Palladium-silver Alloy Research Articles

Printed Thick Film Resistance Temperature Detector for Real-Time Tube Furnace Temperature Monitoring.

Accurately acquiring crucial data on tube furnaces and real-time temperature monitoring of different temperature zones is vital for material synthesis technology in production. However, it is difficult to achieve real-time monitoring of the temperature field of tube furnaces with existing technology. Here, we proposed a method to fabricate silver (Ag) resistance temperature detectors (RTDs) based on a blade-coating process directly on the surface of a quartz ring, which enables precise positioning and real-time temperature monitoring of tube furnaces within 100-600 °C range. The Ag RTDs exhibited outstanding electrical properties, featuring a temperature coefficient of resistance (TCR) of 2854 ppm/°C, an accuracy of 1.8% FS (full scale), and a resistance drift rate of 0.05%/h over 6 h at 600 °C. These features ensured accurate and stable temperature measurement at high temperatures. For demonstration purposes, an array comprising four Ag RTDs was installed in a tube furnace. The measured average temperature gradient in the central region of the tube furnace was 5.7 °C/mm. Furthermore, successful real-time monitoring of temperature during the alloy sintering process revealed approximately a 20-fold difference in resistivity for silver-palladium alloys sintered at various positions within the tubular furnace. The proposed strategy offers a promising approach for real-time temperature monitoring of tube furnaces.

Kinetics of Formic Acid Electrooxidation on Anodically Modified Silver–Palladium Alloys

Kinetics of Formic Acid Electrooxidation on Anodically Modified Silver–Palladium Alloys

Interactions between silver-palladium alloy and silicon carbide cladding layer in TRISO fuel: An in-depth analysis

High-temperature gas-cooled reactors (HTGRs) have garnered considerable interest due to their superior efficiency and inherent safety. This study systematically investigates the interaction between silver-palladium (Ag-Pd) alloy and silicon carbide (SiC) coating in tri-structural isotropic (TRISO) particles of HTGRs, focusing on the potential release of radioactive Ag-110 m through SiC cladding. Operating temperatures ranging from 800–1100 °C were examined to understand the mechanisms of Ag-Pd migration in SiC. Advanced techniques like transmission electron microscopy (TEM), focused ion beam (FIB) coupled with 3D visualization and scanning precession electron diffraction (SPED) integrated with machine learning were employed to identify two pathways of Pd-assisted Ag migration: (1) (Pd,Ag)2Si and (Pd,Ag)3Si acting as migration channels, and (2) Pd-rich phases increasing SiC disorder, enhancing Ag diffusion. Significantly, a carbon barrier formation above 1000 °C was observed, which inhibits Ag-Pd/SiC interaction. These findings offering new insights for predicting nuclear reactor lifespan and data support to optimize TRISO particles' structural design.

Revealing The Morphology of Ink and Aerosol Jet Printed Palladium-Silver Alloys Fabricated from Metal Organic Decomposition Inks.

Palladium films hold signicance due to their remarkable affinity for hydrogen diffusion, rendering them valauble for the seperation and purification of hydrogen in membrane reactors. However, palladium is expensive, and its films can become brittle after only a few cycles of hydrogen separation. Alloying with silver has been shown to overcome the problem of palladium embrittlement. Palladium-silver films have been produced via several methods but all have drawbacks, such as difficulties controlling the alloy composition. This study explores two promising jet printing methods: Inkjet and Aerosoljet. Both methods offer potential advantages such as direct patterning, which reduces waste, enables thin film production, and allows for the control of alloy composition. For the first time, palladium-silver alloys have been produced via inkjet printing using a palladium-silver metal organic decomposition (MOD) ink, which alloys at a temperature of 300°C with nitrogen. Similarly, this study also demonstrates a pioneering approach for Aerosol Jet printing, showing the potential of a novel room-temperature method, for the deposition of palladium-silver MOD inks. This low temperature approach is considered an important development as palladium-silver MOD inks are originally designed for deposition on heated substrates.

Limitations of reuse for silver-palladium alloys -Evaluating post-recasting heat treatment impact on corrosion resistance.

The aim of this study was to investigate the effect of repeated casting and heat treatment on the corrosion resistance of a commercial Ag-Pd-Cu-Au alloy as evaluated by electrochemical techniques. After repeated casting, the fifth cast of the Ag-Pd-Cu-Au alloy exhibited dramatic degradation of properties, although upon heat treatment, this corrosion resistance did improve. Despite the improvement by heat treatment, after five castings, this alloy may not have satisfactory hardness for clinical use. These results of this study demonstrate that, up to the fourth cast and heat treatment, the Ag-Pd-Cu-Au alloy has acceptable corrosion resistance and hardness.

