Ni Ag Research Articles

Structural characterization and mechanical properties of bicontinuous dual-metal composites prepared by liquid metal dealloying

Most bicontinuous dual-metal composites (BDMCs) generated by liquid metal dealloying (LMD) exhibit lamellar microstructures at the grain boundaries of initial precursor alloys, resulting in little to no ductility. Herein, grain-boundary-defect-free bicontinuous Ni/Ag composites consisting of network-like dealloying structures (Ni phase) and solidified matrices of liquid metal corrosive media (Ag phase) are prepared. Then, a detailed study of their intrinsic structures and mechanical properties under uniaxial tension is conducted. This composite is found to be completely dense without visible holes or cracks. Both the Ni phase and Ag phase have independent open porous structures and are well bonded with clear interfaces, forming a dual-interlocking structure with phase-to-phase and grain-to-grain interlocking. This structure does not significantly affect the elastic modulus or tensile yield strength, but under specific conditions, it can enhance the tensile ductility because of the coordinated deformation between the two phases, thereby reducing the likelihood of stress concentration and delays necking. Moreover, these bicontinuous Ni/Ag composites display superior strain hardening rates in comparison to pure Ag. The high strength and ductility of this structure warrant the exploration of its practical application in many areas, if more defect-free systems are synthesized by optimizing the LMD process in the future.

Synthesis and antimicrobial behaviour of NiO/Ag-based material

The main objective of the present work is the green synthesis of NiO and Ag nanoparticles using the leaf extract of Azadirachta indica and the development of NiO/Ag-based nanocomposites via an ultrasonic process. The synthesised NiO/Ag was characterised using different analytical methods and used as an antimicrobial agent against different bacterial and fungal strains. The antimicrobial study was done using the well diffusion method. The FTIR study indicated the presence of O–H, C–H (methylene or methyl), CO, O–H, and Ni–Ag, Ag–O, or Ni–O bonds on the surface of NiO/Ag. The XRD peaks of NiO/Ag were found to be 31.60 (103), 37.30 (111), 38.10 (111), 43.40 (200), 62.90 (220), 76.50 (008), 77.50 (311), and 79.50 (222), respectively. The maximum zones of inhibition were found to be 21.6 (±0.71), 21.2 (±0.69), 17.9 (±0.39), 13.3 (±0.81), and 12.3 (±0.38) mm against Escherichia coli, Staphylococcus aureus, Salmonella enterica, Candida albicans, and Aspergillus niger after incubation periods. On the basis of these findings, we can conclude that NiO/Ag is a potent antimicrobial agent against a variety of bacterial and fungal species.

Effect of Ag content on the friction and wear properties of electrodeposited self-lubricating Ni–Ag coating

Thin film coatings are required to improve the performance of components to resist harsh environments as the modern industry grows. In this study, Ni–Ag coatings with various Ag content were deposited on the Cu surface using an electrodeposition technique. The Ni–Ag coatings were deposited to enhance the tribological properties of the coatings and increase the service life of the friction-sliding components. Ni–6wt%Ag, Ni–8wt%Ag, and Ni–10wt%Ag coatings were deposited. A solid solution of Ni–Ag was formed in the coatings. As the concentration of NiSO4 decreased in the electrolyte, the content of Ag in the coatings increased with the granular morphological characteristics. The increase in Ag content reduces the coefficient of friction (CoF) on comparing the initial running-in period and is stable after some time. The initial decrease was due to the surface roughness. The CoF and wear rate were low for all Ag contents compared to the copper substrate due to the effect of Ag solid lubricant material in prepared coatings.

