Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Hydration Characteristics and Mechanical Properties of Cement-Based Materials Modified by Calcined Zeolite and Montmorillonite

Montmorillonite and clinoptilolite zeolite were used as representative materials to prepare calcined clay-cement binary cementitious materials in order to study the effect of calcination treatment on the activation of clay minerals and the activity difference between layered and framed clays in this research.The influence of different calcined clay content(2%,4%,6%,8%,10%)on the fluidity,compressive strength,microstructure,phase change,and hydration heat of cement-based materials were analyzed.The calcined clay improves the fluidity of cement-based materials as compared with the uncalcined group.The addition of calcined montmorillonite(CMT)improves the development of mechanical strength,and the optimal compressive strength reaches 85 MPa at 28 days with 8%CMT.However,the activity of calcined clinoptilolite zeolite(CZL)is weak with few reaction sites,which slightly reduced the mechanical strength as compared to the blank sample.The addition of CMT changes the microscopic morphology of hydration products such as C-S-H and C-A-H,leading to the formation and transformation of ettringite in the early stage.It promotes the gradual polymerization of Si-O bonds into Si-O-Si bonds simultaneously,which accelerates the early hydration process.However,CZL acts mainly as a filling function in the cementitious system.In brief,CMT as an admixture can improve the mechanical properties of cement,but CZL has little effect.This work provides a guideline for the applications of calcined clay in cement,considering the influence of clay type on workability and mechanical strength.

Improving physical properties of poly(vinyl alcohol)/montmorillonite nanocomposite hydrogels via the Hofmeister effect

Hydrogel is a kind of three-dimensional crosslinked polymer material with high moisture content.However,due to the network defects of polymer gels,traditional hydrogels are usually brittle and fragile,which limits their practical applications.Herein,we present a Hofmeister effect-aided facile strategy to prepare high-performance poly(vinyl alcohol)/montmorillonite nanocomposite hydrogels.Layered montmorillonite nanosheets can not only serve as crosslinking agents to enhance the mechanical properties of the hydrogel but also promote the ion conduction.More importantly,based on the Hofmeister effect,the presence of(NH_(4))_(2)SO_(4)can endow nanocomposite hydrogels with excellent mechanical properties by affecting PVA chains'aggregation state and crystallinity.As a result,the as-prepared nanocomposite hydrogels possess unique physical properties,including robust mechanical and electrical properties.The as-prepared hydrogels can be further assembled into a high-performance flexible sensor,which can sensitively detect large-scale and small-scale human activities.The simple design concept of this work is believed to provide a new prospect for developing robust nanocomposite hydrogels and flexible devices in the future.

Cadmium adsorption in montmorillonite as affected by glyphosate

Behaviors of soil heavy metals are often affected by coexisting herbicides due to their physical and chemical interaction. Effect of glyphosate, an herbicide containing -PO 2- 3 and -COOH groups, on cadmium adsorption in montmorillonite was studied in detail. The results showed that the cadmium adsorption quantity in montmorillonite increased with increasing soil solution pH and cadmium concentration as usual, but decreased with glyphosate, which is due to the formation of a low affinity complex of Cd and glyphosate and decreasing solution pH induced by glyphosate addition. When the equilibrium solution pH was below 6.7, glyphosate has little effect on cadmium adsorption, but when the equilibrium solution pH was above 6.7, glyphosate significantly decreased cadmium adsorption quantity in montmorillonite. In addition, the adding order of Cd and glyphosate also influenced Cd adsorption quantity in montmorillonite.

Efficient and Convenient Procedures forthe Formation and cleavage of steroid acetals catalysed by montmorillonite aite K 10

Acetalization of steroid ketones and cleavage of the acetals have ben carried out inexcellent yield under catalysis of montmorillonite K 10.

Extractive oxidative desulfurization of model oil/crude oil using KSF montmorillonite-supported 12-tungstophosphoric acid

12-Tungstophosphoric acid（PW） supported on KSF montmorillonite, PW/KSF, was used as catalyst for deep oxidative desulfurization（ODS） of mixed thiophenic compounds in model oil and crude oil under mild conditions using hydrogen peroxide（H2O2） as an oxidizing agent. A one-factor-at-a-time method was applied for optimizing the parameters such as temperature, reaction time, amount of catalyst, type of extractant and oxidant-tosulfur compounds（S-compounds） molar ratio. The corresponding products can be easily removed from the model oil by using ethanol as the best extractant. The results showed high catalytic activity of PW/KSF in the oxidative removal of dibenzothiophene（DBT） and mixed thiophenic model oil under atmospheric pressure at 75 ℃ in a biphasic system. To investigate the oxidation and adsorption effects of crude oil composition on ODS, the effects of cyclohexene, 1,7-octadiene and o-xylene with different concentrations were studied.