A study of reaction between palladium, palladium silver alloy and silicon carbide ceramics at high temperature

The reactions between palladium (Pd), palladium-silver alloy (Pd-Ag) and silicon carbide (SiC) from 1200 °C to 1400 °C have been studied to investigate the impact of liquid phases on reaction products formation. The liquid phases were generated in Pd/SiC reactions at 1400 °C and in Pd-Ag/SiC reactions above 1300 °C. An increase in the amount of liquid associated with higher temperatures or Ag presence strongly affected the reaction mechanism and was responsible for the inhomogeneous dissolution of SiC grains and grain boundaries by Pd-rich phase at reaction front. This study helps understand Pd’s role on Ag release through SiC layer in Tri-structural isotropic (TRISO) fuel particles.

Investigation on the effect of recasting palladium-silver alloy by argon arc vacuum pressure casting process

Background/purposePalladium-silver (Pd–Ag) alloys are important as an alternative to gold-based alloys. The purpose of this study was to investigate the effect of an argon-arc vacuum pressure casting process on the recasting of the Pd–Ag alloy. Materials and methodsThe recasting Pd–Ag alloys were compared with conventional horizontal centrifugal (HC) casting to an argon (Ar)-arc vacuum pressure (Ar-arc/VP) casting. The first-generation castings were made from a Pd–Ag alloy purchased from a supplier. Next-generation castings were made from 50 wt% Pd–Ag alloy before casting and 50 wt% from previous castings. This sequence was repeated over three generations to form the 2nd, 3rd and 4th recasting ingots. The ingots were then measured for marginal accuracy, interfacial oxidation, hardness and phase identification. ResultsThe recasting success rate of recastibility reached 100%. Compared with the HC group, the Ar-arc/VP group had better edge precision, smaller oxide layer thickness and lower hardness. The comparison of X-ray diffraction intensity showed that the relative intensities of Pd and Ag in the first, second and third generations recasting of the Ar-arc/VP group were significantly higher than those of the HC group. Phase analysis showed that the trace elements of indium and tin contents in the Pd–Ag recasting ingots of the Ar-arc/VP group were higher than those of the HC group. ConclusionThe results showed that the casting process used for recasting affected the quality of the Pd–Ag alloy. Therefore, Ar-arc/VP casting process could improve the effect of Pd–Ag recasting and maintain the alloy properties in comparison with HC casting.

First principle study of the electronic and catalytic properties of palladium-silver (PdAg) alloys catalyst for direct liquid fuel cells

The alcohol fuel cell is a promising technology that will replace conventional energy production with higher energy conversion efficiency and less pollutant emission. However, the catalyst faces some challenges, and it requires modification. Among various modification methods, producing bimetallic alloys has delivered better performance than monometallic noble metal catalysts. Five catalyst models, Pd (111), Ag (111), Pd3Ag (111), PdAg (111), and PdAg3 (111), have been studied in this work in terms of structural, electronic, and adsorption molecules properties through density functional theory (DFT) studies. The structural and electronic properties of the modified catalyst model show the ligand and strain effect on the alloy with the addition of silver as second metal promotes the adsorption capability; however, the catalytic activity heavily depends on the alloy composition. Searching for active sites was also carried out by adsorption of selected atoms and molecules and used as a preliminary study to find possible active sites for alcohol electrochemical reaction at the anode in a direct liquid fuel cell (DLFC). The Pd3Ag (111) catalyst exhibits better adsorption ability on atomics, simple molecules, and alcohol/polyol molecules (methanol, ethanol, and glycerol). This work also carried out catalytic activities for ORR at the cathode. Pd3Ag (111) was found to be the most suitable for the ORR. The presence of the Ag atom showed theoretically a promising metal–metal combination for an excellent catalyst that might replace monometallic catalyst and produce a new tri-metallic catalyst in the future for the application in DLFCs, especially with glycerol. Even by replacing the 75% of Pd surface with Ag, the adsorption strength on the glycerol is remarkable, positively contributing to the oxidation reaction. The Ag metal is a suitable second metal candidate for the alloy to oxidize molecules with a longer carbon chain similar to or more than glycerol.

