PDF Publication Title:
Text from PDF Page: 005
was obtained. However, when T is raised above 2400 °C, the original RGO sheets transformed into bulk graphite. With T about 1500 °C, functional groups on the precursor RGO sheets were apparently completely removed. The application of pres- sure during high T treatment plays a critical role in obtaining ‘high quality’ graphene sheets as a product material. Based on the molecular dynamics simulation data, XPS spectrum results, and the change of vacuum level during hot pressing (Fig. S4), the mechanism of reducing functional groups through hot-pressing could be thoroughly discussed. The above results indicated that the reaction was divided into two stages, first stage primarily is the C@O and O@CAOH bonds decomposition at 800–1500 °C. Subsequently, when the pressure was fixed at 40 MPa, the CAOH and CAOAC bonds started to be removed due to the formation of CAC and OAO bonds, which resulted in the recovery of the honey- comb structure of graphene. Field effect transistors (FETs) from pristine RGO sheets and also of the high (T, p) treated RGO sheets were fabricated on a 300 nm SiO2/Si substrate [33,34]. The schematic top views of a FET composed of RGO or of the product sheet, as the channel, with source and drain electrode, and back gate, are shown in Fig. 5a and b, respectively. Fig. 5c and d shows the current I as a function of the applied gate voltage Vg, where the conduc- tion carrier is hole for a positive Vg. The average mobility was about 1000 cm2 V1 S1 for the product (graphene) sheets (about 8· higher than the RGO precursor sheets, where the RGO sheets show a mobility of about 130 cm2 V1 S1) (Fig. 5e and f). Moreover, this value exceeds most of the RGO prepared by the chemical reduction method. High reproduc- ibility of the electrical test was verified from the columnar distribution map and the Gauss distribution curve. 4. Summary The perfectly structural integrity and gram-scale produc- tion of graphene have been physically produced using hot pressing with high temperature and moderate pressure. The process is simple and effective, meeting the industrial level requirement of graphene applications. Besides the chemical produced graphene sheets, the graphene sheets from other processes may also be treated with hot pressing for further getting a perfect and highly crystalline graphene. This process could provide a possibility to radi- cally overcome the barrier for further industrial use of graphene with low-cost in energy and composites in the future. Acknowledgements This research was supported by the National Natural Science Foundation of China (No. 11174227), National Basic Research Program of China (973 Program) (No. 2009CB939705), academic award for excellent Ph.D. candidates funded by Ministry of Education of China, and the Fundamental Research Fund for the Central Universities (2011202020003). L. Liao acknowledges the MOE NCET-10-0643 and NSFC Grant (Nos. 11104207, 91123009 and 10975109), Hubei Province Natural Science Foun- dation (2011CDB271), the Natural Science of Jiangsu Grant (No. BK2011348), as well as ‘‘The Grant of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology)’’. The authors acknowledge the helpful input of D. Zhao, Y. Ren, Q. Fu, D. Wang, Y. Liu and W. Yao. XPS measurements were carried out at the Analysis Center, Tsinghua University. AFM measurements were carried out at the School of Materials Science and Engineering, Wuhan University of Technology Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.carbon. 2012.11.012. CARBON 54 (2013) 143–148 147 Fig. 5 – The electrical properties of the RGO and the hot pressed graphene sheet transistor. (a and b) The schematic top view of the device layout. D, drain; S, source; RGO, reduced graphene oxide; TG, treated graphene by hot pressing. (c and d) Ids–Vg transfer characterize for the RGO and treated graphene transistor at Vds = 0.1 V, inset in (c) and (d) are optical images of the transistor device, the scale bar is 5 lm. The external source and drain are fabricated using electron beam lithography. (e and f) Mobility distribution maps of RGO and treated graphene.PDF Image | graphene sheets from graphene oxide by hot-pressing
PDF Search Title:
graphene sheets from graphene oxide by hot-pressingOriginal File Name Searched:
345.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Power up your energy storage game with Salgenx Salt Water Battery. With its advanced technology, the flow battery provides reliable, scalable, and sustainable energy storage for utility-scale projects. Upgrade to a Salgenx flow battery today and take control of your energy future.
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)