Deposition of Multiscale Thickness Graphene Coating by Harnessing

Research Article www.acsami.org

Cite This: ACS Appl. Mater. Interfaces 2019, 11, 25500−25507

Deposition of Multiscale Thickness Graphene Coating by Harnessing Extreme Heat and Rapid Quenching: Toward Commercialization Biswajyoti Mukherjee,† O. S. Asiq Rahman,† Aminul Islam, Krishna Kant Pandey, and Anup Kumar Keshri* Plasma Spray Coating Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Patna, Bihta 801106, India

Downloaded via UNIV OF LOUISIANA AT LAFAYETTE on August 3, 2019 at 21:47:04 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: Deposition of graphene as a coating material over large-scale areas is an intense topic of research because of complexities involved in the existing deposition techniques. Higher defects and compromised properties restricted in realizing the full potential of graphene coating. This work aims to deposit graphene coatings by adopting a traditional technique, that is, plasma spraying, which has inherent merits of extremely high cooling rate (∼106 K/s) and low plasma exposure time (∼0.1−10 μs). Graphene nanoplatelets (GNPs) were spray-dried into spherical agglomerates (∼60 μm dia.) and coatings were deposited over a wide range of surfaces. Continuous monitoring of temperature and velocity of in-flight GNPs was done using a diagnostic sensor. Deposition of GNP coatings was the result of striking of quasi-2D melted GNPs with higher velocity (∼197 m/s) toward the substrate. Postcharacterizations confirmed that GNPs did not collapse even after being exposed to harsh environments in plasma. Instead, high temperatures proved to be beneficial in purifying the commercial GNPs. The coatings were transparent even in the short-wavelength infrared region and remained electrically conductive. A proof-of-concept was established by carrying out preliminary corrosion and antifriction tests. Outstanding reduction of ∼3.5 times in corrosion rate and 3 times in coefficient of friction was observed in GNP-deposited coating. It is envisaged that graphene coating by plasma spraying can bring a revolution in commercial sectors. KEYWORDS: graphene, coating, plasma spraying, conductive, optical property, corrosion, antifriction, commercialization facile in depositing graphene films. However, these techniques utilize the deposition of graphene oxide (GO) and consist a large number of structural defects introduced during oxidation and reduction, which can degrade the final properties of the films/coatings.8 Recently, direct deposition of low-cost electrochemically exfoliated graphene using a simple Langmuir− Blodgett protocol has been found to be promising for obtaining ultrathin graphene films on various surfaces.9 However, this protocol is limited to monolayer films and hence cannot be used in applications that require few or higher layer films.11 Therefore, it comes as no surprise that many scientists are still eager to make a significant breakthrough in the fabrication of graphene as films or coatings, which could be commercially exploited and executed in day-to-day life. Moreover, most of these techniques needed the substrate to be electrically conductive or hydrophilic, which further shrink their domain of application. Thus, the fabrication of graphene films/coating for commercialization still remains a challenge. Hence, there is a need to develop a method which can negate the bottlenecks of large-scale fabrication of graphene films over

1. INTRODUCTION Graphene, a 2D allotrope of carbon, has risen to fame because of its extraordinary electron mobility; thermal, electrical, and mechanical properties; high surface area; and optical transparency.1 Over a decade of research on graphene has promised its potential in applications such as supercapacitors, hydrogen storage devices, fuel cells, solar cells, flexible electronics, sensors, membranes, and biological sensing devices, to name a few.1−3 However, eventual utilization of graphene as practical devices requires it to be deposited as films or coatings on different surfaces. To date, several protocols including chemical vapor deposition (CVD), electrophoretic deposition, solution-based method such as layer-by-layer deposition, dip/spin coating, spray coating, and Meyer’s technique have been utilized to grow or deposit graphene over a surface.4−6 While the CVD technique has established itself as the number one choice for fabricating few-layers graphene film, it is not suitable for applications requiring 3D nanostructures over a larger area, thereby limiting its use only in electronics industry.7 In addition, the lack of flexibility in the use of substrate and high production cost will always be associated with this technique. On the other hand, the more conventional electrophoretic deposition or solution-based deposition has proven to be more © 2019 American Chemical Society

Received: March 11, 2019 Accepted: June 24, 2019 Published: June 24, 2019 25500

DOI: 10.1021/acsami.9b04239 ACS Appl. Mater. Interfaces 2019, 11, 25500−25507

Research Article

ACS Applied Materials & Interfaces

Figure 1. (a) FE-SEM image of the spray-dried GNP agglomerates. (b) High-magnification FE-SEM image of a single agglomerate. (c) Digital image of (from left to right) uncoated ITO glass, GNP-coated ITO using 1 pass, 3 passes, and 5 passes, respectively. (d) FE-SEM image of the surface demonstrating uniform deposition of the coating throughout the surface. (e) Cross-section FE-SEM image of GNPs deposited over a glass substrate using 3 passes. (f) Tapping mode AFM image of the GNP coating deposited using 3 passes over the ITO substrate. (g) Height profile taken along the blue line in Figure 1f.

