PDF Publication Title:
Text from PDF Page: 133
Chapter 5 β Production of Few Layer Graphene in Organic Solvents of bath water at prolonged sonication times; as increased solvent temperature could affect the sonication process. The graphite/organic solvent mixture was sonicated in the round-bottomed flask for 60 hr. Aliquots were taken at different times, left overnight for sedimentation, followed by centrifugation (20 min) at different speeds. Figure 5.1a shows photographs of the graphene obtained in the NMP. The dispersions produced using a longer sonication times appear darker at a given centrifugation speed indicating higher graphene concentration. The quantitative information on the yield (or concentration) of graphene can be estimated using UV-Vis spectroscopy and applying the Lambert-Beer law: π΄ = πΌππ, where π΄ is the absorbance, π (m-1) is the optical path length, π (mg/ml) is concentration and πΌ (ml mg-1 m-1) is absorption coefficient. πΌ was experimentally determined by vacuum filtering a known volume of dispersions and measuring the resulting film in a microbalance, as explained in section 4.1.2.3. The value of πΌ = 4632 mL mg-1 m-1 was obtained for solvent exfoliation. Additionally, value of πΌ = 1825 mL mg-1 m-1 was obtained for TDOC-based exfoliation (see section 4.1.2.4). It should be noted that the different values for πΌ have been reported in literature54, 59, 60, 69, 77 ranging from 1390 to 6600 mL mg-1 m-1 in various solvents and surfactant-based dispersions, and this variation is not clearly understood. In general the πΌ is constant and assumed to be characteristic material property, however, such variation in the observed and the reported values could probably relate to different surface and layer properties of the material.347, 348 A study conducted by Su et al. on rGO with varying lateral dimensions, mean number of flakes and functional groups, revealed dispersions with smaller flakes (lateral dimension) and less layer per flake had lower πΌ, attributed to shrinkage of the π-conjugated systems.349 Therefore, to avoid any uncertainty, calculated πΌ values of 4632 mL mg-1 m-1 and 1825 mL mg-1 m-1 for organic solvent and aqueous surfactant-based dispersions, respectively, were used in this thesis. The UV-Vis spectra of FLG/NMP and FLG/DMF show characteristic featureless absorption as shown in Figure 5.1b. Unknown concentrations were calculated using the π΄ value at 660 nm. 133PDF Image | PRODUCTION AND APPLICATIONS OF GRAPHENE AND ITS COMPOSITES
PDF Search Title:
PRODUCTION AND APPLICATIONS OF GRAPHENE AND ITS COMPOSITESOriginal File Name Searched:
graphene-production-applications.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 | RSS | AMP |