ON THE KINETICS OF THE PROCESS OF GALVANIC SUBSTITUTION OF TITANIUM BY NICKEL
Rubrics: 2. CHEMICAL TECHNOLOGY
Authors:
1.
KNITU
2.
Kazan National Research Technological University
Kazan, Russian Federation
Kazan, Russian Federation
3.
KNITU
4.
Kazanskiy nacional'nyy issledovatel'skiy tehnologicheskiy universitet
Type:
Article
Pages:
from 129
to 132
Status:
In work
Language:
Russian
Keywords:
TITANIUM, NICKEL, HYDROGEN, GALVANIC SUBSTITUTION, KINETICS
Abstract (English):
The galvanic substitution method is one of the promising methods for the synthesis metal microparticles, which allows controlling their size and morphology. The driving force of the process is the difference in the standard redox potentials of the deposited and dissolving metals. A more negative potential of the dissolving metal causes its oxidation and transition into solution in the form of ions, while ions of the deposited metal with a more positive potential are reduced on the surface of the source metal. This process proceeds spontaneously and does not require an external current supply. However, it is important to take into account the possibility of coupled processes, such as hydrogen evolution, which can affect the kinetics of the reaction and the properties of the resulting materials. The kinetics of the process of galvanic replacement of titanium (-1.209 V) with nickel (-0.257 V) in an aqueous solution of nickel(II) chloride in the presence of hydrofluoric acid is studied. It was found that the process is accompanied by an increase in the temperature of the reaction mixture, which is due to the exothermic nature of the galvanic replacement reaction occurring between titanium and nickel(II) ions. The maximum nickel yield (0.3) is achieved in 150 s, while the maximum deposition rate is observed at 60 s from the beginning of the process. In parallel, the kinetics of conjugate hydrogen evolution has been studied. The maximum volume of hydrogen (1025 cm3) is formed in 120 s, and the maximum release rate is observed at 40 s. A comparison of the kinetic curves of nickel deposition and hydrogen evolution has shown the relationship of these processes. The decrease in the rate of hydrogen release after 40 s is explained by a change in the pH of the near-surface layer, the formation of a passivating layer and a decrease in the available surface of titanium. The slowdown in nickel deposition after 60 s is associated with a decrease in the active surface of titanium due to the formation of a nickel coating and competition with the hydrogen release process. The results obtained contribute to the understanding of the mechanism of galvanic replacement of titanium with nickel and can be used to optimize the process of obtaining Ti-Ni materials.
The galvanic substitution method is one of the promising methods for the synthesis metal microparticles, which allows controlling their size and morphology. The driving force of the process is the difference in the standard redox potentials of the deposited and dissolving metals. A more negative potential of the dissolving metal causes its oxidation and transition into solution in the form of ions, while ions of the deposited metal with a more positive potential are reduced on the surface of the source metal. This process proceeds spontaneously and does not require an external current supply. However, it is important to take into account the possibility of coupled processes, such as hydrogen evolution, which can affect the kinetics of the reaction and the properties of the resulting materials. The kinetics of the process of galvanic replacement of titanium (-1.209 V) with nickel (-0.257 V) in an aqueous solution of nickel(II) chloride in the presence of hydrofluoric acid is studied. It was found that the process is accompanied by an increase in the temperature of the reaction mixture, which is due to the exothermic nature of the galvanic replacement reaction occurring between titanium and nickel(II) ions. The maximum nickel yield (0.3) is achieved in 150 s, while the maximum deposition rate is observed at 60 s from the beginning of the process. In parallel, the kinetics of conjugate hydrogen evolution has been studied. The maximum volume of hydrogen (1025 cm3) is formed in 120 s, and the maximum release rate is observed at 40 s. A comparison of the kinetic curves of nickel deposition and hydrogen evolution has shown the relationship of these processes. The decrease in the rate of hydrogen release after 40 s is explained by a change in the pH of the near-surface layer, the formation of a passivating layer and a decrease in the available surface of titanium. The slowdown in nickel deposition after 60 s is associated with a decrease in the active surface of titanium due to the formation of a nickel coating and competition with the hydrogen release process. The results obtained contribute to the understanding of the mechanism of galvanic replacement of titanium with nickel and can be used to optimize the process of obtaining Ti-Ni materials.
Keywords:
TITANIUM, NICKEL, HYDROGEN, GALVANIC SUBSTITUTION, KINETICS
TITANIUM, NICKEL, HYDROGEN, GALVANIC SUBSTITUTION, KINETICS
