Graphite Nano Research Articles

Electrochemical characterization of mesoporous nanographite films

The mesoporous nanographite (NG) film material consisting of tiny flake-like graphite crystallites of nanometer-scale thickness is deposited onto carbon fibers with diameter of few micrometers using adapted plasma enhanced chemical vapor deposition (CVD) method. Macroscopic morphology parameters of NG material depend on deposition time duration so, that thickness of the NG coating is increased from 0.5 to 2 μm, whereas the average sizes of the individual crystallites and the pores between them are decreased from 0.5 to 0.1 nm, with deposition time extension from 15 to 60 min, respectively. The high resolution electron microscopy examinations indicate that the NG flakes consist of parallel graphene layers separated by about 0.34 nm and those layers are paired at the edges of the flakes producing arced structures. The electrochemical capacitance measurements were served for characterization of the mesoporous nanographite coating; the specific capacitance arising from the electrostatic charge accumulated at the electrode–electrolyte interface was estimated using cyclic voltammetry, galvanostatic charge/discharge measurements, and electrical impedance spectroscopy. The effects of the deposition time duration and other parameters of CVD process on electrochemical performance and structural properties of the prepared NG films are to be discussed.

Highly sensitive determination of dopamine by a turn-on fluorescent biosensor based on aptamer labeled carbon dots and nano-graphite

In this paper, a novel fluorescent biosensor based on DA aptamer labeled carbon dots (aptamer-CDs) and nano-graphite (NG) for the determination of dopamine (DA) was developed. In this system, aptamer-CDs were in charge of energy donor (fluorophor) and chemical recognition, while NG served as an energy acceptor. In the absence of DA, aptamer-CDs were adsorbed on the surface of NG through π-π stacking and hydrophobic interaction, which led to the fluorescence quenching of aptamer-CDs due to the surface energy transfer. When it was in presence, DA combined with its aptamer anchored on the surface of CDs to form specific globular chain structure which would detach from the surface of NG and thus the fluorescence intensity of aptamer-CDs was recovered. Under the optimal conditions, the fluorescence intensity of aptamer-CDs increased linearly with the increase of DA concentration in the range of 0.10–5.00nM and the limit of detection was 0.055nM. This method was successfully applied to the determination of DA in human urine samples with satisfactory results.

Investigation of Graphite Nano Particle Addition on the Physical and Mechanical Properties of ZA27 Composites

The physical and mechanical properties of composites consisting of ZA27 alloy reinforced with nano-sized graphite particles were investigated with the main objective of understanding the effect of the nano particulate reinforcement. These properties were determined by measuring the density, hardness and tensile strength values. The microstructure of the ZA27-Graphite (Gr) nanocomposites was investigated using a scanning electron microscope (SEM). The results indicated that density values of nano graphite added nanocomposites (GANs) decrease with increasing graphite rate while porosity ratio increases. Also the UTS and Brinell hardness values decreased with increasing graphite content.

Preparation, characterisation, and in vitro evaluation of electrically conducting poly(ɛ-caprolactone)-based nanocomposite scaffolds using PC12 cells.

In the current study, we describe the synthesis, material characteristics, and cytocompatibility of conducting poly (ɛ-caprolactone) (PCL)-based nano-composite films. Electrically conducting carbon nano-fillers (carbon nano-fiber (CNF), nano-graphite (NG), and liquid exfoliated graphite (G)) were used to prepare porous film type scaffolds using modified solvent casting methods. The electrical conductivity of the nano-composite films was increased when carbon nano-fillers were incorporated in the PCL matrix. CNF-based nano-composite films showed the highest increase in electrical conductivity. The presence of an ionic solution significantly improved the conductivity of some of the polymers, however at least 24 h was required to absorb the simulated ion solutions. CNF-based nano-composite films were found to have good thermo-mechanical properties compared to other conducting polymer films due to better dispersion and alignment in the critical direction. Increased nano-filler content increased the crystallisation temperature. Analysis of cell viability revealed no increase in cell death on any of the polymers compared to tissue culture plastic controls, or compared to PCL polymer without nano-composites. The scaffolds showed some variation when tested for PC12 cell attachment and proliferation, however all the polymers supported PC12 attachment and differentiation in the absence of cell adhesion molecules. In general, CNF-based nano-composite films with highest electrical conductivity and moderate roughness showed highest cell attachment and proliferation. These polymers are promising candidates for use in neural applications in the area of bionics and tissue engineering due to their unique properties.

