Large Basal Spacing Research Articles

Study on the process of hydrogen-doped indium oxide for silicon heterojunction solar cell mass production

In this work, we conducted a comparative study on water vapor (H2O) process and hydrogen gas (H2) process to prepare the IMO:H films based on industrialized DC magnetron sputtering system. To dynamically control the residual H2O pressure, we installed a set of polycold coil and kept it turned on during the sputtering process. The film characteristics of Hall mobility, carrier density, sheet resistance, and transparency was investigated. The results revealed that the silicon heterojunction (SHJ) solar cell with H2 process had a higher Hall mobility and greater transparency in the 400–600 nm wavelength range resulting in a lower contact resistivity and a slight increase current density compared to the H2O process. The median efficiency (Eff) achieved with the H2 process improved by 0.09% absolute to 25.43%, mainly because of the increased Jsc and FF. And the IMO:H films with H2 process had a large basal spacing with (400) and (222) crystal planes resulting in maintaining a more stable and reliable structure at temperatures below 200 °C. After the optimization of TCO layer process, we manufactured the industrial-grade SHJ cells with max efficiency (Eff), Voc, Jsc, and fill factor (FF) values as high as 26.27%, 753 mV, 41 mA/cm2, and 86%, respectively. The IMO:H films with H2 process can thus be considered more suitable for large-scale production.

Synthesis of NiFe layered double hydroxides with varied layer charge densities: the templating effect of dioctyl sulfosuccinate.

NiFe layered double hydroxides (LDHs) intercalated with dioctyl sulfosuccinate with varied Fe3+/(Ni2+ + Fe3+) ratios (0.04-0.25) were prepared by constant-pH co-precipitation from an aqueous solution of Ni and Fe perchlorates at room temperature. The interlayer dioctyl sulfosuccinate was exchanged with carbonate by the reaction of the product with an aqueous solution of sodium carbonate. The basal spacing of the NiFe-LDHs containing carbonate varied (0.80-0.90 nm) depending on the Fe3+/(Ni2+ + Fe3+) ratio; larger basal spacing was attained from the LDH with smaller Fe3+/(Ni2+ + Fe3+) due to the weaker attractive force between the LDH layer and the interlayer anion, proving that the Fe3+/(Ni2+ + Fe3+) ratios were associated with the layer charge density of NiFe-LDHs.

Structure and release properties of pyrethroid/sulfobutyl ether β-cyclodextrin intercalated into layered double hydroxide and layered hydroxide salt.

The aim of this study was to realize the intercalation of the pyrethroid pesticides beta-cypermethrin (BCT) and lambda-cyhalothrin (LCT) into ZnAl-layered double hydroxides (LDH) and NiZn-layered hydroxide salt (LHS). BCT (LCT)/SBECD-LDH and BCT (LCT)/SBECD-LHS hybrids were obtained with the aid of sulfobutyl ether β-cyclodextrin (SBECD) through one step method. The hybrids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry and differential thermal analysis (TGA/DTA). The hybrids based on LHS had larger basal spacing than those on LDH. The LDH-hybrids prepared in N-methylpyrrolidone (NMP) had larger basal spacing than those in ethanol. These results were discussed in terms of the matrix structure and solvent properties. The supramolecular structure of the hybrid was reasonably proposed. Furthermore, the release properties of BCT (LCT) from the hybrids were investigated and discussed in two media. The release rate in pH = 5.0 was slower than that in pH = 6.8. The accumulated release amount of pesticide in pH = 5.0 was lower than that in pH = 6.8. LHS-hybrids synthesized in ethanol exhibit a sustainable release property. These depend on the inclusion complexes’ arrangement and release medium. The release kinetic processes could be described by pseudo-second order and parabolic diffusion models. The release behavior can be controlled by adjusting the synthesis conditions and the releasing media. This provides the guidance for the application of SBECD and LDH (LHS) in pesticide formulation.

