Mixture Of Graphite Research Articles

Comparative study of single- and double-layer BaFe12O19-Graphite nanocomposites for electromagnetic wave absorber applications

The development of stealth technology for military applications and increasing concerns of electromagnetic pollution have garnered interest to design microwave absorbing materials with wide absorption bandwidth and effective absorption properties. Two batches of samples as a potential radar absorbing material were prepared in this study: single-layer and double-layer nanocomposite mixtures of graphite and barium hexaferrite nanoparticles. Characterizations of electromagnetic and microwave absorbing properties were carried out in the frequency range of 8−12 GHz (X-band) and 12−18 GHz (Ku-band). Single-layer samples with thickness of 2 mm showed optimal absorption properties with minimum reflection loss of -20.5 dB at 11.8 GHz for X-band and -20.7 dB at 14.7 GHz for Ku-band, displaying bandwidths of 0.6 GHz for the former and 3.8 GHz for the latter at -10 dB. On the other hand, double-layer samples made of 1 mm thick barium hexaferrite matching layer and 2 mm thick graphite absorbing layer showed optimal absorption properties with minimum reflection loss of -30.0 dB at 9.2 GHz for X-band with narrower bandwidth of 0.6 GHz. The microwave absorption properties of these nanocomposites were attributed to combined effect of dielectric loss from graphite and magnetic loss from ferrite.

Intensive Improvement of Cementite Synthesis

Cementite extraordinary mechanical properties have drawn the attention of researchers in recent years. But, the limited methods for the production of this material, led to the production of iron with more than 2.1%wt carbon content beside free carbon by simultaneous thermal-mechanical activation of hematite and graphite mixture at 800°C for 6 hours in the present research. Then, a structure with more than 80%wt cementite was obtained through partial melting process at 1180°C for 25 minutes.

Intensive Improvement of Cementite Synthesis

Cementite extraordinary mechanical properties have drawn the attention of researchers in recent years. But, the limited methods for the production of this material, led to the production of iron with more than 2.1%wt carbon content beside free carbon by simultaneous thermal-mechanical activation of hematite and graphite mixture at 800°C for 6 hours in the present research. Then, a structure with more than 80%wt cementite was obtained through partial melting process at 1180°C for 25 minutes.

Thermal kinetics involved during the solid-state synthesis of Cr2AlC MAX phase

The formation of nanolaminated Cr2AlC MAX phase by using solid-state synthesis route has been investigated through thermal analysis technique. The mixture of chromium (Cr), aluminum (Al) and graphite (C) in 2:1.4:1 was subjected to differential thermal analysis in an argon atmosphere and heated up to 1250 °C, at multiple heating rates (10, 20, 30, 40 °C min−1). Two endothermic peaks (~ 666 °C and ~ 1053 °C) are observed during the synthesis of Cr2AlC MAX phase. The formation of Cr2AlC is also confirmed through XRD, FESEM, HR-TEM and SAED analysis. The kinetic triplets (activation energy, pre-exponential factor and reaction mechanism) involved during the synthesis of Cr2AlC were estimated. The activation energy and reaction mechanism were determined by using iso-conversional model-free methods (KAS, FWO and FR methods) and integral master plot method, respectively. The results indicated that F2 (second-order) reaction mechanism dominates the formation of Cr2AlC MAX phase.

Features of the interfacial zone structure formation during thermal diffusion metallization of diamond by transition metals

