Ag Phase Research Articles

Silver-doped graphite oxide composites used as antimicrobial agents against Staphylococcus aureus, Escherichia coli and Tatumella terrea evaluated by direct TLC bioautography

Silver-doped graphite oxide composites presented mixed Ag and Ag2O crystalline phases accompanied by C/O and ID/IG average ratios of 2.13 and 1.16, associated with a good oxidation degree and high structural disorder or defects in the carbon material, respectively. The low-silver-doped GrO composite showed homogenous silver particle dispersion and a low particle size distribution (96 nm). However, high-silver-doped GrO composites generated materials with high relative crystallinity, silver particle agglomeration, and Ag metal phase promotion. At 3 and 5 mg ml−1 per chromatographic plate, the silver-doped graphite oxide composites were tested by direct TLC bioautography against Staphylococcus aureus, Escherichia coli, and Tatumella terrea microorganisms, where the minimum inhibitory concentration was 3 mg ml−1 per chromatographic plate. At 3.0 mg ml−1 per chromatographic plate, high-silver-doped GrO composites exhibited a 39%, 3.2-fold, and 83% higher retention factor (R f ) compared with the composites with low-silver-doped GrO composites against S. aureus, E. coli, and T. terra microorganisms, respectively. However, both composites showed similar inhibition capacities at 5.0 mg ml−1 per chromatographic plate against the three microorganisms. This behavior may be associated with both composites reaching the threshold limit. In general, the silver acetate amount used in the silver-doped GrO composites influenced the dispersion, crystalline phase promotion, particle size distribution, and the silver particle release capacity, which modified the electrostatic adsorption type between the composites and the bacterial cell walls.

Gelation of acrylic acid with Ag+ and conversion to Ag nanoparticle as potential system for biomedical applications

Silver (Ag) has been used to cross-link poly (acrylic acid) (PAAc) to obtain antibacterial nanocomposite hydrogel for controlled drug delivery systems. Ag+/PAAc composite hydrogel was prepared by free radical aqueous polymerization of acrylic acid (AAc) using potassium persulfate (KPS) as the initiator in the presence of silver nitrate (AgNO3). Sodium borohydride (NaBH4) was used to reduce the Ag ions present within the hydrogel matrix to generate Ag nanoparticles (Ag NPs). Transmission electron microscopy (TEM) characterization of the sample indicated the formation of Ag nanoparticles that distributed uniformly in the PAAc networks. UV–visible spectrophotometry showed an absorption peak at 425 nm that attribute to the well-known surface Plasmon resonance of the Ag bound in NPs. X-ray diffraction (XRD) pattern showed the appearance of some peaks corresponding to the face-centered cubic (f.c.c.) Ag phase. Energy dispersive spectroscopy (EDS) studies revealed that Ag NPs are successfully formed inside the Ag+/PAAc composite hydrogel. The gelation and crosslinking of PAAc chains with Ag+ by strong interactions between Ag cations and polyanions, deprotonated carboxylic groups of PAAc were identified from the Fourier transform infrared (FTIR) spectrogram. Field emission scanning electron microscopy (FESEM) exhibited an interconnected porous structure with an average pore size of about 10 μ for composite hydrogel that can absorb 440 g water/g dried sample. Dried samples were also loaded with amoxicillin and antibiotic release was studied. The antimicrobial activity of the Ag+ and Ag-NPs hydrogels was tested against Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa and Escherichia coli.

Designing bi-functional Ag-CoGd0.025Er0.05Fe1.925O4 nanoarchitecture via green method

