Electrical conductivity of carbon nanofiber reinforced resins: Potentiality of Tunneling Atomic Force Microscopy (TUNA) technique

Abstract

Epoxy nanocomposites able to meet pressing industrial requirements in the field of structural material have been developed and characterized. Tunneling Atomic Force Microscopy (TUNA), which is able to detect ultra-low currents ranging from 80 fA to 120 pA, was used to correlate the local topography with electrical properties of tetraglycidyl methylene dianiline (TGMDA) epoxy nanocomposites at low concentration of carbon nanofibers (CNFs) ranging from 0.05% up to 2% by wt. The results show the unique capability of TUNA technique in identifying conductive pathways in CNF/resins even without modifying the morphology with usual treatments employed to create electrical contacts to the ground.Epoxy matrix-based composite materials filled with MWCNTs or various carbon additives, such as natural, artificial and exfoliated graphites (EGs), activated carbons, and thick graphene exhibit many properties of great interest both from a scientific and industrial point of view such as low electrical percolation threshold (below 1.5 wt.%) as well as high electromagnetic interference (EMI) shielding capacity, good adhesive properties etc… [1].CNF-reinforced polymer composites have opened up new perspectives for multifunctional materials. In particular, carbon nanofibers play a promising role due to their potential applications in order to improve mechanical, electrical, thermal performance and relative ease of processing in composites used in the aerospace field [2][3][4][5][6][7]. Moreover, in high performance resin formulations, CNFs can be used as effective low-cost replacements for carbon nanotubes (CNTs) since the cost of CNFs is much lower than that of CNTs while possessing similar physical properties. The tetrafunctional epoxy resin tetraglycidyl methylene dianiline (TGMDA) cured with the aromatic diamine 4,4'-diaminodiphenylsulfone (DDS) is one of the most widely employed matrices for the production of high performance fiber composites in the aircraft and spacecraft industries [8]. Carbon nanofibers with extremely high aspect ratios combined with low density possess high electrical conductivity. They are excellent nanofiller materials for transforming electrically non-conducting polymers into conductive materials which have a wide range of applications, namely in electromagnetic interference (EMI) shielding (which has become a critical issue in the last several years with the development and advancement of electrical devices), photovoltaic devices, transparent conductive coatings as well as electro-actuating the shape memory polymer composites [9][10][11][12][13][14][15][16][17][18] and others [19][20][21]. Therefore, they are highly sought-after candidate materials to replace traditional metallic materials for lightning strike protection of aircrafts. Modern aircrafts are made of advanced composite materials, which are significantly less conductive than aluminum. Lightning is initiated at the airplane's leading edges, which ionize, creating a strike opportunity. Lightning currents travel along the airplane and exit to the ...

Nanocomposites conductivity point measurement using Tunneling AFM (TUNA)

“…They were obtained by heat treatment at 2500°C starting from the as-received CNFs. The thermal treatment was found effective in providing the best combination of mechanical and electrical properties [3,14]. The epoxy matrix was prepared by mixing an epoxy precursor TGMDA (epoxy equivalent weight 117-133 g/eq) with a reactive diluent 1-4 butanediol diglycidyl ether (BDE).…”

“…Polymer composites reinforced with carbon nanofibers (CNFs) have paved the way for new and exciting scenarios for multifunctional materials. In fact, carbon nanofibers are increasingly playing a leading role in the aeronautic field because they act as exceptional filler constituents providing overall improvement in mechanical, electrical, thermal properties and ease of processability of the polymer matrix material [1][2][3][4]. In particular, the low manufacturing cost and the remarkable electrical and thermal properties of CNFs offer the possibility to effectively transfer the CNF intrinsic properties to the epoxy composites, thus determining the improvement of the final performance that goes beyond that provided by the individual nanoparticles, without sacrificing light weight.…”

“…In fact, this paper focus on electrical characterization at nanoscale level using Tunneling AFM (TUNA), which is able to detect ultra-low currents ranging from 80 fA to 120 pA [13], as innovative tool for correlating the local topography with electrical properties of CNF/epoxy nanocomposites specifically designed to meet pressing industrial requirements in the field of structural materials. TUNA has proven to be a very effective means of investigation to identify conductive pathways and interconnections in CNF/resins, without undergoing the sample to any prior treatment with silver paint, which is usually employed to create electrical contacts to the ground [3]. In this work, Dynamic Mechanical Analysis (DMA) was used to analyze the effect of carbon nanofiber on the storage moduli and the loss factors (tan) of the developed nanocomposites.…”

Computation of mechanical, thermal and electrical properties of CNT/polymer multifunctional nanocomposites using numerical and analytical models

“…For example, a multifunctional material could be a load-bearing material with excellent thermal and electrical properties providing the structure enhanced resistance to lighting strike and great shielding effectiveness against electromagnetic interference [1]. Nanocomposites (polymers filled by carbon nanotubes (CNTs)) could achieve all these functions due to their excellent mechanical [2][3][4][5][6], thermal [7][8][9] and electrical [10][11][12][13][14][15][16] assigned by the CNTs.…”

“…Early experimental studies [6,[7][8][9][10][11][12][13] have revealed that the properties of CNT/polymer nanocomposites are governed by several material parameters and processing factors and in some cases might be contradictory. Therefore, the development of multifunctional nanocomposites must undergo a proper design and optimization phase which can be performed either by repeated manufacturing trials and physical testing or by virtual testing.…”