Density Of Cu Research Articles

Enhanced hydrogen storage via microporous defects and Cu(I) sites in HKUST-1

A series of microporous defective HKUST-1 materials (DMT-HK-nF) are synthesized employing varying amounts (n = 10, 30, and 50 wt%) of 3,5-dinitrobenzoic acid (DNBA) and 1,3,5-benzene tricarboxylic acid as linkers. Subsequently, stepwise washing and solvent exchanges are conducted to enhance the density of Cu(I) sites and increases the surface area. DMT-HK-30F exhibits superior H2 storage capacity (2.55 wt% at 77 K, 100 kPa and 0.93 wt% at 298 K, 7 MPa), approximately 41% and 48% higher compared to pristine HKUST-1 (1.82 wt% at 77 K, 100 kPa, and 0.63 wt% at 298 K, 7 MPa), respectively. This improvement is attributed to an increase in Cu(I) sites and the introduction of linker defects. However, further addition of DNBA decreases the H2 storage capacity due to a reduction in Cu(I) sites and surface area caused by the formation of “missing metal cluster” defects. This study demonstrates that the simultaneous introduction of appropriate defects and high-density Cu(I) sites into the microporous structure is an effective strategy for enhancing the hydrogen storage performance of metal-organic frameworks.

Experimental and Computational Investigation of Salicylhydroxamic Acid as a Corrosion Inhibitor for Copper in Alkaline Solutions

Inhibitors, as indispensable components in chemical mechanical polishing (CMP) slurries, have a significant impact on inhibiting copper (Cu) corrosion and enhancing post-polishing surface quality. However, one of the major challenges in CMP lies in unraveling the microscopic corrosion inhibition mechanism of Cu. This work focuses on investigating the impact of an inhibitor, salicylhydroxamic acid (SHA), on the static etching rate (SER), electrochemical parameters, and surface morphology of Cu. The experimental findings demonstrate that SHA significantly decreases the SER and corrosion current density of Cu, while notably improving the Cu surface quality. The corrosion inhibition mechanisms of SHA on Cu are revealed through adsorption isotherm models, contact angle analysis, electrochemical impedance spectroscopy, and computational chemistry method. The benzene ring, oxime group, and O1 atom of SHA exhibit significant chemical reactivity, facilitating the preferential adsorption of SHA on Cu in a parallel orientation, thereby forming a hydrophobic protective film on the Cu surface. This process hinders the interaction between corrosive solutions and Cu, therefore SHA exhibits excellent corrosion inhibition performance on Cu. These findings hold great importance in gaining a deeper comprehension of the corrosion inhibition process of Cu, and provide guidance for designing more efficient inhibitors.

Building of rich (111) grain boundary in copper for syngas in electrochemical CO2 reduction

Building of grain boundary (GB) in Cu-based catalysts has been demonstrated to be an efficient strategy to control the product selectivity of electrochemical CO2 reduction reaction (eCO2RR). However, the fabrication and modulation of GBs in Cu are still challenging. In this study, a series of bare Cu catalysts with controllable density of Cu(111) GBs were investigated systematically for eCO2RR. These catalysts exhibit superior eCO2RR performance for syngas production with a high FE of ∼80 % and tunable H2/CO ratio of 0.46–2.78. Three-dimensional wormlike Cu with abundant (111) GBs displays a stable H2/CO ratio of ∼0.5 over a wide potential range from −0.9 to −1.2 V (vs. RHE). In situ Raman and ATR-SEIRAS spectroscopy combined with DFT calculations reveal that Cu(111) GBs enhance the adsorption of CO2, lower the energy barriers of CO2 to *COOH and *CO, further highlighting the potential to control syngas production with desirable proportion over Cu-based catalysts.

