RESUMO
A novel simple gas-driven exfoliation method with mild operating conditions is explored for producing graphene. The obtained graphene, with 97% of flakes being ≤2 layers and 62% mono-layers, is of high-quality and free of defects. A high sheer rate of up to 3.3 × 107 s-1 generated due to the driving of high-speed gas at a working pressure as low as 0.5 MPa is responsible for the exfoliation.
RESUMO
With the severe energy and environmental issues, lignin has received increasing attention as a renewable biomass feedstock. The development of lignin-based nanoparticles provides a new route to the valorization of lignin. In this work, we propose a simple continuous method to prepare lignin nanoparticles (LNS) using a microchannel reactor. Polyvinylpyrrolidone (PVP)/sodium dodecyl sulfate (SDS) were selected as stabilizers. Spherical-like lignin nanoparticles with an average size of 13 nm were obtained in a T-shaped microchannel reactor. The effects of solvent species, PVP/SDS mass ratio, and lignin solution flow rate on the size of LNS were investigated. The as-prepared LNS had a good stability during 60 days-storage and were used as an additive to form UV-shielding composite films with poly(vinyl alcohol) (PVA). Compared with raw lignin, the addition of LNS could enhance the UV-shielding efficacy by 13.3% in the ultraviolet spectrum (250 nm). The present work suggests that the microchannel reactor is a promising continuous approach to prepare LNS with versatile applications.
