Integrated Computation and Experimental Investigation on the

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An Integrated Computation and Experiment Investigation on the Adsorption Mechanisms of Anti-Wear and Anti-Corrosion Additives on Copper Sang Xiong, Yunsong Li, Jianlin Sun, and Yue Qi J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b04460 • Publication Date (Web): 22 Sep 2017 Downloaded from http://pubs.acs.org on September 24, 2017

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The Journal of Physical Chemistry Submitted to The Journal of Physical Chemistry C

An Integrated Computation and Experiment Investigation on the Adsorption Mechanisms of Anti-Wear and Anti-Corrosion Additives on Copper Sang Xiong1, Yunsong Li2, Jianlin Sun1,* Yue Qi2, * 1

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China 2

Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing 48824, United States of America

ABSTRACT：：We integrated first principles calculations and surface characterization techniques to reveal a new molecular adsorption mechanism of anti-wear (dialkyl dithiophosphate ester, EAK) and anti-corrosion (2,5-bis (ethyldisulfanyl)-1,3,4 -thiadiazole, DTA) additives on Cu surface during rolling process. For direct comparison of modeling and experiments, Cu (110) surface was used in the model based on the strong (220) preferred orientation observed in the microstructures of the rolled copper foil. Density functional theory (DFT) calculations were performed to obtain the adsorption energy, optimized adsorption structures, and the charge transfer due to adsorption for EAK and DTA on Cu (110) surface. It was found that the anti-corrosion additive, DTA, decomposed and chemically adsorbed on Cu (110) surface strongly via multiple Cu-N and Cu-S bonds, while the anti-wear additive, EAK, adsorbed weakly due to one Cu-O bond. The predicted chemical bonds formation with Cu surface reasonably agreed with X-ray photoelectron spectroscopy (XPS) analysis. A new anti-corrosion mechanism, due to DTA decomposition and stronger chemisorption than EAK, was therefore proposed based on the simulation.

*Corresponding author: Yue Qi, E-mail: [email protected], Tel: 517-432-1243. Jianlin Sun, E-mail: [email protected], Tel: 86-1062333768.

1

ACS Paragon Plus Environment

The Journal of Physical Chemistry

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Submitted to The Journal of Physical Chemistry C

INTRODUCTION Lubricants are commonly used in machineries with moving parts in contacts (such as engines, gears, transmissions) and in metal forming and machining processes (such as drilling, rolling, cutting and stamping).1 Lubricant is a complicated oil system. On average, lubricating oil consists of ~93% base oil and ~7% chemical additives.2 Specific additives are added for designated functions, such as anti-wear and anti-corrosion. Anti-wear additives will prevent direct metal-to-metal contact between the running parts. Anti-corrosion additives are to decrease the corrosion rates of the metal (or alloy) parts. These chemical additives are absorbed onto metal surfaces through physical, chemical or mixture adsorptions. Some anti-wear functions are achieved due to additive decomposition. For example, zinc dialkyldithiophosphate (ZDDP) can be activated under the mechanical loads, along the normal and shear directions of the contacting surfaces. 3, 4 The functions of these additives are often correlated, rather than independent. In this study, pure copper rolling was taken as an example, since it is an important process to produce rolled copper foil (RCF) for many electronic devices, 5,6 as pure copper has the second highest electrical conductivity among metals.7 Similarly, lubricant composition plays important roles in the rolling process, the final surface quality, and the post-treatment processes.

2,8,9

Anti-wear additives are surfactants

added to the rolling oil to lower friction and to improve the lubricating performance during the rolling process.10 However, residual surfactants can cause oxidation and discoloration of the copper foil,11,12 and eventually lead to product corrosion. Furthermore, the electronically insulating oxides layer can decrease the electrical conductivity of RCF by 10%.13,14 In order to satisfy the high surface quality requirements of RCF products, it is necessary to reduce the surface oxidation during the rolling process. Thus, a suitable anti-corrosion additive is needed to protect the Cu surface against corrosion.15 It has been proposed that some anti-corrosion additives can lead to the formation of a nano-meter thick film,16 which acts as a protective barrier between the RCF surface and the environment,17,18 thus inhibits further corrosion. It is hypothesized that this anti-corrosion film is formed due to the 2


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interaction between the anti-corrosion additives and the metal surface.19,20 Therefore there are competing reactions and adsorptions among oxygen, base oil, anti-wear additives, and anti-corrosion additives on the surface of pure Cu in the rolling process. Deconvolution of these interface interactions will provide insights for lubricant additive design. Recently, many new experimental techniques such as scanning electron microscopy (SEM) with energy dispersive spectrometer21 and confocal laser scan microscopy22,23 have been applied to characterize and compare the surface morphologies with and without anti-corrosion additives. Furthermore, X-ray photoelectron spectroscopy24 and surface-enhanced Raman scattering (SERS) spectroscopy25 have been utilized to analyze the chemisorption state of the anti-corrosion film on the copper surface.26,27 Semi-empirical models, assuming physical adsorption of anti-corrosion additive molecules, have been used to illustrate the inhibition effectiveness of anti-corrosion additive on copper, but provided little insight into the actual corrosion inhibition mechanism.28,29 A more accurate and predictive adsorption model of anti-wear and anti-corrosion molecules on copper surface needs to be established in order to accelerate the design of additives. First principle calculations can predict the adsorption energy of molecules on metal surface accurately. As the first level of approximation, individual gas-phase additive molecule adsorption on copper surface was modeled at density functional theory (DFT) level.