exhibit a fluidlike behavior, similar to polymers at elevated temperatures and has a glass transition temperature (Tg) of 1873 K.12 Recent reports on free-standing graphene and reduced GO as filaments experimentally demonstrated their stability at a temperature as high as 3300 K.13,14 They showed that graphene can withstand temperatures as high as 3300 K in vacuum without any structural defects. These studies motivated us to think in the direction of “quasi-melting” and subsequent deposition of graphene over a surface. In this reference, we attempted to deposit commercially available graphene nanoplatelets (GNP) using a versatile and commercially adapted plasma spray technique, which has traditionally been reserved for the deposition of thermal barrier

a wide range of surfaces for moving graphene coating out of the lab. In this perspective, our group was in continuous pursuit of developing a technique which can be used to deposit graphene coating over any surface. Few recent works on the behavior of graphene at high temperatures fascinated us, which we thought could help in depositing graphene coating. Using molecular dynamics (MD) simulations, Ganz and co-workers predicted that graphene attains a quasi-2D liquid state at 4000−4500 K and move toward 1D at temperatures above 6000 K.11 Their model showed that graphene still holds onto their 6-ring structures in the quasi-2D liquid state. Another interesting study by Xia et al. demonstrated that graphene materials 25501


Research Article

ACS Applied Materials & Interfaces coatings.15 However, the major concern in this hypothesis lies in two folds, that is, (i) flowability of GNPs through the plasma spray system and (ii) survivability of the graphene structure after exposing them to such high temperatures in an ambient environment. Therefore, we are attempting to make spherical agglomerates of GNPs, which could assist better flowability of the GNPs within the plasma spray system and through the nozzle. Additionally, the extremely high cooling rate (∼106 K/ s) and low plasma exposure time (∼0.1−10 μs) involved with this system could be beneficial in retaining the structure of GNP.16

3. RESULTS AND DISCUSSION Commercially available exfoliated graphene nanoplatelets was used as feedstock in this study. The GNPs consist multilayer graphene (10−20 layers) that partially inherit the properties of single-layer graphene with much lower production cost.17 More details about the starting GNPs are provided in the Supporting Information (Figure S1).However, the smaller size, low density (∼1.9 g/cm3), and the tendency to aggregate within themselves will prevent the flow of GNPs in the plasma spray system. We therefore performed spray drying to form agglomerates of GNPs as shown schematically in Supporting Information (Figure S2). The agglomerates have a size of ∼60 μm and resemble sponge like microstructure, much like micro graphene sponge as shown in Figure 1a,b. The special circular morphology of GNP sponges decreases the overall surface area and prevents van der Waals attraction within the agglomerates, resulting in better flowability within the plasma spray system. The GNP powder was then fed into the plasma spray nozzle using argon (Ar) as the carrier gas. However, it is known that the temperature along the plasma periphery to the core shoot up to 2000−12 000 K.16 Hence, the GNPs exposed to this temperature in the presence of oxidizing atmosphere will burn immediately. We, therefore, tried to cut down the connection between the plasma plume having GNPs and atmosphere using an inert atmosphere shroud. The shroud shoots jet of argon through the perforated chamber that envelops the plasma plume. This introduces an inert atmosphere, analogous to the vacuum in the zone where the GNPs and plasma plume come in contact. More details about the plasma spray system and the inert atmosphere shroud are included in Supporting Information (Figure S3). Plasma spray coating of GNPs was performed over ITO at parameters obtained after rigorous optimizations and the deposition efficiency was around ∼66.3%. The coatings deposited over ITO changes from transparent to opaque upon increasing the number of passes (Figure 1c). Upon examining the coated surface through FE-SEM, platelet-like microstructures are observed, which hints toward the deposition of GNP over the substrate (Figure 1d). The platelets are also seen to be uniformly distributed over the substrate, toward their basal inclination. The platelets are found to be completely covering the substrate. We now move to another stumbling block to measure the thickness of the coatings using FE-SEM. Figure 1e shows the cross-sectional FE-SEM image of the coating over ITO that was deposited using 3 passes, depicting a thickness of ∼400 nm. The interface between the platelets and ITO is clean, and it is fascinating to see that the coating is well adhered to the surface. By varying only the number of passes, a broader range of coating thicknesses from few hundred nanometres to micrometres could be deposited (Supporting Information Figure S4). Figure 1f shows the AFM image showing the coating deposited using a 3 pass over ITO. The resulting thickness was ∼300− 400 nm (Figure 1g), which resembles to the result obtained by FE-SEM. The thickness of the coating measured as 210 ± 40 nm at the non-uniform region caused due to the hindrance offered by the substrate holder. We also successfully deposited GNP coatings over various ranges of surfaces including glass, aluminum, stainless steel, mild steel, and ceramics (Supporting Information Figure S5).The roughness of the GNP coating on various surfaces was between 7 and 12 nm as shown in the Supporting Information (Figure S6). It is noteworthy to

