Interparticle interactions and rheological signatures of Ti₃C₂T_z MXene dispersions

We hypothesize that dispersed Ti₃C₂T_z MXene particle interactions are reflected in the bulk viscoelastic properties of the dispersions and can be analyzed using classical colloidal theory for anisotropic particles. The relevant kinetic theory for Brownian anisotropic particles is given by the Doi and Edwards (D-E) Model, and the Maxwell Model is used to fit the relaxation times as a function of frequency. Such behavior is relevant to a variety of MXene processing techniques, particularly printing and coating.

Small oscillatory shear tests were performed for dilute Ti₃C₂T_z MXene aqueous dispersions as a function of their concentration and temperature. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), ζ potential measurements, Dynamic Light Scattering (DLS) were used to characterize the Ti₃C₂T_z MXene nanoparticles.

Ti₃C₂T_z dispersions show gel-like and viscous-like behavior at low and high temperatures, respectively. Experimental relaxation times fitted to the Maxwell model are found to be close to the theoretical values. However, at high temperatures, relaxation time values differ due to the inter-particle interactions, even in the dilute concentration regime. For Ti₃C₂T_z dispersions, aggregation, and clustering can have dramatic consequences for dispersion rheology, including gelation, as the sample transitions from liquid-like to solid-like behavior.