Multilayer Graphene Research Articles

Enhanced physical and mechanical properties of Cu-based nanocomposites with bundled multi-layered carbon nanotubes incorporation: fabrication and comparative analysis via conventional sintering and SPS techniques

The current investigation delves into the influence of incorporating bundled multi-layered graphene sheets, specifically multiwalled carbon nanotubes (MWCNTs), on the microstructure, as well as the physical and mechanical attributes of Cu-based nanocomposites. Various weight percentages (1%, 2%, 3%, and 5%) of MWCNTs were infused into the Cu matrix, and the fabrication of these nanocomposites was conducted through the powder technology route. The fabrication process occurred under an argon atmosphere utilizing both conventional sintering and spark plasma sintering (SPS) techniques. The conventionally sintered Cu-based nanocomposite reinforced with 1% MWCNT exhibited the highest relative density (~86%), hardness (~551.12 MPa), compressive strength (~459 MPa), and outstanding resistance to wear. Conversely, the SPS-fabricated nanocomposite reinforced with the same MWCNT concentration demonstrated the highest relative density (approximately 94.25%) and compressive strength (~688 MPa), while the nanocomposite reinforced with 2% MWCNT displayed the highest hardness (~1178 MPa) and resistance to wear. Notably, a higher concentration of MWCNTs was observed to adversely affect the physical, mechanical, and wear properties of the Cu-MWCNT nanocomposites, irrespective of the chosen sintering technique for their production.

Loss-Assisted Anomalous Hong-Ou-Mandel Interference Based on Nonunitary Multilayer Graphene.

Hong-Ou-Mandel interference is an intrinsic quantum phenomenon that goes beyond the possibilities of classical physics, and enables numerous applications in quantum information science. While the photon-photon interaction is fundamentally limited to the bosonic nature of photons and the restricted phase responses from commonly used unitary optical elements, we present that a nonunitary material provides an alternative degree of freedom to control the two-photon quantum interference, even revealing anomalous quantum interference paths that do not exist in a unitary configuration. An elaborate lossy multilayer graphene that can work as a nonunitary beam splitter is used to explore its tunability over the effective photon-photon interaction in spatial modes, and to verify the particle exchange statistics by its experimental implementation in quantum state filter. This scheme is further extended to observe four-dimensional quantum interference patterns on the lossless and lossy beam splitters, and thus show its applicability even in higher-dimensional Hilbert space.

An Experimental Study on Electromagnetic Shielding Effectiveness and Impact Resistance of UHPC for Protective Facilities

The research was conducted on incorporating short carbon fiber and multi-layer graphene into ultra-high performance concrete (UHPC) to improve the dynamic mechanical performance and electromagnetic shielding effectiveness (SE). In the electromagnetic shielding effectiveness testing, the results shown that UHPC with uniformly distributed conductive fibers exhibited superior shielding effectiveness at high frequencies. In comparison to normal concrete, the UHPC demonstrated the capability to withstand higher impact energy. Simultaneously enhancing both electromagnetic shielding characteristics and dynamic mechanical performance of cementitious materials can be challenging. In this study, employing a composite structure was effective solution to overcome this issue. In accordance with the experimental results, a scaled testing protective facility has been constructed, and the research results could provide the reference for the design and construction of protective structures.

Self-sensing performance of concrete columns using Multi-layer Graphene filled cement-based sensors with different arrangements

The Multi-layer Graphene (MLGs) filled cement-based sensor (GCBS) was developed and applied in the concrete columns. The strain-sensing performance of GCBS was investigated under cyclic and monotonic loading after being embedded in the column. Meanwhile, the influence of embedded location and adjacent sensor distance on the piezoresistive performance of the sensor was discussed. The strain measured by the embedded sensor agreed well with that obtained by LVDTs within the elastic regime. However, the embedded sensor underestimated the concrete strain after stepping into the plastic stage because of the increasing transverse deformation coefficient. Moreover, improper arrangement of the sensor resulted in uneven deformation, generating significant strain differences between the sensor with concrete and increasing prediction deviation. To guarantee the predicting accuracy of the sensor, it is recommended that the embedded position of the sensor from the superficial layer of the column should exceed 25 mm, and the distance between adjacent sensors should not be lower than 107.24 mm.