20,30,31

These adsorption calculations pinpointed that the

anti-corrosion performance of some neutral molecules, 3-amino-1,2,4-triazole (ATA) and benzotriazole (BTA), is due to their ability to form weak N-Cu chemical bonds, with the chemisorption energies of -0.4 and -0.6 eV, respectively. Therefore, adsorption simulations have been used to evaluate the interaction of anti-corrosion additives with metal surface32,33 and ultimately can be used to screen new potential anti-corrosion additives.34,35 However, the mechanism of the competing effect of anti-wear additives and anti-corrosion additives on Cu surface is still unknown and direct validation of modeling predictions has not been achieved. In this work, we combined DFT-based adsorption modeling and experimental techniques for direct comparisons. First, an adsorption model is constructed based on 3



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experimentally determined additives and surface orientations. For example, it was found experimentally that dialkyl dithiophosphate ester (EAK), as one of the anti-wear additives, led to a higher corrosion rate of 27.5mpy. Adding 2,5-bis (ethyldisulfanyl)-1,3,4-thiadiazole (DTA), as one of the anti-corrosion additives, resulted in a lower corrosion rate, which was reported to be 19.6mpy. 22 Cu (110) surface was chosen for the adsorption model according to the X-ray diffraction data on the rolled copper foil. DFT simulations were carried out to predict the physicaland chemical- adsorptions of these two additives. The adsorption energies of different molecules onto Cu (110) surface were predicted, and the adsorption state was explained via electronic structure analysis. To validate the modeling results on the adsorption states, experimental characterization techniques, including X-ray photoelectron spectroscopy (XPS), were used to analyze the copper surface after rolling with anti-wear and anti-corrosion additives. This well integrated modeling and experimental approach will allow us to design new lubricant additives for metal manufacturing process.

EXPERIMENTAL TECHNIQUES AND COMPUTATIONAL DETAILS Raw materials of copper strips13 were rolled with designed lubricants to obtain the RCF samples. The sample cleaning contains three parts: the rollers, the raw material and RCF cleaning. Medical cotton with absolute ethyl alcohol and acetone were used to wipe the rollers and the raw material for five times, respectively. During the rolling process, 0.2 wt. % (% by weight) EAK (C9H21O6P) and 0.05 wt. % DTA (C6H10N2S5) were added to the base oil, which was sprayed onto the raw material surface. RCF samples were obtained after rolling for 5 minutes and 30 minutes. The surface of the samples were blotted with a filter paper, rinsed with absolute ethanol and immersed in an ultrasonic bath for 20 min in acetone to clear away the surface residual. RCF sample was studied by X-ray diffraction (XRD) analysis with a Rigaku DMAX-RB 12KW rotating anode diffractometer with Cu Ka radiation. A German model EVO 18 SEM was used to observe the microstructure of RCF surface. The elemental analysis of the chemical state of the surfaces was carried out by an SCALAB 250Xi X-ray 4


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photoelectron spectrometer (XPS) with MgKα radiation as the exciting source. The binding energies of the target elements were determined at a pass energy of 29.35 eV, with a resolution of about ±0.3 eV and the binding energy of the contaminated carbon (C1s: 284.8 eV) as the reference. Duplicate experiments were carried out for each test condition at room temperature, and different areas on each sample were profiled to ensure reproducibility of the measurements reported. All the calculations were performed using plane-wave DFT implemented in the Vienna Ab initio Simulation Package (VASP).36 The exchange-correlation functional was treated in the spin-polarized Generalized Gradient Approximation (GGA) as parameterized by Perdew-Burke-Ernzerhof (PBE)37 with the projected augmented wave (PAW)38 method. The standard version of the PAW potentials for Cu, C, H, O, N, P and S supplied with VASP is used. Convergence with respect to both energy cutoff and k-point mesh was tested. As a result of the convergence test, a plane wave cutoff of 600 eV was applied for all bulk and surface structures. A k-point mesh of (11 × 11 × 11) and (1 × 1 × 1) in the Monkhorst−Pack sampling scheme including the gamma point were used for bulk and surface supercell, respectively. Spin polarization was taken into account and the Methfessel–Paxton method was employed to determine electron occupancies with a smearing width of 0.1 eV in all cases. The vdW (van der Waals)-DF exchange-correlation functional was used for surface structures. This particular exchange-correlation functional is capable of capturing van der Waals interactions, which play an important role in surface adsorption. The convergence criterion for ionic relaxations was 10−6 eV/supercell and the Hellmann−Feynman force was converged to 0.01 eV/Å. For bulk Cu, the predicted lattice parameter is 3.624 Å, which agrees well with the available experimental data29 of 3.615 Å, confirming the choice of the parameters for DFT calculations. The clean Cu(110) surface was modeled by a slab consisting of five Cu atomic layers separated by the vacuum thickness of 30 Å. After examining the simulation cell size effect, a simulation cell of 6× 4 Cu (110) units was used. Ad-molecules and topmost three Cu atomic layers were fully relaxed till the force on the atoms was less than 0.01 eV/Å, while the other two Cu atomic layers were fixed to ensure a bulk behavior. 5



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In this paper, the gas-phase adsorption energy is defined as the interaction energy between the adsorbate molecule and the metal surface, as (1)

E a d s = E C u + M o lecu le − E C u − E M o lecu le

where Eads is the adsorption energy of molecule adsorbed on Cu(110) surface, ECu+molecule, ECu and Emolecule are the total energy of the optimized slab with molecule adsorbed on Cu (110) surface, the clean Cu (110) surface and the single molecule, respectively. It is defined that a negative adsorption energy Eads indicates the adsorption is more stable than the clean Cu (110) surface, a smaller adsorption energy means a stronger adsorption interaction between ad-molecule and surface and a more stable adsorption structure.

RESULTS AND DISCUSSION a. Atomic Structures Figure 1a shows the illustration of the experiments of rolling of copper foil (RCF) and Figure 1b shows the relaxed molecular structures of DTA and EAK. For confirmation, we compared the VASP predicted bond lengths with those listed in Cambridge structural database39 and predicted from Dmol3 calculations (a basic set DFT method with B3LYP/GGA/PW91) using the Materials Studio 7.0. These consistent bond-length results indicate that the computational method provides reasonable additive structures, which are reliable for the subsequent adsorption properties calculations. These comparisons are listed in Support Material Table S1. The obtained XRD image of the RCF is given in Figure1c. It revealed a very strong (220) preferred orientation parallel to the foil surface, in consist with the result reported by Yu et al.16 Therefore, Cu (110) surface was selected as Cu slab model, which is the most suitable to reflect the actual plastic deformation of Cu. Slab models with 5 Cu (110) layers along Z direction and (6 × 2) and (6 × 4) surface unit cells on X and Y directions were constructed. We calculated the intermolecular interaction energy between each two gas-phase molecules for these two sizes, to ensure the Cu slab model is large enough on X and Y directions. Table S2 gives the simulation cell 6


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size and the intermolecular interaction energy. The calculated results show that the intermolecular interaction energy between EAK is 0.025 eV for the (6 × 2) cell, which indicates that there is intermolecular repulsion. The intermolecular interaction energy of DTA is -0.140 eV for the (6 × 2) cell, which demonstrates intermolecular attraction. Both indicate that (6 × 2) simulation cell is not large enough to exclude self-interaction between the molecule and its images due to the periodic boundary condition. Therefore, the adsorption state is not mimicking gas phase adsorption. In the (6 × 4) simulation cell, the calculated intermolecular interaction of EAK and DTA molecules are 0.005 eV and 0.007 eV, respectively. We confirmed that the intermolecular interactions are small enough (less than 0.01eV) in (6 × 4) supercells and that is negligible in our adsorption energy calculations. Therefore, the Cu (110) surface with (6 × 4) unit cell was used for the following adsorption simulations. Figure 1d is the top view of Cu (110) (6x4) slab model.

