Effect Of Ag Addition Research Articles

Effect of Ag Addition on ZnO for Photo-electrochemical Hydrogen Production

Effect of Ag Addition on ZnO for Photo-electrochemical Hydrogen Production

Effects of Ag addition on the structural and electrical properties of La0.67Sr0.33MnO3 ceramics

ABSTRACTLa0.67Sr0.33MnO3:mol-%Agx (LSMO:Agx, x = 0, 0.1, 0.2, 0.3 and 0.4) polycrystalline ceramics were prepared by chemical co-precipitation methods. All of the LSMO:Agx samples showed rhombohedral perovskite structure with a space group of . The diffraction peaks of metallic Ag did not appear in the XRD graph, due to the Ag substitution at A sites (La3+ or Sr2+ ions) and the evaporation loss of the element Ag in the process of high-temperature sintering, or the residual amount of Ag beyond the sensitivity of the XRD. With the increase of Ag addition, unit cell volume (V), metal−insulator transition temperature (Tp) and conductivity at Tp (ρTp) of the LSMO:Agx samples increased significantly. At the same time, the temperature coefficient of resistance (TCR%), temperature peak of the TCR% (Tk) and the figure of merit (Z) reached the optimal values of 3.3% K−1, 367 K and 0.049 at x = 0.3. Ag substitution at A sites (La3+ or Sr2+ ions) and gathering at grain boundaries (GBs) were proposed to explain the existence of Ag addition. All results suggested that the enhancement of electrical properties was due to silver-doping and it increased the bond angles of Mn−O−Mn (θMn−O−Mn) and the bond distance of Mn−O (dMn−O), improving Mn4+ concentration, grain sizes and GBs connectivity in LSMO:Agx ceramics.

Effect of Ag additions on the lengthening rate of Ω plates and formation of σ phase in Al-Cu-Mg alloys during thermal exposure

Effect of Ag additions on the mechanical properties and microstructures of the peak-aged Al-Cu-Mg alloys during prolonged thermal exposure at 150°C, was investigated by tensile testing, conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The results showed that after exposure for 500h, >85% of the peak strength remained. Microstructure observations indicated that increasing the Ag content from 0.14 to 0.57% promoted the precipitation of a fine and uniform Ω phase and suppressed the formation of the θ′ phase, leading to a notable improvement of the strength properties and thermal stability of the studied alloys. Quantitative TEM analysis showed that the coarsening of Ω phase was predominated by plate lengthening rather than thickening, while its lengthening rate was independent of various Ag additions during exposure at 150°C. In addition, an increase of Ag also facilitated the formation of a cubic σ phase, which was further supported by STEM results.

Effects of Ag Addition on Precipitation and Fatigue Crack Propagation Behavior of a Medium-Strength Al–Zn–Mg Alloy

Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a medium-strength aged Al–Zn–Mg alloy were investigated in the present work. The results show that a combination of enhanced tensile strength and improved fatigue crack propagation resistance in Al–Zn–Mg alloys is achieved with small addition of Ag. The enhanced strength is attributed to the high density of η′ precipitates within the grains and narrow precipitate free zones in the vicinity of grain boundaries. The main contribution to the improvement of fatigue crack propagation resistance comes from the coarser precipitates within the grains. When subjected to two-step aging, Ag-added alloy shows larger semi-coherent matrix precipitates. These relatively coarser precipitates increase the homogeneity of deformation and therefore improve the fatigue crack propagation resistance. In addition, microstructure analysis indicates that the size and distribution of inclusions as well as the grain structures of Al–Zn–Mg alloys are independent of Ag addition.

The Effect of Ag Addition on the Enhancement of the Thermal and Mechanical Properties of CuZrAl Bulk Metallic Glasses

In this study, the thermal and mechanical properties of Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6) bulk metallic glasses (BMGs) are investigated by using an X-ray diffractometer (XRD), a differential scanning calorimeter (DSC), differential thermal analysis (DTA), a Vickers hardness tester, a material test system (MTS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6) BMGs were made by arc-melting and an injection casting process. The results revealed that the glass transition temperature (Tg) and the crystallization temperature (Tx) of CuZrAl alloy decreased with the Ag addition. Hence, the supercooled liquid region and γ of Cu45Zr43Al7Ag5 alloy increased to 76 K and 0.42, respectively. The thermal stability and glass forming ability of CuZrAlAg BMG alloys were enhanced by the microalloyed Ag content. The room temperature compressive fracture strength and strain measured of Cu47Zr43Al7Ag3 were about 2200 MPa and 2.1%, respectively. The distribution of vein patterns and the formation of nanocrystalline phases on the fracture surface of Cu47Zr43Al7Ag3 alloy can be observed by SEM and TEM to be significant, indicating a typical ductile fracture behavior and an improved plasticity of alloys with the addition of microalloyed Ag from 0 to 6 atom %.

