Wear Reduction via CNT Coatings in Electrical Contacts Subjected to Fretting

Carbon nanotubes (CNT) are of great interest to the research community due to their outstanding mechanical, transport, and optical properties. These nanoparticles have also shown exceptional lubricating capabilities, which coupled with their electrical conductivity show promising results as solid lubricants in electrical contacts. In this study, three diferent CNT coatings were deposited over copper platelets via electrophoretic deposition and subsequently tribo-electrically characterized including electrical contact resistance evolution during fretting wear, wear protection, chemical analysis of fretting marks, as well as infuence of CNT coating thickness, duration and normal load applied during fretting, and atmospheric humidity. Thicker CNT coatings show improved wear protection while retaining similar electrical behavior as uncoated copper, or even improving its electrical contact resistance. Moreover, the compaction of the porous CNT coating is crucial for optimal electrical performance at low humidity. For longer fretting tests (150,000 and 500,000 cycles), the coatings are displaced thus afecting the wear protection ofered. However, the coatings stabilize and reduce ECR compared to uncoated samples. Furthermore, thicker CNT coatings can bear higher loads during fretting due to the increased lubricant reservoir, with carbonaceous triboflm remaining at the contacting interface after 5,000 fretting cycles regardless of normal load

Electrical Characterization of Carbon Nanotube Reinforced Silver and Copper Composites for Switching Contacts

Carbon nanotube (CNT)-reinforced silver and copper metal matrix composites—at three different reinforcement phase concentrations (0.5 wt.%, 0.75 wt.%, and 1 wt.%)—were produced via powder metallurgy and sintered via hot uniaxial pressing. Optical and electron microscopy techniques were used to characterize the powder mixtures and sintered composites. The latter were also electrically characterized via load-dependent electrical contact resistance (ECR) and surface fatigue tests. Particle size and morphology play a crucial role in CNT deposition onto the metallic powder. CNT were deposited exceptionally well onto the dendritic copper powder regardless of its larger size (compared with the silver flakes) due to the higher surface area caused by the grooves and edges of the dendritic structures. The addition of CNT to the metallic matrices improved their electrical performance, in general outperforming the reference material. Higher CNT concentrations produced consistently low ECR values. In addition, high CNT concentrations (i.e., 1 wt.%) show exceptional contact repeatability due to the elastic restitutive properties of the CNT. The reproducibility of the contact surface was further evaluated by the fatigue tests, where the composites also showed lower ECR than the reference material, rapidly reaching steady-state ECR within the 20 fatigue cycles analyzed

INTEROPERABILITY OF PUBLIC HEALTH INFORMATION SYSTEMS IN THE STATE OF AMAPÁ

Interoperability in public health has major advantages over agility gains throughout the state bureaucratic logistics system. This agility is fundamental to help relieve the highest demand in all areas of health sciences in the Brazilian public service. This short communication aims to inform the population of Amapa and the academic community about the implementation of interoperability of public health services in the state of Amapá. The service is already in its implementation phase and is expected to end and be fully used by early 2020.A interoperabilidade em saúde pública tem grandes vantagens sobre os ganhos de agilidade em todo o sistema de logística burocrática do estado. Essa agilidade é fundamental para ajudar a aliviar a maior demanda em todas as áreas das ciências da saúde no serviço público brasileiro. Esta breve comunicação visa informar a população do Amapá e a comunidade acadêmica sobre a implementação da interoperabilidade dos serviços públicos de saúde no estado do Amapá. O serviço já está em sua fase de implementação e deve terminar e ser totalmente utilizado no início de 2020

Multipurpose setup used to characterize tribo-electrical properties of electrical contact materials