Figure 1. Model system (a) Experimental illustration of rolling of copper foil (RCF); (b) the relaxed molecular structure of two representative additives, DTA and EAK; (c) XRD image of the RCF; and (d) the top view the Cu (110) slab model in a (6 × 4) supper cell. The simulation cell size is 15.374×14.484×35.125 Å, with 120 Cu atoms and 30 Å vacuum layers along Z direction. Some of the Cu atoms in the first two layers of the Cu slab model are labeled for reference and the dark and light orange colors represent the atoms in the top and second layer, respectively. 7



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The calculated relaxations for the clean Cu (110) surface interlayer spacing with respect to the bulk spacing show 10.4% contraction, 4.7% expansion, 1.5% contraction of the first, second and third interlayer spacing, respectively, which are consistent with the experimentally measured values of 11.8% contraction and 0.1% expansion of the first and second interlayer spacing,40 and the other GGA calculations with 9% contraction and 2% expansion41, respectively. It also suggests 5 Cu layers are thick enough to represent the surface properties of Cu. Finally, the adsorbed molecules were added to the Cu (110) slab model. To reduce the computational cost, we first used a simplified model with one Cu atomic layer to select the initial configurations of molecules and the initial adsorbed site. We considered several initial adsorbed angles and sites with the simplified model, optimized these configurations and then compared their total energy. We chose the most stable configuration with the lowest energy as the initial configuration on the five-layered full Cu (110) model.

b. Adsorption structures The adsorption properties of single EAK and DTA molecule in the gas phase on Cu (110) surface were studied. Figure 2a and 2d show the side view of the initial configuration of DTA and EAK on Cu (110) surfaces, respectively. The side view and top view of the fully optimization configurations for DTA and EAK adsorbed on Cu (110) surface are shown in Figure 2b, 2c, 2d and 2f. The bond distances are labeled as well. The adsorption energy is -0.50 eV and -3.59 eV for EAK and DTA, respectively, indicating EAK molecule chemisorbs weakly to the Cu (110) surface, whereas DTA chemisorbs strongly to the Cu (110) surface. The EAK molecule bonds to the Cu (110) surface with the one of the oxygen atom on the phosphate (-PO3) to the top site with the O atom, designated as atop-O5 adsorption mode, and the O5-Cu33 bond length is 2.04 Å. The DTA molecule has chemically decomposed into three parts, labeled as a, b, and c on Figure 2e. Part b contains the thiadiazole nitrogen atoms, which serve as the adsorption site in the atop-N1, N2 mode. The N1-Cu93 and N2-Cu96 bond lengths are 1.90 and 2.08 Å, respectively, which are close to Cu-N bond of 1.904 Å in 8


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Cu3N

42

. Part a and c bond with Cu via the S-Cu bonds, whose lengths range from

2.22 to 2.50 Å. In addition, S2 in part a bonds with Cu in a centered-S mode and S3 and S4 in part b and c bond with Cu via bridged-S mode, forming Cu-S bonds.

Figure 2. Adopted Structures. Relaxed EAK and DTA molecules on Cu(110) surface. The side view of the initial configuration for (a) EAK and (d) DTA; (b) side view and (c) top view of the fully optimization configurations for adsorbed EAK; (e) side view and (d) top view of the fully optimization configurations for adsorbed DTA. The number above each plot is the corresponding chemisorption energy and bond distances.

Due to the chemical adsorption, the Cu lattice is distorted. Table 1 lists some Cu-Cu bond distance change due to the chemical adsorption. Their atomic numbers are listed in Figure 1. B1 and B2 denote whether the Cu-Cu bond is within the top layer or across the top and the second layer, respectively. The largest displacement (△ D) of Cu-Cu bond (Cu33-Cu20) across the first two layers increased 0.92% after EAK adsorbed on Cu (110) surface. This is because Cu33 formed the O5-Cu33 bond due to 9



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EAK adsorption and it moved up 0.13 Å. The other Cu-Cu bond distance changed much less compare to this pair. It indicates that the adsorption on copper is the major factor that affects the Cu-Cu bonding. Since DTA decomposed into three parts and each adsorbed onto Cu (110) surface, many △D was over 5% due to DTA adsorption. In the first layer, the Cu atoms forming the Cu-S bonds moved up ~0.15 Å in average and those associated with Cu-N bonds moved up ~0.22 Å. The average displacements change of Cu-Cu bonds due to Cu-N bond formation is larger than that due to Cu-S bond formation, and both of them are larger than that due to Cu-O bond formation, indicating the interaction of Cu with DTA is larger than that of EAK, consistent with the adsorption energy.

