Corrosion Of Cu Research Articles

CuSx Catalysts by Ag-Mediated Corrosion of Cu for Electrochemical Reduction of Sulfur-Containing CO2 Gas to HCOOH

CuS_x Catalysts by Ag-Mediated Corrosion of Cu for Electrochemical Reduction of Sulfur-Containing CO₂ Gas to HCOOH

Synthesis of tolyl guanidine as copper corrosion inhibitor with a complementary study on electrochemical and in silico evaluation

A rapid and new synthetic route for N,N′-di-o-tolyl guanidine (DTG) synthesis from cheap materials is reported. The performance of DTG as an excellent inhibitor for delaying copper (Cu) corrosion with an efficiency higher than 98% at 20 × 10−6 M in an acidic solution was investigated via electrochemical measurements. These measurements included PDP, EFM, and EIS spectroscopy. The experimental data indicated that DTG has an efficient inhibiting effect on the corrosion of Cu in acidic media.The DTG was adsorbed on to the Cu surface via chemical adsorption and followed the Langmuir route. The PDP measurements revealed that DTG acted as a mixed inhibitor. Furthermore, EIS data showed that the DTG adsorbed through the metal/electrolyte interface. This resulted in forming a DTG protective layer on the Cu surface, thereby impeding the dissolution of Cu in the acidic solution. The corrosive solution containing the DTG inhibitor after immersion of the Cu specimen for 48 h, which promoted the formation of a complex between the Cu cation and DTG, was investigated via ultraviolet/visible spectroscopy. In addition, the formation of a DTG protective layer on the Cu surface was confirmed via scanning electron microscopy and atomic force microscopy analysis of the Cu surface morphology. Moreover, the active centers for interaction with the Cu surface in an acidic solution were investigated via in silico evaluation of DTG.

Surface photodynamic ion sterilization of ITO-Cu2O/ZnO preventing touch infection

• An ITO-Cu 2 O/ZnO heterojunction was constructed on ITO conductive glass by electrodeposition and atomic layer deposition. • The photocatalytic ability of ITO-Cu 2 O/ZnO was enhanced due to the formation of p-n junction. • The ITO-Cu 2 O/ZnO exhibited efficiently bacteria-killing under solar light irradiation for 3 min. • The coating of ZnO had a protective effect on the water corrosion of Cu 2 O and prolonged the service life of the hybrid film. Pathogenic microbial infections are threatening the people's health and even life. The most common channel of infections can be caused by skin contact, especially hand touching facilities such as touching screen. In this work, Cu 2 O covered with ZnO nanofilm was prepared on the surface of indium tin oxide conductive glass by electrodeposition and the followed atomic layer deposition process. This composite coating had a light transmittance of 71.5%, which met the light transmission needs of touch screen device. Electron spin resonance spectra showed that composite materials can generate more reactive oxygen species (ROS) than a single component under solar light irradiation. This was because a p-n junction with a built-in electric field was formed at the interface after Cu 2 O contacting with ZnO. In the process of photocatalysis, photogenerated electrons and holes migrated at the interface driven by the built-in electric field, which promoted the separation of carriers. The antibacterial rate against Staphylococcus aureus reached 92.5% after 3 min of light irradiation with simulated sunlight due to the synergy of ROS and Cu ions, Zn ions. Therefore, this work may provide a potential method for antibacterial application of preventing hand touch infections.

Corrosion of Cu in Antifreeze Solutions with Triazine- or Triazole-Type Corrosion Inhibitors for 3 Weeks

The corrosion behavior of Cu in antifreeze solutions containing 2,4,6-Tris(5-carboxypentylamino)1,3,5-triazine, 2,4,6-Tris(11-carboxyundecylamino)1,3,5-triazine, 1-Aminomethyl(N′,N′-di(2-hydroxyethyl)tolutriazole, or 1-Aminomethyl(N′,N′-di(2-hydroxyethyl)benzotriazole as corrosion inhibitors were examined by immersion test for 3 weeks as well as potentiodynamic polarization tests before and after immersion test. The corrosion rate of Cu was as relatively high as 10−5 A/cm2 in antifreeze solution with the inhibitor (2,4,6-Tris(11-carboxyundecylamino)1,3,5-triazine) with a high molecular weight of 713 for a short time duration compared with antifreeze solutions using the other three types of inhibitors. However, the corrosion inhibition effect of this large molecule became prominent after 2 weeks, reducing the corrosion rate by about four orders of magnitude. Corrosion of Cu in the solution with inhibitors of high molecular weight of 440 or higher decreased gradually with time, while that in the solution with small molecules slightly increased over 3 weeks.

