Graphene Coatings Research Articles

On the Distinctive Hardness, Anti-Corrosion Properties and Mechanisms of Flame-Deposited Carbon Coating with a Hierarchical Structure in Contrast to a Graphene Layer via Chemical Vapor Deposition.

Two carbonaceous (amorphous carbon and graphene) coatings were catalytically grown on bulk Ni plates. It was found that the flame-deposited carbon (FDC) layers exhibited a unique hierarchical structure with the formation of FDC/Ni nano-interlocking interface. The effect of the flame coating time on its corrosion protective efficiency (PE) was studied and compared with that of graphene coating produced via chemical vapor deposition. The FDC grown for 10 min exhibited a PE of 92.7%, which was much greater than that of the graphene coating (75.6%). The anti-corrosive mechanisms of both coatings were revealed and compared. For graphene coatings, the higher reaction temperature than that for FDC resulted in large grain boundaries inherent in the coating. Such boundaries were weak points and easily initiated grain boundary corrosion. In contrast, corrosion started at only certain local defects in FDC layers, whose unique interface structure likely promoted its PE as well. Moreover, after the coating process, the hardness of FDC-coated Ni remained almost unchanged, in contrast to that of graphene-coated samples (reduced by ~30%). This is suggested to be related to the crystal structure evolution of the Ni substrate caused by the heat treatment accompanying the coating process.

Graphene, phosphorene and silicene coatings on the (0001) surfaces of hcp metals: Structural stability and hydrophobicity

Single atomic layer or monolayer (ML) 2D materials have unique features that can be relevant for protection and functionalization of high-performance surfaces. Here we report a combined density functional theory and ab initio molecular dynamics study on the stability of graphene (Gr), phosphorene (Pp) and silicene (Sl) coatings at the most stable (0001) surface of the metals that have hcp structure at room temperature: Hf, Mg, Os, Re, Ru, Sc, Ti, Zn and Zr. We found that the three 2D materials are stable at the surfaces of many of these metals: Gr is stable at Os, Re, Ti, Zn and Zr; Pp is stable in the blue form at Hf, Mg, Ti and Zr; Sl is stable in the 2D zigzag structure at Hf, Mg and Ti and in the planar form at the Zr surface. For the remaining metals Gr, Pp and Sl do not form van der Waals bonded MLs. In those cases we found structures such as 2D arrangements of mixed hexagons and pentagons, trigonal pyramidal structures and 2 half-monolayers. Many of these structures are very stable coatings covalently bound to the surfaces with considerable adsorption energies that can reach − 2 eV per atom of the coating. Gr imparts hydrophobicity to the surfaces of all materials here studied and increases the distance between these and the first H2O layer by as much as 75 % for Gr coated Ti. These H2O layers have increased rigidity despite being located further apart from the surfaces. These effects could be explored for the protection or functionalization of high-performance systems such as metallic electrodes for example.

Graphene-Dominated Hybrid Coatings with Highly Compacted Structure on Stainless Steel Bipolar Plates.

Highly conductive corrosion protection coatings are necessary for metallic bipolar plates (BPs) of the proton-exchange membrane fuel cell. Graphene coatings have the potential of protecting metal substrates from corrosion without obscuring their excellent electrical conductivity. The electron transfer in the coatings facilitates the formation of galvanic cells, so the challenge is to block the mass transfer of the corrosion process. Here, we constructed highly compacted hybrid coatings with aligned water-dispersible graphene layers. The water-dispersible graphene (SG) held an electrical conductivity of >270 S cm-1 while providing an unprecedented dispersibility, which can be redispersed from filter cake with a concentration of 120 mg mL-1 or even dry state. The cohesion of the hybrid coatings was attributed to the interaction between highly aligned SG layers and the heterointerface between SG and polydopamine (PDA), as proven by the molecular dynamics simulations. The hybrid coatings presented a corrosion current density of 0.023 μA cm-2 and an interfacial contact resistance of 9.94 mΩ cm2, which meets the requirements of corrosion protection and electron transfer for the coatings on metallic BPs. The water-based fabrication method of the graphene-dominated hybrid coatings was a promising alternative of the vacuum-based deposition method for industrial production.