The paper studies morphology, chemical, structural and phase composition of the diamond-metal interphase zone, formed in the process of thermal diffusion metallization of diamond with chromium, titanium, iron, nickel and cobalt powders with the same temperature-time mode that corresponds to the sintering of diamond-containing WC-Co-matrices with copper impregnation. In the process of thermal diffusion metallization of chromium and titanium, a metalized coating is formed on the surface of the diamond, consisting of a mixture of carbides, metals and graphite of variable composition phases. The insignificant content of graphite formations and their intermittent nature of the diamond-metal interfacial zone ensure a strong adhesion of the metalized coating to the diamond through the carbides of the corresponding metals. When thermal diffusion metallization of diamond with iron occurs at the diamond-metal interfacial zone, the formation of an intermediate layer strongly adhered to the diamond also takes place. The intermediate layer has a complex structural phase composition comprising a mixture of iron phases, a solid solution of carbon in iron and graphite of variable composition. An intermediate layer on the surface of diamond could be formed by solidification of the liquid phase with the eutectic composition resulting from the eutectic melting of the diamond-iron contact pairs. However, this assumption requires additional research to confirm it, and special experiments using highly sensitive research methods. Under the heating conditions specified in the experiment samples of nickel-diamond and cobaltdiamond cause intense catalytic graphitization of diamond with the formation of numerous traces of erosion on its surface. The observed weak adhesive interaction of these metals with diamond is probably due to the high melting temperatures of the Ni-C and Co-C eutectics, which does not allow the metals to react with diamond under given experimental conditions.

Microstructural Characterization of TiC-White Cast-Iron Composites Fabricated by In Situ Technique.

High-chromium white cast-iron specimens locally reinforced with TiC–metal matrix composites were successfully produced via an in situ technique based on combustion synthesis. Powder mixtures of Ti, Al, and graphite were prepared and compressed to fabricate green powder compacts that were inserted into the mold cavity before the casting. The heat of the molten iron causes the ignition of the combustion reaction of the reactant powders, resulting in the formation of the TiC by self-propagating high-temperature synthesis. The microstructure of the resultant composites and the bonding interfaces was characterized by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural results showed a good adhesion of the composite, suggesting an effective infiltration of the metal into the inserted compact, yet a non-homogeneous distribution of the TiC in the martensite matrix was observed. Based on the results, the in situ synthesis appears to be a great potential technique for industrial applications.

Influence of different carbon materials on electrical properties of epoxy-based composite for bipolar plate applications

During the last years, polymer composite bipolar plates have been developed from appropriate carbon materials and polymers. Considering these materials, several factors influence the effective electrical properties of bipolar plates for polymer electrolyte fuel cell (PEFC) applications. This research focuses on the development of a composite of graphite/epoxy resin/aliphatic amine, which be technically feasible as a material for use in PEFC and meet international commercial standards. A synergic mixture of Expanded Graphite (EG) as a primary filler and different secondary fillers was analyzed. The effect of Carbon Black (CB) and Graphite Nanoplatelets (GNP) as secondary fillers in proportions of 0, 0.5, 1, 2, and 3 wt% on EG with particle size greater than 300 µm and content of 40 wt% are analyzed. The methodology in this composite processing did not include any solvent and relatively low temperature processing is performed. The processing conditions were studied to understand the impact on the electrical properties of the composite. The best results were obtained with carbon black at 1%, obtaining an in-plane electrical conductivity at about 50 S/cm. The appropriate dispersion of the CB through the Epoxy/EG matrix creates bridges connecting plates that improve the flow of electrons compared to GNP composites.

Preparation and Electrochemical Performance of Porous Si/SiOx/G Composite Anode for Lithium Ion Batteries

Silicon/silicon oxides/graphite (Si/SiOx/G) composite with high capacity and excellent cycling performance has been synthesized via high temperature treatment, HF etching and high-energy ball milling for mixture of silicon oxide and graphite. The chemical composition and morphology of the sample was characterized by XRD, SEM and TEM. Large numbers of nanopores were formed in the as-prepared composite, providing three-dimensional transmission pathways for lithium ions and electrons. After 100 cycles, the electrode kept an excellent reversible capacity of 804.2mAh·g-1. The excellent electrochemical properties are mainly attributed to the uniform distribution of silicon particles in amorphous silicon oxide, the buffering effect of porous structure and the improvement of conductivity of the composite by graphite.

