MMT Layers Research Articles

A surface engineering strategy for the stabilization of zinc metal anodes with montmorillonite layers toward long-life rechargeable aqueous zinc ion batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) exhibit appreciable potential in the domain of electrochemical energy storage. However, there are serious challenges for AZIBs, for instance zinc dendrite growth, hydrogen evolution reaction (HER), and corrosion side reactions. Herein, we propose a surface engineering modification strategy for coating the montmorillonite (MMT) layer onto the surface of the Zn anode to tackle these issues, thereby achieving high cycling stability for rechargeable AZIBs. The results reveal that the MMT layer on the surface of the Zn anode is able to provide ordered zincophilic channels for zinc ions migration, facilitating the reaction kinetics of zinc ions. Density functional theory (DFT) calculations and water contact angle (CA) tests prove that MMT@Zn anode exhibits superior adsorption capacity for Zn2+ and better hydrophobicity than the bare Zn anode, thereby achieving excellent cycling stability. Moreover, the MMT@Zn||MMT@Zn symmetric cell holds the stable cycling over 5600 h at 0.5 mA cm−2 and 0.125 mA h cm−2, even exceeding 1800 h long cycling under harsh conditions of 5 mA cm−2 and 1.25 mA h cm−2. The MMT@Zn||V2O5 full cell reaches over 3000 cycles at 2 A g−1 with excellent rate capability. Therefore, this surface engineering modification strategy for enhancing the electrochemical performance of AZIBs represents a promising application.

Inflammation-oriented montmorillonite adjuvant enhanced oral delivery of anti-TNF-α nanobody against inflammatory bowel disease

Oral delivery of proteins faces challenges due to the harsh conditions of the gastrointestinal (GI) tract, including gastric acid and intestinal enzyme degradation. Permeation enhancers are limited in their ability to deliver proteins with high molecular weight and can potentially cause toxicity by opening tight junctions. To overcome these challenges, we propose the use of montmorillonite (MMT) as an adjuvant that possesses both inflammation-oriented abilities and the ability to regulate gut microbiota. This adjuvant can be used as a universal protein oral delivery technology by fusing with advantageous binding amino acid sequences. We demonstrated that anti-TNF-α nanobody (VII) can be intercalated into the MMT interlayer space. The carboxylate groups (-COOH) of aspartic acid (D) and glutamic acid (E) interact with the MMT surface through electrostatic interactions with sodium ions (Na+). The amino groups (NH2) of asparagine (N) and glutamine (Q) are primarily attracted to the MMT layers through hydrogen bonding with oxygen atoms on the surface. This binding mechanism protects VII from degradation and ensures its release in the intestinal tract, as well as retaining biological activity, leading to significantly enhanced therapeutic effects on colitis. Furthermore, VII@MMT increases the abundance of short-chain fatty acids (SCFAs)-producing strains, including Clostridia, Prevotellaceae, Alloprevotella, Oscillospiraceae, Clostridia_vadinBB60_group, and Ruminococcaceae, therefore enhance the production of SCFAs and butyrate, inducing regulatory T cells (Tregs) production to modulate local and systemic immune homeostasis. Overall, the MMT adjuvant provides a promising universal strategy for protein oral delivery by rational designed protein.

Tribological Effects of Quaternary Ammonium-Functionalized Montmorillonite as Water-Based Additives.

In this study, a water-soluble quaternary ammonium salt (QAS)-functionalized montmorillonite (MMT) was fabricated using a mechanochemical method as a high-performance water lubrication additive. The intercalation of QAS into the MMT layer expands the layer spacing of MMT, but does not affect the hydrophilicity of MMT. The ultrathin layer QAS-functionalized montmorillonite (QAS-MMT) demonstrated excellent water-stable dispersion and can be used as a water-based lubrication additive. Only 0.1% addition can reduce the friction coefficient by more than 71.4% and the wear volume by about 58.8% when compared to water, demonstrating its excellent friction reduction and antiwear performance. The frictional mechanism indicates that the physical adsorption film, together with the chemical reaction film, endows the QAS-MMT additives with outstanding tribological performance, provides excellent lubrication for the contact of steel/steel pairs, and prevents the steel surface from being further worn.

