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Ferroelectric tunnel junctions (FTJs) as the artificial synaptic devices have been considered promising for constructing brain-inspired neuromorphic computing systems. However, the memristive synapses based on the flexible FTJs have been rarely studied. Here, we report a flexible FTJ memristor grown on a mica substrate, which consists of an ultrathin ferroelectric barrier of BiFeO3, a semiconducting layer of ZnO, and an electrode of SrRuO3. The obtained flexible FTJ memristor exhibits stable voltage-tuned multi-states, and the resistive switchings are robust after 103 bending cycles. The capability of the FTJ as a flexible synaptic device is demonstrated by the functionality of the spike-timing-dependent plasticity with bending, and the accurate conductance manipulation with small nonlinearity (−0.24) and low cycle-to-cycle variation (1.77%) is also realized. Especially, artificial neural network simulations based on experimental device behaviors reveal that the high recognition accuracies up to 92.8% and 86.2% are obtained for handwritten digits and images, respectively, which are close to the performances for ideal memristors. This work highlights the potential applications of FTJ as flexible electronics for data storage and processing.

Modern electronics and electric power grids require high performance polymer-based dielectric nanocomposites. To realize large-scale applications, the energy density of nanocomposites needs to be further increased. Here, we demonstrate a remarkable improvement in energy density of poly(vinylidene fluoride) (PVDF) matrix upon the incorporation of high-κ Bi4.2K0.8Fe2O9+δ (BKFO) nanobelts. High aspect ratio BKFO nanobelts can enhance the Young's moduli of the nanocomposites and increase the path tortuosity of electrical trees, which are favorable for increasing the breakdown strength of the system. Thus, the dielectric constant and breakdown strength increase simultaneously at a low volume fraction (0.35 vol%) of BKFO nanobelts, and an ultrahigh recoverable energy density of 25.4 J/cm3 is achieved. These results provide a strategy to develop high performance flexible high-energy-density devices. Keywords: Dielectric nanocomposite, Energy storage, Nanobelt, Breakdown strength

Next-generation non-volatile memories with ultrafast speed, low power consumption, and high density are highly desired in the era of big data. Here, we report a high performance memristor based on a Ag/BaTiO3/Nb:SrTiO3 ferroelectric tunnel junction (FTJ) with the fastest operation speed (600 ps) and the highest number of states (32 states or 5 bits) per cell among the reported FTJs. The sub-nanosecond resistive switching maintains up to 358 K, and the write current density is as low as 4 × 103 A cm−2. The functionality of spike-timing-dependent plasticity served as a solid synaptic device is also obtained with ultrafast operation. Furthermore, it is demonstrated that a Nb:SrTiO3 electrode with a higher carrier concentration and a metal electrode with lower work function tend to improve the operation speed. These results may throw light on the way for overcoming the storage performance gap between different levels of the memory hierarchy and developing ultrafast neuromorphic computing systems., Memristor devices based on ferroelectric tunnel junctions are promising, but suffer from quite slow switching times. Here, the authors report on ultrafast switching times at and above room temperature of 600ps in Ag/BaTiO3/Nb:SrTiO3 based ferroelectric tunnel junctions.

Inorganic nanomaterials exhibit superior friction-reduction and anti-wear properties in oils. In this study, 2D layered α-zirconium phosphate (α-ZrP) nanosheets intercalated with different amines have been synthesized to study their dispersion stabilities in lubricating oil and tribological applications. The intercalated amines should be sufficiently long and lipophilic to provide stabilization to α-ZrP nanosheets in mineral oil. The results of tribological tests illustrate that with the addition of well-dispersed nanosheets, the coefficient of friction (COF) and pin volume loss reduce by ~47% and 75%, respectively. The excellent dispersion stability enables the nanosheets to flow into the contact area at the beginning, and thereby protect the rubbing surface. A reduction in the van der Waals forces between the adjacent layers induced by the intercalated amines transforms the friction between adjacent layers from pin disk to sliding, leading to a decrease in the COF under hydrodynamic lubrication. The study provides a new method to enhance the tribological properties via tuning the dispersion stabilities of nanomaterials in oils.

