|Description||2018 Fall Graduate Colloquium Series|
Core-Shell Structured Semiconducting Poly(diphenylamine)-Coated Polystyrene Microspheres and their Electrorheology
To fabricate a novel type microsphere-based ER(Electrorheology) material, the authors apply the core-shell-coat technology to coat the PDPA(poly diphenylamine), as an electro-response layer, onto PS (polystyrene) particles with a controlled size and morphology. By using scanning electron microscopy and transmission electron microscopy, the morphological analysis could be performed. The chemical composition and thermal stability of the particles are investigated by Fourier-transform under infrared spectroscopy and thermogravimetric analysis, respectively. The rheological properties of the PS/PDPA-based ER fluid are measured via both steady shear and dynamic oscillation tests performed under different electric field strengths. Other characterizations, like electrical polarization property and flow behavior to electric fields of the PS/PDPA-based ER fluid, are performed by using an LCR meter. These measurements provide additional information to support its ER performance, which is confirmed with a conduction model with a slope of 1.5.
Reference: Min Hwan Kin, Hyound Jin Choi. Core-shell structured semiconducting poly(diphenylamine)-coated polystyrene microspheres and their electrorheology. Polymer:2017,120-131.
Thermoacoustic Instability in Two-Dimensional
Fluid Complex Plasmas
For the first time the thermo acoustic instability has been studied in complex plasma. Nonreciprocal effective interactions between particles, mediated by plasma flows, give positive thermal feedback and this will lead to acoustic sound amplifications. Sound spectra generated by experiments and simulations perfectly matches the theory and this justifies thermoacoustic instability in fluid plasma. The results of this research show the similarities between collective fluctuation dynamics in reactive media and systems with nonreciprocal effective interactions.
Reference: Nikita P. Kryuchkov, Egor V. Yakovlev, Evgeny A. Gorbunov, Lenaic Couëdel, Andrey M. Lipaev, and Stanislav O. Yurchenko, “Thermoacoustic Instability in Two-Dimensional Fluid Complex Plasmas”, Phys. Rev. Lett. 121, 075003 (2018)
For more information contact: Dr. Howard Lee 254-710-2277