Magneto transport study of YBCO: Ag composites

We study the effect of Ag addition on the magnetoresistance and allied properties of YBCO. We find that the zero resistance temperature (TC0) shift is narrowed down by the addition of Ag as magnetic field (H) is increased from 0 to 13 T. The resistivity broadening of composites under magnetic field exhibits Arrhenius behavior due to thermally activated flux flow of vortices. The activation energy, determined from Arrhenius plot of resistivity, increases with the addition of Ag in YBCO and is found optimum for 15%Ag composite. The vortex glass transition temperature is found more in YBCO:Ag composites as compared to pristine YBCO. The zero temperature upper critical field Hc2(0) estimated by using Werthamer, Helfand and Hohenberg theory and Ginzburg Landau theory shows two fold enhancement by adding Ag in YBCO matrix. We find that the addition of Ag in YBCO leads to an enhancement in activation energy, an increases in Hc2(0) in addition to better grain connectivity.

An investigation into the effects of silver nanoparticles on natural microbial communities in two freshwater sediments

The expanding production and usage of commercial silver nanoparticles (AgNPs) will inevitably increase their environmental release, with sediments as a substantial sink. However, little knowledge is available about the potential impacts of AgNPs on freshwater sediment microbial communities, as well as the interactions between microbial communities and biogeochemical factors in AgNPs polluted sediment. To address these issues, two different sediments: a eutrophic freshwater sediment and an oligotrophic freshwater sediment, were exposed to 1 mg/g of either AgNO3, uncoated AgNPs (35-nm and 75-nm), or polyvinylpyrrolidone coated AgNPs (PVP-AgNPs) (30–50 nm) for 45 days. High-throughput sequencing of 16S ribosomal ribonucleic acid (16S rRNA) genes using the Illumina MiSeq platform was conducted to evaluate the effects of Ag addition on bacterial community composition. Moreover, sediment microbial biomass and activity were assessed by counting cultivable bacterial number and determining enzyme activities. During the 45-day exposure, compared with no amendment control, some treatments had resulted in significant changes and alterations of sediment biomass or bacterial enzyme activities shortly. While the microbial components at phylum level were rarely affected by AgNPs addition, and as confirmed by the statistical analysis with two-factor analysis of similarities (ANOSIM), there were no significant differences on bacterial community structure across the amended treatments. Redundancy analysis further demonstrated that chemical parameters acid-volatile sulfide (AVS) and simultaneously extracted silver (SE-Ag) in sediment significantly structured the overall bacterial community in sediments spiked with various silver species. In summary, these findings suggested that the ecotoxicity of AgNPs may be attenuated by the transformation under complex environmental conditions and the self-adaption of sediment microbial communities.

Investigation of the effect of Ag addition on the critical current density of the high-temperature superconductor Nd1.85Ce0.15CuO4

We have synthesized a Nd1.85Ce0.15CuO4 + Ag composite system with the aim of studying the effect of Ag addition in the electron-doped system Nd1.85Ce0.15CuO4 on its superconducting and magnetic properties. Measurements of magnetization using a vibration sample magnetometer indicate a systematic increase in diamagnetic shielding upon Ag addition. A subsequent analysis of the critical current density using the Bean model indicates a small but significant increase in intra-grain critical current density upon Ag addition. From the study of the dependence of electrical resistivity on the temperature and electrical current, an increase in inter-granular critical current has also been evidenced upon Ag addition. These results correlate well with the earlier reports of a similar improvement in the properties on the hole-doped ceramic superconductor/Ag composites. Possible reasons for the enhancement of JC have been described and discussed. Magnetic characterization by AC susceptibility using a SQUID magnetometer has been presented for a representative composition, which enabled delineation of the inter- and intra-granular transitions.