Graphene and Resin Coated Proppant with Electrically Conductive Properties for In-Situ Modification of Shale Oil

Proppant is an essential material in hydraulic fracturing, and it can support artificial fractures for a long time. However, few people have applied proppant and conductive materials in the in-situ modification of shale oil. Here, we developed a graphene and resin coated (GRC) proppant with electrically conductive properties. The electrical conductivity of the GRC proppant improved by four orders of magnitude. The GRC proppant has a 54.58% improvement in suspension and 22.75% increase in settlement time at 0.25 wt% concentration compared with uncoated proppant. The GRC proppant’s adhesion reached 68.34 nN under 1 μN load force, increasing by 63.13% compared to uncoated proppant. This new electrically conductive proppant can be used as a conductive carrier to improve the efficiency of electric heating in in-situ modification technology of shale oil.

Understanding the Effects of Graphene Coating on the Electrostatic Field at the Tip of an Atom Probe Tomography Specimen

Abstract As a three-dimensional characterization method, atom probe tomography can provide key information that other methods cannot offer. Conductive coatings have proved to be an effective way for biological samples, and nonconductive samples in general, to be analyzed using voltage-pulsed atom probe tomography. In this study, we analyzed the effects of graphene coating on an electrically conductive material and were able to confirm the detection of carbon atoms. We compare quantitative electrostatic field metrics for a single-coated and a multi-coated specimen and measure both a reduced voltage after graphene coating and lowered charge-state ratios for different ion species, suggesting a lowered evaporation field related to the graphene coating. This information will be instructive for future studies on graphene-coated, nonconductive biological specimens.

Elucidating and Mitigating High-Voltage Interfacial Chemomechanical Degradation of Nickel-Rich Lithium-Ion Battery Cathodes Via Conformal Graphene Coating

Layered-type, nickel-rich lithium nickel manganese cobalt oxides (NMCs) are well-established cathode materials for high-performance lithium-ion batteries. These materials exhibit stable cycling within mild voltage windows (up to 4.3 V vs. Li/Li+) but can be charged to higher potentials (4.8 V vs. Li/Li+) to access additional capacity. However, high-voltage operation is generally avoided due to severe interfacial and chemomechanical degradation, such as electrolyte decomposition reactions and non-uniform buildup of chemomechanical strains that can result in particle fracture and compromised cyclability.In this work, we find that a conformal graphene coating enables significant enhancements in the cycle life and coulombic efficiency of NMC cathodes during high voltage electrochemical cycling. Postmortem surface chemical analysis reveals that graphene-coated NMC electrodes exhibit reduced spectral intensities corresponding to electrolyte decomposition products, suggesting that the interfacial graphene layer limits parasitic electrode-electrolyte interactions. Furthermore, global and local structural analysis shows that the graphene coating mitigates mechanical degradation, which was evidenced by reduced microstrain, particle fracture, and electrochemical creep. Based on these observations, we propose a mechanistic relationship between the spatial uniformity of lithium flux and primary particle-level mechanical degradation, and show that a conformal graphene coating is well-suited to address these issues associated with high voltage chemomechanical degradation. Overall, these results delineate a pathway for rationally mitigating high-voltage chemomechanical degradation of nickel-rich cathodes that can be applied to existing and emerging classes of battery materials.https://doi.org/10.1021/acsaem.1c01995

(Invited) Stabilizing and Enhancing Lithium-Ion Batteries with Chemically Inert 2D Materials