Comprehensive electrochemical imaging analyses of redox activities correlated to multilayer graphene and graphite structures

The utilization of two-dimensional (2D) materials within electrochemical devices constitutes a pivotal area of investigation, particularly pertinent to energy-related materials. Scanning electrochemical cell microscopy (SECCM) stands as a valuable characterization tool for the in-situ visualization of electrochemical processes transpiring within nanoscale structures. In the context of this investigation, SECCM was employed to scrutinize the influence of atomic structures in multilayer graphene and graphite samples, emblematic of 2D materials, upon a spectrum of electrochemical reactions, encompassing redox reactions of Ru(NH3)63+/2+. By visualizing and locally evaluating electrochemical reactions with various atomic structures, this research can be applied to design materials to promote more electrochemical reactions, as well as to other electrochemical energy devices (such as lithium-ion batteries and electrocatalysts). Furthermore, it extends its purview to assess the applicability of graphene substrates as platforms for the evaluation of other two-dimensional materials.

Simultaneous removal of 2,4-DCP and Cr(VI) in water by gBC@nZVI: Cr(V) mediated ROS formation

In the actual polluted environment, the composite pollution system was usually composed of heavy metals and organic pollutants, especially Cr(VI) and chlorophenols often co-existed in industrial wastewater. In this study, a composite material consisting of multilayer graphene carbon shells coated with nZVI (gBC@nZVI) with various excellent properties was applied to deal with the composite system of Cr(VI) and 2,4-dichlorophenol (2,4-DCP) coexisting in the wastewater, and the intrinsic mechanism for the simultaneous removal of heavy metals and organic pollutants was systematically investigated. The results showed that in the composite pollution system (Cr(VI) = 20 mg/L, 2,4-DCP = 15 mg/L), complete removal of Cr(VI) could be achieved in 60 min, while 2,4-DCP achieved 95.2 % removal, with the contribution of oxidative degradation being 76.4 %. It was found that during the efficient adsorption and reduction of Cr(VI) by gBC@nZVI, the generation of the metastable intermediate Cr(V) was verified by probe compounds, electron spin resonance and UV–visible spectroscopy, and further experiments demonstrated that the generation of •OH was closely related to Cr(V) and promoted the oxidative degradation of the coexisting 2,4-DCP. Quenching experiments with the addition of specific scavengers indicated that •OH was the active species directly dominating the oxidative degradation of 2,4-DCP, whereas Cr(V) was indirectly involved in the degradation of 2,4-DCP by promoting the generation of •OH. In addition, the increase of solution pH negatively affected the degradation of 2,4-DCP in the composite polluted system, mainly due to the hindered generation of •OH in the alkaline environment. This work provided theoretical support for the promising application of gBC@nZVI in real environments contaminated with a combination of Cr(VI) and chlorophenols.

Investigation of thermal conductivity and mechanical properties in multi-layer of graphene and graphene oxide: a molecular dynamics study

ABSTRACT Multi-layered graphene and graphene oxide have been used as reinforcements in nanodevices and nanocomposites due to their extraordinary mechanical and thermal properties. However, compared to graphene, graphene oxide has a lower Young’s modulus and lower thermal conductivity. Nanodevices and nanocomposites based on multi-layered graphene and graphene oxide require different mechanical properties and thermal conductivity. This study employed molecular dynamics simulation to investigate 10 models of multi-layered graphene and graphene oxide (in the form of different layer arrangements) in single, double, and triple layers. The results showed that an increase in the number of graphene oxide layers leads to irregularities in the nanosheets, resulting in decreased thermal conductivity (by 64.4%) of the nanosheets decreases. Furthermore, the greater number of graphene layers in multi-layer nanosheets resulted in an increase in Young’s modulus (by 79.3%) and tensile strength (by 73.7%). Moreover, the arrangement of graphene and graphene oxide is a crucial factor that can significantly impact the mechanical properties and thermal conductivity of the models. Moreover, an increase in temperature can lead to a decrease in Young’s modulus of multilayered nanosheets. Increasing the number and size of graphene layers enhances both the ultimate tensile strength and the critical energy release rate.

Quarter-metal phases in multilayer graphene: Ising-XY and annular Lifshitz transitions

Quarter-metal phases in multilayer graphene: Ising-XY and annular Lifshitz transitions

Design and preparation of multiple, multidimensional and multiscale Ni/GC/CNTs/MLGs toughened phases

We introduce a novel methodology for fabricating multiple, multidimensional and multiscale toughened phases, utilizing resin as a binder in traditional ceramic green body. This approach involves exfoliating expanded graphite (EG) mixed in phenolic resin (PF) using three-roll milling (TRM), coupled with the pyrolysis of PF catalyzed by Ni(NO3)2. The effects of catalyst contents and heat-treated temperatures on the phase composition, morphology and microstructure of the resulted products were investigated. An in-situ growth mechanism of CNTs from PF catalyzed by Ni(NO3)2 was proposed. The findings revealed the successful derivation of zero-dimensional (0D) glassy carbon (GC) and 1D CNTs from PF pyrolysis, catalyzed by 0D Ni nanoparticles from Ni(NO3)2 via a vapor-solid mechanism. The 2D multilayer graphenes (MLGs) were effectively produced by exfoliating EG through TRM. We proposed two distinct pathways for integrating multiple Ni/GC/CNTs/MLGs toughened phases with different dimensions and scales into ceramic matrices, potentially enabling synergistic interactions for futural toughening ceramic.