Two-dimensional (2D) layered nanomaterials, including pristine α-zirconium phosphates (ZrP), amine-intercalated organophilic α-zirconium phosphates (OZrP) and organophilic montmorillonite (OMMT), are directly incorporated into linear low density polyethylene (LLDPE) by injection molding. ZrP and OZrP achieve good dispersion in the LLDPE matrices while OMMT forms agglomerations as observed by scanning electron microscope (SEM). The differential scanning calorimetry (DSC) analysis reveals that well-dispersed ZrP and OZrP could act as a nucleating agent to increase crystallinity of LLDPE while the agglomerated OMMT decreases the crystallinity of the polymer matrix. Tensile tests show that the strength and ductility of the LLDPE/ZrP nanocomposites can be enhanced simultaneously, due to the high modulus and parallel alignment along the injection direction for ZrP in matrix. The heat resistance of LLDPE, can also be enhanced by the addition of 2D nanoplatelets, among which ZrP perform the best, showing an increase of ∼16 °C in heat distortion temperature.

The large-area preparation of excellent lubricating materials with good resistance to leakage and an oxidation atmosphere and ease of replenishment has remained a challenge. Here, inspired by the N...

Hydrophobic graphite fluoride (GrF)-reinforced epoxy coatings are fabricated on steel substrate with a simple, solventless, and surfactant-free approach. The contact angle can be enhanced from 72° ...

Graphite fluoride (GrF) platelets were directly incorporated into polyamide 6 (PA6) by simple melt processing without using any surfactant. Due to the hydrogen bonding interaction between the filler and the matrix, GrF at a low loading shows good dispersion and partial exfoliation in PA6, as illustrated by scanning electron microscope and X-ray diffraction (XRD) measurements. The XRD results also reveal that the dominant γ-crystal in the neat PA6 converts to a relatively high content of α-crystal in the composites. Moreover, GrF has been found to be able to promote the mobility of the PA6 molecular chains, then favors the formation of α-crystal. Differential scanning calorimetry analysis demonstrates that GrF can act as heterogeneous nucleation agents to improve the onset of the crystallization temperature of PA6. Furthermore, tensile tests show that PA6 with 0.5 wt% GrF has an optimal improvement in elastic modulus and tensile strength by about 21.4% and 9.8%, respectively. Our current studies illustrate that good dispersion and partial exfoliation of GrF platelets in PA6, good adhesion between GrF and PA6, and more stable α-crystal formed in the matrix together contribute to the high-performance of the PA6/GrF composites at a low filler loading.

Epoxy composites with excellent toughness and strength have been successfully fabricated by direct incorporation of graphite fluoride (GrF) without using any solvent or surfactant modification. Owing to the strong interfacial interactions, the glass transition temperature of GrF/epoxy composites exhibits a significant improvement as observed by dynamic mechanical analysis. Mechanical characterizations on GrF/epoxy composites suggest that the optimal increase of tensile strength and Young's modulus is achieved at a low filler concentration of 0.5 wt%, which is attributed to the favorable level of the GrF dispersion in the epoxy matrix. A maximum toughening effect is obtained at the concentration of 1 wt% GrF in the epoxy matrix with a 1.5-fold improvement in fracture toughness. The generation of crack pinning and crack deflection in epoxy due to the existence of GrF platelets is proposed to be the main toughening mechanism. Besides, microcracks resulted from pulling out, layer breakage and interfacial debonding of GrF platelets also contribute to the improvement in the fracture toughness of GrF/epoxy composites.

In this paper, the correlation of the interfacial molecular array behavior of sugar-based green surfactant dodecyl maltoside DDM, and its apparent foam properties was investigated by molecular dynamics simulation and quantum chemical calculation as well as experimental methods. A common nonionic surfactant nona-ethylene glycol dodecyl ether C12E9, which has same hydrophobic tail and similar O atom number in headgroup with DDM, was studied as a reference. It was found that, not only the array behaviors of hydrophilic groups of DDM and C12E9 at the air-water interface, but also the intermolecular interactions were quite different. The simulation finding agreed well with the experimental results, by which how the interfacial molecular array behavior of the two types of nonionic surfactants affect the foam properties was revealed, and the application potential of DDM being used as foam stabilizer under diverse harsh conditions, such as high salinity, high temperature, strong acid and alkali, was presented, which should be quite meaningful.

