How to improve the efficiency of liquid-phase shear exfoliation(LPSE)for mass production of large-size graphene nanosheets still remains an ongoing challenge.In this work,we have developed a LPSE method using a rotor-...How to improve the efficiency of liquid-phase shear exfoliation(LPSE)for mass production of large-size graphene nanosheets still remains an ongoing challenge.In this work,we have developed a LPSE method using a rotor-stator mixer.It is quite simple and efficient by exfoliation of expanded graphite(EG)in Nmethyl-2-pyrrolidone(NMP)with the assistance of organic salts including sodium citrate,potassium citrate and sodium tartrate.The LPSE of EG in NMP can provide improved yields,up to 6 times as high as values from exfoliation of natural flake graphite(NFG).The additive of organic salts in NMP can make a further improvement in graphene yields,1.5 times higher than that obtained only in NMP.Remarkably,the yields of the as-exfoliated graphene are as high as 10%under optimal conditions,and up to 50%after multiple-cycle exfoliation.Organic salts in LPSE act as analogue grinding aids enhancing the applied shear forces and thus contributing to the improved efficiency of LPSE,but they do not intercalate into the interplanar spaces of graphite.This facile LPSE method should have excellent potential in the large scale production of graphene nanosheets for numerous applications.展开更多
A liquid-assisted shear exfoliation (LASE) as a new powder metallurgy method coupled with spark plasmasintering (SPS) was applied for n-type Bi_(2)Te_(2.7)Se_(0.3) and the effects on microstructure and anisotropictran...A liquid-assisted shear exfoliation (LASE) as a new powder metallurgy method coupled with spark plasmasintering (SPS) was applied for n-type Bi_(2)Te_(2.7)Se_(0.3) and the effects on microstructure and anisotropictransport properties were investigated. Results revealed an effective reduction of average grain size dueto LASE and a high texturing in the bulks. Moreover, along the in-plane direction, electrical conductivitywas increased noticeably due to an enhanced carrier concentration, leading to a significantly improvedpower factor of 25 μW cm^(–1) K^(–2) at 303 K. Meanwhile, the total thermal conductivity was reduced effectively owing to reduction both in lattice component due to enhanced phonon scattering with the grainsize reduction, and in the bipolar component inhibited by the increased carrier concentration. Ultimately,a peak thermoelectric figure of merit (ZT) value of 0.83 was obtained at 448 K along the in-plane direction, increased by 95% compared with the pristine one. These results demonstrate the LASE process as auseful assistant method for enhancing the TE performance of layered materials.展开更多
基金The authors would like to thank the financial support from the National Natural Science Foundation of China(51902173)China Postdoctoral Science Foundation(2019T120084,2018M640123).
文摘How to improve the efficiency of liquid-phase shear exfoliation(LPSE)for mass production of large-size graphene nanosheets still remains an ongoing challenge.In this work,we have developed a LPSE method using a rotor-stator mixer.It is quite simple and efficient by exfoliation of expanded graphite(EG)in Nmethyl-2-pyrrolidone(NMP)with the assistance of organic salts including sodium citrate,potassium citrate and sodium tartrate.The LPSE of EG in NMP can provide improved yields,up to 6 times as high as values from exfoliation of natural flake graphite(NFG).The additive of organic salts in NMP can make a further improvement in graphene yields,1.5 times higher than that obtained only in NMP.Remarkably,the yields of the as-exfoliated graphene are as high as 10%under optimal conditions,and up to 50%after multiple-cycle exfoliation.Organic salts in LPSE act as analogue grinding aids enhancing the applied shear forces and thus contributing to the improved efficiency of LPSE,but they do not intercalate into the interplanar spaces of graphite.This facile LPSE method should have excellent potential in the large scale production of graphene nanosheets for numerous applications.
基金This work was financially supported by the National Natural Science Foundation of China(No.51672127)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘A liquid-assisted shear exfoliation (LASE) as a new powder metallurgy method coupled with spark plasmasintering (SPS) was applied for n-type Bi_(2)Te_(2.7)Se_(0.3) and the effects on microstructure and anisotropictransport properties were investigated. Results revealed an effective reduction of average grain size dueto LASE and a high texturing in the bulks. Moreover, along the in-plane direction, electrical conductivitywas increased noticeably due to an enhanced carrier concentration, leading to a significantly improvedpower factor of 25 μW cm^(–1) K^(–2) at 303 K. Meanwhile, the total thermal conductivity was reduced effectively owing to reduction both in lattice component due to enhanced phonon scattering with the grainsize reduction, and in the bipolar component inhibited by the increased carrier concentration. Ultimately,a peak thermoelectric figure of merit (ZT) value of 0.83 was obtained at 448 K along the in-plane direction, increased by 95% compared with the pristine one. These results demonstrate the LASE process as auseful assistant method for enhancing the TE performance of layered materials.
