Less constrained by bandwidth limitations and sampling scarcity, broadband profiling in a wide temperature range, starting at the cryogenic threshold at −150 °C and extending to 200 °C, can be used to derive parameters of minimal variance for the Jonscher power law for ionic conductivity; these are employed to model the superionic regime over elevated temperatures and frequencies beyond the limits accessed by contemporary electrochemical impedance spectroscopy (EIS) equipment. We apply this technique to non-stoichiometric NaSICON based on the canonical NZSP formula with 5% excess sodium, synthesized by an augmented solid-state reaction (SSR) method. We thoroughly analyze broadband conductivity, dielectric permittivity, and electric modulus data over the extended temperature range. Activation energy anomalies and scaling distortions inherent to the Arrhenius approximation are investigated, and an alternative formulation based on linearized difference equations is proposed to remedy these issues. With Cole–Cole analysis establishing non-Debye relaxation behavior, dissipation analysis is employed to identify relaxation bands, used for extracting initial condition parameters for the Jonscher power law. Finally, simulations of the AC dispersion region at high temperatures and frequencies suggest the dominance of polaron tunneling mechanisms instead of the classical ion hopping mechanism assumed for NaSICON, in line with the latest insights on superionic conduction.
Attempting a thorough investigation of polyimide pyrolysis via CO2 lasers, we revisit the Laser-Induced Graphene (LIG) method, and determine the optimal operating window for producing pyrolytic nanocarbons. We design an experimental investigation that targets the full parameter space of available laser operating parameters: laser power, scan rate, and step interval. This allows us to produce different morphic groups of nanocarbons with properties depending on their surface morphology by directly controlling surface patterning. We further establish that the base material comprises a network of vertically aligned graphene channels, hereby referred to as graphene foam, thus readdressing the classification of Multi-Layer Graphene (MLG) given in previous research. We show how the laser pyrolysis method can be adapted for the production of carbon nanotubes (CNTs) via repeated pyrolysis of the starting graphene foam over high laser fluence levels. We characterize the pyrolytic nanocarbons via optical and scanning electron microscopy, Raman and UV–vis spectroscopy, surface tension measurements, and thermogravimetric analysis.
Results in Surfaces and Interfaces is an open-access journal that serves as a platform for the community interested in the fundamental aspects of chemistry and physics occurring at surfaces, interfaces and thin films of solid materials. The understanding of elementary processes at surfaces and interfaces is key to supporting the most advanced technology that will lead into a more successful and sustainable society, and that is why this knowledge must be open to everyone.
Hybrid Advances is an international and interdisciplinary scholarly open access journal devoted to the advancement in design and application of Hybrid Materials and Technologies.