Passiflora edulia Sims leaves Extract as renewable and degradable inhibitor for copper in sulfuric acid solution

In this research, we obtained Passiflora edulia Sims leaves Extract (PESLE) using a simple and green pure water extraction method. Experiment and theoretical calculations data show that PESLE can effectually restrain Cu corrosion in H2SO4 medium. Electrochemical results demonstrate that the PESLE is 800 mg/L, its anti-corrosion nature can reach about 96%. And with the augment of temperature, the anti-corrosion capacity of PESLE can still reach about 95% at a temperature of 318 K. SEM and AFM morphology test data show that PESLE is adsorbed onto the copper interface, the copper sample is effectively protected and the surface becomes relatively flat. The morphology test results directly prove that PESLE efficaciously restrain the corrosion of Cu in H2SO4 environment. XPS test results show that PESLE adsorption onto the Cu interface can detect Cu-N bond, which proves that chemical adsorption occurs. Quantum chemistry calculation data manifest that the three components of PESLE can reveal high anti-corrosion property. Molecular dynamics simulation data manifest the three components of PESLE can be adsorbed at the Cu (111) surface with paralleled way, and can have a large binding energy.

Microbiologically influenced corrosion of Cu by marine ammonifying Alcaligenes aquatilis bacterium

In this work, we studied the microbiologically influenced corrosion mechanism of Cu by marine ammonifying bacterium Alcaligenes aquatilis. Through immersion experiments, we found that A. aquatilis could accelerate the corrosion rate of copper, resulting in the development of pits. In the presence of A. aquatilis, the morphology and composition of the corrosion products differed from the abiotic samples, and we found that Cu2O was the main corrosion product. By analyzing the biotic medium and experimental NH3 addition, we verified that NH3 was the main component that intensified copper corrosion. Furthermore, we found that NH3 played a catalytic role in the corrosion of Cu in the presence of A. aquatilis.

Influence of nutrition on Cu corrosion by Desulfovibrio vulgaris in anaerobic environment

The eutrophication of seawater is not only harmful to the environment, but also influence microbes’ proliferation and then influence biocorrosion of marine engineering materials to a great extent. This study investigated the microbiologically influenced corrosion (MIC) of Cu immersed in the Desulfovibrio vulgaris (a sulfate reducing bacterium) medium with four defined nutritional degrees: total nutrition, P lacking, N lacking, and P&N lacking. When D. vulgaris was cultured in more nutritional medium, more H2S was generated and more serious corrosion of Cu occurred. The concentration of H2S corresponding to the medium with total nutrition was as high as 4.9 × 104(±913.0) ppm. The weight loss of Cu in medium with total nutrition increased by at least 50% compared with other nutritional conditions. The depth of pitting pits on Cu increased obviously with more abundant nutrient elements N and P. The electrochemical tests supported the weight loss and also showed that an obvious passivation zone was formed on the anodic polarization curve. This indicated that a protective film was formed on the surface of Cu against uniform corrosion. The analyses of thermodynamics and experiment data indicated that metabolite MIC (M-MIC) account for the Cu corrosion by D. vulgaris.

Corrosion Inhibition of Copper in Acidic Solution by using a Natural Product as Henna Extract (Lawsonia inermis L).

