Ag Coatings Research Articles

Biological adhesion and electrochemical behavior of Ag-ZrO2 bioceramic coatings for biomedical applications

Recently, surface tailoring of the metallic implant has taken considerable attention to enhance the longevity of implants. In this study, two different concentrations of silver (Ag) with zirconia (ZrO2) were deposited onto titanium (Ti) substrates using DC magnetron sputtering for both orthopedic and dental implants application. Thickness, surface morphology with elemental composition, functional group, and adhesion of the coatings were characterized by X–ray diffraction (XRD), stylus profilometer, field-emission scanning electron microscopy/energy-dispersive X-ray spectroscopy (FESEM/EDAX), Fourier transform infrared spectroscopy (FTIR) and nano-scratch indentor, respectively. Monoclinic phase of ZrO2 and cubic phase of Ag were confirmed with XRD. Nanostructured grains were obtained by FESEM analysis with the thickness of ∼300 nm, ∼700 nm and ∼800 nm for ZrO2, ZrO2–Ag and ZrO2–Ag(1) (Herein, ZrO2–Ag (low conc.) and ZrO2–Ag(1) (high conc.) coatings measured by profilometer. The in vitro bacterial adhesion was performed for as prepared ZrO2, ZrO2–Ag and ZrO2–Ag(1) coatings against E.coli, and Streptococcus sp. Adhesion study exhibits better performance for Ag containing ZrO2 rather than ZrO2 coated and uncoated Ti. Adhesion of platelet on the coated and uncoated Ti revealed that activated platelets are present in ZrO2–Ag(1) coated Ti. ZrO2 and ZrO2–Ag coated Ti showed enhanced fibroblast cell attachment and proliferation than uncoated Ti but not in ZrO2–Ag(1) coated Ti surface. Electrochemical impedance spectroscopy (EIS) results revealed superior corrosion resistance behavior for all the coatings than uncoated Ti in ABP electrolyte. The results stated those tailored Ti surfaces were certainly used to enhance the durability of the implant for biomedical applications.

Oxygen reduction reaction on thin-film Ag electrodes in alkaline solution

Thin Ag films with nominal thicknesses from 0.5 to 10 nm deposited on a glassy carbon (GC) substrate were prepared by electron beam evaporation and the oxygen reduction reaction (ORR) on the Ag/GC electrodes in alkaline solution was studied employing the rotating disk electrode (RDE) technique. Transmission electron microscopy (TEM) was used to examine the surface morphology of Ag films and it was found that the average particle size for the thinnest film was about 5.5 nm. The Ag particle size increased with increasing the film thickness and for 5 nm film the silver particles merged to a uniform coating. Electrochemical testing showed that the thin-film Ag electrodes are efficient catalyst for oxygen reduction and peroxide reduction reactions. The electron transfer number was calculated to be slightly lower than four for thinnest Ag film and it was 4 for all the other films. Tafel analysis showed similar slope value for all thin-film Ag electrodes revealing that the rate-determining step does not change with the Ag film thickness. The electro-oxidation of Ag films and Pb underpotential deposition experiments were also conducted. Finally, Ag coatings were electrochemically stripped from the GC electrode to determine the mass of Ag on the substrate surface, which was in good agreement with the calculated value. The 1 nm Ag film showed the best utilisation of silver, as mass and specific activities for ORR were the highest for that coating. Nanostructured Ag electrodes might be promising catalysts for alkaline membrane fuel cells.

Influence of annealing temperature on film morphology and tribological performance of TiSiN–Ag coating

TiSiN–Ag coatings were prepared by arc ion plating on Ti6Al4V at 450 °C. The as-deposited coatings were then annealed in a vacuum at 550, 650 and 750 °C for 30 min respectively to observe the Ag morphology and distribution in TiSiN coating. The microstructure evolution of the TiSiN–Ag coatings was characterized through scanning electron microscopy (SEM), revealing the segregation of Ag on the coating surface. The TiSiN–Ag coating annealed at 750 °C has denser structure, and more nanoscale to μm-size Ag outgrowths on the coating surface. The TiSiN–Ag coating annealed at 750 °C showed the highest hardness of 18.3 ± 1.5 GPa and maximum ratios H/E and H3/E*2, with excellent mechanical properties. For the annealed TiSiN–Ag coatings, the friction coefficient is relatively low, and the TiSiN–Ag coating annealed at 750 °C has the lowest wear rate.