Highly transparent hydrophobic coatings with scratch-resistant property attract tremendous interest from both scientific research and practical applications. The present study demonstrates that hydrophobic coatings with high transmittance and anti-scratch performance on glass substrates can be easily created by dewetted epoxy structures in large scale, followed by the attachment of a low surface energy material. The influence of epoxy solution concentrations on the surface dewetted structures, as well as the hydrophobicity and transmissivity of glass substrates were investigated. It was found that the epoxy solution concentration of 5% combined with a low surface energy material coating on glass exhibited the highest contact angle of ∼113°. UV–vis spectrum studies indicated that the coatings fabricated by our method had almost the same transmittance as that of the glass substrate. In addition, nano-scratch test illustrated that the prepared coating was capable of delaying crack generation, further strengthening the glass surfaces. Furthermore, our approach also facilitates the large-scale fabrication of hydrophobic anti-scratch coatings on glass as demonstrated by the preparation of mobile phone screen coatings. The detailed mechanism of large-scale hydrophobic coatings on glass with high transmission and anti-scratch performance was carefully elaborated.

In the wide application of aqueous foam, creating abundant foam and processing appropriate foaming control are both essential, depending upon the actual situation; the latter process is not only harder to achieve, but also more complicated to comprehensively understand on the molecular level. In this paper, a type of natural flavor oil, carvone, was solubilized in a micelle solution of sodium dodecyl sulfate (SDS) to study the effect on the foaming properties. The foamability and foam stability of the swollen micelle solutions were experimentally characterized, and the molecular behavior of the surfactant and oil molecules before, during and after the foaming process were investigated. It was found that the solubilized carvone co-adsorbed with SDS at the gas/water interface and caused a prominent effect on the foam film stability in several approaches, thereby making the flavor oil a possible foam controller that would not inhibit foam formation, but could eliminate foam efficiently once foam was undesired. Interestingly, it was found that the release of flavor in the foaming process was promoted. Detailed discussion of the interfacial behavior of carvone and the effect on the foaming properties of surfactants in different stages of foam may provide a theoretical foundation for exploring green and smart approaches in achieving foaming control.

CO2 capture and sequestration (CCS) is recognized as one of the most promising alternatives to weaken the greenhouse effect, and nanoporous materials are regarded as the promising candidates; therefore, developing a new cost-effective sorbent to achieve CCS is crucial. In this study, asphaltene-based slit nanopores were used to simulate capturing of CO2 from flue gas. The grand canonical Monte Carlo and molecular dynamics simulation methods were employed to examine the microscopic behaviors of CO2 and N2 in asphaltene slit nanopores. The isosteric heat of CO2 and N2 molecules adsorbed in asphaltene slit nanopores, the adsorption energy of a single molecule of CO2 and N2 adsorbed on the surface of asphaltene fragments, and the self-diffusion of CO2 and N2 molecules adsorbed in asphaltene slit nanopores were examined. Strong competitive adsorption of CO2 over N2 is found in a broad range of temperatures and pressures, and it was found that the temperature plays an important role on the competitive adsorptio...

Molecular dynamics simulation studies were employed to investigate the microscopic behaviors of CH4 and CO2 molecules in slit-nanopores (SNPs) with various surfaces and different compositions. Three kinds of SNPs were constructed by a pair-wise combination of graphene, silica, and the calcite surface. The grand canonical Monte Carlo and molecular dynamics simulation methods were used to investigate the adsorption and self-diffusion of the gases in the nanopores. It is found that in all three cases, the CH4 molecules prefer to adsorb onto the graphene surface, whereas the CO2 molecules prefer to adsorb onto the calcite surface. The adsorption intensity of gases adsorbed onto various surfaces, the adsorption distances, along with the details of adsorption orientations of CH4 and CO2 molecules on various surfaces are calculated. The surface characteristics, such as surface roughness and charge distribution, are analyzed to help understand the microscopic adsorption behaviors of the gases on the specific surface. It was found that competitive adsorptions of CO2 over CH4 broadly occurred, especially in the SNPs containing calcite, because of the strong adsorption interactions between the CO2 molecules and the calcite surface. This work provides the microbehaviors of CH4 and CO2 in SNPs with various surfaces in different compositions to provide useful guidance for better understanding about the microstate of gases in complex nanoporous shale formation and to give out useful guidance for enhancing shale gas recovery by injecting CO2.

