Electrical Contact Materials Research Articles

Unraveling the new role of La on arc erosion behavior of C/Cu-based electrical contacts

Copper/carbon (C/Cu) electrical contact materials are widely used in low-voltage appliances due to their exceptional conductivity and anti-ablation properties. However, the oxidation of Cu during operation and the suboptimal wettability at the C/Cu interface negatively impact its arc-resistant performance. This study explores the potential for enhancing the arc-resistant characteristics of C/Cu electrical contact materials through the alloying of La in Cu. The findings indicate that La alloying in Cu significantly decreases the contact resistance (from 50 mΩ to 2.2 mΩ) and mass loss (by 50%) of C/Cu electrical contact materials.

Kinetic Study of Oxidation of Ag-Sn-Zn Solid Solution Powders via Hot Mechanochemical Processing.

Ag-based electrical contact materials are essential in low-voltage devices such as relays, switches, circuit breakers, and contactors. Historically, Ag-CdO composites have been preferred due to their superior electrical and thermal conductivities, resistance to arcing, and mechanical strength. However, the toxicity of Cd has led to increased restrictions on its use. With the aim of contributing to the development of a new environment-friendly, Ag-Zn2SnO4-based electrical contact material, the kinetics of the hot mechanochemical oxidation of a Ag-Sn-Zn solid solution obtained by mechanical alloying were investigated. The results indicated that the proposed synthesis route produces Ag-based composites with a homogeneous distribution of nanoscale Zn2SnO4 precipitates, which is unattainable through conventional material processing methods. This kinetic study established that the mechanochemical oxidation of the Ag-Sn-Zn solid solution follows the Johnson-Mehl-Avrami-Kolmogorov model. An analysis of the microstructure and the relationship between the activation energy "Ea" and the Avrami exponent "n" from experimental data fitting suggests that the primary mechanism for the oxidation of the Ag-Sn-Zn solid solution during the hot mechanochemical process is related to the three-dimensional oxide growth being limited by oxygen diffusion after its immediate initial nucleation.

Research on the influence of different organizational structures on the electrical life of sealed relays

Abstract A sealed relay is a type of power relay mainly used in fields with harsh environments, low noise requirements, or high-reliability requirements. It is used in scenarios such as vehicle loads, household appliances, industrial control, and motors. At the same time, when the input meets certain specified conditions, it is a device that can generate a jump in one or more electrical output circuits, playing a role in controlling the on/off current of the connected circuit. Power relays have been widely used in various fields due to their small size, low noise, and low power consumption advantages. This article mainly studies the electrical parameters such as arc energy, arc time, welding force, and contact burning principle of silver tin oxide electrical contact materials produced by different processes, providing a reference for the development of electrical contact materials.

Improving mechanical and electrical contact performance of silver based electrical contact material reinforced by flower spherical zinc oxide loaded with silver nanoparticles

Flower spherical ZnO loaded with Ag nanoparticles was synthesized by hydrothermal method. Ag/ZnO electrical contact materials were prepared by powder metallurgy combined with hot extrusion technique. During the hydrothermal reaction, Ag nanoparticles entered the interlayer gaps of flower spherical ZnO and uniformly deposited on its surface. The tensile mechanical test results indicate that the Ag/ZnO electrical contact materials prepared by ZnO, Ag@ZnO(75 wt%) and Ag@ZnO(50 wt%) exhibited elongations of 6.8 %, 13.8 % and 12.1 %, respectively. This result indicates that appropriate loading of Ag nanoparticles on flower spherical ZnO could significantly improve the mechanical properties of Ag/ZnO electrical contact materials. The contact resistance of electrical contact materials significantly affects their temperature rise characteristics. During 20, 000 cycles process, Ag/ZnO electrical contact material prepared by Ag@ZnO(50 wt%) exhibited the lowest temperature rise of 6.33 K under the conditions of DC 36 V/10 A. Considering both mechanical and electrical contact performance, Ag/ZnO electrical contact materials prepared by Ag@ZnO(50 wt%) exhibited the optimum overall performance.

Designed bimetallic layer-encapsulated tungsten powders for reinforcing tungsten-silver matrix composite electrical contact materials

Electrical contact materials (ECMs) play a pivotal role in maintaining the stability and efficiency of electrical instruments and electronic devices by regulating the current flow. As an essential member of ECMs, W-Ag matrix composite ECMs (W-Ag-MC-ECMs) are integral, demonstrating commendable resistance to welding and arc erosion. However, the limited wettability between the two phases curtails their broader applications. Herein, Ag-Cu and Ag-Ni bimetallic layer-encapsulated tungsten powders were designed and successfully synthesized through a two-step electroless plating process. Subsequently, the W-Ag-MC-ECMs were fabricated following the powder metallurgy route, including the solution ball milling process and the spark plasma sintering technique. The results indicated that Cu-Ag solid solution and Ni with a metal binder effect could strengthen the interface bonding, which can dramatically improve the microhardness (up to 182HV), strength (up to 600 MPa), ductility (up to 24 %) and resistance to arc erosion (nearly two times longer service life). In addition, during the arc erosion, attributed to the Cu-Ag solid solution effect of W@Ag@Cu/Ag-MC-ECMs and solution-strengthening effect of W@Ag@Ni/Ag-MC-ECMs, the work function increases and the arc energy decreases, which reduces mass loss and extends the service life of the contacts.