Polyamorphism gets a magnetic boost

Four decades since the concept of polyamorphism was introduced by [L. S. Palatnik (1909–1994), Fiz. Nizk. Temp. 25, 400 (1909)], numerous investigations proved its presence in a broad variety of nonmagnetic short-range ordered materials, like structural, metallic, a-metallic, inorganic molecule, orientational, electron glasses, water, ice, carbons, and others. It was manifested by phase transitions between amorphous states as a function of the quench condition and under compression, mediated by long-wave fluctuations of an order parameter. There has been much recent discussion given to the phenomenon of polyamorphism where distinct, different states of amorphous liquids and solids are observed as a function of density. The outstanding contribution of the recently late [A. Sella, et al. (1956–2022), Nat. Mater. 21, 490 (2022)],2 in the field should be recognized here. Underlying this phenomenon is the possibility of a first-order liquid-liquid phase transition driven by the density and entropy differences between the two amorphous phases. Magnetic boost of multilayer graphene under pressure was also recently discovered. Their famous spin counterparts, such as spin liquid, spin ice, and spin glass have been less studied at this end despite numerous similarities, registered so far. Taking that in mind, for further polyamorphism platform development, we demonstrate the signatures of phase transition in spin glass, driven by a magnetic field, and eventually, a novel type of polyamorphism, the spin-glass one.

Improved strength-plasticity-conductivity of graphene/copper layered composites by vacuum hot rolling

The method used to strengthen copper matrix composites generally results in a significant decrease in ductility and electrical conductivity. In this work, multilayer graphene was grown on both sides of copper foil using chemical vapor deposition process and graphene/copper layered composites were prepared by stacking copper foils and hot rolling under vacuum. The microstructures, mechanical properties and electrical conductivity of hot rolled graphene/copper layered composites with different reduction amounts were investigated. Results showed that the grain size increased while the dislocation density did not change much with the reduction amounts from 30% to 50%. The size of graphene decreased and the spacing of graphene increased with the reduction amounts. When the reduction amounts increased from 30% to 50%, the tensile strength decreased from 223 MPa to 163 MPa, the elongation decreased from 45% to 31% and the electrical conductivity decreased from 101.52 %IACS to 89.73 %IACS. The optimized combination of properties was obtained when the hot rolled reduction amount was set as 30% because of the grain refining and the change in graphene size and spacing. Combining the analysis of microstructures and properties of the unreinforced copper matrix at 30% reduction amount, it can be concluded that the tensile strength of the composite increased from 179 MPa to 223 MPa, elongation increased from 38% to 45% and electrical conductivity increased from 98.02 %IACS to 101.52 %IACS. Long and distributed continuously graphene were beneficial to the improvement of strength, elongation and electrical conductivity by playing an obvious role in the load transfer strengthening mechanism, refining the grain size of the composites, and preventing the crack propagation.

Surface modification of mild steel to circumvent challenges in chemical vapour deposition of graphene coating for durable corrosion resistance

Graphene possesses unique combination of characteristics (i.e., inertness, impermeability and toughness) to qualify as ideal coating material for corrosion resistance, and graphene coatings on nickel and copper have been shown to provide excellent and durable corrosion resistances. However, growing graphene directly on mild steel by chemical vapour deposition (CVD), is prohibitively challenging due to high solubility of carbon in mild steel at high temperatures. The non-trivial challenge was circumvented through surface modification of steel by electroplating with Cu and Ni, accounting for the critical consideration, i.e., the inter-diffusivity of iron in nickel or copper. However, the key finding was that the undesirably high thicknesses of the electroplated Cu and Ni layers were detrimental, and optimization of their thicknesses was essential for successful deposition of the required quality graphene. The optimised thicknesses were derived on the basis of the fundamental diffusion calculations. The uniform multi-layered graphene coating on the suitably modified mild steel surface provided remarkable corrosion resistance in an aqueous chloride solution, and electrochemically validation of the corrosion durability for extended exposure (>1000 h) was characterised.

