AgSnO2 Contact Material Research Articles

Preparation and arc erosion mechanism of Ni skeleton reinforced Ag-based contact materials with CuO-coated SnO2

The Ag-SnO2 contact material is widely regarded as the most promising environmental friendly electrical contact material. However, during the make and break operations, SnO2 particles rising to the surface can cause increased contact resistance and temperature rise, which affects the service life of the contact material. In this study, a three-dimensional (3D) Ni skeleton reinforced Ag-based contact material with CuO-coated SnO2 are successfully fabricated via powder metallurgy technology. The basic physical properties of the novel contact material were tested and the microstructures and arc erosion morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The research demonstrated that the hardness and electrical conductivity of the novel contact material are 128.9 HV and 46 %IACS, respectively. It can be observed that the SnO2-rich phase is uniformly distributed in the Ag matrix without significant upward after arc erosion, which indicates that the SnO2@CuO core-shell structure effectively enhances the wettability between Ag and SnO2. Meanwhile, the study revealed that the Ni phase uniformly distributed at the interface of the Ag phase during the arc erosion process, indicating that the 3D Ni skeleton structure effectively impedes the expansion of the Ag molten pool and improves the anti-arc erosion performance.

Nacre-mimetic alternating architecture of Ag[sbnd]SnO2 contact: Highly-efficient synergistic enhancement of in-situ self-repairing erosion resistance and naturally evolving impact resistance

Synergistically enhancing the erosion and impact resistance of contacts poses a significant challenge for cutting-edge electrical equipment. Fortunately, mollusk shells in nature have evolved effective strategies to construct microstructures with superior erosion and impact resistance. Inspired by the structure of nacre, AgSnO2 contact material with hierarchical architectures has been designed and fabricated. The mechanistic link between microstructural evolution and dynamic erosion is studied through experiments combined with Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) simulations. Results show that the reconstructed SnO2 skeleton endowed with a highly continuous and anisotropic ‘flowering'-like structure forms a continuous interpenetrating network with Ag, optimizing the conductive pathways on the molten pool surface. Additionally, the Ag-rich regions in the deeper layers on both sides of the molten pool offers a stable ‘nutrient-supply’ for the continuous ‘flowering’ reconstruction of the skeleton, exhibiting excellent in-situ self-repairing erosion resistance. Benefiting from this synergistic strategy, this skeleton is reconstructed based on its natural structure, which further disperses the stress and deformation concentration while inhibiting interfacial debonding, thereby reducing the formation of cracks and significantly enhancing the impact resistance. This work is expected to breakthrough erosion and impact resistance in extreme condition electrical contact materials through biomimetic microstructure design.

Effect of In2O3 Additive Size on the Mechanical Behavior of Densified Ag-SnO2 Contact Materials

Effect of In2O3 Additive Size on the Mechanical Behavior of Densified Ag-SnO2 Contact Materials

Arc erosion behaviors of the densified Ag-SnO2 contact materials containing sub-micron and nano In2O3 additives

The effects of In2O3 additive size on the physical properties and arc erosion behaviors of the densified Ag-SnO2 materials were investigated. Arc resistance mechanism was analyzed based on the microscopic morphology characterization. Results revealed that the physical properties of the Ag-SnO2(In2O3) materials were significantly improved after densification. Relative density and electrical conductivity of the materials reached above 99.5% and 71%IACS, respectively. The densified Ag-SnO2 material containing sub-micron In2O3 showed the low and stable break arc energy. The mass loss of the cathode was dramatically decreased by 65.4%. Importantly, the generation of pores and micro-cracks on the surface of electrodes were significantly restrained and the contact resistance became more stable. By comparison, the nano In2O3 additive less than 100 nm effectively suppressed not only the splash of molten Ag on the surface of cathode but also the aggregation of SnO2 particles on anode. The arc erosion products were obviously decreased, resulting in an enhancement of arc-erosion resistance of Ag-SnO2(nano In2O3) materials. Compared with that without additive, the mass loss of the Ag-SnO2 material which contains nano In2O3 obviously decreased from 2.3 to 1.4 mg. The optimal mass fraction of nano In2O3 in the Ag-SnO2 contact materials was 1 wt%.