In the current study, we developed a simple and biocompatible method for producing core–shell nanoparticles (NPs). Citrate auto combustion and green procedures were used to create core–shell Ag/CoGd0.025Er0.05Fe1.925O4 (Ag/CGEFO) sample with an average crystallite size of 26.84 nm. The prepared samples were characterized via different structural techniques, such as x-ray diffraction (XRD), Raman Spectroscopy (RS), High-Resolution Transmission Electron Microscopy, and Energy Dispersive x-ray analysis. These analyses were utilized to characterize and confirm the successful formation of the core–shell architecture. For core–shell NPs, all peaks of Ag and CGEFO ferrite are detected in the XRD, confirming the co-presence of the ferrite spinel phase and the cubic Ag phase. The magnetic hysteresis curves demonstrate typical hard ferri-magnetic behavior along with maximum magnetic saturation values up to 53.74 emu g−1 for the CGEFO sample, while an enhanced coercivity is detected for the coated sample. Moreover, the width of the hysteresis loop is increased for the Ag/CGEFO sample compared to the uncoated one. This indicates that the addition of Ag as a shell increases magneto crystalline anisotropy. Moreover, the E g of uncoated CGEFO is equal to 1.4 eV, increasing to 3.6 eV for coated ones. This implies the influence of CGEFO is diminished when the surface is coated with Ag (shell), and the reflectance of the Ag/CGEFO core–shell is nearly dependent on the reflectance of the Ag shell layer. Consequently, the Ag/CGEFO can be used as a light shielding substance.

Fabrication and properties analysis of paraffin@TiO2/Ag phase change microcapsules for thermal energy storage and photocatalysis

To develop a material that can be applied in the field of thermoregulation materials for residential buildings and degradation of organic pollutants. A novel microencapsulated phase change material, paraffin@TiO2/Ag, was prepared using interfacial condensation technology. The paraffin@TiO2/Ag microcapsules' melting point and latent heat were 48.00 °C and 63.56 J/g, respectively, according to the DSC study results, and their encapsulation rate was 46.11 %. In addition, the experimental results of photocatalytic degradation of MB (methylene blue) showed that the paraffin@TiO2/Ag microcapsules had high photocatalytic activity for organic dyes under natural light, and the degradation rate of MB reached 99 % when the light exposure time reached 4 h. By comparing the reaction rate constant of MB by paraffin@TiO2 microcapsules (0.98969 h−1) with that of MB by paraffin@TiO2/Ag microcapsules (1.15845 h−1), it was learned that the introduction of Ag nanoparticles effectively improved the photocatalytic activity of the phase change microcapsules.

Unlocking the Potential of Li–Ag Alloys: Phase Selection and Practical Application

Dendrite formation, contact loss, and continuous formation of the solid electrolyte interphase (SEI) preclude the practical use of the energy-dense lithium (Li) metal. Li–Ag alloys have the potential to address these issues due to their exceptional lithiophilicity, outstanding mechanical stability, and moderate chemical stability. This study evaluates all phases in the Li–Ag phase diagram based on lithiation capacity, Li insertion, mechanical property, and chemical stability. Our findings suggest that Li 4 Ag is the most promising phase, and the Gibbs free energy of nucleation (∆ G nucle ) for Li–Ag alloys is 3 to 5 orders of magnitude smaller compared to pure Li, resulting in uniform nucleation and deposition behavior. We proposed practical applications within the Li 4 Ag phases or from the Li 9 Ag 4 to the Li 4 Ag phases, which may provide a usable capacity of 409 to 696 mAh/g, respectively. Experiments indicate that Li 4 Ag exhibits not only the smallest impedance but also the highest capacity retention compared to Li 9 Ag 4 and pure Li. The study provides valuable guidance for the selection and application of Li-containing alloys in future battery development.

Vapor–liquid–solid synthesis of Ag2Te using chemical vapor deposition method

Silver telluride, Ag2Te, has been selectively synthesized by conventional chemical vapor deposition (CVD) via the vapor–liquid–solid growth mechanism. The pre-deposited Ag film on the SiO2/Si substrate was chemically reacted with vaporized Te atoms and transformed into liquid-phase Ag–Te during the CVD process. The appropriate supply of Te vapor to the Ag film influenced the stoichiometry of Ag–Te compounds, and the formation of stoichiometric Ag–Te compounds was well-explained by the phase diagram of the Ag–Te system. We found that Ag2Te was grown in the liquid of Ag–Te under the Te-poor condition, while Ag5Te3 and Te were simultaneously solidified under the Te-rich condition. The high-temperature synthesis of Ag2Te showed higher crystallinity and better stoichiometry than the low-temperature synthesis. This study demonstrates that Ag2Te can be selectively synthesized by conventional CVD via delicate control over the phases of the complex Ag–Te system.

