Graphite Nano Research Articles

Study on Wear Behaviour of Mg-Gr-WC Nanocomposite Using Response Surface Methodology

The wear behavoiur of hybrid magnesium matrix nano-composite reinforced with nano graphite (1, 2 and 3 Wt.%) and nano tungsten carbide particles (1 Wt.%) fabricated by ultrasonic vibration aided stir casting method is investigated. Impact of weight percentage of reinforcement, applied load and roller speed on wear characteristics is investigated using block-on-roller type multi-tribotester at room temperature with the help of box-behenken design based response surface methodology. A second order regression model is generated. ANOVA analysis is used to find the influence of selected parameters on wear performance of composites. It is seen that Wt.% of reinforcements, load and speed are significantly affecting the wear characteristics while the interaction between Wt.% and speed is also significant at confidence level 95%. SEM of worn surface is done to check the presence of several wear modes

Evolution of Nanostructure and Metastable Phases at the Surface of a HCPEB-Treated WC-6% Co Hard Alloy with Increasing Irradiation Pulse Numbers

This work investigates the mechanisms of the microstructure evolution in the melted surface layers of a WC-6% Co hard alloy when increasing the number of pulses of irradiation by high-current pulsed electron beam (HCPEB) treatment. After one pulse of irradiation, about 50% of the stable hcp WC phase was melted and resolidified into the metastable fcc form (WC1−x). When increasing the numbers of pulse irradiation, the WC phase decomposed into ultrafine-grained WC1−x plus nanosized graphite under our selected energy condition. Because of the rapidity of HCPEB carried under vacuum, the formation of the brittle W2C phase was avoided. In the initial Co-rich areas, where the Co was evaporated, melting and solidification led to the formation of nanostructures Co3W9C4 and Co3W3C. The volume fraction of the nano domains containing WC1−x, Co3W9C4, and Co3W3C phases reached its maximum after 20 pulses of irradiation. The improved properties after 20 pulses are therefore due to the presence of nano graphite that served as lubricant and dramatically decreased the friction coefficient, while the ultrafine-grained carbides and the nano domains contribute to the improvement of the surface microhardness and wear resistance.

Development of sunlight-driven eutectic phase change material nanocomposite for applications in solar water heating

Organic phase change materials (PCMs) have been utilized as latent heat energy storage medium foreffective thermal management. In this work, a PCM nanocomposite, consisting of a mixture of two organicPCMs (referred to as eutectic gel PCM) and minimal amount (0.5 wt%) of nanographite (NG) as asupporting material, was prepared. Differential scanning calorimeter was used to determine the meltingtemperature and latent heat of pristine PCM, paraffin (61.5 °C and 161.5 J/g), eutectic gel PCM (54 °C and158 J/g) and eutectic gel PCM nanocomposite (53.5 °C and 155 J/g). The prepared PCM nanocompositesexhibited enhanced thermal conductivity and ultrafast thermal charging characteristics. The nanocompositeswere employed for two different applications: (i) providing hot water using an indigenously fabricatedsolar water heating (SWH) system and (ii) solar rechargeable glove that can be rapidly warmedand used. Experimental results on SWH system show that the use of PCM nanocomposites helps to increasethe charging rate of PCM while reducing the discharging rate of heat by PCM to water, thus enhancingthe maximum utilization of solar energy and hence improving the efficiency of the SWH system.The experimental results on solar rechargeable glove revealed that the glove has the ability to retain thetemperature up to 3 hours.

