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Journal of Alloys and Compounds xxx (xxxx) xxx

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Journal of Alloys and Compounds j o u r n a l h o m e p a g e : h t t p : / / w w w . e l s e v ie r . c o m / l o c a t e / j a l c o m

An exploration on the use of in-house synthesized reduced few layer graphene particles as a reinforcement during sono-electroplating of Cu matrix composite films Akhya Kumar Behera a, Ramkumar Chandran a, Smarajit Sarkar b, Archana Mallik

a, *

a

Electrometallurgy and Corrosion Laboratory, Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, 769008, Odisha, India b High Temperature Laboratory, Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela, 769008, Odisha, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 24 July 2019 Received in revised form 15 October 2019 Accepted 16 October 2019 Available online xxx

In this report, few-layer graphene particles (FLGPs) were synthesized through electrochemical e tion technique and were further reduced by reagents like hydrazine hydrate and ascorbic ac reduced FLGPs (RFLGPs) were characterized by XRD, FTIR spectrscopy, FESEM, and TEM. The pr RFLGPs were used as reinforcement with different concentration of 0.1 g/L, 0.3 g/L and 0.5 g/L in matrix to form Cu-RFLGPs composite by electrodeposition method. The morphological structu mechanical properties of Cu-RFLGPs composite films were characterized by XRD, SEM, EDS, A hardness analysis. The Cu-RFLGPs composite of 0.5 g/l RFLGPs shows 38% higher hardness as comp pure copper thin film. The corrosion behaviour of Cu-RFLGPs samples has also been analyzed b electrode cell setup. The corrosion rate of 0.5 g/L Cu-RFLGPs sheet shows 50% more corrosion res in 3.5% sodium chloride solution as compared to pure copper thin films and hence can be explore anticorrosive coating for sea water applications. © 2019 Elsevier B.V. All rights re

Keywords: Copper Graphene oxide Nano-composite Reduce graphene oxide Corrosion

1. Introduction Carbon materials such as carbon nanotube, graphite and graphene have been used as reinforcement with metal matrix and have improved strength, electrical and thermal conductivities. In comparison to other carbon materials graphene when used as reinforcement with metal matrixes have given superior properties [1e4]. Graphene, an allotrope of carbon discovered by Andre Geim and Konstantin Novoselov in the year 2004, is a single carbon layered and two-dimensional structure containing carbon atoms in the hexagonal lattice structure [5]. It exhibits outstanding properties such as large surface area of 2630 m2 g-1, high strength (130 Gpa), electron mobility (15000 cm2Ve1S1 ) and higher thermal conductivity of 5000 W/mK [6]. In recent years, graphene is used as reinforcement with copper and has enhanced the mechanical and thermal properties without any decrease its original electrical

* Corresponding author. Room No.-MS215 A, 769008, Odisha, India. E-mail addresses: [email protected] (A.K. Behera), ramkumarchandran33@ gmail.com (R. Chandran), [email protected] (S. Sarkar), [email protected] (A. Mallik). https://doi.org/10.1016/j.jallcom.2019.152713 0925-8388/© 2019 Elsevier B.V. All rights reserved.

conductivity [7e9]. In general copper metal is vastly in dema to its outstanding properties like thermal and electrical c tivity [10]. Copper can be used in seawater applications du corrosion resistance and antifouling properties [11]. Due t excellent mechanical and physical properties, copper and c based composites have been used as bearings, electrical contacts, and other engineering applications. Copper i combined with secondary metals and oxides such as Sn, S and graphite to produce composites with superior pro [12e16]. But these composites give enhanced mechanical p ties by sacrificing the electrical properties; hence graphene be the best alternative as a reinforcement material. Many exciting results have been reported by research groups on Copper-graphene (Cu-Gr) nano-com [7,9,11,17e29]. Y. Raghupathy et al. have synthesized graph ide (GO) particles by modified Hummers’ method and synth Cu-Gr composite by electrochemical deposition route [15 have electrodeposited Cu-Gr composite on steel substrate t yse corrosion resistance of composite and steel substra composite shows higher corrosion resistance as compared copper film and steel substrate in 3.5% NaCl solution. Aga have synthesized graphene particles by electrochemical exf

Please cite this article as: A.K. Behera et al., An exploration on the use of in-house synthesized reduced few layer graphene particl reinforcement during sono-electroplating of Cu matrix composite films, Journal of Alloys and Compounds, https://doi.org/10 j.jallcom.2019.152713

