Development of the Protection Coat for Metallic Structures Based on the Intercalated Graphite Compounds

The practicability of introducing a synthesized graphite compound, intercalated with oxygen, into the protection coat is grounded. The composition and the method of manufacturing a protection coat based on the oxidized graphite, which does not require preliminary preparation of the metal structures surface before welding with an open arc, have been developed. The effect of the oxidized graphite content in the composition of the protection coat on its thermal stability and thermal expansion coefficient is analyzed. The main technological characteristics of the developed protection coat have been investigated and their compliance with the basic criteria for constructing protection coats has been confirmed.

ELECTROCHEMICAL DISPERSION OF GRAPHITE IN 58% NITRIC ACID TO PRODUCE MULTILAYER GRAPHENE OXIDE

Electrochemical oxidation of graphite powder in 58% HNO3 was studied. Samples of oxidized graphite were obtained with a imparting of the amount of electricity 500, 700, 1500 mAh g-1. The character of the galvanostatic dependencies allows to select a region of the formation of intercalated compounds of graphite prior to the accumulation of quantity of electricity of 500 mA h g-1. It was found that when the quantity of electricity of over 700 mA h g-1 the process of electrochemical peroxidation of intercalated graphite begins with the formation of multilayer graphene oxide, as confirmed by comprehensive studies using X-ray diffraction, scanning electron microscopy, FTIR spectroscopy, laser diffraction. The synthesized multilayer graphene oxide is characterized by the presence of a spectrum of oxygen-containing functional groups, mainly hydroxyl, as well as carboxyl, epoxy and alkoxyl. X-ray images show a peak at 2θ = 11.45° which intensity increases for re-oxidized graphite compounds and also indicate the formation of a multilayer graphene oxide with an interlayer distance of 7.8 Å. The synthesized material in aqueous suspensions under the action of ultrasound is dispersed with a 7-11-fold reduction in particle size. Graphene layers remains layered structure but the degree of their deformation increases, and the thickness of the layers decreases with an increase in the imparted amount of electricity.

Removal of Lead by Oxidized Graphite

Lead ion adsorption on the surfaces of pristine and oxidized graphite is studied quantitatively using X-ray photoelectron spectroscopy (XPS) and standard electrochemical measurements. The XPS analysis confirmed the oxidation of graphite, yielding a final composite consisting of 15.97% of oxygen and 84.03% of carbon in comparison with the pristine graphite powder consisting of 6.13% oxygen and 93.87% carbon. The adsorption of lead (II) ion was confirmed by the peaks observed at 138 eV and 143.8 eV, associated with the emissions from Pb4f 7/2 and Pb4f 5/2, respectively. The effective concentration of Pb2+ ion and the optimum dosage of oxidized graphite were calculated to be 400 µM and 200 mg, respectively. Adsorption capacity of bare graphite was 41.18%, whereas that of oxidized graphite was 73.3%. The present results show that graphite oxide is a candidate material for the adsorption of Pb2+ ion from water.

One-spot synthesis of FeOOH/rGO composites by ferrous-ion-induced self-assembly of graphene oxides with different degrees of oxidation

In this study, graphene oxide sheets with different oxidation degrees were reduced by ferrous ion for coating FeOOH nano particles on reduced graphene oxide (rGO) matrix to synthesize FeOOH/rGO composites. The effect of the degree of oxidation on the morphology and chemical structure of FeOOH/rGO was studied using scanning electron microscopy, Raman spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller surface area analysis. The particle size of FeOOH crystallites was approximately 100 nm, and they were distributed uniformly on the surface and in the pores of FeOOH/rGO. FeOOH/rGO prepared with mildly oxidized graphite had fewer defects, higher specific surface area, and higher FeOOH content than FeOOH/rGO prepared with highly oxidized graphite. These features resulted in better electrochemical properties, such as larger specific capacitance and lower charge transfer resistance.

Research of Flame-Retardant and Physical and Mechanical Properties of Thermally Expanding Sealing Tapes Based on Polyolefin Thermoplastic Elastomers

A study of the flame-retardant (FR) properties, the degree of expansion (DE) and the strength properties of thermally expanding sealing tapes (TST) based on polyolefin thermoplastic elastomers is presented. Experimental TST based on ethylene vinyl acetate rubber (БК-E), and a semi-crystalline copolymer of ethylene and propylene (БК-V) with additives of oxidized graphite (OG) were obtained on laboratory equipment. DE, categories of FR and strength properties of БК-E and БК-V differ slightly. The morphology of the char foams of the obtained compositions was determined. Based on the summary of the results it was found that the composition of БК-E has a better FR in comparison with БК-V. It is estimated that this is primarily due to the nature of the polymer matrix of the compositions, as well as the distribution of components in it, in particular, OG, and their interaction with each other during the combustion process. It is shown that the properties of the developed TST are at the level of the existing ones. A further series of research is expected.

Adsorption of organic pollutants from the aqueous phase using graphite as a model adsorbent

Although graphite is not effective as an adsorbent in water treatment, it provides a homogenous, non-porous, carbonaceous structure that is ideal for studying fundamental adsorption mechanisms. High-purity graphite powder (C content 99.5%) was oxidized in an ozone stream, producing a near-surface oxygen content of 5.9 at.%, and was used together with the virgin material to establish adsorption isotherms for organic compounds in aqueous solutions. We examined how the aromaticity and substituents of the adsorptives affect adsorption on the model-activated carbon surface. For both virgin and oxidized graphite, the adsorption capacity for the aromatic compounds decreased in the order 1-naphthol > 2-methoxynaphthalene > naphthalene > anisole > phenol, with significant differences in the adsorption capacities of the two graphite species observed only for anisole, naphthalene, and 1-naphthol. The Freundlich constants (KF) for the five compounds on virgin graphite were 23.9, 10.3, 5.5, 1.4, and 0.8 (nmol mg−1 )/(µmol L−1) n, respectively. Naphthalene and 1-naphthol were slightly more adsorbed on the virgin material, whereas oxidized graphite had marginally better adsorption properties for anisole. The results underline the importance of dispersive and π– π interactions in the adsorption of organic compounds on carbonaceous adsorbents; a second aromatic ring in 1-naphthol and 2-methoxynaphthalene greatly increased the adsorption capacity for these compounds compared with their one-ring counterparts phenol and anisole. Differences were also observed in the adsorption of compounds containing hydroxyl or methoxy substituents, which have electron-donating properties (a resonance effect) but different electron-withdrawal characteristics (caused by induction). Two amino acids occurring as zwitterions, l-tryptophan and l-tyrosine, were also tested as adsorptives. l-Tryptophan, which has a larger aromatic system, achieved higher loading on graphite, suggesting an adsorption mechanism primarily governed by dispersive and π– π interactions for these two ionic compounds as well.