2. EXPERIMENTAL DETAILS 2.1. Fabrication of GNP Coating. Commercially obtained GNPs were spray-dried in order to increase their flowability through the hose during the plasma spraying. Using spray drying, the 2D “nano” GNP platelets can be converted into free-flowing spherical agglomerates of GNPs. In this process, the GNPs are dispersed in an aqueous organic binder (i.e., poly-vinyl alcohol), and the resulting slurry was atomized and fed as drops in the chamber through a spraying nozzle, where the slurry dries and forms spherical agglomerates. The spray-dried GNPs were then deposited over commercially obtained ITO (indium tin oxide), mild steel, aluminum, and alumina substrates using the plasma spray system (Oerlikon Metco, Switzerland) equipped with a 9MB gun. The substrates were ultrasonically cleaned in ethanol before deposition of the coatings. 2.2. Characterizations. Morphology of the starting GNPs, spraydried GNPs, and coatings was analyzed using a field emission scanning electron microscope, (Zeiss, Gemini SEM500, Germany). Atomic force microscopy (AFM) images (Tapping mode) of the GNP coatings were obtained using an AFM system (NTEGRA Prima, Germany).The transparency of the coatings was characterized using a Fourier transform infrared spectrophotometer (FTIR, Tensor 27, Bruker, Germany). Conductivity tests were performed using an AFM system (Asylum/Oxford Instruments, MFP3D Origin) equipped with a conductive AFM module. The measurement of current was done in contact mode and specific spots were selected and the voltage was applied to generate the I−V curve of the samples. Raman spectra were collected using an excitation laser wavelength of 514 nm and 60 mW power using a Raman spectrometer (Raman CRM-2000, WiTec, Germany). X-ray diffraction (XRD) of the GNP powder was carried out using an X-ray diffractometer (TTRAX III, Rigaku, Japan), while the GNP coating was analyzed using a grazing incidence X-ray diffractometer employing Cu Kα radiation (X’pert PAN-alytical, Netherlands). X-ray photoelectron spectroscopy (XPS, PHI5000 Versa Prob II, FEI Inc.) was used to verify the structure of GNPs after coating. High resolution of the GNPs before and after coating was obtained using a high-resolution transmission electron microscope (HR-TEM) (FEI Tecnai, USA) (accelerating voltage: 200 kV). Electrochemical measurements were measured using a potentiostat/galvanostat (Gamry Electochem, US) in 3.5% NaCl solution. Area of 0.25 cm2 was exposed to the corrosive solution. Icorr and Ecorr values were obtained by extrapolating the anodic and cathodic branches. Open circuit potential was stabilized before running the test. Antifriction tests were carried out using a Ball-on-disk Tribometer (Ducom, India) at a load of 5 N with a stationary sample and a rotating tungsten carbide (WC) ball with a sliding speed of 250 rpm. The tests were conducted for 2000 s, which translates to 7500 cycles. AccuraSpray in-flight diagnostic sensor (Tecnar Automation Ltée, QC, Canada) was used to measure the in-flight temperature and velocity of the GNPs. Cross-correlation factor (CCF) value, greater than 0.9, was maintained throughout the experiment. CCF of 0.9 or higher confirms errors in velocity and temperature lesser than 1.5 m/s and 15 °C, respectively. 25502


Research Article


Figure 2. (a) Raman spectra of the GNPs coating showing a slight reduction in D peak. (b) HR-TEM image showing GNPs sheets and the inset displays the wall spacing of the GNPs coating. (c) Atomic-scale HR-TEM image of a single sheet graphene after plasma spraying; the inset shows the FFT image of the sheet. (d) IFFT of the GNPs sheet showing the honeycomb structure of graphene. (e) XPS spectra of the GNPs coating.