The dissolution of the copper in naturally aerated HCl solution is studied at different acid concentrations using open circuit potential measurements, weight loss measurements, and galvanostatic polarization techniques. The rate of corrosion of the metal depends on acid concentration. Henna leaves (Lawsonia inermis L) extract is used as a naturally corrosion inhibitor for the corrosion of Cu in 0.5 M HCl solution. The inhibition efficiency of the henna extract depends on its concentration. Lower concentrations of the extract (2-4%) cause slight effect on metal dissolution. In presence of 6% of the extract, a competitive process occurs between metal dissolution and metal inhibition. However, higher concentrations of the extract 10% caused marked inhibition of the metal (58.7%). Inhibition of Cu dissolution in HCl solutions is assumed to be due to the formation of a Cu2+ - Lawsone complex on the anodic sites and the possible precipitation of Cu(OH)2 on the cathodic sites of the metal surface.

One-step electrochemical deposition leading to superhydrophobic matrix for inhibiting abiotic and microbiologically influenced corrosion of Cu in seawater environment

Finding efficient ways to prohibit abiotic and microbiologically influenced corrosion is a critical task for metal serving in harsh seawater environment. In this paper, originated from the biomimetics principle, a lotus leaf inspired superhydrophobic matrix composed by Fe-myristic acid compound is prepared on copper surface. The preparation is realized by a facile electrodeposition approach based on a coordination-deposition mechanism, which leads to porous structure composed of hydrophobic compound from an ethanol bath via a single step. The dependent relationship between wettability and electrodeposition conditions including electrodeposition potential and time is revealed. Sophisticated techniques including scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier Transform infrared spectroscopy are employed to characterize the matrix morphology and composition. Scanning Kelvin probe and other electrochemical methods show that superhydrophobic matrix improves the corrosion resistance capability of copper in different environments including atmosphere, natural seawater and salt spray, illustrating that superhydrophobic matrix endows high abiotic corrosion inhibition to the underneath Cu metal. The inhibition efficiency of Cu by superhydrophobic coating can reach 99.85 % after immersion in seawater for 28 days. For achieving high prohibition effect to the corrosion induced by microbes, the bio-adhesion inhibition is one prerequisite. The as-obtained superhydrophobic matrix is confirmed to prohibit the representative diatoms and sulfate reducing bacteria (SRB) to grow onto metal surface due to the limited anchoring sites and the low surface energy. Superhydrophobic matrix exhibits excellent corrosion resistance in harsh SRB suspension, demonstrating a prominent role to combat microbiologically influenced corrosion in seawater environment.

Improvement of Data Retention Characteristics By Inserting Ta Adhesion Layer to Ionic Liquid-Supplied Conducting-Bridge Memory