IDENTIFICATION OF THE PAINTING MATERIALS OF A UNIQUE EASEL PAINTING BY MAHMOUD SA'ID

The present study aims at examining a unique easel painting by the well-knownEgyptian painter, Mahmoud Sa'id. It was painted over four years and displayed atthe Agricultural Museum in Egypt. It experienced many deterioration phenomena.The study utilized some non-destructive and non-invasive analytical techniques,i.e. MA-XRF, SEM-EDX, ATR-FTIR, and GC-FID in addition to XRD and SM.Due to the case-study painting multilayers technique, the results of MA-XRF andEDX mapping and XRD patterns revealed using Ultramarine (Na,Ca)8 (AlSiO4)6(SO4,S,Cl)2, yellow ochre (Fe2O3.H2O), red ochre (Fe2O3), and a mixture ofgraphite (C) and bone black (C,Ca5(OH)(PO4)3) as a coloring pigments in theblue, yellow, reddish brown and black samples, respectively. Moreover, Barite(BaSO4) and Zincite (ZnO) were used in the ground layer with Hydrocerussite(Pb3(CO3)2(OH)2) and Sphalerite (ZnS) in lightening colors. Linseed oil wasasserted as the pigment binding media, while the binding media of the groundlayer was not confirmed. Furthermore, fragility, brittleness, cleavages, peeling,cracks, macro cracks, stains, and ancient fault restoration were detected in thecase-study painting. Accordingly, it urgently requires treatment.

Carbon nanotubes and carbon fibers in a flash: an easy and convenient preparation of carbon nanostructures using a conventional microwave

The growing interest in nanomaterials in different application fields calls for the implementation of simple, economically appealing, and efficient preparative methods. Among the wide variety of nanomaterials, carbon nanostructures have a special place due to their potential technological applications. Here, we present a fast, cheap, and easy-to-implement microwave-assisted method for the preparation of carbon nanotubes (CNTs) and carbon fibers (CFs) at room pressure conditions. The synthesis involves heating a mixture of graphite and ferrocene contained in a simple glass tube using a conventional microwave oven. A mixture of multi-walled carbon nanotubes (MWCNTs) and Fe3O4 magnetic nanoparticles were obtained quickly (less than 30 s) and in good yields. The products were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Raman spectroscopy.

Pembuatan Recycle Screen Printed Carbon Electrode dan Aplikasinya untuk Deteksi Asam Galat dengan Teknik Voltammetri

Gallic acid is phenolic compound found in tea and act as antiradical agent. This compound is electrochemically active and could be detected using voltammetric technique. This study aims to obtain recycle screen printed carbon electrode (rSPCE) and applied it for voltammetric detection of gallic acid. rSPCE was prepared by modification of used SPCE working electrode using a mixture of graphite:polystyrene at ratio of 95:5, 90:10, and 85:15 (w/w). Graphite:polystyrene was suspended in chloroform and deposited on SPCE by drop casting method. Phosphate buffer 0.1 M at pH of 2.5, 3.5, and 7 were used as electrolyte solution in voltammetric detection of gallic acid. The optimum condition of gallic acid detection was obtained when phosphate buffer 0,1 M at pH of 2.5 and rSPCE in composition of graphite:polystyrene (95:5) used as electrolyte and working electrode, respectively. Gallic acid has 2 oxidation peaks at potential of 0.26 V and 0.63 V vs Ag/AgCl, respectively. At concentration of 1 – 5 mM, gallic acid and oxidation currents provide linear regression with the coefficient determination of 0.9947 and 0.9864, consecutively for peak number 1 and 2. Measurement of gallic acid at rSPCE 95:5 shows good precision with %RSD < 5%. rSPCE was successfully applied for voltammetric detection of gallic acid in standard solution with accuracy > 96%, however further development is needed before its application for gallic acid measurement in real sample such as tea extract.

Synthesis and characterization of the nanostructured solid solution with extended solubility of graphite in nickel by mechanical alloying

In the present work, mechanical alloying of a powder mixture of nickel and graphite (up to 15wt%) was carried out in an attrition mill under a nitrogen atmosphere. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The 15wt% graphite dissolved into the nickel (exceeding the negligible solid solubility in the nickel-carbon system), thereby forming a supersaturated solid solution of graphite in a nickel matrix. The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions. A three-step graphite dissolution mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the crystallite size (62 to 43 nm), lattice strain (0.12% to 0.3%), and lattice parameter (0.3533 to 0.3586 nm), which led to the formation of the supersaturated solid solution, were also evaluated and discussed.

