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Polyester-urea coatings were synthesized from corn oil with the help of a series of reactions in three different compositions by varying the amount of urea. Out of all the synthesized compositions, the best composition was optimized based on various parameters. The optimized composition was used as a matrix and graphene oxide (GO) was incorporated in three ratios, for the formulation of corn oil-based CPEUr@GO nanocomposites. Fourier transform infrared spectroscopy was used to confirm all the reactions. The physico-mechanical properties of CPEU[r.sub.2] coating were found to be the best among all the compositions. Therefore, CPEU[r.sub.2] was selected as a matrix for the inclusion of GO nanosheets to prepare CPEU[r.sub.2]@GO nanocomposites. Thermogravimetric analysis results showed that incorporation of GO enhanced the thermal stability of CPEU[r.sub.2] up to 325[degrees] C. The anticorrosive studies revealed the high impedance value of 6.5 * [10.sup.5] [ohm].[cm.sup.2] in case of CPEU[r.sub.2]@G[O.sub.0.5]. Furthermore, it can be concluded that the inclusion of 0.5 wt% GO proved to be the optimized amount to produce sustainable CPEU[r.sub.2] coatings with good performance. These CPEUr@GO nanocomposite coatings can be used for various protective purposes owing to their excellent physico-mechanical thermal as well as anticorrosive performance. Highlights * Corn oil-based polyester-urea, CPEUr, coatings were synthesized in three different compositions. * The best composition was used as a matrix for the formulation of CPEUr@GO nanocomposites. * Graphene oxide of 0.5 wt% was found to be the optimum quantity required to modify CPEUr matrix. * Thermal stability, mechanical durability as well as corrosion resistance performances were enhanced. * The environment friendly approach is suitable for the development of corrosion protective coatings. KEYWORDS corn oil, graphene oxide, nanocomposites, polyurea, 1 | INTRODUCTION Polyurea (PUr) coating represents a recent advancement in the field of coating technology, within the realm of urethane coatings chemistry. (1) PUr coatings exhibit notable mechanical strength [...]

The rapid use of additive manufacturing (AM) in electronic industry identifies the need of flexible electrically conductive materials suitable for 3D printing. Challenges like buckling of flexible filament and complexity in addition of conductive fillers makes pellet-based extrusion the most suitable alternative for part printing. In the present work, graphite powder is combined with ethylene vinyl acetate (EVA) to print flexible electrically conductive parts. EVA graphite composite with filler loading up to 30% has been investigated for its electrical conductivity and part printability. The composite made was found electrically conductive and suitable for part printing. The parts were printed on a CNC milling machine by using a retrofitted material extrusion tool with nozzle of 0.4 mm diameter and temperature range of 130-140[degrees] C. Parts were printed on a detchable heating bed placed on the milling machine setup. Samples of EVA with graphite filler by weight of 5%, 10%, 20%, and 30% were printed and were checked for electrical conductivity. When the filler content was increased from 10% to 20%, the electrical resistance of the composite was reduced by 62.6%. The presence and uniform dispersion of graphite flakes in the polymer matrix of EVA were guaranteed by the rheological and morphological characterization of the composite. Applications of 3D printable flexible electrically conductive parts lies in numerous domains including biosensors, wearable health monitoring devices, capacitors, field effective transistors, light emitting diodes, solar cells, and electronic displays. Highlights * CNC milling machine-assisted 3D printing is used for part printing. * Graphite powder is combined with EVA pellets. * Pellet-based extrusion is used to print flexible parts. * 3D printability of parts with resistivity 32.64 [ohm]-cm was achieved. KEYWORDS additive manufacturing (AM), ethylene vinyl acetate (EVA), extrusion, flexible electrically conductive polymers, graphite powder, 1 | INTRODUCTION The fundamental advantage of polymer-based additive manufacturing (AM) is rapid fabrication of parts having complicated geometries. Low weight, low cost, nontoxic nature, and workability make polymer a [...]

Multi-walled carbon nanotubes (MWCNTs) were synthesized by a microwave method. MWCNTs had filamentous shapes (10 [micro]m) and were intertwined in bundles (40-60 nm diameter). The rapid oxidation of MWCNTs with a loss of 90% of weight was observed from 530 to 630[degrees]C. 2% Residue was present at 630[degrees]C, which gradually decreased to 1.2% at 1000[degrees]C. In a silicone elastomer, increased thermal conductivity at a concentration of 8% MWCNTs was observed. The highest thermal conductivity of the nano-modified elastomer was 0.48 W/m[degrees]C with 8.0 wt% MWCNTs. The highest electrical conductivity was 2.4 * [10.sup.-5] S [cm.sup.-1] at 8.0 wt% MWCNTs. Both the thermal and electrical conductivities showed percolation behavior with the percolation thresholds at 6 and 5 wt%, respectively. The MWCNTs synthesized by microwave method gave a good power economy in comparison to MWCNTs obtained by chemical vapor deposition (CVD) on NiMg catalyst. Microwave-synthesized MWCNTs showed high stability at a potential of 250 V in an electrical resistance heater application due to the presence of Fe on the surface of MWCNTs. The developed heater can effectively operate at 220 V, which enables the use of the tubes in household appliances, such as heat fans, irons, and washing machines. Highlights * Synthesis of MWCNTs by microwave plasma treatment of ferrocene and graphite. * Characterization of MWCNTs by different techniques. * Concentration dependence of electro- and thermal conductivity of MWCNTs in elastomers. * Electro-physical parameters studies of elastomers modified with MWCNTs. * Heat generation studies in elastomeric matrix with MWCNTs. KEYWORDS ferrocene and graphite, heat dissipation, heaters, MWCNTs, thermal and electrical conductivities, 1 | INTRODUCTION The use of carbon nanotubes is very important in the production of functional materials. (1-3) The developed materials are being used in various applications including biomedicine, (4) [...]