Understanding about molecular behaviors in microscopic level is always important for not only finding out the natural principles, but also deciding how to solve the problems in application. In this study, the grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were employed to investigate the adsorption and diffusion properties of CH4 and CO2 in silica nanopores with different sizes, and the displacement of residual CH4 in silica nanopores by CO2 at a constant temperature of 323 K and various pressures was studied. It is found that, the microscopic molecular states of the adsorbed CH4 and CO2 in nanopores with various size are different. Competitive adsorption of CO2 over CH4 broadly occurs due to the different intensity of interactions between the gases molecules and the pore surface, of which the degree decreases with the pore size increasing. An effective displacement process of residual CH4 by CO2 was performed, it is found that the displacement is enhanced with the increase of the CO2 bulk pressure, and the pore size has significant influence on the displacement. According to the results, the CO2 capture and storage (CCS) and the enhancement of the CH4 recovery could be achieved at the same time in silica nanopores. This work provides microscopic information about the displacement of CH4 by CO2 in silica nanopores with various size, for the purpose to provide useful guidance for the application of enhancing shale gas recovery by CO2.

The widely performance of surfactants is closely related to their interfacial activity, which is essentially determined by the molecular array behaviours at the interface, of which the studies are significance for clearly understanding their structure-performance relationships. In this paper, the detailed molecular array behaviours of green surfactant alkyl polyglycoside (APG) and the mixed systems with other types of surfactants on oil/water interface have been studied using molecular dynamics simulations, and the key theoretical principle was confirmed by quantum chemistry calculations. It was found that the hydrophilic maltose ring head groups of decyl polyglycoside (C10-APG) are prone to lie flatly at the oil–water interface, the steric hindrance results in the low interfacial density, which critically determines the limit of the interfacial activity. The interfacial adsorption behaviours of the binary mixtures of C10-APG and SDS or DATB and the ternary mixtures of C10-APG, SDS and DATB were studied in detail, how the efficient synergism effect could be achieved for the mixture to get super high interfacial activity was discussed. This study provides a strategy to reveal how the molecular interfacial behaviours determine the key interfacial characteristics of the novel surfactants, which might provide help to promote their applications.

The Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were used to investigate the adsorption and diffusion properties of CH4 and CO2 in montmorillonite slit-nanopor...

Full exploitation and utilization of the unconventional reservoirs of shale gas have become a central issue due to the increasing worldwide energy demand. Enhancing shale gas recovery by injecting CO2 is a promising technique that combines shale gas extraction and CO2 capture and storage (CCS) perfectly. In this study, a kerogen-based slit-shaped pore with a width of ∼21 A was constructed by two kerogen matrices, and the grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were used to investigate the adsorption and diffusion properties of CH4 and CO2 in the kerogen matrix and slit nanopores and explore the displacement efficiency of the residual CH4 by CO2 in kerogen slit nanopores. The adsorption energy of CH4 and CO2 on the kerogen fragment surface and the isosteric heat of CH4 and CO2 in kerogen slit nanopores were examined to demonstrate the competitive adsorption of CO2 over CH4 in kerogen slit nanopores, and the different intensity of interactions between the CH4 and CO...

Polymer-based dielectric materials play a key role in advanced electronic devices and electric power systems. Although extensive research has been devoted to improve their energy-storage performances, it is a great challenge to increase the breakdown strength of polymer nanocomposites in terms of achieving high energy density and good reliability under high voltages. Here, a general strategy is proposed to significantly improve their breakdown strength and energy storage by adding negatively charged Ca2 Nb3 O10 nanosheets. A dramatically enhanced breakdown strength (792 MV m-1 ) and the highest energy density (36.2 J cm-3 ) among all flexible polymer-based dielectrics are observed in poly(vinylidene fluoride)-based nanocomposite capacitors. The strategy generalizability is verified by the similar substantial enhancements of breakdown strength and energy density in polystyrene-based nanocomposites. Phase-field simulations demonstrate that the further enhanced breakdown strength is ascribed to the local electric field, produced by the negatively charged Ca2 Nb3 O10 nanosheets sandwiched with the positively charged polyethyleneimine, which suppresses the secondary impact-ionized electrons and blocks the breakdown path in nanocomposites. The results demonstrate a new horizon of high-energy-density flexible capacitors.

