Currently, nanocomposites based on graphene and transition metal oxides are considered as promising materials for energy accumulation and storage due to their widespread occurrence in nature, low toxicity, and the ability of the metals to change the oxidation state. The rate of surface exchange electrons processes plays an important role in the formation of the electrophysical properties of materials. It is studied an effect of oxygen‐free graphene sheets on the activity of nanostructured ceria and zirconia in oxidation–reduction processes, where the rate of surface exchange electron interactions plays a key role. The reaction of CO oxidation is chosen as a model. It is shown that the introduction of oxygen‐free graphene sheets up to 3 nm thick into ceria or zirconia nanopowders leads to a decrease in the CO oxidation temperature. Apparently, this effect is caused by the formation of highly active centers with elongated terminal MO bonds in the presence of the sp 2 ‐electron system of graphene. It is found that graphene increases the ability of metals to reversible oxygen exchange. The introduction of oxygen‐free graphene into the Mn x O y /CeO 2 system leads to acceleration of surface exchange processes due to the facilitation of electron transfer in the system as a whole.

Currently, replacing expensive and short-lived materials for supercapacitors based on RuO2 with more cost-effective and high-performance materials that remain operational after a large number of cycles is a challenge. Cerium-based materials are the most attractive alternative because of cerium’s ability to quickly change oxidation state. This work proposes the synthesis of nanostructured graphene–ceria composite and studies its morphological features arising under the impact of oxygen-free graphene. The mechanism of formation of nano-ceria crystallites when the sol–gel transition occurs on the surface of graphene sheets is also considered. It has been proven that the introduction of 0.5–0.6 wt% graphene sheets into nano-ceria ensures the preservation of its single-phase state, while simultaneously increasing its dispersion. Using the dilatometry method, it has been determined that uniformly distributed sheets of oxygen-free graphene lead to a decrease in temperature of the beginning of composite sintering by 175°C compared with pure nano-ceria and increase the shrinkage value by two times, which, in turn, should promote better sintering. This study fills a gap in the synthesis and characterization of oxygen-free graphene composites, promising raw materials for small devices and large power plants.

Despite the high demand for nanostructured composites based on zirconia, existing studies primarily focus on their mechanical and electrical properties. However, due to the fragmentated research efforts, it is challenging to compare results across different studies and establish a comprehensive theory for the introduction of graphene sheets into nano-zirconia. This work aims to address these gaps by investigating the dependencies within the synthesis conditions - structure - physicochemical properties, which are critical for the future development of sintering modes for nanostructured composite powders based on zirconia and oxygen-free graphene. We have developed a method that combines sonochemical and sol-gel techniques to synthesize a series of graphenezirconia hybrid powders with an oxygen-free graphene content raging from 0.60 to 1.99 wt%. The influence of graphene content on the morphology of zirconia in composite was examined. High-Resolution Transmission Electron Microscopy (HRTEM) was utilized to study the synthesized powders, allowing for visualization of the chemical homogeneity of the composite and the absence of agglomeration for both graphene and zirconia, which is critical for producing chemically homogeneous fine-grained ceramics from the powder. Mechanisms for the formation of a suspension of oxygen-free graphene during ultrasonic exfoliation and the subsequent synthesis of a composite based on nano-zirconia are experimentally substantiated and proposed.

A technologically promising method for obtaining nanostructured graphene/ZrO2 has been proposed. Its main idea is to use suspensions of graphene and nano-ZrO2 and create conditions for the interaction of graphene sheets and ZrO2 crystallites to form a hybrid nanostructured powder without the formation of new chemical bonds. The oxygen-free graphene sheets with thickness of several nanometers were obtained by sonochemical method in N,N-dimethyloctylamine-aqua emulsion. Nano-ZrO2 powder with average crystallite size of 8.1 nm was synthesized by sol-gel method. The morphology and phase composition of all synthesized objects (nano-ZrO2, graphene, composite) were studied by using a set of instrumental methods (transmission electron microscopy (TEM) and electron diffraction, x-ray diffraction (XRD), electron energy loss spectroscopy (EELS), nitrogen adsorption-desorption, diffusion aerosol spectrometry (DAS) and elemental analysis). It was shown that the proposed method allows obtain chemically homogeneous mesoporous hybrid powders consisting of graphene sheets and ZrO2 crystallites with a size of 8 – 13 nm fixed on them. We investigated an effect of duration of ultrasonic impact to graphite on the morphology of the hybrid and the mechanism of its formation. According to the results of a comprehensive analysis of the obtained data, the mechanisms for the formation of graphene suspension in emulsion and a nanostructured hybrid during the interaction of crystalline ZrO2 and oxygen-free graphene sheets in an aqueous-organic medium was proposed. The developed hybrid nanostructures are highly demanded innovative raw-products in the production of (photo)catalysts for a wide range of processes, sensor, ceramic and electrical materials, and materials for medical and biological purposes.