Efficient energy storage systems represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Arguably, the most important advance in energy storage over the past three decades is the lithium-ion battery, which was recently recognized with the Nobel Prize in Chemistry. However, despite its many successes, issues related to safety, energy density, charging time, and operating temperature range have hindered the realization of the full potential of lithium-ion battery technology, particularly in large-scale applications such as grid-level storage and full electrification of transportation networks. Nanostructured materials were once thought to present compelling opportunities for next-generation lithium-ion batteries, but inherent problems related to high surface area to volume ratios at the nanometer-scale (e.g., undesirable surface chemical interactions between electrodes and electrolytes) have impeded their adoption for commercial applications. This talk will explore how the chemical inertness of select two-dimensional (2D) materials are driving a resurgence in nanostructured lithium-ion battery materials [1]. For example, conformal graphene coatings on lithium-ion battery cathode powders mitigate surface degradation and minimize the formation of the solid electrolyte interphase, thus improving cycling stability [2]. In addition, the high electrical conductivity of graphene reduces cell impedance, resulting in enhanced kinetics that enable high-rate capability and low-temperature performance down to –20 °C [3]. On the other hand, ionogel electrolytes based on ionic liquids and hexagonal boron nitride (hBN) nanoplatelets provide safe, high-rate operation at high temperatures up to 175 °C, which represents the highest operating temperature to date for solid-state lithium-ion batteries [4,5]. The strong interfacial interactions between hBN and ionic liquids further enable novel electrolyte architectures based on layered heterostructure ionogels that result in unprecedently high energy densities and rate performance for solid-state batteries [6].[1] H. Bergeron, et al., Chemical Reviews, 121, 2713 (2021).[2] K.-Y. Park, et al., Advanced Energy Materials, 10, 2001216 (2020).[3] K.-Y. Park, et al., Advanced Materials, DOI: 10.1002/adma.202106402 (2021).[4] W. J. Hyun, et al., ACS Nano, 13, 9664 (2019).[5] W. J. Hyun, et al., Advanced Energy Materials, 10, 2002135 (2020).[6] W. J. Hyun, et al., Advanced Materials, 33, 2007864 (2021).

Nanodiamond plates as macroscale solid lubricant: A “non-layered” two-dimension material

Two-dimensional (2D) materials with a layered structure can realize extremely low coefficient of friction (COF) at the nanoscale or microscale. However, the highly ordered sliding interface is difficult to be obtained with conventional layered 2D materials, leading to a significantly higher COF at the macroscale. Hence, a novel strategy using “non-layered” 2D materials for macroscale lubrication is proposed in this study. As a “non-layered” 2D material, nanodiamond (ND) plates with thickness as low as several nanometers were used to fabricate solid lubrication coatings with thickness of approximately 3 μm using drop casting method. The ND plates coating reduced the COF by 54.55% compared to that of the ND particles coating, and by 55.13 and 41.92% compared to graphene and MoS2 coatings, respectively. A transfer layer was formed on the ball surface and a tribofilm with ND plates highly aligned with the sliding direction was formed in the wear track, where the sliding between the ND plates or ND plates and the friction pairs dominates the lubrication performance. Most importantly, the wrinkles and wrapped edge sites commonly observed on layered 2D materials can be eliminated by the high mechanical performance of ND plates, leading to an ordered sliding interface, thus lowering the macroscale COF. This study provides implications for the development of macroscale lubrication systems with “non-layered” 2D materials for engineering applications.

Graphene-coated sintered porous copper surfaces for boiling heat transfer enhancement

• The effect of sintered porous copper structure thickness on pool boiling heat transfer was investigated. • The additional contribution of graphene coating to further HTC enhancement was presented. • Increased wetted area and nucleation sites enhanced heat transfer on sintered porous surfaces. • Liquid supply mechanism and thermal conductivity with graphene coatings further enhanced heat transfer. • Effective heat dissipation underneath bubbles and prevention of hot spots are possible with Graphene coatings. Phase change heat transfer via pool boiling is an effective and low-cost method for applications such as electronics cooling and noticeably depends on bubble dynamics behavior. Porous copper surfaces provide a larger heat transfer area and more nucleation sites at the liquid-surface interface and improve heat transfer compared to bare copper surfaces. In addition, the capability of copper foams in surface replenishment and capillary wicking prevents surface dry-out at elevated heat fluxes. Graphene has recently attracted increasing attention in thermal management applications due to its exceptional thermal and mechanical properties. This study focuses on the effects of foam thickness (i.e., 0.5 mm, 1 mm, 1.5 mm, and 2 mm) and graphene-coating on pool boiling heat transfer on sintered porous surfaces by combining the porous structure with graphene coating. According to the obtained results, thinner samples (i.e., 0.5 mm and 1 mm) exhibited a better performance due to their lower vapor resistance and efficient liquid supply compared to thicker samples (i.e., 1.5 mm and 2 mm). The optimum surface configuration depends on the operating condition. Graphene-coating affects bubble dynamics and leads to further enhancement in boiling heat transfer by increasing the thermal conductivity and wicking rate. The maximum heat transfer enhancement was recorded for the thickness of 0.5 mm on graphene-coated sintered porous copper surfaces as 161% compared to the bare copper surface, while the maximum enhancement with graphene coating was 24% relative to the porous copper surface of the same thickness. Thus, the contribution of graphene coating on sintered porous copper surfaces to further boiling heat transfer enhancement was proven in this study.

