Yazar "Green, Micah J." seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim
    Öğe
    Interparticle interactions and rheological signatures of Ti3C2Tz MXene dispersions
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2022) Tezel, Güler Bengüsu; Arole, Kailash; Holta, Dustin E.; Radovic, Miladin; Green, Micah J.
    Hypothesis: We hypothesize that dispersed Ti3C2Tz 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. Experiments: Small oscillatory shear tests were performed for dilute Ti3C2Tz MXene aqueous dispersions as a function of their concentration and temperature. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), f potential measurements, Dynamic Light Scattering (DLS) were used to characterize the Ti3C2Tz MXene nanoparticles. Findings: Ti3C2Tz 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 Ti3C2Tz dispersions, aggregation, and clustering can have dramatic consequences for dispersion rheology, including gelation, as the sample transitions from liquid-like to solid-like behavior.
  • Küçük Resim
    Öğe
    Kinetics of carbon nanotube-loaded epoxy curing: rheometry, differential scanning calorimetry, and radio frequency heating
    (Elsevier, 2021) Tezel, Güler Bengüsu; Sarmah, Anubhav; Desai, Suchi; Vashisth, Aniruddh; Green, Micah J.
    The isothermal curing kinetics of carbon nanotube loaded epoxy was investigated using rheometry and differential scanning calorimetry (DSC) at a range of temperatures. Rheo-kinetics was used to observe time-dependent rheological changes in elastic (G?) and viscous (G?) moduli, and complex viscosities of epoxy-CNT samples during isothermal curing. DSC measurements were also performed to monitor the curing reaction, in order to compare against the rheo-kinetic parameters. The Kamal-Sourour kinetic model describes the curing of the epoxy-CNT system for rheo-kinetics and DSC well. The activation energies of the curing reaction were found to be ?36 kJ/mol and ?33 kJ/mol using rheo-kinetics analysis and DSC, respectively. In addition, radio-frequency (RF) electromagnetic fields were used to heat and cure the epoxy-CNT sample; such heating techniques are valuable in a number of epoxy processing technologies. G?, G?, and complex viscosities of RF heated samples were measured to monitor RF-aided curing. This allows us to monitor the curing kinetics inside samples being heated by RF fields; the data indicate that RF-aiding curing is faster than curing rates for samples undergoing curing inside a measurement device such as a rheometer or DSC, because the heat generated is immediate and volumetric.