Cr–Ag coatings: synthesis, microstructure and antimicrobial properties

ABSTRACTCr–Ag coatings for antimicrobial surface applications were fabricated by magnetron sputtering. The coating microstructure and mechanical properties were characterised using XPS, XRD, FESEM, TEM and nanoindentation measurement as a function of Ag content. The antimicrobial efficacy of these Cr–Ag coatings was evaluated against the pathogenic bacteria Escherichia coli and Staphylococcus aureus, revealing varied levels of bacterial killing. This study warrants further investigation into the antimicrobial mechanism of action of silver and future applications of Cr–Ag as antimicrobial coating for healthcare settings.

Silver effect on the tribological and antibacterial properties of a-C:Ag coatings

Abstract a-C:Ag coatings (1.2–23.4 at.% of Ag) were deposited using magnetron sputtering. Ag nanoparticles appear embedded in the carbon matrix or segregated to the column boundaries or surface. The silver doping has not promoted significant changes of the sp 2 /sp 3 ratio although a decrease of the hardness is observed (from 17 to 7 GPa). The tribological behavior did not show a clear dependence on the silver concentration in unlubricated or lubricated conditions (fetal bovinum serum) against alumina or UHMWPE balls. Ag nanoparticle dispersion enhanced the bactericide behavior as determined by the released Ag + ion in the fluid media. There is no clear effect of friction rubbing on the released silver indicating that diffusion and top segregation are prevalent mechanisms for its dissolution.

Study on Electroconductive Tribological Properties of Ag-Based Composite Coating

Electrical contacts are widely utilized in numerous engineering applications that require high reliability. However, fretting wear due to repeated contact may lead to increased electrical contact resistance that can cause failure of the electrical system. Herein, an Ag-based coating was prepared by an electroless co-deposition technique in order to improve the electroconductive properties under fretting conditions. By carefully controlling the deposition time, a relatively smooth and continuous Ag coating could be obtained. The structure of the coating was analyzed using X-ray diffraction, 3D confocal microscopy, and scanning electron microscopy techniques. The electroconductive tribological properties of the coating were assessed using a custom-built fretting tester. The Ag coating possessed good crystallinity and exhibited improved electroconductive properties compared with the Ni interlayer deposited on a steel substrate. The high temperature of the contact zone generated by friction contributed to the reduced electric resistance. Furthermore, incorporation of graphene as a dopant could improve the coating wear resistance, resulting in more reliable electroconductive properties in the fretting condition. The wear mechanism of the coating was also investigated through wear track analysis. The experimental results are expected to aid in understanding the electroconductive tribological properties of Ag coatings used in electrical contact applications.

Optimization of electrodeposited Co–Ag coatings microhardness using Taguchi and ANOVA methods

Co–Ag coatings have been prepared by potentiostatic deposition method from a mixed sulfate chloride bath on a Cu substrate. The cyclic voltammetry (CV) results confirm the reduction of Ag and Co ions. The SEM-EDX analyses prove the formation of Co–Ag coatings with compact and uniform surface. The XRD results reveal the presence of FCC-Ag and HCP-CoAg3 phases. The effects of the experimental parameters ([Co2+]/[Ag+] molar ratio (R), deposition potential (P) and deposition time (t)) on the electrodeposited Co–Ag coatings microhardness (HV) has been investigated using the Taguchi experimental design method based on an orthogonal array (OA) L27(313). Statistical signal-to-noise (S/N) results indicate that the optimal coatings parameters combination corresponding to the maximum of microhardness is P1R3t3 (P = 0.6 V, R = 15, t = 20 min). The coatings microhardness is influenced by R and P factors at a confidence level of 95%. According to the ANOVA results, R and P factors are the most influencing parameters with a contribution of 32.94% and 32.92% respectively, while the individual t factor is insignificant. The parameters interactions P × R and P × t are found to be significant with 17.77% and 9.18% respectively. At the optimum level, the microhardness is improved at 25% as compared to the initial conditions. A linear-interaction model for microhardness was developed and shows a high correlation between the experimental and the predicted microhardness values. The obtained results show that 97.8% of the total variations can be explained by the model with 95% confidence interval.