In this work, expandable graphite (EG) was introduced to the composite of polypropylene/magnesium hydroxide (PP/MH) by melt compounding, fire performance, thermal degradation behavior, and acid resistance of the PP/MH/EG composites were investigated. The results demonstrate that the flame retardant efficiency of MH is very low by itself and there is a noticeable synergism between MH and EG in PP. The addition of proper EG can enhance flame retardancy, smoke suppression, and acid resistance of the PP/MH composite significantly at the same time. Replacing 8.7 wt% MH with 8.7 wt% EG reduces the filling grade needed for V-0 from 63 wt% MH to 56.5 wt% MH/EG mixture. The presence of EG on the composite surface hinders acid erosion of MH. There is no chemical reaction between MH and EG. Continuous intumescent char can be produced on the composite surface upon combustion, which is responsible for the much-improved flame retardancy and smoke suppression, regardless of the presence of MH on the surface area. KEYWORDS acid resistance, expandable graphite, flame retardancy, magnesium hydroxide, polypropylene, smoke suppression, 1 | INTRODUCTION As one of the most important thermoplastic polymers, polypropylene (PP) is widely used in many fields, such as plastics pipes, packaging, building materials, household appliances, and the [...]

A new Al.sup.3+ carbon paste ion selective electrode based on N,N'-bis(salicylidene)-1,3-propanediamine (SB-Salpr) was prepared for the quantification of trace Aluminum. The proposed sensor has significant selectivity and sensitivity toward Al.sup.3+ ions in the presence of a wide range of cations including alkaline, alkaline earth, intermediate and heavy metal ions. The use of multi-walled carbon nanotubes (MWCNTs) and nanosilica in the composition of carbon paste sensors caused improvements in their characteristics; these materials have suitable conductivity and can help in conducting signals through the carbon paste sensors. The electrode consisted of 3% of MWCNTs, 0.5% of nanosilica, 25% of paraffin oil, 66.5% of graphite powder and 5% of SB-Salpr ligand. The sensor shows a Nernstian response to Al.sup.3+ ions with a Nernstian gradient of 20.2 ± 0.1 in the concentration range of 1.0 x 10.sup.-6 to 1.0 x 10.sup.-2 M with the detection limit of 2.1 x 10.sup.-7 M. The sensor response is independent of pH in the range of 24 and possesses the advantages of fast response time less than 5 s. According to the obtained results, Al.sup.3+ nanocomposite carbon paste sensor exhibited good selectivity in the presence of a few metal ions. The sensor was effectively used as an indicator electrode in the potentiometric titration of Al.sup.3+ ions with ethylenediaminetetraacetic acid., Author(s): Razieh Sanavi Khoshnood [sup.1], Setareh Akbari [sup.1], Toktam Mashayekhi Chenarbou [sup.2] Author Affiliations: (1) grid.411768.d, 0000 0004 1756 1744, Department of Chemistry, Mashhad Branch, Islamic Azad University, , Mashhad, [...]

Emission spectrometry with an argon arc source, ensuring the significant suppression of interferences with the molecular spectrum of CN, is used for the rapid direct determination of sulfur in pure graphite powders. A method of the time selection of the analytical signal of sulfur at the line 921.286 nm is proposed (signal registration within a certain interval of 9.8 s). The limit of detection for sulfur is 5 x 10.sup.-4 wt %. The analytical range is 5 x 10.sup.-4-2 x 10.sup.-2 wt % and can be expanded to 1 wt %. The time of a single analysis (3 replicate measurements) is 10 min. The work was performed on an MS-300 compact spectrometer, efficient in the range 908-930 nm, with an S13496 diode array photodetector., Author(s): D. O. Antonov [sup.1], E. G. Silkis [sup.2], B. K. Zuev [sup.1] Author Affiliations: (1) grid.439081.7, 0000 0004 0380 8849, Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy [...]

We present a non-covalent compatibilization approach to prepare polypropylene (PP) composites containing expanded graphite (EG) and graphene nanoplatelets (GNPs) by melt compounding. This method involves PP matrix functionalization with pyridine (Py) moieties, which are capable of engaging in [pi]-[pi] interactions with the surface of the EG and GNPs. The addition of 10 wt% of PP grafted with amino-pyridine (PP-g-Py) to neat PP facilitated the break-up of EG particles, by intercalating between their layers and facilitating their separation into smaller tactoids. GNPs were prepared starting from EG through a thermomechanical exfoliation method. Addition of GNPs to PP resulted in well-dispersed platelets having aspect ratios as high as 40, whereas in the presence of the PP-g-Py compatibilizer the matrix contained sub-micron scale platelets. The electrical percolation thresholds were in the vicinity of 6 and 10 vol% in the compatibilized PPEG and PP-GNP composites, respectively, and the maximum value of the electrical conductivity achieved was [10.sup.-1] S/m for the compatibilized GNP composites. Addition of GNPs resulted in increases in the flexural moduli by as much as 95% compared to the unfilled PP, whereas the impact strength remained unaffected up to 10 wt% GNP content. KEYWORDS conducting polymers, functionalization of polymers, polypropylene), microstructure, nanocomposites, 1 | INTRODUCTION Polypropylene (PP) is used in a wide variety of applications ranging from packaging and textiles to light-weight automotive parts. [1] Recently, there has been growing demand for [...]

Raman spectroscopy is a versatile tool to identify and characterize the chemical and physical properties of graphene-based materials (1-4), providing information on graphene structures for fundamental research and for practical device fabrication, as well as demonstrating the first-and second-order modes in intrinsic graphene, as well as the shear, layer-breathing, and the G and 2D modes of multilayer graphene. Professor Ping-Heng Tan from the State Key Laboratory of Superlattices and Microstructures at the Institute of Semiconductors at the Chinese Academy of Sciences is carrying out new research to advance the use of Raman analysis of these materials. We recently interviewed Tan about this work., You have described Raman techniques to determine the number of graphene layers, to probe resonance Raman spectra of monolayer and multilayer graphenes, and to obtain Raman images of graphene-based materials. [...]