Crack healing in concrete using various bio influenced self-healing techniques

Crack formation and progression under tensile stress is a major weakness of concrete. These cracks also make concrete vulnerable to deleterious environment due to ingress of harmful compounds. Crack healing in concrete can be helpful in mitigation of development and propagation of cracks in concrete. This paper presents the process of crack healing phenomenon in concrete by microbial activity of bacteria, Bacillus subtilis. Bacteria were introduced in concrete by direct incorporation, and thorough various carrier compounds namely light weight aggregate and graphite nano platelets. In all the techniques, calcium lactate was used as an organic precursor. Specimens were made for each mix to quantify crack healing and to compare changes in compressive strength of concrete. Results showed that bacteria immobilized in graphite nano platelets gave better results in specimens pre-cracked at 3 and 7days while bacteria immobilized in light weight aggregates were more effective in samples pre-cracked at 14 and 28days. In addition, concrete incorporated with bacteria immobilized in light weight aggregate, also exhibited significant enhancement in compressive strength of concrete.

Atomic layer deposition of TiO2and Al2O3on nanographite films: structure and field emission properties

Atomic layer deposition (ALD) of metal oxides (MO) was used to modify the properties of nanographite (NG) films produced by direct current plasma–enhanced chemical vapor deposition technique. NG films consist of a few layers of graphene flakes (nanowalls) and nanoscrolls homogeneously distributed over a silicon substrate with a predominantly vertical orientation of graphene sheets to the substrate surface. TiO2 and Al2O3 layers, with thicknesses in the range of 50 to 250 nm, were deposited on NG films by ALD. The obtained NG-MO composite materials were characterized by scanning electron microscopy, energy dispersive x-ray analysis, and Raman spectroscopy. It was found that ALD forms a uniform coating on graphene flakes, while on the surface of needle-like nanoscrolls it forms spherical nanoparticles. Field emission properties of the films were measured in a flat vacuum diode configuration. Analysis based on obtained current–voltage characteristics and electrostatic calculations show that emission from NG-TiO2 films is determined by the nanoscrolls protruding from the TiO2 coverage. The TiO2 layers with thicknesses of <200 nm almost do not affect the overall field emission characteristics of the films. At the same time, these layers are able to stabilize the NG films’ surface and can lead to an improvement of the NG cold cathode performance in vacuum electronics.

In vitro toxicity of carbon nanotubes, nano-graphite and carbon black, similar impacts of acid functionalization

Carbon nanotubes (CNT) and nano-graphite (NG) are graphene-based nanomaterials which share exceptional physicochemical properties, but whose health impacts are unfortunately still not well understood. On the other hand, carbon black (CB) is a conventional and widely studied material. The comparison of these three carbon-based nanomaterials is thus of great interest to improve our understanding of their toxicity. An acid functionalization was carried out on CNT, NG and CB so that, after a thorough characterization, their impacts on RAW 264.7 macrophages could be compared for a similar surface chemistry (15 to 120μg·mL−1 nanomaterials, 90-min to 24-h contact). Functionalized nanomaterials triggered a weak cytotoxicity similar to the pristine nanomaterials. Acid functionalization increased the pro-inflammatory response except for CB which did not trigger any TNF-α production before or after functionalization, and seemed to strongly decrease the oxidative stress. The toxicological impact of acid functionalization appeared thus to follow a similar trend whatever the carbon-based nanomaterial. At equivalent dose expressed in surface and equivalent surface chemistry, the toxicological responses from murine macrophages to NG were higher than for CNT and CB. It seemed to correspond to the hypothesis of a platelet and fiber paradigm.