Enhanced properties of nickel–silver codoped hydroxyapatite for bone tissue engineering: Synthesis, characterization, and biocompatibility evaluation

Hydroxyapatite (HAp) is the most well-known bioceramic and widely utilized in bone tissue regeneration. Hydroxyapatite is biocompatible and bioactive however, it lacks osteogenesis, angiogenesis, and antibacterial properties. In the current study, we synthesized and evaluated a novel nickel (Ni) and silver (Ag) codoped hydroxyapatite (HAp) in comparison to undoped HAp and individually doped HAp samples. Extensive physicochemical characterizations like XRD, TEM, FE-SEM/EDS, FTIR, Raman spectroscopy, and TGA were performed, confirming the crystal structure and morphology of the synthesized HAp samples. All HAp samples exhibited elongated spherical-like nanoparticle morphologies with lengths between 34 and 44 nm and widths between 21 and 26 nm. The presence of dopant atoms, Ag and Ni, were observed in the doped/codoped HAp samples by EDS elemental mapping. Biocompatibility assessments using pre-osteoblast cells indicated high cell viability for all the doped and undoped HAp samples. Osteoinduction potential through alkaline phosphatase (ALP) activity measurements and alizarin red S (ARS) staining revealed enhanced calcium deposition in the presence of Ni–Ag codoped HAp compared to other HAp samples and control groups. This highlights the importance of Ni–Ag co-doping in promoting osteogenesis, surpassing the effects of silver doped HAp and nickel doped HAp. The potential of this novel Ni–Ag codoped HAp to induce osteogenesis in pre-osteoblast cells makes it a promising material for various applications in bone tissue engineering.

Cobalt Prospectivity Using a Conceptual Fuzzy Logic Overlay Method Enhanced with the Mineral Systems Approach

AbstractThis paper describes mineral prospectivity research conducted in Finland to predict favorable areas for cobalt exploration using the “fuzzy logic overlay” method in a GIS platform and public geodata of the Geological Survey of Finland. Cobalt occurs infrequently as a core product in mineral deposits. Therefore, we decided to construct separate conceptual mineral prospectivity models within the Northern Fennoscandian Shield, Finland, for four deposit types: (1) “Orthomagmatic Ni–Cu–Co sulfide deposits,” (2) “Outokumpu-type mantle peridotite-associated volcanogenic massive sulfide (VMS)-style Cu–Co–Zn–Ni–Ag–Au deposits,” (3) “Talvivaara black shale-hosted Ni–Zn–Cu–Co-type deposits” and (4) “Kuusamo-type (orogenic gold with atypical metal association) Au–Co–Cu–U–LREE deposits”. In addition, we created a model combining till geochemical data with data derived from bedrock drilling and mineral indications, including boulders and outcrops. The mineral prospectivity models were statistically tested with the “receiver operating characteristics” method using exploration drilling data from known mineral deposits as validation sites. In addition, the predictive performance of the models was evaluated by using success rate curves, where the number of previously identified deposits was compared with the area coverage of the predicted highly favorable areas. These results indicate that the knowledge-driven mineral prospectivity method using parameters derived from mineral systems models is effective in defining favorable exploration target areas at the regional scale. This study's innovation lies in its comprehension of the process of evaluating mineral prospectivity when the commodity of interest is not the primary commodity within the mineral system.

Structural and mechanical properties of NiTiAg shape memory alloys: ab-initio study

The austenite phase of Ni50−x Ti50Ag x for different concentrations (x = 1, 1.5, 2, 3, 5, 7, 8, 10) has been analyzed in this work. The ground state, structural, and mechanical characteristics of Ni50−x Ti50Ag x for various concentrations are examined under ambient conditions. From total energy as well as formation energy calculations, it is found that the stability of Ni50−x Ti50Ag x austenite phase is increased up to x = 5 and after that it becomes unstable in nature. These results are in good agreement with our experimental results. The experimental and other theoretical results agree with the estimated lattice parameter values. The x-ray diffraction and differential scanning calorimetry reveal the phases formed and transformation characteristics of NiTiAg alloys. The elastic constants, bulk modulus, shear modulus, Poisson’s ratio, and elastic anisotropy factor of Ni50−x Ti50Ag x are examined at ambient conditions for different concentrations. From elastic constant calculations, it is also found that the austenite phase of Ni50−x Ti50Ag x is mechanically stable up to x = 5 and after that it does not obey Born–Huang criteria and becomes unstable. The Ni45Ti50Ag5 composition is found to be the stiffest and hardest material. According to Poisson’s ratio calculations, Ni50−x Ti50Ag x shows that the Ti–Ag, Ni–Ag bonding is more directed in nature. The austenite phase of Ni50−x Ti50Ag x is more incompressible because the Poisson’s ratio is nearly equal to the optimum value (0.5).

