▎ 摘　　要

In this study we have investigated the feasibility of preparing high concentration graphene slurries and their rheological properties as a function of various parameters including the sonicating time, solid loading, surfactant concentration, different types of graphene, aqueous and non-aqueous solvents. The feasibility of micro-extruding slurries with high graphene loading has also been studied. We demonstrate that slurries with graphene loading at 13 wt% (equivalent to 6.3 vol%) can be prepared to have pseudoplastic (shear thinning) properties. The 6.3 vol% graphene is the highest graphene loading ever reported in the open literature. An unusual phenomenon of increasing graphene loading leading to reduced viscosity after graphene loading has reached a critical value has been observed for the first time. This unusual phenomenon is attributed to the forced alignment of graphene flakes during shearing when graphene loading is high enough and has been utilized to prepare slurries with high graphene loading and pseudoplastic properties. Micro-extrusion of these high concentration graphene slurries reveals the capability of the extrudate to maintain its shape right after extrusion of the slurries. Thus, it is expected that these high concentration graphene slurries can be used to fabricate three-dimensional objects through layer-by-layer fabrication methods with high fabrication rates in the near future. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.