Simultaneous analysis of chloramphenicol, amoxicillin, and enrofloxacin using electrochemical sensors with multilayer graphene electrodes fabricated by electrochemical methods in an organic solvent

In this study, three antibiotics, chloramphenicol (CAP), amoxicillin (AMX), and enrofloxacin (ENR), were simultaneously analysed for the first time using electrochemical sensors. The multilayer graphene electrode used in the sensor was directly and rapidly fabricated from graphite through a one-step chronoamperometry method. Scanning electron microscopy and cyclic voltammetry techniques revealed the multilayer-graphene nanostructure of the prepared electrode with a large electrochemically active surface area and good electrochemical activity. The electrode exhibited the best electrochemical oxidation signals corresponding to the three antibiotics when fabricated at a potential of 5 V for 20 s. Under optimised conditions, the sensor demonstrated excellent multi-analyte analysis capability, with clear separation and good linearity of the signals of the three antibiotics (R2>0.99) in relation to their concentrations. The sensor exhibited high accuracy and sensitivity with detection limits of 0.060, 0.381, and 0.109 μM for CAP, AMX, and ENR, respectively. The applicability of the sensor was demonstrated through acceptable recoveries of all three antibiotics when simultaneously analysed in a lake water sample.

Selective removal of single-layer graphene over double-layer graphene on SiO2 by remote oxygen plasma irradiation

Graphene sheet transferred onto the SiO2 substrate has various types at different regions such as single-layer graphene (SLG), double-layer graphene (DLG), and multi-layer graphene (MLG). These layers were identified by Raman analysis of 2D band position around 2700 cm−1 and full width at half maximum (FWHM). The transferred graphene sheets on SiO2 were remotely irradiated by oxygen plasma without energetic ions at a room temperature. At the beginning of the oxygen plasma irradiation, the carbons on the surface of the graphene sheets were oxidized and the 2D-FWHMs were broadened due to an increase of defects on the basal plane. By controlling the plasma irradiation time up to 120 min, selectively stripping away the SLG regions on the SiO2 surface was observed while leaving the other DLG and MLG regions. The difference in attractive forces resulted in favorable desorption of carbon atoms occurred in the oxidized SLG regions on SiO2 surface by the remote oxygen plasma irradiation.

A robust method for assessing the macroscale tribological behaviour of solid lubricant nanoparticles

Reducing friction and wear is crucial for efficiency and longevity in tribological systems. Solid lubricant nanoparticles show great potential in this context but lack deposition control methods and tribological performance investigations under conditions closer to real systems. The present study used drop-casting to deposit multi-layer graphene (MLG) and carbide-derived carbon (CDC) nanoparticles on AISI1020 steel substrates. Tribological performance was evaluated using a ball on flat tests with an incremental load increase in a reciprocating motion. Results indicate a minimum coverage threshold for effective lubrication and highlight substrate topography's critical role. This research enhances understanding of nanoparticle deposition process optimization and control, showing an excellent tribological performance of MLG and CDC nanoparticles in solid lubricated systems.

Pb(II) Adsorption Properties of a Three-Dimensional Porous Bacterial Cellulose/Graphene Oxide Composite Hydrogel Subjected to Ultrasonic Treatment.

A three-dimensional porous bacterial cellulose/graphene oxide (BC/GO) composite hydrogel (BC/GO) was synthesized with multi-layer graphene oxide (GO) as the modifier and bacterial cellulose as the skeleton via an ultrasonic shaking process to absorb lead ions effectively. The characteristics of BC/GO were investigated through TEM, SEM, FT-IR, NMR and Zeta potential experiments. Compared to bacterial cellulose, the ultrasonic method and the carboxyl groups stemming from GO helped to enhance the availability of O(3)H of BC, in addition to the looser three-dimensional structure and enriched oxygen-containing groups, leading to a significantly higher adsorption capacity for Pb(II). In this paper, the adsorption behavior of BC/GO is influenced by the GO concentration, adsorption time, and initial concentration. The highest adsorption capacity for Pb(II) on BC/GO found in this study was 224.5 mg/g. The findings implied that the pseudo-second-order model explained the BC/GO adsorption dynamics and that the data of its adsorption isotherm fit the Freundlich model. Because of the looser three-dimensional structure, the complexation of carboxyl groups, and the enhanced availability of O(3)H, bacterial cellulose exhibited a much better adsorption capacity.

