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Rechargeable aqueous zinc batteries (RAZBs) are emerging candidates for large‐scale energy storage. However, the lack of high‐capacity cathodes because of the electrostatic interactions between Zn2+ and cathode and the inferior electronic conductivity restricts their performance. The operating voltage limitation imposed by water is another barrier for RAZBs. Herein, manganese oxide (MnO) nanocrystals embedded in a spindle carbon matrix (MnO@C) synthesized from a metal–organic framework are used as a cathode. The uniform distribution of fine‐sized MnO (≈100 nm) in the carbonized matrix (≈5 μm) and the intimate connection between them not only increase the utilization of electroactive material but also eliminate the use of conductive additive. By utilizing the molten hydrate electrolyte, ZnCl2·2.33H2O, a discharge voltage plateau approaching 1.60 V and a high reversible capacity of 106 mAh g−1 after 200 cycles are achieved. This research proposes an approach for affordable RAZBs to fulfill large‐scale energy storage. [ABSTRACT FROM AUTHOR]

Cold seeps are widely developed on the seabed of continental margins and can form gas plumes due to the upward migration of methane-rich fluids. The detection and automatic segmentation of gas plumes are of great significance in locating and studying the cold seep system that is usually accompanied by hydrate layers in the subsurface. A multibeam echo-sounder system (MBES) can record the complete backscatter intensity of the water column, and it is one of the most effective means for detecting cold seeps. However, the gas plumes recorded in multibeam water column images (WCI) are usually blurred due to the interference of the complicated water environment and the sidelobes of the MBES, making it difficult to obtain the effective segmentation. Therefore, based on the existing UNet semantic segmentation network, this paper proposes an AP-UNet network combining the convolutional block attention module and the pyramid pooling module for the automatic segmentation and extraction of gas plumes. Comparative experiments are conducted among three traditional segmentation methods and two deep learning methods. The results show that the AP-UNet segmentation model can effectively suppress complicated water column noise interference. The segmentation precision, the Dice coefficient, and the recall rate of this model are 92.09%, 92.00%, and 92.49%, respectively, which are 1.17%, 2.10%, and 2.07% higher than the results of the UNet. [ABSTRACT FROM AUTHOR]

During the solid fluidization exploitation of marine natural gas hydrates, the hydrate particles and cuttings produced via excavation and crushing are transported by the drilling mud. The potential flow safety issues arising during the transport process, such as the blockage of pipelines and equipment, have attracted considerable attention. This study aims to investigate the impact of hydrate adhesion features, including agglomeration, cohesion, and deposition, on the flow transport processes in solid fluidization exploitation and to provide a reference for the design and application of multiphase hydrate slurry transport in solid fluidization exploitation. We established a numerical simulation model that considers the hydrate adhesion properties using the coupled computational fluid dynamics and discrete element method (CFD-DEM) for the multiphase mixed transport in solid fluidization exploitation. An appropriate model to simulate the adhesion force of the hydrate particles and the corresponding parameter values were obtained. The conclusions obtained are as follows. Under the same operating conditions, a stationary bed is more likely to form in the transport process due to the hydrate adhesion forces; adhesion forces can increase the critical deposition velocity of the mixture of hydrate particles and cuttings. Hydrate adhesion lowers the height of the solid-phase moving bed, while the agglomeration and cohesion of particles can intensify the aggregation and deposition of hydrate debris and cuttings at the bottom of the pipe. These particles tend to form a deposit bed rather than a moving bed, which reduces the effective flow area of the pipeline and increases the risk of blockage. [ABSTRACT FROM AUTHOR]

To explore the feasibility of the application of steel slag powder (SSP) in steam-cured precast concrete, 0% and 20% SSP were used to replace cement and prepare cement paste, and the early age performance of steam-cured (80 °C for 7 h and 7 d) SSP-blended cement paste, including different types and amounts of hydrates, the microstructure and mechanical properties were investigated and compared with those of 28 d standard-cured SSP sample. The results show that SSP addition promotes the generation of laminar C-S-H gels and granular C-S-H gels after an initial 7 h steam curing. Further extending the lasting time of 80 °C steam curing to 7 days favors the production of hydrogarnet and crystalline C-S-H, of which the amount of formation of hydrogarnet in SSP composite cement paste is less and the particle size is smaller than those in the control sample. However, steam curing increases the gap between the number of hydrates formed in SSP-blended cement paste and the control paste. The delayed hydration effect of SSP on cement offsets the promoting effect of steam curing on the hydration of cement; in consequence, the incorporation of SSP seems to be detrimental to the hydration of steam-cured cement paste. [ABSTRACT FROM AUTHOR]