Previously, we reported on the memory characteristics of ionic liquid-supplied conducting-bridge random access memory (IL-CBRAM)1. IL-CBRAM is a kind of CBRAM devices in which ionic liquid (IL) is confined in an artificially formed pore in the SiO2 layer of Cu/SiO2/Pt stuck structure. The resistive switching phenomenon is caused by formation and rupture of Cu filaments consisting of electrochemically eluted Cu from the Cu electrode (EL). Although IL-CBRAM has excellent features such as reduction of operating voltages and their variations, there is a serious problem that IL addition makes data retention in low resistance state (LRS) poor. When two metals with different EL potentials (EPs) are in contact in the presence of solvents, it is known that the corrosion of the metal with lower EP proceeds. Therefore, we considered that the abovementioned problem of poor data retention might come from the configuration of LRS itself, that is, the configuration that Cu filaments with low EP directly contact to Pt-EL with high EP.In this study, we demonstrated that data retention characteristics in LRS were drastically improved by inserting the Ta adhesion layer between the SiO2 and Pt-EL. It was suggested that the Ta layer that had lower EP than those of both Cu and Pt provided electrons to Pt-EL, suppressing the corrosion of Cu filaments.Figure 1(a) shows the schematic diagram of IL-CBRAM device. IL-CBRAM has a stack structure of Cu (50 nm)/Cu- or Ag-IL (30 nm)/Pt (20 nm), and IL was supplied to an artificially introduced pore with the diameter of 1 μm in SiO2 layer. Here, Cu- and Ag-IL are 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide ([bmim][Tf2N]) solution containing 0.4 M Cu(Tf2N)2 and 0.4 M Ag(Tf2N), respectively2. The Ta layer with the thickness, d, of 1 nm or 5 nm is inserted as an adhesion layer between the SiO2 and Pt layers. Figures 1(b) and (c) show schematics when filaments are formed in IL-CBRAM at d = 1 and 5 nm, respectively. Cu filaments were observed to be formed on the wall surface of the pore that was introduced in the SiO2 layer1. Since the hole penetrates not only the SiO2 layer, but also the Ta layer, the Cu filament contacts both the Pt and Ta layers.Figure 2 shows data retention characteristics of IL-CBRAM in LRS, for d = 1 and 5 nm. The compliance current to prevent excessive growth of filament was set to 200 μA. Data retention time is less than 103 s for d = 1 nm, whereas more than 104 s for d = 5 nm (still working). After formation of Cu filaments connecting the Cu- and Pt-ELs, the corrosion of Cu filaments with lower standard EP (SEP) should proceed, because of large difference of SEPs between Cu (0.34 V) and Pt (1.2 V). The drastic improvement of the retention characteristics for d = 5 nm suggests that the insertion of the Ta layer that has lowest SEP of -0.81 V provides electrons to Pt instead of Cu, suppressing the corrosion of Cu filaments. On the other hand, the Ta layer with d = 1 nm is considered to be oxidized completely during the SiO2 deposition (Fig. 1(b)) in contrast to a case of thicker d of 5 nm (Fig. 1(c)). The completely oxidized Ta layer no longer provide electrons and cannot contribute to an improvement of data retention. It is also important that the surface of Ta layer except for the interface with Pt is oxidized for the 5 nm thick Ta layer. This prevents corrosion of the Ta layer itself. Acknowledgement This work was supported by NAGASE & CO., LTD. Colors & Advanced Processing Dept. Reference [1] H. Sato, et. al., 14th IEEE NMDC, Stockholm, Sweden, program booklet, pp.171-172, 1698674, Oct. 27-30, 2019.[2] A. Harada, et. al., J. Mater. Chem., 4, pp. 7215-7222 (2016). Figure 1

The synergistic inhibitory effect and density functional theory study of 2,2’-[[(Methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol and potassium oleate on copper in H2O2 based alkaline slurries

Copper (Cu), during the chemical mechanical polishing (CMP) of barrier layer, was associated with several challenges, one of which is to screen slurries required to address the corrosion of Cu. A large number of CMP studies have proved the effectiveness of inhibitors on Cu, but the passivation mechanism is not clear from the perspective of atoms, which needs further confirmation by computational chemistry. In this study, 2,2’-[[(Methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol (TT-LYK) and potassium oleate (PO) as inhibitors for Cu were widely investigated by experimental and density functional theory (DFT) methods. The CMP experiments and potentiodynamic polarization data showed that both of them were mixed - type corrosion inhibitors with significant corrosion inhibition ability on Cu. Besides, the combination of TT-LYK and PO exhibited excellent performance in suppressing the Cu corrosion, which were well prove by the surface morphology, single frequency electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) measurements. In addition, DFT calculation show that TT-LYK and PO were adsorbed on the Cu surface by the Cu-N bonds and Cu-O bonds at the bridge site, respectively, thereby obtaining the most stable configuration. This work is conducive to elucidate the role of corrosion inhibitors from a micro level.