高損失材料(グラファイト混合物)の誘電率と導電率の関係

高損失材料(グラファイト混合物)の誘電率と導電率の関係

Phenolic resin-commercial graphite disk preparation: Effect of the resin amount and the thermal treatment on the structural, morphological and mechanical properties

In this work, macroporous discs were prepared using synthesized phenolic resin (PR) and commercial graphite mixtures (15–40 weight percent). The structure of the PR resin was confirmed by Proton Nuclear Magnetic Resonance and Gas Chromatography Coupled to Mass Spectrometry while the curing temperature was determined by Fourier Transform Infrared Spectroscopy. Also, the surface homogeneity and the structural analysis of the prepared disks were examined by means of scanning electron microscopy and X-ray powder diffraction analysis, respectively. According to the micrographs it was observed that as the PR amount increased disks’ porosity decreased giving rise to homogeneous and smooth surfaces which was explained in terms of the X-ray diffraction analysis that proved that graphite average crystal size (ACS) values decreased progressively with PR amount. Furthermore, it was demonstrated that the mechanical resistance could be tuned with the PR amount and the thermal treatment since as both increased the disks’ hardness augmented.

Saline solution impedance sensor based on Poly Methyl Methacrylate and graphite: preliminary results

This paper shows a preliminary study of behaviour comparison in NaCl and KCl saline solutions of three screen printed bipolar electrodes with a coating mixture of Poly Methyl Methacrylate (PMMA) and graphite. Results indicate greater selectivity of the coating electrodes with partial ring geometry compared with concentric and spiral bipolar, cover mixture allows eliminating electrolyte electrode interface in low frequencies. The benefits of using this electrode are: optimize sample measurements; low-cost manufacturing; integration feasibility into a mobile device. Upcoming research requires including test with other ionic solutions and new doped graphite composes.

One-pot preparation of reduced graphene oxide from liquid nitrogen tetroxide via redox potential control

Reduced graphene oxide (RGO) was prepared by redox method with liquid nitrogen tetroxide (N2O4) as oxidant source and sodium borohydride (NaBH4) as reducing agent, which could provide an effective way for the treatment and reuse of liquid propellant oxidants. After N2O4 was pretreated with 60 wt% hydrogen peroxide (H2O2), fluorocarbon surfactants (FC-4330), a nonionic polymerized yellow viscous liquid that can significantly reduce the surface tension of the solvent at very low concentrations, was added to the mixture of N2O4 and natural graphite. In order to simplify the synthetic route of graphene, we introduced the redox potential (ORP), a comprehensive index to measure the degree of redox of the reaction system, by which we successfully fused the oxidation stage and reduction stage in the same reaction vessel, in other words, the one-pot method for preparation of RGO has been successfully realized. This method can also be used to accumulate graphene products and determine the yields directly without the necessity to purify and deal with numerous intermediate products. Furthermore, the redox potential of the reaction system was continuously optimized and precisely regulated by automatic sample injection to create the best redox atmosphere for the preparation of RGO, so as to achieve the purpose of improving the yield and quality of graphene. Finally, the optimal process conditions for the preparation of RGO by one-pot method were obtained, that is, the optimal initial ORP range was [1700, 1750] mV at the oxidation stage and [−1200, −1180] mV at the reduction stage. The graphene products can eventually be exfoliated easily between layers with uniform fold distribution, more concentrated particle size distribution and smaller microcrystal size, and simultaneously the stacking number of layers can be stabilized at 1 or 2 layers.