Electrical contacts are pervasively found on countless modern devices and systems. It is imperative that connecting components present adequate electrical, mechanical, and chemical characteristics to fulfill the crucial role that they play in the system. To develop an electrical contact material that is tailored for a specific application, different approaches are pursued (e.g., coatings, reinforced composites, alloyed metals, duplex systems, etc.). The manufacturing of electrical contact materials demand a thorough characterization of their electrical properties, mechanical properties, and their resistance to wear, as well as their resistance to atmospheric conditions. Accordingly, commissioning of a novel setup enables a more comprehensive study of the materials that are developed. Therefore, a complete understanding of the material's electrical and tribological characteristics are attained, allowing the production of a material that is compliant with the particular demands of the application for which it is intended. This multipurpose setup was built with higher precision stages and higher accuracy 3-axis force sensor, thus providing the following improvement over the preceding setup: • Elevated load-bearing capacity (double), higher precision and stability. • Tribo-electrical characterization (implementation of scratch and fretting tests). • Environmental control (climate and external vibration)

Near Superhydrophobic Carbon Nanotube Coatings Obtained via Electrophoretic Deposition on Low‐Alloy Steels

Sucker rods are a key element in certain oil-extraction processes as they link the motor group on the surface with the pumps located downhole. During the transport from the production site toward the extraction well, these components are prone to corrosion. A hydrophobic carbon nanotube (CNT) coating, deposited via electrophoretic deposition (EPD), is proposed as a protective layer, shielding the rods from harsh environmental conditions. Three different coating systems are considered and thoroughly characterized (depending on the additive that is used to deposit the CNT), namely, magnesium nitrate hexahydrate (Mg–Nit), triethylamine (TEA), and a duplex coating (DD). The latter presents an approach which combines the advantages of each additive, mechanical stability from Mg–Nit and strong hydrophobicity from TEA (near superhydrophobic). The former coatings are further processed to overcome their individual shortcomings, resulting in an increase in the coating's stability for TEA coating, as well as transforming the hydrophilic Mg–Nit surface into a hydrophobic surface

Comprehensive Study on Carbon-Coated Silver for Improved Tribo-Electrical and Wetting Performance

The rise in electrification has considerably increased the demand for high-efficiency and durable electrical contact materials. Carbon nanoparticles (CNP) are a promising coating material due to their intrinsic transport properties (thus minimizing the impact on conductivity), their proven solid lubricity (potentially improving tribological performance), and their hydrophobic wetting behavior (potentially providing atmospheric protection). In this study, carbon nanotube and nanohorn coatings are produced via electrophoretic deposition on silver-plated surfaces, followed by tribo-electrical and wetting characterization. The proposed coatings do not negatively affect the conductivity of the substrate, showing resistance values on par with the uncoated reference. Tribo-electrical characterization revealed that the coatings reduce adhesive wear during fretting tests while maintaining stable and constant electrical contact resistance. Furthermore, CNP-coated surfaces show a hydrophobic wetting behavior toward water, with graphite and carbon nanotube (CNT) coatings approaching super-hydrophobicity. Prolonged exposure to water droplets during sessile drop tests caused a reduction in contact angle (CA) measurement; however, CNT coatings’ CA reduction after five minutes was only approximately 5◦ . Accordingly, CNP (specifically CNT) coatings show auspicious results for their application as wear and atmospheric protective barriers in electrical contacts

Evaluating the effect of unidirectional loading on the piezoresistive characteristics of carbon nanoparticles