Preparation and Properties of Gelatin-Chitosan/Montmorillonite Drug-loaded Microspheres

A kind of slow release drug-loaded microspheres were prepared with gelatin, chitosan and montmorillonite（MMT） by an emulsification/chemical cross-linking method using glutaraldehyde as cross-linking agent and acyclovir as model drug. The microspheres were characterized by X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） and scanning electron microscopy （SEM）, respectively. The morphology, drug content, encapsulation efficiency and drug-release behavior were investigated with different MMT contents. The experimental results indicated that intercalated microspheres could be prepared, the morphology of microspheres was markedly affected by MMT. The glomeration performance of uncross-linked microspheres was improved because of the physical cross-linking of MMT. Drug content and encapsulation efficiency were decreased when increased the content of MMT, but burst release and the drug release were significantly decreased with the addition of MMT. Effective physical cross-linking could be formed when added MMT, and MMT could reduce the content of toxic chemical cross-linking agents.

Synthesis of ethyl acetate by esterification of acetic acid with ethanol over a heteropolyacid on montmorillonite K10

In present work,liquid phase esterification of acetic acid with ethanol over dodecatungestophosphoric acid （DTPA） supported on K10 montmorillonite was systematically studied and optimization of process parameters was carried out.The 20% m/m DTPA/K10 was found to be the optimum catalyst with 90% acetic acid conversion and 100% ethyl acetate selectivity.The study was also explored to see the feasibility of 20% m/m DTPA/K10 as a catalyst for the alkylation of acetic acid with other alcohols like methanol,iso-propanol and n-butanol.The 20% m/m DTPA/K10 has shown increased activity with the increase in carbon number,at the same alcohol reflux.The results are novel.

Photocatalytic remediation ofγ-hexachlorocyclohexane contaminated soils using TiO_2 and montmorillonite composite photocatalyst

TiO2 and montmorillonite composite photocatalysts were prepared and applied in degrading γ-hexachlorocyclohexane （γ-HCH） in soils. After being spiked with γ-HCH, soil samples loaded with the composite photocatalysts were exposed to UV-light irradiation. The results indicated that the photocatalytic activities of the composite photocatalysts varied with the content of TiO2 in the order of 10%〈70%〈50% 〈30%, Moreover, the photocatalytic activity of the composite photocatalysts with TiO2 content 30% was higher than that of the pure P25 with the same mass of TiO2. The strong adsorption capacity of the composite photocatalysts and quantum size effect may contribute to its increased photocatalytic activities. In addition, effect of dosage of composite photocatalysts and soil pH on γ-HCH photodegradation was investigated. Pentachlorocyclohexene, trichlorocyclohexene, and dichlorobenzene were detected as photodegradation intermediates, which were gradually degraded with the photodegradation evolution.

DISPERSION AND TENSILE BEHAVIOR OF POLYPROPYLENE/MONTMORILLONITE NANOCOMPOSITES PRODUCED VIA MELT INTERCALATION

Most of the articles on polymer nanocomposites focus on the importance of chemistry used to modify the surface of the clay, usually montmorillonite (MMT), and characterization of the nano-scale structure obtained. The role and importance of processing were also discussed recently. However, few papers concerning the correlation between morphology of MMT and mechanical properties were published. In order to understand. the tensile behavior of PP/Montmorillonite (MMT) nanocomposites better, and to further improve the reinforcement efficiency, we first prepared the PP nanocomposites via direct melt intercalation using conventional twin-screw extrusion. The dispersion and tensile property of the composites were then investigated by SEM, XRD, TEM and a video-controlled tensile set-up. The macroscopic and microscopic dispersion of MMT in PP matrix was verified by XRD and TEM, combined with SEM. The tensile properties were obtained by video-controlled tensile set-up, which gives true stress-strain curve. It was found that a partly intercalated and partly exfoliated structure (also called incomplete exfoliation) existed in the system. Though the tensile strength of PP nanocomposites is not much improved in engineering stress-strain curves, more than 20% increase of true stress was found in a true stress-strain experiment at high true strain, which indicates that only oriented silicate layers can have a big effect on tensile properties: Not only orientation of silicate platelets but also the degree of exfoliation is a key factor to determine the reinforcement efficiency. The reinforcement efficiency of MMT has been discussed based on the 'continuum' Halpin-Tsai equations. A good agreement was found between experimental data and theoretical prediction by changing N value (number of platelets per stack) which corresponding to different state of the dispersion of MMT in PP matrix.