Synthesis and characterization of AgPd alloy coatings as beneficial catalysts for low temperature fuel cells application

The Ag, Pd and AgPd alloys of different morphologies and compositions were electrodeposited onto Au and glassy carbon (GC) disc electrodes from the solution containing 0.001 M PdCl2 + 0.04 M AgCl + 0.1 M HCl + 12 M LiCl under the conditions of non-stationary (RPM = 0, samples AgPd1 and AgPd2) and convective diffusion (RPM = 1000, sample AgPd3). Electrodeposited alloy layers were characterized by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) was investigated on all coatings in 0.1 M NaOH solution saturated with oxygen. The j-E curves for the ORR were recorded by two procedures: (1) samples were cycled with 5 mV s−1 from open circuit potential (OCP) to −0.8 V for Ag and AgPd alloys (or −0.6 V for pure Pd) and back; (2) samples were cycled with 5 mV s−1 from open circuit potential to 0.45 V (formation of Ag2O, in the case of Pd formation of PdO and PdO2), from 0.45 V to −0.60 V and back to the OCP. Significant catalytic activity for the Ag and AgPd alloys was detected after cycling electrodes in the potential region of Ag2O formation and reduction. Increase of the catalytic activity for AgPd alloys was, for the first time in the literature, ascribed to the presence of a certain amount of Ag2O which could not be completely reduced during the reverse sweep from 0.45 V to −0.6 V. Catalytic activity of AgPd alloys was found to be closely related to the amount of non-reduced Ag2O (most probably in the form of Ag-hydroxide). In the absence of such treatment, the catalytic activity for the ORR on electrodeposited Ag and AgPd alloy coatings was not detected.

Quasi layer by layer spray deposition of high-quality Ag coatings with excellent micro mechanical properties

In this paper, quasi layer by layer (quasi-LbL) spray deposition has been developed to produce pure and homogeneous metallic coatings on plastic surfaces. Comparing with Ag coatings by electroless deposition, the surfaces prepared by quasi-LbL show reflective and white characteristics that made of uniform nanoparticles of uneven size. By changing pH of spraying solution and spray passes, the surface morphology, roughness, composition, deposition weight and electrical properties of the Ag coatings by quasi-LbL were studies in details. The Ag coating with excellent electrical conductivity was face centered cubic (fcc) metallic state without any other phase, but with less oxides on the top surfaces than Ag coatings prepared by electroless plating. The deposition weight of Ag coatings would increase as the spray passes steps up, and Ag salts were the defining parameter for deposition weight even the spray atmosphere is air or N2. Nanoindentation tests were used to studies the micro mechanical properties. The modulus and the hardness of Ag coatings are 2.649 GPa and 0.118 GPa respectively, which are higher than those of electroless Ag coatings. The quasi-LbL method shows the possibility of producing high-quality metallic coatings and also be exploited to produce other kinds of metallic coatings, such as Ni and Cu.

TiSiN(Ag) films deposited by HiPIMS working in DOMS mode: Effect of Ag content on structure, mechanical properties and thermal stability