Tailoring the catalytic microenvironment of CuO with hydrophobic CuSA2 for selective CO2 electroreduction to C2+ products

Advancing the Faraday efficiency (FE) and current density of Cu catalyzed electrochemical CO2 reduction (ECR) reaction to produce C2+ products is important for its practical applications. Constructing a hydrophobic interface to regulate the local reaction environment is an effective method to improve the selectivity of C2+ products, but it is limited by the low reaction current density. In this work, we fabricated a novel hydrophobic and ECR active copper stearate (CuSA2) decorated CuO nanoparticle catalyst (CuO/CuSA2) for ECR reaction toward C2+ products. As a result, the CuO/CuSA2 catalyst achieved an FE of 61.33 % and a partial current density of 429.33 mA cm−2 for C2+ products. The CuSA2 and CuO nanoparticle cooperate very well for the formation of C2+ products. The in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and electrochemical adsorption experiment indicated that the hydrophobic CuSA2 regulated the local ECR reaction environment. The local ∗CO2.- and *CO adsorption were strengthened by hydrophobic CuSA2 modification while the H2O adsorption was inhibited. CuO nanoparticle promotes *CO coupling reaction and enhances C2 intermediates (*OCCOH and *OC2H5) adsorption. Hydrophobic CuSA2 and CuO nanoparticle synergistically promote the generation of C2+ products. This work provides new insights into the design of hydrophobic CO2 reduction electrocatalysts for the preparation of C2+ products.

Enhanced Charge Carrier Dynamics on Sb2 Se3 Photocathodes for Efficient Photoelectrochemical Nitrate Reduction to Ammonia.

Ammonia (NH3 ) is recognized as a transportable carrier for renewable energy fuels. Photoelectrochemical nitrate reduction reaction (PEC NO3 RR) offers a sustainable solution for nitrate-rich wastewater treatment by directly converting solar energy to ammonia. In this study, we demonstrate the highly selective PEC ammonia production from NO3 RR by constructing a CoCu/TiO2 /Sb2 Se3 photocathode. The constructed CoCu/TiO2 /Sb2 Se3 photocathode achieves an ammonia Faraday efficiency (FE) of 88.01 % at -0.2 VRHE and an ammonia yield as high as 15.91 μmol h-1 cm-2 at -0.3 VRHE with an excellent onset potential of 0.43 VRHE . Dynamics experiments and theoretical calculations have demonstrated that the CoCu/TiO2 /Sb2 Se3 photocathode possesses high light absorption capacity, excellent carrier transfer capability, and high charge separation and transfer efficiencies. The photocathode can effectively adsorb the reactant NO3 - and intermediate, and the CoCu co-catalyst increases the maximum Gibbs free energy difference between NO3 RR and HER. Meanwhile, the Co species enhances the spin density of Cu, and increases the density of states near the Fermi level in pdos, which results in a high PEC NO3 RR activity on CoCu/TiO2 /Sb2 Se3 . This work provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate-rich wastewater.

Enhanced Charge Carrier Dynamics on Sb2Se3 Photocathodes for Efficient Photoelectrochemical Nitrate Reduction to Ammonia

AbstractAmmonia (NH3) is recognized as a transportable carrier for renewable energy fuels. Photoelectrochemical nitrate reduction reaction (PEC NO3RR) offers a sustainable solution for nitrate‐rich wastewater treatment by directly converting solar energy to ammonia. In this study, we demonstrate the highly selective PEC ammonia production from NO3RR by constructing a CoCu/TiO2/Sb2Se3 photocathode. The constructed CoCu/TiO2/Sb2Se3 photocathode achieves an ammonia Faraday efficiency (FE) of 88.01 % at −0.2 VRHE and an ammonia yield as high as 15.91 μmol h−1 cm−2 at −0.3 VRHE with an excellent onset potential of 0.43 VRHE. Dynamics experiments and theoretical calculations have demonstrated that the CoCu/TiO2/Sb2Se3 photocathode possesses high light absorption capacity, excellent carrier transfer capability, and high charge separation and transfer efficiencies. The photocathode can effectively adsorb the reactant NO3− and intermediate, and the CoCu co‐catalyst increases the maximum Gibbs free energy difference between NO3RR and HER. Meanwhile, the Co species enhances the spin density of Cu, and increases the density of states near the Fermi level in pdos, which results in a high PEC NO3RR activity on CoCu/TiO2/Sb2Se3. This work provides a new avenue for the feasibility of efficient PEC ammonia synthesis from nitrate‐rich wastewater.