Insight on molecular interactions in shrinkage of Na-montmorillonite clay by molecular dynamics simulation

Expansive soils are known to be hazardous materials for infrastructure due to their high shrinking or swelling potential. Understanding the shrinking factors of expansive soils such as montmorillonite (MMT) is essential for predicting their mechanical properties. The interactions between the components of Na-MMT clays, e.g., MMT layer–layer (LL), layer–cation (LC), layer–water (LW) and water–cation (WC), are responsible for its shrinking behavior. In this study, molecular dynamics simulation and grand canonical Monte Carlo simulations are used to investigate the interaction energy evolution in the layered structure of Na-MMT for the shrinkage mechanisms analysis of clay. The results of simulation indicate that the magnitude of the interaction energy contributed by the interlayer cations dehydration is the driving force of the interlayer shrinkage. Furthermore, in the hydrated state, with one water layer, two water layers and three water layers, the attractive interactions between WC and LW, maintain the stability of the clay layers. However, at the dry state, the interaction energy between layers and cations appears to be the most essential component in holding the stacked layers together, which provides structural stability to the clay sheets. Finally, the study reveals that intermolecular interactions contribute to the mechanical properties of clays such as cohesive and elastic properties.

Preparation and investigation of TbCrO3/montmorillonite-K10 nanocomposite electrode for electrochemical hydrogen storage application

The limited resources of fossil fuels and the increase in human’s demand for energy have made the use of alternative green energies like hydrogen very important. In this regard, achieving superior specific capacity and high-performance electrochemical hydrogen storage requires the structural design and development of highly active electrode material with cooperative influence of “spillover”, “redox”, and “physisorption” mechanisms. The aim of this report is to fabricate a binary TbCrO3/montmorillonite-K10 (TC/MMT) nanocomposite and to skillfully ensure its electrochemical ability for hydrogen storage in 2.0 M KOH electrolyte, for the first time. A facile sonochemical strategy was presented to successfully form uniform orthorhombic TC nanoparticles with varying tetradentate Schiff base ligands derived from salicylaldehyde and relative diamines as well as the molar ratio of H2Salbn to Tb3+. Characterization analyses displayed that the nucleation and growth process of TC samples can be well controlled by a molar ratio of H2Salbn:Tb3+ = 1:1 within the range of 17–72 nm. Furthermore, implementation of a well-organized MMT-based nanocomposite with various amounts of nano-TC perovskites was evaluated on the structural and electrochemical features. The greatly enhanced hydrogen storage capacity of TC/MMT nanocomposites was acquired as 734.3 mAh/g after 15 cycles, when 10.0 % of perovskite oxide is induced by MMT layers. Moreover, architecture of pristine TC and MMT electrodes possessed a 936.87 and 341.52 mAh/g discharge capacities at the same situation. These merits allow a promising potential application of the nanocomposite electrodes containing rare-earth chromite oxide and clay substrates in electrochemical energy-storage devices.

Enhancing Zn2+ diffusion for dendrite-free zinc anodes via a robust zincophilic clay mineral coating

Clay minerals as artificial solid electrolyte interphase (SEI) layers have played a crucial role in protecting zinc metal anodes for aqueous Zn-ion batteries (AZIBs) due to their unique layered structure, negatively charged lamellas, ion exchange ability, and electronic insulation. However, the clay mineral layers exhibit limited ability to suppress dendrites and side reactions on the Zn anode in the water-based working environment. This limitation is attributed to the severe volumetric expansion, poor mechanical performance, and inferior zinc ion conductivity. To address these issues, montmorillonite (MMT) is intercalated with urea in this study. The resulting dense and robust UMMT coating layer enhances the diffusion of Zn2+ and increases the Zn2+ concentration at the Zn deposition surface through strong absorption of Zn2+ at −C=O and −NH2 active sites. As a result, it facilitates the uniform deposition of Zn2+ and inhibits dendrite growth. Additionally, the UMMT coating layer acts as a desolvation layer, mitigating parasitic reactions originated from active water. Consequently, the UMMT coating layer enables stable Zn plating/stripping compared to MMT layer. In symmetric cells, MMT@Zn electrode exhibits a significantly longer lifespan of over 1300 h at 6 mA cm−2 with a capacity of 3 mAh cm−2. Furthermore, it demonstrates enhanced cyclic performance of 254 mAh g−1 at 10 A g−1 after 4000 cycles in Zn//V2O5 full cells. This present work presents a strategy to intercalate small-molecule organics into clay minerals, enhancing their protective capacity and expanding their application as SEI layers in AZIBs.