Preparation and Properties of Phenolic Resin/Montmorillonite Intercalation Nanocomposites

Phenolic resin/montmorillonite intercalation composites were prepared by using the methods of pressing intercalation and melt intercalation.Properties and structure of the composites were investigated by using XRD,TG and test of softening point.It is indicated that both the pressing intercalation and melt intercalation can be used to prepare the phenolic resin/organo-montmorillonite intercalation nanocomposites.Compared with phenolic resin,the intercalation nanocomposites have better heat-resistance,higher decomposition temperatures and less thermal weight-loss.However,these two intercalation methods have different effects on the softening point of the intercalation nanocomposites.Pressing intercalation almost does not affect the softening point of the intercalation nanocomposites,while melt intercalation significantly increases the softening point of the intercalation nanocomposites, probably due to the chemical actions happening in the process of melt intercalation.

PROPERTIES AND MORPHOLOGY OF UNSATURATED POLYESTER/ACRYLATE-TERMINATED POLYURETHANE/ORGANO-MONTMORILLONITE NANOCOMPOSITES

Unsaturated polyester resin （UPR）/acrylate-terminated polyurethane （ATPU）/organo-modified montmorillonite （OMMT） nanocomposites were prepared by the in situ intercalative polymerization method. Samples were prepared by the sequential mixing, i.e. mixture of the ATPU and styrene （S） and OMMT were prepared in the first step; UPR was then added to the pre-intercalates of ATPU/S/OMMT. Results indicate that the mechanical properties and thermal properties of UPR/ATPU/OMMT nanocomposites greatly depend on the amount of ATPU and OMMT. Results show that the addition of ATPU could increase the impact strength of UPR/ATPU composites, but the tensile strength, flexural strength and heat resistance of the materials are obviously decreased. When the weight ratio between UPR, ATPU and OMMT were 82：15：3, the impact strength and heat distortion-temperature of nanocomposite were greatly improved, meanwhile there was little change for other properties of the nanocomposites. The synergistic enhancement effects of ATPU and OMMT on the composites were observed. The structures and morphology of the composites were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

Atomic and electronic structures of montmorillonite in soft rock

Montmorillonite is a kind of clay mineral which often causes large deformation in soft-rock tunnel engineering and thus brings about safety problems in practice.To deal with these engineering safety problems,the physical and chemical properties of montmorillonite should be studied from basic viewpoints.We study the atomic and electronic structures of montmorillonite by using density-functional theory within the local-density approximation （LDA）.The results of calculation show that Al-O bond lengths are longer than Si-O bond lengths.It is found that both the valence band maximum （VBM） and the conduction band minimum （CBM） of montmorillonite are at point Г,and the calculated direct band gap of montmorillonite is 5.35 eV. We show that the chemical bonding between cations and oxygen anions in montmorillonite is mainly ionic,accompanied as well by a minor covalent component.It is pointed out that the VBM and CBM of montmorillonite consist of oxygen 2p and cation s states,respectively.Our calculated results help to understand the chemical and physical properties of montmorillonite,and are expected to be a guide for solving the problem of large deformation of soft-rock tunnels.

Preparation and Characterization of Polylactide/Montmorillonite Nanocomposites

The montmorillonite, a form of layered silicate, was successfully intercalated into polylactide （PLA） matrix through solvent-casting technique. In addition, PLA/MMT nanocomposite films were produced, in which homogenous distribution of the silicate lamellae plays a key role in the mechanical properties of the films. A small amount（5wt%） of OMMT intercalated into the PLA matrix resulted in their flexibility enhancement, from 3.68%（pure PLA film） to 352.65%. The results of wide-angle X-ray diffraction （WAXD） patterns confirmed that the silicate interlayer distance increased from 3.044 nm （for OMMT） to 3.56nm （for 5wt%, maximum） with increasing OMMT contents, but decreased to 3.319 nm when OMMT content was over 8wt%. FT-IR also verified the molecular-level associations between PLA chains and OMMT lamellae by vibration variances of hydrogen bonding. DSC thermograms demonstrated that thermal stabilities of the nanocomposite films enhanced, due to the silicate lamellae dispersed into PLA matrix.