Nanoscale structural and morphological features of kaolinite nanoscrolls

One-dimensional kaolinite nanoscrolls have been arousing great interest due to their applicability in advanced materials for adsorption and slow release of reagents, as well as in nanoscale reactors and carriers. Production of high-quality halloysite-like nanoscrolls with controlled morphology, however, remains challenging as there is a lack of understanding of the curling process of kaolinite layers on the atomic scale. In the present work, the nanoscrolls were efficiently produced from the readily available natural kaolinite using a two-pot solvothermal exfoliation of the kaolinite-dimethyl sulfoxide, kaolinite-urea, and kaolinite-N-methylformamide precursors. The structures, sizes, shapes and crystallographic properties of the produced halloysite-like nanoscrolls were characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and electron tomography in scanning transmission mode (STEM). In order to avoid structural disintegration of the highly electron beam-sensitive nanoscrolls, we used a low imaging current (70–240 e/A2); as a result, the acquisition of structure images was possible. In contrast to the triclinic symmetry of kaolinite, electron diffraction patterns suggest a hexagonal symmetry of exfoliated layers. Both HRTEM and STEM tomography show partially and completely rolled up layers, with the axis of curvature being parallel to either the a or b axes. The methanol-grafted nanoscrolls have a variable but larger basal spacing (from 0.76 to 0.90 nm) than the value in ordered kaolinite (0.72 nm). Their external diameters range from 22 to 75 nm, lengths from 218 to 2287 nm, aspect ratios from 5 to 74, and the scrolls have recognizable chirality. Crystallographic image processing of HRTEM structure images suggest that the tetrahedral sheet can be on either the outer or the inner sides of the nanoscrolls. Molecular simulation results for the curled kaolinite layers are consistent in their details with the experimental observations, suggesting that the layers may roll up either way.

Synthesis of Zn-Saponite Using a Microwave Circulating Reflux Method under Atmospheric Pressure

Smectite is a common clay mineral in nature. Due to its tendency to swell and its strong cation exchange capacity (CEC), smectite is prevalently used in industrial and technological applications. Numerous scholars have explored smectite synthesis, which usually involves autoclaving under high pressure. However, this approach requires an array of expensive equipment, and the process consumes time and energy. This study adopted self-developed equipment to synthesize zinc saponite (Zn-saponite), a type of trioctahedral smectite, using a microwave circulating reflux method under atmospheric pressure. Compared with the conventional hydrothermal methods, the proposed method entails fewer constraints regarding the synthesis environment and can be more easily applied to large-scale synthesis. The phase purity of the synthetic product was examined using X-ray diffraction and the CEC of the product was tested. The results revealed that the microwave circulating reflux method could synthesize Zn-saponite in 16 h under atmospheric pressure, and the CEC of the product reached 120 cmol(+)/kg. In addition, the product exhibited larger basal spacing and a 32% increase in CEC compared with Zn-saponite synthesized using a hot-plate under atmospheric pressure.

Layered K0.28MnO2·0.15H2O as a Cathode Material for Potassium-Ion Intercalation.

Here, we present K0.28MnO2·0.15H2O, which has a two-dimensional open framework, as an intercalation host for potassium ions. K0.28MnO2·0.15H2O has a layered structure consisting of edge-sharing MnO6 octahedra with a large basal spacing of ∼7.3 Å, which facilitates K+-ion mobility. Water molecules in the interlayers between the MnO2 layers play an important role as a pillar to support the structure during repetitive de/potassiation cycles, as confirmed by an operando X-ray diffraction study. As a result, the large K+ ions readily migrate into the crystal structure, resulting in satisfactory electrochemical performance in K-cells. With the aid of the structural pillar, the K0.28MnO2·0.15H2O cathode delivers a high reversible capacity of 150 mA h g-1 over 100 cycles at a rate of 0.1 C (15 mA g-1), with acceptable power capability up to 5 C-rates.