The Influence Mechanism of Interfacial Characteristics between CSH and Montmorillonite on the Strength Properties of Cement-Stabilized Montmorillonite Soil.

To elucidate the impact mechanism of the interfacial characteristics of Calcium Silicate Hydrate gel (CSH)-Montmorillonite (MMT) at the nanoscale on the strength of cement-stabilized montmorillonite soil, this paper begins by examining the interfacial energy. Through Molecular Dynamics (MD) simulation methods, the energy at the MMT and CSH binding interface is quantitatively calculated, and the correlation between the interfacial energy and macroscopic strength is determined in conjunction with grey relational analysis. Finally, based on the characterization results from X-ray diffraction (XRD), the accuracy and sources of deviation in the MD simulation results are discussed. The study shows the CSH-MMT interfacial energy is composed of van der Waals forces, hydrogen bond energy, and electrostatic interactions, which are influenced by the migration of cations; there is a good consistency between the CSH-MMT interfacial energy and the unconfined compressive strength (UCS) of cement-stabilized soil (cemented soil), with the interfacial energy decreasing as the number of water molecules increases and first decreasing then increasing as the number of MMT layers grows; by adjusting the mix proportions, the magnitude of the CSH-MMT interfacial energy can be altered, thereby optimizing the strength of the cemented soil.

Chitosan-Pd0 nanoparticles encapsulated in Al, Co-pillared montmorillonite by one-pot process

Chitosan-Pd0 (CS-Pd0) nano particles encapsulated in Al, Co-pillared montmorillonite (MMt) nanocomposites were synthesized by a facile one-pot heat treatment method. The MMt was impregnated with Al, Co pillaring reagent, protonated chitosan solution, and Na2PdCl4 solution, followed with a controlled low-temperature (200 °C) heat treatment, resulting in Pd@CS/Al, Co-MMt nanocomposites. Al, Co pillaring effectively expanded the basal spacing of MMt layers from 1.24 nm to 1.82 nm, and generated numerous mesopores in interlayer space, resulting in increase of surface area from 11.8 m2/g to 198.3 m2/g. Due to the well encapsulation of CS chains in the interlayer nano-spaces, the specific surface area of the hybrid nanocomposite underwent a reasonably decrease as the CS content increase. Most of nano-sized Pd species (2–3 nm) chelated with CS chains dispersed well in the interlayer space of the porous Al, Co pillared MMt matrix. The resultant nanocomposite prepared by such facial one-pot process method have similar high comprehensive catalytic performances as applied in coupling reactions to that prepared by regular divided-multistep method. Moreover, it is confirmed that Al pillaring doped with Co and encapsulation of CS chains have synergistic improving effects on the comprehensive catalytic performance of the nanocomposites.

Investigation of the structural, magnetic and dielectric properties of NiFe2O4/nanoclay composites synthesized via sol-gel autocombustion

NiFe2O4 nanoparticles supported with 0, 2, 4, and 6 wt% of dodecylalkylammonium intercalated montmorillonite (DDA-MMT) are synthesized by sol-gel autocombustion method. The structural and morphological properties have been analyzed by XRD, FTIR and SEM techniques. The dielectric, magnetic, optical and electrical properties of the prepared samples have been evaluated. XRD analysis confirmed the formation of MMT layers exfoliated NiFe2O4 nanoparticles by showing the absence of 001 reflection of DDA-MMT in NiFe2O4/DDA-MMT compounds. The crystallite size is determined to be 31.32 nm for naked Ni ferrite and decreases with increase of DDA-MMT content, which revealed crystallization of NiFe2O4 is influenced by DDA-MMT. The saturation magnetization of Ni ferrite is found to be increased from 29.84 emu/g to the range of 30.78–38.45 emu/g when supported with DDA-MMT up to 6 wt%. A significant enhancement of dielectric constant, from 2.7 to 4.2, is observed when Ni ferrite is supported with 2 wt% DDA-MMT which could be accounted for interfacial polarization between MMT layers and ferrite nanoparticles. Optical band gap increases from 1.67 to 1.76 eV with application of 2 wt% DDA-MMT as supporting material in Ni ferrite. Present work indicates that the magnetic, dielectric, optical as well as electrical properties of Ni ferrite nanomaterial may be modified by adding the right quantity of DDA-MMT as a supporting material, which will ultimately assist in broadening the uses of Ni ferrite.