Structural studies of Nd1.85Ce0.15CuO4 + Ag superconducting system

We have studied for the first time the effect of Ag addition (0–15 wt%) to the superconducting system, Nd1.85Ce0.15CuO4, on its crystal structure and local structural features, using synchrotron X-ray diffraction (SXRD) and Raman spectroscopy, respectively. SXRD and subsequent Rietveld refinement studies on powders of Nd1.85Ce0.15CuO4 + Ag system indicate a small but significant change in lattice parameter upon Ag addition, showing evidence for possible incorporation of Ag to the extent of ∼1 wt%. Raman spectroscopic studies indicate that the parent structure of Nd1.85Ce0.15CuO4 remains unaffected with no major local structural changes on doping with silver. However, all Raman modes show minor phonon hardening upon Ag addition, which is consistent with the unit cell volume reduction as is observed in XRD. A systematic bleaching out of the apical oxygen defect mode was also observed with increased Ag addition. Polarized Raman measurements helped to identify the asymmetric nature of the B1g Raman mode. X-ray diffraction studies on pellets of Nd1.85Ce0.15CuO4 + Ag system further indicate a randomization of preferred orientation upon Ag addition. The superconductivity of the Nd1.85Ce0.15CuO4 + Ag system has been well characterized for all the compositions studied.

Structure and Magnetic Properties of (001) Oriented CoPt-Ag and CoPd-Ag Alloy Films

20-nm-thick (CoPt)100–xAgx and (CoPd)100–xAgx (001) films (x = 0–20) were grown on MgO(001) substrate at a temperature of 300uC by molecular beam epitaxy, and their crystal structure and magnetic properties were compared with those of FePt-Ag and FePd-Ag films [Y. Tokuoka et al.: J. Appl. Phys., 115, 17B716 (2014)] for the systematic study of the effect of Ag addition into transition metal – noble metal alloy films. For the CoPt-Ag, the addition of 5% Ag increased perpendicular magnetic anisotropy (PMA) and coercivity. However, for the CoPd-Ag, Ag addition enhanced neither the PMA nor the coercivity. Structural analysis of the CoPt-Ag and CoPd-Ag films revealed that Ag addition promoted L10 phase ordering for CoPt-Ag, while L10 ordering was not found in CoPd-Ag. Although there were some similarities in the effect of Ag addition between CoPt-Ag and FePt-Ag, such as increased PMA, coercivity, and L10 ordering, there were different trends in PMA and L10 ordering between CoPd-Ag and FePd-Ag, except that both films showed reduced coercivity with Ag addition. Ag segregation and L10 ordering are considered important factors to explain the variations of structure and magnetic properties with Ag addition.

Effect of Ag Addition on the Electrochemical Performance of Cu10Al in Artificial Saliva.

In this work we proposed to evaluate the corrosion resistance of four different alloys by electrochemical techniques, a binary alloy Cu10Al, and three ternary alloys Cu10Al-xAg (x = 5, 10, and 15 wt.%) to be used like biomaterials in dental application. Biomaterials proposed were tested in artificial saliva at 37°C for 48 h. In addition, pure metals Cu, Al, Ag, and Ti as reference materials were evaluated. In general the short time tests indicated that the Ag addition increases the corrosion resistance and reduces the extent of localized attack of the binary alloy. Moreover, tests for 48 hours showed that the Ag addition increases the stability of the passive layer, thereby reducing the corrosion rate of the binary alloy. SEM analysis showed that Cu10Al alloy was preferably corroded by grain boundaries, and the Ag addition modified the form of attack of the binary alloy. Cu-rich phases reacted with SCN− anions forming a film of CuSCN, and the Ag-rich phase is prone to react with SCN− anions forming AgSCN. Thus, binary and ternary alloys are susceptible to tarnish in the presence of thiocyanate ions.