mention that this is also the first report to demonstrate a nanometer range deposit using the plasma spray technique. However, we are well aware that GNPs undergo heavy oxidation at high temperatures in an oxidizing environment.18 Therefore, in order to see any structural changes in the coated GNPs, we conducted Raman spectroscopy over the coating. Surprisingly, the spectra revealed all the characteristics peaks of graphene, that is, D peak at 1342 cm−1, G peak at 1572 cm−1, and 2D peak at 2695 cm−1(Figure 2a). This suggests that the GNP structure was intact after plasma spraying. In order to confirm the repeatability, Raman spectra were collected from 10 different positions of the coating and they all showed the similar results. Additionally, the intensity ratio of D peak to G peak (ID/IG) is 0.02, which is slightly lower than that of the starting GNP (ID/IG = 0.17). As the D peak is associated with defect/disorder in the graphene structure, decrease in ID/IG advocates slightly reduced defects in GNPs after plasma spraying.19 Moreover, the low ID/IG ratio of the deposited GNP also distinguishes it with graphene-like nanocarbon, which hints toward the successful retention of the GNP.20 This suggests that the GNPs might have undergone thermal

treatment, which not only improved the 2D arrangements of carbon layer but also removed volatile impurities present in the commercial GNPs. Our result converges with various studies that discuss about the purification of graphene using thermal annealing.21,22 We also confirmed the structure of GNPs in coating using HR-TEM. No change in the wall spacing of the plasma-sprayed GNPs (0.34 nm) was observed when compared to the commercial GNPs (0.34 nm) (Figure 2b). Figure 2c shows the atomic-scale image of a single layer graphene that was extracted from the coating showing uniformly aligned carbon atoms. Obtaining a clean atomicscale image is an indication of the purity of the sample.20 The inset in Figure 2c shows the fast Fourier transform (FFT) of the marked area, where a hexagonal diffraction pattern corresponding to the basal plane of graphene is observed. Inverse fast Fourier transform (IFFT) was applied on the marked area in Figure 2c to examine the atomic image of the plane. A hexagonal atomic array resembling a perfect 2D honeycomb structure composed of closely arranged carbon atoms of graphene is clearly observed in Figure 2d, which confirms the high quality of the plasma-sprayed graphene.23−25 25503


Research Article


will be an assessment of the feasibility of our fabrication protocol. For comparison, the conductivity of Al2O3 is also presented to get a clear idea of the conductivity of the GNP coating. Figure 4a displays the conductive imaging of the Al2O3 surface showing a complete dark region indicating its nonconducting behavior. The resulting I−V curves further shows that no conduction can be measured at any voltage (Figure 4b). On the contrary, the plasma spray-fabricated coated GNP (1 pass) shows a rather bright conductive image (Figure 4c). The corresponding I−V curve (Figure 4d) shows a rapid increase in current with voltage and rapidly saturates at a preamplifier measurement range, which is representative of an excellent conducting surface.32,33 The coatings fabricated using multiple passes (n = 3, 5) also demonstrated similar characteristic I−V curves, indicating no loss in conductivity. After the successful deposition of GNP, the next step is to find a conscious reasoning, which could have aided the deposition of GNP using a technique that involves temperature in the range of thousands. It is known that the temperature at the epicenter of a plasma plume is around 12 000 K, which keeps on reducing as we moves toward the periphery of the plume.34 A schematic representation of the temperature distribution in plasma plume is added in the Supporting Information (Figure S3). The GNPs in a plasma spray can encounter the plume in two possible ways: (i) directly into the epicenter and (ii) just outside epicenter at the periphery of the plume. Now, if the GNP comes in contact with the plume at the epicenter where the temperature is highest (∼12 000 K), there is a high chance for them to sublime or collapse. Although, there has been no experimental evidence of melting of graphene, MD simulations have demonstrated that a graphene sheet exposed to 5000−6000 K moves toward 1D structure (i.e., melting).9,10 However, our postcoating characterizations did not indicate any major gain in defects in the GNPs. Therefore, it is safe to assume that the GNPs injected at the epicenter sublime or collapse at the instant as it comes in contact with the plume and does not reach to the substrate. On the other hand, the GNPs which fall just at the periphery of the plume are expected to get heated and accelerated toward the substrate. Unlike the previous study that reports the effect of temperature on a single graphene sheet, our experiment involves the heating of a bundle of agglomerated GNPs. We speculate that the heat supplied to the GNP agglomerates is uniformly distributed toward the inner core of the agglomerates because of very high thermal conductivity of graphene (3000−5000 W/m K). Hence, the heat keeps on transferring from one to other platelets and prevents any localized heating in the agglomerate. In addition, we believe that the extremely high cooling rate (106 K/s) and very less plasma plume exposure time (∼0.1−10 μs) also helped it from overheating. Now, we attempted to experimentally measure the in-flight temperature of the GNP agglomerates just after encountering the plasma plume. We used an in-flight particle diagnostic sensor to measure the temperature and velocity of the agglomerates. More details about the diagnostic sensor is proved as Supporting Information (Section S1).The sensor measured temperature of the GNP agglomerates in the range of 3400−3700 K (Figure 5a,b). Now, recalling the work of Ganz et al., there is a high probability that the GNP approach toward the quasi-2D liquid state exposed to a temperature close to 4000 K.9 This quasi-2D liquid state gives a viscous nature to the graphene without disturbing its lattice structure. These viscous quasi-2D graphene strikes the substrate with