Ni–Ag ferrites synthesized by sol gel route using aloe vera extract as a solvent: Enhancement in structural, dielectric, magnetic and optical properties

The Ag+ doped nanocrystalline nickel ferrites, NiAgxFe2-xO4 (NAF) with x = 0–0.1 were synthesized by sol gel route using aloe vera extract as a solvent. The analysis of X-ray diffractogram reveals the creation of spinel phase within the pristine Ni ferrite. The phase of nano Ag particles coexists along with the spinel phase for doped NAF, which was confirmed by the Rietveld refinement of XRD patterns. The wt. % of metallic nano Ag and spinel phase was calculated from the refined XRD data. The mean size of the ferrite crystallites calculated from Debye-Scherer method was 44 nm. The TEM analysis confirms the nanocrystalline nature of the ferrites. The SAED image of the ferrite confirms the creation of spinel phase within the ferrite. The morphological analysis by SEM explores the layered arrangement of spherical nanoparticles within the NAF crystals. The EDS analysis shows the absence of impurity elements in the synthesized ferrites. The dielectric constant and loss tangent were studied as a function of frequency and Ag+ composition. The analysis of hysteresis loops depicts the soft magnetic behavior of the NAF samples. The optical properties of NAF crystals were studied from the UV Vis absorption spectra within the wavelength range 400–800 nm. The band gap energies were decreased with the increasing Ag+ composition due to the contribution of delocalized electrons in direct optical transitions.

Improvement of Heat Dissipation in Ag/Ni Substrates for Testing Cu-TiO2/TiO2-Modified Filters Using SERS Spectroscopy

Surface-enhanced Raman scattering (SERS) spectroscopy is used to investigate a composition of wash swabs from the Cu-TiO2/TiO2-modified filters with disinfecting ability. Macroporous Si chips coated with conformal 800 nm thick Ni layer and Ag particles (Ag/Ni) are engineered to act as SERS-active substrates. Such substrates are characterized by a moderate reflection band in the visible range and provide an improved heat dissipation from contaminants in wash swabs during SERS study. This prevents thermal-induced destruction of analyzing media for reliable assessment of its composition. The anatase Cu-TiO2 and TiO2 nanoparticles are synthesized using the sol-gel method and characterized via Raman spectroscopy and X-ray diffractometry. The filters are modified with Cu-TiO2/TiO2 nanoparticles and embedded in three-valve facial masks that are worn by a volunteer to breathe for 4 h. Comparative SERS analysis of the filters shows that they slightly destroy chemical bonds in the molecules constituting airborne contaminations upon ceiling day lights, which can be associated with Cu-TiO2 photocatalytic activity. The filters additionally exposed to near-ultraviolet light prominently decrease the intensity of Raman signatures of airborne contaminant due to the presence of pure TiO2.

The origin of the P-type conductivity for Cu and Ag-doped NiO: Density functional theory study

NiO, as a promising transparent p-type semiconductor, was intensively studied in experiment. Due to the difference of fabrication methods and defects concentration, it is difficult to make meaningful comparisons. In this work, the performance for Cu and Ag-doped NiO is fully evaluated by using the density functional theory method. Electronic structures show Cu and Ag substituting Ni (labeled as Cu Ni and Ag Ni ) are deep acceptors, and the ionization energy ε(0/-) for Cu Ni and Ag Ni are much higher than 0.20 eV. Our studies show the p-type conductivity for Cu and Ag-doped NiO mainly stems from the coexistent Ni vacancies (labeled V Ni ). The ionization energy ε(0/-) for Cu Ni (Ag Ni ) plus V Ni are 0.086 (0.012) eV. Under O-rich condition, the compounds M 2 O 2 and M 2 O (M = Cu and Ag) are promising dopants sources. We expect this work could promote the fundamental understanding of the p-type conductivity for nonstoichiometric NiO as well as the Cu and Ag-doped NiO. The data that supports the findings of this study are available from the corresponding author upon reasonable request.

