S. A. Lilin

Anodic behavior of hafnium in water-alcohol solutions of sodium chloride

High-rate anodic dissolution of hafnium in water-isopropanol-glycerin chloride solutions is studied in relation to the alcohol concentration and electrolyte temperature by voltammetric, chronoamperometric, and photoelectric measurements. The dissolution mechanism varies with increasing potential: upon reaching a potential of 0.4 to 0.5 V, the diffusion control of the process is replaced by kinetic one. It is supposed that the anodic behavior of hafnium is determined by the properties of surface nonstoichiometric semiconducting films, which are present on the metal under all studied conditions.

Physicochemical properties of ultrafine copper-containing powders synthesized by cathode reduction

Copper-containing ultrafine (nanosized) powders were synthesized from solutions of copper dichloride in the water-isopropanol binary solvent by electrochemical reduction. Particles were analyzed using a transmission electron microscope. A combination of thermal analysis with mass spectrometry made it possible to determine the composition of the cathode deposit obtained.

Electrochemical production of ultradisperse copper-containing particles from organo-aqueous electrolyte solutions

A possibility of the cathodic deposition of copper-containing nanopowders from organo-aqueous electrolyte solutions is studied. The dimension of particles is corroborated with a transmission electron microscope. Additions of low-molecular surfactants to aqueous electrolyte solutions lead to a decrease in the limiting cathodic currents thus promoting the formation of finely dispersed powder.

Chemical synthesis of stable nano-sized water-organic copper dispersions

The formation of aggregatively stable copper dispersions by the reduction of copper salts with thiourea dioxide or sodium hydroxymethane sulfinate in a water-organic solvent is studied. X-ray electron spectroscopy and photon correlation spectroscopy showed that the chemically formed copper exists as nano-sized particles.

Extracting Heavy Metals with Cellulose-Containing Materials

Sorptivity of cellulose-containing materials of heavy metal ions from diluted electrolyte solutions is studied. Capacity and kinetic characteristics of the sorbents are estimated. The limiting stage of the adsorption of copper and nickel ions is shown to have a mixed nature. These sorbents are found to provide a high degree of metal ion removal.

Diffusion mass transfer under the conditions of instability of products of electrochemical reaction

Theoretically considering the diffusion-migration mass transfer in binary z1–z2-electrolytes during anodic dissolution of metals is performed with due allowance for the decomposition of intermediates formed. The components’ concentration and electric potential distributions in the diffusion layer, as well as the system’s current-voltage characteristics are calculated. It is shown that under conditions of the cation slow removal the electrochemical process is slowed down with an increase in the products’ stability constant.

On the Diffusion Kinetics of Anodic Dissolution of Metals Complicated by Decomposition of the Reaction Products

A diffusion–migration problem of anodic dissolution of a two-valent metal associated with decomposition of the reaction products is considered in terms of Ya.M.Kolotyrkins concept of direct participation of anions in electrochemical reactions. Distributions of the components and electric potential in the diffusion layer, as well as voltammetric characteristics of the process are calculated. It is shown that an increase in stability constants of the products can make the dissolution rate either increase or decrease depending on the diffusivity ratio of the solution components.

A Quantitative Description of the Anodic Dissolution of Nickel in Water–Organic Media1

The effect of aprotic solvent additives on the anodic behavior of nickel in aqueous sodium chloride solutions is studied. A three-parameter equation correlating the physicochemical properties of the medium (conductivity, polarity, and polarizability) with the electrochemical dissolution rate of the metal is formulated. A substantial role of conductivity agrees with the diffusion control of the processes under investigation.

Kinetic Regularities of Nickel Anodic Dissolution in Water–Alcohol Sodium Chloride Solutions

Nickel anodic dissolution in water–alcohol sodium chloride solutions is studied on a rotating disk electrode. It is found that the character of the limiting stage of nickel dissolution is determined by the essence of the alcohol. Under potentiostatic conditions, a spontaneous increase in the current (autocatalytic effect) is found, which depends on the solution composition.

Anodic behavior of a BK8 type tungsten-cobalt alloy in organo-aqueous solutions of sodium nitrate

Anodic dissolution of a BK8 type hard alloy in aqueous and water-monoethanolamine solutions of sodium nitrate is studied. It is found that, at a concentration of monoethanolamine (MEA) higher than 6 mol/l, the removal of the dissolution products to the bulk of electrolyte is the slow stage of the process. The best surface finish (Rz=0.44 μm) is achieved in the solutions containing 8 mol/l MEA.