Effects of Ag addition on FePt L1 ordering transition: A direct observation of ordering transition and Ag segregation in FePtAg alloy films

FePt and (FePt)91.2Ag8.8 alloy films were deposited by magnetron sputtering. The average coercivity of (FePt)91.2Ag8.8 films reaches 8.51 × 105 A/m, which is 0.63 × 105 A/m higher than that of the corresponding FePt films. Ag addition effectively promotes the FePt L10 ordering transition at a relatively low annealing temperature of 400 °C. The promotion mechanism was investigated by using in situ high-resolution transmission electron microscopy (HRTEM) and ex situ X-ray absorption fine structure (XAFS). The concurrence of ordering transition and Ag segregation in FePtAg alloy films was first observed by using in situ heating HRTEM. The time-resolved evolution reveals more details on the role of Ag addition in FePt low-temperature ordering. Ex situ XAFS results further confirm that Ag replaces Fe sites in the as-deposited films and segregates from FePt-Ag solid solution phase through annealing at elevated temperatures. The segregation of Ag atoms leaves vacancies in the grain. The vacancy formation is believed to accelerate the diffusion of Fe and Pt atoms, which is critical for the L10 ordering transition.

Effects of Ag addition on electrical and thermal properties of Mo–Cu composites

Abstract In this work, Mo–Cu composites with improved electrical and thermal conductivities were fabricated by sintering Mo–Cu–Ag powders obtained from a microwave-assisted aqueous solution method, as Ag is added as activator with contents ranging from 0.5 wt.% to 2.0 wt.%. Effects of Ag additive on microstructure, electrical conductivity (EC), thermal conductivity (TC) and coefficient of thermal expansion (CTE) were investigated. Results show that Mo–Cu composites with evenly distributed microstructure can be obtained when the Ag content is 1.5 wt.%. Additionally, Mo–Cu composites with an addition of 1.5 wt.% Ag have the optimal desired properties, 27.82 × 106 Sm−1 for EC and 185.4 W m−1 K−1 for TC, respectively. However, if the Ag addition becomes beyond 1.5 wt.%, it will result in decrease in electrical and thermal conductivities and increase in coefficient of thermal expansion.

Effects of Ag addition on properties and structure of Ge–Ga–Se–AgI chalcohalide glasses

An increasing amount of Ag metal was introduced in two GeSe2–Ga2Se3–AgI chalcohalide glasses with GeSe2/Ga2Se3 molar ratios of 1:1 and 2:1. Up to 25mol% Ag can be added in this GeSe2–Ga2Se3–AgI glass. The effects of Ag addition on some basic properties such as density, thermal stability, and optical band gap were investigated to have an overall understanding of GeSe2–Ga2Se3–AgI–Ag chalcohalide glasses. The modification of glass networks can be observed by Raman spectra and DSC measurements. Specifically, electrical conductivity was characterized by AC impedance spectra. The activation energy values of conductivity (Eσ) were obtained through Arrhenius linear fitting. The large amount of Ag in the systems led to high conductivity and low Eσ values. In general, several basic properties of the two series of novel glasses with different GeSe2/Ga2Se3 ratios were investigated in parallel and their potential as solid state conductive materials was evaluated.

Effect of Ag addition on microstructure and mechanical properties of Mg–14Gd–0.5Zr alloy

Microstructure and mechanical properties of the Mg–14Gd–0.5Zr (wt.%) alloy and Mg–14Gd–2Ag–0.5Zr (wt.%) alloy in homogenized, extruded and aged conditions have been investigated. Addition of 2% Ag enhances the tensile ultimate strength of the homogenized Mg–14Gd–0.5Zr alloy due to producing a larger strain field in magnesium crystal lattice. For the hot extruded alloys, the Ag-containing alloy shows a different type of texture, finer grains, higher hardness and a weak age-hardening response compared with the extruded Mg–14Gd–0.5Zr alloy, which are influenced by more Mg5Gd phases precipitating during extrusion in the Ag-containing alloy. The extruded Ag-containing alloy in peak-aged condition exhibit a lower yield strength due to a lower density of the prismatic β′ precipitate, while its better elongation is ascribed to the finer grain size and the basal precipitate.

In vitro investigation of Mg–Zn–Ca–Ag bulk metallic glasses for biomedical applications

For the purpose of developing biodegradable magnesium alloys with suitable properties for biomedical applications, Mg–Zn–Ca–Ag metallic glasses (MGs) were synthesized by copper-mold casting and melt spinning. The effects of Ag addition on the glass formation, thermal stability, microhardness, hydrogen evolution, corrosion resistance, and cytocompatibility of the Mg-based glassy alloys were studied in vitro. The corrosion resistance and the capability of suppressing the hydrogen evolution are enhanced for the Ag-containing alloys, in comparison to the Mg–Zn–Ca MG, though the incorporation of Ag decreases the glass-forming ability but influences insignificantly on microhardness. The higher cellular viability of the Ag-containing alloys than that of the Ag-free alloy was also revealed by direct cell-culture experiments. Thus, Mg–Zn–Ca–Ag MGs possess the potential to be employed as biodegradable materials.