The XRD pattern also showed a less intense (002) diffraction peak after plasma spraying (Supporting Information, Figure S7). The weak (002) peak and a slight increment in full width at half-maximum of the (002) diffraction peak compared to that of the commercially obtained GNP are also an indicative of few-layer feature of the GNP.26,27 We further confirm the structural retention of GNPs using XPS. Figure 2e shows the XPS spectra of the GNP coating. C 1s core-level photoelectron spectra were deconvoluted into three main components at 284.2, 285.4, and 288.5 eV, which are attributed to C−C, C−O, and CO bonds, respectively.28 The sharp C−C bond at 284.2 refers to the sp2 carbon fraction, which is an indication of the graphene structure. The carbon sp2 fraction was calculated to be 68%, which indicates the retention of the graphene structure after plasma spraying.29 The minor peaks (C−O and CO) can be the result of oxygen adsorption over the GNPs during exposing the surface at an ambient atmosphere. We can therefore assure that the GNPs were successfully deposited through plasma spraying with no additional defects. To further examine the deposited GNP coating, its optical transparency and the conductivity were characterized. It was observed from the digital images (Figure 1c) that the coatings visually change from transparent to near opaque upon increasing the thickness of the coatings by increasing the number of passes. For further insight in the dependencies of transmittance of the GNP coating on the film thickness, the percentage of transmittance was studied using a FT-IR. Figure 3 presents the IR spectra of the GNP coatings with different

Figure 3. IR spectra of GNP films obtained at different thicknesses (N indicates the number of passes).

film thicknesses. The initial assessment of the spectra showed that the transmittance of the GNP coating decreased with increasing film thickness from N = 1 to N = 5 pass. The GNP coating deposited using a single pass demonstrated a transmittance of ∼47% throughout the entire wavelength (2250−3000 nm). This indicates that our GNP coatings remain transparent even in the short-wavelength infrared region, which is in contrast with the widely used fluorine doped tin oxide and ITO, which shows strong absorption in this region.30,31 Conductivity of GNP is always a prime significance as it plays a major role in defining the usability of the material in diverse applications. However, plasma spraying involves high temperatures which could have an adverse effect on the conductivity of the coatings. Hence, the electrical conductivity of our GNP coatings was tested using conductive AFM, which 25504


Research Article


Figure 4. (a) Conductive image of Al2O3 surface and (b) resulting I−V curves for the same showing the nonconducting behavior of the surface; (c) conductive image of the GNP coating fabricated using 1 pass and (d) its corresponding I−V curve showing the highly conducting behavior of the surface.

Figure 5. Snapshot at (a) initial and (b) after the introduction of GNPs into the plume showing the in-flight particle temperature (T) and velocity (V).

velocity close to ∼197 m/s. We postulate that striking viscous GNPs with high velocity will lead to adhere to the substrate analogous to the deposition of ceramic splat, which is also clear from the cross-section image of the coating. We predict that these GNP coatings will have wide spectrum of applications in energy sectors, membranes, as protective and oxidation resistance coatings, and wear resistance coatings, where large scale is a significant factor. Therefore, in order to show the proof-of-concept for these coatings, we performed a preliminary investigation on the corrosion resistance of GNP coating over a mild steel substrate. For comparison, an uncoated mild steel coating was used as reference. Potentiodynamic polarization curves of the bare and GNPs coatings are shown in Figure 6 after immersion in 3.5% NaCl aqueous solution. The corresponding corrosion potential (Ecorr) and corrosion current density (Icorr) values were obtained using the Tafel extrapolation method from the point of intersection of cathodic and anodic Tafel curves. A positive shift in Ecorr values and decrease in Icorr values infer to the enhanced corrosion resistance of GNP-coated mild steel. Furthermore, the GNPcoated mild steel showed an exponential reduction in the corrosion rate from 394 × 10−3 to 112 × 10−3 mpy. Our results demonstrated a remarkable reduction of ∼3.5 times in

Figure 6. Tafel plots of mild steel and GNP-coated mild steel; the inset shows the respective corrosion rate.