Advance treatment by nanographite for Portland pulverised fly ash cement (the class F) systems

This is a full article that overcomes such some negative side effects as rapid coagulation and reduced early strength in class F fly ash-substituted cement (FFA-SC) by serving nano graphite particle (nG). This study uses class F fly ash (FFA), nG, and ASTM type I cement as constituent materials to prepare proper pulverized fly ash–Portland cement combinations (35% FFA + 65% ASTM I + 1.1% nG i.e.). Pastes include lime and/or lime + nG, and tap water to examine ups and downs in Ca(OH)2 content. Mortars also contain these prepared cements, tap water and/or tap water + super plasticizer (SP), and mortar sand in order to measure fluidity, flexural strength, and compressive strength according to present standard methods. Results indicate for FFA-SC system that the nano graphite particle increases the reduced early strength gain at early age, and the SP reduces the rapid coagulation. The use of nG also shows to be favorable in terms of the Ca(OH)2 content, the fluidity and the flexural strength gain, and compressive strength gain in FFA-SC system when compared to the pure Portland cement with and without nano graphite particle.

Modification of the Electrode Surface by Ag Nanoparticles Decorated Nano Diamond‐graphite for Voltammetric Determination of Ceftizoxime

AbstractA modified glassy carbon electrode with a film of nano diamondgraphite nano mixture decorated with Ag nanoparticles (AgNPsNDG/GCE) was constructed and used for sensitive voltammetric determination of ceftizoxime (CFX). Morphology of AgNPsNDG/GCE has been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental variables such as deposited amount of the modifier suspension, pH of the supporting electrolyte and accumulation potential and time were optimized by monitoring of CV and LSV responses of CFX. The results illustrate that AgNPsNDG/GCE exhibits an excellent electrocatalytic effect in the electro‐oxidation of CFX that leads to a considerable improvement in the corresponding anodic peak current. This also allows the development of a highly sensitive voltammetric sensor for the determination of CFX in pharmaceutical and clinical samples. Under the optimum conditions, the modified electrode showed a linear response to the concentration of CFX in the range of 0.02–7 µM with detection limit of 6 nM. The prepared modified electrode has some remarkable electrochemical properties such as simple preparation, high sensitivity, excellent repeatability and reproducibility and long‐term stability.

Field emission spectroscopy evidence for dual-barrier electron tunnelling in nanographite

Nanocarbon films with upstanding flake-like graphite crystallites of nanometre thickness were fabricated by carbon condensation from a methane–hydrogen gas mixture activated by a direct-current discharge. The nanographite (NG) crystallites are composed of a few graphene layers. The adjacent atomic layers are connected partially at the edges of the crystallites to form strongly curved graphene structures. The extraordinary field emission (FE) properties were revealed for the NG films with an average current density of a few mA/cm2, reproducibly obtained at a macroscopic applied field of about 1 V/μm. The integral FE current–voltage curves and electron spectra (FEES) of NG cathodes with multiple emitters were measured in a triode configuration. Most remarkably, above a threshold field, two peaks were revealed in FEES with different field-dependent shifts to lower energies. This behaviour evidences electron emission through a dual potential barrier, corresponding to carbon–carbon heterostructure formed as a result of the graphene bending.

Nanocomposite coatings on cotton and silk fibers for enhanced electrical conductivity

Electrically conducting carbon nanofillers like liquid exfoliated graphite (EG), nanographite (NG), carbon nanotube (CNT) and carbon nanofiber (CNF) were dispersed in thermoplastic polyurethane (TPU) matrix. HRTEM images and SAED patterns confirmed exfoliation of graphite and good dispersion of all nanofillers. The polymer dispersions were used to develop nanocomposite coatings on cotton yarn and silk fibers. These nanocomposite coated fibers showed significant improvements in electrical conductivity. Current-voltage (IV) plots indicated linearity for most of the nanocomposite coated fibers. Among the nanofillers, CNF and CNT have strong potential to impart stable conductivity on such fibers. The electrical conductivity of 10 wt% CNF based nanocomposite coated cotton yarn was 2 S/m; while it was more than 12 S/m for silk filament. 2 wt% CNT dispersed nanocomposite coating on silk also showed very good conductivity of 11 S/m. The large void fraction in coated cotton yarn (~12 %) is attributed for such difference in electrical conductivity. Hence, staple yarns are not suitable to develop such nanocomposite coated fibers. Both the resistance and impedance tests were carried out at different test lengths up to 5 cm and resistance and impedance (at 100 Hz, 120 Hz and 1 kHz) per cm was calculated with variable test length. As variations in test results were not very high it can be concluded that the uniformity in electrical conductivity is achieved through these coatings.