Daylight-driven catalytic removal of pyridine over Ag-embedded ZnO porous nanosheets

Structure of heterogeneous photocatalyst with adequate coupling interface has an important effect on energy transfer and photoinduced electron-hole pairs separation. In this work, Ag-embedded ZnO heterogeneous porous nanosheets (PNSs) have been synthesized by thermal pyrolyzing of Ag2CO3-modified Zn5(CO3)2(OH)6 nanosheets at 400 °C. Photoelectron spectra and X-ray diffraction measurements demonstrate that there exists an adequate coupling between Ag and ZnO phase. Ag-embedded ZnO PNSs, in contrast to bare ZnO PNSs, performs 6-fold enhancement in natural-daylight-driven degradation of pyridine which requires participation of ·OH radicals. This result demonstrates that the adequate coupling interface between Ag and ZnO for Ag-embedded ZnO PNSs promotes an energy transfer from local surface plasma resonance of Ag nanoparticles to bound excitons in ZnO region, activating them to dissociate into free photoinduced carriers. In addition, external control experiments indicate that the best photocatalytic degradation is obtained in the 7–10 pH range of 10 mg/L pyridine solution in presence of 0.5 g/L photocatalyst dosage. The optimal Ag-embedded ZnO PNSs under outdoor daylight irradiation also performs an efficiently photocatalytic degradability for pyridine present in ground water. Our work provides a new approach to fabricate ZnO-based photocatalyst with efficient energy transfer for treating stubborn organics present in polluted water.

Facile gamma-ray induced synthesis of reduced graphene oxide decorated with silver nanoparticles: a green approach for symmetric supercapacitor applications

This study presents a green, novel, one-pot, and single-step method for synthesizing reduced graphene oxide/silver nanocomposites (RGO/Ags) with different Ag ratios using Roselle extract and 80kGy of γ-ray for symmetric supercapacitor applications. As a natural antioxidant, Roselle extract served as a scavenger of oxidative free radicals to inhibit the oxidation of graphene oxide/silver nitrate suspensions (GO/AgO3), which were undergoing radiolysis under γ irradiation. An additional sample of GO/AgO3 was irradiated with the same dose in the absence of Roselle for comparability. The efficient reduction of GO/AgO3 has been assessed by several analytical techniques, including XRD, FTIR, TEM, and Raman spectroscopy. The presence of Roselle hindered the formation of the AgO phase while concurrently promoting the construction of the Ag phase. Furthermore, using Roselle extract results in a more homogeneous dispersion of spherical silver nanoparticles on reduced graphene oxide (RGO) sheets. Symmetric supercapacitor has been assembled from arbitrary samples amongst RGO/Ags, which showed good performance like low internal resistance and suitable specific capacitance (96 F/g at current density 0.2 A/g). The findings point to the merit of RGO/Ag nanocomposites prepared by the synergetic effect of γ-ray and Roselle extract as an efficient supercapacitor material.

Investigating on the microstructure and optical properties of Au, Ag and Cu implanted TiN thin films: The effects of surface oxidation and ion-induced defects

In the present paper, the effects of metal ion implantation on the structural and optical properties of TiN thin films have been investigated. TiN films of 170 nm thickness were grown by d.c. reactive sputtering on Si (100) wafers and then irradiated at 5 × 1016 ions/cm2 with either Au, Ag, or Cu ions by using two different energies per each implanted metal. The results showed that as deposited TiN crystallizes in the form of a fcc cubic structure, with the crystallites preferentially oriented along the (111) plane. For all implanted layers, the cubic structure was preserved, but compared to as deposited TiN the crystallites were smaller and the lattice was contracted. These changes were correlated with the depth distribution of Au, Ag and Cu ions and assigned to implantation-induced damage that was larger when higher ion energies were used. High-resolution XPS spectra of the surface of as deposited sample showed the coexistence of TiN, TiO2 and TiOxNy phases and this was related to the surface oxidation of the films due to the exposure to air. After implantation, the results were almost similar for all metals, showing an increase in TiO2 contribution and the formation of pure metallic Au and Ag phases, while copper is in the Cu2+ state, which is attributed to Cu(II)-oxide and Cu(OH)2. The microstructural characteristics including defect formation, changes in crystallite size and lattice contraction, and also growth of different metallic phases during implantations were correlated with the findings of the optical characterization of the implanted films. For the as deposited film we found an energy gap of 2.91 eV, which was lower than the value typical for TiN. After implantation the gap was shifted to higher energies, while at the visible part of the region, the existence of additional energy levels, at photon energies below 2.9 eV was observed. Besides, all implanted films showed degraded photocatalytic activity compared to as deposited TiN, among which Cu-implanted samples exhibited the best photocatalytic performances. The lower photocatalytic activity of Au and Ag implanted films compared to Cu implantations was ascribed to larger structural defects and the formation of less favorable electronic states.