corrosion rate and are comparable to previous observations (i.e., 4 times).35 The inherent inertness of the GNP layer cuts down the interaction between oxygen (O2) and corrosive species (Cl−) with the underlying surface. This impressive improvement in the corrosion behavior could also be attributed to the corrosion-resisting behavior of GNPs as well as its hydrophobic nature, which could have slowed down the transport of electrolyte molecules through it. Additionally, it can create a tortuous path for the corrosive species to react with the surface and effectively lowers down the corrosion. Further, the viability of the GNP-coated surface was also investigated for its potential application as antifriction coating. Wear tests were performed over a GNP-coated Al2O3 substrate under a load as high as 5N against a tungsten carbide (WC) ball. Tests were also performed over a bare Al2O3 substrate to evaluate the degree of improvement in the antifriction property after coating GNP. Figure 7 demonstrates the coefficient of friction (COF) of different surfaces for an interval of 2000s (7500 cycles). Outstanding reduction of 3 times in COF was 25505


Research Article

ACS Applied Materials & Interfaces ORCID

Anup Kumar Keshri: 0000-0001-6929-5810 Author Contributions †

B.M. and O.S.A.R. equal contributors.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS Authors B.M. and A.K.K. acknowledge the financial support provided by the Indian Institute of Technology Patna. A.K.K. and K.K.P. acknowledge the financial support from RESPOND-ISRO, Government of India, grant no. ISRO/RES/ 3/735/16-17. A.K.K. and A.I. acknowledge the financial support from DST, Government of India, grant no. DST/ TSG/AMT/2015/264. The authors acknowledge the Centre for Nanoscience, IIT Kanpur for the various characterizations. The authors also acknowledge the “Conductive Atomic Force Microscopy” Central facility cAFM, IIT Bombay for providing conductive AFM.

Figure 7. COF of the GNP coating over alumina at a load of 5 N.

observed for the GNP-coated surface (COF = 0.17), when compared to the bare Al2O3 substrate (COF = 0.51). The GNP-coated surface demonstrates constant COF throughout the entire test length of 7500 cycles, which indicates toward the durability of the surface for longer run. It is also worth mentioning that this result is comparable to that of the antifriction performance of monolayer graphene.36 Moreover, this result also outperforms the antifriction capability of bulk consolidated GNP operated at much lower load for short duration.37 The shearing capability of GNPs combined with their atomically smooth lamellar structure makes the best lubricating candidate help in reducing the COF and simultaneously protecting the underlying surface.38 Moreover, the multilayer stack is helpful in making them a potential selflubricating candidate for longer runs.

■

4. CONCLUSIONS In summary, we have successfully demonstrated the deposition of stacked GNPs using a traditional plasma spraying technique. Postcharacterization of the GNP coatings exhibited that no defects were introduced in the GNPs after coating. The coatings displayed good optical transparency and conductivity. Further, coatings can be deposited on any substrate and the thickness of coatings can be controlled just by varying the number of passes. Deposited plasma-sprayed GNP coating displayed proof-of-concept for its applications as corrosionresistant and antifriction coating. This study has the potential to open new avenues in graphene-based coatings and can be used in industries due to its simplicity and scalability.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.9b04239. Initial characterizations of GNP, schematic showing the spray drying process, details of plasma spraying, FE-SEM image showing the coating cross section, supporting digital images, surface roughness, XRD pattern, and details of working of the in-flight particle diagnostic sensor (PDF) (PDF)

