3 of 25) 1601625 wileyonlinelibrary.com Adv. Energy Mater. 2017, 7, 1601625 www.advenergymat.de www.advancedsciencenews.com Figure 1. Comparison of the a) inorganic and b) organic carbon sources on the performance of carbon coated Li 4 Ti 5 O 12 .
Flexible polypyrrole (PPy) films with highly ordered structures were fabricated by a novel vapor phase polymerization (VPP) process and used as the anode material in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The PPy films demonstrate excellent rate performance and cycling stability. At a charge/discharge rate of 1 C, the reversible capacities of the PPy film anode reach 284.9 and 177.4 mAh g in LIBs and SIBs, respectively. Even at a charge/discharge rate of 20 C, the reversible capacity of the PPy film anode retains 54.0% and 52.9% of the capacity of 1 C in LIBs and SIBs, respectively. After 1000 electrochemical cycles at a rate of 10 C, there is no obvious capacity fading. The molecular structure and electrochemical behaviors of Li- and Na-ion doping and dedoping in the PPy films are investigated by XPS and ex situ XRD. It is believed that the PPy film electrodes in the overoxidized state can be reversibly charged and discharged through the doping and dedoping of lithium or sodium ions. Because of the self-adaptation of the doped ions, the ordered pyrrolic chain structure can realize a fast charge/discharge process. This result may substantially contribute to the progress of research into flexible polymer electrodes in various types of batteries.
The mini-slump test is a fast, inexpensive and widely adopted method for evaluating the workability of fresh cementitious pastes. However, this method lacks a standardised procedure for its experimental implementation, which is crucial to guarantee reproducibility and reliability of the test results. This study investigates and proposes a guideline procedure for mini-slump testing, focusing on the influence of key experimental (mixing and testing) parameters on the statistical performance of the results. The importance of preparation of always testing at the same time after mixing, testing each batch once rather than conducting multiple tests on a single batch of material, is highlighted. A set of alkali-activated fly ash-slag pastes, spanning from 1 to 75 Pa yield stresses, were used to validate the test method, by comparison of calculated yield stresses with the results obtained using a conventional vane viscometer. The proposed experimental procedure for mini-slump testing produces highly reproducible results, and the yield stress calculated from mini-slump values correlate very well with those measured by viscometer, in the case of fresh paste of pure shear flow. Mini-slump testing is a reliable method that can be utilised for the assessment of workability of cements.
Articles you may be interested inEnhanced magnetism and ferroelectricity in epitaxial Pb(Zr0.52Ti0.48)O3/CoFe2O4/La0.7Sr0.3MnO3 multiferroic heterostructures grown using dual-laser ablation technique Adjustable magnetoelectric effect of self-assembled vertical multiferroic nanocomposite films by the in-plane misfit strain and ferromagnetic volume fractionThe morphology and structure of interfaces in PbTiO 3 -CoFe 2 O 4 films on SrTiO 3 substrates of various orientations are studied. It is found that for film with thickness more than 100 nm with columnar two-phase morphology, the average orientations of the interfaces between the phases reside on the ͕110͖, ͕111͖, and ͕112͖ planes for films normal to substrates oriented along ͗001͘, ͗110͘, and ͗111͘ correspondingly. These macroscopic interfaces consist of ͕111͖ nanofacets. The study of very thin film less than 30 nm shows that the interfaces between nanosize phases are ͕111͖ planes. Available theoretical results on morphology of multiferroic thin film nanostructure allow us to conclude that for thick films ͑Ͼ100 nm͒, two-phase columnar morphology ͑shape of constituent phases, their arrangement, and average crystallographic orientations of the interfaces͒ is essentially determined by the trend for minimization of elastic energy, while the trend to minimize the energy of interfaces results in faceting interfaces along the ͕111͖ planes. Possibility of long range ordering in phase arrangement is discussed.
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