Design and synthesis of magnesium-modified copper oxide nanosheets as efficient electrocatalysts for CO2 reduction.

Electroreduction of carbon dioxide (CO2) to multiple carbon products plays a significant role in carbon neutrality and the production of valuable chemicals. Herein, we developed a magnesium-modified copper oxide nanosheet catalyst (Mg-CuO) using a post-impregnation method. Comprehensive elemental analysis demonstrated the effective incorporation of magnesium into CuO nanosheets, resulting in a noticeable alteration of the electron density of Cu atoms. Consequently, the Mg-CuO nanosheets exhibited an increased efficiency for CO2 electroreduction in comparison with the unmodified CuO nanosheets. The optimized Mg-CuO catalyst exhibited faradaic efficiencies of 46.33% for ethylene production and 62.64% for C2+ production at -1.3 V vs. reversible hydrogen electrode (RHE). DFT proved that the introduction of Mg species could increase the charge density of Cu and decrease the adsorption energy of *CO, which promoted C-C coupling and enhanced the selectivity of C2+ products. This study presents an effective way to adjust the electronic structure of common copper-based electrocatalysts and the corresponding interaction with *CO, resulting in an improved faradaic efficiency of C2+ products.

Boron-modified CuO as catalyst for electroreduction of CO2 towards C2+ products

The development for electroreduction of carbon dioxide (CO2) is crucial for achieving sustainable cycles and carbon neutrality. Electroreduction of CO2 to C2+ products can not only mitigate environmental issues by reducing CO2 but also provide high-value chemicals for modern industry. In this study, we synthesized CuO nanosheets (CuO NS) via simple hydrothermal method and modified its electron structure by in-situ boron (B) doping to produce B-CuO NS catalyst. The XPS spectra revealed the successfully doping of B into CuO NS, which obviously changes the electron density of Cu on the surface of CuO NS. As a result, B-CuO NS displayed a higher performance for electroreduction of CO2 compared with original CuO NS. The optimized B-CuO NS catalyst exhibits a faradaic efficiency of 54.78 % for C2+ production at −1.2 V vs. reversible hydrogen electrode (RHE). Based on the structural characterization and Density Functional Theory (DFT) calculations, the introduction of B increases the charge density of Cu, which could process free electrons to adsorb *CO. Thanks to the easier adsorbing of *CO on B-CuO NS as well as the lower adsorption energy of *CO on Cu, C–C coupling reaction was promoted to produce more C2+ products. This work shows a rational design strategy for developing efficient catalysts for electroreduction of CO2.

Effect of laser energy density on microstructure and properties Cu–Fe–P immiscible alloys fabricated by laser selective melting: heterogeneous and high strength and magnetic

Through the incorporation of phosphorus (P) as a third component, an in-situ formation of a magnetic phase with a nanotwin structure was achieved. The utilization of selective laser melting (SLM) enabled the synthesis of a Cu–Fe–P immiscible alloy that exhibits an integrated structure and function. The microstructure predominantly consists of a magnetic heterogeneous Fe–P-rich phase, comprising a mixture of Fe2P and a small quantity of Fe3P, which is distributed within the ε-Cu Cu-rich matrix in alternating “fiber-layer” and “particle-shape” forms. Additionally, the fibrous Fe2P phase exhibited precipitation of α-Fe, while the Fe–P-rich phase experienced the precipitation of high-density nanotwinned Cu (nt-Cu) particles. The microstructure density and structural characteristics of Cu–Fe–P immiscible alloys were enhanced through the adjustment of laser energy density, leading to improvements in their mechanical and magnetic properties. It was observed that the microstructure density initially increased and then decreased with increasing laser energy density. The highest relative density of the Cu–Fe–P immiscible alloy microstructure (98%) was achieved at a laser energy density of 53 J/mm3. Furthermore, the influence of laser energy density on the mechanical and soft magnetic properties of Cu–Fe–P immiscible alloys was examined. The findings indicate that the mechanical and soft magnetic properties of these alloys are affected by the laser energy density. The findings indicate that the compact Cu–Fe–P immiscible alloys exhibit favorable compression mechanical properties and soft magnetic properties. Specifically, the ultimate compressive stress can reach 890.5 ± 20 MPa, while the failure strain can reach 20.5 ± 2%. Additionally, the coercivity is observed to be as low as 20.0 Oe, the magnetic saturation strength as high as 93.5 emu/g, and the residual magnetization at 1.1 emu/g.