Study of Corrosion Mechanism in Brazed Cu Joints

The mechanism behind corrosion of Cu and Cu alloys has been the subject of extensive studies within their applications in various engineering components. These studies explore the electrochemical mechanisms along with the contributing factors impacting the corrosion behaviors such as pH, temperature, and solution chemistry. Thanks to these studies, the corrosion behavior of Cu and Cu alloys is reasonably well understood to a degree to predict their reliability under conditions that have been a concern of related industries. However, it is noted that studies are very limited to the impact of a microscopic structure that forms a galvanic pair with Cu and Cu alloys. One of the most obvious but least studied examples of such a case is the corrosion located in the joint that is created by brazing material. The Cu or Cu alloy components with a brazed joint is commonly found in water handling devices and facilities (such as a heat exchanger). Since the filler material used for the brazing of Cu and Cu alloys contains a substantial number of elements other than Cu the joint changes chemically and microstructurally different. It then becomes a source of a galvanic couple. In this case, the most corrosion prone part is the area near or at the joint as the corrosion is accelerated by the galvanic potential. While such joints are abundantly placed in various engineering components (and therefore the concern for corrosion should be focused more on those parts), studies on the corrosion mechanism with the brazing joint are extremely limited. This is probably due to sufficient material redundancy in the joint and thus causing immunity to failure by corrosion. However, a recent development of an advanced cooling system, where heat from electronic devices such as a microcontroller is removed by the use of recirculating coolant, the redundancy is no longer valid and the corrosion at the brazed joint becomes a matter of critical and practical concern.Motivated by the growing need to better understand the corrosion mechanism active in advanced cooling system, we have investigated the nature of corrosion in Cu plate with a variation in filler materials (Cu-Ag eutectic alloy, Cu-Ag-P alloys), liquid type (water, water mixed with PG), and temperatures. One of the most challenging part of our investigation is the fact that there are multiple sources of galvanic potential due to the existence of multiple phases in the sample. For example, when a Cu-Ag-P alloy was chosen as a filler material, the joint contained three phases, Cu-rich, Ag-rich and Cu3P intermetallic phases. An example of such a microstructure is shown in Fig.1, where an SEM micrograph of the joint is displayed. In this case, the galvanic potential exists not only between the filler materials as a whole and the surrounding Cu, but also among these three phases. In order to overcome the difficulty of studying corrosion behaviors in such a structure, we adapted two different experimental approaches. The first is to measure the corrosion current under the configuration of ZRA (zero-resistance-analysis). The ZRA uses the Cu and the joint as the counter/working electrode as shown in Fig.2 and measures the galvanic potential and current across the joint. The second is to make a mini-galvanic cell consisting of a pure Cu plate and a Cu plate with the brazed part. Spaced by an O-ring, these two plates are forced to make a galvanic cell with a liquid filled the gap and an external short circuit. We were able to measure the resulting corrosion current, direction and the amount of which can be related to the galvanic corrosion created by the braze.This study presents some of our highlighting findings suggesting that the galvanic corrosion can be better characterized by the use of techniques employed in our study. An example of such evidence can be found in Fig.3 where the ZRA scan signal (voltage and current) in 1M KCl solution is shown with the filler area as the working and surrounding Cu as the counter electrode. Note the instability in the galvanic potential with time, which is attributable to the lack of sustainable passivation layer on top of Cu3P and is responsible for the complex corrosion response of the brazed part to the solution chemistry. A detailed description of such findings along with theoretical explanation will be provide in this paper. Figure 1

Inhibition of 2-phenyl imidazoline on chloride-induced initial atmospheric corrosion of copper by quartz crystal microbalance and electrochemical impedance

Initial atmospheric corrosion of clean copper and NaCl-deposited copper was investigated by quartz crystal microbalance and electrochemical impedance spectroscopy. 2-phenyl imidazoline (2-PI) exhibits increasing inhibition efficiency with temperature on chloride-induced atmospheric corrosion of Cu. However, on the NaCl-deposited Cu, adsorption amount of 2-PI is much higher than that on clean Cu possibly due to that rough corrosion products entrap lots of 2-PI molecules. The adsorption of 2-PI on corroded Cu is suggested to obey a capillary condensation and entrapment mechanism, but in dry argon atmosphere, it obeys a simple pseudo first-order model for lack of corrosion products.

