Formation and processability of liquid crystalline dispersions of graphene oxide

Rational control over the formation and processability, and consequently final properties of graphene oxide liquid crystalline dispersions has been a long-standing goal in the development of bottom-up device fabrication processes. Here we report, the principal conditions through which such levels of control can be exercised to fine-tune dispersion properties for further processing

A significant improvement in both low- and high-field performance of MgB<inf>2</inf> superconductors through graphene oxide doping

The effects of graphene oxide (GO) doping on the superconducting properties of MgB2 were studied using bulk samples made by the diffusion method. Homogeneous dispersions of GO in tetrahydrofuran were obtained through a novel synthesis method, which is then chemically doped with MgB2. It was found that GO doping significantly improves the critical current density, under both low and high magnetic fields, which distinguishes GO from all the other elements doped into MgB2 so far. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Improvements in the Dispersion of Nanosilver in a MgB<inf>2</inf> Matrix through a Graphene Oxide Net

© 2015 American Chemical Society. The effects of graphene oxide (GO) addition on the dispersion of nanosilver (Ag) in an MgB2 matrix were studied using bulk samples prepared through a diffusion process. The influence of the dispersion of Ag and Ag/GO particles on the critical current density (Jc) of MgB2 was also investigated. GO has emerged as an excellent dopant which can significantly improve both the low- and high-field performance of MgB2 due to its capability to improve intergrain connectivity (GO) and inter- and intragrain pinning (GO and AgMg). The addition of nanosize Ag particles also results in an improvement of vortex pinning, and at the same time, it offers the advantage of preventing the loss of Mg during the sintering process. It is found that the dispersion of nanosilver in the presence of GO results in significant improvements in the critical current density in MgB2, particularly at high magnetic fields, due to improved intergrain connectivity and flux pinning. The use of the GO net as a platform for doping MgB2 in our case with Ag yielded a 10-fold-better critical current density (Jc) than standard Ag doping at 9 T and 5 K. Even without sophisticated processes, we obtained a Jc result of 104 A/cm2 at 9 T and 5 K, which is one of the best ever achieved

Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 (o)C) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB