Different Types Of Graphene Research Articles

Use of graphene (go and rGO) as a reinforcement filler to increase the beta phase in fluorinated copolymer nanocomposites

The present study aims to evaluate the influence of different types of graphene, graphene oxide (GO, synthesized by the Hummers method) and reduced graphene oxide (rGO, obtained by thermal reduction of GO) on the piezoelectric properties of composites based on PVDF copolymer. Hydrogen-fluorine interaction is expected to occur between GO or rGO and the fluorinated copolymer, increasing the β-conformation content in the polymer. The samples were prepared in the molten state at two concentrations of each charge inside a twin-screw extruder with interpenetrating screws. The characterizations of the nanocomposites were made according to their thermal and electrical properties. The effect of graphene incorporation into the P(VDF-TrFE) matrix was observed from thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results obtained indicated that the incorporation of graphene contributed to the increase in the β phase content of P(VDF-TrFE), which is indicative of the increase in its piezoelectricity.

Modified 3D Graphene for Sensing and Electrochemical Capacitor Applications.

Less defective, nitrogen-doped 3-dimensional graphene (N3DG) and defect-rich, nitrogen-doped 3-dimensional graphene (N3DG-D) were made by the thermal CVD (Chemical Vapor Deposition) process via varying the carbon precursors and synthesis temperature. These modified 3D graphene materials were compared with pristine 3-dimensional graphene (P3DG), which has fewer defects and no nitrogen in its structure. The different types of graphene obtained were characterized for morphological, structural, and compositional assessment through Scanning Electron Microscopy (SEM), Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) techniques. Electrodes were fabricated, and electrochemical characterizations were conducted to evaluate the suitability of the three types of graphene for heavy metal sensing (lead) and Electric Double-Layer Capacitor (EDLC) applications. Initially, the various electrodes were treated with a mixture of 2.5 mM Ruhex (Ru (NH3)6Cl3 and 25 mM KCl to confirm that all the electrodes underwent a reversible and diffusion-controlled electrochemical process. Defect-rich graphene (N3DG-D) revealed the highest current density, followed by pristine (P3DG) and less-defect graphene (N3DG). Further, the three types of graphene were subjected to a sensing test by square wave anodic stripping voltammetry (SWASV) for lead detection. The obtained preliminary results showed that the N3DG material provided a great lead-sensing capability, detecting as little as 1 µM of lead in a water solution. The suitability of the electrodes to be employed in an Electric Double-Layer Capacitor (EDLC) was also comparatively assessed. Electrochemical characterization using 1 M sodium sulfate electrolyte was conducted through cyclic voltammetry and galvanostatic charge-discharge studies. The voltammogram and the galvanostatic charge-discharge (GCD) curves of the three types of graphene confirmed their suitability to be used as EDLC. The N3DG electrode proved superior with a gravimetric capacitance of 6.1 mF/g, followed by P3DG and N3DG, exhibiting 1.74 mF/g and 0.32 mF/g, respectively, at a current density of 2 A/g.

A Novel Aqueous Asymmetric Supercapacitor based on Pyrene‐4,5,9,10‐Tetraone Functionalized Graphene as the Cathode and Annealed Ti3C2Tx MXene as the Anode (Small 25/2023)

Asymmetric Supercapacitors Pyrene-4,5,9,10-tetraone (PYT) molecules are noncovalently combined with two different types of graphene (GN and LO). The electrochemical performance of the PYT/GN composites is found to be significantly better than the LO-based composites. When matched with an annealed Ti3C2Tx MXene anode, the assembled asymmetric device (PYT/GN 4–5//A-Ti3C2Tx) delivers an outstanding energy density of 18.4 Wh kg−1 at a power density of 700 W kg−1. More details can be found in article number 2301449 by Xiaoyan Zhang and co-workers.

Role of adding carbon nanotubes in the electric and electromagnetic shielding behaviors of three different types of graphene in hybrid nanocomposites

Graphene-related materials (GRM) are promising materials to improve mechanical, electrical, and optical polymer properties. Adding multi-wall carbon nanotubes (MWCNT) on GRM nanocomposites promotes synergistic effects on its electrical properties and electromagnetic interference shielding effectiveness (EMI SE). This study focused on evaluating the addition of MWCNT on three different polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)/GRM nanocomposites. These hybrid nanocomposites were prepared by melt mixing using extrusion and injection-mold processes. The morphologies of the nanocomposites were evaluated by field emission gun scanning electron microscopy (FEG-SEM), and their proprieties were characterized by X-ray diffraction (XRD), oscillatory rheological, dielectric spectroscopy, and EMI SE analyses. The electrical behavior of all hybrid nanocomposites was anisotropic due to the injection-molded preparation process. The lateral size, thickness, and production method of the GRM were indicated to be critical factors for the electrical and EMI SE behaviors of these composites. The nanocomposites with GRM2, which had the smallest lateral size and thickness (graphene nanoplatelets), promoted total attenuation levels around 20 dB with 1.5 wt% of MWCNT, matching the EMI SE required for some commercial applications.

