Intercalated films

Further Developments Break-up of Suspended, Supported and Intercalated Films. There is a whole family of closely related problems, ranging from (i) the bursting of soap films suspended in the air (see Fig. 1.29), studied by Mysels, K. through the intermediate case of (ii) films supported on a liquid or solid and exposed to the air to that of (iii) films intercalated between a solid and a soft material (rubber). 

In the case (m) of intercalated films, the rim must distort the soft material around it. Consequently, it becomes rather flattened and viscous dissipation still predominates. It is no longer localised only in the wedge fronts, but occurs throughout the volume. It increases with the size of the rim, whereas the driving force 5 remains constant the dewetting speed thus decreases in time. Experiments on intercalated Aims are currently underway at the Institut Curie in Prance (Martin). 

In the case of intercalated films, consider the example of the lachrymal film between the cornea and a contact lense. Dewetting would lead to adhesion between the lense and the cornea, which would be catastrophic. Another example is hydroplaning on wet roads if we brake, the car cannot slow down unless the water film, which plays the role of a lubricant, has time to dewet. 

Krikorian and Pochan [37] explored the effect of compatibility of different organic modifiers on the overall extent of dispersion of layered silicate layers in a PLA matrix. Three different types of commercially available organoclays were used as a reinforcement phase. Nanocomposites were prepared by using the solution intercalation film casting technique. 

Veszelei M., Kullman L., Azens A., Granqvist C., Rjbrvasson B. Transparent ion intercalation films of Zr-Ce oxide. J. Appl. Phys. 1997 81(4) 2024-2026... 

OMLS were used as a reinforcement phase. Nanocomposites were prepared by using the solution-intercalation film-casting technique. For each composition, 100 mg of PLA was dissolved in 10 mL of dichloromethane. OMLS dispersions (<0.1wt.%) were obtained by suspension of well-dried OMLS in a separate beaker of dichloromethane. Both the PLA solution and OMLS suspension were sonicated separately for 30 min at room temperature. The final mixture was further sonicated for 30 min. The mixture was then cast on a glass surface and kept in a desiccator for controlled evaporation of the solvent over 2 days. 

Moleculady mixed composites of montmorillonite clay and polyimide which have a higher resistance to gas permeation and a lower coefficient of thermal expansion than ordinary polyimides have been produced (60). These polyimide hybrids were synthesized using montmorillonite intercalated with the ammonium salt of dodecylamine. When polymerized in the presence of dimethyl acetamide and polyamic acid, the resulting dispersion was cast onto glass plates and cured. The cured films were as transparent as polyimide. 

Numerous research activities have focused on the improvement of the protective films and the suppression of solvent cointercalation. Beside ethylene carbonate, significant improvements have been achieved with other film-forming electrolyte components such as C02 [156, 169-177], N20 [170, 177], S02 [155, 169, 177-179], S/ [170, 177, 180, 181], ethyl propyl carbonate [182], ethyl methyl carbonate [183, 184], and other asymmetric alkyl methyl carbonates [185], vinylpropylene carbonate [186], ethylene sulfite [187], S,S-dialkyl dithiocarbonates [188], vinylene carbonate [189], and chloroethylene carbonate [190-194] (which evolves C02 during reduction [195]). In many cases the suppression of solvent co-intercalation is due to the fact that the electrolyte components form effective SEI films already at potential which are positive relative to the potentials of solvent co-intercalation. An excess of DMC or DEC in the electrolyte inhibits PC co-intercalation into graphite, too [183]. 

Graphitic anodes which have been "prefilmed" in an electrolyte "A" containing effective film-forming components before they are used in a different electrolyte "B" with less effective film-forming properties show lower irreversible charge losses and/or a decreased tendency to solvent co-intercalation [155, 201, 202], However, sufficient insolubility of the pre-formed films in the electrolyte "B" is required to ascertain long-term operation of the anode. 

Using dilatometry in parallel with cyclic voltammetry (CV) measurements in lmolL 1 LiC104 EC-l,2-dimethoxy-ethane (DME), Besenhard et al. [87] found that over the voltage range of about 0.8-0.3 V (vs. Li/Li+), the HOPG crystal expands by up to 150 percent. Some of this expansion seems to be reversible, as up to 50 percent contraction due to partial deintercalation of solvated lithium cations was observed on the return step of the CV. It was concluded [87] that film formation occurs via chemical reduction of a solvated graphite intercalation compound (GIC) and that the permselective film (SEI) in fact penetrates into the bulk of the HOPG. It is important to repeat the tests conducted by Besenhard et al. [87] in other EC-based electrolytes in order to determine the severity of this phenomenon. 

Carbon dioxide as additive improves the behavior of (Li02C0CH2)2 films formed above intercalation potentials in EC/DEC-based electrolytes due to increased formation of Li 2 CO 3 [200], It is interesting to note that SO2 reduction occurs at quite high potentials, before the reduction of other electrolyte components films contain inorganic and organic lithium salts [201]. 

These tactoids are responsible for the particular geometrical structures formation in the blends, which leads to the formation of superstructures in the thickness of the blended film. The Young s modulus of the hybrid is increased by this kind of structural feature. After that, the preparation of intercalated PLA/ OMMT nano-composites with much improved mechanical and thermal properties was reported by Bandyopadhyay et al. (1999). 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

Later electrochemical smdies on sputtered, amorphous MoOyS films showed that the Li intercalation process strongly depends on the composition of these films... 

In specific, it was found that up to 3.5 mole lithium per mole molybdenum can be intercalated in films with high oxygen content and 1.7 in the others. The Li diffusion coefficient was found equal to 10 cm s at the beginning of the intercalation. It was noted that intercalation of the first Li is never reversible. 

Further, tungsten oxysulfide films, WOyS, have shown promising behavior as positive electrodes in microbatteries, unlike WS2 that is not suitable as cathode in lithium cells. Using amorphous thin films of WO1.05S2 and WO1.35S2.2 in the cell Li/LiAsFe, 1 M ethyl-methyl sulfone (EMS)/W03,Sz, Martin-Litas et al. [80] obtained current densities up to 37 xA cm between 1.6 and 3 V. In these cathode materials, 0.6 and 0.8 lithium per formula unit, respectively, could be intercalated and de-intercalated reversibly. 

Castro RJ, Cabrera CR (1997) Photovoltammetry and surface analysis of MoSea thin films prepared by an intercalation-exfoliation method. J Electrochem Soc 144 3135-3140... 

Kanehori K, Matsumoto K, Miyauchi K, Kudo T (1983) Thin film solid electrolyte and its application to secondary Lithium cell. Solid State Ionics 9-10 1445-1448 Py MA, Haering RR (1983) Structural destabilization induced by lithium intercalation in M0S2 and related compounds. Can J Phys 61 76-84... 

Levi E, Lancry E, Gofer Y, Aurbach D (2006) The crystal structure of the inorganic surface films formed on Mg and Li intercalation compounds and the electrode performance. J Solid State Electrochem (2006) 10 176-184... 

Thin self-supporting clay films (appropriate for IR measurement) readily take up organic amines such as cyclohexylamine with displacement of the major fraction of the intercalated water. For the Ua -exchanged sample the majority of the amine is present in the unprotonated form - there being insufficient Bronsted acidity generated by the interlayer cation. When Al + is the exchangeable cation, however, a major fraction of the intercalated amine becomes protonated (see Figure 2). 

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