In this study, three different sizes of tripolyphosphate-modified expandable graphite (EGP) are prepared and incorporated into rigid polyurethane foam (RPUF) in order to obtain a flame retardant material with low density, good mechanical properties, and hydrophobicity. The influence of particle size on material combustibility, thermal stability, compression strength, pore cell structure, diathermancy, and hydrophobic property is investigated. Synergistic effect between the EGP and ammonium polyphosphate (APP II) is also examined. Results show the limiting oxygen index value and residue yield increase as the EGP size increases. On the contrary, the heat release rate and total heat release decrease as the EGP size increases. In addition, the chemical char formation effect of APP on RPUF is more important than the char formation of the graphite intercalation compounds. EGP and APP show synergistic effect in improving flame retardancy, thermal stability, and hydrophobicity., INTRODUCTION In order to prevent burning and delay fire spread, flame retardants (FRs) are commonly used in polymers [1-6]. The graphite intercalation compound (GIC), namely expandable graphite (EG), is known [...]

A new voltammetric approach was developed for the determination of paracetamol in tablet and syrup samples using chemometric optimization. The method is based on the use of the gold nanoparticles-polyaniline (AuNPs-PA) modified pencil graphite electrode (PGE). Electrode system was fabricated by using the electrochemical reduction of gold on aniline modified pencil electrode to give gold nanoparticles. A 3.sup.3 full factorial design was used to find optimal oxidation conditions of paracetamol on the AuNPs-PA-PGE. The optimal oxidation conditions of drug substance were found as -524 mV for the accumulation potential, 295 s for the accumulation time and pH 8.69 (for the phosphate buffer solution, 0.1 M). The determination of paracetamol was linear in the range of 2.0 x 10.sup.-7-6.0 x 10.sup.-6 M with a detection limit of 5 x 10.sup.-8 M. As a result, the proposed voltammetric approach gave satisfactory results for the determination of the related drug substance in tablets and syrup., Author(s): Remziye Güzel [sup.1], Haslet Eksi [sup.2], Erdal Dinç [sup.3], Ali Osman Solak [sup.4] Author Affiliations: (Aff1) 0000 0001 1456 5625, grid.411690.b, Dicle University, Faculty of Education, Department of Chemistry, [...]

A titanium dioxide modified expendable graphite ([EG.sub.T]) was prepared and characterized. The synergistic effect between [EG.sub.T] and ammonium polyphosphate (APP) on the combustion characteristics and thermal stability of rigid Polyurethane foam (RPUF) were investigated through limiting oxygen index (LOI), vertical-combustion, microscale combustion calorimeter tests, and thermogravimetric/differential thermal gravimetric (TG/DTG) analysis. Results showed that [EG.sub.T] modified RPUF presented better thermal stability and flame retardancy than the normal expandable graphite (EG) modified RPUF. Addition of [EG.sub.T] improved the LOI value of 80RPUF/20[EG.sub.T] from 19.0% to 26.9%. Furthermore, the combination of [EG.sub.T] and APP caused the 80RPUF/10APP/10[EG.sub.T] to exhibit a LOI value of 27.8%, a vertical burning level of V-0 and a total heat release of 16.5 kJ [g.sup.-1]. The research gave a body of evidence for synergistic performance between [EG.sub.T] and APP, and the effect of condensed phase mechanism was believed to be the main reason for such synergistic effect. POLYM. ENG. SCI., 58:2008-2018, 2018., INTRODUCTIONRigid polyurethane foam (RPUF) is extensively used as structural and insulating material and space filling material due to its excellent properties such as low thermal conductivity, high compressive strength, low [...]

The present study explores the potential use of graphene nanoplatelets (GL-GNPs), synthesized from glucose through a new chemical approach that is facile, economical, and eco-friendly alternative to the conventional Hummer's method, as a nanoreinforcement in polymers for the production of lightweight structural polymer nanocomposites. Understanding the interface character of GL-GNPs/Polyamide 12 (PA12) nanocomposites with various nanofiller loadings and how this affects their tensile behavior, are focal points of interest. Results reveal that enhancements in polymer stiffness and strength are superior at low GL-GNPs content than higher contents. This is attributed to higher degree of GL-GNPs exfoliation and increased polymer phase crystallinity. Interestingly, abundant small/imperfect PA12 crystallites have grown on the GL-GNPs surface, strongly interlinking thus the polymer and graphene phases within nanocomposites. The intensity of such crystallites in interface region is the determinant of the nanocomposites' Young's modulus, assessed at small applied tensile stress. While the GL-GNPs-PA12 interfacial bonding is the determinant of yield and ultimate strengths, estimated at medium and high stress levels. Overall, the 1 wt% GL-GNPs/PA12 nanocomposite is considered the optimum. Its low density and good mechanical performance among the previously developed graphene/Polyamide nanocomposites, propose promising future for GL-GNPs-based nanocomposites as ecofriendly and cost-effective lightweight structural material., INTRODUCTION Polymer nanocomposites (PNCs) are defined as polymeric-based materials filled with inclusions, having at least one dimension less than 100 nm. In contrast to the micro-scale fillers, incorporation of nanofillers [...]

Abstract: A flexible, lightweight, and high conductivity current collector is the key element that enables fabrication of a high-performance, flexible lithium-ion battery. Here, we report a thin, lightweight, and flexible [...]