Designing sandwich-structured Ag–SnO2 contact materials: Overcoming the trade-off between erosion resistance and mechanical properties

Designing a second-phase enhancement system for SnO2 microstructures always plays a major role in improving the electrical contact performance of Ag–SnO2 contacts. This study fabricated sandwich-structure Ag–SnO2 contacts to overcome the trade-off between the erosion resistance and mechanical properties of Ag–SnO2 contacts via electrospinning with spark-plasma sintering; subsequently, the influence of SnO2 interlayers on the arc-erosion behaviour and mechanical characteristics of the contacts was investigated. The sandwich structure facilitated a reduction in the hill-and-valley morphology of the contact surface during repetitive erosion; fibrous SnO2 restricted the fluid evaporation of Ag, while SnO2 interlayers dispersed molten bridges, thereby improving the erosion resistance of the system. In parallel, 3D models of the sandwich-structured Ag–SnO2 contacts were reconstructed to investigate the evolution of their mechanical characteristics. Experimental and simulation indicated that the dispersion of stress concentration and reduction in surface deformation induced by the interface effect were the mechanical enhancement mechanisms, while the improvement of impact and wear resistances was attributed to the intensified support provided by the SnO2 interlayers on the matrix surface. Moreover, the synergistic interactions between Ag and SnO2 interlayers mitigated crack initiation and fracture propagation, thereby improving the fracture resistance of the contact matrix. These insights led to a feasible strategy for designing the microstructures of Ag-based contact materials.

Effect of short-time hot repressing on a Ag-SnO2 contact material containing CuO additive

It remains difficult to achieve high-density metal matrix composites by traditional powder metallurgy. In this study, short-time hot repressing was proposed to densify a Ag-SnO2 contact material prepared by powder metallurgy. The effect of the vacuum repressing temperature on the Ag-SnO2 material containing CuO additive was systematically investigated under a constant pressure of 200 MPa. The results showed that the relative density of the material repressed at 800 °C for 10 min can be increased to as high as 99.75%. The microstructure of the Ag-SnO2(CuO) material was obviously refined and homogenized by short-time hot repressing. The dispersive distribution of the SnO2 particles in the Ag matrix was induced, resulting in the elimination of particle aggregation. It is worth noting that almost all the CuO additive was decomposed into Cu2O after hot repressing, which was beneficial for improving the electrical contact properties. Furthermore, the arc energy of the repressed material significantly decreased with increasing repressing temperature, which can be attributed to the high density and uniform microstructure. During arc erosion, the mass loss of the Ag-SnO2(CuO) materials repressed at 800 °C was smallest, and the formation of pores and cracks was inhibited. However, the relative density of the material showed a tendency to decrease when the repressing temperature reached 850 °C.

Effects of the CuO additive nanoparticles on the internal strain homogenization and microstructure evolution in Ag-SnO2 composites