Study on the cracking mechanism of strongly weathered purple mudstone under wetting and drying effect through experiments and molecular dynamics simulation

This study aims to investigate the cracking mechanism of strongly weathered purple mudstone (SWPM) samples in Three Gorges Reservoir (TGR) drawdown area, China under wetting and drying (WD) effect. The surface morphology and internal meso-structure changes of SWPM samples were observed by laboratory WD experiments and X-ray computed tomography (CT). Then, the Hyperspectral imaging (HSI) was conducted to explore the mineral components and mineral distribution on the crack sidewalls of the SWPM samples under WD effect, and the Atomic Force Microscopy (AFM) was applied to obtain the height profile of montmorillonite (MMT) on the surface of crack sidewalls based on HSI results. Subsequently, the molecular models contained clay mineral model and non-clay minerals model were established according to HSI analysis. The results showed that the cracks evidently appeared on SWPM surface after WD tests, the initial cracks in the mudstone sample extended continuously and connected pores increased rapidly under WD effect through CT images analysis. The hyperspectral images showed that the montmorillonite, albite and quartz were the main minerals of SWPM cracks area, the montmorillonite was the primary component of clay minerals, and the AFM images illustrated the existence of five layers of montmorillonite crystal layers on the montmorillonite region of the crack sidewalls. The MD simulation revealed that the interaction energy of SiO2 - MMT layers and MMT-MMT layers decreased with the increase of water content, and the electrostatic energy accounted for most of the energy. In wet condition, the distance of SiO2-MMT layers and MMT-MMT layers was raised with the swelling of montmorillonite due to the water intrusion. In dry condition, as the amount of water diminished, the MMT layers were close to each other and the spacing was shrinking, while the distance between MMT and SiO2 expanded continuously. The extension of the spacing SiO2-MMT layers in the dehydrated state was considerably more superior than that in the water absorption state, with the large apparent distance emerging between SiO2 and MMT, which illustrating the adjacent area of montmorillonite and detrital mineral in SWPM can easily appear microcracks under WD effect. This work directly explained the interaction behavior of SiO2-MMT layers and MMT-MMT layers at the molecular level, which provided a new perspective to comprehend the cracking process of strongly weathered purple mudstone in the TGR area.

Intelligent cyclic fire warning sensor based on hybrid PBO nanofiber and montmorillonite nanocomposite papers decorated with phenyltriethoxysilane

An abundance of early warning graphene-based nano-materials and sensors have been developed to avoid and prevent the critical fire risk of combustible materials. However, there are still some limitations that should be addressed, such as the black color, high-cost and single fire warning response of graphene-based fire warning materials. Herein, we report an unexpected montmorillonite (MMT)-based intelligent fire warning materials that have excellent fire cyclic warning performance and reliable flame retardancy. Combining phenyltriethoxysilane (PTES) molecules, poly(p-phenylene benzobisoxazole) nanofiber (PBONF), and layers of MMT to form a silane crosslinked 3D nanonetwork system, the homologous PTES decorated MMT-PBONF nanocomposites are designed and fabricated via a sol–gel process and low temperature self-assembly method. The optimized nanocomposite paper shows good mechanical flexibility (good recovery after kneading or bending process), high tensile strength of ∼81 MPa and good water resistance. Furthermore, the nanocomposite paper exhibits high-temperature flame resistance (almost unchanged structure and size after 120 s combustion), sensitive flame alarm response (∼0.3 s response once exposure onto a flame), cyclic fire warning performance (>40 cycles), and adaptability to complex fire situations (several fire attack and evacuation scenarios), showing promising applications for monitoring the critical fire risk of combustible materials. Therefore, this work paves a rational way for design and fabrication of MMT-based smart fire warning materials that combine excellent flame shielding and sensitive fire alarm functions.