Microstructural evolution in ultrafine grained Al-Graphite composite synthesized via combined use of ultrasonic treatment and friction stir processing

An attempt was made to develop ultrafine grained Al-Graphite composites through friction stir processing (FSP). Al-Graphite composite was initially prepared using stir casting technique and it subsequently subjected to ultrasonic treatment prior to solidification. The results showed that the ultrasonic treatment during the composite preparation reduced the porosity, graphite particles' agglomeration and the graphite particles' size in the composite. The ultrasonic treated Al-Graphite composite was subjected to a single pass FSP at a constant tool rotational speed of 1600 rpm with three different feed rates, of 20 mm/min, 40 mm/min and 60 mm/min. The microstructure of FSPed composites within the stir zone exhibited a fine recrystallized grain structure due to the combined effect of severe plastic deformation and frictional heat generation during FSP. After the single pass of FSP, the grain size of the composite was reduced from 150 μm to 14 μm, 6 μm and 0.5–1 μm for the tool transverse speeds of 20 mm/min, 40 mm/min and 60 mm/min, respectively. Distribution of graphite particles in Al matrix was significantly improved after FSP process due to the strong stirring action of the rotating tool. Most importantly, microstructural analysis suggested that a substantial reduction in graphite particles' size could be achieved with the aid of FSP process. FSPed Al-Graphite samples exhibited superior hardness as compared to the unprocessed composites due to the uniform dispersion of fine graphite particles in ultra-fine grain structure. In a nutshell, ultrafine grained Al-Graphite composites with uniform dispersion of Graphite nano particles were produced using a single pass FSP process.

Nanographite-based fluorescent biosensing of Salmonella enteritidis by applying deoxyribonuclease-assisted recycling

The authors describe a low-cost and sensitive method for the fluorometric determination of Salmonella enteritidis (S. enteritidis). It is based on the use of nanographite (NG) as a quencher of fluorescence, and on cyclic signal amplification by using deoxyribonuclease I (DNase I). The probe containing a capture probe and two short sequences (probe 1 and probe 2) labeled with carboxyfluorescein (FAM) are used as the signal probe that is adsorbed on the surface of NG via p-stacking interactions. Adsorption results in quenching of the fluorescence of FAM. If S. enteridis is introduced, fluorescence is restored due to the displacement of the probe from the surface of the NG due competitive binding. The signal is considerably amplified by applying DNase I-mediated target recycling. The assay has a linear response that covers the 1 to 50 nM concentration range, with a 0.5 nM lower limit of detection (LOD). A milk sample spiked with S. enteritidis was analyzed and the detection limit is as low as 50 colony-forming units (CFU) per mL. Accordingly, this biosensor is highly sensitive and selective but also cost-effective. Conceivably, the detection scheme may be extended to the detection of other biomolecules.

Highly sensitive and selective aptasensor for detection of adenosine based on fluorescence resonance energy transfer from carbon dots to nano-graphite

In this article, a novel aptasensor was fabricated by modifying carbon dots (CDs) with adenosine aptamer (CDs-aptamer) for sensitive, selective and quantitative detection of adenosine (AD). When nano-graphite (NG) as an energy acceptor was added into the CDs-aptamer (energy donor) solution, the fluorescence of CDs-aptamer was quenched due to fluorescence resonance energy transfer (FRET). When AD was present in the solution of CDs-aptamer/NG, the process of FRET was inhibited because of the specific combination between AD and AD aptamer. As a result, the fluorescence of CDs-aptamer was restored due to the dissociation of CDs-aptamer from NG and its change was proportional to the AD concentration. Under the optimized conditions, a linear range was found to be 2–50nM for the detection of AD with a detection limit of 0.63nM. Furthermore, the application of the proposed approach was demonstrated in real sample with satisfying results and it showed promise in diagnostic purpose.

