A New Perspective for Solid-to-Liquid Transition of an Inorganic Particle Structure in a Gel System Filled with Fumed Silica and Aluminum Microparticles during Stress-Controlled Oscillation

Silica-based gels are often mentioned because of their viscoelasticity, but very little work has really reflected this competing relationship between restorative and destructive properties dominated by the inorganic particle structure. Understanding the mechanical behavior of the solid-to-liquid transition is a key to be addressed in the design of gelation, while it is an attractive task to excavate the respective morphology and separate effects on the viscoelasticity of the gel structure and the viscous elasticity of the interface. In this work, gel fuels were prepared by dispersing fumed silica (FS) and aluminum microparticles (Al MPs) in a hydrocarbon fuel. The two types of particles were labeled to display different fluorescence colors, and the particulate system was studied via a vane rotor test system under a stress-controlled large-amplitude oscillatory shear (LAOStress). The results demonstrate that the viscoelastic characteristics of gel fuels based on the inorganic particle structure are mainly due to the role of fumed silica, the nanoparticles of which comprise the most important flocculating structure, and that doping of Al MPs enhances only the yield stress of the structure but reduces the viscosity and recoverability of the fuel. The energy dissipation has been demonstrated as new evidence for structural recovery and collapse, which increased dramatically at a 10% strain as the amplitude reached the yield stress. Fourier transform (FT) analysis revealed that the sample's nonlinearities were predominantly pronounced near the yield stress.