Spectroscopic and electrochemical investigation of ternary Cu (II) complex interaction with calf thymus DNA

Aiming to design unique metallic drugs with significant therapeutic activity, in this work, mixed ligand Cu (II) complex involving 2,2′‐bipyridine and phenylalanine [Cu (bpy) (phenala.)Cl].2H2O has been fabricated and characterized using IR spectroscopy. The interaction of Cu (II) complex with CT‐DNA molecules was examined through UV–vis absorption titration plots, thermal denaturation experiments, viscosity measurements, and electrochemical studies. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry measurements have been exploited to elucidate their binding style. The negative potential shift in ΔE and E1/2 values as well as the increased current density of Cu (II)/Cu(I) redox couple suggested the promoted rate of electron transfer process in presence of CT‐DNA molecules in the examined solution. Some kinetic parameters were also estimated such as the diffusion coefficient, the exchange current density, and Tafel slope values. Based on the results of these binding experiments, a groove and/or electrostatic interaction mode was expected. The antimicrobial activity of the studied Cu (II) complex was screened against a series of bacteria and fungi. An outstanding performance was shown when treating different Gram‐positive and Gram‐negative bacteria types. Moreover, an enhanced cytotoxicity behavior toward some human tumor cell lines, including MCF7, HEPG2, and HFB4, was detected with respective IC50 values of 43.02, 51.21, and >200 μM when incubated with Cu (II) complex for 72 h. These results suggest the application of [Cu (bpy) (phenala.)Cl].2H2O complex as a chemotherapeutic agent with a promising output in the drug discovery field.

Electronic behavior of Ag-doped YBa2Cu3O7-δ using Hubbard-U correction method

The ability to accurately describe the electronic properties in the highly correlated materials YBa2-xAgxCu3O7-δ was queried. Previous calculations revealed that the electronic bandgap was estimated much lower than the established experimental value when standard density functional theory, DFT was used in the computation of pure YBa2Cu3O7-δ. The electronic properties of Ag-doped at Ba-site samples such as the bandgap, total and partial density of states, electron density, and Mulliken population, were computationally calculated using DFT with the Hubbard-U correction method, DFT+U and compared to the pure samples. The calculation was conducted using CASTEP code in Material Studio software applying both LDA and range of GGA exchange-correlation functionals. 2 × 2 × 1 supercell symmetry was applied to enlarge the single cell crystal structure to able the dopant concentration, x = 0.250 at the Ba-site. The calculated bandgap of pure YBa2Cu3O7-δ (Eg = 3.67 eV) shows 8.25% difference to the referred theoretical value using the GGA-PBE+U functional. Upon Ag-dopant, the bandgap was calculated to be Eg = 3.85 eV. The energy of the Ba 6p orbital on the valence band has shifted from − 10.49 eV to − 10.67 eV, away from the Fermi energy level, and the density of state has increased significantly by + 57.52%. The Ag dopant enhanced the electron density of Cu and O atoms along the CuO chain and CuO2 plane. The study enables the prediction of impurity dopant concentration prior to experimental work, hence promoting green research.