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.

Adhesion, Stability and Electronic Properties of Ag/SnO2 Interface from First‐Principles Calculation

AbstractThe interfacial bonding state between each oxide and the silver matrix in AgCuOIn2O3SnO2 electrical contact materials remains unclear. To address this, first‐principles calculations using density‐functional theory are employed to establish the low‐index surfaces of Ag and SnO2 and perform convergence tests. Computational results reveal that the Ag (111) surface and the SnO2(110)‐O surface exhibit the highest stability among their respective low‐index surfaces. Consequently, these surfaces are chosen to form the interfacial model, and their atomic structure, adhesion work, and interfacial energies are systematically analyzed. The results demonstrate that the stability and interfacial bonding strength of the Ag(111)/SnO2(110)‐O interface are high, exhibiting metallic properties and strong conductivity. Moreover, at an interface spacing of d0 = 2.4 Å, the interface stability is optimal. The redistribution of charge at the interface induces significant changes in the local atomic density of states, particularly noticeable in the Ag and O atoms. Additionally, the Ag/SnO2 interface is predominantly bonded through ionic interactions, contributing to its robust bonding.

Optimization of Cyanide-Free Composite Electrodeposition Based on π-π Interactions Preparation of Silver-Graphene Composite Coatings for Electrical Contact Materials.

With the rapid development of industrial automation and power electronics, the requirements for electrical contact materials are increasing. However, traditional electrical contact materials encountered significant bottlenecks in terms of performance enhancement and production environmental friendliness. Therefore, this paper proposes a new material design idea that utilizes π-π interactions between graphene and compounds with conjugated structures in order to achieve uniform dispersion of graphene in the metal matrix and thus enhance the performance of composites. Based on this design idea, we used nicotinic acid, which has a conjugated structure and is safe, as the complexing agent, and successfully prepared high-quality silver-graphene (Ag-G) composite coatings with graphene uniformly dispersed in the metal matrix on copper substrates by composite electrodeposition technique. Subsequently, the mechanical properties of composite coatings were investigated by hardness test and X-ray diffractometer, and the tribological properties of the composite coatings and the comprehensive performance under the current carrying conditions were systematically evaluated by using friction and wear tester and load key life tester. The results show that the Ag-G composite coatings have significant advantages in mechanical, tribological, and current carrying conditions. This result not only verifies the feasibility of the design idea of the material, but also provides a new direction for the research and development of electrical contact materials.

Lubrication performance of graphene in the sliding electrical contact interface

Electrical contact materials are increasingly widely used, but the existing electric contact lubricants still have lots of room for improvement, such as anti-wear performance and lubrication life. Due to the excellent electrical and lubrication properties, graphene shows great potential in lubricating the sliding electrical contact interface, but there is a lack of relevant research. Some researchers have studied the lubrication performance of graphene between the gold-coated/TiN-coated friction pair at an ultra-low current. However, the lubrication performance of graphene on more widely used electrical contact materials such as copper and its alloys under larger and more commonly used current or voltage conditions has not been reported. In this paper, we study the lubrication performance of graphene in the copper and its alloys sliding electrical contact interface under usual parameters, which is explored through four aspects: different substrates—copper and brass, different test methods—constant voltage and constant current, different normal loads and durability test. The experiments demonstrate that graphene can significantly reduce the friction and wear on brass and copper under the above test methods and parameters, with low contact resistance at the same time. Our work is expected to provide a new lubricant for electrical contact materials and contribute to enriching the tribological theory of graphene.