The problem of visual object tracking has traditionally been handled by variant tracking paradigms, either learning a model of the object's appearance exclusively online or matching the object with the target in an offline-trained embedding space. Despite the recent success, each method agonizes over its intrinsic constraint. The online-only approaches suffer from a lack of generalization of the model they learn thus are inferior in target regression, while the offline-only approaches (e.g., convolutional siamese trackers) lack the target-specific context information thus are not discriminative enough to handle distractors, and robust enough to deformation. Therefore, we propose an online module with an attention mechanism for offline siamese networks to extract target-specific features under L2 error. We further propose a filter update strategy adaptive to treacherous background noises for discriminative learning, and a template update strategy to handle large target deformations for robust learning. Effectiveness can be validated in the consistent improvement over three siamese baselines: SiamFC, SiamRPN++, and SiamMask. Beyond that, our model based on SiamRPN++ obtains the best results over six popular tracking benchmarks and can operate beyond real-time.

Mass gathering events have been identified as high-risk environments for community transmission of coronavirus disease 2019 (COVID-19). Empirical estimates of their direct and spill-over effects however remain challenging to identify. In this study, we propose the use of a novel synthetic control framework to obtain causal estimates for direct and spill-over impacts of these events. The Sabah state elections in Malaysia were used as an example for our proposed methodology and we investigate the event’s spatial and temporal impacts on COVID-19 transmission. Results indicate an estimated (i) 70.0% of COVID-19 case counts within Sabah post-state election were attributable to the election’s direct effect; (ii) 64.4% of COVID-19 cases in the rest of Malaysia post-state election were attributable to the election’s spill-over effects. Sensitivity analysis was further conducted by examining epidemiological pre-trends, surveillance efforts, varying synthetic control matching characteristics and spill-over specifications. We demonstrate that our estimates are not due to pre-existing epidemiological trends, surveillance efforts, and/or preventive policies. These estimates highlight the potential of mass gatherings in one region to spill-over into an outbreak of national scale. Relaxations of mass gathering restrictions must therefore be carefully considered, even in the context of low community transmission and enforcement of safe distancing guidelines., Author summary Mass gathering events have been identified as high-risk environments for community transmission of coronavirus disease 2019 (COVID-19). Empirical estimates of their direct and spill-over effects however remain limited. We frame the Sabah state election in Malaysia as a natural experiment to investigate the event’s spatial and temporal impacts on COVID-19 transmission. We estimate the direct and spill-over impact of the elections through a synthetic control methodology. Results indicate an estimated (i) 70.0% of COVID-19 case counts within Sabah post-state election were attributable to the election’s direct effect; (ii) 64.4% of COVID-19 cases in the rest of Malaysia post-state election were attributable to the election’s spill-over effects. We demonstrate that our estimates are not due to pre-existing epidemiological trends, surveillance efforts, and/or preventive policies. These estimates highlight the potential of mass gatherings in one region to spill-over into an outbreak of national scale. Relaxations of mass gathering restrictions must therefore be carefully considered, even in the context of low community transmission and enforcement of safe distancing guidelines.

The synthetic α-zirconium phosphate (ZrP) modified by tetra-n-butylammonium hydroxide (TBA+OH−) was used to fabricate highly transparent and superhydrophilic coating on glass substrate through a facile and effective approach. The influence of molar ratio between TBA+OH− and ZrP on the surface topographical morphology, as well as the hydrophilicity and transparency of coating was explored. It was found that, the higher concentration of TBA+OH− is, the better surface wettability and light transmission performance are. With more introduction of TBA+OH−, more TBA+ ions can be intercalated into the ZrP interlayers to form exfoliated nanoplatelets, which are able to continuously cover the whole glass substrate as revealed by scanning electron microscopy and atom force microscopy. As a result, the contact angle of the prepared coatings can reach to ~4.5° at 400 ms and ~0° within 1 s. The completely exfoliated structure of ZrP nanoplatelets and high surface charge density provided by TBA+ ions make a great contribution to the highly transparent and superhydrophilic coatings on glass substrates. The detailed mechanisms on fabricating high-performance superhydrophilic coatings on glass substates by TBA+OH− modifying ZrP nanoplatelets are carefully elaborated.