Thermal conductivity, thermal diffusivity, and volumetric heat capacity of silicone elastomer nanocomposites

Silicone elastomer (SiR) nanocomposites were prepared using multiwalled carbon nanotubes (MWCNT) and nano-graphite (NG). The morphology of the SiR nanocomposites has been studied using scanning electron microscopy and high-resolution transmission electron microscopy techniques. Detailed analysis of the morphology reveals a uniform distribution of the MWCNT and NG filler particles in the silicone matrix. On increasing the filler loading, a continuous network structure is formed and aggregation takes place. The effect of the MWCNT and NG loadings on the thermal properties of the silicone elastomer has been investigated. The thermal properties of the SiR nanocomposites were measured by a thermal properties analyzer based on the transient hot-wire method. Studies also suggest that incorporation of nanoparticles improves the thermal conductivity of SiR nanocomposites. The thermal conductivity of SiR nanocomposites increased from 0.200 W/(m K) to 0.440 W/(m K) and to 0.310 W/(m K) for 6 wt% MWCNT and NG loadings, respectively. Because of the positive temperature coefficient and the conductive nature of the nanoparticles, the thermal conductivity of the material increased on increasing the temperature. The thermal diffusivity and the volumetric heat capacity of the SiR nanocomposites were measured. The thermal diffusivity of the SiR nanocomposites increased from 0.1194 mm2/s to 0.3209 mm2/s and to 0.2050 mm2/s for 6 wt% MWCNT and NG loadings, respectively. This indicates that the temperature response becomes faster with MWCNT and NG loadings. The volumetric heat capacity of the silicone elastomer nanocomposites decreased from 1.80 MJ/(m3K) to 1.34 MJ/(m3K) and to 1.40 MJ/(m3K) for 6 wt% MWCNT and NG loadings, respectively. Thus, MWCNT particles are more effective in increasing the thermal conductivity and diffusivity of the SiR nanocomposites, when compared to NG fillers at any loading.

The Effect of Nano Graphite Particle Content on the Wear Behaviour of ZA27 Based Hybrid Composites

ZA27 based hybrid composites with dry lubricating particles and hard particles can be used for bearing applications with their good tribological properties instead of the traditional bearing materials. In this study, the wear behaviour of ZA27 based hybrid composites reinforced nano-graphite particulates and hard nano-alumina (Al2O3) particulates were investigated under dry sliding conditions. While the content of nano-alumina that is one of reinforced materials was selected in 4 vol. %, the contents of nano-graphite particulates were determined in different volumes (%1-%2-%3 and %4). The effect of graphite content was studied on wear behaviour under different sliding distance conditions. A block-on-disc sliding wear testing apparatus was used to carry out dry wear tests. The sliding distances was found to be significant parameter detecting effect of graphite content. The worn surfaces were investigated by scanning electron microscopy (SEM) and the wear mechanisms were identified. While the lowest wear loss was seen in hybrid nanocomposite with content of 4 vol. % graphite and 4 vol. % alumina, the highest wear loss was determined in ZA27. It was determined that abrasion is the dominant mechanism in all hybrid nanocomposites except for composite including 4 vol. % graphite and 4 vol. % alumina. However, the worn surface of the hybrid nanocomposite that is with content of 4 vol. % graphite and 4 vol. % alumina showed that adhesion is dominant as the wear mechanism.

Development of Prussian Blue and Fe(bpy)32 + hybrid modified pencil graphite electrodes utilizing its intrinsic iron for electroanalytical applications

Pencil lead is composed of clay and graphite and it has been widely used as a low-cost electrode system in electrochemistry. There are a few reports on chemical modification of PGE as oxygen functionalized surface that has been prepared via a pre-anodization technique for electro-analytical applications. For the first time in this work, we introduce a new strategy for electrochemical derivatization of PGE as Prussian blue (PB) and Fe(bpy)32+ functionalized PGEs (i.e., PGE-PB and PGE-Fe(bpy)32+), utilizing its intrinsic iron (1.31wt.%), in 0.1M KCl-HCl medium. Potential cycling of the PGE with Fe(CN)63− (as solution phase system) and bipyridyl (as surface adsorbed system) resulted in a facile formation of the hybrid complexes on the PGE surface. Physico and electrochemical characterization of PGE-PB and PGE-Fe(bpy)32+ modified electrodes by Raman, FT-IR and UV–Vis spectroscopies, cyclic voltammetry and several control experiments (graphite nano powder, clay, Fe2O3 modified electrodes) evidenced the formation of surface confined complexes on PGE. It was found that the intrinsic iron in clay is responsible for the complexation reactions. Selective electrocatalytic function for the H2O2 reduction reaction was demonstrated as an application of the PGE-PB system.