Challenges of Coating Textiles with Graphene

Electronic textiles (e-textiles) hold the key for seamless integration of electronic devices for wearable applications. Compared to other flexible substrates, such as plastic films, textiles are, however, challenging substrates to work with due to their surface roughness. Researchers at the University of Exeter, UK, demonstrated that using different coating techniques as well as different types of graphene coatings is the key to overcome this challenge. The results of coating selected monofilament textile fibres and woven textiles with graphene are discussed here. These conductive textiles are fundamental components in e-textiles, and some applications will be reviewed in this paper. That includes light-emitting devices, touch and position sensors, as well as temperature and humidity sensors. The possibility of triboelectric energy harvesting is also discussed as the next step to realise self-powered e-textiles.

Effect of the cross-linker content and type of graphene on the thermo-mechanical properties of nanocomposites

In this paper we study the influence of the type of graphene (GNP) and the different ratios of the crosslinking agent (XB)-resin epoxy (LY) on the thermo-mechanical properties of epoxy-graphene nanocomposites (GNP). Epoxy/GNP nanocomposites have been prepared using two different types of graphene: one non-functionalized (GNPn) and one amino functionalized graphene (GNPNH2). The content of graphene has been 6% and 10% by weight. The thermo-mechanical properties of the LY-XB thermoset and the nanocomposites have been determined through dynamic mechanical thermal analysis and tensile tests in a universal testing machine. The glass transition temperature and the storage modulus in the elastomeric zone (T>Tg) of the thermoset LY-XB and the nanocomposites have maximum values ​​for slightly rich amine content. The addition of graphene significantly increases the elastic modulus of the nanocomposites compared to the neat epoxy thermoset (LY-XB), both in the vitreous region (T<Tg) and in the elastomeric region (T>Tg). The thermoset LY-XB shows the best strength and toughness for the stoichiometric ratio XB/LY. The addition of graphene leads to more rigid but more fragile materials.

Low Operating Voltage Carbon-Graphene Hybrid E-textile for Temperature Sensing.

Graphene-coated polypropylene (PP) textile fibers are presented for their use as temperature sensors. These temperature sensors show a negative thermal coefficient of resistance (TCR) in a range between 30 and 45 °C with good sensitivity and reliability and can operate at voltages as low as 1 V. The analysis of the transient response of the temperature on resistance of different types of graphene produced by chemical vapor deposition (CVD) and shear exfoliation of graphite (SEG) shows that trilayer graphene (TLG) grown on copper by CVD displays better sensitivity due to the better thickness uniformity of the film and that carbon paste provides good contact for the measurements. Along with high sensitivity, TLG on PP shows not only the best response but also better transparency, mechanical stability, and washability compared to SEG. Temperature-dependent Raman analysis reveals that the temperature has no significant effect on the peak frequency of PP and expected effect on graphene in the demonstrated temperature range. The presented results demonstrate that these flexible, lightweight temperature sensors based on TLG with a negative TCR can be easily integrated in fabrics.

Transient absorption spectroscopy as a promising optical tool for the quality evaluation of graphene layers deposited by microwave plasma

The qualified analysis of structure, morphology and defects in graphene is crucial for graphene layers evaluation and development of various electro-optical applications. In this work, we present the detailed analysis of properties of planar graphene and vertical graphene nanosheets (VGNs) prepared by means of microwave plasma enhanced chemical vapour deposition method (PECVD), employing common analysis methods (scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman scattering spectroscopy), as well as ultrafast transient absorption spectroscopy (TAS) technique with different excitation wavelengths (at 350, 400 and 700 nm) to analyze excited state relaxation dynamics in different types of graphene. By measuring relaxation duration (or hot electrons cooling dynamics that originates from electron-phonon interactions, leading to phonon-phonon interactions) we showed that TAS provides with the information about phonons and defects in graphene. The complex analysis of graphene layers, in parallel to the TAS measurements, demonstrates that TAS analysis of the excited state dynamics in graphene might lead to the creation of effective methodology of control of quality of graphene in terms of effective defect analysis.

