Copper Substitution Research Articles

Heavy metals: toxicity and human health effects.

Heavy metals are naturally occurring components of the Earth's crust and persistent environmental pollutants. Human exposure to heavy metals occurs via various pathways, including inhalation of air/dust particles, ingesting contaminated water or soil, or through the food chain. Their bioaccumulation may lead to diverse toxic effects affecting different body tissues and organ systems. The toxicity of heavy metals depends on the properties of the given metal, dose, route, duration of exposure (acute or chronic), and extent ofbioaccumulation. The detrimental impacts of heavy metals on human health are largely linked to their capacity to interfere with antioxidant defense mechanisms, primarily through their interaction with intracellular glutathione (GSH) or sulfhydryl groups (R-SH) of antioxidant enzymes such as superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR), and other enzyme systems. Although arsenic (As) is believed to bind directly to critical thiols, alternative hydrogen peroxide production processes have also been postulated. Heavy metals are known to interfere with signaling pathways and affect a variety of cellular processes, including cell growth, proliferation, survival, metabolism, and apoptosis. For example, cadmium can affect the BLC-2 family of proteins involved in mitochondrial death via the overexpression of antiapoptotic Bcl-2 and the suppression of proapoptotic (BAX, BAK) mechanisms, thus increasing the resistance of various cells to undergo malignant transformation. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important regulator of antioxidant enzymes, the level of oxidative stress, and cellular resistance to oxidants and has been shown to act as a double-edged sword in response to arsenic-induced oxidative stress. Another mechanism of significant health threats and heavy metal (e.g., Pb) toxicity involves the substitution of essential metals (e.g., calcium (Ca), copper (Cu), and iron (Fe)) with structurally similar heavy metals (e.g., cadmium (Cd) and lead (Pb)) in the metal-binding sites of proteins. Displaced essential redox metals (copper, iron, manganese) from their natural metal-binding sites can catalyze the decomposition of hydrogen peroxide via the Fenton reaction and generate damaging ROS such as hydroxyl radicals, causing damage to lipids, proteins, and DNA. Conversely, some heavy metals, such as cadmium, can suppress the synthesis of nitric oxide radical (NO·), manifested by altered vasorelaxation and, consequently, blood pressure regulation. Pb-induced oxidative stress has been shown to be indirectly responsible for the depletion of nitric oxide due to its interaction with superoxide radical (O2·-), resulting in the formation of a potent biological oxidant, peroxynitrite (ONOO-). This review comprehensively discusses the mechanisms of heavy metal toxicity and their health effects. Aluminum (Al), cadmium (Cd), arsenic (As), mercury (Hg), lead (Pb), and chromium (Cr) and their roles in the development of gastrointestinal, pulmonary, kidney, reproductive, neurodegenerative (Alzheimer's and Parkinson's diseases), cardiovascular, and cancer (e.g. renal, lung, skin, stomach) diseases are discussed. A short account is devoted to the detoxification of heavy metals by chelation via the use of ethylenediaminetetraacetic acid (EDTA), dimercaprol (BAL), 2,3-dimercaptosuccinic acid (DMSA), 2,3-dimercapto-1-propane sulfonic acid (DMPS), and penicillamine chelators.

Optimizing ZnFe2O4 with copper substitution for improved lithium storage performance

Optimizing ZnFe2O4 with copper substitution for improved lithium storage performance

Copper-catalyzed yne-allylic substitutions: concept and recent developments.

The catalytic (asymmetric) allylation and propargylation have been established as powerful strategies allowing access to enantioenriched α-chiral alkenes and alkynes. In this context, combining allylic and propargylic substitutions offers new opportunities to expand the scope of transition metal-catalyzed substitution reactions. Since its discovery in 2022, copper-catalyzed yne-allylic substitution has undergone rapid development and significant progress has been made using the key copper vinyl allenylidene intermediates. This review summarizes the developments and illustrates the influences of copper salt, ligand, and substitution pattern of the substrate on the regioselectivity and stereoselectivity.