Synergistic Improvement in γ-Phase Content and Dielectric Properties of PVDF/Deep Eutectic Solvent/Montmorillonite Composite Films

The high dielectric constant of PVDF is very important for its high-performance energy storage dielectrics, but it is more critical to strike a proper balance between high dielectric constant and low dielectric loss. In this work, deep eutectic solvent (DES) and montmorillonite (MMT) have been used together to prepare γ-phase PVDF composite films with excellent dielectric properties. It is found that DES significantly induces crystallization of γ-phase and increases the dielectric constant of the composite due to the incremental ion motion. Meanwhile, DES greatly promotes the stripping and dispersion of MMT layers, which in turn inhibits the long-range ion migration and therefore suppresses the dielectric loss of the composite to a very low level. The dielectric constant of PVDF/MMT/DES composite films can increase to 32, while the dielectric loss remains as low as 0.06 at 1 kHz. Moreover, the synergistic effect of MMT/DES also contributes to enhancing the toughness and optical transmittance of composite films.

Photochemical degradation of perfluorooctanoic acid under UV irradiation in the presence of Fe (III)-saturated montmorillonite

Perfluorooctanoic acid (PFOA) has attracted worldwide attention owing to its widespread distribution and potential ecological risks. Developing low-cost, green-chemical and highly efficient treatment approaches is significant for treating PFOA caused environmental issues. Herein, we propose a feasible PFOA degradation strategy under UV irradiation by adding Fe (III)-saturated montmorillonite (Fe-MMT), and the Fe-MMT could be regenerated after reaction. In our system consisting of 1 g L−1 Fe-MMT and 24 μM PFOA, nearly 90 % initial PFOA could be decomposed within 48 h. The enhanced PFOA decomposition could be explained by the ligand-to-metal charge transfer mechanism based on the generated reactive oxygen species (ROSs) and the transformation of iron species in the MMT layers. Moreover, the special PFOA degradation pathway was revealed according to the intermediate identification and the density functional theory calculation. Further experiments demonstrated that even in the presence of co-existing natural organic natter (NOM) and inorganic ions, efficient PFOA removal could still be obtained in UV/Fe-MMT system. This study offers a green-chemical strategy for PFOA removal from contaminated waters.

Graphene Oxide-Intercalated Microbial Montmorillonite to Moderate the Dependence of Nafion-Based PEMFCs in High-Humidity Environments

The most fatal disadvantage of Nafion-based proton-exchange membrane fuel cells (PEMFCs) is their significant performance losses at low relative humidities (RH ≤ 80%), making external humidification necessary. In this work, a graphene oxide (GO)-intercalated microbial montmorillonite (mMMT) layered stack (GO@mMMT) was prepared to enhance the proton conductivity of a Nafion membrane under a low humidity at elevated temperatures. The prepared mMMT had a high specific surface area and pore volume due to microbial mineralization, allowing GO to act as a spacer intercalated between MMT layers. This layered stack greatly enhanced the water absorbance and retention capacity of GO@mMMT/Nafion composite membranes. The GO@mMMT/Nafion composite membrane exhibited excellent proton conductivity under various humidities. Particularly, the 0.5GO@mMMT/Nafion sample achieved a proton conductivity of 36.4 mS·cm–1 at 80 °C/98% RH and 17.3 mS·cm–1 at 80 °C/20% RH, which was 82% and 188% higher than that of the recast Nafion membrane, respectively. The assembled single cell reached a peak power density of 546 mW·cm–2, which was 60% higher than that of the recast Nafion single cell. These results indicate that the Nafion composite membranes with GO@mMMT incorporated layered stacks show substantial potential for PEMFC applications with simplified water management.

