Synthesis,structure and properties of fluorinated graphite

Fluorine-graphite intercalation compounds, C₂F to C₁₆F were synthesized by various methods. C-F bonds range from ionic to semi-covalent. These properties of C-F bonding give to fluorinated graphite metallic conductivity, higher hydrophilicity than graphite and high reduction potential. The c-axis and in-plane structures are governed by C-F bonding, fluorine intercalation rate and host graphites.     

Synthesis, properties, and structure of tetrazoles: Certain achievements and prospects

The review generalizes and systematizes the results of research on the synthesis and properties of tetrazole derivatives obtained in the Belarusian State University within the last decade. The main attention is fixed on important directions in the tetrazole synthesis: the acid-catalyzed N-alkylation, the reactions of primary amines with triethyl orthoformate and sodium azide followed by the heterocyclization of imidoyl azides, and on the transformation of the obtained 1-aryltetrazoles into 1-aryl-5-aminotetrazoles. The results of quantum-chemical and X-ray investigations as well as aspects of the practical application of tetrazoles are reviewed.     

The production and properties of polylactide composites filled with expanded graphite

Composites have been produced by melt-blending biodegradable polylactide (PLA) with commercially available expanded graphite (EG). Using different techniques of addition, the manifold effects of EG on PLA molecular, thermo-mechanical and fire-retardant properties were evaluated. The EG nanofiller provides PLA composites with competitive functional properties. They have a high rigidity, with Young's modulus and storage modulus increasing with EG content. They also have excellent thermal stability while preserving the glass transition and melting temperature of the original PLA matrix. Purification and pre-dispersion of EG nanofiller proved beneficial for preserving PLA molecular weights and led to improved mechanical performance. The presence of dispersed graphene nanolayers in PLA significantly accelerated the polyester crystallization process. The flame retardant properties also displayed improvements with a large decrease in the maximum rate of heat release as recorded by cone calorimetry, whereas the horizontal burning test (UL94 HB) was successfully passed revealing non-dripping and char formation.     

A novel approach for synthesis of expanded graphite and its enhanced lithium storage properties

Relying on the great success in portable and smart devices, lithium ion batteries (LIBs) have been considered as one of the leading technologies in electric veh...     

Synthesis,properties, and structure of intercalated graphite fluosulfonate fluorides

Graphite fluosulfonate fluorides of the composition C₂F_x−y(SO₃F)_y (x+y≈1) have been synthesized. The new compounds can be treated as derivatives of graphite fluorides C₂F_x(x≈1) in which approximately 1/50 of the F atoms have been replaced by SO₃F groups. The intercalates based on the new matrices have been studied by X-ray phase analysis, IR spectroscopy, mass spectrometry, and thermography. The ability of the intercalates to absorb various substances is investigated. It is shown that the introduction of a few SO₃F groups into the C₂F_x matrices significantly changes the physicochemical properties and the structure of intercalates; in particular, for intercalates of stage II structure this expands the scope of substances that can penetrate into interlayer spacings. The dependence of the penetration ability of the substances on the van der Waals sizes of their molecules makes intercalates resemble zeolites in properties. Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Novosibirsk. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No, 1, pp. 144–151, January–February, 1995 Translated by I. Izvekova     

Texture and catalytic properties of palladium supported on thermally expanded natural graphite

Data about preparation and properties of palladium catalysts on porous supports prepared by intercalation and subsequent thermal expansion of natural graphite are presented. Some relations between the structure of the graphite support, the state of supported palladium and its catalytic properties in the model reaction of cyclohexene liquid-phase hydrogenation were established. This revised version was published online in June 2006 with corrections to the Cover Date.     

Status and future prospects for use of the graphite furnace for elemental trace analysis of liquids and solids

Summary An overview of the versatility and use of the graphite furnace for elemental trace analysis of liquids and solids using spectrochemical detection is presented. The analytical performance of conventional graphite furnace atomic absorption spectrometry is compared to other popular state of the art spectrochemical techniques with respect to detection power, precision, sample compatibility and throughput. Some applications of the graphite furnace to practical problem solving in trace analysis are highlighted, including its use with atomic absorption, coherent forward scattering, laser excited atomic fluorescence, laser enhanced ionization and coupled methodologies. Prospects for future use and evaluation are given.     

Plasma-chemical synthesis and properties of polymer semiconductors and prospects for their use

The properties and structures of semiconducting polymers prepared by chemical and electrochemical techniques and plasma-synthesized polymer semiconductors were compared. The advantages and disadvantages of these techniques were considered. The potential areas of application of semiconducting polymer films prepared by plasma polymerization were demonstrated.     