A Study of Microstructure and Mechanical Properties of Eutectic In-Sn Solder Added Ag

In this study, effect of Ag addition on microstructure of In-48 wt%Sn solder was investigated to improve mechanical properties. The microstructure of In-Sn-Ag solder was formed by β phase, γ phase and two different intermetallic compounds (IMCs) which are Ag2In and AgIn2. Ag2In in In-Sn-Ag solder improves the mechanical strength but deteriorates the ductility. However, AgIn2 enhances the ductility but decreases the mechanical strength. To improve the both mechanical strength and ductility, control of the amount of Ag2In and AgIn2 was found to be important, and 3 wt% Ag addition was found to improve both mechanical strength and ductility of In-48 wt%Sn solder.

Effect of Trace Addition of Ag on the Precipitation Behavior of Al-Mg-Cu Alloy

Effect of Ag addition on the age-hardening response and precipitate microstructure of the Al-3.0Mg-1.0Cu (wt%) alloy has been investigated by micro Vickers hardness and transmission electron microscopy (TEM). The alloy compositions located in the (α+S+T) phase field of the Al-Mg-Cu phase diagram are known to be effective to harden in two stages separated by a distinct and often prolonged hardness plateau. The first stage of hardening occurs very rapidly (e.g. within 60 s at 443 K) and contributes to increase the hardness as much as 50% of the total age-hardening. Trace addition of Ag changes the age hardening response of the Al-3.0Mg-1.0Cu alloy dramatically. In the Ag-added alloy, the hardness change during the first stage of hardening is larger and the plateau stage is shortened as a result of the fast arrival at the second stage of hardness. The microstructure at the plateau stage of hardening for the Al-3.0Mg-1.0Cu alloy exhibits no clear evidence of any precipitates contributing to the first rapid hardening. On the other hand, lath-shaped S phase was observed at the peak hardness. In the Ag-added alloy, fine distributed precipitates were obtained from the beginning of age-hardening.

Effect of Ag addition on the magnetic and electrical properties of La0.67Ca0.33MnO3 films

La0.67Ca0.33MnO3:mol%Agx (LCMO:Agx, x=0, 0.04, 0.08, 0.10 and 0.20) films were prepared on the single crystalline (100)-orientated (LaAlO3)0.3–(SrAlTaO6)0.7 (LSAT) substrates by the pulsed laser deposition (PLD) method. With the increasing of Ag addition, the magnetoresistance (MR) of the LCMO:Agx films exhibits a significant decrease and the x=0 sample reach to the maximum value of MR ratio at 46.6% under 1T magnetic field, in addition, the metal–insulator transition temperature (Tp) improve 20–26K or 12–18K for the films at a zero or 1T fields, respectively. The results maybe due to the fact that Ag enter the host lattice, partially substitute for La3+/Ca2+ ion, and then increase the Mn4+/Mn3+ ratio, which lead to enhance the electrical properties in LCMO:Agx films.

Effects of Silver Addition on Critical Current Densities and Mechanical Properties in Bulk MgB2

The present study focuses on the effects of Ag addition on the critical current density (Jc) and the mechanical performance of disk‐shaped MgB2 bulk superconductors. MgB2 samples with varying Ag contents of 0, 2, 4, 6, 8, and 10 wt% were sintered at 775 °C for 3 h in Ar atmosphere. The Jc values were improved with Ag addition, in that the sample with 4 wt% Ag showed the highest Jc value of 295 kA cm−2 at 20 K and self‐field. The respective Jc values of the same sample were 430, 360, and 238 kA cm−2 in self‐field, 0.5 T, and 1 T at 7 K. These values are the highest so far reported in bulk MgB2 materials. Scanning electron microscopy showed that silver and silver oxide particles are embedded in the voids. As a result, the mechanical performance at room temperature was improved with Ag addition. We also confirmed the presence of nanometer‐sized AgMg3 particles, which may be responsible for high flux pinning and improved mechanical performances.