A low-cost and simply fabricated amperometric glucose biosensor based on glucose oxidase (GOx) and 1,10-phenanthroline-5,6-dione (PD) modified graphite rod electrode was developed. The electrode exhibited good electrocatalytic activity with a well-defined hyperbolic dependence of amperometric signal upon glucose concentration in the presence and in the absence of oxygen. The electrode showed a good reproducibility and repeatability with relative standard deviation of less than 3 and 5%, respectively. The interaction of GOx with PD mediator was confirmed by means of UV-'Vis absorbance spectroscopy. Keywords: phenanthroline derivative, 1,10-phenanthroline-5,6-dione, glucose oxidase, glucose biosensor, amperometric sensors, electrocatalytic activity DOI: 10.1134/S1061934816010044, The development of biosensors is one of the most important directions in bioanalytical chemistry, because biosensors could be successfully applied for the determination of some toxic compounds [1] and biologically [...]

Expanded graphite (EG) was added to polylactic acid (PLA) and then fully mixed in a novel elongational mixing device (RMX) to obtain PLA/EG nanocomposites. The operation of the new mixer device is based on the induced multiple passages of material (by means of reciprocating pistons) at different flow speeds through a short capillary die, thus creating convergent/divergent elongational flows. Highly homogeneous materials were obtained at all mixing conditions and particle size ranged from hundred to several hundreds of nanometers. Also, X-ray diffractograms showed different intensity of the characteristic peak of EG (3% wt/ wt EG was kept constant), suggesting partial exfoliation. Furthermore, the molecular weight of processed neat PLA samples was assessed in order to correlate the PLA degradation to morphology and reinforcement mechanisms in the nanocomposites, as a function of the RMX parameters. As well, final flow properties of neat PLA and EG compounds were obtained by dynamic rheology. Thermomechanical degradation of PLA was found to play a major role in the rheology of mixing. On the other hand, PLA nanocomposites presented a storage modulus between 20 and 40% higher than neat PLA. Finally, morphology comparison between the RMX and an internal mixer, at the same mixing energy input, demonstrated a higher dispersive mixing efficiency for the RMX., INTRODUCTION Polymer/Graphite Nanocomposites With the advent of graphene in the last decade [1], research on polymer/graphite nanocomposites has been gaining relevance since graphite is a natural source of this revolutionary [...]

The potentials of using a graphite matrix for laser desorption/ionization from a thin-layer chromatography (TLC) spot is studied. Using a series of pharmaceutical substances with various functional groups and synthetic N-heterocyclic compounds, it was shown that the simple application of graphite onto TLC spots (outlining contour of the spots and shading the spots with a pencil lead) ensured the efficient desorption/ionization of analytes. In most of cases, the recorded mass spectra revealed only [[M + Na].sup.+] and [[M + K].sup.+] ion peaks, doublets of which can be used to determine molecular masses. The appearance of [[M + H].sup.+] ion peaks in some mass spectra may be due to the presence of mineral acids in the samples. The described approach to the application of the 'matrix' onto analyte spots eliminates the danger of spot blurring by a solution or an organic matrix, simplifies the procedure, and shortens the time of sample preparation. Keywords: graphite-assisted laser desorption/ionization, GALDI mass spectrometry, thin-layer chromatography, graphite, pharmaceutical substances, N-heterocyclic compounds DOI: 10.1134/S1061934814140032, INTRODUCTION Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) most often includes the use of various organic matrices. At the same time, the so called matrix-free versions, based on the activation of [...]

Cyclic and direct voltammetry with linear potential sweep has been used for the investigation of the dependence of the reversibility and reduction current in the system [Fe(CN).sup.3-.sub.6]/[Fe(CN).sup.4-.sub.6] on the concentrations of LiCl, NaCl, KCl, and CsCl solutions. The electrode was made of a graphite-epoxy composite and activated by mechanically cutting a surface layer directly in the solution and deactivated by the long-term storage in the air. The selected type of the graphite electrode and the method used to activate its surface provides the reversibility and diffusion control of the electrode process in the system [Fe(CN).sup.3-.sub.6]/ [Fe(CN).sup.4-.sub.6] regardless of the composition of the supporting solution. In the case of the deactivated electrode, the degree of irreversibility of this process depends on the form and concentration of metal chloride in the supporting electrolyte and the diffusion transfer is complicated by the adsorption of compounds formed between the ferricyanide and the cation of the supporting solution. Keywords: voltammetry, graphite electrode, ferricyanides DOI: 10.1134/S1061934811050091, One of the conditions of the successful development of chemistry, chemical technology, and methods of environment protection from pollution is the improvement of methods of analytical control. Among the great [...]

We examined the analysis of nucleotides and nucleotide sugars by chromatography on porous graphitic carbon with mass spectrometric detection, a method that evades contamination of the MS instrument with ion pairing reagent. At first, adenosine triphosphate (ATP) and other triphosphate nucleotides exhibited very poor chromatographic behavior on new columns and could hardly be eluted from columns previously cleaned with trifluoroacetic acid. Satisfactory performance of both new and older columns could, however, be achieved by treatment with reducing agent and, unexpectedly, hydrochloric acid. Over 40 nucleotides could be detected in cell extracts including many isobaric compounds such as ATP, deoxyguanosine diphosphate (dGTP), and phospho-adenosine5'-phosphosulfate or 3',5'-cyclic adenosine 5'-monophosphate (AMP) and its much more abundant isomer 2',3'cylic AMP. A fast sample preparation procedure based on solid-phase extraction on carbon allowed detection of very short-lived analytes such as cytidine 5'-monophosphate (CMP)-2-keto-deoxy-octulosonic acid. In animal cells and plant tissues, about 35 nucleodde sugars were detected, among them rarely considered metabolites such as uridine 5'-diphosphate (UDp)-L-arabinopyranose, UDPL-arabinofuranose, guanosine 5'-diphosphate (GDP)-L-galactefuranose, UDP-L-rhamnose, and adenosine diphosphate (ADP)-sugars. Surprisingly, UDP-arabinopyranose was also found in Chinese hamster ovary (CHO) cells. Due to the unique structural selectivity of graphitic carbon, the method described herein distinguishes more nucleotides and nucleotide sugars than previously reported approaches. 10.1021/ac101975k