Stress concentration caused by reinforcements has very unfavorable effects on the metal matrix composites, which will inevitably induce localized strains and crack initiation. In this paper, an effective approach is presented to relieve stress concentrations near the reinforcements in metallic composites. The Ag-SnO2 contact materials with CuO additive are prepared by electroless plating combined with powder metallurgy method. The CuO nanoparticles in-situ formed on the SnO2 reinforcements are adopted to relieve local stress concentrations near the Ag/SnO2 interfaces and promote strain homogenization. The mechanical properties, deformation characteristics and microstructure evolution of the Ag-SnO2 composites without and with CuO additive are systematically studied by experiments and numerical simulations. The results show that the CuO nanoparticles formed on the surfaces of the SnO2 reinforcements dramatically improve the mechanical properties of the Ag-SnO2 composites, particularly the plasticity at a higher loading rate. The ultimate strength of the Ag-SnO2(CuO) tensile specimens is increased from 104 to 127 MPa, and the uniform elongation is increased by 83% compared with that without CuO. It is demonstrated that the dislocation tangle around the CuO nanoparticles effectively relieves the adverse effect of the stress concentration near the SnO2 and results in the strain homogenization in the Ag matrix. Furthermore, the damage evolution of the Ag-SnO2 composites without and with CuO nanoparticles is investigated by the Gurson-Tvergaard-Needleman (GTN) models under uniaxial tension. The error range of the simulated stress-strain curves is lower than 4%. The nucleation and growth of voids at the interfaces of the Ag-SnO2 composites are numerically simulated and discussed. This study provides a fundamental basis for developing novel high-performance metal matrix composites.

Properties of AgSnO2 Contact Materials Doped with Different Concentrations of Cr.

As an important component carrying the core function and service life of switching appliances, the selection and improvement of electrical contact materials is of great significance. AgSnO2, which is non-toxic, environmentally friendly and has excellent performance, has become the most promising contact material to replace AgCdO. However, it has deficiencies in machinability and electrical conductivity. The property of AgSnO2 contact material was improved by doping element Cr. The relationship between the mechanical and electrical properties of AgSnO2 contact materials and doping concentrations were investigated and analyzed by simulation and experiment. Based on the first principle, the elastic constants of supercell models Sn1−xCrxO2 (x = 0, 0.083, 0.125, 0.167, 0.25) were calculated. The results show that the material with a doping ratio of 25% is least prone to warp and crack, and the material with a doping ratio of 12.5% has the best toughness and ductility and the lowest hardness, which leads to molding and is subsequently easier to process. The Cr-doped AgSnO2 contacts with different doping proportions were prepared by the sol–gel and powder metallurgy method. Additionally, their physical performance and electrical contact properties were measured in experiments. The results show that the doped SnO2 powders prepared by the sol–gel method realize integration doping, which is consistent with the crystal model constructed in the simulation calculation. Sn0.875Cr0.125O2 has lower hardness, which is beneficial to process and form. Doping helps to stabilize the arc root, inhibit the ablation of contact by arc, reduces arc duration and arc energy, improves the resistance to arc erosion of AgSnO2 contact material, and makes electrical contact performance more stable. The contact material with a doping concentration of 16.7% has the best arc erosion resistance.

Study on the Improvement of the Performance of AgSnO2 Contact Material for Low‐Voltage Electrical Apparatus with Additive Particle Size

In this paper, the relationship between additive particle size and properties of AgSnO2 contact materials was studied. La2O3 and Bi2O3 were selected as additives for contact materials. AgSnO2 contact materials were successfully prepared by powder metallurgy, the wettability and electrical contact properties of AgSnO2 contact materials with five particle sizes of additives were investigated. The results show that the wettability and electrical contact properties of the two contact materials are better when the particle size of additives is 500 nm and 1000 nm respectively. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Numerical investigation on interface enhancement mechanism of Ag-SnO2 contact materials with Cu additive

Numerical investigation on interface enhancement mechanism of Ag-SnO2 contact materials with Cu additive

Improved arc erosion resistance of Ag/SnO2 composites fabricated by Ag melt-infiltration in the SnO2 skeleton

The typical Ag-SnO2 contact materials in which SnO2 dispersing in the Ag matrix suffer a poor arc erosion resistance because the individual SnO2 particles segregate and form a SnO2-rich layer under repeated arcing. Here, we introduce an architectured Ag/SnO2 composites in which individual SnO2 particles are bonding into a skeleton, fabricated by a novel method: (i) creating a porous SnO2 matrix by sintering SnO2 powders with NaCl space-holders, (ii) then infiltrated by Ag melt in the air. 95% relative density is achieved for the Ag/SnO2 composites. The microstructure evolution during the sintering and infiltration are investigated. 10,000 times make-and-break operations are conducted to evaluate the arc erosion resistance of the architectured composite, the temperature rise of the prepared Ag-60vol.%SnO2 composite decreases ∼90% compared with the particle dispersed composites. The microstructure of the arc-erased layer is analyzed and reveals that the SnO2 skeleton effectively suppresses the formation of the SnO2-rich layer, providing good arc erosion resistance and the potential for long lifetime contacts.