Transition metal phosphates (TMPs) have attracted interest as materials for (electro-) catalysis, and electrochemistry due to their low-cost, stability, and tunability. In this work, an automated synthesis platform was used for the preparation of transition metal phosphate crystals to efficiently explore the multidimensional parameter space, determining the phase selection, crystal sizes, shapes. By using X-ray diffraction and spectroscopy-based methods and electron microscopy imaging, a complete characterization of the phase stability fields, phase transitions, and crystal morphology/sizes was achieved. In an automated three-reactant synthesis, the individual effect of each reactant species NH4+, M2+, and PO43− on the formation of transition metal phosphate phases: M-struvite NH4MPO4·6H2O, M–phosphate octahydrate M3(PO4)2·8H2O with M = Ni, Co and an amorphous phase, was investigated. The NH4+ concentration dictates the phase composition, morphology, and particle size in the Ni-system (crystalline Ni-struvite versus amorphous Ni–PO4 phase), whereas in the Co-system all reactant species – NH4+, Co2+, and PO43− – influence the reaction outcome equivalently (Co-struvite vs. Co–phosphate octahydrate). The coordination environment for all crystalline compounds and of the amorphous Ni–PO4 phase was resolved by X-ray absorption spectroscopy, revealing matching characteristics to its crystalline analogue, Ni3(PO4)2·8H2O. The automated synthesis turned out to be significantly advantageous for the exploration of phase diagrams due to its simple modularity, facile traceability, and enhanced reproducibility compared to a typical manual synthesis. [ABSTRACT FROM AUTHOR]

The effects of a hybrid nanofluid (Cu‐Al layered double hydroxide (LDH)) on the CO2 hydrate formation kinetics was investigated at three different nanofluid concentrations (0.25–1.0 wt %). The Cu‐Al LDH nanofluid was prepared using a one‐step co‐precipitation technique. The addition of the LDH nanofluid reduces the induction time and enhances the hydrate formation kinetics. The maximum reduction in the induction time (by 91.08 %) was observed at the optimal nanofluid concentration of 0.5 wt %, compared to water. A chemical affinity model was implemented to predict the experimental data for CO2 hydrate formation in the presence of the different LDH nanofluid concentrations. An artificial neural network‐based Levenberg‐Marquardt model predicts the experimental data with higher accuracy than the scaled conjugate gradient model. The results indicate a strong dependency of the hydrate formation kinetics on the LDH nanofluid concentrations. [ABSTRACT FROM AUTHOR]

Sour gas in hydrocarbon reservoirs contains significant amounts of H2S and smaller amounts of CO2. To minimize operational costs, meet air emission standards and increase oil recovery, operators revert to acid gas (re-)injection into the reservoir rather than treating H2S in Claus units. This process requires the pressurization of the acid gas, which, when combined with low-temperature conditions prevailing in subsurface pipelines, often leads to the formation of hydrates that can potentially block the fluid flow. Therefore, hydrates formation must be checked at each pipeline segment and for each timestep during a flow simulation, for any varying composition, pressure and temperature, leading to millions of calculations that become more intense when transience is considered. Such calculations are time-consuming as they incorporate the van der Walls–Platteeuw and Langmuir adsorption theory, combined with complex EoS models to account for the polarity of the fluid phases (water, inhibitors). The formation pressure is obtained by solving an iterative multiphase equilibrium problem, which takes a considerable amount of CPU time only to provide a binary answer (hydrates/no hydrates). To accelerate such calculations, a set of classifiers is developed to answer whether the prevailing conditions lie to the left (hydrates) or the right-hand (no hydrates) side of the P-T phase envelope. Results are provided in a fast, direct, non-iterative way, for any possible conditions. A set of hydrate formation "yes/no" points, generated offline using conventional approaches, are utilized for the classifier's training. The model is applicable to any acid gas flow problem and for any prevailing conditions to eliminate the CPU time of multiphase equilibrium calculations. [ABSTRACT FROM AUTHOR]