The addition of latent heat storage systems in solar thermal applications has several benefits including volume reduction in storage tanks and maintaining the temperature range of the thermal storage. A phase change material (PCM) provides high energy storage density at a constant temperature corresponding to its phase transition temperature. In this paper, a high temperature PCM (melting temperature of 80[degrees]C) made of a composite of paraffin and graphite was tested to determine its thermal properties. Tests were conducted with a differential scanning calorimeter and allowed the determination of the melting and solidification characteristics, latent heat, specific heat at melting and solidification, and thermal conductivity of the composite. The results of the study showed an increase in thermal conductivity by a factor of 4 when the mass fraction of the graphite in the composite was increased to 16.5%. The specific heat of the composite PCM (CPCM) decreased as the thermal conductivity increased, while the latent heat remained the same as the PCM component. In addition, the phase transition temperature was not influenced by the addition of expanded graphite. To explore the feasibility of the CPCM for practical applications, a numerical solution of the phase change transition of a small cylinder was derived. Finally, a numerical simulation and the experimental results for a known volume of CPCM indicated a reduction in solidification time by a factor of 6. The numerical analysis was further explored to indicate the optimum operating Biot number for maximum efficiency of the composite PCM thermal energy storage. [DOI: 10.1115/1.4001473]

Catalytic graphitization for [sup.14]C-accelerator mass spectrometry ([sup.14]C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500[degrees]C, 3 h) produced the AIMS target of graphite-coated iron powder (GCIP), a mix of non-graphitic carbon and [Fe.sub.3]C. Crystallinity of the AMS targets of GCIP (nongraphitic carbon) was increased to turbostratic carbon by raising the C/Fe ratio from 1:5 to 1 : 1 and the graphitization temperature from 500 to 585[degrees]C. The AMS target of GCIP containing turbostratic carbon had a large isotopic fractionation and a low AMS ion current. The AMS target of GCIP containing turbostrdtic carbon also yielded less accurate/ precise [sup.14]C-AMS measurements because of the lower graphitization yield and lower thermal conductivity that were caused by the higher C/Fe ratio of 1 : 1. On the other hand, the AMS target of GCIP containing non-graphitic carbon had higher graphitization yield and better thermal conductivity over the AMS target of GCIP containing turbostratic carbon due to optimal surface area provided by the iron powder. Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental[sup.14]C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals. 10.1021/ac9020769

Here we report a graphene oxide amplified electrogenerated chemiluminescence (ECL) of quantum dots (QDs) platform and its efficient selective sensing for antioxidants. Graphene oxide facilitated the CdTe [QDs.sup.**+] production and triggered [O.sub.2.sup.**-] generation. Then, a high yield of CdTe QDs* was formed due to the combination of CdTe [QDs.sup.**+] and [O.sub.2.sup.**-], leading to an ~5-fold ECL amplification. Glutathione is the most abundant cellular thiol-containing peptide, but its selective sensing is an intractable issue in analytical and biochemical communities because its detection is interfered with by some thiol-containing compounds. This platform showed a detection limit of 8.3 [micro]M (S/N = 3) for glutathione and a selective detection linear dependence from 24 to 214 [micro]M in the presence of 120 [micro]M cysteine and glutathione disulfide. This platform was also successfully used for real sample (eye drug containing glutathione) detection without any pretreatment with a wide linear range from 0.04 to 0.29 [micro]g [mL.sup.-1]. 10.1021/ac901935a

New thermal storage composites made of graphite and PCM (NaN[O.sub.3]/ KN[O.sub.3] eutectic) have been developed for solar thermal power plants using direct solar steam generation. Those materials, obtained using different elaboration routes (compounding, infiltration, cold compression) and graphite types, are presented with their respective properties (enhanced thermal conductivities, thermal storage capacities, stability) and compared together. Both the laboratory and industrial scales and grades are considered and compared. The infiltration route has been found to be inefficient before the two other ones. Compound composites present isotropic properties and thermal conductivity intensification in the medium range (a factor of 10 for 7 wt % in graphite). Cold compressed composites present highly anisotropic properties and strong intensification in thermal conductivity (a factor of 31 at 200[degrees]C for 20 wt % in graphite). Their melting and solidification temperatures as well as their intrinsic storage capacity are close to the pure salt ones. [DOI: 10.1115/1.2804620] Keywords: latent heat storage, phase change materials, graphite, solar thermal electric plant

In this study, the flammability characterization and synergistic effects of different particle size of expandable graphite (EG) with modified magnesium hydroxide (MH) in flame-retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL-94 test, ther-mogravimetric analysis (TGA), and fourier transform infrared (FTIR) spectroscopy. The results showed that the particle size of EG had a great effect on the flammability of the PP/MH/EG composites. The EG2 with smaller particle size could apparently increase the LOI value and improved the UL-94 flammability properties rating of the PP composites. The data obtained from the TGA and FTIR curves indicated that the thermo-oxidative stability of PP/MH/EG composites increased with decreasing particle size of EG. And the smaller the particle size of EG, the higher the residues of the composite. POLYM. ENG. SCI., 47:1756-1760, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION Traditionally, halogen containing compounds, alone or in conjunction with antimony trioxide, are the main flame retardants (FR) of polyolefins (PO). There is an increasingly restriction about the use of [...]