Electrophoresed Graphene Coatings for Corrosion Prevention: A Review

Corrosion has been the foremost factor affecting the longevity of metals and alloys since ages. It can be thought of as the force of nature which strives to bring the refined form of elements back to their original state. However, human applications are essentially based on refined forms of elements, thereby creating the need for corrosion protection. Corrosion prevention methodologies span between coatings, inhibitors, sacrificial anodes. Coatings have seen maximum utility due to their simplicity and low cost. Researchers are on the lookout of a durable, environment-friendly, cheap coating. Graphene, a carbonaceous material is a new found interest delivering optimistic results. It carries the advantage of being a 2D material, whereby thin coatings with superior quality can be achieved. Additionally, its chemical inertness has proven to be a useful characteristic. On similar lines, electrophoretic deposition (EPD) is low cost and simple technique which has attracted the attention of researchers. It has been used to deposit colloidal solutions onto suitable substrates, mostly ceramics. The significance is growing steadily owing to its capability in producing thin films, nanomaterials and composite coatings. This paper highlights the use of graphene through EPD for synthesis of anti-corrosive coatings.

Atomic perspective of contact protection in graphene-coated high-entropy films

Covering graphene (Gr) coatings on high-entropy alloy (HEA) films is a promising approach to avoid its contact damage. However, current understanding regarding the underlying strengthening mechanisms of these systems at atomic level remains limited. Here, the contact mechanical behavior and strengthening mechanism of Gr-coated HEA films during nanoindentation were unravelled by means of molecular dynamics (MD) simulations. The results demonstrated that an increase of about 80.3% in indentation hardness of the composites can be endowed by covering a Gr layer, meaning a dramatically enhanced carrying capacity. More importantly, it would be further improved as Gr layers varied from monolayer to trilayer (increases of about 129.3% and 160.2% for the bilayer and trilayer cases, respectively). Moreover, we confirmed that due to the high in-plane stiffness, Gr coatings can effectively decrease the contact stress and inhibit the dislocation nucleation, which facilitated the decreased subsurface damage. Meanwhile, high-density Shockley and Stair-rod dislocations induced by an increase of the actual loading area synergistically promoted a strong strain hardening effect in the composites. It was deemed that the capability of contact protection of HEA films can be further improved after covering Gr coatings which can be ascribed to the high in-plane stiffness of Gr layers coupled with its induced strong strain hardening effect. These findings may contribute to the development and design of Gr-coated HEA composites with better mechanical properties.

Ultra-Broadband Strong Electromagnetic Interference Shielding with Ferromagnetic Graphene Quartz Fabric.