Wear of various restorative materials against 5Y-ZP zirconia

Statement of problemThe ceramic 5-mol% yttria-stabilized zirconia (5Y-ZP) has been developed for dental use in the esthetic zone with greater translucency than 3-mol% yttria-stabilized zirconia (3Y-ZP). However, studies on the wear behavior of 5Y-ZP zirconia against clinically relevant antagonist materials are lacking. PurposeThe purpose of this in vitro study was to investigate the wear behavior of 5Y-ZP zirconia against the antagonists 5Y-ZP zirconia, lithium disilicate, palladium alloy, and human enamel. Materials and methodsFlat specimens (n=8) were fabricated from 5Y-ZP zirconia, lithium disilicate, palladium alloy, and human central incisor enamel. A custom wear-simulating device with a sliding pin-on-plate configuration was used for a total of 120 000 wear cycles at 1.6-Hz frequency under a 49-N vertical load while submerged in distilled water at room temperature. The wear volume and maximum wear depth of flat specimens were evaluated with a 3D profilometer. Scanning electron microscopy was used to analyze the characteristics of the worn surfaces. ResultsAfter wear simulation, the 5Y-ZP zirconia and palladium-silver alloy specimens exhibited the least amount of material loss, both in terms of maximum wear depth and wear volume (0.079 ±0.042 μm, 0.001 ±0.001 mm3 and 0.637 ±0.307 μm, 0.001 ±0.000 mm3, respectively). This was followed by human enamel (6.034 ±1.086 μm, 0.009 ±0.001 mm3) and by lithium disilicate, which showed excessive material loss (38.342 ±2.569 μm, 0.213 ±0.024 mm3). Scanning electron microscopy revealed variations in wear mechanisms among the materials. ConclusionsThe 5Y-ZP zirconia and palladium-silver alloy exhibited the lowest wear, followed by human enamel and lithium disilicate. Slight grain dislodgement was displayed on worn 5Y-ZP surfaces, while more apparent grain dislodgement and wear grooves were found on lithium disilicate. Plastic deformation of worn palladium-silver alloy accumulated at the end of wear track. Cracks were detected in the human enamel specimens.

Revisiting Mott's model for the thermopower of PdxAg1−x alloys with support of density functional theory

Electronic properties of palladium-silver alloys have been studied for almost a century as a prototype of a transition-metal alloy with entangled $s$ and $d$ bands. We review the literature starting from Mott's model of 1935 and discuss from a quantitative point of view a series of common assumptions stemming from that seminal paper. We also show that spectral functions obtained by unfolding the band structures of a sample of supercells can be used for the ab initio computation of the thermopower of such systems within a Boltzmann transport equation approach.

Photo-thermo catalytic selective oxidation of cyclohexane by In-situ prepared nonstoichiometric Molybdenum oxide and Silver-palladium alloy composite

The highly selective oxidation of cyclohexane to cyclohexanone and cyclohexanol (KA oil) is one of the most challenging issues in the chemical industry. However, the difficulty in attaining high selectivity and high conversion rate in parallel for the existing catalysts limits its practical application. In this paper, a novel photo-thermo synergistic catalyst was reported for the aerobic oxidation of cyclohexane. The uniform blue MoO3-x nanowires with small diameter stabilized by polyvinyl pyrrolidone (PVP) were synthesized by a hydrothermal method, and a series of MoO3-x-AgPd composite materials of different proportions were prepared by an in-situ reduction process. The morphology, crystalline structure, surface chemical bonding, photoelectrochemical properties of MoO3-x-AgPd composites are thoroughly characterized. The MoO3-x-AgPd composites present significantly increased catalytic performance than MoO3-x nanowires in the photo-thermo synergistic catalytic oxidation of cyclohexane under dry air. The high conversion rate of 11.3% with the KA oil selectivity of 99.0% was achieved by the MoO3-x-Ag20Pd20 composites under photo-thermo catalytic process at 120 ℃, which is 1.5 times of that by MoO3-x nanowires. Under photo-thermo catalytic process, a high cyclohexane conversion rate similar to that of higher temperature thermal catalysis can be obtained at lower reaction temperature, and more cyclohexanol can be produced with a ketone to alcohol (K/A) ratio of 0.254. The significantly enhanced catalytic activity can be attributed to the effective charge transfer in the AgPd alloy nanoparticles, the optimized band gap structure, the suppressed charge recombination, and the promoted photo-thermo synergetic catalytic effect. This work provides a new reference scheme for the design and preparation of high-efficiency photo-thermo catalysts for the selective oxidation of cyclohexane.

Framework Materials for Full-Arch Implant-Supported Rehabilitations: A Systematic Review of Clinical Studies.