Due to a high background in the low-mass region, conventional MALDI is not as useful for detecting small molecules (molecular masses < 500 Da) as it is for large ones. Also, spatial inhomogeneity that is inherent to crystalline matrixes can degrade resolution in imaging mass spectrometry (IMS). In this study, colloidal graphite was investigated as an alternative matrix for laser desorption/ionization (GALDI) in IMS. We demonstrate its advantages over conventional MALDI in the detection of small molecules such as organic acids, flavonoids, and oligosaccharides. GALDI provides good sensitivity for such small molecules. The detection limit of fatty acids and flavonoids in the negative-ion mode are in the low-femtomole range. Molecules were detected directly and identified by comparing the MS and MS/MS spectra with those of standards. Various fruits were chosen to evaluate the practical utility of GALDI since many types of small molecules are present in them. Distribution of these small molecules in the fruit was investigated by using IMS and IMS/MS.

A new on-column derivatization method based on the redox activity of porous graphitic carbon (PGC) packing materials was presented for enhancement of separation selectivity of HPLC. Two PGC packing materials were used as the solid redox agents as well as the stationary phase, and their redox activities were investigated using trans-1,2-diaminocyclohexanetetraacetate (DCTA) complexes of some metal ions as probe compounds. It was found that the redox property of PGC was modified by treating them with a solution containing a reducing agent, sodium sulfite or hydroxylammonium chloride. The original PGC packings oxidized Co(II)-DCTA to Co(III)-DCTA during elution, while the PGC treated with a reducing agent showed reduction activity converting Co(III)-DCTA to Co(II)-DCTA. These two cobalt complexes do not form their individual chromatographic zones but migrate as a single zone of their mixture on the PGC column contrary to the chromatographic behavior on a [C.sub.18] bonded silica, on which Co(II)-DCTA and Co(III)-DCTA can be separated. Treatment of the PGC column with a reducing agent solution transforms the oxidative activity of the original PGC packing to a reductive one from the upper part of the column, so that the retention time of the cobalt complex can be controlled by changing the volume of the reducing agent solution to be used for treatment of the PGC column. The selective separation and determination of cobalt in a reference manganese nodule sample by the developed method was demonstrated.

Poly(methyl methacrylate) (PMMA)/expanded graphite composite has been made via an in situ polymerization of methyl methacrylate(MMA) in the presence of expanded graphite obtained by rapid heating of the graphite intercalation compound (GIC). The composite was then blended with poly(vinyl chloride) (PVC) to form an electrically conducting composite. SEM, TEM and XRD showed that the graphite had been dispersed throughout the polymer matrix in the form of nanosheets with thicknesses of about 20 nm. The resulting composite showed excellent electrical conductivity despite a low concentration of graphite. The transition from an electrical insulator to an electrical semiconductor for the composite occurred when the graphite content was 3.5 wt%, much lower than that of conventional conducting polymer composites. Conductivity reached a maximum of [10.sup.-4] s/cm at a graphite concentration of 5.0 wt%. This improvement of conductivity could be attributed to the high aspect ratio (width-to-thickness) of the graphite na nosheets dispersed in the polymer matrix., INTRODUCTION Graphite, which is naturally abundant, has been widely used as a conducting filler in preparing conducting polymer composites (1, 2). Conventional graphite fillers are usually micro-diameter powders. In order [...]

The insertion of platinum tetrachloride molecules into graphite layers, their reduction behavior, and the formation of platinum metal nanosheets containing hexagonal holes are studied. The sheets had a number of hexagonal holes and edge angles of 120 degree, owing to the limited aggregation of the intercalated platinum chloride molecules to platinum sheets along regular hexagonal nets of carbon atoms between graphite layers.

A new type of electrochemically driven actuator is described. This actuator uses graphitic carbon as the electroactive material (as opposed to the polymeric films used in previous devices of this type), and it is the first example of an actuator based on a nanostructured material. The actuator consists of branched carbon nanotubules embedded within the pores of a microporous alumina template membrane. Electrochemical [Li.sup.+] intercalation causes this nanotubule-containing membrane to flex, and electrochemical deintercalation causes the membrane to relax to its original position. The characteristics of this new actuator are described here.

A modern electrothermal atomic absorption spectrometer with transversely heated graphite tube and a solid sampling system based on the boat technique was used for the development of a method for the direct determination of Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn in high-purity tungsten powders. The high background originating from tungsten oxide was eliminated by using hydrogen as purge gas during pyrolysis. Quantification of all elements could be performed by using calibration curves measured with aqueous standard solutions. The analyte contents determined were between 0.02 (Zn) and 34.9 (Fe) [[micro]gram]/g. The results were in good agreement with those obtained in analysis of sample digests, and they were compared also with results provided by other methods in other laboratories. Owing to an almost complete freedom of blank and unusually high sample amounts applied (5-100 [[micro]gram]), extremely low limits of detection, in the range between 0.01 (Mg) and 4 (Fe) ng/g, could be achieved.

The analyses of both O and N isotopic compositions of nitrate have many potential applications in studies of nitrate sources and reactions in hydrology, oceanography, and atmospheric chemistry, but simple and precise methods for these analyses have yet to be developed. Testing of a new method involving reaction of potassium nitrate with catalyzed graphite (C + Pd + Au) at 520 [degrees] C resulted in quantitative recovery of N and O from nitrate as free C[O.sub.2], [K.sub.2]C[O.sub.3], and [N.sub.2]. The [[Delta].sup.18]O values of nitrate reference materials were obtained by analyzing both the C[O.sub.2] and [K.sub.2]C[O.sub.3] from catalyzed graphite combustion. Provisional values of [[Delta].sup.18][O.sub.VSMOW] for the internationally distributed KN[O.sub.3] reference materials IAEA-N3 and USGS-32 were both equal to +22.7 [+ or -] 0.5[per thousand]. Because the fraction of free C[O.sub.2] and the isotopic fractionation factor between C[O.sub.2] and [K.sub.2]C[O.sub.3] were constant in the combustion products, the [[Delta].sup.18]O value of KN[O.sub.3] could be calculated from measurements of the [[Delta].sup.18]O of free C[O.sub.2]. Thus, [[Delta].sup.18][O.sub.KN[O.sub.3]] = a[[Delta].sup.18][O.sub.free C[O.sub.2]] - b, where a and b were equal to 0.9967 and 3.3, respectively, for the specific conditions of the experiments. The catalyzed graphite combustion method can be used to determine [[Delta].sup.18]O of KN[O.sub.3] from measurements of [[Delta].sup.18]O of free C[O.sub.2] with reproducibility on the order of [+ or -]0.2[per thousand] or better if local reference materials are prepared and analyzed with the samples. Reproducibility of [[Delta].sup.15]N was [+ or -]0.1[per thousand] after trace amounts of CO were removed.