Magneto‐structural correlations of oximato‐bridged dinuclear copper(II) complex: A theoretical perspective

AbstractThe theoretical understanding of the magneto‐structural correlations of an oximato‐bridged dinuclear copper(II) complex can help develop new applied molecular magnets. This study evaluated the magnetic coupling constant of a [Cu2(hfac)2(ppko)2] complex using the density functional theory combined with the broken symmetry approach (DFT‐BS). The magnetic structure correlation between the magnetic coupling constant (Jcalc) of the complex and the structural parameters, NOCu bond angle (α), ONCu bond angle (β), NO bond length (RN‐O), and Cu•••Cu distance (R0), was evaluated. The data showed that Jcalc initially decreased and then increased as bond angles α and β increased. These relationships were expressed by unary quadratic functions. However, Jcalc varied linearly with the bond length, RN‐O, and spacing, R0. Moreover, in the ground state, the magnetic coupling constant increased with a decrease in the spin density of Cu(1), but gradually decreased as the spin density of Cu(2) increased. An increase of parameters α, β, RN‐O, and R0, resulted in a gradual increase in the distance between Cu(II) ions, and the square of the overlap integral between the non‐orthogonal magnetic orbitals of Cu(II) ions to gradually decay. Finally, the contribution of the antiferromagnetic part decreased as the magnetic coupling constant gradually increased.

Regulating the charge density of Cu(I) single sites enriched on the surface of N3c Vacancies-engineered g-C3N4 for efficient Fenton-like reactions

The construction of highly accessible copper active sites with enhanced charge density is essential for the performance of Cu-based Fenton catalysts. Herein, we report the preparation of a catalyst comprising Cu(I) atoms anchored on the surface of N3c vacancies-engineered g-C3N4 (Cu/Nv-CN) and its enhanced Fenton-like performance. The surface-enrichment of single Cu(I) atoms maximizes the exposure of active sites and reduces the mass transfer limitation for short-lived hydroxyl radicals. The N3c vacancies, meanwhile, facilitate electron donation from N2c to Cu sites, greatly increasing the number of single Cu(I) sites. These two strategies synergistically enhance the hydroxyl radical production rate in the Fenton-like process and endow Cu/Nv-CN with not only excellent performance in degrading various contaminants (such as phenolic compounds, endocrine disruptors, antibiotics, and dyes), both in purified and real water samples matrixes, but also superior bactericidal properties for Escherichia coli. Compared to bulk Cu-doped g-C3N4 without N3c vacancies (CO-Cu/CN), Cu/Nv-CN shows a more than 14-fold increase in phenol degradation and an enhancement of approximately 4 log10 CFU/mL in bacterial inactivation. Our strategy of increasing the number of Cu(I) single atoms through surface enrichment and enhanced electron donation opens up a new route for the design of efficient Fenton-like catalysts for environmental remediation.

Structural characteristics of metal (Ni, Cu) doped cobalt phosphide catalysts and mechanism of catalytic hydrogen evolution of NH3BH3

AbstractIn this paper, using density functional theory (DFT) methods, we meticulously investigated the structural properties of cobalt phosphide (CoP) and its Cu‐ and Ni‐doped counterpart. Then, on the surfaces of three catalysts, the hydrogen evolution reaction mechanism of ammonia borane (NH3BH3) was examined in turn, and four possible hydrogen evolution reaction paths of NH3BH3 on the catalyst surface were reviewed. The optimal reaction channel for each catalyst was found by comparing the activation energies of the control steps for several reaction paths, and activation energies of the optimal reaction for CoP, Cu, and Ni‐doped CoP were 31.4, 30.4, and 30.8 kcal/mol, respectively. Cu‐ and Ni‐ doped were beneficial to improve the hydrogen evolution reaction activity of NH3BH3. At the same time, the band structures and density of states of the stable catalysts were calculated. The results showed that near the fermi level, the electron cloud density of Cu and Ni‐doped CoP catalysts increased. The energy gap values of the three catalysts are 43.8, 41.0, and 41.7 kcal/mol, respectively, and the energy gap values of Cu and Ni doped CoP catalysts decrease. The energy gap values of the three catalysts are inversely proportional to their catalytic activities. We believe that these two factors together contribute to the increased catalytic activity of the doped CoP. Our results revealed the correlation between the physical properties of CoP and its metal‐doped catalysts and their catalytic activity.