Contactless probing of graphene charge density variation in a controlled humidity environment

The electronic properties of graphene are highly sensitive to atoms and molecules adsorbed on its surface and to changes in its environment, such as temperature and humidity. In this paper, we examine the effect of humidity on the local carrier concentration of different types of graphene prepared by mechanical exfoliation, chemical vapour deposition and epitaxial growth on SiC, using in-situ Raman spectroscopy. We present a systematic and comparative study of the changes in Raman response using a vector analysis method to produce spatial maps of doping variation as a function of humidity. We also quantify the humidity induced carrier concentration change for different types of graphene. This study illustrates the effects of humidity on the electronic properties of graphene and provides a simple, contactless and quantitative method to directly evaluate water-induced doping effects in graphene, that are crucial for tailored device performance.

A comparative investigation of aminosilane/ethylene diamine–functionalized graphene epoxy nanocomposites with commercial and chemically reduced graphene: static and dynamic mechanical properties

Incorporation of nanosized fillers into polymers has created new composites by expanding the functions and applications while retaining the excellent engineering and processing flexibility inherent to polymers. Compared with traditional nanofillers, more recently, graphene has been increasingly preferred as a candidate for strengthening and/or functionalizing polymer nanocomposites. The easy synthetic methods, low cost, and non-toxicity of graphene make this material attractive for many technological applications. Herein, we discuss the synthesis of different types of graphene from graphite via graphene oxide reduction. Commercial graphene (CG) as well as the synthesized chemically reduced graphene (CRG) and chemically reduced silane-modified graphene (SMG) were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and ultraviolet visible (UV-vis) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies. The results confirmed that the silane molecules were attached on the surface of graphene sheets. Simultaneously, most of residual oxygen-containing functional groups of GO were reduced and the sp2-hybridized structure of graphene was restored. The utilization of these graphene-based materials in the fabrication of epoxy nanocomposites with enhanced properties has been explored and compared with those of neat epoxy and CG/epoxy nanocomposites. Inclusion of 0.25 phr CRG and SMG in an epoxy resin showed 28% and 32% increases in tensile strength, and the corresponding fracture toughness displayed 67.6% and 66.3% increase respectively. The improved mechanical properties of SMG/epoxy nanocomposites might be due to the uniform dispersion of functionalized graphene and strong interfacial bonding between modified graphene and epoxy resin.

The impact of graphene nanoparticle additives on the strength of simple and hybrid adhesively bonded joints

In this paper, the effect of graphene nanoparticle additive on the strength of simple and hybrid (rivet-bonded) single-lap joints is studied using the experimental method. Two different types of graphene with different number of layer and thicknesses are used in adhesive-graphene nanoparticle composite construction. At first, tensile tests are done on bulk specimens of adhesive with different additives. It is found that adding 0.5 wt% of graphene to the neat adhesive leads to an increase in the ultimate tensile strength of bulk specimens almost 24% and 12% for two graphene types compared to the neat adhesive. Also, the shear strength of adhesive and hybrid lap joints incorporating two types of graphene nanoparticles (types I and II) is compared to that of adhesive and hybrid joints without graphene nanoparticles. SEM results of fracture surfaces show that the inclusion of graphene nanoparticle to the adhesive increases the roughness of surfaces. Experimental results reveal that graphene nanoparticle increases the strength of bonded and hybrid joints. It is observed that, graphene with a lower thickness and number of layers has a better influence on joint strength. In fact, graphene nanoparticle type II makes a homogeneous distribution in adhesive-graphene nanoparticle composite and causes a significant increase on joint strength.

Comparative study on the antioxidation behaviors of polycrystalline multilayer and single-crystalline monolayer graphene

Graphene is known effective as a short-term solution to protecting metals from oxidation. Past studies have shown that more layers and fewer defects (e.g. grain boundaries) enhance the antioxidation ability of graphene. However, it has remained unanswered which of these two parameters, namely, number of graphene layers and crystallinity of graphene, is more important when it comes to protecting metals. Herein, we aim to study this subject by comparing the oxidation behaviors of Cu covered by two different types of graphene. One is multilayered but contains a high density of grain boundaries, while the other is free of grain boundaries but comes with only one layer. Through oxidizing experiments in air and water-rich vapor conditions, failure mechanisms of graphene and change of underlying Cu (and Cu oxides) are thoroughly investigated using a wide range of analytical tools, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS). It is found that the single-crystalline, monolayer graphene is more effective than the counterpart in polycrystalline, multilayer format for protecting Cu against oxidation in both air and water-rich vapor conditions. Especially in air oxidizing case, the former graphene raises the temperature barrier by at least 100 °C as compared to the latter graphene. Our results therefore suggest that the crystallinity of graphene deserves more considerations when using graphene as the antioxidizing barrier.