Details of an artificially synthesized dry phantom material developed for the experimental studies of microwave exposure to the human body are shown. The material is solid and can simulate electrical characteristics of high water content biological tissues such as muscles and the brain. The material is composed of high-[[Epsilon].sub.r] ceramic powder, graphite powder, and bonding resin. Any shape of phantom models can be constructed to simulate different parts of the body, as well as the head. The paper reports the synthesis technique to obtain the desired complex permittivity and the fabrication technique of the phantom models for usage of specific absorption rate (SAR) estimation at 900 MHz. Index Terms - Bonding resin, ceramic powder, dry phantom, graphite powder, material, microwave exposure, specific absorption rate.

Raman spectra of normally fluorescent materials were obtained by quenching the fluorescence through adsorption on carbon surfaces. Energy transfer from the excited state to the carbon surface greatly reduced the fluorescence of rhodamine 6G and the near-IR laser dye IR125, and Raman spectra with high S/N were obtained from the adsorbed molecules. Strong resonance enhancement of Raman scattering was observed, and monolayer films of RGG were observed. RGG exhibited Langmuirian adsorption behavior, with saturation coverage occuring at [approximately] 0.5 mM in methanol. The technique was also successfully applied to bis(methylstyryl)benzene (BMB) and fluoranthene, which are less fluorescent but also much weaker scatterers. Since the laser wavelengths yielding resonance enhancement are in the same range as those producing fluorescence, adsorption to carbon permits elimination of fluorescence without loss of resonance enhancement. The porous graphite substrate has the added advantage of high microscopic surface area, low elastic background, and propensity to adsorb a wide range of organic materials. With care, it was possible to observe Raman features from monolayers of materials having cross sections comparable to that of benzene, such as the 1205 [cm.sup.-1] peak of BMB.

Novel carbon film optically transparent electrodes are prepared by the deposition of thin carbon films on the surface of metal mesh substrates. Deposition occurs either through spray coating colloidal graphite on the metal mesh or through pyrolysis of acetone on a resistively heated metal mesh. Pyrolytic graphite-coated electrodes are preferred with their high optical transparencies and low electrical resistances, as well as greater potential windows for the metal mesh electrodes.

The temperature-c0 calibration of D.M. Shengelia, R.A. Akhvlediani and D.N. Ketskhoveli was tested to geologically examine the dependability of the X-ray diffraction (XRD)-derived c0 parameter in functioning as a geothermometer. The possible application of the changes in the c0 parameter of graphite with temperature for geothermometric measurements were explored. For qualitative measurement, graphite thermometry can be applied only to low-grade metamorphic rocks, because besides temperature, other factors influence the c0 parameter of graphite. For temperatures more than 500 degree centigrade, graphite thermometry is a useful technique.

Oxidation of the first fractional carbon monolayer on highly oriented pyrolytic graphite (HOPG) electrodes is topographically manifested by the formation of well-defined surface blisters consisting of a solid skin covering a hollow interior. Atomic force microscopy (AFM), optical microscopy (OM), and scanning electron microscopy (SEM) show that the surface blisters formed by application of potentials from +1.5 to +1.63 V vs SSCE in 1.0 m [KNO.sub.3] are from 20 to 1000 nm high and from 0.5 to 50 [micro]m at the base. Surface analyses by AFM, X-ray microprobe, and Auger electron spectroscopy indicate that the outermost layer of the blister skin is essentially intact HOPG lattice (at the atomic scale) while the interior of the blister top contains a layer of graphite oxide (EGO). We propose that, following intercalation of electrolyte and water into the HOPG, blisters form as a result of electrolytic gas evolution at subsurface active sites (e.g., crystallite grain boundaries) with accompanying parallel electrolytic formation of EGO. The HOPG electrode kinetics of the Fe-[[(CN).sub.6].sup.3-/4-] couple are only slightly enhanced by oxidation at +1.62 V, relative to the large changes in k[degrees] caused by oxidation at +1.99 V, consistent with AFM images that show modest overall changes in the HOPG surface lattice in the former case and extensive lattice damage with exposure of edge plane sites in the latter case., The topographical manifestations of the oxidation of the first fractional carbon monolayer of basal plane highly oriented pyrolytic graphite electrode surfaces was analyzed. The formation of well-defined blisters in the electrode was characterized by atomic force, optical, scanning electron Auger electron microscopies and surface and energy-dispersive x-ray microanalyses. Results indicate that these blisters were formed due to electrolytic gas evolution at the subsurface active sites.

Energy-dispersive X-ray fluorescence (ED-XRF) was used to determine sulfur in graphite. Because of interferences and abnormal scattering of the excitation radiation (diffraction effects), spectrum evaluation using least squares fitting failed. The partial least squares (PLS) method on the other hand is able to predict the S concentrations with an accuracy better than 5% in the concentration range of 2-60%. The various artifacts observed in the spectra can be explained with the PLS model., The quantification of sulfur in a graphite matrix by partial least squares (PLS) was investigated. Experiments involved the utilization of energy- dispersive x-ray fluorescence. PLS spectrum evaluation was compared to least squares fitting (LSF). It was found that PLS estimations were more accurate the LSF, were able to reduce human interaction requirements to nil and exhibited potential for quality control spectrometry applications.