■

REFERENCES

(1) Rümmeli, M. H.; Rocha, C. G.; Ortmann, F.; Ibrahim, I.; Sevincli, H.; Börrnert, F.; Kunstmann, J.; Bachmatiuk, A.; Pötschke, M.; Shiraishi, M.; Meyyappan, M.; Büchner, B.; Roche, S.; Cuniberti, G. Graphene: Piecing it Together. Adv. Mater. 2011, 23, 4471−4490. (2) Novoselov, K. S.; Fal’ko, V. I.; Colombo, L.; Gellert, P. R.; Schwab, M. G.; Kim, K. A Roadmap for Graphene. Nature 2012, 490, 192−200. (3) Randviir, E. P.; Brownson, D. A. C.; Banks, C. E. A Decade of Graphene Research: Production, Applications and Outlook. Mater. Today 2014, 17, 426−432. (4) Li, X.; Cai, W.; An, J.; Kim, S.; Nah, J.; Yang, D.; Piner, R.; Velamakanni, A.; Jung, I.; Tutuc, E.; Banerjee, S. K.; Colombo, L. Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils. Science 2009, 324, 1312−1314. (5) Ruoff, S. J.; Zhu, Y.; Lee, S. H.; Stoller, M. D.; Emilsson, T.; Park, S.; Velamakanni, A.; An, J.; Ruoff, R. S. Thin Film Fabrication and Simultaneous Anodic Reduction of Deposited Graphene Oxide Platelets by Electrophoretic Deposition. J. Phys. Chem. Lett. 2010, 1, 1259−1263. (6) Shen, J.; Hu, Y.; Li, C.; Qin, C.; Shi, M.; Ye, M. Layer-by-Layer Self-Assembly of Graphene Nanoplatelets. Langmuir 2009, 25, 6122− 6128. (7) Yeom, D.-Y.; Jeon, W.; Tu, N. D. K.; Yeo, S. Y.; Lee, S. S.; Sung, B. J.; Chang, H.; Lim, A. H.; Kim, H. High-Concentration Boron Doping of Graphene Nanoplatelets by Simple Thermal Annealing and their Supercapacitive Properties. Sci. Rep. 2015, 5, 9817. (8) Zhu, Y.; Murali, S.; Cai, W.; Li, X.; Suk, J. W.; Potts, J. R.; Ruoff, R. S. Graphene and Graphene Oxide: Synthesis, Properties, and Applications. Adv. Mater. 2010, 22, 3906−3924. (9) Heidler, J.; Yang, S.; Feng, X.; Müllen, K.; Asadi, K. Ferroelectric Field-Effect Transistors based on Solution-Processed Electrochemically Exfoliated Graphene. Solid-State Electron. 2018, 144, 90−94. (10) Zheng, Q.; Ip, W. H.; Lin, X.; Yousefi, N.; Yeung, K. K.; Li, Z.; Kim, J.-K. Transparent Conductive Films Consisting of Ultralarge Graphene Sheets Produced by Langmuir-Blodgett Assembly. ACS Nano 2011, 5, 6039−6051. (11) Ganz, E.; Ganz, A. B.; Yang, L.-M.; Dornfeld, M. The Initial Stages of Melting of Graphene between 4000 K and 6000 K. Phys. Chem. Chem. Phys. 2017, 19, 3756−3762. (12) Xia, W.; Vargas-Lara, F.; Keten, S.; Douglas, J. F. Structure and Dynamics of a Graphene Melt. ACS Nano 2018, 12, 5427−5435. (13) Kim, Y. D.; Kim, H.; Cho, Y.; Ryoo, J. H.; Park, C.-H.; Kim, P.; Kim, Y. S.; Lee, S.; Li, Y.; Park, S.-N.; Shim Yoo, Y.; Yoon, D.; Dorgan, V. E.; Pop, E.; Heinz, T. F.; Hone, J.; Chun, S.-H.; Cheong,

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +91-612-3028184. 25506


Research Article


Maji, S. K. Cell Alignment on Graphene−Amyloid Composites. Adv. Mater. Interfaces 2018, 5, 1800621. (34) Mauer, G.; Vaßen, R.; Stöver, D. Plasma and Particle Temperature Measurements in Thermal Spray: Approaches and Applications. J. Therm. Spray Technol. 2011, 20, 391−406. (35) Prasai, D.; Tuberquia, J. C.; Harl, R. R.; Jennings, G. K.; Bolotin, K. I. Graphene: Corrosion-Inhibiting Coating. ACS Nano 2012, 6, 1102−1108. (36) Berman, D.; Deshmukh, S. A.; Sankaranarayan, S. K. R. S.; Erdemir, A.; Sumant, A. V. Extraordinary Macroscale Wear Resistance of One Atom Thick Graphene Layer. Adv. Funct. Mater. 2014, 24, 6640. (37) Nieto, A.; Lahiri, D.; Agarwal, A. Synthesis and properties of bulk graphene nanoplatelets consolidated by spark plasma sintering. Carbon 2012, 50, 4068−4077. (38) Wu, P.; Li, X.; Zhang, C.; Chen, X.; Lin, S.; Sun, H.; Lin, C.-T.; Zhu, H.; Luo, J. Self-Assembled Graphene Film as Low Friction Solid Lubricant in Macroscale Contact. ACS Appl. Mater. Interfaces 2017, 9, 21554−21562.