An ultra-wideband magnetic composite metamaterial microwave absorber embedded with multilayered graphene FSS

Nowadays, it is still challenging to develop high-efficiency broadband microwave absorption materials for electronic equipment and communication facilities. Herein, an ultra-wideband metamaterial microwave absorber (MMA) composed of CoNi@CNH/epoxy composite absorption substrates and the multilayered graphene frequency selective surface (FSS) is designed and fabricated. Thanks to the effective synergies of the multilayered graphene FSS with impressive tunable frequency features and magnetic absorption substrates with distinguished broadband absorption capacity, the obtained MMA showcases an effective absorption bandwidth from 4.5 GHz to 18 GHz. Meanwhile, an equivalent circuit model is proposed to explain its physical absorption mechanism. The designed MMA exhibits the insensitivity to both polarization modes and oblique incidences, and a significant radar cross-section reduction. The experimental results of the as-fabricated sample match well with the simulation values. Furthermore, the as-designed MMA possesses a simple fabrication process and an ultralight feature of 2.7 kg/m2. All these excellent properties make this MMA a high application prospect in both military stealth and civil fields.

Multi-channel switch and sensing applications based on multilayered annular graphene metamaterials at terahertz frequency

In this study, a novel silica-graphene–silica periodic graphene structure consisting of six graphene semi-rings is proposed. The structure is based on a three-layer graphene metamaterial with a semicircular ring that achieves a tunable double plasmon-induced transparency (PIT) effect. In the proposed structure, the double-PIT window can be switched simultaneously at multiple frequencies through the dynamic tunability of graphene. Besides, the sensitivities of the refractive index for the PIT windows are investigated with the maximum values of 1.42 THz RIU−1 and 1.09 THz RIU−1, respectively, indicating the structure’s performance as a terahertz sensor. Overall, it shows the potential of PIT effect in graphene metamaterials in controlling electromagnetic field responses. It has made positive contributions to the development of terahertz technology and related fields.

Evolution of the Surface Wettability of Vertically Oriented Multilayer Graphene Sheets Deposited by Plasma Technology.

Carbon deposits consisting of vertically oriented multilayer graphene sheets on metallic foils represent an interesting alternative to activated carbon in electrical and electrochemical devices such as super-capacitors because of the superior electrical conductivity of graphene and huge surface-mass ratio. The graphene sheets were deposited on cobalt foils by plasma-enhanced chemical vapor deposition using propane as the carbon precursor. Plasma was sustained by an inductively coupled radiofrequency discharge in the H mode at a power of 500 W and a propane pressure of 17 Pa. The precursor effectively dissociated in plasma conditions and enabled the growth of porous films consisting of multilayer graphene sheets. The deposition rate varied with time and peaked at 100 nm/s. The evolution of surface wettability was determined by the sessile drop method. The untreated substrates were moderately hydrophobic at a water contact angle of about 110°. The contact angle dropped to about 50° after plasma treatment for less than a second and increased monotonously thereafter. The maximal contact angle of 130° appeared at a treatment time of about 30 s. Thereafter, it slowly decreased, with a prolonged deposition time. The evolution of the wettability was explained by surface composition and morphology. A brief treatment with oxygen plasma enabled a super-hydrophilic surface finish of the films consisting of multilayer graphene sheets.

High-quality lateral monolayer-multilayer graphene junction formed by selective laser thinning for self-powered photodetection

The formation of an asymmetric junction is key to graphene-based photodetectors of high-sensitive photodetectability, because such a junction can not only facilitate the diffusion or drift of photogenerated carriers but also realize a self-powered operation. Here, a monolayer-multilayer graphene junction photodetector is accomplished by selectively thinning part of a multilayer graphene to a high-quality monolayer. Benefiting from the large photoabsorption cross section of multilayer graphene and strong asymmetry caused by the significant differences in optoelectronic properties between monolayer and multilayer graphene, the monolayer-multilayer graphene junction shows a 7-fold increase in short-circuit photocurrent as compared with that at the monolayer graphene-metal contact in scanning photocurrent images. The asymmetric configuration also enables the photodetector to work at zero bias with minimized dark current noise and stand-by power consumption. Under global illumination with visible light, a photoswitching ratio of 3.4 × 103, a responsivity of 8.8 mA W−1, a specific detectivity of 1.3 × 108 Jones and a response time of 11 ns can be obtained, suggesting a promising photoresponse. Moreover, it is worth mentioning that such a performance enhancement is achieved without compromising the broadband spectral response of graphene photodetector and it is hence applicable for long wavelength spectral range including infrared and terahertz.