Effect of the contact load and rotation speed on the formation of rolling current-carrying arc and the corresponding material damage

The current-carrying arc is a critical factor that affects the electrical contact performance and material damage of contact pairs. In this study, a copper disk–copper disk pair was used to simulate the rolling electrical joint in a conductive rotating joint. Under operating conditions with a current of 2 A, rotation speeds from 4 to 600 r/min, and loads from 40 to 180 N, the dynamic behavior of the current-carrying arc and the surface damage mechanism were investigated. The movement characteristics of the arc at the friction interface were observed, and the arc generation difficulty and intensity were statistically analyzed based on the arc burning rate and arc energy. With increasing load and rotation speed, the generation of current-carrying tribological arcs became easier, and both the arc burning rate and arc energy increased. After the arc was generated, the arc root position was randomly distributed at the contact interface, exhibiting dynamic phenomena such as splitting and merging. Following the generation of the arc, the dominant damage mechanism at the current-carrying friction interface transitioned from mechanical damage to electrical damage. The manifestations of electrical damage included burning, oxidation, and roughening, with the degree of electrical damage positively correlated with the arc burning rate and arc energy. Surface oxidation could reduce the adhesion between metal contact pairs, contributing to a decrease in the current-carrying friction coefficient. Simultaneously, the film resistance caused by oxidation and the contraction resistance caused by roughening could lead to an increase in the average contact resistance.

Orientation-dependent tribological behavior of the graphite–diamond composite

Coherent interfacial graphite–diamond composite (Gradia) is superhard and conductive, promisingly applied as electric contact material. In this work, large-scale atomistic simulations were performed to investigate its tribological behavior. Depending on the orientation between graphite–diamond interface and loading direction, three structural evolution modes were observed under compression, featuring Gradia to diamond, Gradia to graphite, and Gradia to defective carbon. Coefficient of friction and wear rate were found orientation-dependent. Orientations of graphite-, diamond-, and defective-preferred structural evolution showed different performance. A satisfied balance between tribological performance and conductivity (rich of sp2-carbon) is obtained in the defective-preferred orientation. These results demonstrate the great potential for Gradia using in dynamic electrical contact and provide a theoretical basis for further material design.

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 M-site element on the interaction of M2AlC and Ag and the induced properties of Ag/M2AlC composites

The deintercalation of weakly bonded A element affects the microstructure and properties of MAX phases and their reinforced composites. In this work, the effect of M-site element on the interaction of Al-containing M2AlC (M = V, Cr) phase and Ag, and the induced properties of Ag/M2AlC electrical contact materials (ECMs) were investigated. Though Ag and Al are soluble to each other and can form intermetallics, the variation of M element significantly affected the vacancy formation of Al, and thereby the interfacial reaction of Ag/M2AlC. The difficult formation of Al vacancy in V2AlC contributed to no obvious interfacial reaction in Ag/V2AlC. But the easy deintercalation of Al atoms in Cr2AlC led to their massive replacement by Ag, which generated Ag nano-twins and Cr3C2 with the same crystallographic relationship in one original Cr2AlC, and Cr7C3 and Ag3Al as well. Due to the distinct interactions, the resistivities of Ag/V2AlC and Ag/Cr2AlC increased by roughly 1 and 5 times after sintering, respectively. The low resistivity and proper hardness of the sintered Ag/V2AlC, which were very close to those of the “all-purpose” commercial Ag/CdO, contributed to its superior arc erosion resistance.

Erosion behaviors and mechanisms of Ti3AlC2 material under arc discharge in various mixed atmospheres

The present study establishes an experimental platform for investigating arc erosion and explores the erosion characteristics of Ti3AlC2 material under a voltage of 10 kV in SF6/N2, SF6/CO2, and N2/CO2 environments. Our findings reveal that the arc energy and duration exhibit a gradual increase in the sequence of SF6/N2, SF6/CO2, and N2/CO2, while the breakdown strength decreases. Scanning electron microscopy (SEM) and a three-dimensional laser confocal microscope were employed to observe uneven erosion morphology. Additionally, high-speed camera footage captures the arc bending and drifting phenomenon caused by Rayleigh-Taylor instability between the arc and gas. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis were utilized to characterize the composition of eroded surfaces. Erosion models were proposed for each mixed atmosphere along with comprehensive discussions on their underlying mechanisms. This work expands the application scope of MAX phase materials while providing a theoretical foundation for designing electrical contact materials.

The thermal stability of Ti2AlC and Ag/Ti2AlC in Ar and air

Ag/Ti2AlC electrical contact material is a new type of environmentally friendly alternative material for Ag/CdO due to the good wettability and conductivity of Ti2AlC. However, the thermal stability and moderate oxidation sensitivity of Ti2AlC put restrictions on Ag/Ti2AlC materials manufacturing and application. Therefore, the thermal stability and oxidation behavior of Ti2AlC and Ag/Ti2AlC in air and Ar were analyzed by TG-DSC, XRD, SEM, EPMA and thermodynamic calculation. The practical periodic oxidation behavior of Ti2AlC and mixed Ag/10Ti2AlC powders at 300–900 °C in air and Ar atmosphere was studied. The negative effect of Ag diffusion into Ti2AlC particles on Ti2AlC’ s thermal stability was demonstrated. In addition, the different behavior of Ti and Al atom during the sintering process of Ag/10Ti2AlC in air at different temperature were also discussed and combined with the periodic oxidation of Ti2AlC.