Table 1 Typical Cu-Cu bond distances change due to additive adsorbed on Cu (110) surface and the associated bonds and bond length with surface Cu. (DInitial and DOptimized are the Cu-Cu bond distance before and after the additive adsorption, B1 and B2 indicate whether the Cu-Cu bond is within the surface Cu layer or between the first and second layers) Adoption system

Cu+DTA

Cu+EAK

Cu1-Cu2

Comment

DInitial /Å

DOptimized /Å

△D/%

Cu103-Cu40

B2

2.498

2.626

5.10

Cu103-Cu58

B2

2.498

2.753

10.19

Cu103-Cu108

B2

2.498

2.668

6.79

Cu93-Cu96

B1

2.562

2.697

5.25

Cu93-Cu70

B2

2.498

2.646

Cu93-Cu88

B2

2.498

2.707

Cu93-Cu98

B2

2.498

2.694

7.84

Cu66-Cu70

B2

2.498

2.693

7.79

Cu33-Cu16

B1

2.592

2.597

0.18

Cu33-Cu10

B2

2.544

2.551

0.25

Cu33-Cu20

B2

2.539

2.562

0.92

Cu33-Cu28

B2

2.551

2.550

-0.03

Cu33-Cu38

B2

2.548

2.563

0.62

Bond

Bonds

Bond lengths /Å

Cu103-S2

2.50

Cu103-S3

2.50

5.89

Cu93-N1

1.90

8.36

Cu96-N2

2.08

Cu66-S4

2.22

Cu33-O5

2.04

c. The decomposition and adsorption mechanism of DTA on Cu (110) surface The computed adsorption model provides new insights into anti-corrosion mechanisms and processes. The DTA anti-corrosion additive chemically decomposed 10


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and adsorbed on the Cu surface. Due to the lower bond energy of disulfide bonds, the polar S-S bonds will break in the adsorption process, such that DTA is decomposed into three parts, 1,3,4-thiadiazole-2,5-bis -(thiolate) (part b) and ethane thiolate (part a and c), as shown in Figure 2e. To summarize the total charge transfer due to the chemical adsorption of the three parts, Table 2 lists the atomic Bader charge on the adsorbed DTA and the total charge on the Cu slab. First, we note the Cu slab is losing electrons and becomes positively charged. Part a and c are ethanethiolates adsorbed on Cu surface via Cu-S bonds, due to the charge transfer from Cu to S, S2 and S4 gained ~0.4e and became negatively charged. The bond length of both S2-C3 and S4-C5 increased from 1.815Å (Table S1) to 1.836 Å. Meanwhile, there is no obvious charge transfer to the C atoms in part a and c during adsorption. Part b, 1,3,4-thiadiazole-2,5-bis -(thiolate), adsorbed on Cu surface via Cu-N and Cu-S bonds. S3, which bonded with Cu surface in part b, also gained ~0.40e. Since the Cu slab lost ~1.8e in total, besides the three S atoms gained electrons, there should be ~ 0.6e (=1.79-0.46-0.40-0.36) transferred to the N atoms. However, the two N atoms lost -0.03 and -0.16 electrons instead. This also means N atoms must pass the electrons to the N-C bonds. In fact, C1 gained ~1.57e due to the adsorption but C2 only gained ~0.19e. This is because C2 was bonded to S3, which was bonded to Cu. However, C1 was bonded to S3, which was dangling after DTA decomposition. To avoid the lone-pair electron, S5 gave ~1e to C1. Therefore, C1 gained ~1.60e in total.

Table 2 The Bader charge and its change (△Q) on the specified atoms before and after DTA adsorbed on Cu slab. Atom

Bonded atoms

S2

-C3-S2-Cu-

C3

Belongs to part (a, or b, or c) a

C4 S1

-C1-S1-C2-

S3

-C2-S3-Cu-

S5

-C2-S5-C1-

N1

-C1-N1-Cu-

b

Q’DTA

Q’Cu+DTA

△QDTA

-0.01

-0.47

0.46

-0.06

-0.03

-0.02

0.05

0.04

0

0.24

0.21

0.03

0.15

-0.25

0.40

0.12

1.18

-1.06

-1.90

-1.74

-0.16

11



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N2

-C2-N2-Cu-

-1.87

-1.84

-0.03

C1

-N1-C1-S1-

1.58

0.01

1.57

C2

-S3-C2-N2-

1.54

1.35

0.19

S4

-C5-S4-Cu-

-0.01

-0.37

0.36

-0.06

-0.06

0

C6

0.02

0.03

-0.01

Atoms

Q’∑Cu-slab

Q’∑Cu-slab+DTA

△QCu-slab

Cu-slab

+0.00

+1.79

-1.79

C5

c

d. SEM and XPS analysis To validate the DFT predicted chemical decomposition of DTA on Cu surface, high-resolution XPS spectra of the RCF surface rolled for 30 minutes in lubricants with EAK (only) and with DTA and EAK were analyzed, as shown in Figure 3a. To reveal the rolling effect, a shorter rolling time of 5 minutes with DTA and EAK additives were also performed. Analyzing the peak shift in the high-resolution XPS spectra provides a possible interpretation of the surface bonding change due to DTA addition. This interpretation is still qualitative, further investigations with more quantitative surface sensitive characterization methods are warranted. As well known, the Cu 2p XPS peaks at 928-938 and 952-957 eV correspond to the Cu 2p3/2 and Cu 2p1/2, respectively.

43

When only EAK was added in the base oil,

the Cu 2p spectrum consists of four peaks. The binding energy of the Cu 2p3/2 peak at 932.6 eV and Cu 2p1/2 peak at 952.5 eV are indicative of the Cu0 state in Cu metal and Cu+ state in Cu2O, which cannot be distinguished from each other due to almost the same peak location on the spectrum of Cu 2p.44 However, the Cu metal and Cu2O can be distinguished from the Cu LMM Auger region. As shown in Fig. 3a, the Cu LMM peaks for Cu metal and Cu2O exhibit peaks at the kinetic energy of 918.6 and 916.2 eV, respectively.45 The other low-intensity peaks Cu 2p3/2 at 934.1 eV and Cu 2p1/2 peak at 953.8 eV are attributed to the Cu2+ state in the CuO.45 Therefore, the oxidation and corrosion products of copper during the rolling process with EAK only are dominant by Cu2O and a little of CuO. When both DTA and EAK were introduced into the base oil within 5 min, the Cu2p peak set (Cu 2p3/2 and Cu 2p1/2) on the RCF sample surface already clearly split 12


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to two peak sets at 931.9 eV (Cu 2p3/2) and 952.3 eV (Cu 2p1/2) corresponding to Cu-S bond,

46

and at 933.1eV (Cu 2p3/2) and 952.6 eV (Cu 2p1/2) corresponding to Cu-N

bond,43 respectively. The sequence of these peak shifts for copper could be explained by the electronegativity of the elements, which is in the following order: O > N > S. It is easier for Cu to loss electrons to the element with larger electronegativity, resulting increased binding energy of the electron in Cu.47 Therefore, the sequence of binding energy of Cu 2p is Cu-O > Cu-N > Cu-S. When the rolling time is extended to 30 min, the peak values of Cu-N and Cu-S bonds shift to higher energy level, especially the binding energy of Cu