Two hybrid systems based on oxygen-free graphene and AlCl- and Zn-phthalocyanines have been synthesized in aqueous-organic medium and comparatively studied by optical absorption method. N,N-Dimethylformamide was used as an organic solvent. It has been shown that the presence of oxygen-free graphene in the systems prevents the aggregation of phthalocyanines in aqua medium and contributes to their stabilization in monomeric form. The stability of the resulting hybrid complexes as well as the binding capacity of the components of the systems has been evaluated. The mechanisms of phthalocyanines and oxygen-free graphene interaction in aqueous-organic medium have been proposed.

A method is proposed for the synthesis of nanostructured composites based on graphene and CeO2, which combines sol-gel and sonochemical methods. A feature of the method is that when the graphene content is not more than 2 wt. %, its uniform distribution in the volume of the material is achieved without the formation of an impurity phase. In addition, oxygen-free graphene with a sheet thickness of 3 – 5 nm was used in the synthesis as a suspension obtained by ultrasonic exfoliation in an alkalized by KOH aqua-alcohol solution of dodecylamine. The formation of a composite in a mixed colloid occurs in such a way that the sol-gel transition and subsequent crystallization of nano-CeO2 occur on the graphene sheets. However, the chemical interaction of the latter and CeO2 in the composite is not observed, which contributes to the preservation of the sp2-electrons system of graphene and, as a result, the preservation of its unique electronic properties. The graphene sheets form a layered structure of composite agglomerates, and isolated CeO2 nanocrystals are incorporated into these differently oriented layers. It has been determine that CeO2 dispersion in the composite is higher than in pure CeO2 nanopowder. Estimating the phase and chemical purity of the synthesized composite, it can be argued that the developed method for obtaining nanostructured powders based on graphene and CeO2 is promising as the basis for an economical and environmentally friendly technology for the production of initial substances for fine-grained electrical ceramics.

The comparative study of the catalytic behavior of K-modified CoMoS2-catalysts supported on Al2O3, carbon covered alumina (CCA) and graphene coated alumina (GCA containing 0.4, 1.2, and 1.7% of graphene) in synthesis gas and ethanol conversion (separately) to higher alcohols (HAS) and other oxygenates has been carried out. The supports and catalysts were characterized by N-2 adsorption-desorption isotherms, pyridine adsorption, SEM, EDX, and TEM. In HAS from syngas, the catalyst supported on GCA materials showed better catalytic performances than the catalysts supported on alumina and carbon coated alumina (Cat-GCA > Cat-CCA > Cat-Al2O3). The spectroscopic results have established that the homogenous uniform coating of alumina by graphene nanosheets follows the order: GCA1 (1.7%) > GCA2 (1.2%) > GCA3 (0.4%). The yield of ethanol has a positive correlation with graphene wt. % in GCA. In ethanol conversion, graphene attenuate the interaction of the support/active site KCoMoS2 and with it its selectivity toward dehydrogenation/condensation reactions. The GCA1 supported catalyst exhibits low activity for the water-gas shift (WGS) reaction compared to its counterpart. Explanations of the observed phenomena have been suggested.

Recently, it has become more and more obvious that the use of the unique physical properties of graphene is practically inexhaustible. In our work, we used the surface of oxygen-free graphene sheets to stabilize the AlClPc complex and prevent its agglomeration. A sonochemical method was developed for the preparation of stable suspensions of oxygen-free graphene in a DMF-aqua mixture, the composition and morphology of which were characterized using TEM, DLS, and Raman. Also, a method for the synthesis of hybrid structures based on AlClPc and graphene was developed, and new electrons interactions in them were determined by using of UV-VIS absorption spectroscopy. It was proved that these interactions are due to the graphene participation in surface complex with charge transfer. Graphene also prevents the agglomeration of the AlClPc complex, which is especially valuable for using the synthesized structure in biomedical research. The results obtained show how the use of molecular design techniques makes it possible to create new platforms for vector drag delivery and early diagnosis.