Microbiologically influenced corrosion of Cu by nitrate reducing marine bacterium Pseudomonas aeruginosa

The microbiologically influenced corrosion (MIC) mechanisms of copper by Pseudomonas aeruginosa as a typical strain of nitrate reducing bacteria (NRB) was investigated in this lab study. Cu was immersed in deoxygenated LB-NO3 seawater inoculated with P. aeruginosa and incubated for 2 weeks. Results showed that this NRB caused pitting and uniform corrosion. The maximum pit depths after 7 d and 14 d in 125 mL anaerobic vials with 50 mL broth were 5.1 μm and 9.1 μm, accompanied by specific weight losses of 1.3 mg/cm2 (7 d) and 1.7 mg/cm2 (14 d), respectively. Electrochemical measurements corroborated weight loss and pit depth data trends. Experimental results indicated that extracellular electron transfer for nitrate reduction was the main MIC mechanism and ammonia secreted by P. aeruginosa could also play a role in the overall Cu corrosion process.

Compositing fluid infused in superhydrophobic Cu(OH)2 nanoneedle matrix to inhibit abiotic and microbiologically induced corrosion of Cu in seawater environment

Although superhydrophobicity (SHP) and liquid infused surface (LIS) bio-inspired by the lotus leaf and pitcher plant have afforded high corrosion inhibition to metals, they still have the drawbacks such as short term duration and drainage in water phase. In this report, using a facile electrochemical anodization approach, Cu(OH)2 nanoneedle matrix is built onto Cu substrate. The surface modification with dodecanethiol enables superhydrophobicity wettability. Oil and hydrophobic ZnO nanoparticle obtained by modification with dodecanethiol realize compositing liquid infused surface (CLIS) on Cu surface. For superhydrophobic Cu(OH)2 layer, its corrosion inhibition to Cu is limited. However, when Cu metal is covered with compositing fluid, the corrosion inhibition capability to abiotic and biotic corrosion induced by sulfate reducing bacteria has been remarkably enhanced. After immersion in seawater for 20 days, Z0.01Hz of CLIS Cu is still as high as 1.30 × 109 Ω·cm2, confirming the higher protection efficiency than SHP and LIS coverage. For biotic corrosion inhibition, after soaking for 10 days in sulfate reducing bacteria suspension, Z0.01 Hz of CLIS Cu still remains 1.25 × 105 Ω·cm2, which is much higher than SHP Cu and LIS Cu. Hydrophobic nanoparticles work as the additional absorption matrix to further anchor oil phase, so that drainage will be avoided. The duration of the coating is enhanced. Therefore, CLIS layer has afforded a versatile route to protect Cu from both seawater corrosion and microbiologically induced corrosion.

Corrosion of Cu by a sulfate reducing bacterium in anaerobic vials with different headspace volumes

Microbiologically influenced corrosion (MIC) of copper by Desulfovibrio vulgaris, a sulfate reducing bacterium (SRB), was investigated in anaerobic vials with a fixed broth volume of 40 mL but varied headspace volumes (10 mL, 85 mL 160 mL). It was found that the headspace volume variation had a very large effect on the dissolved [H2S] in the broth and the cell counts of planktonic and sessile cells, as well as Cu corrosion severity. A 16× smaller headspace led to a 1.6-fold increase in the dissolved [H2S], a 13-fold decrease in sessile SRB cell count, a 32-fold decrease in planktonic cell count and a 3.7-fold increase of Cu weight loss. SEM images revealed that different headspace volumes caused different corrosion patterns on the immersed coupons. With a lower headspace volume, pitting corrosion was observed, while with a higher headspace volume, intergranular corrosion was seen. The results confirmed that SRB MIC of Cu belongs to metabolite-MIC (M-MIC) by H2S, unlike SRB MIC of carbon steel that belongs to extracellular electron transfer-MIC (EET-MIC) that is directly correlated with sessile cell counts rather than dissolved [H2S]..