Complexity in the Au–Ag–Hg system: New information from a PGE (‘osmiridium’) concentrate at Waratah Bay, Victoria, Australia

AbstractAu–Hg–Ag phases have been described from a variety of metallogenic orebodies and the placer deposits derived from them. In many documented placer deposits, the phases typically occur intergrown as ‘secondary’ rims to primary Au–Ag grains. The origin of these rims has been ascribed to supergene redistribution reactions during deposition or to the effects of amalgamation (i.e. use of mercury) during mining for gold. Difficulties in determining compositions and crystal structures on such a small scale have made full characterisation of these phases problematic. This paper describes a new occurrence of these phases, found by accident during investigation of a historical concentrate of ‘osmiridium’ containing a number of gold grains from beach sands at Waratah Bay, in southern Victoria, Australia. The phases occur as rims to gold grains and are intergrown on a scale of tens of micrometres or less. Application of electron microprobe analysis (EPMA) and limited electron back-scattered diffraction (EBSD) was required to characterise them. These techniques revealed the presence of the approved mineral weishanite (Au–Hg–Ag) and a phase with compositional range Au2Hg–Au3Hg surrounding primary Au–Ag (electrum) containing trace amounts of Hg. EBSD analysis showed weishanite is hexagonal P63/mmc and Au2Hg to be hexagonal P63/mcm. Comparison with published data from other localities (Philippines, British Columbia and New Zealand) suggests weishanite has a wide compositional field. Textures shown by these phases are difficult to interpret, as they might form by either supergene processes or by reaction with anthropogenic mercury used during mining. However, in the absence of any historical evidence for the use of mercury for gold mining at Waratah Bay, we consider the formation of the Au–Hg phases is most probably due to supergene alteration of primary Au–Ag alloy containing small amounts of Hg. In addition to revealing some of the reaction sequences in the development of these secondary Au–Hg–Ag rims, this paper illustrates methods by which these phases can be more fully characterised and thereby better correlated with the Au–Hg synthetic system.

Microstructure, mechanical properties and hermeticity of W-Cu/HTCC brazed joints with surface metallization

WCu alloy and high temperature co-fired ceramic (HTCC) were metallized through electroless nickel plating, then one series of W-Cu/Ni/AgCu/Ni/HTCC joints were successfully brazed with AgCu filler. The microstructure, mechanical properties, and hermeticity of W-Cu/HTCC joints were systematically investigated, and the fracture paths of the joints were summarized. The results revealed that the interface microstructure of the joints consisted of Ni(Cu)-W, Ni3P, CuNi, Cu(s,s), and Ag(s,s) phases. As the brazing temperature increased, Ni atoms gradually diffused from the NiP layer into the filler layer and substrate. At 900 °C, the NiP layer dissolved, and Cu atoms from the WCu alloy diffused into the solder layer, leading to a sharp growth in joint thickness. The shear tests indicated that the promotion of Cu content in the filler layer effectively alleviated the residual stress in the joints, resulting in higher joint strength. The maximum shear strength of 73.57 MPa was reached when the joints brazed at 840 °C. The hermeticity measurement results showed that the joints brazed at 900 °C for 10 min exhibited exceptional hermeticity, with a helium leakage rate of 2.51 × 10−11 Pa·m3/s. This work provided a reference for the connection of metal packaging materials with high temperature co-fired ceramics.