H.; Lee, S. W.; Bae, M.-H.; Park, Y. D. Bright Visible Light Emission from Graphene. Nat. Nanotechnol. 2015, 10, 676−681. (14) Bao, W.; Pickel, A. D.; Zhang, Q.; Chen, Y.; Yao, Y.; Wan, J.; Fu, K.; Wang, Y.; Dai, J.; Zhu, H.; Drew, D.; Fuhrer, M.; Dames, C.; Hu, L. Nanocarbon Paper: Flexible, High Temperature, Planar Lighting with Large Scale Printable Nanocarbon Paper. Adv. Mater. 2016, 28, 4684−4691. (15) Padture, N. P.; Gell, M.; Jordan, E. H. Thermal Barrier Coatings for Gas-Turbine Engine Applications. Science 2002, 296, 280−284. (16) Fauchais, P. Understanding plasma spraying. J. Phys. D: Appl. Phys. 2004, 37, R86−R108. (17) Kavan, L.; Yum, J. H.; Grätzel, M. Optically Transparent Cathode for Dye-Sensitized Solar Cells Based on Graphene Nanoplatelets. ACS Nano 2011, 5, 165−172. (18) Surwade, S. P.; Li, Z.; Liu, H. Thermal Oxidation and Unwrinkling of Chemical Vapor Deposition-Grown Graphene. J. Phys. Chem. C 2012, 116, 20600−20606. (19) Ferrari, A. C.; Meyer, J. C.; Scardaci, V.; Casiraghi, C.; Lazzeri, M.; Piscanec, S.; Jiang, D.; Novoselov, S.; Roth, S.; Geim, A. K. Raman Spectrum of Graphene and Graphene Layers. Phys. Rev. Lett. 2006, 97, 187401. (20) Kumar, A.; Patil, S.; Joshi, A.; Bhoraskar, V.; Datar, S.; Alegaonkar, P. Mixed phase, sp2−sp3 bonded, and disordered few layer graphene-like nanocarbon: Synthesis and characterizations. Appl. Surf. Sci. 2013, 271, 86−92. (21) Song, L.; Khoerunnisa, F.; Gao, W.; Dou, W.; Hayashi, T.; Kaneko, K.; Endo, M.; Ajayan, P. M. Effect of High-Temperature Thermal Treatment on the Structure and Adsorption Properties of Reduced Graphene Oxide. Carbon 2013, 52, 608−612. (22) Andrews, R.; Jacques, D.; Qian, D.; Dickey, E. C. Purification and Structural Annealing of Multiwalled Carbon Nanotubes at Graphitization Temperatures. Carbon 2001, 39, 1681−1687. (23) Ci, L.; Song, L.; Jin, C.; Jariwala, D.; Wu, D.; Li, Y.; Srivastava, A.; Wang, Z. F.; Storr, K.; Balicas, L.; Liu, F. Atomic layers of hybridized boron nitride and graphene domains. Nat. Mater. 2010, 9, 430−435. (24) Lehtinen, O.; Kurasch, S.; Krasheninnikov, A. V.; Kaiser, U. Atomic scale study of the life cycle of a dislocation in graphene from birth to annihilation. Nat Commun. 2013, 4, 2098. (25) Alegaonkar, A. P.; Alegaonkar, P. S.; Nanocarbons: Preparation, assessments, and applications in structural engineering, spintronics, gas sensing, EMI shielding, and cloaking in X-band Nanocarbon and its Composites; Elsevier, 2019; pp 171−285. (26) Liu, T.; Zhang, X.; Liu, M.; Wu, W.; Liu, K.; Liu, Y.; Gu, Y.; Zhang, R. One-step room-temperature exfoliation of graphite to 100% few-layer graphene with high quality and large size. J. Mater. Chem. C 2018, 6, 8343−8348. (27) Geng, Y.; Wang, S. J.; Kim, J.-K. Preparation of graphite nanoplatelets and graphene sheets. J. Colloid Interface Sci. 2009, 336, 592−598. (28) Fujimoto, A.; Yamada, Y.; Koinuma, M.; Sato, S. Origins of sp3C Peaks in C1s X-ray Photoelectron Spectra of Carbon Materials. Anal. Chem. 2016, 88, 6110−6114. (29) Alegaonkar, A.; Alegaonkar, P.; Pardeshi, S. Exploring molecular and spin interactions of Tellurium adatom in reduced graphene oxide. Mater. Chem. Phys. 2017, 195, 82−87. (30) Wang, S. J.; Geng, Y.; Zheng, Q.; Kim, J.-K. Fabrication of highly conducting and transparent graphene films. Carbon 2010, 48, 1815−1823. (31) Wang, X.; Zhi, L.; Müllen, K. Transparent, Conductive Graphene Electrodes for Dye-Sensitized Solar Cells. Nano Lett. 2008, 8, 323−327. (32) Martin-Olmos, C.; Rasool, H. I.; Weiller, B. H.; Gimzewski, J. K. Graphene MEMS: AFM Probe Performance Improvement. ACS Nano 2013, 7, 4164−4170. (33) Das, S.; Kumawat, M. K.; Ranganathan, S.; Kumar, R.; Adamcik, J.; Kadu, P.; Padinhateeri, R.; Srivastava, R.; Mezzenga, R.; 25507


Deposition of Multiscale Thickness Graphene Coating by Harnessing

Recommend Documents