TiSiN(Ag) coatings with Ag contents ranging from 0 to 29 at.% were designed as promising materials to allow long term solid lubrication during dry machining operations. Here, we report the influence of Ag additions on the properties of TiSiN(Ag) films deposited by high power impulse magnetron sputtering- HiPIMS, working in deep oscillation magnetron sputtering mode – DOMS. Introduction of silver pellets on the target progressively increases the Ag concentration on the films, influencing the deposition rate, structure and morphology of the films. All the coatings display crystalline peaks assigned to a TiN fcc NaCl type structure. Ag additions to the reference TiSiN film, significantly broadens the TiN diffraction peaks and abruptly decreases the grain size of the TiN crystallites from 24 nm to 11–7 nm. Grain size was then found to be independent of the silver content on the films. Hardness and Young's modulus of the coatings decreased with increasing Ag additions mainly due to the increase of this soft phase on the microstructure. An increase in the peak power was observed when 6 at.% Ag was added which revealed a transition from a columnar to a very compact morphology, a decrease of the deposition rate and an increase of the lattice parameter for this coating. A reverse in the morphology is then perceived for the higher Ag concentration (29 at.%). Annealing treatment didn't present any significant changes in the structure/phase composition or mechanical properties of the coatings. Elemental maps and profiles allowed perceiving the formation of a very thin dual layer where a top Ag rich layer is formed due to the diffusion of silver from the Ag deficient TiSiN layer below.

Brazing of Martensitic Stainless Steel to Copper Using Electroplated Copper and Silver Coatings

Brazing of 3 mm thick sheets of low-carbon martensitic stainless steel and Cu-Cr-Zr-Ti alloy was attempted using electroplated coatings of Cu and Ag. Ni coating of 5 µm thick was provided on the MSS base metal to enhance the wettability. Brazing experiments were carried out at 985 °C for a holding of 15 min. Detailed microstructural studies, hardness, lap-shear, tensile, and pressure tests were carried out on the brazed joints. The reaction between the Cu and Ag coatings lead to the formation of in situ braze metal. The microstructure of the braze metal was found to consist of Cu-rich primary alpha (αP) and Ag-rich eutectic mixture (β + αE). In lap-shear tests, the brazed joints produced with an overlap of 9 and 6 mm were found to fail in copper base metal, while the joints produced with an overlap of 3 mm failed in the braze metal exhibiting a lap-shear strength of 147 MPa. In tensile tests, the butt brazed joints were found to fail in copper base metal as well with an average tensile strength of 213 MPa. The braze metal hardness was found to be higher than the hardness of the copper base metal. In pressure tests, the brazed panels were found to survive a pressure of 750 bar without undergoing any damage. These results show that electroplated coatings of Cu and Ag can be advantageously utilized for brazing of large, complex-shaped parts such as thrust chambers in space industry.

Frictional properties of silver over-coated on surface textured tantalum interlayer at elevated temperatures

Surface textured tantalum interlayer is designed to improve the friction properties of silver at elevated temperatures. In this study, the textured dimples were fabricated on the tantalum coated steel by pulse laser and the Ag coatings were deposited on the textured Ta interlayer by DC magnetron sputtering. The friction properties of silver films on the textured tantalum interlayer were tested by rubbing against a Si3N4 ball on a ball-on-disk tribometer from 25 °C to 600 °C. The results show that the friction performance of silver at 200 °C, 400 °C, 600 °C is improved by the textured tantalum interlayer while the role of texture is not significant for friction reduction at room temperature. It is not found a consistent trend that point to the ability of texturing to reduce friction at elevated temperatures. At the temperature above 400 °C, the role of lubricant storage for texture is more dominant. The silver films deposited on the textured tantalum interlayer with the dimple density of 6% shows relatively stable and low friction coefficient (μ = 0.2) at 600 °C. The combination of Ta2O5 and silver clusters on the worn surface of Ag/textured Ta composite coating contributes to the low friction coefficient at elevated temperatures.

Temperature-dependent structural transformation and friction behavior of nanocomposite VCN-(Ag) coatings

