38 巻 6 号 p. 217-222
The codeposition behavior of Zn2+, Ni2+ and SiO2 was investigated by a galvanostatic method using colloidal SiO2 (20nm). The SiO2 content of the electodeposits increased with the increase of Ni2+ content in the bath, and the amount of Ni2+ adsorbed on SiO2 particles was greater than the amount of Zn2+ adsorbed on SiO2 in the bath. Ni2+ played an important role on the deposition of SiO2. The relation between the amount of SiO2 in the bath and in the electrodeposit changed in accordance with Guglielmi's theory. Adsorption of the SiO2 on the cathode seems to occur in the first stage of the Zn-Ni-SiO2 electrodeposition process. A part of the SiO2 in the electrodeposit coagulated into larger particles during electrolysis because the pH on the cathode became higher than that of the electrolyte. The surface pH on the cathode during Zn-Ni-SiO2 electrodeposition measured by micro-Sb electrode was about 5-7 at a bath pH of 2, and a current density of 10-20A/dm2. This value coincided with the pH of the coagulation of SiO2. These results indicate that the factors controlling the codeposition of SiO2, Ni2+, and Zn2+ were: 1) adsorption of Ni2+ on the SiO2 in the bath; 2) adsorption of SiO2 on the cathode according to Guglielmi's theory; and 3) coagulation of SiO2 by the increase of pH on the cathode during electrolysis.