Synthesis and Characterization of North Aceh CEC Bentonite Determination with Methylene Blue Method and Increased D-Spacing after Addition of Surfactants CTAB-SDS

Bentonite is not susceptible to polymers because it is organophilic and has low basal spacing. The main objective of this study is to increase bason spacing of bentonite and change the properties of bentonite to hydrophobic by modifying bentonite with cationic and anionic surfactants using Cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). Surfactant with different CEC concentration, namely CTAB 1 CEC, 2 CEC and 3 CEC while SDS 0.5 CEC, 1 CEC and 1.5 CEC where the CEC is generated by halometric methods. From the results of the analysis with CEC bentonite value through the halometric method obtained 95.2 meq / 100 grams clay, while the basal spacing of interlayer bentonite with modification of cationic and anionic surfactants using X-Ray Diffraction (XRD) obtained an increase in basal spacing from 14. 18393 Å to 25.08971 Å on CTAB 3 CEC and SDS 1.5 CEC. This research can produce bentonite from northern Aceh with the largest basal spacing so that it can be intercalated by other additives.

Preparation of azobenzene-intercalated kaolinite and monitoring of the photoinduced activity

AbstractSystems consisting of layered structures and photoactive molecules have been studied extensively. The structures of resulting complexes may be controlled by UV–Vis radiation, which subsequently affects their materials properties. This study describes a synthesis route for obtaining a photoresponsive kaolinite intercalation compound. The material was prepared by co-intercalating azobenzene and benzylalkylammonium chlorides into a methoxy form of kaolinite. The resultant materials possessed large basal spacing values in the range of 45–55 Å. The UV–Vis and Fourier-transform infrared spectroscopy analyses confirmed the reversible photoisomerization of azobenzene upon exposure to UV and Vis radiation. This phenomenon was significantly influenced by the type and amount of co-intercalated molecules. Upon multiple trans–cis conversions, the azobenzene partially evaporated. For the first time, a kaolinite-based material was prepared that exhibited photochromic behaviour upon UV and Vis irradiation.

Sodium dodecyl sulfate intercalated and acrylamide anchored layered double hydroxides: A multifunctional adsorbent for highly efficient removal of Congo red

In this study, a novel adsorbent was designed and synthesized via intercalation of sodium dodecyl sulfate (SDS) in the interlayer, and subsequent grafting of acrylamide (AM) on the layer of layered double hydroxides (LDH) (named as AM/SDS-LDH), and applied for congo red (CR) removal. The morphological structure, wettability and physicochemical properties of the adsorbents were thoroughly characterized using SEM, EDS, N2-adsorption/desorption isotherm, static contact angle, XRD and FTIR. Results elucidated that SDS and AM were successfully introduced into the interlayer and onto the layer of LDH, respectively. Adsorption experimental results suggested that the maximum adsorption capacities of CR on SDS-LDH and AM/SDS-LDH at pH 5.0 and 293 K were 714.29 and 1118.78 mg/g, respectively, which were much higher than that of CR on LDH (588.24 mg/g). Based on the BET, XRD and FTIR analysis, the higher adsorption capacity of AM/SDS-LDH was mainly attributed to high surface area, large basal spacing as well as the abundant NH2 groups. The experimental data can be well fitted by pseudo-second-order kinetic and Langmuir isotherm models. Thermodynamic parameters indicated the adsorption process was favorable under the higher temperature condition. The synergistic effect existed during the adsorption process of CR onto AM/SDS-LDH, including the electrostatic interactions, anion exchange and hydrophobic-hydrophobic interactions. Overall, this study provided a strategy for design and fabrication of highly efficient adsorbents.

An Insight into the Silanization of Montmorillonite Nanoparticles

The purpose of this study is to investigate the effect of reaction conditions on the silanization of montmorillonite nanoparticles using methacryloxypropyltrimethoxysilane (γ–MPS) and to establish relationships between the reaction conditions, the grafting percentage, and the silane arrangement on the particles. The silanization reaction was performed in the following conditions: (i) acidic ethanol-water solution with a pH of 5 and (ii) basic cyclohexane with a pH of 9. To characterize the surface of montmorillonite nanoparticles, analytical methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), CHN elemental analysis, and X-ray diffraction (XRD) diffraction were utilized. In addition, the dispersion stability of modified particles suspended in different solvents was investigated using a separation analyzer. The results revealed silane grafting in cyclohexane (pH = 9) achieved higher silanization efficiency, leading to a larger basal spacing in montmorillonite nanoparticles. A parallel arrangement was also suggested for the silane molecules on the surface of the nanoparticles. The higher hydrophobicity of the modified nanoparticles and the decreased overall density of the grafted particles led to a better dispersion in ethanol and toluene.