Development of sunlight-driven eutectic phase change material nanocomposite for applications in solar water heating

Organic phase change materials (PCMs) have been utilized as latent heat energy storage medium for effective thermal management. In this work, a PCM nanocomposite, consisting of a mixture of two organic PCMs (referred to as eutectic gel PCM) and minimal amount (0.5 wt%) of nanographite (NG) as a supporting material, was prepared. Differential scanning calorimeter was used to determine the melting temperature and latent heat of pristine PCM, paraffin (61.5 °C and 161.5 J/g), eutectic gel PCM (54 °C and 158 J/g) and eutectic gel PCM nanocomposite (53.5 °C and 155 J/g). The prepared PCM nanocomposites exhibited enhanced thermal conductivity and ultrafast thermal charging characteristics. The nanocomposites were employed for two different applications: (i) providing hot water using an indigenously fabricated solar water heating (SWH) system and (ii) solar rechargeable glove that can be rapidly warmed and used. Experimental results on SWH system show that the use of PCM nanocomposites helps to increase the charging rate of PCM while reducing the discharging rate of heat by PCM to water, thus enhancing the maximum utilization of solar energy and hence improving the efficiency of the SWH system. The experimental results on solar rechargeable glove revealed that the glove has the ability to retain the temperature up to 3 hours.

Nano graphite as additive in soybean oil

Vegetable oil-based lubricants have several disadvantages as compared to mineral and synthetic ones, including low viscosity that not encourage the generation of a continuous film when the tribosystem runs, consequently, implying a mixt or boundary. This is why the additivation of such oils is of great interests for researchers, producers and users. This paper presents results of testing the soybean oil additivated with nano graphite (0.25%wt, 0.50%wt and 1%wt) on a four ball machine. The friction coefficient is slightly increased for the additivated lubricants, but no evident dependency on concentration and test conditions was noticed. Supplementary tests will give the opportunity of a statistical approach of this parameter. Any concentration of nano graphite makes the wear parameter (wear scar diameter) to slightly increase as compared to the values obtained for the non-additivated soybean oil. The increase of the nano graphite concentration in this vegetable oil does not influence significantly the wear parameter, meaning that, at least for the tested regime, this is not an efficient anti-wear additive.

EFFECT OF NANO FERTILIZATION, CHEMICAL AND HUMIC ACID ON THE VEGETATIVE GROWTH, CHEMICAL COMPOSITION AND OIL YIELD OF CUMINUM CYMINUM L.

This experiment was carried out at a private farm near El-Mahalla: Gharbieah Governorate during the two successive seasons of 2013/2014 & 2014/2015 to study the effect of different levels of fertilization and nano-particles fertilizer on the vegetative growth, chemical composition and essential oil yield of Cuminum cyminum L. plants. Silicon and graphite nanoparticles were applied to cumin plants by spraying at three levels of 20, 40 and 60 mg/l two times. The resultes showed that, using 75 % NPK dose + humic acid and 60 mg/l nano graphite gave the highest values of growth parameters, (plant height, number of both branches and umbels/ plant) while the treatment of 75 % NPK dose +2g/plant humic acid and 40 mg/l nano graphite gave the highest values of chlorophyll a and b. The treated plants with 100 % NPK and 20 mg/l nano silica gave the highest values of N and P percentages. While, the highest K % and oil % were obtained by using 100 % NPK dose and 60 mg/l nano graphite. For the major identified components in the oil were p-menta-1-en 7-al from using 75% NPK +2g/plant humic acid with 40 mg/l nano silica. It can be recommended to apply 75 % NPK dose + 2g/plant humic acid and/ or 100 % NPK with 60 mg/l nano graphite for both to obtain the highest vegetative growth parameters and essential oil yield of Cuminum cyminum L.