Defect-State Transition Associated Hole Dynamics in Cuprous Iodide Nanosheets

The cuprous iodide of zinc-blende structure (γ-CuI) is a p-type semiconductor with a wide band gap of 3.1 eV. It is considered promising as the third generation of semiconductors, in applications of hole transport layer and transparent electrode due to the high hole density and carrier mobility, but its carrier transport characteristics have not yet been understood in detail. We synthesized γ-CuI nanosheets with large sizes and measured the carrier dynamics by femtosecond transient absorption (TA) spectroscopy. We observed signals of defect trapping photogenerated carriers during band-edge transitions, as well the weak band filling and photoinduced absorption directly associated with defect states. The species and lifetimes of defect assisted transition are identified and quantified based on TA measurements with various excitation fluences, and the changes of spectra and kinetics of defect band filling are correlated to the trend of density of Cu and I vacancies in samples with different thicknesses, based on the observations on a single nanosheet. We extract a diffusion coefficient of ∼71 cm2 s–1 and derive a diffusion length longer than the sample thickness, which possibly makes a remarkable contribution to the generation of a photocurrent. Our findings are expected to offer help for harnessing the defects in γ-CuI and improving its performances in optoelectronic applications.

Facile flame catalytic growing carbon coating on Cu panel with surface protection performance comparable to that of graphene film via CVD

Uniform amorphous carbon films were deposited on polycrystalline copper substrate within a few minutes by a facile flame coating method. The effects of the flame coating process on the grain structure, corrosion resistance and mechanical properties of the metal substrate were investigated and compared with those of graphene counterpart via chemical vapor deposition (CVD). Due to the different heating temperature required for carbon deposition, it was found that the crystalline and grain structure of the Cu substrate varied with the deposition method, as well as their mechanical properties. Results indicated that the higher temperature, the larger metal grains formed and the lower hardness accordingly. Thanks to the lower temperature required for the flame coating approach, the hardness of the carbon coated Cu samples was much larger than that of graphene coated ones. Moreover, the corrosion current density of Cu with flame coating for 15 min declined sharply to be one thirtieth of that of bare Cu in 3.5 wt% NaCl solution, which was comparable to that of graphene coated sample. Furthermore, the oxidation resistance performance of both carbon and graphene coating as protective layer for Cu in hot air was also studied. Results indicated that the amorphous carbon had comparable protective performance with that of graphene layer and both of them slowed down the oxidation of Cu at elevated temperature. The corresponding corrosion mechanism was also proposed.

Evolution of texture distribution in thickness direction of aluminum sheet in metal spinning

We evaluated the texture distribution in the thickness direction of the spun workpieces and clarified the mechanism of the change in the crystal orientation of the texture during metal spinning. Blank aluminum disks with a thickness of 1.44 mm were deformed into circular truncated cone cups by under-, true shear, and over-spinning and into cylindrical cups by 13 passes of conventional spinning. Crystal orientation analysis using electron backscatter diffraction revealed that the calculations of the orientation densities for small Miller indices could lead to a systematic evaluation of high intensity texture. The orientation density of Cu {121}<11¯1> decreased or that of B {110}<11¯2> increased on the roller side of the shear-spun part, of the workpieces formed by shear spinning, and on the roller side of the wall part and on the mandrel side of the open-edge part, of the workpieces formed by conventional spinning. The cosine similarity and Euclidean distance showed that the texture distributions obtained by shear spinning and that of the wall part obtained by conventional spinning were similar. Based on the stress state and preferred crystal orientation in deep drawing, the mechanism of the change in crystal orientation during spinning were described. The density of the texture with {110} (corresponding to B in this study) parallel to a disk plane increased when tensile stress was applied in the circumferential direction, contrarily, when compressive stress was applied in a similar fashion the density of the texture with {112} (corresponding to Cu) parallel to the disk plane increased.