In this study, styrene/heptadecafluorodecyl acrylate (St–HFDA) copolymers of different compositions were synthetized for the purpose of thickening supercritical carbon dioxide (SC-CO2). The cloud point pressures of the copolymer–CO2 mixtures and the thickening effects of these copolymers for SC-CO2 were measured. Molecular dynamics (MD) simulations were used to evaluate the intermolecular interactions and microstructures of polymer–CO2 systems, the copolymer–CO2 interaction energy, cohesive energy density (CED), solubility parameter, equilibrium conformations and radial distribution functions (RDFs) were obtained, which provided useful information for microscopic understanding on the thickening capability of copolymers in SC-CO2. It was found that all the synthesized St–HFDA copolymers induced greater viscosity enhancements of SC-CO2 compared to poly(Heptadecafluorodecyl acrylate) (PHFDA), and π–π stacking of the Styrene (St) groups played a key role in thickening SC-CO2. On one hand, the introduction of the St groups into PHFDA weakened the CO2-philicity of the polymers by reducing the polymer–CO2 interaction and increasing polymer–polymer interactions, resulting in higher cloud point pressure in SC-CO2 compared to PHFDA. On the other hand, the increase of the polymer–polymer interaction via π–π stacking provided an associative force to thicken SC-CO2. The subtle relationship between the copolymer composition and thickening abilities of the copolymers in SC-CO2 were evaluated and the optimum styrene molar ratio was determined. It can be concluded that the content of the CO2-philic HFDA groups and the CO2-phobic St groups in the copolymers should be optimized to achieve the balance between the solubility and the thickening capability.

Agricultural water management is the core part of agricultural efficient water use in irrigation districts, which provides basic guarantee and decision-support for improving the efficiency of water production. This study was conducted in three typical irrigation districts in Huang-huai-hai river basin of north China. The evaluation index system of agricultural water management in irrigation districts was established which included technology index, engineering index, management index, environment index and economic index, classified 5 sorts of second-grade indices, 14 third-grade indices and 35 fourth-grade indices. The weight of each index was confirmed through improved AHP method. The grades of agricultural water management of Fenhe, Shijin and Renmin Shengliqu irrigation districts in Huang-huai-hai riverbasin were obtained using Grey Correlation method and Fuzzy Comprehensive Evaluation method. Results showed that the evaluation indices ranked according to the descending order of their weights as engineering index, 0.2147; management index, 0.2138; technology index, 0.2128; economics index, 0.1797; environment index, 0.1791 in the criterion level. The engineering and management index were the most two important factors which influenced the agricultural water management in irrigation districts. The grades of Fenhe, Shijin and Renmin Shengliqu irrigation districts were good, good and average, respectively. The study provides a theoretical basis in improving the level of agricultural water management and water use efficiency in irrigation districts of north China.

Nylon6 nanocomposites containing pristine layered α-zirconium phosphate (ZrP) nanoplatelets of various sizes have been fabricated by a simple and direct melt-compounding method without adding intercalation or exfoliation agents. Owing to the excellent compatibility between the nanofillers and Nylon6, the pristine ZrP nanoplatelet nanocrystallites were well dispersed and homogeneously distributed into the polymer matrices during the melt processing, but still maintained their original layered state as observed by scanning electron microscopy and X-ray diffraction. Tensile testing and dynamic mechanical analysis on the Nylon6/ZrP nanocomposites illustrate that the size and concentration of the pristine ZrP nanoplatelets have a profound effect on the mechanical properties of such prepared polymer nanocomposites. The improvement of the mechanical reinforcement for the Nylon6 nanocomposites does not show a steady increase with the increase in the size and concentration of the embedded pristine ZrP nanoplatelets, but displays the maximum for the pristine ZrP nanoplatelets with a size ranging from 600 nm to 800 nm at a concentration of ∼3.0–5.0% in the polymer matrices. The mechanisms that are responsible for the mechanical reinforcement of thermoplastic polymer matrices by the embedded pristine ZrP nanoplatelets, as well as their comparisons with corresponding epoxy nanocomposites, are also discussed.