2p3/2

in Cu-N increase from 933.1 eV to 933.8 eV, suggesting

stronger interaction between Cu and N. This is likely due to the DTA decomposition. The possible mechanism of DTA decomposition will be discussed below. Similar findings were reported by Cosultchi et al.,48 who investigated the surface structure of copper sliding using petroleum and also by Mazalov and Semushkina,49 who analyzed adhesion of organic thin films on metal substrates. The peaks of O 1s observed at 530.0 and 531.1 eV correspond to oxygen in CuO and Cu2O,50 which are additional evidences of the presence of Cu2O and CuO on the RCF surface in rolling lubricants with EAK only. The remaining peaks correspond to oxygen with C-O and P-O in EAK.51 The O 1s peak is dramatically reduced when both DTA and EAK were used. The N 1s spectrum display two peaks, where the larger peak at 399.6 eV is considered as “organic nitrogen” and the smaller peak at 399.1 eV corresponds to the metal coordinated nitrogen.52 With increasing rolling time, the peak value of Cu-N bond shifts to lower energy level of 398.3 eV, which is close to Cu-N bond (398.2 eV) formed from chemisorbed dimethylamine on Cu(211) surface.53 The binding energy of N 1s in Cu-N bond decreases 0.8 eV in the rolling process with DTA additive. Combining with the binding energy shift of Cu 2p3/2 in Cu-N, it is evident that the interaction between Cu and N increased in the rolling process. More specifically, the Cu-N interaction changes from molecular DTA adsorbed on Cu surface to the Cu-N chemical bond formation, which could only occur if DTA is decomposed on Cu after rolling process. 13



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Considering S 2p signal has a 1.2eV spin-orbit splitting, the S 2p1/2 and S 2p3/2 have been fitted in the signal. The sulfur (S 2p) spectra obtained from the XPS analysis show peaks of binding energies of 162.4 eV (S 2p3/2), and 161.3 eV (S 2p1/2). The relative intensity ratio of 3/2:1/2 spin-orbit split components are 2:1 and both of them can be attributed to the Cu-S species, which come from the dissociation of disulfide bond. 54 The 163.4eV component and the 167.3 eV component to the organic C=S and C-S species 55, respectively. There are no N 1s and S 2p peaks when only using EAK as the additive. The high-resolution carbon (C 1s) spectra obtained from the XPS analysis show peaks of binding energies of 285.1 eV, 285.9 eV and 288.3 eV, corresponding to CH2, CH3 and C-O bond 56, respectively. Deconvolution of the C 1s of RCF surface showed the presence of CH2 (~285.1 eV), CH3 (~285.9 eV), C=S (~286.6 eV) and C-N (~285.4 eV) bond 53 with using DTA in the base oil.

Figure 3. Surface Characterization (a) Comparison of the XPS spectra of the RCF surfaces after rolling in lubricants with only EAK for 30 minutes, with DTA+EAK for 5 minutes, and with DTA+EAK for 30min. The SEM images of the raw RCF surface 14


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(b), rolling with (c) EAK and (d) EAK and DTA for 30 minutes. Based on the XPS analysis of the RCF surface in rolling oil with DTA, it was found that the peak intensity of oxygen element decreased, while the peak intensity with sulfur and nitrogen elements increased, carbon element kept the same in comparison with the case in absence of DTA. The atomic percentage of the sample surface also showed a similar trend. These results indicate that there is a strong adsorption on the metal surface of the additive or decomposed compounds containing nitrogen forming Cu-N and Cu-S bonds during rolling. The XPS analysis of the sample surface is in reasonable agreement with the DFT predictions. The strongly adsorbed decomposed DTA protects the Cu surface from oxidation. The surface morphologies of RCF after rolling with EAK and DTA additives after 30 minutes are given in Figure 3 b~d. There are irregular corrosion pits when rolling oil was absence of DTA. When only EAK is added, the EAK adsorbed on the surface via Cu-O bond, which was the root cause for oxidation and corrosion. It can be seen that the surface texture of the sample is clear after adding DTA. It confirmed that the protection of the RCF surface was achieved by chemical decomposition and strong adsorption of the DTA molecules on Cu surface. Based on the computational and experimental analysis, we propose the following new anti-corrosion mechanism provided by DTA as illustrated in Figure 4. Due to the lower bond energy of disulfide bonds, polar S-S bonds will break in the rolling process, and DTA decomposes into three parts, 1,3,4-thiadiazole-2,5-bis -(thiolate) (part b) and ethanethiolate (part a and c). Electrons will transfer from Cu to the adsorbed parts. The S atoms on ethanethiolate (part a and c) and one of the S atom at the end groups in 1,3,4-thiadiazole-2,5-bis(thiolate) (part b) become negatively charged. The two N atoms in 1,3,4-thiadiazole-2,5-bis -(thiolate) (part b) bond with Cu but pass the electrons from Cu to the C atom that connects to the dangling S. When N atoms bond with Cu, the C-N double bonds unfold 57 and become C-N single bonds. Electrons will also be transferred from S to C to and to N due to larger electronegativity of N, then form C=S double bond. Bond lengths of both N-N and 15



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C-N decrease from 1.382 Å to 1.371 Å and 1.316 Å to 1.310 Å, respectively. Due to the charge transfer, the surface of Cu is positively charged. The Cu-S and Cu-N bonds are likely ionic and covalent mixed bond, providing strongly chemical adsorbed states. This decomposition reaction is triggered by the Cu/DTA interaction.