Evaluating Sulfur as a P‐Type Dopant in Cu3N Using Ab Initio Methods

Copper nitride (Cu3N) is an environmentally friendly semiconducting material with bipolar doping capability and is of interest to various applications. As deposited Cu3N films have inherent n‐type conductivity, further controllable n‐type doping is possible by introducing metal impurities. First‐principles methods based on density functional theory and beyond have been employed to study the p‐type doping behavior of sulfur atoms in Cu3N. The structural, electronic, optical, and thermal properties of pure Cu3N and sulfur‐doped Cu3N are computed for single and 3 × 3 × 3 supercells. Sulfur doping causes a shift from intrinsic n‐type to p‐type behavior. This study confirms that sulfur atoms in sulfur‐doped copper nitride preferentially occupy interstitial positions over nitrogen substitution, face‐centered, or copper substitution sites. Due to this change and an increased lattice constant, Cu3N becomes a softer material with a larger bandgap in the single‐cell alloy. Doped Cu3N supercell results show significant changes in optical properties appropriate for solar and other photoelectric applications. Cu3N:S exhibits remarkable enhancements in power factor and thermal and electrical conductivity, indicating potentially better performance in thermoelectric applications. The dielectric constant and absorption coefficient also significantly change with the incorporation of sulfur into Cu3N.

Discovery and Underground Mining of Large Deposits: Essential Training to Ensure Copper Supply

Editor’s note: The aim of the Geology and Mining series is to introduce early career professionals and students to various aspects of mineral exploration, development, and mining in order to share the experiences and insight of each author on the myriad of topics involved with the mineral industry and the ways in which geoscientists contribute to each. Abstract A supply shortfall of at least 6 million tonnes (Mt) Cu is expected by 2031—with total demand now forecast to increase from 25 Mt in 2023 to >36 Mt, and possibly to a suggested 50 Mt by 2050—given the present trend in demand. The deficit can be partially filled by increased mine production, expanding currently installed mine production capacity, and increasing Cu recycling. However, satisfying demand in 2050 as the demand-to-mining supply gap increases will require the accelerated discovery of at least five large Cu deposits—individually producing >0.5 to >1.0 Mt/yr Cu—and their related mine development, by 2030. These five deposit discoveries are required to replace mines scheduled to close in the 2050s, given the >20 years needed to take a deposit from discovery to mine production. The two largest sources of Cu supply, porphyry and sediment-hosted Cu deposits, can potentially fill the gap if enough discoveries are made; however, there is no evidence that this is about to occur. Future porphyry Cu discoveries are expected to be mined underground, mostly by a caving method. The demand increase is occurring at a time when the capital intensity of porphyry Cu mine development has almost doubled since 2006. We predict that the only solution to the future Cu demand-supply challenge for society and the mining industry in the short to medium term rests with simple demand-supply economics and a substantially increased Cu price. Copper substitution by other materials and recycling could potentially benefit from a significantly increased price; however, the major advantage will be conferred on deposits amenable to open-pit mining that are undeveloped because of price-dependent, failed feasibility studies. The challenge of possibly doubling Cu supply by ca. 2050 through developing mines on large Cu deposits—both discovered and undiscovered, in an unprecedented number and in a shorter period—will require a major increase in the number of competent mining industry personnel. This comes at a time when the industry faces an aging workforce, leading to a critical skills gap compounded by a chronic shortage of students graduating in the sciences and engineering with mining-related university degrees. There is an acute shortage of experienced professionals in cave mining, and the substantial number of open-pit mining professionals who are predicted to retire by 2030 will need to be replaced. On-the-job training of geoscientists and engineers after graduation, delivered by experienced practitioners through university-accredited professional development programs, is suggested as the solution.