Strengthening effects of encapsulating graphene in SiC particle-reinforced Al-matrix composites

This work aims to reveal the strengthening effects of encapsulating graphene in the tensile strength of SiC particulate Al-based composites. Modified theoretical models are discussed regarding the thermal mismatch, Orowan and fine-grain strengthening mechanisms. It is found that the thermal mismatch strengthening is the dominant mechanism among them, followed by the Orowan strengthening and the fine-grain strengthening to be the last. While comparing the effects of two different types of graphene, we find that sheet graphene makes more strengthening contributions to both thermal mismatch and Orowan strengthening mechanisms compared with encapsulating graphene. Finite element simulations are employed to investigate the variation patterns of these effects with varies particle sizes and volume fractions. A better enhancing effect of encapsulating graphene can be achieved with a larger volume fraction and a smaller particle size.

The Influence of Different Types of Graphene on the Lithium Titanate Anode Materials of a Lithium Ion Battery

Graphene is widely studied in various fields, due to its high electrical conductivity and thermal conductivity, as well as its large theoretical surface area. Graphene is used in batteries to improve the electronic conductivity of the material and to reduce the volume effect that the electrode material has during the charging and the discharging process. The graphene nanosheets (GNS) and the electrochemical properties of the composite of battery electrode material differ, due to the different preparation methods used for commercial GNS. Two types of commercial GNS were evaluated via XRD, Raman spectra, and HR-TEM. Li4Ti5O12/graphene nanosheet (LTO/GNS) composites were obtained with a sol-hydrothermal process with in situ additions of GNS. Both the LTO/GNS composites showed the same microstructure. The GNS in the composites provided conductive connections for LTO to establish a conductive network. The effect that GNS with low structural defects had on improving the electrical conductivity of the LTO/GNS was better than the GNS with additional structural defects. The LTO/GNS (with low structural defects) exhibited superior electrochemical performance than the LTO/GNS (with additional structural defects). Moreover, the LTO/GNS samples with additional structural defects obtained a lower specific capacity than the pure LTO samples, in terms of the rate performance measurements. The possible causes were analyzed throughout this study.

Ice Nucleation Activity of Graphene and Graphene Oxides.

Aerosols can act as cloud condensation nuclei and/or ice-nucleating particles (INPs), influencing cloud properties. In particular, INPs show a variety of different and complex mechanisms when interacting with water during the freezing process. To gain a fundamental understanding of the heterogeneous freezing mechanisms, studies with proxies for atmospheric INPs must be performed. Graphene and its derivatives offer suitable model systems for soot particles, which are ubiquitous aerosols in the atmosphere. In this work, we present an investigation of the ice nucleation activity (INA) of different types of graphene and graphene oxides. Immersion droplet freezing experiments as well as additional analytical analyses, such as X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy, were performed. We show within a group of samples that a highly ordered graphene lattice (Raman G band intensity >50%) can support ice nucleation more effectively than a lowly ordered graphene lattice (Raman G band intensity <20%). Ammonia-functionalized graphene revealed the highest INA of all samples. Atmospheric ammonia is known to play a primary role in the formation of secondary particulate matter, forming ammonium-containing aerosols. The influence of functionalization on interactions between the particle interface and water molecules, as well as on hydrophobicity and agglomeration processes, is discussed.

A Multiscale Morphological Insight into Graphene Based Coatings for Pool Boiling Applications

ABSTRACTThe application of graphene for pool boiling is an attractive option to facilitate compaction and promote efficient heat removal from high power density devices. In this context, chemical characterization of the depositions achieved through commonly employed coating techniques are an important topic of discussion. A detailed structure-property relationship between the morphologies obtained on the mono and multilayered graphene coatings and their corresponding pool boiling performance quantified by the experimental critical heat fluxes is presented. Three different types of graphene (G) and graphene oxide (GO) substrates are characterized: (i) nanoscale: mono and multilayer samples developed through chemical vapor deposition, (ii) Rochester Institute of Technology (RIT)-G/GO colloid generated through an oxygen embrittlement electrochemical process, and (iii) commercially available chemical vapor deposited (CVD)-G/GO colloid. The morphological features were characterized with scanning electron microscope while X-Ray Diffractometer analysis and Raman spectroscopy were used to examine the ordering and stacking of the sheets that result in the unique structural features. Fourier transform infrared and energy dispersive X-ray spectroscopy were employed to identify the overall compositional characteristics of the coated surfaces. The wettability changes and additional nucleation sites for nanoscale coatings, and multiscale roughness features and ridge microstructures for microscale coatings were identified as enhancement mechanisms.

