Vanadium oxide-based nanomaterials have been prepared by cryochemical synthesis (CCS) and supercritical drying (SCD) in n-hexane and acetone. We have performed the first comparative analysis which demonstrates differences in the physicochemical and electrochemical properties of the products, related to the key features of the effect of the CCS and SCD approaches. The nanomaterials prepared from the same precursor using CCS and SCD (in acetone and n-hexane) have been shown to differ in phase composition and morphology. The oxidizing annealing of the resultant aerogels and cryogel at 500°C in air leads to the formation of only one phase: α-V2O5. In all cases except the aerogel prepared using SCD in n-hexane, the crystalline α-V2O5 has a higher discharge capacity in comparison with the unannealed aerogels and cryogel. The highest discharge capacity among the annealed aerogels is offered by the sample prepared using SCD in acetone (255 mAh/g), and the highest discharge capacity among the unannealed materials is offered by the sample prepared using SCD in n-hexane (280 mAh/g). The samples range in energy density from 110 to 640 Wh/kg. The highest energy density is also offered by the aerogel prepared using SCD in n-hexane.

This paper examines the effect of supercritical drying parameters (including the nature of the solvent) on the electrochemical properties of vanadium oxide-based aerogels. It is shown that, among vanadium oxide-based aerogels prepared using different solvents (supercritical CO 2 , n -hexane, and n -octane), the material obtained in n -hexane is superior in discharge capacity characteristics: its capacity is 350 to 250 mAh/g in the first seven cycles. The aerogel obtained in supercritical CO 2 has a far lower capacity: 80–105 mAh/g.

V x Ti1–x O2 (x = 5 and 10 mol %) solid solutions have been synthesized through supercritical drying in isopropanol at t = 250°C and p = 10 MPa. Their physicochemical properties and photocatalytic performance have been compared to those of an earlier synthesized Zn x Ti1–x O2 aerogel containing 10 mol % Zn [1]. It has been shown that increasing the vanadium content of V x Ti1–x O2 from 5 to 10 mol % leads to a decrease in hydrogen evolution rate in methanol/water splitting reaction under UV irradiation from 190 to 32 µL/(min gcatal), whereas in the case of the anatase-based aerogel solid solution containing 10 mol % Zn an opposite picture is observed: the hydrogen evolution rate in methanol/water splitting reaction under UV irradiation increases sharply to 700 µL/(min gcatal).

Aerogels based on vanadium oxide were obtained by supercritical drying in carbon dioxide (scCO(2)) and organic solvents (acetone, n-hexane, n-heptane, and n-octane). The performed study allowed us to reveal the effect of experimental parameters (precursor type, type of primary and secondary solvents) on the phase composition and morphology of obtained aerogels. The obtained samples were studied by X-ray diffractometry, scanning electron microscopy, and capillary nitrogen adsorption-desorption (BET) method.

Vanadium oxide aerogels containing vanadium in low oxidation states (V3+, V4+) were synthesized by a supercritical drying technique, using mixtures of acetone and ethanol as supercritical solvents. The V3+/V4+ ratio in aerogels was shown to be easily tuned by changing the composition of supercritical solvents. The microstructure of the aerogels was notably affected by the choice of precursors.

Методом сверхкритической сушки в диоксиде углерода (СК-CO2) и органических растворителях (ацетон, н-гексан, н-гептан, н-октан) получены аэрогели на основе оксидов ванадия. Проведенный комплекс исследований позволил установить влияние экспериментальных параметров (тип прекурсора, тип первичного и вторичного растворителей) на фазовый состав и морфологию получаемых аэрогелей. Синтезированные образцы исследованы методами РФА, РЭМ, методом капиллярной адсорбции-десорбции азота (БЭТ).

An influence of heating mode of a reaction system on phase composition and morphology of products during hydrothermal and microwave-hydrothermal synthesis of vanadium oxide nanomaterials is presented at the current work. The common hydrothermal treatment of V2O5 center dot nH(2)O xerogel is proved to give rise one-dimensional V3O7 and V6O13 phases. On the other hand, microwave-hydrothermal treatment of the same precursor leads to xerogel crystal structure distortion and to possible formation of superstructure.

Aerogel gives rise to nano-boomerangs with a high return

A completely functional composite cathode material based on a VOx aerogel was synthesized by a supercritical drying technique. The electrochemical performance of the resultant composite was characterized.

The stability of the Aurivillius phases in the system Bi2O3-Fe2O3-TiO2 was investigated. Structural and physicochemical parameters, allowing to calculate the limits of the length of the homologous series of the compounds Bin+1Fen-3Ti3O3n+3 were identified. It was found that the maximum thickness of a perovskite-like block of these compounds is similar to 3.7 nm.

A novel phase of vanadia-based whiskers Ba 0.25 V 2 O 5 ·1.5H 2 O with a huge aspect ratio (40000:1), which can be used as conductive reinforcing fibers in electrode composites or as an ‘electronic paper’, has been synthesized by a hydrothermal method and characterized by XRD, SEM, TEM, SAED, EDX, TG and XPS.

A phase of Mg-todorokite with a size of structural tunnels of ∼10 Å has been synthesized by the hydrothermal method in the form of lamellar crystalline aggregates 50–100 nm in size. Topotactic interaction with concentrated nitric acid results in the formation of the H-form of todorokite, having a high ability to adsorb Cs + , Pb 2+ , and Ba 2+ ions from water solutions. H-todorokite can be used as an ion filter for cleaning ions of heavy metals from water solutions.