The purpose of this systematic review was to investigate the clinical outcomes of frameworks made of different materials in patients with implant-supported full-arch prostheses. A literature search was conducted on MEDLINE, Scopus and Cochrane Library, until the 1st of March 2021, with the following search terms: framework or substructure combined with “dental implants”. The outcomes evaluated were: implant and prosthesis survival, bone resorption, biological and technical complications. The Cochrane Handbook for Systematic Reviews of Interventions was employed to assess the risk of bias in randomized clinical trials. The Newcastle–Ottawa quality assessment scale was used for non-randomized studies. In total, 924 records were evaluated for title and abstract, and 11 studies were included in the review: 4 clinical randomized trials and 7 cohort studies. The framework materials investigated were: gold alloy, titanium, silver-palladium alloy, zirconia and polymers including acrylic resin and carbon-fiber-reinforced composites. High implant and prosthetic cumulative survival rates were recorded by all included studies. Various materials and different fabrication techniques are now available as alternatives to traditional cast metal frameworks, for full-arch implant-supported rehabilitations. Further long-term studies are needed to validate the use of these materials and clarify their specific clinical indications and manufacturing protocols to optimize their clinical outcomes.

Synergistic catalytic activity of palladium–silver alloy nanoparticle for anodic oxidation of ethanol in alkali

Palladium and palladium-silver alloy nano catalysts were synthesized from aqueous precursor at room temperature via a single vessel chemical reduction and co-reduction methods in absence of capping agent. XPS analysis confirms the presence of Pd and Ag in the catalyst matrix. Microscopic analyses reveal spherical morphology of the catalyst in the nanoscale dimension. The electro-analytical investigation of the catalyst loaded on carbon electrode shows that the Pd4Ag nano alloy catalyst demonstrates marked improvement in electro-catalytic efficiency among all prepared catalysts for ethanol oxidation in alkali. The Pd4Ag/C catalyst shows the mass normalized peak current density of 522 mA mg−1Pd in cyclic voltammetric (CV) study, which is 1.97 times greater than that of similarly synthesized Pd/C (264.2 mA mg−1Pd) catalyst. Chronoamperometric and impedance analyses further establish the superiority of Pd4Ag/C catalyst. To discover the plausible mechanism, the CV study is typically extended to the intermediates like sodium acetate which reveals that though Pd is better for catalytic oxidation of intermediate than the best catalyst but the optimal OH− adsorption on the surface of the metal, favours catalytic oxidation of ethanol more on Pd4Ag catalyst. The mechanistic path of the reaction is anticipated by evaluating the ex-situ FTIR and chromatographic studies which explain the promotion of the formation of carboxylate in comparison to carbonate by Ag.

Alloyed Palladium–Silver Nanowires Enabling Ultrastable Carbon Dioxide Reduction to Formate

Palladium can enable the electrochemical CO2 reduction to formate with nearly zero overpotential and good selectivity. However, it usually has very limited stability owing to CO poisoning from the side reaction intermediate. Herein, it is demonstrated that alloying palladium with silver is a viable strategy to significantly enhance the electrocatalytic stability. Palladium-silver alloy nanowires are prepared in aqueous solution with tunable chemical compositions, large aspect ratio, and roughened surfaces. Thanks to the unique synergy between palladium and silver, these nanowires exhibit outstanding electrocatalytic performances for selective formate production. Most remarkably, impressive long-term stability is measured even at < -0.4V versus reversible hydrogen electrode where people previously believed that formate cannot be stably formed on palladium. Such stability results from the enhanced CO tolerance and selective stabilization of key reaction intermediates on alloy nanowires as supported by detailed electrochemical characterizations and theoretical computations.

Due to intolerance of dental materials used for therapeutic treatment

Long-term clinical observations show that widely used dentures made of metals and their alloys are not indifferent, cause a number of diseases of the oral mucosa, and have social and medical consequences in the form of intolerance to dental prosthesis materials[1,2]. Currently, ceramic materials, plastics, stainless steels, cobalt-chromium, silver-palladium alloys, gold-based alloys, platinum, etc. are used for orthopedic treatment. these alloys include the following metals: iron, chromium, Nickel, titanium, manganese, silicon, molybdenum, cobalt, palladium, zinc, silver, gold, etc. Signs of intolerance may occur when placing dentures and filling materials in the oral cavity. Intolerance to prosthetic materials can be caused by different reasons that have different mechanisms of pathology development. Solving problems with intolerance to dental materials in each patient requires analysis together with a dentist, an immunologist, and an immunological laboratory [1-4].