Cyclic Voltammetry and Photoluminescence Studies of Ag-doped ZnO Nanoparticles

Introduction: Herein, we prepared Zinc oxide (ZnO) and silver (Ag) doped ZnO nanoparticles (NPs) using a simple, fast, effective and economic coprecipitation method. The superior characteristics in the nanoscale range of ZnO encourage us to work on the ZnO NPs. Also, Ag has long been employed for its antibacterial qualities. X-ray diffraction (XRD) results indicate a hexagonal wurtzite structure of ZnO NPs and an additional peak corresponding to the metallic Ag phase in the Ag-ZnO sample. The EDAX elemental mapping confirms the uniform distribution of Ag in ZnO NPs. Photoluminescence (PL) spectroscopy investigates electronic structure and defects in NPs.ic co-precipitation method and study of Cyclic Voltammetry and Photoluminescence characteristics. Method: According to the PL study, the strong photoluminescence NBE observed at 393 nm, indicating the high crystalline quality of the material and broad blue-green emission at 467 nm and green-yellow emission at 560 nm were attributed to the Zn interstitial and oxygen vacancy defects present in ZnO NPs. Measurements from cyclic voltammetry (CV) demonstrate approximately symmetric peaks related to anodic and cathodic behaviours of the NPs based electrode. Result: For ZnO sample, the anodic peak was found at 0.49 V and cathodic at 0.29 V, whereas, for Ag-ZnO sample, the anodic peak was at 0.59 V, and the cathodic peak was present at 0.19 V, respectively. The separation between cathodic and anodic peaks enhanced with Ag-doping in ZnO, which could be associated with the variations in the transfer of electrons at the interface between the working electrode and the solution, confirming an increase in the reaction activity of Ag-ZnO NPs. Conclusion: The results indicate that Ag-doped ZnO NPs may be an efficient catalyst for waste water treatment and photocatalytic applications.

Influence of Electron Beam Treatment on Structure and Phase Composition of TiB2–Ag Coating Deposited by Electrical Explosion Spraying

Due to many factors, the electrical explosion spraying process is not stable, which directly causes unstable coating quality and structure. Electron beam treatment may be used to improve the surface and modified structure of coatings sprayed by electrical explosions. In this study, a new TiB2–Ag metal matrix composite coating was deposited by electrical explosion spraying and modified by electron beam treatment. The prepared coatings were characterized by surface macro- and microanalysis, XDR, cross-section SEM, and TEM. The composition of the spray-coating phase differs from sample to sample. The electron beam treatment normalized the phase composition. Ag TiB2 B2O became the main phase in the modified coating. Increasing the pulse energy density and duration leads to a reduction in the low-melting Ag phase and the formation of copper contact phases due to heating and melting of the copper substrate by excess electron beam energy. The coating structure consists of a silver matrix and TiB2 inclusions. The electron beam treatment did not affect the structure; however, the microstructure of the coating transformed into a cellular crystallization structure. The silver matrix nanostructure was transformed into a nanocrystalline structure with an average crystal size ranging from tens to hundreds of nanometers.

Loading of Silver (I) Ion in L-Cysteine-Functionalized Silica Gel Material for Aquatic Purification.

The L-cysteine-functionalized silica (SG-Cys-Na+) matrix was effectively loaded with silver (I) ions using the batch sorption technique. Optimal Ag(I) loading into SG-Cys-Na+ reached 98% at pHi = 6, 80 rpm, 1 mg L-1, and a temperature of 55 °C. The Langmuir isotherm was found to be suitable for Ag(I) binding onto SG-Cys-Na+ active sites, forming a homogeneous monolayer (R2 = 0.999), as confirmed by FTIR spectroscopy. XRD analysis indicated matrix stability and the absence of Ag2O and Ag(0) phases, observed from diffraction peaks. The pseudo-second-order model (R2 > 0.999) suggested chemisorption-controlled adsorption, involving chemical bonding between silver ions and SG-Cys-Na+ surface. Thermodynamic parameters were calculated, indicating higher initial concentrations leading to increased equilibrium constants, negative ΔG values, positive ΔS values, and negative ΔH. This study aimed to explore silver ion saturation on silica surfaces and the underlying association mechanisms. The capability to capture and load silver (I) ions onto functionalized silica gel materials holds promise for environmental and water purification applications.

Ag-Co3 O4 -CoOOH-Nanowires Tandem Catalyst for Efficient Electrocatalytic Conversion of Nitrate to Ammonia at Low Overpotential via Triple Reactions.

