Kaolinite-hydrazine intercalate

Changes in the vibrational modes of the adsorbent, however, reflect only those changes which occur to the substrate they do not provide direct insight into the structure and bonding of the adsorbed species. In order to examine the influence of the surface on the intercalated species, the vibrational modes of the adsorbate must be obtained. In a previous dispersive-IR absorption study of the kaolinite-hydrazine intercalate, Ledoux and White (17) observed that the ISu hydroxyl groups of... 

Figure 4. FT-IR (A,B) and Raman (C,D) spectra of non-intercalated kaolinite (top spectra), and of kaolinite-hydrazine intercalates in the 3600 to 3725 cm-1 region (bottom spectra). Spectra were obtained at 298 K and 1 atm. pressure.

Figure 9. Controlled-environment X-ray diffraction patterns of a kaolinite-hydrazine intercalate in the 7 to 11 ° 20 region, obtained as a function of pressure at 298 K.

Johnston, C.T. Stone, D.A. Applewhite, L.A. Vibrational spectroscopic study of tire kaolinite-hydrazine intercalation complex. The Third Conference on the Environmental Chemistry of Hydrazine Fuels, Panama City, FL 15-17 Sept. 1987 1987, ESL-TR-87-74,118. 

C.T. Johnston, D.L. Bish, J. Eckert L.A. Brown (2000). J. Phys. Chem. B, 104, 8080-8088. Infrared and inelastic neutron scattering study of the 1.03-and 0.95-nm kaolinite-hydrazine intercalation complexes. 

These include hydrazine, dimethylsulfoxide (DMSO), formamide and some derivatives (N-methylformamide and dimethylformamide), acetamide and some derivatives, and pyridine N-oxide. Some salts such as potassium acetate also intercalate kaolinites. Once intercalated by one of these small molecules or salts, other molecules which normally do not directly intercalate kaolins can be introduced by replacement. Further, the exposure of the inner surfaces by intercalation gives one the opportunity to alter the interlayer bonding of the kaolin layers by chemical modification of the inner surfaces. 

Raman spectra of hydrazine (a) and of the kaolinite-hydrazine (KH) intercalate (b) suspended in liquid hydrazine are shown in Fig. 1. In contrast to the strong IR-active absorption bands characteristic of clay minerals below 1200 cm-1, the corresponding Raman bands of kaolinite are relatively weak. Nonetheless, both the kaolinite and the hydrazine bands can clearly be resolved (Fig. lb). Hydrazine bands occur at 903,1111,1680, 3200,3280, and 3340 cm-1, whereas the kaolinite bands are found at 140 (not shown), 336, 400, 436, 467, 514, 636, 739, 794, and 3620 cm-1. Observation of lower-frequency adsorbate modes below 1200 cm-1 are often obfuscated in IR absorption spectra because of the strong lattice- framework vibrational modes. As the Raman spectrum of the KH complex shown in Fig. la indicate, the lower-frequency modes of hydrazine below 1200 cm-1 can readily be resolved. The positions of die hydrazine bands in the KH spectrum (Fig. lb) are similar to those of liquid hydrazine (Fig. la) and agree well with published vibrational data for hydrazine (22.23.29-31). The observed band positions for the KH complex, for hydrazine, and for kaolinite are listed in Table 1. 

The dominant spectral component in the Raman spectrum of the KH intercalate (Fig. lb) is hydrazine. By comparison, the IR bands of kaolinite are much more prominent than those in the Raman spectrum. Consequently, the strong IR-active... 

The synthesis of palladium nanoparticles on montmorillonite layer silicates was studied. The Pd particles were prepared in situ in the interlamellar space of montmorillonite dispersed in an aqueous medium. Macromolecules were adsorbed on the support from an aqueous solution, followed by adsorption and reduction of Pd ions. The Pd° nanoparticles appear and grow in the internal, interlamellar space as well as on the external surfaces of the lamellae. Well-crystallized kaolinite clay can be disaggregated by the intercalation of DMSO to individual lamellae, which may serve as excellent supports for metal nanoparticles. After the adsorption of palladium precursor, metal nanocrystals were reduced by hydrazine or sodium borohydride between the kaolinite lamellae, i.e., in the interfacial layer acting as a nanoreactor. The incorporation of nanoparticles between the lamellae was shown hy XRD measinements. This procedure makes possible the steric control and restriction of nanoparticle growth. The stability of nanoparticles can be further enhanced hy the addition of polymers (PVP) and surfactants (alkyl-ammonium salts) that are also adsorbed between the kaolinite lamellae. The presence of the particles was also verified and their sizes were quantified by TEM measurements. 

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