Electrical Tortuosity in Nanostructured Mesoporous Silica Powder and Nanocomposite Membranes

Polymer silica nanocomposites are advanced materials with unique properties combining the advantages of an inorganic nanofiller and the organic polymer matrix, which attracted considerable interest for applications in energy conversion and storage, drug delivery, environmental remediation, and many more. However, the dispersion of the nanofiller in the polymer matrix leads to complexified nanocomposite materials whose barrier properties are altered resulting in a tortuous pathway for the transport of current, matter, and velocity. The tortuosity of these nanocomposite materials, which depends on their porosity organization, is a parameter usually challenging to quantify accurately. Therefore, the objective of this study was to develop a method to quantify the electrical tortuosity and to develop a theoretical model to accurately predict electrical tortuosity in these in-house prepared silica powder and nanocomposite membrane materials at different porosity ranges. The SBA-15 silica powder and nanocomposite membranes’ conductivity was measured with the help of impedance spectroscopy in a 1 M sodium chloride electrolyte solution from which the electrical tortuosity is quantified. The calculated tortuosity of SBA-15 silica powder was found to be well correlated to the entire range of its porosity. The plots of the tortuosity versus porosity from the Maxwell and the modified Maxwell models showed a well-fitted curve to the entire range of porosity. These theoretical models will help to give a perfect prediction of the electrical tortuosity of materials from porosity measurements, which would be a vital technique to characterize materials used in electrochemical devices and battery technology.