Cr(VI) adsorption by montmorillonite nanocomposites

Various montmorillonite (Mt) nanocomposite adsorbents were prepared with Al13 cations, dodecyl trimethyl ammonium chloride (DTAC) or dodecyl amine (DA) and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and BET surface area and pore size analyses. The adsorption of hexavalent chromium, Cr(VI) onto various Mt nanocomposites as a function of adsorbent dosage, initial Cr(VI) concentration, contact time and solution pH was investigated. The results showed that the obtained nanocomposites had large basal spacing and good porous structure, and the specific surface areas followed the order: OH-Al-Mt>DA-Al-Mt>DTAC-Al-Mt>Na+-Mt>DTAC-Mt>DA-Mt. The removal efficiency of Cr(VI) ions increased with increasing the adsorbent dosage and contact time, but decreased with increasing initial Cr(VI) concentration, as expected. The adsorption of Cr(VI) was highly pH-dependent and the maximum removal efficiency of Cr(VI) was found in the acid environment. The adsorption equilibrium time was 2h and the adsorption kinetic data of Cr(VI) on various adsorbents were well described by the pseudo-second-order kinetics model, which indicated that the adsorption reaction of Cr(VI) ions with the adsorbents was mainly due to chemical adsorption. Both the Langmuir model and Freundlich model fitted the equilibrium data well, which suggested that the Cr(VI) adsorption onto various adsorbents was both as monolayer and on heterogeneous surface conditions. The adsorption results indicated that among all the adsorbents used in this experiment, the dodecyl amine and Al13 cations composited with Mt (DA-Al-Mt) was the most effective for removing Cr(VI) from wastewater.

Adsorption of carbon dioxide, methane, and their mixture by montmorillonite in the presence of water

Using grand canonical Monte Carlo (GCMC) simulations, we study the adsorption behavior of CH4, CO2, and their mixture at 298.15 K and pressures up to 50 bar in Na-, Cs-, and Ca-montmorillonite clays in the presence of water. Montmorillonite clays in the presence of preadsorbed water, preferentially adsorb CO2 over CH4 during both pure component and mixture adsorption. The atomistic model we have used, gives good agreement with available single-component experimental adsorption isotherms, for CH4 and CO2 molecules adsorbed onto montmorillonite clays in the presence of water. We observe the general trend that the presence of increasing preadsorbed water content in the clay interlayers, reduced adsorption amounts of pure CH4 and CO2 molecules. With a relatively large basal spacing (d = 30 Å), the favorability of adsorption of CO2 by montmorillonite at relatively low pressures and intermediate water contents has been demonstrated using simulations. GCMC simulation is also used to assess the effect of water on the adsorption of N2/CH4, H2S/CH4, CO2/N2, and CO2/H2S binary mixtures in Na-montmorillonite clay. The ideal adsorbed solution theory is shown to agree well with the observed adsorption capacities and selectivities of mixtures in Na-montmorillonite clay.

Gas‐phase Preparation of SO3‐Graphite: Host‐Exchange and Exfoliation

AbstractThe reaction of sulfur trioxide with graphite via gas phase led to an intercalation of a double layer of sulfur trioxide with a basal spacing of 11.1 Å. The SO3‐graphite was obtained atom‐efficient as a single phase product without the need of purification. The increased basal space should facilitate an exfoliation by rendering the tactoids more shear labile. A further weakening of the attractive forces within a stack was done by the replacement of sulfur trioxide with the surfactant perfluorobutanesulfonic acid leading to a basal spacing of 16.8 Å. The large basal spacings were also preserved in suspension and no defects were created. The mechanical exfoliation with ultrasound predominantly broke the platelets. A rotor‐stator device offering high shear forces was found to exfoliate the platelets more gently but there was still a good number of very small particles.

