Influence of Bulk Graphite Density on Electrical Conductivity (original) (raw)
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PloS one, 2016
In this paper, we report how few layers graphene that can be produced in large quantity with low defect ratio from exfoliation of graphite by using a high intensity probe sonication in water containing liquid hand soap and PVP. It was founded that the graphene powder obtained by this simple exfoliation method after the heat treatment had an excellent exfoliation into a single or layered graphene sheets. The UV-visible spectroscopy, FESEM, TEM, X-ray powder diffraction and Raman spectroscopy was used to analyse the graphene product. The thermal diffusivity of the samples was analysed using a highly accurate thermal-wave cavity photothermal technique. The data obtained showed excellent enhancement in the thermal diffusivity of the graphene dispersion. This well-dispersed graphene was then used to fabricate an electrically conductive polymer-graphene film composite. The results demonstrated that this low cost and environmental friendly technique allowed to the production of high qualit...
Facile synthesis of graphene by ultrasonic-assisted electrochemical exfoliation of graphite
Materials Today: Proceedings, 2020
Graphene, a 2-dimensional form of carbon, attracted significant attention in a wide range of applications such as energy storage, power generation, chemical sensors, composite materials owing to its unmatched physical and chemical properties. In this study, graphene powder was synthesized by ultrasonic-assisted electrochemical exfoliation of the graphite electrode from acidic bath. An external ultrasonic bath (ultrasonic frequency of 40 kHz and ultrasonic power of 180 W) was employed to provide ultrasonic assistance during the electrochemical exfoliation process. The synthesized graphene powder was characterized with FTIR spectroscopy, Raman spectroscopy, XRD, and SEM techniques to study the chemical, microstructural and morphological properties. FTIR spectrum exhibited the CO and O-H functional groups and the C=C stretching of the hexagonal ring of graphene. Raman spectrum showed two sharp peaks for I D and I G bands at 1350cmAˋ1and1350 cm À1 and 1350cmAˋ1and1580 cm À1 , respectively. The XRD results revealed the polycrystalline nature of graphene powder. The SEM results showed various sizes and shapes of graphene powder. Our proposed method shows huge potentials for facile synthesis of graphene powder on a large scale.
Graphene Synthesis via Exfoliation of Graphite by Ultrasonication
Graphene has newly grabbed the attention of many researchers and scholars for it's huge range of properties, mainly high surface area is the most innovative field of research. High surface area property has a great significance for its demand in almost all applications in addition to supercapacitors. Accordingly, an attempt here is accomplished to create the graphene by sonication method using ODCB solvent. Different characterization techniques are mentioned in support of the work accomplished and it is found that the interlayer distance between graphite layers increases with increasing duration of sonication process. In XRD result, it can be found that first peak at 2θ of 26.4 degree disappears and a distinguishable peak at 11.3 degree with inter graphite layer spacing in close value with 0.78 nm in association with some other diffraction peaks appear. SEM images very nicely represent homogeneous graphene film with particle size varying from 42 to 150 nm. UV-VIS absorption spectra suggests that the peak absorption in graphene decreases with high wavelengths. At 210 nm, a peak can be noticed and one more peak around 226 nm with a little bit less intensity of absorption peak can be observed in UV-VIS spectra. The details offered by SEM, XRD and UV-VIS throughputs are also mentioned. It is quoted that upon sonication the distance between graphite layers increases, thereby originating graphene. Thus it can be concluded that the graphene with enormous extraordinary properties (including Super capacitor) can be synthesized following the sonication method using organic solvents. Long hour processing via sonicator leads to formation of homogenous dispersion of graphene in case of ODCB. For thorough exfoliation of graphite, the sonication should be maintained with a very dilute system in order to reduce the importance of the graphene sheets recombination process.
Properties of Graphene Flakes Obtained by Treating Graphite with Ultrasound
Ukrainian Journal of Physics
A possibility to obtain graphene and graphene layers with the help of the ultrasound (US) treatment of pyrolytic graphite in an N-methyl pyrrolidone (NMP) solution has been demonstrated. Raman spectroscopy is confirmed to be an effective method for monitoring the graphite transformation into graphene. By varying the time of the ultrasonic treatment of pyrolytic graphite in the NMP solution, optimum regimes for the fabrication of graphene flakes with various numbers of layers are determined. In particular, the US treatment for 5 h is shown to be sufficient for producing a colloidal solution of graphene flakes, most of which are singlelayered. It is shown that the longer US treatment results in larger intensities of Raman bands and ′ , which testifies to a larger number of defects in the graphene layers. The average distances between defects are estimated for various times of US treatment. The influence of vacancy and edge defects on the intensity band ratio / ′ is analyzed. Vacancies are found to be the prevailing type of defects in the graphene flakes. K e y w o r d s: graphene, Raman spectroscopy, ultrasound treatment, vacancy and edge defects, scanning electron microscopy.
Nanotechnology, 2011
A simple one-stage solution-based method was developed to produce graphene nanoribbons by sonicating graphite powder in organic solutions with polymer surfactant. The graphene nanoribbons were deposited on silicon substrate, and characterized by Raman spectroscopy and atomic force microscopy. Single-layer and few-layer graphene nanoribbons with a width ranging from sub-10 nm to tens of nm and length ranging from hundreds of nm to 1 µm were routinely observed. Electrical transport properties of individual graphene nanoribbons were measured in both the back-gate and polymer-electrolyte top-gate configurations. The mobility of the graphene nanoribbons was found to be over an order of magnitude higher when measured in the latter than in the former configuration (without the polymer electrolyte), which can be attributed to the screening of the charged impurities by the counter-ions in the polymer electrolyte. This finding suggests that the charge transport in these solution-produced graphene nanoribbons is largely limited by charged impurity scattering.