Influence of chloride ion concentration and temperature on the corrosion of Cu–Al composite plates in salt fog

In this work, the effects of temperature and chloride ion concentration were evaluated for the corrosion behavior of Cu–Al composite plates exposed to salt spray. There were three diffusion layers at the interface between Cu and Al, which were Al4Cu9, AlCu and Al2Cu, respectively. Corrosion only appeared on the diffusion layers and the aluminum, amongst which Al2Cu was the most vulnerable to corrosion, AlCu and Al were the second most vulnerable while the corrosion resistance of Al4Cu9 was second to the Cu. When the concentration of NaCl was lower than 3 wt%, the increased concentration had an obvious effect on the mass loss of the corrosion for the Cu–Al composite plates. The kinetic constant of corrosion increased with the increasing NaCl concentration. When the concentration of NaCl increased from 1 wt% to 3 wt%, the kinetic constant of corrosion increased by 31 times. With the concentration of NaCl increasing to 5 wt%, the kinetic constant of corrosion was 4.6 times that of 3 wt% by weight. In addition, the kinetic constant of corrosion was affected by temperature. With an increase of temperature, the kinetic constant of corrosion initially increased, and then decreased. The kinetic constant of corrosion reached its maximum value at 45 °C. Finally, the results of electrochemical testing showed that an increase of the chloride ion concentration (CIC) accelerated the corrosion of Cu–Al composite plates, and the corrosion attack was the worst under 45 °C.

Investigation on friction and wear behaviors of Cu–Zn composition with doped MoS2 powder under electric field

Molybdenum disulfide (MoS2) as a two-dimensional material and solid lubricant shows good friction properties in many applications. The study used the copper (Cu) and zinc (Zn) powder with doped MoS2 powder to prepare the alloy material through the spark plasma sintering (SPS) technology. The coefficient of friction (COF) and wear of alloys with different doped ratios (0 wt%, 3 wt%, 6 wt%, 9 wt%) of MoS2 were studied by using universal mechanical tester (UMT-5), which was based the ball-on-disk method. The results show that the alloy with 3 wt% MoS2 has the lowest COF, about 0.093. The COF of composites containing 9% MoS2 are close to those of un-doped composites, 0.673 and 0.712, respectively. It is mainly owing to excessive corrosion of Cu by MoS2, resulting in increased COF and wear rate. In addition, the effect of the applied electric field on the COF of the alloy was also investigated. It was found that the electric field can increase the COF and the wear rate of the composites. As the voltage increases, oxidation of the Cu was promoted and FeSx was formed to reduce friction and wear. This work provides a new method for manufacturing and studying electrical contact friction materials.

Titanium dioxide-coated copper electrodes for hydrogen production by water splitting

Pt is the most commonly used electrode and catalyst materials for H2 production via water splitting as it provides the highest Gibbs free energy of H2 adsorption (ΔGH) an d overpotential. However, as Pt catalysts are expensive and difficult to mass-produce, several efforts have been made to identify suitable substitutes. Although Cu provides lower ΔGH and overpotential than Pt, it exhibits better catalytic performance than other catalysts and is suitable for H2 production. However, corrosion of Cu may affect its stability of Cu electrode. To overcome this limitation, we have coated a layer of carbon on the copper electrode and then synthesized titanium dioxide-(TiO2-) on the C/Cu electrode for water splitting application. Carbon black (CB) has excellent electrical conductivity and stable resistance for effective working as an electrochemical catalyst, and TiO2 has diverse applications because of its low-cost, non-toxic, and corrosion-resistant characteristics. In this study, TiO2 was synthesized on C/Cu electrodes under UV irradiation for different durations. The optimum irradiation duration was determined to be 15 min via surface and electrochemical analyses. To identify the potential applications of this TiO2–C/Cu electrode, we used artificial wastewater as the electrolyte. The synthesized TiO2–C/Cu electrode exhibited better stability than C/Cu electrode. Further, H2 production with TiO2–C/Cu electrode was higher than that with C/Cu electrode at the same current density. We also investigated the effect of TiO2–C/Cu electrode on decomposition of formaldehyde.

Electrochemical Impedance Studies on the Corrosion of Cu- 35Ni-10Al Alloy in a Molten (0.62Li, 0.38K)2CO3 Environment

Electrochemical Impedance Studies on the Corrosion of Cu- 35Ni-10Al Alloy in a Molten (0.62Li, 0.38K)2CO3 Environment