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A.K. Behera et al. / Journal of Alloys and Compounds xxx (xxxx) xxx

route and have electrodeposited Cu-Gr nano-composite. The prepared graphene particles when introduced as reinforcement with copper matrix was found to have increased corrosion resistance to 43% as compared to pure copper coating in 3.5% NaCl media [30]. Y. J. Mai et al. have electrodeposited reduced graphene oxide (RGO)/ Cu nano-composite by pulse electrodeposition route [ 31]. They have used surfactant free colloidal solution of copper (II)-ethylene diamine tetraacetic acid complex with graphene oxide. The GO particles converted in-situ to RGO particles and electrodeposited RGO/Cu composite through pulse current electrodeposition process. The RGO/Cu composites had 30% higher hardness (117HVe151HV) and decreased coefficient of friction (0.41e0.26) up to 35%e40% and wear rate decreased 10e18 times as compared to pure copper. To summarise, the nano-composites hence formed were analyzed for the change in electrical, mechanical and corrosion properties as per the specific applications. Furthermore, in our recently published work, it has been reported that Cu-Gr composite synthesized by electrodeposition route with few layered graphene particles have 31% higher hardness as compared to copper film with reduced electrical conductivity [ 32]. The graphene used in the study was electrochemically synthesized and were partially functionalized. The electrical properties of the composites were not good, which might have been due to the attached functional groups. Hence the current research is focused on to reduce the assynthesized graphene and explore the prepared Cu-Gr composite coating as an anti-corrosive protective coating on steel for seawater media. Here, we propose a chemical reduction of the in-house synthesized particles with Hydrazine hydrate and Ascorbic acid, which will be addressed as reduced few layered graphene particles (RFLGPs). Hydrazine hydrate is more toxic than ascorbic acid whereas Ascorbic acid is eco-friendly to the environment [33e35]. Furthermore, the synthesis of RFLGPs particles by Hydrazine hydrate and Ascorbic acid has similar properties. Hence Ascorbic acid has been significantly used as a reducing agent in many researches. However, in the present study both the reducing agents have been used to critically compare the evolution of properties. The reduced FLGPs are used as reinforcement with copper matrix to produce

composites by electrodeposition technique. Fig. 1 shows the var steps to synthesize, RFLGPs and Cu-RFLGPs composites. In previous research, synthesis of Cu-graphene composites by u as-synthesized FLGPs (which were partially functionalized unreduced) [32] had been reported where the main focus wa the effect of reinforcement on variation of mechanical properti the present research the obtained graphene particles have reduced and then incorporated in the matrix to monitor changes in the properties of the composites. In addition, corrosion behaviour of the composites has also been studied. 2. Experimental

FLGPs were prepared by electrochemical intercalation exfoliation technique. An aqueous solution was prepared by H2 SO4 with distilled water. A graphite sheet was used as cou electrode and another graphite sheet of exposed area 0.45 cm 2 used as a working electrode. Prior to exfoliation a cathodic treatment was given to the working electrode by applyi negative bias of 3 V for 10 min and further 10 V for 10 s. The treatment was given to remove any adsorbed impurities as we expansion of the graphite sheet to prepare it for the upcom intercalation stage. Then the working electrode was connecte the anode of the DC supply and a voltage of 0e8 V was applied a gradual increase of 0.5 V per 3 min. The electrode was hold a to complete the exfoliation of graphite particles. After the exf tion was completed, the flakes were collected and washed distilled water. The flakes were dispersed by performing u sonication for up to 3 h. The dispersed graphene particles w centrifuged at 4000 rpm for 40 min. Then the centrifuged graph was collected from the centrifuge and dried in the oven at a perature of 60  C for 24 h. The collected powder was as confir by different characterizations. The details of experimental se and final product can be followed in supporting docum (Figs. S1 and S2). Synthesized particles were reduced by chemical redu method with a suitable reducing agent. For the reduction pro 50 mg FLGPs was dispersed in100 ml distilled water and 0

Fig. 1. Schematic image of synthesis route of RFLGPs and Cu-RFLGPs nanocomposite. (a) Graphite plates,(b) Electrochemical exfoliation setup, (c) & (d) reduced few la graphene nano-particles, (e) electrolyte of Cu-RFLGPs composite synthesis, (f) Electrodeposition setup and (g) Cu-RFLGPs thin films.

Please cite this article as: A.K. Behera et al., An exploration on the use of in-house synthesized reduced few layer graphene particles reinforcement during sono-electroplating of Cu matrix composite films, Journal of Alloys and Compounds, https://doi.org/10.10 j.jallcom.2019.152713