Figure 4. Decomposition and adsorption mechanism of DTA on Cu (110) surface, illustrated based on (a) molecule reaction, (b) S-S bonds breaking and (c) Cu-N and Cu-S interfacial bonds formation. The total adsorption energy due to the three parts is ~-3.59eV. We also computed the adsorption energy from each part of the decomposed DTA. After relaxing each part, the adsorption energy on Cu (110) surface is in the order EDTA-a ≈ EDTA-c (-1.816 eV) < EDTA-b (-2.518 eV). The sum of the absolute values of the three parts is larger than the adsorption energy of DTA onto Cu (110) surface and the excess energy comes from the intermolecular interactions of the three portions. Adsorption energy of each part of the decomposed anti-corrosion molecule on Cu (110) surface is much lower than that of anti-wear molecule (EAK, -0.50 eV). Although we did not explicitly compute the adsorption of representative base oil molecules on Cu surface. It has been measured that they weakly adsorb on clean metal surface, specifically, each -CH2 group in an n-alkane molecule contributes ~-0.05 eV to the adsorption energy on clean Cu surface.58 Therefore the adsorption energy of long-chain hydrocarbons may be comparable to that of EAK, but still much less than the decomposed DTA. Therefore, the Cu (110) surface will be covered by the decomposed anti-corrosion molecules rather than by the anti-wear molecules or base-oil molecules. Thus, the surface is protected from future oxidation. 16


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CONCLUSIONS We have investigated the adsorption details of anti-wear (EAK) and anti-corrosion (DTA) additives on Cu (110) surface using DFT calculations and XPS characterization. DFT modeling suggests that the S-S bonds in DTA will break in the rolling process, and DTA will decompose into three parts, 1,3,4-thiadiazole -2,5-bis-(thiolate) (part b) and ethanethiolate (part a and c). We show the adsorption configuration is stable after DTA decomposes. Electrons will transfer from Cu to the adsorbed parts, according to the charge analysis, and form Cu-N, Cu-S bonds. A new detailed decomposition and adsorption mechanism for DTA on Cu surface is proposed. In comparison, EAK will adsorb on Cu (110) surface via a Cu-O bond without any decomposition. As a result, not only the total adsorption energy of DTA (-3.59 eV) is much larger than that of EAK (-0.50 eV), each decomposed part of DTA has stronger adsorption energy than EAK. Thus, the Cu (110) surface will be covered mainly by the decomposed anti-corrosion molecules (DTA) rather than by the anti-wear molecules (EAK), therefore preventing it from being corroded easily. XPS analysis of Cu foil surface rolled with DTA in the lubricants showed stronger Cu-N and Cu-S bonds and less Cu-O bonds, reasonably agreeing with DFT predictions. Thus, protection of the RCF surface is achieved by the chemical decomposition and strong adsorption of the DTA molecules on Cu surface.

ACKNOWLEDGEMENTS This work was financially supported by the National Natural Science Foundation of China (Grant No. 51474025). Computational work in support of this research was performed at Michigan State University’s High-Performance Computing Facility.

Supporting Information. The Supporting Information is available free of charge on the ACS Publications website at DOI: The detailed data are provided, including the relaxed molecular structure and bond length (Å) of DTA and EAK in VASP and Dmol3 calculations, and 17



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the simulation cell size effect on intermolecular interaction.

REFERENCES: 1

Byers., J.P. (second ed.) Metalworking Fluids; CRC Press: New York, U.S.A, 2006.

2 Dresel, T.M.A.W. (second ed.) Lubricants and Lubrication; John Wiley & Sons Inc Press: New York, U.S.A, 2007. 3 Mosey, N.J.; Müser, M.H.; Woo, T.K. Molecular mechanisms for the functionality of lubricant additives. Science 2005, 307, 1612-1615. 4 Onodera, T.; Kuriaki, T.; Morita, Y.; Suzuki A.; Koyama, M.; Tsuboi, H.; Hatakeyama, N.; Endou, A.; Takaba, H.; Del, C.A. Influence of nanometer scale film structure of ZDDP tribofilm on its mechanical properties: A computational chemistry study. Appl. Surf. Sci. 2009, 256, 976-979. 5 Hatano, T.; Kurosawa, Y.; Miyake, J. Effect of material processing on fatigue of FPC rolled copper foil, J. Electron. Mater. 2000, 29, 611-616. 6

Lee, C.Y.; Moon, W.C.; Jung, S.B. Surface finishes of rolled copper foil for flexible printed circuit board. Mat. Sci. Eng. A 2008, 483, 723-726.

7 Lu, L.; Shen, Y; Chen, X; Qian L.; Lu, K. Ultrahigh strength and high electrical conductivity in copper. Science 2004, 304, 422-426. 8 Evans, R. D.; Nixon, H. P.; Darragh, C. V.; Howe, J. Y.; Coffey, D. W. Effects of extreme pressure additive chemistry on rolling element bearing surface durability. Tribol. Int. 2007, 40, 1649-1654. 9

Neville, A.; Morina, A.; Haque, T.; Voong, M. Compatibility between tribological surfaces and lubricant additives — How friction and wear reduction can be controlled by surface/lube synergies. Tribol. Int. 2007, 40, 1680-1695.

10

Lenard, J.G. The effect of lubricant additives on the coefficient of friction in cold rolling. J. Mater. Process. Tech. 1998, 80, 232-238.

11

Carugno,

S.;

Chassaing,

E.;

Rosso,

M;

González,

G.A.

Enhanced

electrochemical oxidation of methanol on copper electrodes modified by electrocorrosion and electrodeposition. Mater. Chem. Phys. 2014, 143, 18


Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1012-1017. 12. Lei, X.; Sun, J.L.; Liu, N.N.; Xiong, S. Corrosion of rolling oil for rolled electronic copper foil. J. Mater. Protect. 2013, 43, 30-34. 13

Xiong, S.; Sun, J.L; Xu, Y.; Yan, X.D. Effect of lubricants and annealing treatment on the electrical conductivity and microstructure of rolled copper foil. J. Electron. Mater. 2015, 44, 2432-2439.

14

Qin, W.; Lei, B.; Peng, C.; Wu, J. Corrosion resistance of ultra-high purity porous alumina ceramic support. Mater. Lett. 2015, 144, 74-77.

15

Kovačević, N.; Milošev, I.; Kokalj, A. The roles of mercapto, benzene, and methyl groups in the corrosion inhibition of imidazoles on copper: II. Inhibitor– copper bonding. Corros. Sci. 2015, 98, 457-470.

16

Yu, B.; Woo, P.; Erb, U. Corrosion behaviour of nanocrystalline copper foil in sodium hydroxide solution. Scripta Mater. 2007, 56, 353-356.

