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

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.

Feasibility of Carbon Nanoparticle Coatings as Protective Barriers for Copper─Wetting Assessment.

Copper is extensively used in a wide range of industrial and daily-life applications, varying from heat exchangers to electrical wiring. Although it is protected from oxidation by its native oxide layer, when subjected to harsh environmental conditions─such as in coastal regions─this metal can rapidly degrade. Therefore, in this study, we analyze the potential use of carbon nanoparticle coatings as protective barriers due to their intrinsic hydrophobic wetting behavior. The nanocarbon coatings were produced via electrophoretic deposition on Cu platelets and characterized via scanning electron microscopy, confocal laser scanning microscopy, and sessile drop test; the latter being the primary focus since it provides insights into the wetting behavior of the produced coatings. Among the measured coatings, graphite flakes, graphene oxide, and carbon nanotube (CNT) coatings showed superhydrophobic behavior. Based on their wetting behavior, and specifically for electrical applications, CNT coatings showed the most promising results since these coatings do not significantly impact the substrate's electrical conductivity. Although CNT agglomerates do not affect the wetting behavior of the attained coatings, the coating's thickness plays an important role. Therefore, to completely coat the substrate, the CNT coating should be sufficiently thick─above approximately 1 µm.

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).