Optimization of Electrical, Dielectric, and Electromagnetic Response in Nanocomposite Foam by Balancing Carbon Nanotube Restricted Orientation and Selective Distribution

Abstract

In nanocomposite foams, one-dimensional (1D) carbon nanotubes (CNTs) with large length-to-diameter (L/D) ratios are selectively distributed in two-dimensional (2D) cell walls, featured as restricted distribution state of limiting in the cell-wall thickness direction and orienting in the cell-wall stretching direction. Such a unique CNT distribution state in nanocomposite foam significantly affects the degree of interface polarization for CNTs, conductive network construction, and electromagnetic (EM) wave interaction, hence determining the dielectric, conductive, and EM absorbing performance of the foams. Based on experiment and simulation results, the underlying synergistic interaction between CNTs and cells in nanocomposite foam is uncovered: (1) CNTs selectively distributed in polymer matrix isolated by cells (that is, the cell wall), and, hence, better dielectric, conductive, and EM absorbing performance were obtained at lower CNT volume content; (2) the 1D structure of CNTs is favorable for contacting with each other, but also leads to restricted orientation in the 2D cell walls (hence, there is an optimum CNT distribution in nanocomposite foam to optimize the corresponding performance). It was observed that larger CNT L/D ratios, easier to construct response networks, but larger CNTs restrict the degree to which the corresponding network construction is suppressed in cell walls. This optimum L/D ratio shifts to lower values as the CNT volume content in nanocomposite foam increases. Therefore, an appropriate cellular structure, CNT L/D ratio, and volume content are the prerequisites to maximize the advantages of CNT selective distribution and an easy-to-contact 1D structure, and to minimize the disadvantage of cell-wall-restricted CNT distribution, to construct optimum dielectric, conductive, and EM-absorbing networks for better corresponding performance.

Two-dimensional MXene nanosheets on nano-scale fibrils in hierarchical porous structure to achieve ultra-high sensitivity

“…The obtained plate sample was then processed in a high-pressure autoclave connected with an ISCO high-pressure control pump (260D, USA) via scCO 2 foaming. [52][53][54][55] The hierarchical nanoscale skeleton was then obtained by foaming at 177 °C and 15 MPa, saturated for 3 h followed by a rapid depressurization. 56…”

Sustainable polyester vitrimer capable of fast self-healing and multiple shape-programming via efficient synthesis and configuration processing

“…This is because their molecular chains experience serious stretching during the foaming process, leading to the orientation of the chains. 34,35 Therefore, the molecular chains disorientate, and the foam materials shrink before selfhealing when the molecular chain segments are available to move. 9,36 Alternatively, despite the prominent sustainability of foams, it is difficult to obtain vitrimer foam given that the strong melt strength restricts cell growth.…”

Determination of electromagnetic traveling path in polymer/multi‐walled carbon nanotube nanocomposite foams and analysis by Taguchi technique

“…Fabrication cellular structure inside the CPCs which was constructed by foaming process, could induce multi-scattering of EM radiation which is penetrated in shield. 19 This phenomenon could dissipate microwave energy in the shield because EM wave reflected and scattered numerous times into cellular structure of nanocomposite foams, as well as the EM wave traveling path into the shield were prolonged. 20 Furthermore, the introduction of microcellular structure could optimize impedance match which permits EM beam penetrates into the shield, therefore absorption mechanism is dominant mechanism compared to reflection.…”

“…The introducing of porous structure is a vital solution to overcome this problem. Fabrication cellular structure inside the CPCs which was constructed by foaming process, could induce multi‐scattering of EM radiation which is penetrated in shield 19 . This phenomenon could dissipate microwave energy in the shield because EM wave reflected and scattered numerous times into cellular structure of nanocomposite foams, as well as the EM wave traveling path into the shield were prolonged 20 .…”