Nano-graphite controlling properties of novel composites with damping-absorption functions and storage-loss behaviors: Nano-graphite/PZT-PMN-PNN/RTV

To clarify the influence of nano-graphite (NG) on the comprehensive performances of Nano-graphite/PZT-PMN-PNN/RTV composites, composites with damping-absorption performances and storage-loss behaviors based on Room Temperature Vulcanizing silicone rubber (RTV), PZT matrix ceramics, NG as conductive agent were fabricated employing three steps methods of ball-milling, three-roller milling and pressing. The effects of NG on storage, loss and damping properties were investigated by the method of DMTA. Absorption and mechanical performances are measured by the method of standing wave tube and TG. The morphologies, chemical and phase structures of composites are characterized by SEM, XRD and IR. The research indicated that both doping of NG and the combination of PZT-PMN-PNN/RTV can be proposed to improve greatly the comprehensive performance of RTV matrixes. There would be more excellent comprehensive properties in NG/PZT-PMN-PNN/RTV composites as increasing rate of 65% in d33, storage modulus of 3010 MPa, loss modulus of 205 MPa, and damping coefficient tanδ of 0.26 and, absorption coefficients of 0.6–0.7 with the frequency of 400–1600 Hz. Also, the improvement in NG amounts for composites can lead to the enforcement of stress for NG/ZT-PMN-PNN/RTV composites, but it caused neither the preferential growth in any a single crystal surface, nor the appearance of solid solution.

Conductive inks of graphitic nanoparticles from a sustainable carbon feedstock

Microwave plasma splitting of biogas to solid carbon forms is a promising technique to produce large quantities of sustainable carbon based nano materials. Well defined graphitic nano carbons have been produced exhibiting graphene multilayers in turbostratic packing. After heat treatment, the purified material has been used to formulate stable, aqueous dispersions. These dispersions are used directly as inks, allowing the preparation of conductive membranes with remarkable resistivity. Nano carbons derived by plasma processes constitute a promising alternative to carbon black because they can be prepared from renewable sources of methane or natural gas, are calibrated in size, exhibit high conductivity, and have promising perspectives for chemical and material science purposes.

Electro Chemical Machining of Aluminum-Boron Carbide-Nanographite Composites

Non-traditional machining process had made possible the machining of hard to cut materials. Among several non-traditional processes electrochemical machining has been given attention since there occurs no burrs or tool wear. Composites with nano reinforcements had outclassed their counterparts in terms of the properties shown by the nano composites. In the present work aluminium matrix has been reinforced with boron carbide and nano graphite which is added as a solid lubricant to improve tribological properties. The composite is subjected to electrochemical machining with a view of optimizing the process parameters. The process involves introducing abrasive particles while machining which aids in machining. Optimization of process parameters was based on the response surface methodology techniques with four independent input parameters such as voltage, current, electrolytic concentration and feed rate and ECM process performance in terms of material removal rate and overcut.

KOH-activated graphite nanofibers as CO2adsorbents

Porous carbons have attracted much attention for their novel application in gas storage. In this study, porous graphite nano-fiber (PGNFs)-based graphite nano fibers (GNFs) were prepared by KOH activation to act as adsorbents. The GNFs were activated with KOH by changing the GNF/KOH weight ratio from 0 through 5 at 900°C. The effects of the GNF/ KOH weight ratios on the pore structures were also addressed with scanning electron microscope and N2 adsorption/desorption measurements. We found that the activated GNFs exhibited a gradual increase of CO2 adsorption capacity at CK-3 and then decreased to CK-5, as determined by CO2 adsorption isotherms. CK-3 had the narrowest micropore size distribution (0.6–0.78 nm) among the treated GNFs. Therefore, KOH activation was not only a significant method for developing a suitable pore-size distribution for gas adsorption, but also increased CO2 adsorption capacity as well. The study indicated that the sample prepared with a weight ratio of ‘3’ showed the best CO2 adsorption capacity (70.8 mg/g) as determined by CO2 adsorption isotherms at 298 K and 1 bar.