Study of the magnetic and structural properties of BaFe12 – xCuxO19 ferrites obtained by hydrothermal synthesis

Hexagonal ferrites of M-type (in particular, BaFe12O19) are magnetic materials with functional characteristics affected both by chemical composition and technology of their synthesis. We present the results of studying the magnetic and structural properties of BaFe12 – xCuxO19 hexaferrites (x = 0, 0.1, 0.2, 0.3, 0.4) obtained by hydrothermal synthesis with partial substitution of copper for iron. The composition of the synthesized samples was analyzed using X-ray diffraction, and the magnetic characteristics were measured using a vibration magnetometer. It has been revealed that the coercivity of the ferrite powders depends non-monotonically on the copper concentration and reaches the maximum (5629 Oe) and minimum (4698 Oe) values at x = 0 and x = 0.2. The presence of copper reduces the coercive force, but at the same time the values remain rather high compared to the results of similar studies. The saturation magnetization of the obtained ferrites gradually decreases (from 65.88 to 60.75 A · m2/kg at x = 0 and x = 0.4, respectively) with increasing. The distribution of Cu over ferrite sublattices was studied using Mössbauer spectroscopy. It is shown that in the hexaferrite structure, copper ions preferentially occupy 12k and 4f1 sites. Hence, a decrease in the saturation magnetization with increasing x is most likely attributed to the presence of side non-magnetic phases observed on X-ray diffraction patterns. It is also revealed that during synthesis, copper participates in the formation of low-melting phases on the surface of hexaferrite grains which promotes agglomeration of the particles. Thus, the resulting powders can potentially be sintered at lower temperatures and, therefore, without a significant increase in the size of crystallites. Herewith, the coercivity retains its original high values. The results obtained can be used in developing ferrite permanent magnets with improved characteristics.

Improving the optical properties of magnesium spinel chromites through Ni and Cu substitutions for optoelectronic applications.

In this study, we investigated the optoelectronic performance of magnesium spinel chromites with nickel (Ni) and copper (Cu) substitutions. Using the sol-gel method, we synthesized two spinel chromites: Mg0.6Ni0.4Cr2O4 (MNCO) and Mg0.6Cu0.4Cr2O4 (MCCO). We extensively characterized these samples to analyze their thermal, structural, elastic, and optical properties. Structural analysis reveals good agreement between the calculated and refined structural parameters, which supports the proposed cation distributions for the samples. By calculating stiffness constants from force constants, we derived elastic moduli such as bulk modulus, longitudinal modulus, and rigidity modulus. MCCO exhibited lower values for these moduli, as well as the Debye temperature, compared to MNCO. Both samples displayed a brittle mechanical nature according to the Pugh ratio, while the Poisson ratio remained constant at 0.25, indicating isotropic elasticity. UV-vis-NIR spectroscopy revealed that MNCO has higher band-gap (E g) and Urbach (E u) energies than MCCO. Further analysis of refractive index, penetration depth, extinction coefficients, nonlinear optical parameters, optical conductivity, and optical dielectric constants highlighted the promising optoelectronic applications of the synthesized materials. Our study found that the band-gap energy values of the as-synthesized samples were smaller than reported values for MgCr2O4 spinel chromites, indicating that Ni and Cu substitutions offer an opportunity to extend the sunlight absorption range of magnesium chromites.

Enhanced dielectric properties of copper substituted nickel ferrite nanoparticles for energy storage applications

In this study, it was aimed to obtain copper-substituted nickel ferrite nanoparticles, which are advantageous for use in energy storage devices such as batteries and supercapacitors that provide high energy storage capability with their high dielectric behavior, by co-precipitation method. Nickel ferrite nanoparticles in the form of CuxNi1-xFe2O4 containing copper substitution at ratios for x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were synthesized. X-ray diffraction Method (XRD) was used to analyze the spinel structure, the purity phase, and the crystalline size of the nanoparticles. Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier Transform Infrared (FTIR) Spectroscopy were also performed to investigate the particle size, morphological distribution, and the functional groups of the samples. The structural analyses confirmed the successfully produced single-phase pure cubic spinel nickel ferrite and copper-substituted nickel ferrites with nanometer-scale particle distribution. The Impedance Spectroscopy technique was used for the characterization of the dielectric properties of the samples. Frequency-dependent complex dielectric, impedance, modulus, and alternating current (AC) conductivity mechanisms of the copper-doped nickel ferrite nanoparticles (CuxNi1-xFe2O4) were determined. The results showed that copper-induced nickel ferrite nanoparticles display a promising dielectric material consisting of grains and grain boundaries which are confirmed by Maxwell-Wagner interface-type polarization, which is in agreement with Koop's theory. Furthermore, a remarkable enhancement is obtained on the dielectric parameters of copper-induced nickel ferrites for x = 0.2, and it is seen that this is a critical value on the doping ratio. In addition, the dielectric parameters decreased between x = 0.2–0.8 ratios but still showed higher values than pure nickel ferrites, confirming that nickel ferrites have a tunable dielectric behavior depending on the stoichiometric copper doping ratios. Therefore, this may make them a promising dielectric medium for further studies in various electronic device applications.