Iron Metal Ion Adsorption Capacity on Palm Oil Mill Effluent (POME) Using Montmorillonite Adsorbent

Palm oil mill effluent (POME) is the most produced waste among other types of waste, which is around 60% in every 100% processing of fresh fruit bunches containing heavy metals, namely ferrous metal (Fe). Montmorillonite (MMT) is one of the best adsorbents used to reduce the concentration of Fe in POME. In addition, this mineral (MMT) also has a high cation fertilization capacity so that the space between layers of MMT is able to accommodate large amounts of cations and make MMT a unique material. In this review, the assurance of the mass variety of the MMT as adsorbent and the variety of the contact time on the adsorption capacity of Fe metal in POME was resolved utilizing a Atomic Absorption Spectrophotometer (AAS) and surface morphology analysis of MMT before and after adsorption using Scanning Electron Microscope (SEM). Based on the results of AAS analysis, the greater the mass of the adsorbent, the higher the amount of Fe adsorbed from the POME. Moreover, the longer the contact time between MMT and Fe, the higher the amount of Fe in the palm oil mill effluent adsorbed on the adsorbent surface. The best adsorption conditions occurred at an adsorbent mass of 8.5 g MMT in 50 mL adsorbate and a contact time of 5 hours with an adsorption capacity of 0.0383 mg/g. The results of the SEM showed the presence of empty spaces in the MMT before adsorption, in which after adsorption white granules occupies the empty spaces evenly on the surface of the MMT. The granules indicate the presence of Fe metals in the POME samples which are adsorbed on the MMT surface.

Robust superhydrophobic and flame-retardant coatings based on hierarchical epoxy textured with gas barrier structure; efficient oil-water separation devices under extreme conditions

Inspired by the biomaterial nacre, we report a versatile and facile strategy to rugged, flame retardant superhydrophobic materials by embedding a nacre-like montmorillonite (MMT) based gas barrier layer into hierarchical epoxy-resins. The well-aligned MMT layer imparted excellent oxygen and water barrier properties that rendered the coating surface water repellent yet protected the substrate materials from fire by suppressing heat and oxygen transfer. The hierarchical epoxy not only provided the robust superhydrophobic structure but offered strong adhesion to MMT layer. After application of this coating to a flammable sponge, it demonstrated superhydrophobicity with a contact angle of ∼153°. Furthermore, the material was rugged, resisting 1200 compression cycles and induced marked flame retardancy. The coated sponge delayed ignition (689% delay in ignition time) and promoted significant flame extinguishing property, compared with the uncoated material (demonstrated by LOI, CONE combustion, and fire scenario tests). Owing to its robustness and multifunctionality, the coated sponge was able to efficiently separate oil from multi-environments including strong corrosive, icy, boiling or vibrating mixtures. Additionally, the versatile application to wood, cotton, textile and other lignocellulosic substrates has been verified. This research opens up a new direction for durable waterproof and fireproof materials.

Carboxymethyl cellulose/montmorillonite bionanocomposite films incorporated with polyhedral oligomeric silsesquioxane

ABSTRACT In this work, carboxymethyl cellulose (CMC)/montmorillonite (MMT) bio-nanocomposite films were prepared by intercalating MMT with polyhedral oligomeric silsesquioxane (POSS) to promote the interfacial interactions between CMC and MMT and overcome limitations of CMC such as its moisture barrier property, thermal, and mechanical properties with maintaining its transparency, biocompatibility, and film-forming ability, etc. POSS combined with ammonium and imidazolium groups (POSS-ammonium and POSS-imidazolium) were prepared by the hydrolysis of organic silane compounds and intercalated into MMT via an ion-exchange reaction. MMT intercalated with POSS-ammonium and POSS-imidazolium are designated as MOAP and MOIP, respectively. MMT modified with POSS-imidazolium (MOIP) was adequately dispersed in the polymer matrix owing to the increased gap between the MMT layers and electrostatic interaction between POSS at the MMT edge and carboxylate moieties on CMC chain. The good compatibility and interaction between MOIP and CMC as well as higher thermal stability of heterocyclic compound in POSS-imidazolium endowed the bionanocomposite films with excellent mechanical properties and thermal stability. Furthermore, UV-barrier, moisture barrier, antibacterial, and antioxidant properties of the CMC bionanocomposite films were effectively improved with the introduction of MOIP.

Percolation Network Formation in Nylon 6/Montmorillonite Nanocomposites: A Critical Structural Insight and the Impact on Solidification Process and Mechanical Behavior.

