In this work, we tried to combine the advantages of microemulsion and emulsion synthesis to obtain stable concentrated organosols of Ag nanoparticles, promising liquid-phase materials. Starting reagents were successively introduced into a micellar solution of sodium bis-(2-ethylhexyl)­sulfosuccinate (AOT) in n-decane in the dynamic reverse emulsion mode. During the contact of the phases, Ag+ passes into micelles and Na+ passes into emulsion microdroplets through the cation exchange AOTNaOrg + AgNO3 Aq = AOTAgOrg + NaNO3 Aq. High concentrations of NaNO3 and hydrazine in the microdroplets favor an osmotic outflow of water from the micelles, which reduces their polar cavities to ∼2 nm. As a result, silver ions are contained in the micelles, and the reducing agent is present mostly in emulsion microdroplets. The reagents interact in the polar cavities of micelles to form ∼7 nm Ag nanoparticles. The produced nanoparticles are positively charged, which permitted their electrophoretic concentration to obtain liquid concentrates (up to 30% Ag) and a solid Ag–AOT composite (up to 75% Ag). Their treatment at 250 °C leads to the formation of conductive films (180 mOhm per square). The developed technique makes it possible to increase the productivity of the process by ∼30 times and opens up new avenues of practical application for the well-studied microemulsion synthesis.

An ETAAS method was developed to determine the platinum group elements and gold in copper-nickel ores using a single sample. It is based on an approach involving interconnected consideration of the main components of analytical procedure (autoclave decomposition of sample; collective extractive preconcentration of metals with a mixture of alkylaniline hydrochloride and petroleum sulfides; and atomic absorption spectrometric analysis of the extract). The concentrations of elements determined in standard reference materials (lode and impregnation copper-nickel sulfide ores) were found to be in accordance with the certified values, within experimental error. The relative standard deviation varied between 2 and 17% at 0.05-10 mg kg-1 element concentrations. The determination limits were 0.001-0.06 mg kg-l for a 5 g sample and an extract volume of 5 ml.

The size, composition, and morphology of KNO3 particles produced under the conditions of isothermal evaporation crystallization were found to depend on the concentration ratios of surfactant in mixed reverse micelles of Tergitol NP-4 + AOT, content of water pseudophase (w o = 1.1–4.4), concentration of salt (0.8–2.5 M), and temperature (20–40 °C). In optimal conditions (w o = 2.2, T = 35 °C), powders with micrometer particles of tubular structure are formed in reverse micellar solutions of Tergitol NP-4 in n-decane. The addition of 0.01–0.05 M AOT results in the splitting of tubes, a 103-fold increase in the specific surface area, and formation of whisker-type particles 5–10 μm long and 0.2–0.5 μm thick. We used photon-correlation spectroscopy and a spinning drop procedure, which showed that the addition of AOT to Tergitol NP-4 leads to a decrease in the hydrodynamic diameter of reverse micelles, and interfacial tension passes through the maximum, which increases with growing temperature.

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We have determined the solubilization and crystallization fields of KNO3 for simple (Tergitol NP-4 and AOT) and mixed (Tergitol NP-4 + AOT) microemulsions at 35 °C, depending on water content and concentration of KNO3. An increase in the content of AOT in mixed microemulsions leads to widening of the solubilization field, but the crystallization field narrows up to complete disappearance (in simple microemulsions of AOT). Fourier transform-infrared spectroscopy, photon–correlation spectroscopy, and flame photometry were used to determine the rate of water evaporation (2.6–7.4 μL/min), hydrodynamic diameter of micelles (4.3–10 nm), and the content of water and K+ and Na+ ions in the studied microemulsions at different stages of evaporation crystallization of KNO3. In simple microemulsions of Tergitol NP-4 crystallization begins well before that in mixed microemulsions; in mixed microemulsions the beginning of crystallization requires higher supersaturation (up to 13 M) compared to simple microemulsions (∼4 M at initial solubilization capacity of 0.5 vol %). In accordance with the Gibbs–Thomson (Kelvin) theory, high supersaturations suggest that in mixed micelles cores of smaller sizes are formed. During crystallization, micelles with KNO3 solution coexist with KNO3 crystals. The function of micelles is to supply “building material” for their growth. Numerical simulation with the help of direct optimization showed that in mixed micelles at low water contents, Na+ ions are stronger bound with AOT–, owing to which Na+ ions occur only as impurities in powders.

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