Microstructure and arc-induced degradation of Ag/Ti3AlC2 composites with varying particle size of Ti3AlC2

Nano-layered ternary compounds Mn+1AXn phases combine properties of both ceramics and metals, holding promising prospect for various applications. In this work, the microstructure evolution of coarse Ti3AlC2 particles, as well as the microstructure, physical properties and arc-induced degradation of Ag/Ti3AlC2 electrical contact materials (ECMs) with varying particle sizes of Ti3AlC2 were investigated. The Ti3AlC2 particles milled by vibration were inhomogeneous, whereas those milled through high energy ball milling for 3 h were basically uniformly refined and delaminated to nano-flakes with edge length of ∼100–350 nm without obvious decomposition. With decreasing particle size, the interaction between Ag and Ti3AlC2 was enhanced, thus mitigating the decrease of density and hardness after sintering. Though fine Ti3AlC2 particles led to increased hardness, easier decomposition of finer Ti3AlC2 during both sintering and arc erosion resulted in greater thermal accumulation and accelerated erosion process, thus negatively impacting the arc erosion resistance of Ag/Ti3AlC2 ECMs.

Effect of Nb Doping on the Electrical Contact Properties of AgNi Contact Materials

AgNi contact materials have received widespread attention with the acceleration of the process of replacing AgCdO contact materials. However, the practical applications of AgNi contact materials are limited due to its disadvantage of poor resistance to melting welding. Firstly, following the first principles of the density functional theory, we simulated and tested an interfacial model of AgNi doped with varying amounts of Nb. Next, we fabricated AgNi electrical contact materials. Subsequently, we conducted electrical contact tests. Finally, the impact of Nb doping on the arc erosion behavior of AgNi electrical contact materials was analyzed. The results indicate that, with an increase in Nb doping content, the electrical contact performance and the degree of arc erosion exhibit a trend of initially decreasing and then increasing, which aligns with the simulation results. The mean values of arc energy, arc duration, and welding force for the material doped with 4.55% Nb were 181.02 mJ, 9.43 mS, and 38.45 cN, respectively. Moreover, the anode is more responsive to changes in Nb content compared to the cathode. The introduction of Nb enhances the viscosity of the molten pool in the AgNi electrical contact. Furthermore, the mechanisms of grain boundary strengthening and solid solution strengthening by Nb improve the weld performance resistance of the contact.

First-Principles and Experimental Study of Ge, V, Ta-Doped AgNi Electrical Contact Materials

To explore the stability, electrical, and mechanical characteristics of undoped AgNi alongside AgNi doped with elemental Ge, V, and Ta, we performed calculations on their electronic structures using density functional theory from first-principles. We also prepared AgNi(17) and AgNi-x(Ge, V, Ta) electrical contact materials using the powder metallurgy technique, and they were subsequently assessed experimentally. The electrical properties of these materials were evaluated under a 24 V/15 A DC-resistive load using the JF04D contact material testing system. A three-dimensional morphology scanner was employed to examine the contact surface and investigate the erosion patterns of the materials. Our findings indicate that doping with metal elements significantly enhanced the mechanical properties of electrical contacts, including conductivity and hardness, and optimizes arc parameters while improving resistance to arc erosion. Notably, AgNi-Ge demonstrated superior conductivity and arc erosion resistance, showing significant improvements over the undoped AgNi contacts. This research provides a theoretical foundation for selecting doping elements aimed at enhancing the performance of AgNi electrical contact materials.

Interfacial wettability and electrical properties of Ni-doped Ag/Bi2Sn2O7 electrical contact materials

Interfacial wettability and electrical properties of Ni-doped Ag/Bi2Sn2O7 electrical contact materials

Current carrying tribological properties of multi arc ion plated titanium nitride doped silver coating

Sliding electrical contact materials play a crucial role in the transmission and conversion of electrical energy, but due to various factors such as force, electricity, and heat, the interface exhibits complex wear behavior. A single solid or liquid lubrication system can no longer meet the growing performance requirements of current carrying tribology. In this study, a TiN-Ag coating was prepared using multi arc ion plating technology, and a solid–liquid composite lubrication system was formed with ionic liquid and polyurea grease, respectively. Through current carrying friction and wear tests, their tribological properties, electrical contact resistance(ECR) values, and stability were tested, and compared with the results obtained during dry friction. The coating and worn surfaces were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results indicated that compared with dry friction, TiN-Ag coatings lubricated with ionic liquids and polyurea grease showed higher friction reduction, wear resistance, and conductivity, especially the synergistic effect between ionic liquids and coatings is prominent. The behavior of ionic liquids under voltage was analyzed, and it was found that ionic liquids formed a physical adsorption film composed of a mixture of anions and cations on the worn surface. The ordered layered structure improved the tribological performance of the system.