Influences of coupling agent on thermal properties, flammability and mechanical properties of polypropylene/thermoplastic polyurethanes composites filled with expanded graphite

In this study, polypropylene (PP)/thermoplastic polyurethanes (TPU) filled with inorganic intumescent flame retardant expanded graphite (EG) was prepared by melt blending in a twin-screw extruder. The thermal stability, fire retardancy, mechanical properties, and fracture morphology of PP/TPU composites with treated and untreated EG were investigated by thermogravimetric analysis, cone calorimeter, and scanning electron microscope. The results showed that both untreated and treated EG can greatly enhance the thermal stability and fire resistance of polymer matrix materials. Compared with untreated EG, treated EG can further improve the flame retardancy of the composites. For example, treated EG can further reduce the heat release rate, total heat release, and CO emissions of the composites in the combustion. Surface treatment of EG could significantly improve elongation at break and impact strength of PP/TPU/EG composites due to its enhanced interfacial adhesion and the good dispersion of EG particles in the polymer matrix.     

Modified expanded corrole-ferrocene conjugates: syntheses, structure and properties

Syntheses, characterization and properties of expanded corrole-ferrocene conjugates are reported. Ferrocenyl group are covalently linked to the corrole macrocycle through three different spacers groups. The synthetic strategy involved prior insertion of ferrocene with spacers to the dipyrromethane unit followed by a "3+2" acid-catalyzed oxidative coupling methodology. The optical and emission data of the expanded corrole-ferrocene conjugates depend on the nature and length of the spacer groups and the maximum effects are seen where ferrocene is directly linked to the meso carbon of macrocycle. The single crystal X-ray structure of two expanded corrole-ferrocene conjugates; [22]pentaphyrin (1.1.0.1.0) with different meso substituents, clearly reveal shortening of the C-C bond length linking the meso carbon and the aryl substituent containing the ferrocene moiety relative to meso aryl substituents without ferrocene. The results suggest that an electronic interaction between the two pi systems. Electrochemical data reveal harder oxidation for the ferrocene unit in the conjugates relative to free ferrocene; this suggests the electron donating nature of the ferrocene. The first corrole ring oxidation shows easier oxidation relative to 1 and the magnitude of shifts in potential is inversely proportional to the length of spacer. The molecular first hyperpolarizabilities (beta) measured at 1064 nm by HRS method vary in the range 20-32x10(-30) esu and imply that the beta values can be increased by enhancing the number of mobile electrons in the conjugation. The conjugates form 1:1 metal complex with the Rh(I) where rhodium is coordinated to one amino and one imino nitrogen of the dipyrromethane unit.     

Nickel oxide/expanded graphite nanocomposite electrodes for supercapacitor application

Nickel oxide/expanded graphite (NiO/EG) nanocomposites with different loading of EG were prepared through chemically depositing Ni(OH)₂ in EG followed by thermal annealing and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET) isotherm and electrochemical measurements. The prepared NiO/EG composites were found to be crystalline and highly porous with high specific surface area and pore volume. SEM analysis reveals uniform porous morphology for NiO in the NiO/EG-60 nanocomposites which shows good specific capacitance (510?F?g^?1) at a current density of 100?mA?g^?1 in 6?mol?L^?1 KOH measured by chronopotentiometry employing a three-electrode system. The specific capacitance retention of the NiO/EG-60 nanocomposites was found to be ca. 95% after 500 continuous galvanostatic charge–discharge cycles, indicating that the NiO/EG nanocomposites can become promising electro-active materials for supercapacitor application.     

Synthesis and properties of residual graphite nitrate obtained by treatment of graphite nitrate with water

The possibility of obtaining residual graphite nitrate by water treatment of graphite nitrate and its subsequent drying was studied. The expansion coefficients were determined in the temperature range 500–900°C with a step of 100°C for the samples obtained.     

Preparation and thermal properties of expanded graphite/paraffin/organic montmorillonite composite phase change material

Expanded graphite (EG)/paraffin/organic montmorillonite (OMMT) composite phase change material (PCM) was prepared by using melt intercalation method. The microstructure of EG/paraffin/OMMT is observed by scanning electron microscope (SEM). The thermal properties are investigated by differential scanning calorimetry (DSC). The mass loss of EG/paraffin/OMMT after 50 heating cycles was measured for investigating the influence of EG and OMMT on the thermal properties of paraffin. The results show that EG and OMMT have the ability of adsorption and shape-stability. The melting point EG/paraffin/OMMT is decreased slightly with an addition of paraffin and the latent heat of EG/paraffin/OMMT is determined by the mass ratio of paraffin. The heat transfer efficiency of EG/paraffin/OMMT is strengthened and the heating time is decreased to one-sixth of that of paraffin by addition of EG and OMMT. The thermal stability of EG/paraffin/OMMT is improved by addition of OMMT.     