Nanocomposite VCN-Ag coatings with 10–11 at.% of Ag were obtained by pulsed DC magnetron co-sputtering of V and C (graphite) targets and simultaneous sputtering of Ag target and characterized as promising materials for wide temperature range tribological applications. The friction behavior of the Ag-doped coatings was studied during dynamic temperature ramp tribological tests in the range of 100–700 °C in comparison with their Ag-free counterparts. The sequence of phase transformations upon heating was determined using a combination of high-temperature in situ grazing incidence XRD and DSC/TGA analysis. In situ TEM heating to 450 °C was carried out to evaluate the thermal stability of VCN-Ag coatings. Raman spectroscopy, SEM, TEM, and EDS were employed to compare the coating structure inside and outside of wear tracks after high-temperature tribological tests. The temperature dependence of Ag shear moduli and the shear moduli of two experimentally observed vanadium oxides, V3O7 and V6O13, were obtained using DFT calculations to support and verify experimental observations. The obtained results indicated that the Ag-doped coatings exhibited a lower oxidation threshold. An observed significant drop in the friction coefficient of the VCN-Ag coatings in comparison with their Ag-free counterparts can be explained by (i) the surface self-oxidation initiated by Ag and the tribo-activated formation of AgVO3 phase in the temperature range of 250–350 °C and (ii) the formation of Ag0.4V2O5 phase and its tribo-activated melting above 650 °C.

Antibacterial and immunogenic behavior of silver coatings on additively manufactured porous titanium

Implant-associated infections (IAI) are often recurrent, expensive to treat, and associated with high rates of morbidity, if not mortality. We biofunctionalized the surface of additively manufactured volume-porous titanium implants using electrophoretic deposition (EPD) as a way to eliminate the peri-operative bacterial load and prevent IAI. Chitosan-based (Ch) coatings were incorporated with different concentrations of silver (Ag) nanoparticles or vancomycin. A full-scale in vitro and in vivo study was then performed to evaluate the antibacterial, immunogenic, and osteogenic activity of the developed implants. In vitro, Ch + vancomycin or Ch + Ag coatings completely eliminated, or reduced the number of planktonic and adherent Staphylococcus aureus by up to 4 orders of magnitude, respectively. In an in vivo tibia intramedullary implant model, Ch + Ag coatings caused no adverse immune or bone response under aseptic conditions. Following Staphylococcus aureus inoculation, Ch + vancomycin coatings reduced the implant infection rate as compared to chitosan-only coatings. Ch + Ag implants did not demonstrate antibacterial effects in vivo and even aggravated infection-mediated bone remodeling including increased osteoclast formation and inflammation-induced new bone formation. As an explanation for the poor antibacterial activity of Ch + Ag implants, it was found that antibacterial Ag concentrations were cytotoxic for neutrophils, and that non-toxic Ag concentrations diminished their phagocytic activity. This study shows the potential of EPD coating to biofunctionalize porous titanium implants with different antibacterial agents. Using this method, Ag-based coatings seem inferior to antibiotic coatings, as their adverse effects on the normal immune response could cancel the direct antibacterial effects of Ag nanoparticles. Statement of SignificanceImplant-associated infections (IAI) are a clinical, societal, and economical burden. Surface biofunctionalization approaches can render complex metal implants with strong local antibacterial action. The antibacterial effects of inorganic materials such as silver nanoparticles (Ag NPs) are often highlighted under very confined conditions in vitro. As a novelty, this study also reports the antibacterial, immunogenic, and osteogenic activity of Ag NP-coated additively-manufactured titanium in vivo. Importantly, it was found that the developed coatings could impair the normal function of neutrophils, the most important phagocytic cells protecting us from IAI. Not surprisingly, the Ag NP-based coatings were outperformed by an antibiotic-based coating. This emphasizes the importance of also targeting implant immune-modulatory functions in future coating strategies against IAI.

Aramid fibre-based wearable electrochemical capacitors with high energy density and mechanical properties through chemical synergistic combination of multi-coatings

