Foam flows in turbulent liquid exfoliation of layered materials and implications for graphene production and inline characterisation

Sustainable Upcycling of Spent Electric Vehicle Anodes into Solution-Processable Graphene Nanomaterials

“…For a similar high-shear stirred vessel in this work, only with larger process volumes of up to ∼1 L, Pérez-Álvarez et al showed that few-layer graphene concentration follows the scaling relationship , above the critical exfoliation criteria. 19 Applying this scaling, we estimate an upcycling production rate of ∼5 g/h with a process volume of V = 3 L. This is only 1% of the volume required by high-shear mixing in batch operation, indicating that high-shear upcycling of spent graphite anodes is a promising and environmentally sustainable approach.…”

“…The dispersion was subjected to high-shear exfoliation using a cylindrical stirred vessel with diameter 70 mm, height 95 mm, and a contoured base (Figure ). A four-bladed impeller with diameter D = 55 mm was rotated at a speed of ω = 20 000 ± 1500 rpm (350W, Kenwood BLP31), resulting in turbulent flow inside the vessel ( Re = ρωD 2 /μ ≈ 10 6 ) and shear rates of γ̇ ≈ 10 5 s –1 . This rotational speed was chosen to operate above the critical criterion required to exfoliate few-layer graphene from graphite flakes, γ̇ ≈ 10 4 s –1 …”

“…A four-bladed impeller with diameter D = 55 mm was rotated at a speed of ω = 20 000 ± 1500 rpm (350W, Kenwood BLP31), resulting in turbulent flow inside the vessel ( Re = ρωD 2 /μ ≈ 10 6 ) and shear rates of s –1 . 19 This rotational speed was chosen to operate above the critical criterion required to exfoliate few-layer graphene from graphite flakes, s –1 . 7 …”

Sustainable up-cycling of spent electric vehicle anodes into solution processable graphene nanomaterials

“…For a similar high-shear stirred vessel to this work, only with larger process volumes up to ≈ 1 L, Pérez-Álvarez et al showed that few-layer graphene concentration follows the scaling relationship, C gr ∼ γ ∼ ω 3/2 V −1/2 , above the critical exfoliation criteria. 17 Applying this scaling, we estimate an up-cycling production rate of ≈ 5 g/hr with a process volume of V = 3 L. This is only 1% of the volume required by highshear mixing in batch operation, indicating that high-shear up-cycling of spent graphite anodes is a promising and environmentally sustainable approach.…”

“…The occurrence of a single peak in concentration can also be seen in previous studies on liquid exfoliation of graphite in aqueous-surfactant solutions using sonication 20 and high-shear exfoliation. 17,26 Recently, using WS 2 as a model system, Griffin et al showed that a fall-off in nanosheet concentration occurs at ∼ 10mM for all ionic surfactants. 27 The authors measured reductions in ionic conductivity of the aqueoussurfactant dispersions in this region and hypothesised this behaviour to be due to electrostatic screening.…”