The use of a nanostructured graphene-zirconia composite will allow the development of new materials with improved performance properties and a high functionality. This work covers a stepwise study related to the creation of a nanostructured composite based on ZrO2 and graphene. A composite was prepared using two suspensions: nano-zirconia obtained by sol-gel synthesis and oxygen-free graphene obtained sonochemically. The morphology of oxygen-free graphene sheets, phase composition and the morphology of a zirconia powder, and the morphology of the synthesized composite were studied. The effect of the graphene sheets on the rheological and sintering properties of a nanostructured zirconia-based composite powder has been studied. It has been found that graphene sheets in a hybrid nanostructure make it difficult to press at the elastic deformation stage, and the composite passes into the plastic region at a lower pressure than a single nano-zirconia. A sintering mechanism was proposed for a composite with a graphene content of 0.635 wt%, in which graphene is an important factor affecting the process mechanism. It has been determined that the activation energy of the composite sintering is more than two times higher than for a single nano-zirconia. Apparently, due to the van der Waals interaction, the graphene sheets partially stabilize the zirconia and prevent the disordering of the surface monolayers of its nanocrystals and premelting prior to the sintering. This leads to an increase in the activation energy of the composite sintering, and its sintering occurs, according to a mixed mechanism, in which the grain boundary diffusion predominates, in contrast to the single nano-zirconia sintering, which occurs through a viscous flow.

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al2O3 nanolayer. A method was proposed for applying nanocrystalline γ-Al2O3 to h-BN particles using a sol–gel technique, which ensures the chemical homogeneity of the composite at the nano level. It has been determined that during crystallization on the h-BN surface, the proportion of spinel in alumina decreases from 40 wt.% in pure γ-Al2O3 to 30 wt.% as a result of the involvement of the B3+ ions from the surface nitride monolayers into the transition complex. For comparison, nano-alumina was synthesized from the same sol under the same conditions as the composite. The characterization of the obtained nanostructured powders was carried out using TEM and XRD. A mechanism is proposed for the formation of a nanostructured γ-Al2O3@h-BN composite during the interaction of Al-containing sol and h-BN suspension in aqueous organic media. The resulting composite is a promising model of powdered raw materials for the development of fine-grained ceramic materials for a wide range of applications.

Abstract Combination of sol–gel and sonochemical techniques is suggested for producing a nanostructured graphene–alumina hybrid, which is a promising raw material for manufacturing fine-grained ceramics. This study focuses on the use of dodecylamine both in the sol–gel synthesis of Al-containing particles and in sonochemical graphene exfoliation. It has been shown that, when forming graphene–alumina composite in a reaction mixture of Al-containing sol and graphene suspension, graphene sheets take part as a template in the formation of a hybrid structure. Graphene sheets orient sol particles on their surface due to van der Waals interaction and control growth and direction of oligomeric gel chains. The graphene sheets limit the growth of Al-containing particles, which leads to an increase in the specific surface of the hybrid as compared to an alumina powder sourced from the same sol. The proposed approach enables the preparation of chemically homogeneous composite nanopowders with uniform distribution of components.

In pure DMF, the graphene layering is mainly limited to 5 layers; in the aqua presence, partial association of the lightest graphene sheets with the highest surface energy occurs.

The colloidal processing method was suggested for obtaining chemically homogeneous composite powder based on graphene and nano-alumina. The technique allows integrating a hybrid structure by mixing components at the nanoscale owing to the use of exfoliated oxygen-free graphene sheets and as-prepared Al-containing sol. This method leads to the production of super finely dispersed alumina in the composite and prevention of graphene agglomeration in the bulk material. It turned out that the graphene sheets partially protect the alumina crystallites from deformation and phase transition in the temperature region of 1130 °C, which is critical for pure nano-alumina. The content of graphene sheets, even less than 2 wt%, leads to a decrease in compressibility of the composite compared to pure alumina. The elasticity of the obtained sintered material increased, which makes it promising for the development of fine-grained ceramics with improved mechanical properties, such as hardness, impact strength, and fracture strength. The achieved improvements in the structure and features of the graphene–alumina composite, as well as dilatometry properties, are of high demand in the production of medical materials with high biocompatibility, sensors, materials with low electrical resistance, catalysts, adsorbents, Li-battery electrodes and facilitated high impact materials.

A comparison study of the effect of different carbon-containing materials used as carriers on transition metal sulfide (TMS) catalyst behavior in the synthesis gas conversion has been conducted. Supports used for the synthesis of alcohols from syngas via KCoMoS2, in this project are γ-Al2O3, Carbon-Coated Alumina (CCA), Graphene coated Alumina (GCA), NiAl2O3.CuO, and different types of low-cost commercial activated carbons such as fabric active sorption (TCA), non-woven activated material (AHM), AG-3, OBC-1, DAC, and BAW. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Fluorescence (XRF), and N2 physisorption were used to characterize the carriers and catalysts. The obtained results have shown that GCA is more effective than alumina and CCA to increase the yield ratio between alcohol and hydrocarbons (YROH/HCs), besides it has shown low selectivity for CO2. The graphene ribbons have played a role in decreasing the interaction between alumina and the active phase which decreased the hydrogenation reaction. The used types of carbon materials showed different supporting efficiency to synthesis of alcohol from syngas. The activities depend on the support nature have shown trends to increase in the following order: Al2O3 < CCA < BAW < TCA < Ag3 < AHM > GCA.