A.K. Behera et al. / Journal of Alloys and Compounds xxx (xxxx) xxx

hydrazine hydrate was added to it and the solution was heated in a water bath at 100  C for 24 h. The obtained RFLGPs were washed four times with distilled water to remove any unwanted impurities. Then the washed particles were dispersed in distilled water by ultra-sonication to get RFLGPs(Hy) particles. Another reducing agent ascorbic acid was also used for the reduction of FLGPs. 50 mg of ascorbic acid was added with 50 mg FLGPs dispersed in 100 ml distilled water. Then the mixture was dispersed by using a magnetic stirrer for 2 h. After dispersion, the solution was filtered through filter paper (Grade 42, Retention 2.5 m m) and washed with distilled water. The RFLGPs thus obtained are called RFLGPs(Vc) particles. The mechanism of reduction can be explained as followed. Ascorbic acid is a mild reducing agent and antioxidant. It is oxidised with loss of one electron to form a radical cation and then loss of second electron to form dehydroascorbic acid. It reacts with oxidants of the reactive oxygen species, such as hydroxyl radical and separates it from the parent graphene network. Hydrazine is a convenient reducing agent and gives the by-product of nitrogen gas and water. The mechanism by which ascorbic acid and hydrazine reduce graphene oxide to reduced graphene oxide is presented below in Fig. 2. RFLGPs(Hy) and RFLGPs(Vc) particles were dispersed in acidic copper sulfate solution of 1 M CuSO4$5H2O. The RFLGPs(Hy) and RFLGPs(Vc) concentrations of 0.1, 0.3 and 0.5 g/L were added with the electrolyte for different Cu-RFLGPs composites. The pH of the electrolyte was maintained at a value of 1 by maintaining 0.9 M H2 SO4 (98% pure). The electrodeposition of RFLGPs(Vc) and RFLGPs(Hy) reinforced composite coatings were carried out at a temperature of 15  C [32] onto an oxygen free polished steel substrate of 316 grade stainless steel. The electrodeposition was carried out in presence of ultrasound for uniform distribution of reinforcements. A double water jacketed cell has been used to balance the temperature rise in the bath due to application of ultrasound. Sodium dodecyl sulfate (SDS, with 30 ppm concentration in the bath) was also added in the bath to act as a surfactant to reduce agglomeration of graphene particles during electrodeposition. The composite films were electrodeposited for 30 min with an applied potential of 2 V. After electrodeposition, the films were washed with double distilled water and were dried. Then the films were subjected to structural and morphological characterization. The X-ray diffraction pattern of RFLGPs, Cu-RFLGPs composite films were analyzed by Rigaku Ultima-IV system with Cu Ka

radiation ( a ¼ 1.5418 Å). The surface topography of RFLGPs p were examined by Field Emission Scanning Electron Micr (FESEM, NOVA nano-450) and Transmission Electron Micr (JEM 1200 JEOL, 200 KV). The topography of Cu and Cu- RFLG films were observed by Scanning Electron Microscopy (SEM JSM 6480 LV) and Atomic force microscope (Veeco di In Presence of graphene in the Cu- RFLGPs composite fil confirmed by the elemental analysis by energy-dispersiv trometer (EDS) attached with SEM. Mechanical properties films were first done by force displacement (FD) analy attachment with AFM, and the data was analyzed by us supplied software of Nano scope analysis. The hardness of th have been analyzed by Vickers microhardness tester (LECO L with a load of 25gf. The hardness value was taken of averag readings. The corrosion behaviour of composite sample wa studied in a potentiostat (Corr Test, CS 350) with a standar electrode system. In the electrochemical cell composite film exposed area of 0.6 mm 2 was used as working electrode, a pl rod as counter electrode and saturated calomel electrode (S reference electrode. The corrosion behaviour of composit analyzed in 3.5% sodium chloride solution at room tempe The open circuit potential (OCP) was recorded up to 30 m potential dynamic polarization was carried out in the ra potentials of 0.4 mv to 0.4 mv w.r.t OCP at a scan rate of 5m corrosion rate was analyzed by using Tafel plot analysis thro supplied software. 3. Results and discussion

3.1. Structural and morphological analysis of FLGPs and RFLG

Fig. 3 shows the structural and morphological st RFLGPs(Hy) and RFLGPs(Vc) through various techniques. T patterns of pyrolytic graphite (PGr), RFLGPs, RFLGPs(H RFLGPs(Vc) are presented in Fig. 3(a). The (002) diffraction p PGr particles was observed at a 2q angle of 26.34  . The inte the (002) peak of both FLGPs and RFLGPs particles ha decreased in comparison to PGr particles. There was no G present in 11 and it shows the absence of any oxygen fun groups in RFLGPs particles. Moreover the intensity of (002) p RFLGPs(Hy) and RFLGPs(Vc) has found to be decrease broadened as compared to FLGPs particles to values of 26.1

Fig. 2. Mechanism of reduced FLGPs by (a) Ascorbic acid and (b) Hydrazine hydrate.

Please cite this article as: A.K. Behera et al., An exploration on the use of in-house synthesized reduced few layer graphene particl reinforcement during sono-electroplating of Cu matrix composite films, Journal of Alloys and Compounds, https://doi.org/10 j.jallcom.2019.152713

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A.K. Behera et al. / Journal of Alloys and Compounds xxx (xxxx) xxx

Fig. 3. (a) XRD and (b) FTIR spectra of FLGPs and RFLGPs, FESEM image of (c) RFLGPs(Hy) (d) RFLGPs(Vc) and TEM image of (e) RFLGPs(Hy) and (f) RFLGPs(Vc).

