Optimized interfacial integrity in CNTFI/CNTs-Cu composites for enhanced electromechanical and joule heating performance

Abstract

Fractured carbon nanotube fibers (CNTFs) often suffer from poor electrical and mechanical performance after damage, limiting their use in current-carrying and Joule heating applications. CNTF composites are particularly well suited for Joule heating based on their high thermal stability, electrical properties, high current density. In this work, CNTF joints reinforced with CNT-Cu bilayer structures were successfully fabricated to restore and improve their functional properties. CNTFI/CNT joints were first prepared through electrothermal-induced solvent evaporation (EISE), followed by Cu deposition using a meniscus-confined electrochemical deposition (MECD) process to produce CNTFI/(CNTs-Cu) joints. Microstructural characterization confirmed uniform CNT distribution and successful Cu incorporation at the joint interface. Statistical analysis of electrical measurements confirms that the CNT/Cu bilayer architecture significantly improves conductivity, reducing the average resistance from 34.0 ± 1.7 Ω for pristine CF to 18.0 ± 0.50 Ω (for n= 4) in engineered joints, with excellent reproducibility. Statistical thermal analysis confirmed enhanced stability after Cu deposition, with weight loss values of 21.7 ± 0.2%, 36.2 ± 0.3%, 40.2 ± 0.6%, and 48.9 ± 0.4% for pristine fiber, CNTFI/(CNTs-Cu)₁, CNTFI/(CNTs-Cu)₂, and CNTFI/(CNTs-Cu)₃, respectively. The CNTFI/(CNTs-Cu)₃ sample exhibited superior thermal resistance due to its dense Cu coating. Mechanical testing further revealed improved tensile strength, ductility, and toughness, while statistical analysis confirms highly consistent strain 6.9%± 0.035% (n = 4) and moderate stress variability 118.0 MPa±1.23 Mpa (for n = 4), indicating good reproducibility with acceptable dispersion in mechanical performance.