The incorporation of montmorillonite (MMT) into Nylon 6 can endow advantages like improved mechanical strength and thermal stability, making Nylon 6/MMT a possible ideal alternative for Nylon 66. However, the relationship between the microstructure and physical properties of nylon 6/MMT nanocomposites is unclear so far due to the complicated system, including the highly asymmetric geometry of the exfoliated MMT layer and the complicated interaction between MMT layers and entangled nylon 6 chains. Herein, we focus on two processes, namely the impact of MMT on the solidification procedure during molding and the toughness–brittleness transition during the tensile stretch, in order to elucidate the structure–property relationship of nylon 6/MMT composites. We firstly studied the solidification process of nylon 6/MMT with bending height experiments. The results showed that the solidification process occurs prior to the crystallization of nylon 6, indicating that a physical crosslinked network rather than a crystalline structure is the reason for the solidification process. Furthermore, the solidification speed has a step change at around 2 wt% MMT content, indicating that the MMT percolation network is related to the transition. We further studied the influence of MMT inclusion on the mechanical properties, and found the tensile strain at break showed a similar step change at around 2 wt% MMT content, which further confirms the existence of an MMT percolation network above 2 wt% MMT content. It was generally believed that the main effect of MMT on nylon 6 is the nanofiller enforcement; we found that the percolation effect of the highly asymmetric 2-D nanofiller plays a central role in influencing the mechanical properties and solidification behavior during molding.

Efficient polysulfides trapping and redox enabled by Co/N-carbon implanted Li+-montmorillonite for advanced lithium-sulfur batteries

Li-S batteries are very promising next-generation energy storage systems due to their high theoretical capacity and energy density, but suffer from sluggish redox kinetics and serious polysulfides (PS) shuttle. Herein, Co/N-carbon implanted Li+-montmorillonite (Co/NC@Li-MMT) is designed to inhibit PS shuttle and maximize PS redox kinetics in Li-S battery. The Co/NC@Li-MMT 2D nanomaterial is fabricated by exfoliation of the Li-MMT nanosheets using melamine and Co(II)(acac)2, followed by one-step thermal reduction. The exfoliated Co/NC@Li-MMT with high Li+ and electrical conductivity can expose abundant active sites for efficient PS adsorption via Co-S and Si-S and Li bonds and for fast PS electrocatalytic conversion via Co and CoNC catalytic active sites. The Co/NC@Li-MMT modified PP (Co/NC@Li-MMT@PP) separator with a thin Co/NC@Li-MMT layer of 2.2 μm (0.3 mg cm−2 mass loading) features high Li+ conductivity, fast Li+ diffusion, superior electrolyte wettability as well as efficient PS trapping and fast PS redox kinetics as verified by various analytical techniques. Consequently, the Li-S battery with the Co/NC@Li-MMT@PP separator shows high initial capacity (1447 mAh/g), good rate performance, excellent cycling stability (0.027 % capacity fade per cycle at 1C over 300 cycles) and ultralow self-discharge.

Preparation and Characterization of TCPP-CaMMT Nanocompound and Its Composite with Polypropylene.

Based on the molecular dynamics method, the tris-(1-chloropropan-2yl) phosphate (TCPP)/montmorillonite (MMT) molecular model was established to study the binding energy and microstructure changes in TCPP and MMT. The theoretical simulation results showed that TCPP can enter the MMT layer and increase the layer spacing. From this, an organic intercalated Ca-montmorillonite TCPP-CaMMT was prepared by a very simple direct mixing method using flame retardant TCPP as a modifier. Polypropylene (PP) composites were prepared by TCPP, CaMMT, and TCPP-CaMMT. The microstructures of TCPP-CaMMT nanocompounds and PP composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results showed that TCPP-CaMMT nanocompounds could be exfoliated into nanosheets in PP. The flame retardancy and mechanical properties of PP/TCPP-CaMMT samples were studied by limited oxygen index (LOI) measurements and tensile tests. The PP/TCPP-CaMMT composites showed better LOI, tensile strength, and elongation at break than the machine-mixed PP/TCPP + CaMMT.