First-Principles Calculation of Conductivity of Ce-C Codoped SnO2 Contacts

The contact is the core element of the vacuum interrupter of the mechanical DC circuit breaker. The electrical conductivity and welding resistance of the material directly affect its stability and reliability. AgSnO2 contact material has low resistivity, welding resistance, and so on. This material occupies an important position of the circuit breaker contact material. This research is based on the first-principles analysis method of density functional theory. The article calculated the lattice constant, enthalpy change, energy band, electronic density of state, charge density distribution, population, and conductivity of Ce, C single-doped, and Ce-C codoped SnO2 systems. The results show that Ce, C single doping, and Ce-C codoping all increase the cell volume and lattice constant. When the elements are codoped, the enthalpy change is the largest, and the thermal stability is the best. It has the smallest bandgap, the most impurity energy levels, and the least energy required for electronic transitions. The 4f orbital electrons of the Ce atom and the 2p orbital electrons of C are the sources of impurity energy near the Fermi level. When the elements are codoped, more impurity energy levels are generated at the bottom of the conduction band and the top of the valence band. Its bandgap is reduced so conductivity is improved. From the charge density and population analysis, the number of free electrons of Ce atoms and C atoms is redistributed after codoping. It forms a Ce-C covalent bond to further increase the degree of commonality of electrons and enhance the metallicity. The conductivity analysis shows that both single-doped and codoped conductivity have been improved. When the elements are codoped, the conductivity is the largest, and the conductivity is the best.

Effect of nano-metal additives on the creep behavior of AgSnO2 contact materials

The creep behavior of the AgSnO2 contact materials with different nano-metal additives (Fe, Ni, Cu) was investigated at room temperature. The fracture surface was characterized by scanning electron microscope (SEM). The creep behavior and mechanism of the AgSnO2 materials without addition and with Cu, Fe and Ni were simulated and analyzed. It was found that the creep strain and creep rate of the AgSnO2 materials were obviously decreased due to the improvement of interface wettability between Ag and SnO2 by the incorporation of metal additive. The Cu additive exhibited the most remarkable effect on improving the creep resistance, following by Fe, Ni. The creep strain of the AgSnO2(Cu) materials was significantly decreased, about 60% lower than that of the material without additives. The experimental creep curves of the AgSnO2 materials with different nano additives agreed well with the Norton-Bailey power law. Moreover, the nano metal additives played a role in preventing or slowing creep voids growth which could be attributed to the interface strength enhancement and the improved load-transfer capability, evidenced by ABAQUS software. This work can provide a useful guideline for the optimization and design of Ag-matrix contact materials.

Study on Simulation and Experiment of Y-Mo Co-Doped AgSnO2 Contact Materials

Due to the shortcomings of AgSnO2 as a contact material, models of SnO2, Y-SnO2, Mo-SnO2, and Y-Mo-SnO2 were built to calculate their electrical and mechanical properties based on the first principles of density functional theory. The Y-Mo co-doped SnO2 was the most stable of all the models according to the enthalpy change and the impurity formation energy. By analyzing the energy band structure and the density of states, it was shown that the doped models are still direct bandgap semiconductor materials. The valence band moved up and the conduction band moved down after doping, reducing the band gap and enhancing conductivity. With the reduced energy for carrier transition, the electrical performance of Y-Mo co-doped SnO2 was improved best. The mechanical properties of SnO2 were completely improved by Y-Mo co-doping according to calculation results. The doped SnO2 materials were prepared by the sol-gel method, and the doped AgSnO2 materials were prepared by the powder metallurgy method. X-ray diffraction, hardness, conductivity and wettability experiments were undertaken, with experimental results showing that AgSnO2 can be improved comprehensively by Y-Mo co-doping, verifying the conclusions of the simulation. Overall, the present study provides an effective method for the preparation of high-performance contact materials.

