Papers by Keyword: Intercalation

Abstract: Graphite intercalation compounds (GIC) are the most common precursors for expanded graphites which are promising materials for many applications. A series of GICs with different expanding volumes (EV) were prepared by a two-step chemical intercalation way. Effects of the input of oxidant and intercalating agent on the EV of GICs were discussed. The microstructures and morphologies of graphites before and after intercalation were analylized by X-ray diffraction and scanning electron microscope, respectively. The results show that the GIC with an EV of 600 ml⋅g^-1 may be prepared under temperal conditions by a two-step intercalation way. The interlayer spacing of the pre-GIC formeded by one-step intercalation is a bit larger than that of natural graphites, while the interlayer spacing of the GIC obtained by two-step intercalation becomes much larger than that of the pre-GIC because of secondery intercalation. When the d-spacing (d₀₀₂) value of the GIC rises from 0.3590 nm up to 0.3711nm, its EV increases from 267 up to 600 ml⋅g^-1 due to the decomposition and release of much more intercalated substances during a thermal shock.

Abstract: The intercalation of calcein into Mg/Al-NO₃-LDHs and Zn/Al-NO₃-LDHs by co-precipitaiton and ion-exchange method has been investigated. The obtained intercalation compounds were characterized by XRD, FT-IR and TG-DSC techniques. The results show that the original interlayer nitrate ions can be replaced by the organic anions under the controlled conditions. From the XRD data, the guest size and the orientation of anions between the layers were determined and after intercalation the interlayer spaces of the materials are expanded to 1.81 nm. FT-IR and DSC/TG curves reveal the presence of a complex system of supramolecular host-guest interaction and the increase of thermal stability of materials and the photochemical properties of compounds were studied by UV-Vis adsorption spectroscopy. These results indicate that the confinement of the UV absorbents in their anionic form within the restricted space of the interlayer region of LDHs is in favor of guest-host and guest-guest interactions, so that the UV aborption range and ability of the intercalation compounds are changed.

Abstract: The intercalation of herbicide, 3,4-dicholorophenoxyacetic acid (3,4D), into zinc-aluminium-layered double hydroxide (LDH) for the formation of a new nanocomposite ZADX, was accomplished via anion exchange method. Due to the intercalation of 3,4D with LDH interlayer domain, basal spacing expanded from 8.9Å in the ZAL to 17.7-19.0 Å in the ZADX. The percentage loading of 3,4D in the ZADX is 51.4 % (w/w). The FTIR spectra of the nanocomposite shows resemblance peaks of the 3,4D and Zn-Al-layered double hydroxide indicating the inclusion of 3,4D into the layered double hydroxide. Surface area of the resulting nanocomposite increased from 1.3 to 7.14 m²g^-1 with the nitrogen adsorption-desorption of type IV.

Abstract: The present work aims at a better understanding of the influences of the intercalated mono-, di- and triethanolamines on the characteristics and CO₂ adsorption ability of sodium form of bentonite (Na-bentonite). The results revealed that the molar mass of intercalated amines significantly influenced the structural and surface properties as well as the CO₂ adsorption capacity of Na-bentonite. In this respect, a stepwise increase in the d-spacing of Na-bentonite with the molar mass of amine was recorded by XRD technique. However, an inverse effect of the molar mass of amine on the surface area was confirmed by BET method. CO₂ adsorption experiments on amine-bentonite hybrid adsorbents showed that the CO₂ adsorption capacity inversly related to the molar mass of amine at 25 ^ͦC and 101 kPa. Accordingly, Na-bentonite modified by monoethanolammonium cations adsorbed as high as 0.475 mmol CO₂/g compared to 0.148 and 0.087 mmol CO₂/g for that one treated with di- and triethanolammonium cations, respectively.

Abstract: Mesoporous maghemite γ-Fe₂O₃ was obtained by thermal decomposition of iron citrate xerogel hydrate. The influence of precursor molar concentration and calcination temperature on the material phase composition, morphology, crystalline and magnetic microstructure, surface condition and optical properties was studied. The model of mesoporous γ-Fe₂O₃ formation is proposed. Obtained maghemite was tested as cathode material for lithium power sources. Increase of lithium power sources specific capacity and energy with the samples specific surface area enlarging is determined. Two kinetic processes are observed during discharge processes: lithium accumulation at the cathode material/electrolyte interface and diffusion of lithium ions into the material crystal structure. The diffusion coefficients of lithium in the cathode material on the different stages of discharge process are calculated.