Selective CO-to-acetate electroreduction via intermediate adsorption tuning on ordered Cu–Pd sites

Electrochemical reduction of carbon monoxide (CO) has recently emerged as a potential approach for obtaining high-value, multicarbon products such as acetate, while the activity and selectivity for prodution of acetate have remained low. Herein, we develop an atomically ordered copper–palladium intermetallic compound (CuPd) composed of a high density of Cu–Pd pairs that feature as catalytic sites to enrich surface *CO coverage, stabilize ethenone as a key acetate path intermediate and inhibit the hydrogen evolution reaction, thus substantially promoting acetate formation. The CuPd electrocatalyst enables a high Faradaic efficiency of 70 ± 5% for CO-to-acetate electroreduction and a high acetate partial current density of 425 mA cm−2. Under membrane electrode assembly conditions, the CuPd electrocatalyst demonstrated a 500 h CO-to-acetate conversion at 500 mA cm−2 with a stable acetate Faradaic efficiency of ~50%. Electrocatalytic CO reduction presents a route to low-temperature acetate production, but activity and efficiency remain below practical levels. Here, the authors present an intermetallic compound with stable, atomically ordered Cu–Pd pairs that facilitates an acetate pathway and delivers 70% Faradaic efficiency at 425 mA cm−2.

Corrosion behavior of tin‐phosphor bronze strips in environments containing Cl− and HCO3−

AbstractThe corrosion behaviors of Cu–7.42Sn–0.156P and Cu–5.78Sn–0.162P alloys in different solutions were investigated. The results show that the Cu–Sn–P alloy with higher Sn content exhibits better corrosion resistance. In the NaCl, NaHCO3, and NaCl+NaHCO3 solutions, compared with Cu–5.78Sn–0.162P alloy, the corrosion current densities of Cu–7.42Sn–0.156P alloy are reduced by 25.2%, 36.9%, and 34.5%, and the polarization resistances are increased by 32.0%, 25.4%, and 29.9%. The Cu–Sn–P alloys have the best corrosion resistance in the NaHCO3 solution, followed by the NaCl solution and the worst in the NaCl + NaHCO3 solution. The increase of Sn is helpful to improve the density and spalling resistance of the corrosion film. There is a double‐layer structure for the corrosion film of Cu–Sn–P alloy. For the alloys immersed in the NaCl solution and the NaCl+NaHCO3 solutions, the corrosion films consisted of Cu2O, CuO, and SnO2. For the alloys immersed in the NaHCO3 solution, the corrosion films are composed of Cu2O, CuO, SnO, and SnO2. The increase of Sn content in the alloy can increase the contents of Cu2O and SnO in the corrosion films.

Copper reinforced SiAlON matrix composites produced by spark plasma sintering

Cu particles (vol%. 0, 10, 20, 30) were incorporated into the αı:βı-SiAlON matrix to investigate its effect on fracture toughness, Vickers hardness, density, friction, and wear. The composite powders were prepared by planetary milling and sintering was carried out by spark plasma sintering at a temperature of 1600 °C for 10 min. The bulk density of Cu- αı:βı-SiAlON hybrid composites varied between 3,2501 and 2,9547 g/cm3, % open porosity values of composites increased with the addition of Cu. The fracture toughness showed improvement when the content of copper is 30 vol% (8,76 MPam1/2). On the other hand, hardness decreased from 17.6 GPa to 12.25 GPa, as expected, related to copper's low hardness value compared to the SiAlON matrix. Although the copper phase remained stable after sintering, it was determined that some of it formed copper silicide phase. In terms of wear, the use of metallic second phase as copper seems to enormous addition for SiAlONs in order to develop wear properties depending on the provided physico-mechanical properties such as high fracture toughness, self-lubrication etc., which discussed in this study. The wear rates were decimated in SiAlON matrix with the 30 wt% the optimal amount of copper.