Effect of Ni, N Co-Doped on Properties of AgSnO2 Contact Materials

The first-principles method based on density functional theory was used to analyze the impurity formation energies, energy bands, density of states, electron overlap population and elastic modulus of SnO2, SnO2–Ni, SnO2–N and SnO2–Ni–N. SnO2 powders with different additives were prepared by the sol-gel method, and then X-ray diffraction experiments and wettability experiments were carried out. The powder metallurgy method was used to prepare AgSnO2 contacts with different additives. The simulation experiments on hardness, electrical conductivity and electrical contact were carried out. The simulation results show that the conductivity of Ni–N co-doped SnO2 is best, and more impurity levels are introduced into the forbidden band, thereby increasing the carrier concentration, reducing the band gap, and improving the conductivity. The experimental results show that Ni, N doping does not change the structure of SnO2, so doped SnO2 still belongs to the tetragonal system. Ni–N co-doping can better improve the wettability between SnO2 and Ag, reduce the accumulation of SnO2 on the contact surface and reduce the contact resistance. Ni–N co-doped SnO2 has the smallest hardness, improving ductility, molding and service life of the AgSnO2 contact material.

Effect of La and Mo co-doping on the properties of AgSnO2 contact material

For the shortage of the AgSnO2 contact material, the models of SnO2, La–SnO2, Mo–SnO2, and La–Mo–SnO2 were built to calculate their electrical and mechanical properties based on the first principles of density functional theory in this study. The La-Mo co-coped SnO2 is the most stable of all the models according to the enthalpy change and the impurity formation energy. By analyzing the energy band structure and density of states, the doped models are still the direct bandgap semiconductor materials. The valence band moves up and the conduction band moves down after doped, reducing the band gap and enhancing the conductivity. With the reduced energy for carrier transition, the electrical performance of La-Mo co-doped SnO2 is improved best. The mechanical properties of SnO2 were completely improved by La-Mo co-doping with the calculation results. The doped SnO2 materials were prepared by sol-gel method and the doped AgSnO2 materials were prepared by powder metallurgy method. The x-ray diffraction experiment, hardness, conductivity and wettability experiment had been taken. And the experimental results show that the AgSnO2 can be improved comprehensively by La-Mo co-doping, verifying the conclusions of the simulation. It provides an effective method for the preparation of high-performance contact materials.

Effects of Ce and N Co-Doped on Properties of AgSnO₂ Contact Materials

AgSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , as the most potential material to replace AgCdO, is widely used in low-voltage electrical appliances. However, because of the high hardness and poor conductivity of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , AgSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has the problems of processing difficulties and large contact resistance. Based on the first principles of density functional theory, a method is proposed to calculate the electronic structure and mechanical properties of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -Ce, SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -N, and SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -Ce-N. By analyzing the energy band, density of states, and elastic constants, the results show that Ce-N co-doped SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has the highest relative conductivity, reduced hardness, and increased ductility and overcome processing difficulty. The doped AgSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> contact material was prepared by sol-gel method and powder metallurgy method, and the hardness and electrical properties of the sample were tested. The experimental results show that AgSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -Ce-N contacts have higher conductivity, lower contact resistance and arc energy, and lower hardness. The theory is consistent with the experiment, proving the feasibility of simulation. Therefore, Ce and N co-doping can effectively overcome the disadvantages of AgSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> contact materials, improve conductivity, and overcome processing difficulty. It provides a new idea and theoretical basis for the doping research of AgSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> contact materials.