17

Lawton, T. J.; Pushkarev, V.; Wei, D.; Lucci, F. R.; Sholl, D. S.; Gellman, A. J.; Sykes, E.C.H. Long range chiral imprinting of Cu(110) by tartaric acid. J. Phys. Chem. C 2013, 117, 22290-22297.

18

Sun, J.L.; Liu, N.N.; Xia, L.; Wu, D. Research of oil film thickness model and surface quality in cold rolling copper foil. Lubr. Sci. 2013, 26, 95-106.

19

Li, C.; Li, L.; Wang, C. Study of the inhibitive effect of mixed self-assembled monolayers on copper with SECM. Electrochim. Acta 2014, 115, 531-536.

20

Kokalj, A.; Peljhan, S.; Finšgar, M.; Milošev, I. What determines the inhibition effectiveness of ATA, BTAH, and BTAOH corrosion inhibitors on copper? J. Am. Chem. Soc. 2010, 132, 16657-16668.

21

Deyab, M. A.; Eddahaoui, K.; Essehli, R.; Rhadfi, T.; Benmokhtar, S.; Mele, G. Experimental evaluation of new inorganic phosphites as corrosion inhibitors for carbon steel in saline water from oil source wells. Desalination 2016, 383, 38-45.

22

Xiong, S.; Sun, J.L.; Xu, Y.; Yan, X.D. Inhibition effect of azole derivate on corrosion activity of copper in rolling oil. Surf. Interface Anal. 2016, 48, 88-98.

23

Merdan, T.; Kunath, K.; Fischer, D.; Kopecek, J.; Kissel, T. Intracellular processing of poly (ethylene imine)/ribozyme complexes can be observed in 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


living cells by using confocal laser scanning microscopy and inhibitor experiments. Pharm. Res. 2002, 19, 140-146. 24

Singh, P.; Srivastava, V.; Quraishi, M. A. Novel quinoline derivatives as green corrosion inhibitors for mild steel in acidic medium: Electrochemical, SEM, AFM, and XPS studies. J. Mol. Liq. 2016, 216, 164-173.

25

Karthigeyan, D.; Siddhanta, S.; Kishore, A. H.; Perumal, S. S.; Ågren H.; Sudevan, S.; Bhat, A.V.; Balasubramanyama, K.; Subbegowdac, R. K; Kundua, T. K.; et al. SERS and MD simulation studies of a kinase inhibitor demonstrate the emergence of a potential drug discovery tool. P. Nat. Acad. Sci. 2014,111, 10416-10421.

26

Yi, Z.; Tan, X.L.; Niu, G.; Xu, X.B.; Li, X.B.; Ye, X.; Luo, J.S.; Luo, B.C.; Wu, W.D.; Tang, Y.J., et al. Facile preparation of dendritic Ag-Pd bimetallic nanostructures on the surface of Cu foil for application as a SERS-substrate. Appl. Surf. Sci. 2012, 258, 5429-5437.

27

Durnie, W.H.; De Marco, R.; Jefferson, A.; Kinsella, B.J. In situ SERS study of the adsorption of inhibitors of carbon dioxide corrosion. Surf. Interface Anal.

2003, 35, 536-543. 28

Jamalizadeh, E.; Jafari, A.H.; Hosseini, S.M.A. Semi-empirical and ab initio quantum chemical characterisation of pyridine derivatives as HCl inhibitors of aluminium surface. J. Mol. Struct. 2008, 870, 23-30.

29

Xiong, S.; Sun, J.L.; Xu, Y. Adsorption behavior of thiadiazole as corrosion inhibitors on copper surface. Mater. Sci. Forum 2015, 817, 204-211.

30

Tafreshi, S.S.; Roldan, A.; Dzade, N.Y.; Leeuw, N.H.D. Adsorption of hydrazine on the perfect and defective copper (111) surface: A dispersion-corrected DFT study. Surf. Sci. 2014, 622, 1-8.

31

Gleason, N. J.; Greathouse, D. V.; Grant, C. V.; Opella, S. J.; Koeppe, R. E. Scale alpha and beta of quantitative convergence and chemical reactivity analysis in dual cholinesterase/monoamine oxidase inhibitors for the alzheimer disease treatment using density functional theory (DFT). J. Theor.Chem. 2013, 2013, 1-13. 20


Page 20 of 28

Page 21 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


32

Mert, B.D.; Mert, M. E; Kardaş, G.; Yazıcı, B. Experimental and theoretical investigation of 3-amino-1,2,4-triazole-5-thiol as a corrosion inhibitor for carbon steel in HCl medium. Corros. Sci. 2011, 53, 4265-4272.

33

Döner, A.; Solmaz, R.; Özcan, M.; Kardaş, G. Experimental and theoretical studies of thiazoles as corrosion inhibitors for mild steel in sulphuric acid solution. Corros. Sci. 2011, 53, 2902-2913.

34

Gajdoš, M.; Hafner, J. CO adsorption on Cu(111) and Cu(001) surfaces: Improving site preference in DFT calculations. Surf. Sci. 2005, 590, 117-126.

35

Gomes, J.R.B.; Gomes, J.A.N.F. A DFT study of the methanol oxidation catalyzed by a copper surface. Surf. Sci. 2001, 471, 59-70.

36

Sun, G.; Kürti, J.; Rajczy, P.; Kertesz, M.; Hafner, J.; Kresse, G. Performance of the Vienna ab initio simulation package (VASP) in chemical applicationsq. J. Mol. Struct. 2003, 624, 37-45.

37

Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77, 3865-3868.

38

Blöchl P.E. Projector augmented-wave method. Phys. Rev. B Condens. Matter.

1994, 50, 17953-17979. 39

Hu, Z. P.; Pan, B. C.; Fan, W. C.; Ignatiev, A. Structure analysis of the Cu(110)-(1×2) surface reconstruction induced by alkali-metal adsorption. Phys. Rev. B Condensed Matter 1990, 41, 41-45.

40

Lannoo, M.; Friedel, P. Atomic and Electronic Structure of Surfaces: Theoretical Foundations; Springer Series in Surface Sciences:Berlin, 1991; Vol.16, pp 68-82.

41

Li, W.; He, Q.; Pei, C.; Hou, B. Experimental and theoretical investigation of the adsorption behaviour of new triazole derivatives as inhibitors for mild steel corrosion in acid media. Electrochim. Acta 2007, 52, 6386-6394.

