N. E. Sorokina

Anodic Oxidation of Graphite in 10 to 98% HNO3

Systematic studies into the anodic oxidation of natural fine-particle graphite in 10 to 98% HNO3are described. The concentration ranges of the formation of stage I–IV graphite nitrates are determined. Below CHNO3 = 55%, no graphite intercalation compounds are detected by x-ray diffraction. The electrochemical oxidation of graphite in dilute HNO3yields graphite oxide phases. Their formation seems to be preceded by intercalation and hydrolysis, which occur in parallel. The properties of the oxidation and hydrolysis products are shown to depend strongly on the process parameters.

The choice of oxidizers for graphite hydrogenosulfate chemical synthesis

Abstract The features of chemical oxidation of graphite in H2SO4 are discussed. Measurements of currentless potentials of K2Cr2O7, KMnO4, (NH4)2S2O8 and complex salt Ce(SO4)2·4(NH4)2SO4·2H2O solutions in 96% H2SO4 were carried out. Correlation of the redox potentials of oxidizers to the stage number of graphite hydrogenosulfate (GHS) is established. It is proposed to use the standard redox potential scale to choose the oxidizers for the formation of a given stage GHS. On the basis of this approach, numerous oxidizers for GHS formation are considered. For the first time, ozone and Ce(IY) sulfate were applied for GHS production. The stage 1 GHS is obtained in accordance with standard potentials of these oxidizers.

The specific surface area and porous structure of graphite materials

Transformations of the specific surface area and porous structure of carbon materials based on graphite were studied by low-temperature adsorption of nitrogen. Exfoliated graphite and graphite foil were found to have a developed (compared with the initial graphite) surface (up to 90 m2/g) and a porous structure formed by slit-like mesopores with a characteristic radius of ∼20 Å. The determining influence of the method of synthesis on the adsorption properties of materials was demonstrated for the first time.

Chemical synthesis of graphite hydrogenosulfate: Calorimetry and potentiometry studies

In the present work dynamics of sulfuric acid intercalation into graphite by chemical oxidation were investigated by means of the calorimeter and potentiometer techniques. Phase composition of intermediate and end-products of the reaction was investigated by X-ray diffraction.

Surface modification of carbon fibers with nitric acid solutions

We have studied the surface modification of carbonized carbon fibers with nitric acid solutions, compared the effects of 60 and 98% HNO3, and examined the influence of the anodic polarization of the fiber for surface functionalization. Unmodified and surface-modified carbon fibers have been characterized by a variety of physicochemical techniques.

Stability limits of graphite intercalation compounds in the systems graphite-HNO3(H2SO4)-H2O-KMnO4

AbstractThe formation of binary graphite intercalation compounds (GICs) with nitric and sulfuric acids in the presence of a strong oxidant has been studied by x-ray diffraction and potentiometry in a wide range of acid concentrations. The redox potential of the oxidizing solution and the intercalation ability of the acid are shown to influence the stage number (the number of graphite layers between two successive intercalate layers) of the forming GIC and the concentration ranges of GIC formation. The (

Preparation and Properties of Exfoliated Graphite Doped with Nickel and Cobalt Oxides

E_{H_2 }

Intercalation of Graphite in the Ternary Systems C–HNO3–R (R = H2O, CH3COOH, H3PO4 , H2SO4)

)-H0 (redox potential of the oxidizing solution-Hammett function of the acid) stability fields of graphite nitrate and graphite bisulfate are presented. Our results are the first to demonstrate that KMnO4 extends the concentration ranges of GIC formation and reduces the threshold acid concentration for the synthesis of binary GICs (to 40%).