Analysis of the Effect of Temperature and Time for Ultrasonication on Graphite Structure
Proceedings of the Mathematics, Informatics, Science, and Education International Conference (MISEIC 2019), 2019
Graphite is a carbon allotrope with special bonding characteristics. These bonds can be altered given ultrasonic waves to be another form of bond or loosened. Changes in bonds will cause changes in bond characteristics to other forms of carbon allotropes. By varying ultrasonication process (time and temperature), the change in bonding or functional groups could be analyzed by changes in the structure of carbon. The ultrasonication process resulted in the bonding of oxygen atoms, produced bonding of C atoms with O, either as single or double bond. The new bond formed was linearly proportional to change in ultrasonication time and temperature. C bond with O caused carbon to change into allotrope of graphite oxide carbon, this was supported by the results of Raman spectroscopy characterization, where the defect of carbon was increased compared to carbon without ultrasonication. The intensity of the defect increased from 60 a.u to 265 a.u.
Advancement in liquid exfoliation of graphite through simultaneously oxidizing and ultrasonicating
J. Mater. Chem. A, 2014
Layered crystals, once exfoliated in liquids, create nanosheets with large surface area and likely generate electron band gaps. The current liquid exfoliation of graphite is performed by either oxidation, ultrasonication or the oxidation followed by ultrasonication; these methods are respectable but have limitations in general: the oxidation actually produces graphene oxide while the sonication is timeconsuming with a low yield. In this paper we report a highly effective yet simple approach for the fabrication of high-quality graphene; the approach consists of simultaneously oxidizing and ultrasonicating graphite for merely 60 min, followed by washing and filtration. Exfoliation was markedly promoted by the simultaneous treatment, where 80% of the sheets comprise single or few layers with lateral dimensions ranging 50 nm to over 100 nm; their carbon to oxygen ratio is at 8.85; the ratio of Raman D-to G-band intensity is as low as 0.211; and the sheets can be stably dispersed in acetone for at least 48 hours and they have an electrical conductivity over 600 S cm À1 . A thin graphene film made by casting exhibited a sheet resistance of $1000 U square À1 with 80% transparency at 550 nm. Fig. 6 Statistics and AFM micrographs and height profiles of graphene sheets made by oxidi-sonication for 20 min (a1-3), 40 min (b1-3) and 60 min (c1-3).
Nanoscience and Nanotechnology, 2022
This article presents a brief review of some methods of obtaining graphite and graphene nanosheets, the latter a material that has attracted much attention from the scientific community in recent years, due to its different properties and possible applications. Next, the work addresses the subject of graphite exfoliation by the sonication method, which is simple and versatile, and by which it is possible to obtain graphite sheets with thicknesses of units of nanometers. Furthermore, the work presents experimental data that show the influence of the sonication time interval on the dimensions of graphite nanosheets. The results indicate that longer the sonication time interval, smaller the dimensions of the graphite sheets.
Synthesis of Graphene Oxide Through Ultrasonic Assisted Electrochemical Exfoliation
Open Chemistry, 2019
We report a 'green', simple and efficient approach for the production of graphene oxide (GO) by ultrasonic assisted electrochemical exfoliation of graphite rods, and by using Improved Hummers' graphene oxide (IGO) as an electrolyte. The effects of applied bias, electrolyte concentration and the duration of the electrochemical exfoliation on the quality of the GO nanosheets were investigated. The produced graphene oxide with a high yield (> 48%), and the lowest defect was obtained in the ultrasonic assisted electrochemical exfoliation performed at 0.05% IGO mass percent in DI water and 50 V applied bias for 1 hour at room temperature. The structural, morphological and physical properties of the obtained nanostructures were analyzed by XRD, Raman, FESEM, STEM techniques and thermal conductivity analysis, respectively. The characteristic Raman bands were observed at 1354 cm-1 and 1590 cm-1 for the prepared GO nanosheets. The produced graphene oxides exhibited a lateral dimension of 3-7 µm revealed by field emission scanning electron microscopy (FESEM). It was observed that the thermal conductivity enhancement of 14.95% was obtained for GO, which was higher than the other IGO nanofluid (7.64%) with respect to DI water at 20 o C.
Materials Today: Proceedings, 2019
Graphene is a new wonder material that known as an atomic layer of graphite. Due to its exceptional mechanical, physical and chemical properties, it's used in different fields such as composites, medical, electronic, energy conversion, and for storage applications. So, preparation of graphene with high quality, low cost, large quantities became an important matter. In our study, planetary wet ball milling process used and modified to produce graphene from graphite flakes, preceded by annealing and sonication process that used as assistant factors to increase the cleavage and exfoliation rates on graphite structure. Morphological characteristics were investigated using scanning electron microscopy while the structural characterizations were studied using Raman spectroscopy. The exfoliated graphene sheets with fewest number of layers, some structural defects and small crystal size indicate the promising efficiency of the used methodology.