In this paper, the bulk phase aggregation and interfacial adsorption properties as well as foam characteristics of a kind of amino acid-based surfactant sodium lauroylglutamate (LGS) under the variety of external conditions such as temperature and pH were investigated. The variation of the protonation degree of the head group of the surfactant as a function of pH was analyzed by integrating determination results of acid-base titration and FT-IR (ATR) spectra. At neutral pH, the LGS solution had the minimum surface tension and could form more stable foam. The mechanism about how the pH affects the foam stability of LGS was discussed thoroughly. TEM images of the LGS foam films and the bulk phase solutions showed that gel network association structure was formed not only in bulk phase in specific temperature range and suitable pH, but also in the foam films. The variation of the strength of the gel formed in foam film under different external conditions has obviously different influence on foam stability.

The high adsorption capacity of the phase change mediums in porous supports is a key requirement for the shape-stabilized phase change materials (ss-PCMs) with high latent heat. Here, ship-shaped diatom (Pennales) frustule-based composite ss-PCMs with high polyethylene glycol (PEG) absorption capacity and high phase change enthalpy was prepared by a solution-assisted vacuum impregnation method for high-performance thermal energy storage. To improve the diatom frustules’ specific surface area and form a multi-level pore structure, the effects of calcination temperature on the microstructure of diatom frustules were studied. It was found that diatom frustules calcined at 400 °C (400CDF) had a relatively high specific surface area (~155.9 m2/g) with a well-maintained skeleton, which was a suitable PEG supporter. The devised PEG/400CDF composites with 72.7% loading of PEG4000 that had a latent heat value of 128.9 J/g for melting and 136.7 J/g for freezing, and the relative enthalpy efficiency reached up to 97.7%. The composite ss-PCMs exhibited thermal and chemical stability even after 200 thermal cycles. The current work demonstrated that ss-PCMs from biomass-based artificially cultured diatoms could slow the spread of heat by absorbing thermal energy. Moreover, the phase change mechanisms of the PEG/CDF composites under the nanoconfinement in the diatom frustules framework were also explored to explain the obtained high adsorption capacity.

Chemical mechanical polishing (CMP) is the most effective technology for the global and local planarization of metal surfaces. In this study, an environment-friendly and highly efficient CMP slurry for aluminum alloy is prepared by using 2D layered zirconium phosphate (ZrP) platelets and alumina (Al2O3) particles as hybrid abrasives, polyethylene glycol (PEG) as dispersant, hydrogen peroxide (H2O2) as oxidant and sodium dodecyl sulfate (SDS) as corrosion inhibitor. Using the optimized CMP slurry, surface roughness (Ra) of aluminum alloy is decreased from ~200 nm to ~13 nm and material removal rate (MRR) can be increased from 150 nm/min to 300 nm/min. The addition of ZrP platelets can improve the stability and dispersion of the Al2O3 abrasives due to the PEG-induced hydrogen bonding interactions between the used hybrid abrasives. Moreover, the X-ray photoelectron spectroscopy (XPS) and electrochemical analysis reveal that adjusting the concentrations of H2O2 and SDS in the CMP slurry would help to achieve an excellent balance between the chemical corrosion and mechanical removal. The use of binary hybrid abrasives in CMP slurries provides a novel route for the efficient planarization of aluminum alloy and also sheds light on precise polishing for metallic and non-metallic materials with desired surface requirements.

Polylactic acid (PLA) is a promising biodegradable polyester, however, the brittle nature of PLA restricts its applications. In this study, PLA is reinforced by artificially cultured diatom frustules (DFs) to prepare high-performance and biodegradable polymer composites via melt blending. Interpenetrating structure can be observed between DFs and PLA by scanning electron microscope (SEM) due to the porous nature of diatom. Both X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis reveal that well-dispersed DFs can act as a nucleating agent to increase the crystallinity of the α-crystal in PLA, but decrease its cold crystallization temperature (Tcc). Tensile tests show that both strength and ductility of PLA can be enhanced simultaneously by incorporation of a few percent of DFs. Dynamic mechanical analysis (DMA) indicates that DFs can increase the storage modulus and maintain the glass transition temperature of PLA. Our study illustrates the promise of utilizing artificially cultured diatom frustules as biomass-based reinforcing fillers for preparing high-performance fully-biodegraded polymeric materials for green and sustainable applications.