Preparation and characterization of mixed hydroxy-Fe-Al pillared montmorillonite with large basal spacing

Mixed hydroxy-Al-Fe pillared montmorillonites with large basal spacing were successfully prepared through cation-exchanging of Na +- montmorillonite with mixed hydroxy-Al and hydroxy-Fe pillaring solutions made from hydrolysis of corresponding metal salts, followed by calcination to convert hydroxy-Al and hydroxy-Fe into intercalated polycations. According to XRD analysis, the basal spacing d(001) of pillared products dramatically enlarged from 12.7 *! in the Na-montmorillonite to 81 *! in the hydroxy-Fe -montmorillonite and 77.5 *! in mixed hydroxy-Al-Fe-montmorillonite. The N_2 BET surface areas of the pillared montmorillonites also greatly increased to more than 200 m 2/g as compared to about 27 m 2/g for the Na-montmorillonite. IR analysis of hydroxy-Fe, and mixed hydroxy-Al-Fe pillared montmorillonites revealed a new absorption vibration at 1384 cm -1 wavelength. XRF elemental analysis data also showed a high content of Fe_2O_3 in the hydroxy-Fe pillared montmorillonite.

STRESS-INDUCED CRYSTALLIZATION OF POLYURETHANE/MONTMORILLONITE NANOCOMPOSITE

Exfoliated polyurethane/montmorillonite nanocomposites with both high elongation at break and high tensilestrength were studied by dynamic-infrared spectroscopy (dynamic-IR). The results show that crystallization induced byadditional stress is impeded by the nano-layered organo montmorillonite.

Modification of Montmorillonite through Intercalative Polymerization

Montmorillonite (MMT) was modified through intercalative polymerization of phenol and formaldehyde catalyzed by oxalic acid. The modified montmorillonite was delaminated at large, as demonstrated by XRD and TEM studies. It can disperse easily in epoxy resin to form exfoliated nanocomposites. The nanoscale silicate platelets dispersed in water can be metallized by silver deposition.

Swelling of K＋, Na＋ and Ca2＋-montmorillonites and hydration of interlayer cations： a molecular dynamics simulation

This paper performs molecular dynamics simulations to investigate the role of the monovalent cations K, Na and the divalent cation Ca on the stability and swelling of montmorillonite. The recently developed CLAYFF force field is used to predict the basal spacing as a function of the water content in the interlayer. The simulations reproduced the swelling pattern of these montmorillonites, suggesting a mechanism of their hydration different （K＋ 〈 Na＋ 〈 Ca2＋） from that of K＋-, Na＋-, and Ca2＋-montmorillonites. In particular, these results indicate that the valence of the cations has the larger impact on the behaviour of clay water systems. It also finds that the differences in size and hydration energy of K＋, Na＋ and Ca2＋ ions have strong implications for the structure of interlayer. This leads to the differences in the layer spacings of the simulated K＋-, Na＋-, and Ca2＋-montmorillonites. Furthermore, these simulations show that the K cations interact strongly with the clay sheets for the dehydrated clay sheets, but for the hydrated clays the Ca cations interact clearly strongly with the clay sheets.

Molecular Simulations of the Effect of Hydrated Montmorillonite on the Viscosity of Polyacrylamide under Confined Shear

Our researches are based on the fact that the systems composed of polyacrylamide and montmorillonite under a kind of shear state often appear in some important practical processes like drilling well etc. The viscosity of polyacrylamide is usually the most important one among the characteristics to decide if the practical processes succeed or not. Therefore, we studied the effect of hydrated montmorillonite on the viscosities of polyacrylamide with temperature and shear rate varying under confined shear by molecular simulation method. Adopting the condition of confined shear in the research could make our simulations and the practical processes as similar as possible. First, the model of one polyacrylamide polymer chain with 20 monomers linearly linking surrounded by water molecules between two of montmorillonite layers was constructed. Then canonical ensemble （NVT） MD simulations were carried out for the built model at different temperatures and shear rates. From the gained simulation results, we calculated the polymer＇s structural property-radius of gyration, which was directly related to the viscosity property of polyacrylamide polymer. It was found that the viscosity of the polyacrylamide polymer between hydrated clay layers decreased with the temperature increasing from 298 to 343 K under the condition of confined shear. The variation trend of viscosity from simulation results was also confirmed by our experiments. Besides, the viscosity of the polyacrylamide between hydrated clay layers decreased with the shear rate increasing within the range of higher shear rates.