Towards conductive textiles: coating polymeric fibres with graphene

Conducting fibres are essential to the development of e-textiles. We demonstrate a method to make common insulating textile fibres conductive, by coating them with graphene. The resulting fibres display sheet resistance values as low as 600 Ωsq−1, demonstrating that the high conductivity of graphene is not lost when transferred to textile fibres. An extensive microscopic study of the surface of graphene-coated fibres is presented. We show that this method can be employed to textile fibres of different materials, sizes and shapes, and to different types of graphene. These graphene-based conductive fibres can be used as a platform to build integrated electronic devices directly in textiles.

Comparison of Photocatalytic Performance of Different Types of Graphene in Fe3O4/SnO2 Composites

We have reported the role of annealing temperature Fe3O4/SnO2 nanocomposites as a photocatalyst for remove methylene blue (MB) dye from aqueous solution. However, how to enhanced the degradation performance of Fe3O4/SnO2 nanocomposites is important to its photocatalytic application. Therefore, in this work Fe3O4/SnO2 nanocomposites was combined with two different types of graphene materials (NGP and grahene) to improve the photocatalytic performance for remove methylene blue (MB) dye. Fe3O4/SnO2/NGP and Fe3O4/SnO2/graphene have been successfully synthesized by co-precipitation method. The influence of two types graphene on Fe3O4/SnO2 nanocomposites properties were systematically investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Thermal gravimetric analysis (TGA). Degradation of methylene Blue (MB) in aqueous solution was studied in detail under photocatalytic process. Effect of catalyst dosage (0.1-0.4 g/L) and scavengers on dye degradation were carried out to check the efficiency of photocatalyst. The results indicated Fe3O4/SnO2/graphene displayed higher photocatalytic activity than other catalyst. The reusability tests have also been done to ensure the stability of the used photocatalyst.

Multifunctional Photocatalytic Degradation of Methylene Blue Using LaMnO3/Fe3O4 Nanocomposite on Different Types of Graphene

This study added different types of graphene (GN-1 and GN-2) in to LaMnO3/Fe3O4 nanocomposite to degrade MB as an organic pollutant. LaMnO3/Fe3O4/GN-1 and LaMnO3/Fe3O4/GN-2 composites were synthesized using the co-precipitation method in a constant 5 wt% of GN. The as-prepared samples were characterized using XRD and TGA. The LaMnO3/Fe3O4/GN-1 and LaMnO3/Fe3O4/GN-2 composites showed the orthorhombic structure of LaMnO3 nanoparticles and the cubic spinel of Fe3O4 nanoparticles, as well as of GN-1 and GN-2. The graphite structure of NGP in LaMnO3/Fe3O4/GN-1 composites was confirmed. However, the peak of graphene in LaMnO3/Fe3O4/GN-2 could not be identified. The photocatalytic efficiency of the LaMnO3/Fe3O4/GN-2 was higher than that of LaMnO3/Fe3O4/GN-1. The enhancement of the photocatalytic light activity can be attributed to the high separation efficiency of electron-hole recombination and to the large surface contact between LaMnO3/Fe3O4 and graphene, which can improve the transfer efficiency of the photocatalytic process. In addition, the effects of catalyst dosage, rate constant, and scavengers were investigated and discussed.

Synthesis of Different Layers of Graphene on Stainless Steel Using the CVD Method.

In this study, different types of graphene, including single-, few-, and multi-layer graphene, were grown on a stainless steel (SS) mesh coated with Cu catalyst by using the chemical vapor deposition (CVD) method. Even though the SS mesh consisted of different types of metals, such as Fe, Ni, and Cr, which can also be used as catalysts, the reason for coating Cu catalyst on the SS surface had been related to the nature of the Cu, which promotes the growth of graphene with high quality and quantity at low temperature and time. The reaction temperature and run time, as the most important parameters of the CVD method, were varied, and thus led to the synthesis of different layers of graphene. Moreover, the presence of single-, few-, and multi-layer graphene was confirmed by employing two techniques, namely transmission electron microscopy (TEM) and Raman spectroscopy. On top of that, electron dispersive X-ray (EDX) was further applied to establish the influence of the CVD parameters on the growth of graphene.