A surface model for rough pyrolytic graphite (RPG) and glassy carbon (GC) electrodes has been developed in ionic surfactant media. Ionic surfactant aggregates enable the control and optimization of response of these graphite electrodes. The feasibility of forming surfactant aggregates directly from solution is demonstrated. The results indicate head-on surfactant--surface interactions and formation of hemimicelles at the surface. Structural differences between RPG and GC result in differences in aggregation and consequently different effects of surfactants on probe response. Therefore, the nature of the probe along with the surface and surfactant structure must be considered for optimization of response. Furthermore, in surfactant solutions improvements in sensitivity of inactive GC and reproducibility of active RPG are demonstrated., The development in an ionic surfactant media of a surface model for rough pyrolytic graphite and glassy carbon electrodes is discussed. The response of these electrodes was controlled and maximized by ion surfactant aggregates and analyzed by cyclic voltammetry experiments. Results established the occurence of probe response optimization along with the modification of controlled surfaces.

Silver-graphite materials are commonly used as arcing contacts is prevalent in both arcing and sliding applications. One such material, Graphite, has the ability to prevent sticking or welding and stops the formation of insulating compounds which could cause high contact resistance. On the other hand, silver is a very good electrical conductor and does not form stable oxides. The effects of graphite particles on the arc erosion behavior of silver-graphite materials are discussed.

Mount Etna's lava contains all the necessary ingredients for constructing carbon nanotubes. A volcanic eruption fulfills the need of a carbon source, metal particles and high temperatures, which are required for producing carbon nanotubes.

We report the synthesis of tubular graphite cones using a chemical vapor deposition method. The cones have nanometer-sized tips, micrometer-sized roots, and hollow interiors with a diameter ranging from about 2 to several tens of nanometers. The cones are composed of cylindrical graphite sheets; a continuous shortening of the graphite layers from the interior to the exterior makes them cone-shaped. All of the tubular graphite cones have a faceted morphology. The constituent graphite sheets have identical chiralities of a zigzag type across the entire diameter, imparting structural control to tubular-based carbon structures. The tubular graphite cones have potential for use as tips for scanning probe microscopy, but with greater rigidity and easier mounting than currently used carbon nanotubes., Owing to their unique mechanical properties and atomic structures, carbon nanotubes (CNTs) have various potential applications, such as probes for scanning probe microscopy (1-3), field electron-emitting sources (4-6), and tiny [...]

A scanning tunneling microscopy (STM) experiment can be used to teach physical chemistry undergraduate students about surface oxidation kinetics, exploring the kinetics of the oxidation of a carbon surface. The students first do an experiment introducing them to STM and the crystal structure of graphite.

Encapsulation of fine metal particles by graphite would not only provide an oxidation protective layer but also acts as a solid lubricant that enables high speed scanning of magnetic tapes against a writing/recording head. In this paper, we propose a novel method to produce the graphite layer on the surface of magnetic particles. First, the surfactant is adsorbed onto the particle and then reduced/decomposed by bombardment with ionized He atoms in the arc discharge chamber. As a result of this treatment, the magnetite particles are uniformly coated with a graphite layer of a few nanometers thick.

The high-resolution scanning tunneling microscopy (STM) used to study the self-assembly of the DNA base molecule adenine (A) revealed two coexisting distinct (homo- and heterochiral) domain of adenine formed at the liquid/solid interface. The STM findings were validated and confirmed by using ab initio density functional theory (DFT) calculations.

The effects of iron content and initial fractional density of the preforms on deformation behavior are investigated thoroughly by using graphite as a lubricant. It was found that the preforms of higher iron content show higher values of deformation properties like the axial stress and the Poisson's ratio than less/without iron preforms provided that the initial fractional density taken is kept constant.

The use of graphite particles (1-2/[micro]m) as coatings on quartz crystal microbalances (QCMs) for detection and monitoring of toluene and other volatile organic compounds (VOCs) is described. Unlike the more commonly used polymeric coatings with low glass transition temperatures ([T.sub.g]), particulate graphitic coatings are not as susceptible to loss of acoustic energy when coating thickness or operational temperature increases. This situation enables the use of relatively thick coatings, which increases the absolute amount of vapor sorbed in the coating and, consequently, lowers the level of detection and enhances operation over a wide temperature range. The use of small size particles also results in a coating with a more porous structure, which facilitates uptake and release of VOCs in comparison to coatings made from high [T.sub.g] polymers, which have a lower porosity. These attributes, coupled with the inherent stability of graphitic materials, make particulate graphite coatings especially suitable for applications at high temperatures. The advantages of using particulate graphite as a coating on QCMs are demonstrated by comparison to the performance of a few low-[T.sub.g] polymers [i.e., poly(isobutylene) and poly(diphenoxyphosphazene)] and high-[T.sub.g] polymers (i.e., polystyrene).

A measurement system is described for determining the size of a high-current density solid electron beam from a Pierce-type electron gun. The apparatus incorporates ten graphite apertures and two graphite tubes mounted at 30 [degrees] intervals on an off-axis drum that is rotated by a stepper motor. The graphite apertures are used to make localized beam-edge current-interception measurements at ten discrete locations at 1-cm intervals along the length of the beam. The graphite tubes can be used either to produce an integrated edge-current profile over an 11.4-cm length of the beam, or to measure the net current outside of two specific diameters centered on the beam axis. The active aperture or tube and its position with respect to the beam axis are determined by the orientation of the drum, which is read out using an absolute shaft encoder. This permits the position of each aperture or tube to be determined to an accuracy of 60 [micro]m. Index Terms--Electron beam analyzer, magnicon.