Fibrous electrochemical capacitors (FECs) with outstanding wearability, mechanical properties and satisfactorily high energy density are greatly required for developing wearable smart devices and sustainable energy sources. Herein, new high performance FECs based on flexible but insulating aramid fibres (KFs) were developed through chemically grafting composite coatings of Ag nanoparticles, carbon nanotubes (CNTs) and capacitive polypyrrole (PPy), successively. Their structures and integrated performances were intensively studied. The PPy loading plays an important role on the capacitive properties of new KFs, and there is an optimum content of PPy for getting the best integrated performances. It is interesting to find that the capacitive property of KF/Ag/CNT/PPy is not the simple combination but much higher than those of KF/Ag/PPy and KF/CNT/PPy, proving that there is a synergistic effect between Ag and CNT coatings. This synergistic effect endows KF/Ag/CNT/PPy fibres with high specific capacitance and large energy density. For example, the specific capacitance and energy density of the novel aramid fibre capacitor with the optimum content of PPy (KF/Ag/CNT/PPy0.2) are as high as 84.3 F cm−3 (or 24.8 F g−1) and 7.49 mW h cm−3 (or 2.21 mW h g−1), respectively. In addition, KF/Ag/CNT/PPy0.2 exhibits enhanced cyclability and wearability (its capacitance retains 94.0% after 1000 cycles and 93.2% after bending for 500 times) because of the special design of strong interactions between different components. Note that KF/Ag/CNT/PPy0.2 also has high tensile strength, modulus and break extension. These attractive integrated performances demonstrate that KF/Ag/CNT/PPy0.2 makes obvious breakthrough on developing FECs based on polymer fibres, and thus have great prospect in fabricating wearable electronic devices and sustainable energy sources.

Electrochemical Promotion of Propylene Combustion on Ag-Based Nanostructured Catalysts

Catalytic and electrocatalytic measurements have been carried out in a solid oxide cell for propylene combustion using continuous Ag catalytic films and Ag nanoparticles dispersed on a mixed ionic electronic conductor film deposited on yttria-stabilized zirconia. Similar EPOC behaviors were observed for both samples, indicating that dispersed Ag nanoparticles in LSCF can be electropromoted in a reversible and non-Faradaic manner under lean-burn conditions. Key words: Electrochemical Promotion of Catalysis (EPOC); Propylene Combustion; Ag Catalytic films; dispersed Ag nanoparticles. Introduction: Catalytic combustion as a process used for removal of hydrocarbons from automotive gas exhausts or for energy production has been widely implemented on supported PGM (Platinum Group Metals) based catalysts. Since PGMs are very costly and rare, there is a strong need for an equally effective and less expensive catalyst. The electrochemical promotion of catalysis (EPOC), is a promising concept to in-operando boost catalytic processes in a reversible and controlled manner. The aim of this study was to develop Ag-based electrochemical catalysts for low temperature propylene deep oxidation. The magnitude of the electrochemical promotion has been investigated on continuous screen-printed Ag films as well as on Ag nanoparticles dispersed into the porosity of LSFC (La0.8Sr0.2Co0.2Fe0.8O3), a mixed ionic electronic conductor (MIEC). Experimental: Nanostructured electrochemical catalysts were prepared by screen-printing and by wet impregnation method. Catalytic and electrocatalytic tests have been carried out in a specific quartz reactor1 which operated under continuous flowing conditions at atmospheric pressure. The catalytic activity was monitored in a temperature range of 100 to 400 oC under lean-burn conditions, as encountered in Diesel exhausts. The most active Ag films were also evaluated under closed circuit conditions in order to measure the impact of polarization between the silver working electrode and a Au reference electrode. Both electrodes were exposed to the same atmosphere in a single chamber configuration. Results and discussion: Figure 1 shows typical catalytic activity measurements under current application for a Ag/YSZ sample (a) and a Ag/LSCF/YSZ sample (b) under lean-burn conditions, at 300 oC. The OCV propylene conversion is twice on the dispersed Ag nanoparticles despite a two orders of magnitude lower Ag loading. Furthermore, similar EPOC behaviors were observed for both samples, indicating that dispersed Ag nanoparticles in LSCF can be electropromoted in a reversible and non-Faradaic manner. The predominant impact of current applications is to modify the reactivity of oxygen present on the Ag surface. Conclusions: This study reports, for the first time, that the catalytic activity for propylene combustion of Ag coatings and Ag nanoparticles supported on LSCF both deposited onto YSZ can be tailored by current applications in a non-Faradaic manner. This study also demonstrates that EPOC can enhance catalytic properties of Ag nanoparticles dispersed in a MIEC layer for the abatement of propylene in air. Acknowledgments: This study was performed in the “EPOX” project, funded by the French National Research Agency (ANR), ANR-2015-CE07-0026.