Highly selective removal of nitrate and perchlorate by organoclay

An organoclay was prepared using montmorillonite and hexadecylpyridinium chloride (HDPyCl) and tested for the removal of nitrate and perchlorate anions from aqueous solutions. The cationic surfactant modified organoclay was prepared at room temperature using HDPyCl corresponding to 4 times the cation exchange capacity (CEC) of Na-montmorillonite. Powder X-ray diffraction (XRD) analysis of the above organoclay showed a large basal spacing of 40.27Å with the intercalation of HDPy cations in the interlayers probably as a result of a paraffin-type bilayer arrangement. The adsorption data of nitrate and perchlorate were fitted to the Langmuir and Freundlich adsorption isotherms and pseudo-first order and pseudo-second order kinetic models to better understand their adsorption mechanisms. The nitrate and perchlorate uptakes by this organoclay could be described well using the Langmuir isotherm while their uptake kinetics fitted well to the pseudo-second order model. The maximum adsorption capacities of nitrate and perchlorate by the organoclay, HDPy-montmorillonite were calculated at 0.67 and 1.11mmolg−1, respectively. Nitrate and perchlorate uptake kinetics were found to be fast as equilibrium was reached within 4h. Furthermore, the uptakes of nitrate and perchlorate by HDPy-montmorillonite were found to be highly selective in the presence of Cl−, SO42− and CO32−, the most abundant naturally occurring anions. Therefore, the HDPy-montmorillonite could be used as a highly efficient adsorbent for the separation of nitrate and perchlorate from drinking or waste water and ground water.

Effect of the type of clay organo‐modifier on the morphology, thermal/mechanical/impact/barrier properties and biodegradation in soil of polycaprolactone/clay nanocomposites

AbstractThe effect of addition of unmodified (CNa+) and modified (C30B and C20A) montmorillonites on the performance of polycaprolactone (PCL) based nanocomposites prepared by melt intercalation was studied. The study covers morphological and thermal aspects, mechanical and barrier properties and also biodegradability, which are important for packaging applications. Particular effort was made to find the main characteristics of the clays responsible for the final clay dispersion degree inside the nanocomposite. The most hydrophobic reinforcement (demonstrated by water adsorption tests) also showed the strongest thermal stability (shown by thermogravimetrical analysis) and the larger basal spacing (calculated by X‐ray diffractometry (XRD)), which were the main characteristics that led to the best clay dispersion degree inside the PCL matrix (demonstrated by XRD and Transmission Electron Microscopy (TEM)). The findings demonstrate that a biodegradable polymer/clay nanocomposite with enhanced mechanical, impact, and barrier properties was obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Intercalation of Fe(III) complexes into layered double hydroxides: Synthesis and structural preservation

In this study, intercalation of Fe(III) complexes [Fe(Ox)3]3− and [Fe(Cit)2]3− in Mg2Al layered double hydroxides (LDHs) had been carried out by different routes: direct self-assembly, reconstruction and anion exchange. The result of XRD indicated that these two kinds of Fe(III) complexes intercalated LDHs (LDHs/Fe-complexes) could be successfully synthesized by anion exchange obtaining two well crystallized LDHs both with a large basal spacing. The chemical environment of iron ion in the intercalated Fe complexes was determined by FTIR, XPS and XAFS, the results of which concertedly proved that the intercalated Fe complexes were well preserved in the interlayer of LDHs. The arrangement of the Fe(III) complexes anions in the galleries of LDHs was studied by one-dimensional electron density projection. The results showed that the [Fe(Ox)3]3− anions were probably accommodated in the gallery of LDHs as an interdigitated bilayer arrangement, and the [Fe(Cit)2]3− were perpendicularly arranged against the LDHs sheets. Through the research, it is proved that the obtained LDHs/Fe-complexes markedly enhanced the UV–vis absorption ability of Fe complexes.