New hybrid graphene and aluminum phthalocyanine structures are synthesized (graphene is prepared with the sonochemical method in N,N-dimethylformamide). The physicochemical properties of these hybrid systems are studied with transmission electron microscopy, Raman spectroscopy, and optical spectroscopy. We show that graphene in the system prevents the aggregation of aluminum phthalocyanine and leads to its stabilization in monomeric form. The results may be used to obtain new materials for various sciences and technologies.

Nanostructured composite particles of nano- and submicron sizes were synthesized by a combination of sol-gel and sonochemical techniques. Their graphene content was 0.8-0.9 wt%. These layered particles consisted of graphene sheets in which zirconia nanocrystals were discretely incorporated. The synthesized powders were characterized using XRD, TEM, HRTEM, diffusion aerosol spectrometry and elemental analysis. A comparison of the compressibility modulus, limit values of linear section deformation and compressibility factor shows that the compressibility of the composite is difficult to achieve compared to that of pure zirconia, apparently, due to the low elasticity of graphene sheets.

Nanocomposites based on graphene and Co3O4, MoO3, NiO and WO3 have been synthesized by a combination of sol-gel and sonochemical techniques. N,N-Dimethyloctylamine was used for the formation and stabilization of metal-containing sols and for stabilization of graphene suspension. The structure, morphology and composition of graphene-based nanocomposites were investigated by means of transmission electron microscopy, X-ray diffraction, Raman and FT-IR spectroscopy. It has been shown that the proposed method allows obtaining the hybrid nanoparticles with 10 to 200 nm size consisting of Co3O4, MoO3, NiO or WO3 crystallites coated with the graphene layers. This method enables preparing chemically homogeneous composite nanopowders for the production of high performance (photo)catalysts and fine-grained ceramics for the energy sector with uniform distribution of components within a volume. It has beens proven experimentally that graphene sheets are involved in the formation of hybrid nanoparticles based on metal oxides as structuring and texturing agents. These results show promise in the synthesis and fabrication of well-defined graphene-based functional materials, including graphene-ceramic hybrids, with a broad scope of applications.

In the present investigation, the cryochemical approach was used for the improved synthesis of nanocrystalline metal oxides (e.g., NiO, Fe2O3, CeO2) and NaNO3 salt. It was shown that the solutions and sols can be treated with a liquid nitrogen stream (−196 °C) to increase the powder dispersity by 3–18 times and to increase their specific surface area by an order of magnitude. The proposed approach also reduces the agglomeration of the nanoparticles, and at the same time, results in NiO, Fe2O3 and CeO2 crystallite sizes of less than 10 nm (quantum dot size regime). The diameter of NaNO3 salt crystallites could also be reduced to ≤50 nm by freezing in a liquid nitrogen atmosphere, which is a significant improvement over analogous salts obtained by traditional methods (average diameter 300–1000 nm). The characterization of the obtained nanopowders was carried out using X-ray diffraction, transmission electron microscopy, surface area measurements and diffusion aerosol spectrometry (DAS). It was determined that the addition of 3–15 wt % of NaF to the NaNO3 solution prior to its cryogenic treatment results in a further decrease in the particle size of the obtained crystalline salt. NaF creates a protective coating with a thickness of 2–3 nm on the surface of NaNO3 crystallites, preventing their association. The results obtained show that the cryochemical processing of the solutions during the preparation phase of production allows nanopowders to be obtained with improved morphological and textural characteristics without significant increase in technical development costs.

— Al- and Zr-containing sols intended for producing Al 2 O 3 and ZrO 2 nanocoatings, respectively, were prepared by a sol–gel process using N , N -dimethyloctylamine (DMOA) and acetylacetone (acacH). Aluminum and zirconyl nitrates were used as metal precursors. The DMOA/Al and DMOA/Zr molar ratios were 1 and 2, respectively, and the acacH/DMOA molar ratio was 1.5 in both cases. The sols were synthesized at a temperature of 80–90°C and then were evaporated at 90–95°C to a gel state. The resultant gels were characterized by differential thermal analysis, differential scanning calorimetry, and electron impact mass spectrometry. Measurements in the temperature range 20–500°C in air and Ar showed that the Zr-containing material was more thermally stable (decomposition temperature of 304–308°C) than its Al-containing analog (decomposition temperature of 225–230°C). According to the mass spectrometry analysis data, the gels contained metals as acetylacetonate complexes having strong M–O bonds and coordinated molecular DMOA. The nature of the metal was shown to influence both the thermal stability of the gel in which it is present in a chemically bound state and the mechanisms of the processes involved in its thermolysis.