Flexible electromagnetic interference (EMI) shielding materials with ultrahigh shielding effectiveness (SE) are highly desirable for high-speed electronic devices to attenuate radiated emissions. For hindering interference of their internal or external EMI fields, however, a metallic enclosure suffers from relatively low SE, band-limited anti-EMI responses, poor corrosion resistance, and non-adaptability to the complex geometry of a given circuit. Here, a broadband, strong EMI shielding response fabric is demonstrated based on a highly structured ferromagnetic graphene quartz fiber (FGQF) via a modulation-doped chemical vapor deposition (CVD) growth process. The precise control of the graphitic N-doping configuration endows graphene coatings on specifically designable quartz fabric weave with both high conductivity (3906 Scm-1 ) and high magnetic responsiveness (a saturation magnetization of ≈0.14 emug-1 under 300 K), thus attaining synergistic effect of EMI shielding and electromagnetic wave (EMW) absorption for broadband anti-EMI technology. The large-scale durable FGQF exhibits extraordinary EMI SE of ≈107dB over a broadband frequency (1-18GHz), by configuring ≈20nm-thick graphene coatings on a millimeter-thick quartz fabric. This work enables the potential for development of an industrial-scale, flexible, lightweight, durable, and ultra-broadband strong shielding material in advanced applications of flexible anti-electronic reconnaissance, antiradiation, and stealthy technologies.

Stages of Defect Formation in a Graphene Coating on a Copper Substrate under Irradiation with Helium and Argon Ions

Stages of Defect Formation in a Graphene Coating on a Copper Substrate under Irradiation with Helium and Argon Ions

Sustaining dropwise condensation on nickel-plated copper surfaces with As-grown graphene coatings

• Dropwise condensation on as-grown graphene on electroplated Ni has been achieved. • Dropwise condensation has been successfully promoted on Cu using Ni-Gr coatings. • Condensation rate has been enhanced up to 2.9 times higher than filmwise mode. • The electroplated Ni-Gr coatings on Cu are more robust than the Ni-Gr surface. Dropwise condensation (DWC) has been extensively investigated owing to its substantially higher efficiency compared with filmwise condensation (FWC). However, performing the highly efficient DWC has been hindered by the durability of existing hydrophobic surface coatings. Graphene grown on Nickel (Ni-Gr composite) has been demonstrated in our previous study to sustain the DWC in an aggressive condition for more than 36 months. Compared with traditional heat exchangers made of copper (Cu) and stainless steel, the high purity requirement of Ni substrate for graphene growth and high material cost greatly limit its practical applications. In this study, the cost-effective nickel-plating technique has been explored to apply the robust Ni-Gr coating on prevail metals such as Cu in industry. DWC can be sustained for more than 180 days without noticeable degradation in a steam/air mixture environment. After 180 days, the Ni-Gr coating electroplated on the copper surface (Cu-Ni-Gr) can still facilitate DWC with approximately 2.9 times higher condensation heat transfer rate than that of conventional metal surfaces. The consistently superior anticorrosion properties of Cu-Ni-Gr surfaces is further revealed by Tafel tests. An additional 46% lower corrosion rate than the Ni-Gr surface has been characterized. This study manifests a feasibility to implement the sustainable and highly efficient DWC on other popular heat exchanging metals using super-durable Ni-Gr coatings.

The Surface Structure Origin of Carbon Fiber with Enhanced Electrothermal Properties Prepared by Modification of Graphene Coating

The Surface Structure Origin of Carbon Fiber with Enhanced Electrothermal Properties Prepared by Modification of Graphene Coating

Experimental Comparison of Pool Boiling Performance between Cu-plain Surface and Functionalized Graphene Layers

Functionalized-Graphene coatings have attracted considerable attention because this kind of materials offers many new and greatly improved properties for a wide range of applications. The purpose of this study is to provide experimental observation for pool boiling heat transfer on enhanced copper substrates by Graphene and Fluorinated-Graphene coatings using two different coating techniques, Chemical Vapor Deposition (CVD), and Electrophoretic Deposition (EPD) . HFE-7000 refrigerant is used as a working fluid in this study. It has been shown that the bubbles' density on Graphene coating surface (CVD) is 2 times higher than the bubbles density on Cu-plain, the bubbles density on F-Graphene surface (CVD) is 2.43 times higher than those on Cu-plain, and the bubbles density is 3.7 times on F-Graphene surface (EPD) more than the bubbles density on Cu-plain, and thereby this results in an enhancement in pool boiling HTC up to 20%, 80%, and 200% on Graphene & F-Graphene (CVD), and F-Graphene (EPD) respectively. It has also been proven that pool boiling Heat Transfer Coefficient (HTC) and Critical Heat Flux (CHF) by CVD are affected by the wettability change only, whereas pool boiling HTC and CHF by EPD are affected by two controlling parameters (the wettability change and the surface roughness). The surface morphology of (EPD) F-Graphene coating surface shows larger surface roughness compared to Graphene and F-Graphene surfaces by CVD attributing to more effective structures that result from applying F-Graphene by EPD. The results of this study can be further applied on two-phase heat transfer products to enhance their performance.