Copper doping effects on the superconducting properties of Sm‐based oxypnictides

AbstractA systematic investigation has been performed by synthesis and comprehensive characterization of a series of SmFe1−xCuxAsO0.8F0.2 bulks (x = 0–0.2). These samples are well characterized by structural, Raman spectroscopy, microstructural, transport, magnetic measurements, and supplementary calculations within density functional theory (DFT). The parent compound, SmFeAsO0.8F0.2 (Sm1111), exhibits a superconducting transition temperature (Tc) of approximately 54 K. The lattice volume (V) is increased with Cu substitution (x) without observing any impurity phase related to copper, which confirms the successful incorporation of Cu at Fe sites in the superconducting FeAs layers. These analyses are also well in agreement with Raman spectroscopy measurements and relevant DFT results. The superconducting transition is decreased systematically with copper doping and completely suppressed for 7% Cu‐doped Sm1111 (x = 0.07). A large amount of Cu substitution (x ≥ 0.07) has demonstrated the metal to insulate transition in the low‐temperature range, and no impurity phase was observed even at high Cu doping levels (x = 0.2). The calculated critical current density of the parent sample is suppressed with copper substitution, suggesting the reduced pinning centers, sample density, and grain connections, as confirmed by the microstructural analysis. Our studies suggest that the substitution of Cu in the superconducting FeAs layer, resulting the enlargement of the lattice volume, is a source of strong disorder scattering, leading to the suppression of Tc and the emergence of metal‐to‐insulator, unlike the more successful carrier doping by nickel (Ni) or cobalt (Co), as previously reported.

Exploring the physicomechanical properties and biocompatibility traits of CuO Substituted 45S5 bioactive glass through in-vitro analysis

While clinically approved, 45S5 bioactive glass possesses limitations in terms of mechanical and biological properties for broader biomedical applications. To address this, we have synthesized 45S5 bioactive glass with partial substitution of CuO for CaO using the melt-quench technique. We conducted extensive characterization using XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscopy), and UTM (Universal Testing Machine), in-vitro simulated body fluid (SBF) studies, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), antibacterial and hemolysis assays. Our results demonstrate that CuO-substituted glasses exhibit enhanced bioactivity, as evidenced by the formation of a hydroxyapatite layer on their surface after immersion in SBF, confirmed from XRD, FTIR and SEM. Additionally, MTT assay with MG-63 cells reveals improved cell proliferation, particularly with 1.5 mol% of CuO addition. Furthermore, Cu_2 to Cu_4 compositions demonstrate effective inhibition of E. coli (Escherichia coli) colonization. The substitution of CuO also leads to significant improvements in the mechanical properties of these bioactive glasses. The density of 45S5 glass increases from 2.72 to 2.86 g/cc, compressive strength from 53 to 64 MPa and young's modulus from 76.74 to 82.21 GPa after the substitution of copper from 0.0 to 2.5 mol%, respectively. Partial substitution of CuO for CaO in 45S5 bioactive glass significantly enhances its physicomechanical properties and biocompatibility compared to the original 45S5 bioactive glass that can be used as implant materials for various biomedical applications.

A comparative in vitro and in vivo analysis of the impact of copper substitution on the cytocompatibility, osteogenic, and angiogenic properties of a borosilicate bioactive glass.

