Investigation On The Determinants And Mechanism Of Electrical Percolation Of Metal Rubber

The metal rubber is flexible conductive nanocomposite materials that are dispersed in the high elastic polymer matrix.The excellent properties of this material exhibited both the high elasticity and the high electrical conductivity also make it have a broad potentially applications.At the same time,the metal rubber play an indispensable role in the development of flexible electronic or optoelectronic products.What different from the traditional conductive phase is that the more substantial surface effects and quantum mechanical effects of the spherical nanoparticles enable a small amount of spherical nanoconductors to autonomously form non-contact and more efficient conductive pathways in the insulating matrix while the nanocomposite retain a greater degree of the excellent properties of a highly elastic matrix.However,the study on conductive percolation properties of this kind of nanocomposite is currently limited to the experimental technique.Moreover,the conductive percolation behavior of nanocomposites constituted by the spherical conductors are also greatly different from that of other nanocomposites because the spherical conductors is significantly different from the one dimensional or two dimensional nanofibers,and,at present,there is no corresponding report to conduct more in-depth exploration and analysis of the conductive percolation behavior of this metal rubber.Therefore,considering the quantum tunneling effect and the van der Waals force into the research,the conductive percolation behavior of the metal rubber by combining the numerical simulation with the theoretical research have been studied.Firstly,Monte Carlo method is used to establish equivalent model of the metal rubber.Then the conductive percolation behavior of the nanocomposite is simulated by combining this method with the nanoscale electronic contact model and the conductive loop theory,and the influencing factors and physical mechanism of the conductive percolation are discussed.Next,an interphase reflecting the role of quantum tunneling effect was coated around the nanoparticles,and an equivalent mechanical model of "metal nanoparticles + interphase" was established.After that,the formula of equivalent conductivity of the nanoparticle-polymer composite was deduced.Based on the formula,we in-depth and completely revealed the entire process of conductive percolation of the nanocomposite.Finally,by simulations and theoretical calculations,we have obtained specific conclusions as follows:(1)Conductive percolation behavior of metal rubber is controlled by two conductive mechanism,i.e.quantum tunneling effect and conductive contact.At the stage where the tunneling effect plays a dominant role,the conductivity of the metal rubber is mainly determined by the tunneling energy barrier of the matrix while the conductivity of the metal rubber is mainly controlled by the resistivity of the nanoparticle at the stage where the conductive contact plays a dominant role.Therefore,the remarkable piezoresistive effect of the metal rubber can actually be achieved in the stage where the tunneling effect plays a dominant role.(2)The percolation threshold and the power exponent t of the metal rubber are independent of the electrical properties of the nanoparticles and the polymer,and they are completely determined by the geometric characteristics of the nanofillers.(3)The metal rubber has a two-stage conductive percolation behavior.The first surge of its conductivity is mainly the result that there happening electron transport between neighboring nanoparticles in the matrix through the electron tunneling effect and finally form a conductive circuit while the second jump is due to the change of the mechanism of electron transport between neighboring nanoparticles in the conductive circuit,i.e.,the tunneling effect translates into the conductive contact.(4)The quantum tunneling effect is greatly sensitive to the size of nanoparticles.When the nanoparticle radius exceeds 195 nm,the tunneling effect on percolation process of the metal rubber have disappeared,and the two-stage percolation behavior of the nanocomposite have transformed the traditional one-stage percolation behavior.