Retracted: EMI shielding effectiveness of expanded graphite and reduced graphene oxide

Retraction: Gairola, SP, Gairola, P, Shah, SK, Gupta, R. EMI shielding effectiveness of expanded graphite and reduced graphene oxide. J. Chin. Chem. Soc. 2018. https://doi.org/10.1002/jccs.201800189 . The above article, published online on 1 October 2018 in Wiley Online Library ( https://onlinelibrary.wiley.com ), has been retracted by agreement between the corresponding author, the journal's Editor‐in‐Chief, Dr. Yu‐Tai Tao, the Chemical Society Located in Taipei, and Wiley‐VCH Verlag GmbH & Co. KGaA. The retraction has been agreed due to several images across Figures 1, 2 and 3 within the article having been duplicated from other publications. The corresponding author apologizes for the inconvenience caused.     

New floating photocatalysts based on expanded graphite and anatase

A new method for production of composites constituted by expanded graphite, amorphous carbon, and titanium dioxide was suggested. The structure of the materials obtained was studied, and it was demonstrated that they show promise as photocatalysts for water treatment to remove organic contaminants.     

Simulation and synthesis of graphene oxide from expanded graphite

Russian Journal of General Chemistry - Expanded graphite oxide and multilayered graphene oxide have been synthesized. The processes of thermal expansion of intercalated graphite and oxidation of...     

Boron-containing small rings: synthesis,properties, and application prospects

The studies published over the last 15 years on the synthesis, physicochemical properties, and application prospects of saturated and unsaturated three- and four-membered boron-containing carbocycles with one boron atom — boriranes, borirenes, boretanes, and 1,2-dihydroboretanes — are summarized and systematized. Original methods for the synthesis of boriran(en)es based on photochemical isomerization of organoboranes, double hydroboration of acetylenes with imidazol-2-ylideneboranes, and [2+1]-cycloaddition of borylenes (:B–R) to unsaturated compounds are considered. A new method for the synthesis of substituted boriranes by Cp₂TiCl₂-catalyzed cycloboration of olefins with boron halides in the presence of metallic Mg is presented. The not numerous data on the synthesis of four-membered boracyclanes (boretanes and 1,2-dihydroboretes) based on thermal isomerization of cyclopropylboranes, [2+2]-cycloaddition of methyleneboranes to nitriles, 1,1-diethoxyethylene, or alkynes, as well as transmetallation of 1,8-dilithium naphthalene and titanacyclobutenes with boron halides, are summarized.

     

Low density polyethylene,expanded polystyrene and expanded polypropylene: Strain rate and size effects on mechanical properties

Polymeric foam materials may be used as energy absorbing materials for protection in impact scenarios, and design with these materials requires the mechanical properties of foams across a range of deformation rates, where high deformation rate testing often requires small samples for testing. Owing to their cellular macrostructure, and the large deformations that occur during loading of foams, the measured stress-strain response of a foam material may be influenced by the sample size. In this study, the mechanical properties of three closed-cell polymeric foams (Low Density Polyethylene, Expanded Polystyrene and Expanded Polypropylene) at two different densities were investigated over a range of deformation rates from 0.01 s⁻¹ to 100 s⁻¹. For each foam material, three different nominal sample sizes (10 mm, 17 mm and 35 mm) were tested. On average, the polymeric foam materials exhibited increasing stress with increasing deformation rate, for a given amount of strain.Density variation was identified at the sample level, with smaller samples often exhibiting lower density. Expanded Polystyrene demonstrated the highest variability in sample density and corresponding variability in mechanical response, qualitatively supported by observed variations in the macrostructure of the foam. Expanded Polypropylene exhibited variability in density with sample size, and observable variability in the material macrostructure; however, the dependence of the measured mechanical properties on sample size was modest. Low Density Polyethylene was found to have a relatively consistent cell size at the macrostructure level, and the material density did not vary significantly with sample size. In a similar manner, the dependence of measured mechanical properties on sample size was modest. The effect of sample size was identified to be material specific, and it is recommended that this be assessed using sample-specific density measurements and considering different sized samples when testing foam materials.     

Effect of expanded graphite/layered-silicate clay on thermal, mechanical and fire retardant properties of poly(lactic acid)

Preparation of PLA based nanocomposites was carried out by using two different nanofillers: expanded graphite and organically modified montmorillonite. The addition and co-addition of these nanofillers to PLA using the melt-blending technique provides nanocomposites that showed significant enhancements in rigidity, thermal stability and fire retardancy of the polymer matrix. The presence of dispersed graphite nanolayers in PLA significantly accelerated the polyester crystallization, whereas the essential increase of thermal resistance is mainly connected to the addition of organoclay. The structure of the nanocomposites was examined by Wide Angle X-ray Scattering Analysis and Transmission Electron Microscopy. The improvement of thermal and mechanical properties obtained by the presence of both nanoparticles in PLA were associated to the good (co)dispersion and to the co-reinforcement effect, whilst the fire retardant properties were found to be related to the combined additive action of both nanofillers.