The 0106-B1-bioactive glass (BG) composition (in wt %: 37.5 SiO2, 22.6 CaO, 5.9 Na2O, 4.0 P2O5, 12.0 K2O, 5.5 MgO, and 12.5 B2O3) has demonstrated favorable processing properties and promising bone regeneration potential. The present study aimed to evaluate the biological effects of the incorporation of highly pro-angiogenic copper (Cu) in 0106-B1-BG in vitro using human bone marrow-derived mesenchymal stromal cells (BMSCs) as well as its in vivo potential for bone regeneration. CuO was added to 0106-B1-BG in exchange for CaO, resulting in Cu-doped BG compositions containing 1.0, 2.5 and 5.0 wt % CuO (composition in wt %: 37.5 SiO2, 21.6/ 20.1/17.6 CaO, 5.9 Na2O, 4.0 P2O5, 12.0 K2O, 5.5 MgO, 12.5 B2O3, and 1.0/ 2.5/ 5.0 CuO). In vitro, the BGs' impact on the viability, proliferation, and growth patterns of BMSCs was evaluated. Analyses of protein secretion, matrix formation, and gene expression were used for the assessment of the BGs' influence on BMSCs regarding osteogenic differentiation and angiogenic stimulation. The presence of Cu improved cytocompatibility, osteogenic differentiation, and angiogenic response when compared with unmodified 0106-B1-BG in vitro. In vivo, a critical-size femoral defect in rats was filled with scaffolds made from BGs. Bone regeneration was evaluated by micro-computed tomography. Histological analysis was performed to assess bone maturation and angiogenesis. In vivo effects regarding defect closure, presence of osteoclastic cells or vascular structures in the defect were not significantly changed by the addition of Cu compared with undoped 0106-B1-BG scaffolds. Hence, while the in vitro properties of the 0106-B1-BG were significantly improved by the incorporation of Cu, further evaluation of the BG composition is necessary to transfer these effects to an in vivo setting.

Increasing thermodynamic stability and electrochemical performance of IT-SOFC cathodes based on Ln2MO4 (Ln = La, Pr; M = Ni, Cu)

La2-xPrxNi1-yCuyO4+δ (x = 0.5, 1, 1.5, y = 0.4, 0.6, 0.8) were synthesized by a citrate-nitrate method and studied as cathode materials for IT-SOFCs by Electrochemical Impedance Spectroscopy (EIS) in symmetrical cells based on the Ce0.8Sm0.2O2-δ (SDC) and La28-zW4+zO54+1.5z (z = 0.85, LWO) electrolytes. Phase identification and crystal structure analysis by means of X-ray powder diffraction (XRPD) shows that solubility of copper y decreases with the increase in praseodymium content x due to increasing structural distortions. Thermodynamic stability of La2-xPrxNi1-yCuyO4+δ at intermediate temperatures in air tends to decrease with praseodymium doping level x and increases with copper substitution for nickel y. Oxides with x = 0.5 and 0.6≤y ≤ 0.8 are shown to be thermodynamically stable at 700 °C in air. Electrochemical performance of the La2-xPrxNi1-yCuyO4+δ electrodes improves with praseodymium and copper doping. The results of EIS measurements at different temperatures and oxygen partial pressures (P(O2)) reveal that the rate-determining step of the overall electrochemical process is charge transfer, which can be a combination of surface diffusion and bulk diffusion. EIS studies in dry and wet air indicate the presence of proton conduction in the studied electrodes. The area-specific resistances (ASRs) for La2-xPrxNi1-yCuyO4+δ with x = 0.5, y = 0.6 and y = 0.8 in contact with SDC are comparable with those reported for Pr2NiO4+δ and equal to 0.07 and 0.065 Ω cm2 at 800 °C.