Hierarchical defective palladium-silver alloy nanosheets for ethanol electrooxidation

Tuning the chemical composition and surface structure of electrodes is demonstrated as a feasible and effective strategy to tailor advanced catalysts for energy electrocatalysis. In this work, hierarchical palladium-silver alloy nanosheets (PdAg NS) with the thickness ~7 atoms and rich atomic defects are successfully prepared, using the carbon monoxide (CO) confinement approach. The optimized Pd7Ag3 NS/C exhibits 8.8 times higher catalytic peak current density and much better stability toward ethanol electrooxidation than Pd NS/C catalyst. The catalytic enhancement mechanism could be attributed to the synergetic effects among optimized electronic structure of Pd, novel architecture, and rich atomic defects.

Transmutations observed from pressure cycling palladium silver metals with deuterium gas

Hydrogen, deuterium, and helium gases were separately cycled through a Johnson-Matthey purifier containing coiled palladium silver alloy tubing: Pd25Ag (75 wt% Pd and 25 wt% Ag). During the cycling of D2 gas, evidence of anomalous heat production was observed. However, during the cycling of H2 and He, very little (H2) or no (He) unusual heat events were observed. After cycling the D2 gas through the coiled tubing for several months, Pd25Ag samples showed an increase in Cu and Fe compared with the amounts in unexposed Pd25Ag. Chromium, manganese, and zinc were detected in gas-cycled Pd25Ag samples, whereas they were not detected in unexposed Pd25Ag samples. In particular, Zn was present in the gas-cycled Pd25Ag material in larger quantities than either Cr or Mn. Although a small amount of Cu was present in the Pd25Ag coil before the D2 gas cycling, 7 times more was present after the cycling. Multiple material characterization techniques were used to obtain both pre-test and post-test elemental composition. The results indicate that novel post-test elements, primarily on the surface, were created by unknown nuclear mechanisms at low energy.

Gas Transmission Properties of Pd–Ag Membranes Coated with Modifying Layer

The paper proposes the manufacturing methods for modifying coatings for gas-diffusion membranes made of palladium-silver alloy comprising 23% Ag. Highly developed surface structures are synthesized to intensify chemisorption and dissociation and to accelerate the overall process of hydrogen transmission through the membrane. At a 0.6 MPa hydrogen overpressure and 100°C temperature, the density of the hydrogen flow through Pd/Ag23 wt.% membrane with the developed surface is 7 times higher than through the similar membrane without the modifying layer. The analysis of the proposed methods shows that the hydrogen density passing through the membranes with the modifying coating synthesized by a method with the included recrystallization stage, is 1.3 times higher than through the similar membranes synthesized in accordance with the standard procedures. The experiments show that the hydrogen transmission rate can be increased in the surface limited regime by creating a highly developed structure of the membrane surface.

Permeator Simulations for the EU-DEMO Fuel Cycle

Palladium alloy permeators are foreseen for the retrieval of hydrogen in the fusion fuel cycle of the European DEMO power plant. Driven by a pressure gradient, unburned fuel permeates through a thin-walled metallic membrane within the permeator while other gases cannot pass this barrier. With a theoretically unlimited selectivity with regard to nonhydrogenic species, a very high proportion of unburned fuel can be recovered in a continuous process from the exhaust gas and reused after a very short time. A potential candidate for the design of such a permeator consists of a tube (l = 500 mm, d = 10 mm) with a 125-μm-thick, self-supporting membrane made of a palladium-silver alloy all combined in the shape of a so-called finger-type design. A two-stage process then connects several of these permeators in parallel and in series to match the required throughput of DEMO during plasma operation at a given degree of separation. As the first design point in the scope of the current preconceptual design phase, a model was developed using the commercial software ASPEN Custom Modeler to estimate important parameters such as the tritium inventory and the scale of the permeator unit. How the hydrogen pressure profile is calculated over the length of a permeator using the Sieverts’ Law and the Finite Volume Method is thoroughly described. As a result, the integral performance of the combined permeators is presented as well as all important boundary conditions and assumptions that led to it. For the current DEMO baseline scenario, the total number of permeators of the abovementioned shape is found to be about 50.

Synergy between Plasmonic and Electrocatalytic Activation of Methanol Oxidation on Palladium–Silver Alloy Nanotubes

AbstractLocalized surface plasmon resonance (LSPR) excitation of noble metal nanoparticles has been shown to accelerate and drive photochemical reactions. Here, LSPR excitation is shown to enhance the electrocatalysis of a fuel‐cell‐relevant reaction. The electrocatalyst consists of PdxAg alloy nanotubes (NTs), which combine the catalytic activity of Pd toward the methanol oxidation reaction (MOR) and the visible‐light plasmonic response of Ag. The alloy electrocatalyst exhibits enhanced MOR activity under LSPR excitation with significantly higher current densities and a shift to more positive potentials. The modulation of MOR activity is ascribed primarily to hot holes generated by LSPR excitation of the PdxAg NTs.