42

Juza, R.; Hahn, H. Über die kristallstrukturen von Cu3N, GaN und InN metallamide und metallnitride. Z. Anorg. Allg. Chem. 1938, 239, 282-287.

43

Ni, Y.; Chen, Z.; Kong, F.; Qiao, Y.; Kong, A.; Shan, Y. Space-confined synthesis of multilayer Cu-N-doped graphene nanosheets for efficient oxygen electroreduction. Dalton Trans. 2017, 46, 8586-8592. 21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


44

Bulushev, D. A.; Chuvilin, A. L.; Sobolev, V. I.; Stolyarova, S. G.; Shubin, Y. V.; Asanov, I. P.; Ishchenko, A. V.; Magnani, G.; Ricco, M.; Okotrub, A. V., et al. Copper on carbon materials: stabilization by nitrogen doping. J. Mater. Chem. A 2017, 5, 10574-10583.

45

Poulston, S.; Parlett, P. M.; Stone, P.; Bowker, M. Surface oxidation and reduction of CuO and Cu2O studied using XPS and XAES. Surf. Interface Anal.

1996, 24, 811-820. 46

Deroubaix, G.; Marcus, P. X-ray photoelectron spectroscopy analysis of copper and zinc oxides and sulphides. Surf. interface Anal. 2010, 18, 39-46.

47

Hitam, C. N. C.; Jalil, A. A.; Triwahyono, S.; Ahmad, A.; Jaafar, N. F.; Salamun, N.; Fatah, N. A. A.; Teh, L. P.; Khusnun, N. F.; Ghazali, Z. Synergistic interactions of Cu and N on surface altered amorphous TiO2 nanoparticles for enhanced photocatalytic oxidative desulfurization of dibenzothiophene. RSC Adv.

2016, 6, 76259-76268. 48

Cosultchi, A.; Rossbach, P.; Hernandez-Calderon. I. XPS analysis of petroleum well tubing adherence. Surf. interface Anal. 2010, 35, 239-245.

49

Mazalov, L. N.; Semushkina, G.I.; Lavrukhina, S.A.; Korotaev, E.V.; Boronin, A. I.; Gulyaev, R. V.; Basova T. V.

X-ray spectral and photoelectron study of

the electronic structure of copper phthalocyanine and its fluoro-substituted analog. J. Struct. Chem. 2012, 53, 1046-1055. 50

Biesinger, M. C.; Lau, L. W. M.; Gerson, A. R.; Smart, R. S. C. Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn. Appl. Surf. Sci. 2010, 257, 887-898.

51

Hussein, A.; Devillanova, F.A.; Isaia, F.; Verani, G. Copper(I) complexes with N-methylbenzothiazole-2-thione and -2-selone. Transit. Metal Chem. 1985, 10, 368-370.

52

Volosskiy, B.; Fei, H.; Zhao, Z.; Lee, S.; Li, M.; Lin, Z.; Papandrea, B.; Wang, C.; Huang, Y.; Duan, X. Tuning the catalytic activity of a metal–organic framework derived copper and nitrogen Co-doped carbon composite for oxygen reduction reaction. ACS Appl. Mater. Interfaces 2016, 8, 26769-26774. 22


Page 22 of 28

Page 23 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


53

Davies, P. R.; Keel, J. M. Intermolecular migration of methyl groups at a Cu(211) surface. Catal. Lett. 1999, 58, 99–102

54

Healy, P.C.; Myhra, S.; Stewart A.M. XPS Studies of planar four-coordinate copper(II) and copper(III) complexes. Journal: JPN. J. Appl. Phys. 1987, 11, 1884-1887.

55

Lindberg B. J., Hamrin K.; Johansson, G.; Gelius, U.; Fahlman, A.; Nordling, C.; Siegbahn K. Molecular spectroscopy by means of ESCA. II. Sulfur compounds. Correlation of electron binding energy with structure. Physica Scripta. 1970, 1, 286-298.

56

Leadley, S.R.; Watts, J.F. The use of XPS to examine the interaction of poly (acrylic acid) with oxidized metal substrates. J. Electron Spectrosc. 1997, 85, 107-121.

57

Feng, L.; Yang, H.; Wang, F. Experimental and theoretical studies for corrosion inhibition of carbon steel by imidazoline derivative in 5% NaCl saturated Ca(OH)2 solution. Electrochim. Acta 2011, 58, 427-436.

58

Sexton, B.A.; Hughes A.E. A comparison of weak molecular adsorption of organic molecules on clean copper and platinum surfaces. Surf. Sci. 1984, 140, 227-248.

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TOC Graphic

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Figure 1. Model system (a) Experimental illustration of rolling of copper foil (RCF); (b) the relaxed molecular structure of two representative additives, DTA and EAK; (c) XRD image of the RCF; and (d) the top view the Cu (110) slab model in a (6 × 4) supper cell. The simulation cell size is 15.374×14.484×35.125 Å, with 120 Cu atoms and 30 Å vacuum layers along Z direction. Some of the Cu atoms in the first two layers of the Cu slab model are labeled for reference and the dark and light orange colors represent the atoms in the top and second layer, respectively. 88x65mm (300 x 300 DPI)



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Figure 2. Adopted Structures. Relaxed EAK and DTA molecules on Cu(110) surface. The side view of the initial configuration for (a) EAK and (d) DTA; (b) side view and (c) top view of the fully optimization configurations for adsorbed EAK; (e) side view and (d) top view of the fully optimization configurations for adsorbed DTA. The number above each plot is the corresponding chemisorption energy and bond distances. 367x302mm (300 x 300 DPI)


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Figure 3. Surface Characterization (a) Comparison of the XPS spectra of the RCF surfaces after rolling in lubricants with only EAK for 30 minutes, with DTA+EAK for 5 minutes, and with DTA+EAK for 30min. The SEM images of the raw RCF surface (b), rolling with (c) EAK and (d) EAK and DTA for 30 minutes. 1214x892mm (96 x 96 DPI)



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Figure 4. Decomposition and adsorption mechanism of DTA on Cu (110) surface, illustrated based on (a) molecule reaction, (b) S-S bonds breaking and (c) Cu-N and Cu-S interfacial bonds formation. 335x109mm (300 x 300 DPI)


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Integrated Computation and Experimental Investigation on the

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