Yolk-Shell Construction of Na3V2(PO4)2F3 with Copper Substitution Microsphere as High-Rate and Long-Cycling Cathode Materials for Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) is emerging as a promising cathode material for high-voltage sodium-ion batteries. Whereas, the inferior intrinsic electrical conductivity leading to poor rate performance and cycling stability. To address this issue, a strategy of synthesizing unique yolk-shell structured NVPF with copper substitution via spray drying method is proposed. Besides, the synergistic modulation of both crystalline structure and interfacial properties results in significantly enhanced intrinsic and interfacial conductivity of NVPF. The optimized yolk-shell structured cathode materials can possess a high capacity of 117.4 mAh g-1 at 0.1 C, and remains a high-capacity retention of 91.3% after 5000 cycles. A detailed investigation of kinetic properties combined with in situ XRD technology and DFT calculations, has been implemented, particularly with regard toelectron conduction and sodium ion diffusion. Consequently, the yolk-shell structured composition of Na3V1.94Cu0.06(PO4)2F3 with nitrogen-modified carbon coating layer shows the lowest polarization potential because of the effectively enhanced electronic conductivity and Na+ diffusion process in the bulk phase. The robust electrochemical performance suggests that developing the unique yolk-shell structure with the collaboration of interface and bulk crystal properties is a favorable strategy to design cathode material with a high performance for sodium-ion batteries.

Band gap engineering and photocatalytic degradation of lead-free halide chalcogenide Cs(Ag1-xCux)2I3

Lead halide chalcogenides are becoming more and more widely used in photocatalysis, but the toxicity of elemental lead has forced the study of environmentally friendly lead-free halide chalcogenides. In this paper, the band gap modulation of Cs(Ag1-xCux)2I3 and its application in photocatalytic degradation were investigated. Cs(Ag1-xCux)2I3 single crystals were prepared by an anti-solvent method. Experimental analyses showed that copper substitution could modulate the band gap size and improve the photocatalytic performance, in which Cs(Ag0.8Cu0.2)2I3 degraded 99.0 % of methylene blue pollutants in 4 h with good reusability. This study demonstrated that Cs(Ag1-xCux)2I3 has good application prospects in photocatalytic degradation.

Influence of Strain Rate on Metallurgical and Mechanical Properties of Friction Stir Spot Welded Aluminium Joints

Nowadays, the substitution of copper with aluminium is widely pursued in order to save weight and material costs, for battery components and wire connectors. Additionally, cost reductions can be further enhanced with effective reduction of energy consumption through efficient manufacturing. Therefore, friction stir spot welding as a solid-state welding technique is a potential choice with low energy demands and high joining performances. However, the joining of aluminium and its alloys with solid-state welding techniques is still a challenging task due to a persistent and chemically stable aluminium oxide layer formed at the sheets prior to the welding, due to the reaction between aluminium and atmospheric oxygen. In this paper, the influence of strain rate induced during friction stir spot welding process on the metallurgical, mechanical and electrical properties of friction stir spot welding of AA 5754-H111 was studied. The strain rate was calculated according to the rotational speed of the tool and the effective (average) radius and depth of the stir zone. It was observed that the specimens welded with a lower strain rate endured a 15 % higher average strain failure load compared to the specimens welded at a higher share rate. The microhardness profiles of the specimens obtained at low strain rates imply strain hardening mechanisms in the weld zone, while the microhardness of specimens welded at high strain rates expressed thermal softening. It was also found that the friction welded sheets, regardless of the strain rate, show increased electrical resistance compared to the base material, however, it decreases with an increase in strain rate. Microstructural analysis reveals a stress-induced metallurgical transformation in the narrow zone around the weld-faying interface.

Polyacrylamide gel synthesis of Ni1-xCuxAl2O4 nano-pigments with photocatalytic properties

Ni1-xCuxAl2O4 (x = 0, 0.25, 0.50, 0.75, and 1) nanoparticles were prepared via a polyacrylamide gel method. The compounds were characterized by Fourier Transform infrared spectroscopy, thermal analysis, X-ray diffraction, UV–vis diffuse reflectance, and scanning electron microscopy. The produced powders were studied for dual applications of pigment and photocatalyst. The results showed that a spinal structure with an average particle size of 70 nm was obtained via this polymer-assisted synthesis method. The substitution of copper in the structure of nickel aluminate caused an increase in crystallite size growth, whereas it decreased the band gap energy of the samples. DRS results demonstrated that the band gap energy of Ni1-xCuxAl2O4 with x = 0 reduced from 3.4 eV to 2.51 eV for the sample with x = 0.75. The CIE colorimetric values of the samples showed that the color of the nanoparticles changed from cyan for x = 0 to brown for x = 0.75. The photocatalytic investigations revealed that all the produced powders can effectively remove methylene blue pollution from water.

