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.

A technologically promising method for obtaining nanostructured graphene-ZrO₂ has been proposed. Its main idea is to use the 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 the sizes 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 aqua-organic medium were 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.

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 is used in the synthesis as a suspension obtained by ultrasonic exfoliation in an alkalized by KOH water-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, chemical interaction of the latter and CeO₂ in the composite is not observed, which contributes to the preservation of the sp² electron 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 is determined 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.