The electrocatalytic conversion of nitrate (NO3 ‾) to NH3 (NO3 RR) offers a promising alternative to the Haber-Bosch process. However, the overall kinetic rate of NO3 RR is plagued by the complex proton-assisted multiple-electron transfer process. Herein, Ag/Co3 O4 /CoOOH nanowires (i-Ag/Co3 O4 NWs) tandem catalyst is designed to optimize the kinetic rate of intermediate reaction for NO3 RR simultaneously. The authors proved that NO3 ‾ ions are reduced to NO2 ‾ preferentially on Ag phases and then NO2 ‾ to NO on Co3 O4 phases. The CoOOH phases catalyze NO reduction to NH3 via NH2 OH intermediate. This unique catalyst efficiently converts NO3 ‾ to NH3 through a triple reaction with a high Faradaic efficiency (FE) of 94.3% and a high NH3 yield rate of 253.7 μmol h-1 cm-2 in 1 M KOH and 0.1 M KNO3 solution at -0.25 V versus RHE. The kinetic studies demonstrate that converting NH2 OH into NH3 is the rate-determining step (RDS) with an energy barrier of 0.151 eV over i-Ag/Co3 O4 NWs. Further applying i-Ag/Co3 O4 NWs as the cathode material, a novel Zn-nitrate battery exhibits a power density of 2.56 mW cm-2 and an FE of 91.4% for NH3 production.

Vacuum Brazing of 18MAR300 Nickel Maraging Steel Joints Based on Additively Manufactured and Conventional Material Grades

Laser powder bed fusion (LPBF) processes offer the best possible design options for the production of highly complex components with unique functionalities. Although the development of additive manufacturing processes is progressing impressively and build rates have already been significantly increased, the economic production of high‐volume components is still particularly truncated. Comparatively expensive powders, machine‐hour rates, and a limited construction space demonstrate a high demand for joining LPBF components to conventionally manufactured parts. Vacuum brazing is an excellent technology for manufacturing and simultaneous heat treatment of such hybrid components. The aim of this study is to investigate the brazeability and the joint properties of ultrahigh‐strength nickel maraging steel 18MAR300 (1.2709, X3NiCoMoTi18‐9‐5) using BVAg‐30 (Ag68Cu27Pd5) as brazing filler metal. For this purpose, the effect of nickel‐plated surfaces on the wettability and the microstructure of the joint is studied for conv./conv.‐, LPBF/conv.‐, and LPBF/LPBF joints. Furthermore, the quasi‐static and quasi‐dynamic joint strength is evaluated. The results prove that nickel‐plated surfaces are vital to achieve a sufficient process control. The coating assures a deoxidized and sealed surface which favors the formation of NiCu(Fe,Pd,Ag) phases within the braze metal thus enhancing the joint strength. In addition, LPBF/LPBF joint features have significantly higher tensile strength than conv./conv. joints (825–627 MPa).

A Limit to Accelerated Free-Sintering: Nano-Phase Separation Interferes With Organic Debinding

Nano-phase separating Ni–12 at. pct Ag powders are processed via high-energy ball milling and brought into a supersaturated state with a reduction of the grain size to the nanocrystalline scale, a combination that is designed to encourage rapid densification by phase separation upon heating. This unstable powder is then characterized by dilatometry, in-situ x-ray diffraction, thermogravimetry and microstructure analysis for sintering cycles up to 940 °C. However, these powder compacts exhibit excessive pore evolution and significant macroscopic swelling caused by removal of the organic process additives. This competition of organic removal with densification is known in nanocrystalline metals, but the present study adds an additional dimension of phase separation, which shifts the dominant swelling mechanism as the formation of the second phase traps the volatilizing organics and hinders the debinding process. The creep swelling and overall loss in relative density is then dominated by the creep deformation of the second Ag phase. The interference between organic removal and low-temperature onset of consolidation represents a new challenge to efforts aimed at rapid free sintering and should guide the design of rapidly sintering alloys; specifically, the present work emphasizes the need to select alloys that have their sintering-accelerating phase separation temperature above the range where gases are evolved.

