A. I. Titkov

Characterization and Growth Mechanism of Nickel Nanowires Resulting from Reduction of Nickel Formate in Polyol Medium

Nickel linear nanostructures were synthesized by reduction of nickel formate with hydrazine hydrate in ethylene glycol medium in the absence of any surfactants or capping agents for direction of the particles growth. The effect of the synthesis conditions such as temperature, reduction time, type of polyol, and nickel formate concentration on the reduction products was studied. The size and morphology of the nickel nanowires were characterized by X-ray diffraction, scanning, and transmission electron microscopy. It was shown that the nickel nanocrystallites were wire-shaped with a face-center-cubic phase. Ethylene glycol was found to play a crucial role in the formation of the nickel nanowires. The possible growth processes of the wire-shaped particles taking place at 110 and 130°C are discussed. It was shown that, under certain synthesis conditions, nickel nanowires grow on the surface of the crystals of the solid intermediate of nickel with hydrazine hydrate.

Specific features of polyol synthesis of silver nanoparticles with the use of solid carboxylates as precursors

Electron microscopy, X-ray diffraction, and chromatography-mass spectrometry have been employed to investigate the reduction of solid silver caprylate in ethylene glycol with the formation of silver nanoparticles. The structural characteristics of silver nanoparticles have been studied as depending on the conditions of their synthesis, including temperature, reduction time, and silver salt concentration. It has been found that, in the studied range of parameters under the conditions, when solid silver caprylate is dispersed in ethylene glycol, the characteristics of resulting nanoparticles are almost independent of the synthesis temperature. This peculiarity is related to the fact that the formation and growth of nanoparticles occur on the surface of silver salt crystals and are accompanied by gradual dissolution thereof. In this system, ethylene glycol plays the roles of a reductant and a solvent for liquid reaction products.

Application of solvent extraction in the preparation of metal nano- and microparticles

The extraction of silver, nickel, copper, and bismuth from a solution of their salts by solutions of caprylic, 2-ethylhexanoic, and Versatic 10 and 913 acids in different diluents has been studied and the possibility of obtaining concentrated solutions of carboxylates of these metals has been shown. It has been established that the nature of carboxylic acid significantly affects the extraction of silver. The process of the thermal decomposition of metal-containing organic phases prepared as a result of the extraction of silver, nickel, copper, bismuth, lead, and cadmium by a solution of carboxylic acid in benzyl alcohol has been studied. The possibility of preparing metal powders of the micron and submicron size as a result of the thermal decomposition of solutions of metal-containing carboxylates in benzyl alcohol has been shown.

Synthesis of nonspherical nanoparticles by reducing silver neodecanoate extract with benzyl alcohol

A method for synthesizing nonspherical silver nanoparticles by reducing liquid extract of silver neodecanoate in benzyl alcohol has been developed. The method is simple and does not require the use of polyvinylpyrrolidone, sodium citrate or special methods using pre-synthesized seeds. The obtained particles have been investigated by the methods of electron microscopy, X-ray diffraction, and differential-thermogravimetric analysis. It has been found that triangular and hexagonal plates, as well as particles of pentagonal form and polyhedrons, are formed as a result of the reduction. The sizes of the obtained plates, depending on the synthesis conditions, vary from 80 nm to 2 μm. The method is promising for the industrial production of silver nano- and microplates.

Preparation of electroconductive aluminum-silicon oxide ceramic sensors modified with silver and bismuth nanoparticles

Abstract Currently, to provide complete information on measuring is one of the most essential problems for measuring devices. In order to obtain electrodes for recording of cardiac micropotentials in a wide range of frequencies, a process for modifying of the aluminum-silicon oxide ceramic matrix with bismuth or silver nanoparticles was investigated. It was found that when impregnating aluminum-silicon oxide ceramics with aqueous or organic solutions of the silver compounds with subsequent drying and calcinations, both the total amount of silver and its distribution over the thickness of the sample essentially depend on the nature of the silver precursor solution. Thus, when impregnating the aluminum-silicon oxide ceramics with an aqueous solution of silver nitrate followed by its reduction with formic acid, the silver content in the ceramic matrix does not exceed 15% and it is mainly distributed in the near-surface layer. The highest degree of impregnation (39%) and uniform distribution of silver throughout the volume of the sample are achieved by treatment of the ceramic matrix with a branched silver carboxylate (silver caprate) solution containing 250 g/L Ag, followed by drying and calcination of the samples at 250°C. It was shown that bismuth-containing electroconductive ceramics can be obtained by its impregnation with a solution of bismuth formate or caprylate followed by its calcination in vacuum at 280°C. The results of the study showed that the ceramic sensors modified with silver nanoparticles have a direct current drift of less than 5 nV/s while the noise level does not exceed±200 nV, which allows development of the measuring apparatus from 300 nV.

Metal Extracts as Precursors for the Production of Metal Powders and Coatings via the Extraction-Pyrolytic Method

The extraction of copper, silver, bismuth, and nickel with carboxylic acids thus providing concentrated metal-containing organic solutions and their crystalline salts has been studied. Micron- and submicron-sized metal powders have been obtained via reduction of these metals carboxylates by heating in benzyl alcohol or ethylene glycol. The synthesis of aspherical silver nanoparticles has been achieved by the reduction of a liquid extract of silver neodecanoate in benzyl alcohol. The possibility of the use of concentrated silver-containing solutions as inks for obtaining of electroconductive images has been demonstrated.

Synthesis of nickel nanowires by reduction of nickel formate in polyol medium

Linear nanostructures with different length to diameter ratios were synthesized by reduction of nickel formate with hydrazine hydrate in ethylene glycol medium. The effect of the synthesis conditions such as temperature, reduction time, and nickel formate concentration on the reduction products was studied. Morphology and properties of the nickel nanoparticles were studied by X-ray diffraction, scanning and transmission electron microscopy. It was shown that at 130 °C, well-crystallized metallic nickel in the form of nanowires of about 100 nm in diameter and of 2–4 microns in length is formed in the system. An increase in the reaction temperature up to 150 °C results in an increase in the reduction rate, a decrease in the particles size to 50 nm and changes the morphology of the particles. It was shown that an increase in the concentration of nickel formate in the initial solution does not affect the particles size but leads to an increase in their aggregation. An increase in the synthesis time leads to a substantial increase in the length of the nanowires, while their diameter increases slightly.