Tip-Functionalized Au@Ag Nanorods as Ultrabright Surface-Enhanced Raman Scattering Probes for Bioimaging in Off-Resonance Mode

Surface-enhanced Raman scattering (SERS) performance of Au nanorods (AuNRs) can be enhanced by the tip adsorption of Raman molecules (RMs) through anisotropic polymer stabilization or through the embedding of RMs between AuNR cores and Ag shells of AuNR@RM@Ag composite particles. We propose a new strategy to design ultrabright SERS probes composed of high-aspect-ratio AuNRs with anisotropic Ag coatings, with preferred adsorption of RMs to open AuNR tips. Specifically, for 4-nitrobenzenethiol (NBT) concentrations above a threshold value c > ctr, the fabricated Au@NBT@Ag particles had NBT-functionalized open Au tips, as well as anisotropic Ag shells grown on the AuNR sides. The SERS response of these probes with an optimal Ag shell was highest in the off-resonance mode, when the excitation wavelength was far from the plasmon resonance of the Au@NBT@Ag composites. Growing the Ag shell further to completely cover the AuNRs decreased the SERS enhancement. For biocompatibility and stability, the probes were add...

Optimization of Electrically Conductive Adhesive Bonds in Photovoltaic Modules

Gluing ribbons to silicon solar cells by using electrically conductive adhesives (ECAs) is an alternative interconnection technology for module integration to the state-of-the-art soldering process. We reveal cost reduction potentials by analyzing the influence of volume and contact resistivity, as well as the bond design of ECAs on the fill factor of photovoltaic modules. Solar cells with structured busbars are considered in the analysis. The volume resistivity is controlled by the cure temperature. We contact individual cells at different curing conditions and measure their fill factors. A volume resistivity of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> Ω · cm does not cause a significant fill factor reduction compared with an ECA with around 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> Ω · cm. The contact resistivity is varied by using different ribbon coatings. Ag and Sn coatings achieve almost identical fill factors. A bare Cu surface reduces the fill factor. We lower the consumed ECA from 40 to 3 mg/cell by modifying the bond design. A design with 16 mg/cell achieves similar fill factors as with 40 mg/cell. A finite-element model is developed to study the combined influence of electrical properties and the bond design. We propose an optimized contact design for high fill factors and reduced material consumption.

Dual-doped(Si-Ag) graphite-like carbon coatings with ultra-low friction and high antibacterial activity prepared by magnetron sputtering deposition

Silicon(Si) and silver (Ag) co-doped amorphous carbon (a-C:H:Si:Ag) coatings were prepared by magnetron sputtering deposition. The results of Raman analyses revealed that the coating was dominated by sp2 carbon bonds and had graphite like structure. The a-C:H:Si:Ag coating exhibited a very high elastic recovery rate of 82%. Tribological tests in saline solution (NaCl, 0.9 wt%) showed that the average friction coefficient and the wear rate of the coating were as low as 0.016 and 1.2 × 10−8 mm3/(N·m), respectively. The dual doped coating exhibited a high antibacterial rate over 99% against Escherichia coli though containing a small content of Ag. It also was found that the silver ions release from the coating was extremely slow, and the newly developed (a-C:H:Si:Ag) coating would be a promising long term antibacterial materials.

Deformation and Fracture of Micron‐Sized Metal‐Coated Polymer Spheres: An In Situ Study

In situ imaging and analysis of the mechanical behavior of micron‐sized metal‐coated polymer particles under compression is reported. A nanoindentation set‐up mounted in a scanning electron microscope is used to observe the deformation and fracture of 10 μm polymer spheres with Ni, Ni/Au, Au, and Ag coatings. The spheres fracture in one of two metallization‐dependent modes, brittle, and ductile, depending only on the presence of a nickel layer. The metal coating always fractures parallel to the direction of compression. The mechanical properties up to the point of coating fracture are rate‐dependent due to the viscoelastic polymer core. Metal‐coated polymer spheres are an important composite material in electronics packaging, and this study demonstrates a novel method of evaluating the mechanical properties of particles to tailor them for electronic materials.