The piezoresistive efect of materials can be adopted for a plethora of sensing applications, including force sensors, structural health monitoring, motion detection in fabrics and wearable, etc. Although metals are the most widely adopted material for sensors due to their reliability and afordability, they are signifcantly afected by temperature. This work examines the piezoresistive performance of carbon nanoparticle (CNP) bulk powders and discusses their potential applications based on strain-induced changes in their resistance and displacement. The experimental results are correlated with the characteristics of the nanoparticles, namely, dimensionality and structure. This report comprehensively characterizes the piezoresistive behavior of carbon black (CB), onionlike carbon (OLC), carbon nanohorns (CNH), carbon nanotubes (CNT), dispersed carbon nanotubes (CNT-D), graphite fakes (GF), and graphene nanoplatelets (GNP). The characterization includes assessment of the ohmic range, load-dependent electrical resistance and displacement tracking, a modifed gauge factor for bulk powders, and morphological evaluation of the CNP. Two-dimensional nanostructures exhibit promising results for low loads due to their constant compression-todisplacement relationship. Additionally, GF could also be used for high load applications. OLC’s compression-to-displacement relationship fuctuates, however, for high load it tends to stabilize. CNH could be applicable for both low and high loading conditions since its compression-to-displacement relationship fuctuates in the mid-load range. CB and CNT show the most promising results, as demonstrated by their linear load-resistance curves (logarithmic scale) and constant compression-todisplacement relationship. The dispersion process for CNT is unnecessary, as smaller agglomerates cause fuctuations in their compression-to-displacement relationship with negligible infuence on its electrical performance

Characterization and electrical analysis of carbon-based solid lubricant coatings

The use of electrical devices has skyrocketed over the past decades, increasing the demand for electrical connectors worldwide. Therefore, it is of utmost importance to produce more reliable, energy and material efficient, and durable electrical contact material systems; particularly in low-redundancy systems, such as in passenger vehicles. This work analyzes the potential use of carbon nanoparticle coatings applied via electrophoretic deposition over copper substrates to reduce wear, require lower insertion forces, and to protect the connectors from atmospheric conditions, while reducing the gain on the overall resistance of the system. Four carbon nanoparticles were considered due to their well-known solid-lubricating capabilities, namely: graphite flakes, graphene oxide, carbon nanotubes, and carbon nanohorns. Through a comprehensive characterization of the coatings, aspects like coating topography, compactness, thickness, elasticity, and electrical contact resistance were analyzed. Carbon nanotubes and nanohorns proved to have the highest potential. In addition to their previously documented outstanding solid-lubricity and environmental protection - after chemical modification of the coatings’ surfaces - these nanoparticles showed low resistance values for loads above 4 N, i.e., below 400 mΩ. Moreover, the coatings produced were thin and homogeneous, with adequate mechanical stability, and elastic behavior

Evaluating the effect of unidirectional loading on the piezoresistive characteristics of carbon nanoparticles

Abstract The piezoresistive effect of materials can be adopted for a plethora of sensing applications, including force sensors, structural health monitoring, motion detection in fabrics and wearable, etc. Although metals are the most widely adopted material for sensors due to their reliability and affordability, they are significantly affected by temperature. This work examines the piezoresistive performance of carbon nanoparticle (CNP) bulk powders and discusses their potential applications based on strain-induced changes in their resistance and displacement. The experimental results are correlated with the characteristics of the nanoparticles, namely, dimensionality and structure. This report comprehensively characterizes the piezoresistive behavior of carbon black (CB), onion-like carbon (OLC), carbon nanohorns (CNH), carbon nanotubes (CNT), dispersed carbon nanotubes (CNT-D), graphite flakes (GF), and graphene nanoplatelets (GNP). The characterization includes assessment of the ohmic range, load-dependent electrical resistance and displacement tracking, a modified gauge factor for bulk powders, and morphological evaluation of the CNP. Two-dimensional nanostructures exhibit promising results for low loads due to their constant compression-to-displacement relationship. Additionally, GF could also be used for high load applications. OLC’s compression-to-displacement relationship fluctuates, however, for high load it tends to stabilize. CNH could be applicable for both low and high loading conditions since its compression-to-displacement relationship fluctuates in the mid-load range. CB and CNT show the most promising results, as demonstrated by their linear load-resistance curves (logarithmic scale) and constant compression-to-displacement relationship. The dispersion process for CNT is unnecessary, as smaller agglomerates cause fluctuations in their compression-to-displacement relationship with negligible influence on its electrical performance