Graphene Oxide Framework Structures and Coatings: Impact on Cell Adhesion and Pre-Vascularization Processes for Bone Grafts.

Graphene oxide (GO) is a promising material for bone tissue engineering, but the validation of its molecular biological effects, especially in the context of clinically applied materials, is still limited. In this study, we compare the effects of graphene oxide framework structures (F-GO) and reduced graphene oxide-based framework structures (F-rGO) as scaffold material with a special focus on vascularization associated processes and mechanisms in the bone. Highly porous networks of zinc oxide tetrapods serving as sacrificial templates were used to create F-GO and F-rGO with porosities >99% consisting of hollow interconnected microtubes. Framework materials were seeded with human mesenchymal stem cells (MSC), and the cell response was evaluated by confocal laser scanning microscopy (CLSM), deoxyribonucleic acid (DNA) quantification, real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and alkaline phosphatase activity (ALP) to define their impact on cellular adhesion, osteogenic differentiation, and secretion of vascular growth factors. F-GO based scaffolds improved adhesion and growth of MSC as indicated by CLSM and DNA quantification. Further, F-GO showed a better vascular endothelial growth factor (VEGF) binding capacity and improved cell growth as well as the formation of microvascular capillary-like structures in co-cultures with outgrowth endothelial cells (OEC). These results clearly favored non-reduced graphene oxide in the form of F-GO for bone regeneration applications. To study GO in the context of a clinically used implant material, we coated a commercially available xenograft (Bio-Oss® block) with GO and compared the growth of MSC in monoculture and in coculture with OEC to the native scaffold. We observed a significantly improved growth of MSC and formation of prevascular structures on coated Bio-Oss®, again associated with a higher VEGF binding capacity. We conclude that graphene oxide coating of this clinically used, but highly debiologized bone graft improves MSC cell adhesion and vascularization.

Graphene for Antimicrobial and Coating Application.

Graphene is a versatile compound with several outstanding properties, providing a combination of impressive surface area, high strength, thermal and electrical properties, with a wide array of functionalization possibilities. This review aims to present an introduction of graphene and presents a comprehensive up-to-date review of graphene as an antimicrobial and coating application in medicine and dentistry. Available articles on graphene for biomedical applications were reviewed from January 1957 to August 2020) using MEDLINE/PubMed, Web of Science, and ScienceDirect. The selected articles were included in this study. Extensive research on graphene in several fields exists. However, the available literature on graphene-based coatings in dentistry and medical implant technology is limited. Graphene exhibits high biocompatibility, corrosion prevention, antimicrobial properties to prevent the colonization of bacteria. Graphene coatings enhance adhesion of cells, osteogenic differentiation, and promote antibacterial activity to parts of titanium unaffected by the thermal treatment. Furthermore, the graphene layer can improve the surface properties of implants which can be used for biomedical applications. Hence, graphene and its derivatives may hold the key for the next revolution in dental and medical technology.

Graphene, Phosphorene and Silicene Coatings on the (0001) Surfaces of Hcp Metals: Structural Stability and Hydrophobicity

Graphene, Phosphorene and Silicene Coatings on the (0001) Surfaces of Hcp Metals: Structural Stability and Hydrophobicity

Lithium-Induced Intralayer Rearrangement of Molybdenum Disulfide: Effect of Graphene Coating

Lithium-Induced Intralayer Rearrangement of Molybdenum Disulfide: Effect of Graphene Coating