Investigation of Arc Erosion Mechanism for Tin Dioxide-Reinforced Silver-Based Electrical Contact Material Under Direct Current

To get an in-depth insight into the arc erosion mechanism for tin dioxide-reinforced silver-based (Ag-SnO2) contact material, the contact pairs made of Ag-4wt%SnO2 contact material were, respectively, performed for 20,000 switching operations under the direct currents of 19 A and 29 A and the voltage of 12 V, together with the electrode gap of 4 mm. The eroded surfaces and cross-sectional morphologies and the chemical compositions were characterized by scanning electron microscopy equipped with an energy dispersive spectrometer (EDS). The results show that there is a deep erosion pit at the cathode and an apparent protrusion at the anode, suggesting that a serious material transfer generates from cathode to anode. The EDS results show that the Sn contents at the protrusion and at the region around the crater are below 0.75 wt.% and 4 wt.%, respectively. This reveals that SnO2 undergoes severe evaporation during electrical contact testing. Moreover, arc stability decreases with increasing the load current, and the Ag-SnO2 contact material has larger arc power (make arc: 68.2 J/s; break arc: 58.53 J/s at 29 A) as compared to Ag-TiB2 contact material (make arc: 62.85 J/s; break arc: 50.01 J/s at 29 A). As a result, it is thought that SnO2 evaporation reduces Ag dissipation, thus shortening the lasting time of the make arc. However, the emission current is increased owing to the low work function of SnO2, which further promotes the improvement in the density of the charged particles, thereby enhancing the arc power. Additionally, the large density of charged particles can sustain arc burning for a longer time, resulting in an extended break arc duration.

Research on Simulation, Experiment and Evaluation Method of Different Ratio Gd Doped AgSnO₂ Contact Material

AgSnO2 electrical contact material with greenery and good performance has the most potential to replace the toxic AgCdO. However, SnO2 in AgSnO2 contact material is a kind of semiconductor with wide band gap, which is almost insulated and has high hardness, resulting in the increase of contact resistance and temperature rise, and easy to form microcracks. First principle based on density functional theory are used to simulate three doping ratios (8.3%, 12.5%, 16.7%) of rare earth element Gd doped SnO2. The simulation results show that when the doping ratio is 12.5%, electrical performance is the best. As the doping ratio increases, the smaller the hardness, the higher the probability of microcracks. To more objectively obtain the doping ratio with the best comprehensive performance, the comprehensive evaluation model of Technique for Order Preference by Similarity to Ideal Solution with entropy weight is adopted to evaluate, and the performance with doping ratio of 12.5% is the best. Finally, it is verified by experiments. Different ratio of Gd doped SnO2 powders are prepared by the sol-gel method, and the X-ray diffraction test proves that the sol-gel method can realize the substitution doped model established by simulation. The doped AgSnO2 is prepared by powder metallurgy method, and its electrical performance and hardness are measured. The theory and experiment can be well matched, which proves the feasibility and credibility of simulation. It provides a new idea and scientific reference for the research on doping to improve the properties of AgSnO2 contact material.

Porównanie obniżenia charakterystyk oraz badanie mechanizmu uszkodzeń materiałów stykowych z kompozytów typu srebro-tlenek metalu stosowanych w przekaźnikach elektromagnetycznych na podstawie danych z symulacji komputerowej

To evaluate the electrical contact behaviors of silver metal oxide contact materials in relays application more accurately, and to guide the selection of contact materials, the test device and testing method for simulating electrical contact performance in relays application were analyzed in this paper. The electrical contact simulation test system was designed and developed, which can easily simulate contact materials. The contact resistance, static force and rebound energy degradation parameters of AgSnO2, AgCdO and AgNi contact materials under the same load conditions were obtained through experimental research, the contact resistance and arcing energy degradation parameters of AgSnO2 under different opening distances were acquired at the same time. The result indicated that accurate data are received by the electrical contact simulation testing method. Finally, based on the test data, the degradation performance of three selected test materials was tested, and the failure mechanism of AgSnO2 materials was analyzed.