Effects of Ni-NCAL and Ni–Ag electrodes on the cell performances of low-temperature solid oxide fuel cells with Sm0.2Ce0·8O2-δ electrolyte at various temperatures

Three low-temperature solid oxide fuel cells are built using Sm0.2Ce0·8O2-δ (SDC) as the electrolyte. Cell A is symmetrical and features Ni–LiNi0.8Co0·15Al0·05O2 (Ni–NCAL) electrodes, Cell B comprises a Ni–NCAL anode and a Ni–Ag cathode, and Cell C is fabricated using a Ni–NCAL cathode and a Ni–Ag anode. The ohmic resistance and polarization resistance (Rp) of Cells B and C are significantly higher than those of Cell A. The reduction of NCAL at the anodes of Cells A and B yields LiOH and Li2CO3 phases, and the Ni particles generated on the surfaces of the NCAL particles improve the catalytic activity of the cells. Li2CO3–LiOH melts at temperatures >450 °C and penetrates the porous SDC electrolyte layer, causing its densification and abnormal grain growth and increasing its ionic conductivity to >0.2 S/cm at low temperatures. The high open-circuit voltages (OCVs) (0.970–1.113 V) of the cells during electrochemical measurements are ascribed to the Li2CO3–LiOH phase which serves as an electron-blocking layer for the SDC electrolytes. As the reduction of NCAL approaches completion, the anode comprises only Ni phase, which hinders the charge transfer process. The triple-phase-boundary (TPB) area at cathode of Cell B is significantly lower than that of Cell A; therefore, the catalytic activity of Cell B for the oxygen reduction reaction is lower than that of Cell A. Consequently, the maximum power density (MPD) of Cell B is less than half of that of Cell A. The large Rp value of Cell C is ascribed to its low TPB area at Ni–Ag anode which has no reaction with H2 during operation. No visible sintering of the SDC electrolyte layer is observed for Cell C; therefore, its ionic conductivity is considerably smaller than those of the electrolyte layers of Cells A and B. The OCVs of Cell C (0.281–0.495 V) are significantly lower than the typical OCVs of ceria-based SOFCs. This is attributed to the porous SDC electrolyte layer of Cell C. The large Rp values and the low OCVs contribute to the low MPDs of Cell C at various temperatures.

Effects of LiNi0.8Co0.15Al0.05O2 electrodes on the conduction mechanism of Sm0.2Ce0.8O2−δ electrolyte and performance of low-temperature solid oxide fuel cells

In this study, three low-temperature solid oxide fuel cells are constructed using Ce0.8Sm0.2O2−δ (SDC) as the electrolyte and Ni–LiNi0.8Co0.15Al0.05O2 (Ni–NCAL) and Ni–Ag as the electrodes. Cell A with symmetrical Ni–NCAL electrodes exhibits the best electrochemical performance. During operation, the Ni–NCAL anode is reduced by H2atmosphere to form LiOH and Li2CO3. The Li2CO3–LiOH melt produced at >450 °C permeates the SDC electrolyte layer, causing its densification and grain growth in addition to the Li+-ion doping of SDC grains. The maximum electrical conductivity of the Li+-ion-doped SDC at 550 °C is at least one order of magnitude smaller than that of the SDC–Li2CO3–LiOH composite electrolyte (0.331 S cm−1). The ohmic and polarization resistances of Cell A at 550 °C are 0.168 and 0.256 Ω cm2, respectively, and its open-circuit voltage is 1.065 V, indicating the presence of dense SDC electrolyte and electron-blocking layers. The maximum power density of the cell at 550 °C is 535.2 mW·cm−2, which is primarily due to the high catalytic activity for the hydrogen oxidation and oxygen reduction reactions at the electrodes and large electrical conductivity of the SDC–Li2CO3–LiOH composite electrolyte at low temperatures.