Cu-Substituted Hydroxyapatite Powder: Mechanochemical Synthesis Using Different Copper Sources and Thermal Stability

In this paper, we present results of a study on the possibilities of the mechanochemical synthesis of copper-substituted hydroxyapatite with the replacement of calcium cations by copper cations. During the synthesis, various reagents—sources of copper cations—were used. It was found that the nature of the carrier of the doping cation plays an important role in the formation of the structure of Cu-substituted apatite. It was established that a single-phase material forms most efficiently when copper (II) phosphate is employed; however, even this reagent did not allow the introduction of a large amount of copper into the hydroxyapatite crystal lattice. Out of 10 calcium cations in the unit cell of hydroxyapatite, no more than two could be replaced by copper cations. A further increase in the copper concentration led to the formation of an amorphous product. The degree of copper substitution in hydroxyapatite increases as the oxidation state of copper increases. The thermal stability of the hydroxyapatite with the highest degree of substitution was studied. It was shown that the presence of copper cations significantly decreases the stability of hydroxyapatite. In a temperature range of 550–750 °C, it is gradually decomposed to form a mixture of rhombohedral Ca2.57Cu0.43(PO4)2 and CuO. The FTIR spectrum of Ca2.57Cu0.43(PO4)2, which is a copper-substituted β-Ca3(PO4)2, was first studied.

Partial Substitution of Copper with Nickel for the Superconducting Bismuth Compound and Its Effect on the Physical and Electrical Properties

Partial Substitution of Copper with Nickel for the Superconducting Bismuth Compound and Its Effect on the Physical and Electrical Properties

High-conducting Bi4V1.8Cu0.2-xSbxO10.7+3x/2 ceramics: Structural, microstructural, electrical and optical properties

The partial substitution of copper by antimony in Bi4V1.8Cu0.2O10.7 compounds leds to the solid solution Bi4V1.8Cu0.2-xSbxO10.7+3x/2 (0.00 ≤ x ≤ 0.20). X-ray diffraction and thermal analysis showed that for all compositions, the obtained phases are isotype to the tetragonal γ or γ′ form of Bi4V2O11. The effect of Sb5+ doping on electrical conductivity was studied using electrochemical impedance spectroscopy in the temperature range 200–700 °C. The changes in slope observed in the Arrhenius plots correspond to the structural transitions that occur within the material. The band gap was determined by DRS spectra, BiCuSbVOx materials have a very low gap band (1.77–1.80 eV) compared to parent phase Bi4V2O11 and the most of BIMEVOX semiconductor materials. The band located around 860 cm−1 in Raman spectroscopy is attributed to V–O bond and more especially to V–O2 bond.

Element-Specific Study of Magnetic Anisotropy and Hardening in SmCo5-xCux Thin Films.

This work investigates the effect of copper substitution on the magnetic properties of SmCo5 thin films synthesized by molecular beam epitaxy. A series of thin films with varying concentrations of Cu were grown under otherwise identical conditions to disentangle structural and compositional effects on the magnetic behavior. The combined experimental and theoretical studies show that Cu substitution at the Co3g sites not only stabilizes the formation of the SmCo5 structure but also enhances magnetic anisotropy and coercivity. Density functional theory calculations indicate that Sm(Co4Cu3g)5 possesses a higher single-ion anisotropy as compared to pure SmCo5. In addition, X-ray magnetic circular dichroism reveals that Cu substitution causes an increasing decoupling of the Sm 4f and Co 3d moments. Scanning transmission electron microscopy confirms predominantly SmCo5 phase formation and reveals nanoscale inhomogeneities in the Cu and Co distribution. Our study based on thin film model systems and advanced characterization as well as modeling reveals novel aspects of the complex interplay of intrinsic and extrinsic contributions to magnetic hysteresis in rare-earth-based magnets, i.e., the combination of increased intrinsic anisotropy due to Cu substitution and the extrinsic effect of inhomogeneous elemental distribution of Cu and Co.