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It is shown by physical methods that the preliminary preparation of samples affects the structure and properties of graphite oxide and partially reduced graphite oxide. The graphite oxide drying technique as the last synthesis stage determines its morphology and structural properties. At drying by sublimation method, the state of graphite oxide in aqueous suspension before the beginning of the process of self-ordering of its sheets is fixed, the data of X-ray diffraction analysis testifies its X-ray amorphous state, the dried graphite oxide appearance is a light yellow powder. Drying of graphite oxide aqueous suspensions at temperatures above room temperature is accompanied by the ordering of the graphite oxide structure under the action of the surface tension and Van der Waals forces with the dark brown film formation. It is shown by scanning and transmission microscopy methods that the method of separation of partially reduced graphite oxide from glass substrates, on which the product is dried, can lead to the formation of wrinkled or roll-shaped structures. When graphite oxide is examined by transmission electron microscopy, even a short exposure to ultrasound (used in the conventional method of depositing the material on a copper grid prior to examination) results in wrinkling and partial curling of the edges of graphite oxide nanoparticles. Mechanical grinding of graphite oxide leads to disordered graphite oxide structure and to the interplanar spacing increase.

The paper presents the investigation results of the morphology of carbon nanoparticles formed during liquid-phase exfoliation of thermally expanded graphite in tert-butanol. The thermally expanded graphite used in this work was obtained by thermal expansion of graphite nitrate with acetic and formic acids in the thermal shock mode at 500°C and 900°C. Initial cointercalate was shown by powder X-ray diffraction analysis to be the mixture of the II^nd and the IV^th stage intercalation compounds. It has been established by transmission electron microscopy that dispersions of carbon nanoparticles formed during the exfoliation of thermally expanded graphite in tert-butanol via sonication contain mainly few-layer graphenes, the planar dimensions of which reach 8 μm. The influence of the conditions for thermally expanded graphite obtaining on the morphology of resulting carbon nanoparticles is discussed. Dispersions based on thermally expanded graphite obtained at a lower temperature, in addition to few-layer graphenes, also contain a significant amount of amorphous carbon particles with planar sizes up to 100 nm.

Dispersions of graphene nanoparticles were obtained by liquid phase exfoliation of thermally expanded graphite in ethanol as well as tert-butanol via sonication. Initial thermally expanded graphite was obtained by heat treatment in the shock mode of ternary graphite nitrate intercalation compound with formic and acetic acids. Investigation of the graphite nitrate intercalation compound and thermally expanded graphite structural characteristics by X-ray diffraction analysis has been carried out. The microstructure and morphology of the obtained graphene particles were studied by transmission electron microscopy.

The sonication impact on the process of the Hummers graphite oxide reduction by thiourea was investigated. It was found that treatment of the graphite oxide with thiourea leads to the partial removing of oxygen-containing and formation of sulfur-containing functional groups on the graphite oxide surface. The low-power ultrasound promotes an increase in the graphite oxide surface functionalization by sulfur. The morphology of the partially reduced and functionalized graphite oxide particles was studied by using the scanning and transmission electron microscopy. It was shown that ultrasound promotes the formation of a hydrogel with a highly developed surface.

Тhe Boehm titrimetric method gives distorted results when determining total quantity of acid groups total quantity in Hammers’ graphite oxide. It was established that the additional acidity of the aqueous phase of the Hammers graphite oxide suspension is due to intercalated sulfuric acid. The adding alkali during the acid-base titration is accompanied by the reaction of Hammers’ graphite oxide decarboxylation. Such an effect was not observed for an aqueous suspension of Brodie’s graphite oxide.