Synthesis and thermal properties of the MA/HDPE composites with nano-additives as form-stable PCM with improved thermal conductivity

For the purpose of improving the thermal conductivity of the form–stable phase change materials (FSPCM), two types of nano–powders with high thermal conductivity were added into the samples. In the modified FSPCM, myristic acid (MA) was used as a solid–liquid phase change material (PCM), high density polyethylene (HDPE) acted as supporting material to prevent the leakage of the melted MA. Nano–Al2O3 (NAO) and nano–graphite (NG) were the additives for thermal conductivity enhancement. Scanning electronic microscope (SEM), Fourier transformation infrared spectroscope (FT–IR) and X-ray diffractometer (XRD) were used to analyze the microstructure, chemical structure and crystalline phase of the samples, respectively. Furthermore, the specific latent heat and phase transition temperature, thermal conductivity and thermal reliability were investigated using differential scanning calorimeter (DSC), thermal conductivity meter and thermo–gravimetric analyzer (TGA). The results showed that the MA was uniformly absorbed in the HDPE matrices and there was no leakage during the melting process when the mass fraction of the MA in the MA/HDPE composite was less than 70%. The DSC results revealed that the modified FSPCM have a constant phase change temperature and high specific latent heat. The thermal conductivity of the FSPCM was measured in the solid (30°C) and liquid (60°C) states of the MA. When the mass fraction of nano–powder additives is 12%, the thermal conductivities of the FSPCM increase by 95% (NAO) and 121% (NG) at 30°C. It is anticipated that the FSPCM possess a potential application for thermal energy storage.

Single step rubbing for highly efficient fabrication of flexible transparent conductive films featured with micro conductive channels on Polyvinylchloride surface

In this research, we proposed and developed a “single step rubbing method” to fabricate flexible transparent conductive films with highly efficiency, and such films are featured with micro conductive channels embedded in Polyvinylchloride matrix. Based on the intrinsic wear properties of Polyvinylchloride films and intrinsic self-lubrication property of graphite, micro conductive channels and flexible transparent conductive films could be obtained through a convenient rubbing process of commercial nano graphite raw materials. It is a highly efficient technology as the progress consumes only several minutes from raw materials to final products and its benefits in economic, environment and energy aspects. Films with surface resistivity from 35 to 500 kΩ sq−1, and optical transparency from 80 to 95 % at 550 nm can be obtained. The surface stability of the films is strong enough to protect them from aging under destructive surface treatments. Finally, the samples show strain sensitivity with high stability, which means that the samples can also be applied as transparent strain sensing films. Not only the fabrication method but also the TCFs/strain sensing films are very promising to be applied in flexible electronics.

Nanofibrillated cellulose/nanographite composite films

Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite(NG) in composite films, and, it has, however been a challe ...

A multi wavelength Raman scattering study of defective graphitic carbon materials: The first order Raman spectra revisited

The Raman spectra of a number of defected graphitic carbonaceous materials have been recorded using a large panel of laser exciting lines ranging from 1064 to 325 nm. They concern Arkema and Nanocyl multiwall nanotubes, Pyrograph nano filaments, heat-treated glassy carbons and graphite nano platelets. A particular attention was paid on the characteristic spectral range (≈1000–1300 cm−1) of the so-called “D4” band. It is shown that in fact three different components participate to the scattered signal in this spectral range, whose relative intensities depend on the carbon considered. They include the dispersive D″ band, an additional dispersive band denoted D** and a non-dispersive band denoted D*. When considering the different defect-induced double resonance inter-valley scattering processes, and according to symmetry considerations, these components are assigned to phonon modes belonging to different dispersion branches away from the K point of the Brillouin zone in the Γ-K direction (D″), in the K-M direction (D**) and in the very close vicinity of the K point (D*).