Intercalation Phases

Figure 4.17 Structure of the intercalation phase LixCo02 (a) packing of the oxygen layers in C0O2 before intercalation is hexagonal closest packing and (b) after intercalation the packing changes to cubic closest packing.

Fig. 18 Schematic diagram showing the kinetic and thermodynamic intercalate phases of hexagonal LiAl - Cl. a Host material, b Kinetic intercalate phase containing a mixture of 1,4- and 1,2-BDA. c Thermodynamic intercalate phase containing soley 1,4-BDA, following the extrusion of 1,2-BDA...

The evidence for a separate MoS2 phase being present on the catalyst has already been discussed under A above. There is scant evidence for the existence of an intercalation phase on the supported catalyst. Much of the argument is based on the intercalation model proposed for the bulk Ni-WS2 catalyst (108). Canesson and Grange (109) and Mone (55) have... 

Sometimes compounds of definite composition may be formed, such as KC6 or CdBr, but in other cases intercalated phases may be non-stoichiometric such as Li2TiS2 (O < x < 1). Most interaction reactions... 

Figure M Calculated nanocomposite phase diagram (in the limit of small organoclay loadings). Solid line is the phase boundary between weakly intercalated stacks and partially exfoliated, partially intercalated phase, as calculated using compressible SCFT. Dashed line is the phase boundary between immiscible and exfoliated phases, as calculated by incompressible SCFT.

Tennakoon et al. (1983) IR Clays, montmorillonite Dehydration, intercalation, phase stability + + + Alcohol intercalation at elevated pressures... 

PROP White or light-yeUow crystals, powder, or solid moisture-sensitive. Monoclinic forms intercalated phases with graphite + CI2. D 3.68, mp 216-220°, bp 239.3°. Decomposed by water sol in ale. Volatilizes at 144°. 

The layered double hydroxides have been of interest as anion exchangers, basic catalysts, and catalyst precursors. Pillared derivatives of the type discussed earlier for the clays have been synthesized by ion exchange with polyoxometallate anions but have lower thermal stability. Several authors have reported synthesis of layered double hydroxides pillared with the Vio028 ion by direct ion exchange or by techniques that involve preswelling the layer structure with an organic anion. For example, the terephthalate anion was used in the synthesis ofVio028 and Mo7 024 intercalated phases. 

Exfoliation of the perovskite related layer structures is more difficult than for the clays and acid phosphates discussed earlier but can be achieved by intercalation of large bulky amines. Treacy etal. reported that the layered perovskite HCa2Nb30io could be made to form unilamellar sheets by first intercalation of an amine polyether. Spontaneous exfoliation of the layers occurs on subsequent exposure of the intercalated phase to a suitable solvent. Exfoliation techniques have been extended to other systems using tetra(n-butyl)-ammonium hydroxide (TBAOH) by Mallouk and others. A number of examples of the protonated layered perovskite phases that intercalate bases have been exfoliated. The Dion-Jacobson phases typically exfoliate to form plates but others including Ruddlesden-Popper tantalates curl to form tubular scrolls . Part of the interest in these single layer dispersions arises from their use as building blocks in the layer-by-layer self-assembly of thin films. Single layers derived from exfoliated perovskites can be attached to or alternately stacked with polycationic layers to produce thin films. Tiled monolayer structures and multilayer perovskite heterostructures result from the self-assembly. 

The SmAc phase was the first intercalated phase to be discovered [68] but examples of intercalated SmC and SmI phases and intercalated crystal B and J phases have since also been identified [69]. It is important to note, however, that tilted intercalated phases have only been observed for non-symmetric dimers containing long odd membered spacers and presumably such bent molecules experience great difficulties in packing efficiently into the intercalated network. Indeed, this packing difficulty may provide the driving force for the formation of the tilted intercalated smectic phases. 

For M0O3—hmta intercalation compounds (Mo4, Mo5, and M06), the X-ray results are as follows A diffiraction peak at 8.7° (d = 1.01 nm) is present in the X-ray patterns of the three compounds. However, the intensity of this peak decreases in the sequence M06 < Mo5 < Mo4. For the Mo4 compound this peak is almost absent. Furthermore, this is not a dif action peak due to free hmta. So, it is possible to suppose that at lower hmta/MoOs ratios, an intercalation phase, not present at higher concentration is formed. Based on the experimental interlayer distance for M0O3 (0.70 nm) and the molecular length calculated for hmta (0.40nm), the intercalation feature shown in Fig. 6.10 can be proposed. 

The first intercalation chemistry was reported in 1841 by Schafifautl, who successfully intercalated sulfate ions into graphite. After this pioneering work, fascination with intercalation chemistry did not start until the 1960s. The synthesis and study of intercalation compounds are both useful and rewarding. Intercalated phases have found applications as electrodes in high-energy-density batteries [9] and as catalytic materials [10]. Since the... 

Using a one-pot reaction design, an intercalated compound of polyaniline into M0O3 was prepared by Shao et al. [60]. This particular method of synthesis uses a coprecipitation route to fabricate the layered structure. An excess of aniline was acidified to a pH of 0.5, to which was added ammonium molybdate [(NH4)gMo7024.7H20] and FeCl3. The powder pattern of the isolated product revealed the formation of an intercalated phase of polyanihne into M0O3. The identity of the entrapped polymer was confirmed by FTIR... 

Chang et al. also reported on the intercalation of aniline into zirconium phosphate sulfophenylphosphonate (ZPS), an organo derivative of a-zirconium phosphate [70]. The hydrophilic (—SO3H) groups in ZPS promote swelling of ZPS, which served as a template for aniline. The aniline-ZPS system was then oxidized with ammonium peroxydisulfate to yield a polyaniline-ZPS composite. However, there is no X-ray evidence that has been provided to support the formation of an intercalated phase. 

Bissessur and coworkers explored the inclusion of poly(2-ethylaniline) (PEA) and poly(2-propylaniline) (PPA) into GO, in addition to polyaniline [90]. The technique of intercalation differed from previously reported methods. They showed that polyaniUnes can be directly inserted into GO without the preparation of precursor phases. The polymers were first prepared from the monomers by oxidation with ammonium peroxydisulfate in acidic medium. GO, synthesized by using the Hummers method, was dispersed in deionized water with the aid of sonication. Colloidal suspensions of the polymers in NMF were then added to the aqueous GO suspensions. The reaction mixtures were then acidified and heated at 60 °C for 90 min. The intercalated phases were isolated via freezedrying. A similar process was used to intercalate polypyrrole into GO [91]. 

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