Manufacture of nano graphite oxides derived from aqueous glucose solutions and in-situ synthesis of magnetite–graphite oxide composites

A “bottom up” approach of manufacturing graphite oxides (GOs) derived from aqueous glucose solutions by virtue of an environmentally-friendly process and the way of in-situ synthesizing magnetite–GOs composites are described in this work in detail. The dehydrations among glucose molecules under hydrothermal condition result in the initial carbon quantum dots and ultimate GOs. The structural information of the GOs is obtained by the infrared, ultraviolet–visible and X-ray photoelectron spectra. The magnetite–GOs composites were obtained by a one-pot method under the same hydrothermal conditions as the one of preparing GOs. The composites perform high activities in catalytic degradation of Rhodamine B in the presence of hydrogen peroxides without extra heating or pH adjusting. Both the GOs and the magnetite–GOs composites are also assured by measurements of transmission electron microscope and X-ray powder diffraction.

Studying the Interactions of Polyethylene with Graphite in the Presence of Solvent by High Temperature Thermal Gradient Interactive Chromatography, Thermal Gradient Nuclear Magnetic Resonance Spectroscopy, and Solution Differential Scanning Calorimetry

High temperature thermal gradient interactive chromatography (HT-TGIC or TGIC) has emerged as an important analytical tool to determine the comonomer content distribution (CCD) present in copolymers of polyethylene (PE). The method separates the macromolecules according to the differences in their interactions, in solution, with a graphite stationary phase using temperature as a variant. It is vital to gain insight into the nature of these interactions in order to further improve the separation resolution and increase the accuracy of CCD measurement. Nuclear magnetic resonance (NMR) spectroscopy has been routinely applied for quantitative determination of comonomer content in olefinic copolymers. In this paper NMR has been adapted in a unique manner to monitor the temperature-dependent concentration of PE in solution in the presence of nanographite (NG). It was found that in the presence of NG a decrease in polymer concentration can be observed for both a semicrystalline PE homopolymer and a highly amorph...

Nano-graphite cold cathodes for electric solar wind sail

The nanographite (NG) films consisting of tiny graphite crystallites (nanowalls) are produced by carbon condensation from methane–hydrogen gas mixture activated by a direct current discharge. High aspect ratio and structural features of the NG crystallites provides efficient field electron emission (FE). Applicability and performance of the NG films in an electron gun (E-gun) of a solar wind thruster system with an electric sail (E-sail) is tested. The long-term tests are demonstrated suitability of E-gun assembly with the NG cathodes for the real space missions. The results of the tests are analyzed and physical mechanisms of the cathode aging and practical methods for improvement performance of the E-gun are proposed.

Preparation of graphene and graphene supported Pd catalysts for formic acid electrooxidation

Two kinds of graphene GN-1 and GN-2 with significantly increased specific surface area were obtained from nano graphite by different methods. The morphology and pore size distribution of GN-1 and GN-2 also have great differences. Using these two kinds of graphene as supports, Pd catalysts were prepared and designed as Pd/GN-1 and Pd/GN-2. The electrochemical specific surface area of Pd/GN-1 and Pd/GN-2 catalysts are 34.66 and 71.25 m2/g. The catalytic activities of Pd/GN-1 and Pd/GN-2 during the formic acid electrooxidation reaction are greatly improved compared with the Pd catalyst supported by nano graphite. The peak current densities of formic acid oxidation on Pd/GN-1 and Pd/GN-2 are 66.0 and 95.8 mA/cm2. The Pd/GN-1 and Pd/GN-2 catalysts also have good stability for formic acid electrooxidation.

