To bridge the gap between laboratory-scale studies and commercial applications, mass production of high quality graphene is essential. A scalable exfoliation strategy towards the production of graphene sheets is presented that has excellent yield (ca. 75 %, 1-3 layers), low defect density (a C/O ratio of 21.2), great solution-processability, and outstanding electronic properties (a hole mobility of 430 cm V s ). By applying alternating currents, dual exfoliation at both graphite electrodes enables a high production rate exceeding 20 g h in laboratory tests. As a cathode material for lithium storage, graphene-wrapped LiFePO particles deliver a high capacity of 167 mAh g at 1 C rate after 500 cycles.
A compact scanning Michelson interferometer for the measurement of both the concentration and temperature derivative of the refractive index of liquids, liquid mixtures, and solutions has been developed. Scanning of one of the mirrors allows the extraction of the phase information and makes the instrument insensitive to intensity drifts of the light source. The refractive index noise level of the empty instrument is of the order of 10−8 for a 10 mm sample cell, and for continuously varying refractive indices there is no upper limit of the linear detection range. Accuracies of the order of 0.5% can be achieved both for (n/c)p,T and (n/T)p,c.
Oxygen permeabilities of different polymers were determined by using two different methods based on quenching of an excited phosphorescent dye by oxygen. In the first method, the phosphorescent dye platinum octaethylporphyrin is directly dissolved in the polymer film of interest whereas in the second method a sensor film is used which is separated from the film of interest by a spacer. The polymers investigated are PMMA, PVC, PVAc, cellulose acetate, PEMA, and PS. The resulting oxygen permeability coefficients are compared with data reported in the literature. It was found that oxygen permeation strongly depends on the protocol of preparation and thermal history of the films.magnified image
We have developed a highly sensitive, multi‐angle, static light scattering (TRSLS = time resolved static light scattering) instrument, which measures the angular dependent Rayleigh scattering intensity of solutions simultaneously at 38 angles within approximately one second. It is thus suitable as a quick and easy to use static light scattering device for routine polymer and colloid characterization. The time resolution allows the kinetics of many systems to be investigated down to a second time scale, such as polymerization kinetics of linear, branched and crosslinked polymer structures, thermoreversible gelation, growth of colloidal particles, structural changes in micellar systems, etc.
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