Effects of Conductive Phase on Properties of Concrete

In this paper, the effects of graphite and carbon fiber on the properties of concrete were studied, the 28d compressive strength and electrical resistivity of concrete were measured, and the microstructure of concrete was observed. The results show that the graphite could improve the conductivity of concrete meanwhile reduce the compressive strength, and that the carbon fiber can improve the compressive strength of concrete, but its influence is considerably limited. Only when the mixing amount of graphite is higher than 1%, the compressive strength of concrete will increase along with the increase of mixing amount of carbon fiber, and the lamellar structure of graphite will be obvious, and the lamellar connection between graphite flakes will be in good condition. When the mixing amount of carbon fiber is 0.8%, dense connection will be formed between the carbon fiber & graphite and the hydration products. The combined mixture of graphite and carbon fiber can form a dense and relatively complete conductive network and is beneficial to the improvement of compressive strength of concrete.

A novel disposable self-adhesive inked paper device for electrochemical sensing of dopamine and serotonin neurotransmitters and biosensing of glucose

In this work, we detail the progress of a novel electrochemical disposable device, which has a relatively low cost and easy production, with a novel conductive ink, that consists of graphite and automotive varnish mixture, deposited over a self-adhesive paper, granting an easy production with relatively low cost. The electrode surface was characterized by scanning electron microscopy, X-ray powder diffraction and Fourier transforms infrared and Raman, cyclic voltammetry and electrochemical impedance spectroscopies. In addition, the proposed electrode was applied for individual electrochemical determination of dopamine and serotonin. The device achieved a linear response between 30 and 800 μmol L−1 and a limit of detection (LOD) of 0.13 μmol L−1, by square wave voltammetry for dopamine and a linear range from 6.0 to 100 μmol L−1, with a LOD of 0.39 μmol L−1, by differential pulse voltammetry for serotonin. Later, the working electrode was modified with glucose oxidase and dihexadecyl phosphate film in order to obtain a biosensor. At this stage, CV was applied to detect glucose in the range of 1.0–10 μmol L−1 and LOD of 0.21 μmol L−1. By three different techniques and analytes, the sensoring and biosensoring processes presented high reproducibility. The proposed adhesive electrode is easy to prepare, disposable, within non-restrictive nature, which allows an approach of a new device for electrochemical sensing and biosensing.

Formation of a ZnO–C Composite with a Nanocrystalline Structure

The formation of a nanocrystalline composite of a ZnO–C system with simultaneous mechanical activation of a mixture of zinc oxide and graphite powders in a ball mill in an inert atmosphere is studied. It is shown that the presence of graphite reduces the efficiency of dispersing ZnO crystallites. The following principal dispersion mechanisms of graphite are determined: the fragmentation of particles due to the impact of grinding bodies and the exfoliation of flakes by submicron zinc oxide particles. It has been established that a composite system is formed as a result of the prolonged mechanical activation effect on the ZnO–graphite mixture, which is a nanocrystalline zinc oxide powder with uniformly distributed inclusions of micro- and nanocrystalline graphite, turbostratic carbon, exfoliated graphene structures, and amorphous carbon.

Selective Zinc Removal from Electric Arc Furnace (EAF) Dust by Using Microwave Heating

Recycling of electric arc furnace (EAF) dust helps to avoid disposal of wastes, conserves resources, and minimizes its environmental impact. This study aimed to investigate the selective zinc removal from EAF dust by means of microwave heating oven as a heat source. The effect of microwave heating temperature on the selective zinc removal from EAF dust was studied at temperatures of 750 °C, 850 °C, and 950 °C. The mixture of EAF dust and graphite was well homogenized and compressed to pellet and heated for 20 min at the microwave power of 1.1 kW. X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM–EDS) techniques were used to characterize the residue after microwave treatment. The results indicated that the reduction and the recovery of zinc increase with the rising temperatures. The temperature of 750 °C was insufficient for the volatilization of zinc. Zinc removal of 94% was achieved after microwave heating at 950 °C. The residue that remained in the crucible was composed mainly of metallic iron and calcium ferrite. These results indicated that a temperature of 950 °C is suitable for selective removal of zinc from EAF dust, which is in accordance with the thermodynamic calculations.