Facile synthesis of robust Ag/ZnO composites by sol–gel autocombustion and ion-impregnation for the photocatalytic degradation of sucrose

Metallic Ag nanoparticles decorated on ZnO photocatalysts were prepared by facile sol–gel autocombustion followed by ion-impregnation. Electron microscopy studies revealed the presence of impregnated Ag as nanoparticles on ZnO surfaces, which affected the microstructure of ZnO particles. XRD patterns of Ag/ZnO composites confirmed the metallic phase of Ag. No peak shift for ZnO phase peaks suggests that the impregnated Ag was barely incorporated into the ZnO lattice. Consequently, DRS spectra of Ag/ZnO composites revealed the same absorption edges and Eg for pure and Ag/ZnO. The photocatalytic activity of Ag/ZnO composites for sucrose degradation under UV light was 40% higher than that of pure ZnO. Metallic Ag nanoparticles on the ZnO surface suppressed the surface defects and the recombination of photoexcited electrons and holes. The highest activity with 100% degradation of 100 ppm sucrose (1200 µg of carbon) within 105 min was achieved using ZnO with 10% w/w Ag (10% Ag/ZnO). Ag L3-edge XANES spectra of fresh and spent Ag/ZnO catalysts confirmed the stability of metallic Ag after the usage. The Ag/ZnO catalyst could be used for 5 cycles without losing photocatalytic activity. The Ag/ZnO catalyst was utilized to degrade sugar-contaminated condensate from the sugar mill. 10% Ag/ZnO revealed the highest photocatalytic performance, capable of degrading 90% of sugar in the condensate within 90 min.

Preparation, characterization and densification studies of W-Ag nanocomposites produced by chemical route

W-Ag has applications in a wide range of cutting-edge fields, counting heat sinks and microwave absorbers for micro—electronic components, electric arc ends, and filaments for welding processes, electrical contacts, and durable electronic connections. Chemical methods provide a number of benefits, including improved purity, and controlled particle size. The present study focused on the fabrication of W-Ag nano composites using chemical synthesis. W-Ag nanocomposites with average size less than 50 nm were synthesized using Tungsten hexacarbonyl (W(CO)6, and silver acetate (CH3-COOAg) as metal precursors in the present study. The W-Ag composites were sintered using conventional sintering. X-ray diffraction studies of as-prepared powders showed amorphous W-phase and FCC Ag, while sintered W-Ag composites exhibited crystalline BCC W and FCC Ag phase. The effect of sintering temperature on relative density and mechanical properties of W-Ag sintered compacts was investigated. Relative density in excess of 97.6%, 98.2% and 98.8% was achieved for W-20.3 wt.% Ag, W-30.1 wt.% Ag and W-39.8 wt.% Ag composites on conventional sintering at 1000°C for 1 h. Vickers hardness of 364 ± 10 and 320 ± 8 Hv and 279 ± 6 were achieved for W-20.3 wt.% Ag, W-30.1 wt.% Ag and W-39.8 wt.% Ag composite compacts respectively. The hardness value of W-Ag composites decreased with an increase in Ag content. The combination of properties realized in this study renders the composites suitable for automotive and heat sink applications.

Tribological properties of NiCrAlYTa-Ag self-lubricating coatings at wide temperature range by detonation spraying

High-temperature self-lubricating materials are an appropriate choice to solve the problem of friction and wear for elevated temperature mechanical systems. In this study, NiCrAlYTa-Ag self-lubricating coatings used in a wide temperature range were prepared by the detonation gun spraying method. According to the findings, NiCrAlYTa-Ag coatings are composed of γ/γ', β-NiAl and Ag phases. The hardness and bonding strength of the coating decrease with the addition of Ag, and the coating with 20 % Ag has a high bonding strength of 43 MPa and a hardness of 303 Hv. The coating exhibited a friction coefficient of 0.35–0.47 and a wear rate of 4 × 10−5–6 × 10−5 mm3/N m From room temperature to 900 °C. At low temperatures, lubrication behavior was mainly attributed to the formation of Ag films. Excitingly, the AgTaO3 with good lubrication performance was created at high temperatures by a tribo-chemical reaction, which plays a synergistic lubrication role with Ta2O5, NiO, and Cr2O3.