Influence of Carbon Nanoparticles Morphology on Physical Properties of Polymer Composites

The paper presents in uence of diverse shapes and dimensions of carbon nanostructures on physical properties of polymer composites. Graphene nanoplatelets, carbon nanotubes, graphite nano bers, and graphite micro akes have been investigated as llers in polymethacrylate resin. Layers were deposited with printing techniques used in printed electronics technology such as screen printing and spray coating, both elaborated in our earlier works. Different sets of measurements have been performed for obtained layers with particular carbon nano llers. Thickness and topography have been examined using optical pro lometer. Morphology of nanostructures has been observed with scanning electron microscope. Moreover, sheet resistivity and optical transmission in visible wavelength have been measured. Also mechanical properties have been characterized for each polymer composite by conducting fatigue test which consisted of multiple bending cycles.

Methane Catalytic Cracking to Make Hydrogen and Graphitic Nano Carbons (Nanotubes, Microfibers, Microballs, Onions) with Zero Emission

Methane was catalytically decomposed to hydrogen and highly graphitic carbon nanotubes, microfibers, microballs, and nano onions. Over Mo x –Ni(Fe,Co) y –MgO z , single-walled carbon nanotubes (SWNTs) and thin-walled carbon nanotubes (TWNTs) were produced; over Ni/Y, individually separated SWNTs were generated; over La2NiO4, multiwalled carbon nanotubes (MWNTs) were made. Over Ni/MCM-41, with the addition of benzene, the carbon microballs (CMBs) were produced. Over Fe–Cr alloy and LaNi0.9Co0.1O3, the carbon nano onions (CNOs) and carbon microfibers (CMFs) were produced, respectively. The methane conversion efficiency and carbon growth rate followed the order: CNOs > CMBs > CMFs > MWNTs > TWNTs > SWNTs.

Nano graphite platelets enhanced blue emission in alternating current field induced polymer based electroluminescence devices using Poly (9,9-dioctylfluorenyl-2,7-diyl) as the emitter

We report a simple way of enhancing blue emission in Poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO) based alternating current field driven electroluminescence devices by mixing graphite nano platelets in the emission layer. Significantly strong and well resolved blue peaks at 437nm and 470nm are observed both in the devices’ electroluminescence and photoluminescence spectra with the presence of graphite nano platelets. The origin of this strong blue emission has been identified as the PFO’s beta-phase formation confirmed by transmission electron microscopy images and UV–Vis absorption spectra. The nano platelets loading in PFO solution can be controlled by the dispersion time in organic solvents. When the loading increases, the green emission in the electroluminescence spectrum can be reduced. This technique has been found useful in the generation of bright white light when illuminating through down conversion phosphor.

Study of workpiece vibration in powder-suspended dielectric fluid in micro-EDM processes

In micro-EDM (electrical discharge machining), improper removal of debris causes short-circuiting between a tool electrode and a workpiece and in turn, prevents continuous machining process. Therefore, a remarkably longer period of time is required to fabricate a through hole than that would be required when no short-circuiting took place. In order to solve this problem, the dielectric fluid is immersed with graphite nano powders to reduce machining time and improve surface quality due to the less frequent of arcing between the tool electrode and the workpiece. However, excess powders become debris and subsequently deteriorate the efficiency of machining. To fully exploit the effects of the suspended powders, we introduced vibration of the workpiece in order to remove the debris in the small gap between the workpiece and electrode efficiently. The experimental results showed that combination of these techniques improved machining stability, assured continuous machining processes, and significant reduction of the machining time. Reduction of the machining time and the surface roughness of the workpiece after machining were investigated with respect to the powder concentrations when the workpiece was vibrated at 1000 Hz.

Preparation and characterization of properties of nanographite-based cutting fluid for machining operations

Soluble oils are the most popularly used oils in metal-cutting industry. However, the regular application strategy, flood cooling, involves the problem related to its disposal. Hence, mist application can be seen as an alternative procedure. Since less amount of cutting fluid is used, its capacity to carry away heat and provide adequate lubrication is limited. Therefore, the heat carrying and lubricating abilities of soluble oil need to be enhanced. Graphite has better lubricating and cooling properties, and hence inclusion of graphite nano particles in cutting fluid may help in formulating a better coolant in machining operation. This paper consists of two parts. The first part consists of preparation of nano cutting fluid by different methods followed by their stability evaluation, and second part consists of characterization of the basic properties of nano cutting fluid.