Microstructure and supercapacitive properties of buserite-type manganese oxide with a large basal spacing

A hydration-layered structure of buserite-type manganese oxide (Mg–buserite) was successfully synthesized by an ion exchange method. The as-prepared Mg–buserite possesses a large basal spacing of 10 Å, and contains Mg2+ ions and two sheets of water molecules in the interlayer region. The supercapacitive behaviors of Mg–buserite were systematically investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD) experiments and electrochemical impedance spectroscopy (EIS). The results showed that the specific capacitance of the Mg–buserite electrode sharply increased during the initial 500 cycles and reached a maximum of 164 F g−1 at approximately the 500th cycle at a scan rate of 1 mV s−1, and then it remained an almost constant value and decreased slightly upon prolonged cycling. After 22,000 cycles, the specific capacitance decreased by approximately 6% of the maximum specific capacitance. The superior capacitive behavior and excellent cycling stability of the as-prepared Mg–buserite are attributed to the large basal spacing, which can accommodate a larger amount of electrolyte cations and provide more favorable pathways for electrolyte cations intercalation and deintercalation. The experimental results demonstrate that Mg–buserite is a promising candidate as an electrode material for supercapacitors.

Thermal stability of organoclays with mono- and di-alkyl cationic surfactants

In this study, mono- and di-alkyl cationic surfactants were used to prepare organoclays through ion exchange and the prepared organoclays were characterised by X-ray diffraction (XRD) and thermogravimetric analysis (TG). Larger basal spacings were observed in the interlayer of the organoclays intercalated with DDDMA than organoclays intercalated with DDTMA. The DTG curves identify the thermal stability of organoclays intercalated with two different types of surfactants (DDTMA and DDDMA) and the different arrangements of the surfactant molecules intercalated in the montmorillonite. Both organoclays intercalated with organic surfactant molecules proved to be thermally stable at high temperature. This study provides an understanding of the structure and properties of organoclays, which will enhance the potential applications of organoclays in environmental remediation.

Synthesis and characterization of aluminum and Al/REE pillared clays and supported palladium catalysts for benzene oxidation

Volatile organic compounds (VOCs) are considered as a major pollutant in indoor and outdoor air. More stringent environmental regulations have been implemented in order to reduce the VOC emissions. One of the techniques available for destructive removal of VOCs is catalytic oxidation. In the present work, Al/Rare Earths (REE: Y, Ce, La, Pr and Nd) pillared clays (PILCs) were used to support 0.2 wt.% of palladium for the complete oxidation of low concentration of benzene. The supports and catalysts were characterized by XRD, N 2 adsorption/desorption, FTIR spectroscopy, HRTEM and H 2-TPR techniques. The results indicated that after Al and Al/REE pillaring, the basal spacing, S BET, A mic and V mic of Al and AlREE-PILC had a considerable increase compared with those of Na-mmt. Activity tests of deep oxidation of benzene showed that the catalytic activity of Pd catalysts supported on Al and AlREE-PILC were much higher than that on initial clays, which was due to the fact that optimized structure of PILCs, such as large basal spacing, high S BET and porosity, improved Pd dispersion and increased the active sites of Pd. Especially for Pd/AlCe-PILC, the temperature of complete oxidation was about 280 °C, exhibiting the highest catalytic activity.

Novel polymer/surfactant modified montmorillonite hybrids and the implications for the treatment of hydrophobic organic compounds in wastewaters

Polydiallyldimethylammonium (PDADMA) and cationic surfactant cetyltrimethylammonium (CTMA) were applied simultaneously to modify montmorillonite, with the aim to synthesize novel organo montmorillonites with a high sorption capacity towards organic pollutants. The basal spacings of the resulting organo montmorillonites (C/P-Mt) were characterized with XRD, and their sorption characteristics for phenol were investigated. It showed that C/P-Mt had larger basal spacings than the corresponding CTMA modified montmorillonite (C-Mt), which indicated that both CTMA and PDADMA were intercalated into the interlayer spaces of the montmorillonite. C/P-Mt was shown to have much better sorption capacity towards phenol than the corresponding C-Mt, and the maximum increase of sorption coefficient (i.e., Kd) and the organic carbon normalized sorption coefficient (i.e., Koc) reached 45% and 20%, respectively. The possible reason for the enhanced sorption capacity is that the intercalation of PDADMA caused a change in the arrangement of the CTMA micelles, which might then lead to the increased affinity towards phenol. Results of this work showed that simultaneous intercalation of cationic polymers could be a possible method for increasing the sorption capacity of the traditional surfactant synthesized organo montmorillonites.