26.17 respectively. The said observation may indicate that the number of layers in RFLGPs particles have been decreased due to the chemical reaction during reduction of FLGPs by the reducing agents. Fig. 3(b) shows FTIR spectra of FLGPs, RFLGPs(Hy), and RFLGPs(Vc) respectively for elemental and functional group confirmation. The peak position of FTIR spectra shows that the IR irradiations at 1712, 1400, 1212.85, 1077 and 613 cm 1 may be assigned to stretching of carbon/oxygen bond (C]O), carboxyl (CeOH), epoxide/ether (CeOeC), alkoxide/alkoxy (CeO). These observations confirm the oxygen functional groups presence in FLGPs. In RFLGPs(Hy) and RFLGPs(Vc) particles some functional groups disappeared and intensity of some peaks were reduced as compared to RFLGPs particles, hence confirming reduction by

hydrazine and ascorbic acid. Whereas a few functional groups still present in RFLGPs(Hy) and RFLGPs(Vc) particles, indicating the reduction is not 100%. The peak at 1577.7 cm1 may be assig to the aromacity of carbon bond (C]C) of graphene particles Fig. 3(c) and (d) shows the FESEM morphologies of RFLGPs and RFLGPs(Vc). The topography of RFLGPs particles confirm crumpled and folded morphology structure of reduced graph particles. The crumpled and folded morphology structur reduced graphene sheets are from the unreduced FLGNs. believe, it may be due the fact that during exfoliation the numb layers decreased from a high value to as low as 3 layers by intercalating ions. The stacking and because of oxygenation hydroxylation, the edges might have got crumpled and folded.

Please cite this article as: A.K. Behera et al., An exploration on the use of in-house synthesized reduced few layer graphene particles reinforcement during sono-electroplating of Cu matrix composite films, Journal of Alloys and Compounds, https://doi.org/10.10 j.jallcom.2019.152713

A.K. Behera et al. / Journal of Alloys and Compounds xxx (xxxx) xxx

is might have been originated by various defects and functional groups carrying sp3 hybridized carbon atoms, which are introduced during the oxidation process. Fig. 3 (e) and (f) shows the TEM image of RFLGPs(Hy) and RFLGPs(Vc) respectively. The graphene particles observed under TEM appear to be semi-transparent consisting of 3e5 layers under the electron microscope. The SAED pattern (inscribed in Fig. 3 e and f) showed strong diffraction spots with six-folded rotational symmetry. The diffraction rings clearly indicates the graphitic crystalline structure. 3.2. Analysis of Cu-RFLGPs composite films Fig. 4 shows the XRD analysis and texture coefficient of prepared copper Cu and Cu-RFLGPs films different concentrations of 0.1 g/L, 0.3 g/L and 0.5 g/L RFLGPs(Hy) and RFLGPs(Vc). We observed that in Cu-RFLGPs(Hy) and Cu-RFLGPs(Vc) there are no RFLGPs peaks present, but with increase in RFLGPs concentration, the intensity of the peaks have been decreased. The crystallite size of Cu, and CuRFLGPs composite films were measured by using Williamson-Hall formula and are presented in Table 1. The table also include the dislocation density and number of crystals calculated through equations (2) and (3).

bcos q ¼

kl þ 4ε sin q D

(1)

where k is the shape factor, l is the wavelength of the radiation

source, b is the full width half maximum, q is the Bragg’s ang the crystallite size and ε is the Internal strain respectively.

d¼

1 D2

where d is the dislocation density and D is the crystallite si

N¼

t D3

where N is the number of crystallites per unit area and thickness of composite film. Crystallite size of Cu and composites are in the ra 42e61 nm. Generally the change in size due to incorpora graphene may be due the fact that it has not allowed th growth and has act as a surfactant. Accordingly the varia dislocation density is also not significant. Furthermore the in of (111) planes at 2q ¼ 43.42⁰ has been decreased with incr RFLGPs concentrations in both Cu-RFLGPs(Hy) and Cu-RFL composite, and the intensity of peaks at 2q ¼ 74.23⁰ of the (220) was found to be increased particularly for Cu-RFLG films. The said observation indicates that there might hav textural growth of the copper metal matrix in a preferred di i.e. (220) plane. The textural coefficient (Tc) of crystalline , and of crystal planes were calculated following formula (4) and the values have been reported sh Fig. 4(c).

Fig. 4. XRD analysis of (a) Cu-RFLGPs(Hy) composites, (b) Cu-RFLGPs(Vc) composites and (c) Texture coefficient of ...