Ni–Ag Supported on Reduced Graphene Oxide as Efficient Electrocatalyst for Alcohol Oxidation Reactions

Ni–Ag Supported on Reduced Graphene Oxide as Efficient Electrocatalyst for Alcohol Oxidation Reactions

In situ de-wetting of liquid–solid interface to fabricate spherical Ag@Ni immiscible alloys

Spherical Ag@Ni immiscible alloy powders were successfully fabricated combining in situ de-wetting of metal droplets from a metalloid solid medium with phase separation of immiscible alloys. The effects of atom ratio and temperature on morphology, structure, and phase separation were investigated. The spherical morphology of alloy powders confirmed the de-wetting of the liquid–solid interface between the liquid Ni–Ag immiscible alloy and the solid alumina powder medium. The Ni-rich phase was scattered in the Ag-rich phase matrix at 1673 K while the spherical Ni-core at the center was surrounded by a ring-shaped shell of Ag at the outer layer with an egg-type structure at 1753 K. The egg-type microstructure of the Ni–Ag particle resulted from the liquid–liquid immiscible phase separation. Such spherical Ag@Ni alloy powders with an egg-type microstructure have a good combination of a high strength Ni-rich phase core and a high electric and thermal conductivity Ag-rich phase shell with many potential advanced applications in electronic packaging.

Preparation of a cost-effective Ni–Ag bimetallic catalyst for hydrodehalogenation of aryl halides under mild conditions

A novel bimetallic Ni–Ag catalyst was prepared, exhibiting excellent catalytic performance in hydrodehalogenation of aryl halides under mild conditions. It provided a green and cost-effective method for the degradation of aryl halide pollutants.

Synthesis of Ni-Ag-ZnO solid solution nanoparticles for photoreduction and antimicrobial applications.

ZnO is one of the most promising and efficient semiconductor materials for various light-harvesting applications. Herein, we reported the tuning of optical properties of ZnO nanoparticles (NPs) by co-incorporation of Ni and Ag ions in the ZnO lattice. A sonochemical approach was used to synthesize pure ZnO NPs, Ni–ZnO, Ag–ZnO and Ag/Ni–ZnO with different concentrations of Ni and Ag (0.5%, 2%, 4%, 8%, and 15%) and Ni doped Ag–ZnO solid solutions with 0.25%, 0.5%, and 5% Ni ions. The as-synthesized Ni–Ag–ZnO solid solution NPs were characterized by powdered X-ray diffraction (pXRD), FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV-vis (UV) spectroscopy, and photoluminescence (PL) spectroscopy. Ni–Ag co-incorporation into a ZnO lattice reduces charge recombination by inducing charge trap states between the valence and conduction bands of ZnO and interfacial transfer of electrons. The Ni doped Ag–ZnO solid solution NPs have shown superior 4-nitrophenol reduction compared to pure ZnO NPs which do not show this reaction. Furthermore, a methylene blue (MB) clock reaction was also performed. Antibacterial activity against E. coli and S. aureus has inhibited the growth pattern of both strains depending on the concentration of catalysts.

Geology and Mineral Chemistry of Uranium‐ and Thorium‐bearing Minerals in Rare‐Metal (NYF) Pegmatites of Um Solimate, South Eastern Desert, Egypt

AbstractThe garnet muscovite granitic pegmatite of Um Solimate, in southern Egypt, represents a promising asset for strategic and economic metals, especially Bi–Ni–Ag–Nb–Ta as well as U and Th. The ore bodies occur as large masses, pockets and/or veins of very coarse‐grained pegmatites, which consist mainly of K‐feldspar, quartz and albite with subordinate muscovite, garnet, and biotite. Radiometric data revealed that eU‐ and eTh‐contents of the pegmatites reach up to 39 ppm and 82 ppm, respectively. The studied pegmatites are enriched in primary U and Th minerals (uraninite, coffinite, thorianite and uranothorite) as well as Hf‐rich zircon and monazite, which give rise to anomalous radioactive zones. Niobium‐tantalium‐bearing minerals (i.e. ferrocolumbite, microlite and uranopyrochlore), xenotime, barite, galena, fluorite, and apatite are ubiquitous, and, consequently, the studied pegmatites belong tothe Niobium–Yttrium–Fluorine‐type (NYF) family. The noble metal mineralization includes argentite (Ag2S), native Ni and Bi as well as bismite and bismoclite. In addition, beryl and tourmaline are observed in pegmatites near the contact with metasediments and ultramafic bodies. The observed compositional variations of Ta/(Ta+Nb) and Mn/(Mn+Fe) ratios in columbite (0.08–0.45 and 0.11–0.57, respectively) and Hf contents in zircon (3.54–6.46 wt%) may reflectan extreme degree of magmatic fractionation leading to formation of the pegmatite orebody.