Various applications of CO2 have received extensive attention, especially those realizing the reuse of the greenhouse gas and meeting the application requirements simultaneously, of which the CO2 enhanced oil recovery (EOR) and enhanced gas recovery (EGR) approaches is a paradigm. In recent years, the applications of CO2 foam as flooding or fracturing system are both of the research hotspots. Since conventional surfactants are generally poor in stabilizing CO2 foam, the exploration of CO2 foam stabilizer is of great significance, while it is also a difficult problem. In this work, a kind of hydrophobically modified water-soluble polyelectrolyte (HMPE) was used in the stabilization of CO2 foam containing millimeter-sized and micron-sized bubbles, which both exhibit high stability and perfect foam viscoelasticity, due to the enhancement of the mechanical strength of the foam films through HMPE absorbed at the gas/liquid interfaces. The interaction between the CO2 bubbles and ceramiste particles was investigated, the mechanism of the excellent sand-carrying performance of the CO2 foam system was discussed. Based on the comprehensive understanding of all aspects of the properties, the HMPE-CO2 foam system has bright potential being used in the CO2-foam fracturing.

Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were used to investigate the adsorption and diffusion properties of CH4 and CO2 in calcite slit nanopores with a pore width of ∼22 A. It was found that, in contrast to CH4, CO2 molecules have a much higher capacity to be adsorbed onto calcite pore surfaces. The diffusion capacity of CO2 molecules is much less in comparison with that of CH4 molecules, which could be attributed to diverse interactions between CO2 gas molecules and calcite nanopore surfaces. An effective displacement process of residual adsorbed CH4 in calcite slit nanopores by CO2 was performed, and it was found that the displacement efficiency was enhanced with an increase in the bulk pressure. This work provides microscopic information about the adsorption and diffusion properties of CH4 and CO2 in calcite nanopores, and confirmed the feasibility of the displacement of adsorbed CH4 in calcite nanopores by CO2, with the purpose of providing useful guidance for enhancing the extraction of shale gas by injecting CO2.

In this paper, the detailed behaviors of all the molecules, especially the interfacial array behaviors of surfactants and diffusion behaviors of gas molecules, in foam systems with different gases (N2, O2, and CO2) being used as foaming agents were investigated by combining molecular dynamics simulation and experimental approaches for the purpose of interpreting how the molecular behaviors effect the properties of the foam and find out the key factors which fundamentally determine the foam stability. Sodium dodecyl sulfate SDS was used as the foam stabilizer. The foam decay and the drainage process were determined by Foamscan. A texture analyzer (TA) was utilized to measure the stiffness and viscoelasticity of the foam films. The experimental results agreed very well with the simulation results by which how the different gas components affect the interfacial behaviors of surfactant molecules and thereby bring influence on foam properties was described.

Vinyl Benzoate/Heptadecafluorodecyl acrylate (VBe/HFDA) co-polymers were synthesized and characterized as thickening agents for supercritical carbon dioxide (SC-CO2). The solubility and thickening capability of the co-polymer samples in SC-CO2 were evaluated by measuring cloud point pressure and relative viscosity. The molecular dynamics (MD) simulation for all atoms was employed to simulate the microscopic molecular behavior and the intermolecular interaction of co-polymer–CO2 systems. We found that the introduction of VBe group decreased the polymer–CO2 interaction and increased the polymer–polymer interaction, leading to a reduction in solubility of the co-polymers in SC-CO2. However, the co-polymer could generate more effective inter-chain interaction and generate more viscosity enhancement compared to the Poly(Heptadecafluorodecyl) (PHFDA) homopolymer due to the driving force provided by π-π stacking of the VBe groups. The optimum molar ratio value for VBe in co-polymers for the viscosity enhancement of SC-CO2 was found to be 0.33 in this work. The P(HFDA0.67-co-VBe0.33) was able to enhance the viscosity of SC-CO2 by 438 times at 5 wt. %. Less VBe content would result in a lack of intermolecular interaction, although excessive VBe content would generate more intramolecular π-π stacking and less intermolecular π-π stacking. Both conditions reduce the thickening capability of the P(HFDA-co-VBe) co-polymer. This work presented the relationship between structure and performance of the co-polymers in SC-CO2 by combining experiment and molecular simulations.