Abstract: A controlled release composite has been prepared by intercalation of sodium paeonolsilate (PAS) into Mg/Al layered double hydroxide (LDH) with the molar ratio (M²⁺/M³⁺) of 2:1. The powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) confirm the intercalation of PAS into the galleries of LDH. The chemical composites of PAS-LDH were revealed by elemental analysis. Release tests of the PAS-LDH composite showed that no burst release phenomenon occurred at the beginning stage and a high release ratio of PAS (89.8%) was obtained, exhibiting controlled release behavior. Furthermore, the parabolic diffusion model was used to simulate the release kinetics of PAS from the LDH carrier, indicating that the intraparticle diffusion via ion-exchange is the rate-determining step in the release process. It is significance in this work for introducing the PAS-LDH composite to develop antifouling materials with long-term activity.

Abstract: Zn/Al layered double hydroxide (LDH) intercalated by an anionic phenoxyherbicide guest, 3-(4-methoxypheny) propionate (MPP) were prepared by ion-exchange method. Power XRD and FTIR shows that the MPP phenoxyherbicide were successfully intercalated into the LDH interlayer. The basal spacing for Zn/Al layered double hydroxide-3-(4-methoxyphenyl) propionate nanocomposite (LDH-MPP) was 18.7 Å - 20.5 Å for 0.015 M, 0.025 M, and 0.050 M of MPP, respectively. Thermal analysis shows that the thermal stability of MPP was improved by the intercalation into the LDH interlayer. The results were also supported by elemental analysis and the surface morphology of this nanocomposite.

Abstract: Sodium montmorillonite (Na-MMT) was modified with various type of diamine surfactants. The modification imparts hydrophobic characters of MMT, thus enhancing its compatibility and dispersibility in polymer matrix. In this research, pristine MMT was modified with three types of diamine surfactants, namely, 1,3 diaminopropane (DAP), 1,8 diamino octane (DAO) and 1,5 diamino-2-Methyl pentane (DAMP). These diamines have different molecular structures where DAP has a short linear structure, DAO has eight carbons while DAMP has a methyl branch on its backbone. The modification was carried via cationic exchange process. X-ray diffraction (XRD) analysis showed the enhancement of d-spacing of MMT galleries and the formation of intercalated structure with the incorporation of diamines. Overall, type of diamines did not give significant effect on the d-spacing values with DAMP-MMT exhibited a slightly higher d-spacing at 13. 36 Å. The presence of methyl branch on the DAMP backbone was thought provide more spacing for the diamine to intercalate through the MMT gallery. Meanwhile, the detection of –NH bending amine group at 1470 cm^-1 on the Fourier infrared (FTIR) spectra, corresponding to the free surfactant tail, had confirmed the successfulness of cationic exchange reaction between the diamines and MMT surface.

Abstract: The present study investigates the effects of intercalation process of protonated primary, secondary and tertiary amines on structural and surface characteristics of sodium form of bentonite clay. For this purpose, sodium form of bentonite clay was prepared and then exchanged with mono-, di-and triethanolammonium cations via intercalation mechanism into the interlayer space of the clay. The prepared samples were characterized by XRD and BET techniques. An increase in the d-spacing of bentonite clay with the molar mass of amines was observed in their x-ray diffractograms, following the order of: triethanolamine > diethanolamine > monoethanolamine. The BET results showed a gradual decrease in the BET surface area with the increase in the molar mass of amines used. Based on the results obtained, it can be concluded that the molar mass of amines has significant effects on structural and surface properties of bentonite clay.

Abstract: A new layered-double hydroxide-3-(4-hydroxyphenyl) propionate (LDH-HPP) has been synthesized by intercalation of 3-(4-hydroxyphenyl) propionic acid (HPP) into Zn-Al-layered double hydroxide (LDH) by ion-exchange method. PXRD, FTIR, TGA/DTG, compositional studies and FESEM were used to characterize the synthesized nanocomposite. The intercalation of HPP into the interlayer gallery space of LDH was characterized by x-ray diffractogram showed expanded basal spacing of the value of 17.1 Å. The FTIR spectra of LDH-HPP nanocomposite synthesis by 0.025M HPP resembled a mixture of both FTIR spectra of HPP and LDH. Thermal analysis of LDH-HPP nanocomposite shows a better thermal stability as compared to the pure HPP, which proved that the intercalation of HPP into LDH interlayer enhanced the thermal stability of the HPP.