Synergistic effect of photo-reduced Ni–Ag loaded g-C3N4 nanosheets for efficient visible Light‐Driven photocatalytic hydrogen evolution

A heterogenous ternary Ni and Ag co-modified g-C3N4 nanocomposite is designed and fabricated using a photoreduction approach for photo-catalytic hydrogen production from methanol-water mixture. Ternary nanocomposite consisting of Ni–Ag co-deposited onto g-C3N4 was successfully fabricated and uniformly distributed, therefore, exhibited strong visible-light absorption and efficient charge carrier separation due to synergistic effect throughout the ternary composite. The nanocomposite with varying amounts of nickel and silver, play an important role to maximize the photoactivity with the optimized 3Ni–1Ag/CN sample delivering H2 of 2137.5 μmolg−1h−1, which is 16.13, 1.42 and 1.52 folds greater than using CN, 3Ni/CN and 3Ag/CN, respectively. This proves that semiconductor composition ratio is important in achieving a successful p-n junction and efficient charge separation and transfer in the ternary composite. The performance of optimized Ni–Ag/CN was further enhanced using photo-reduction method. The highest H2 yield of 5740 μmolg−1 is achieved over the photo-reduced Ni–Ag/CN-R nanocomposite which is 1.25 folds higher than non-photo-reduced composite. This improvement can be accredited to the formation of good p-n junction between the semiconductors in the ternary composite and due to the formation of photo-reduced Ag which acts as electron sinks which leads to improved charge separation. Furthermore, increasing catalyst loading increases the H2 production rate and methanol-water mixture gave the highest H2 production rate. The findings of this study would be beneficial for future hydrogen generation and implementation within newer sustainable systems.

Cu–Ag and Ni–Ag meshes based on cracked template as efficient transparent electromagnetic shielding coating with excellent mechanical performance

Cu–Ag and Ni–Ag meshes based on cracked template as efficient transparent electromagnetic shielding coating with excellent mechanical performance

Plasmonic Ag supported on Ni-doped TiO2 nanospheres for rapid microbial inactivation under visible light

Ni-doped TiO2 nanospheres decorated with silver plasmonic nanoparticles (Ni-TiO2/Ag) have been successfully synthesized via sol-gel method and photo-deposition approach. In contrast with pure TiO2 and Ni-TiO2, the Ni-TiO2/Ag composite photocatalysts exhibit markedly enhanced visible-light photocatalytic sterilization efficiencies towards Escherichia coli (E. coli). And more importantly, antifungal experiment reveals that the composite can also disinfect ca. 2.0 log10 cfu·mL−1Fusarium graminearum (F. graminearum) macroconidia within 3 h. The highly efficient antimicrobial activities are ascribed to the introduction of Ni doping and Ag nanoparticles, which increases the visible light utilization and promotes the separation of electron-hole pairs. The photocatalytic disinfection mechanism is studied with scavengers trapping experiments and electron spin-resonance spectroscopy (ESR), which verifies the key role of •O2- and •OH during the microbial inactivation. Our study indicates that the Ni-TiO2/Ag nanocomposite has great potential for use in pathogenic microorganism remediation.

The Role of Phase Separation on Rayleigh-Plateau Type Instabilities in Alloys

Classical molecular dynamics (MD) simulations are used to investigate the role of phase separation (PS) on the Rayleigh-Plateau (RP) instability. Ni–Ag bulk structures are created at temperatures (...