This paper presents the results of an acoustic survey carried out from the fast ice in the shallow waters of the East Siberian Arctic Shelf (ESAS) using a single beam echosounder. The aim of this paper is to demonstrate an improved approach to study seafloor seepages in the Arctic coastal zone with an echosounder calibrated on site. During wintertime field observations of natural rising gas bubbles, we recorded three periods of their increased activity with a total of 63 short-term ejections of bubbles from the seabed. This study presents quantitative estimates of the methane (CH4) flux obtained in wintertime at two levels of the water column: (1) at the bottom/water interface and (2) at the water/sea ice interface. In winter, the flux of CH4 transported by rising bubbles to the bottom water in the shallow part of the ESAS was estimated at ~19 g·m−2 per day, while the flux reaching the water/sea ice interface was calculated as ~15 g·m−2 per day taking into account the diffusion of CH4 in the surrounding water and the enrichment of rising bubbles with nitrogen and oxygen. We suggest that this bubble-transported CH4 flux reaching the water /sea ice interface can be emitted into the atmosphere through numerous ice trenches, leads, and polynyas. This CH4 ebullition value detected at the water/sea ice interface is in the mid high range of CH4 ebullition value estimated for the entire ESAS, and two orders higher than the upper range of CH4 ebullition from the northern thermocarst lakes, which are considered as a significant source to the atmospheric methane budget. [ABSTRACT FROM AUTHOR]

The ubiquitous presence of crystal defects provides great potential and opportunities to construct the desired structure (hence with the desired properties) and tailor the synthetic process of crystalline materials. However, little is known about their regulation role in phase transition and crystallization pathways. It was generally thought that a phase transition in solution proceeds predominantly via the solvent-mediated phase-transformation pathway due to energetically high-cost solid-state phase transitions (if any). Herein, we report an unprecedented finding that an orientational disorder defect present in the crystal structure triggers an unusual pathway of a core-shell phase transition with apparent shape-preserved evolution. In the pathway, the solid-state dehydration phase transition occurs inside the crystal prior to its competitive transformation approach mediated by solvent, forming an unconventional core-shell structure. Through a series of combined experimental and computational techniques, we revealed that the presence of crystal defects, introduced by urate tautomerism over the course of crystallization, elevates the metastability of uric acid dihydrate (UAD) crystals and triggers UAD dehydration to the uric acid anhydrate (UAA) phase in the crystal core which precedes with surface dissolution of the shell UAD crystal and recrystallization of the core phase. This unique phase transition could also be related to defect density, which appears to be influenced by the thickness of UAD crystals and crystallization driving force. The discovery of an unusual pathway of the core-shell phase transition suggests that the solid-state phase transition is not necessarily slower than the solvent-mediated phase transformation in solution and provides an alternative approach to constructing the core-shell structure. Moreover, the fundamental role of orientational disorder defects on the phase transition identified in this study demonstrates the feasibility to tailor phase transition and crystallization pathways by strategically importing crystal defects, which has broad applications in crystal engineering.

The in‐situ stress state and geomechanical properties of hydrate‐bearing sediments impact hydrate formation and gas production strategies. We explore the uniaxial strain compression and stress evolution of natural hydrate‐bearing sandy‐silts from Green Canyon Block 955 in the deep‐water Gulf of Mexico. We performed constant rate of strain uniaxial strain experiments, interrupted by periods where we held the axial stress constant, to explore the vertical deformation and the evolution of the ratio of lateral to axial effective stress (K0) with time. The hydrate‐bearing sandy‐silt is stiffer and has a larger K0 than the equivalent hydrate‐free sediment upon loading. During stress holds, the void ratio decreases sigmoidally with the log of time, and K0 converges to isotropic conditions. We interpret that during loading, the hydrate bears the load and deforms. With time, the hydrate redistributes the load and K0 increases. We used a viscoelastic model to describe the behavior. The model accurately captures deformation and K0 trends but does not reproduce all the complex interactions of the hydrate with the porous skeleton. We anticipate that viscous effects within hydrate sediments will impact reservoir compression and stresses during production (hours to days), result in isotropic stress state over geological timescales, and explain the creeping movement in submarine landslides. Plain Language Summary: Natural methane hydrates are ice‐like crystalline solids, typically found within and beneath permafrost regions and near the seafloor in the deep ocean. They host large amounts of methane and are envisioned as a potential energy resource, a potential geo‐hazard, and an active component in the Earth's carbon cycle. We studied the geomechanical behavior of natural and intact hydrate‐bearing sandy‐silts recovered from the deep‐water Gulf of Mexico. We performed all the experiments at a high pressure and low temperature to maintain the hydrate stable during testing. This study demonstrates that these hydrate‐bearing sandy‐silts are viscoplastic; deformation and stresses are rate‐dependent. Under sustained vertical load, while allowing no lateral deformation, the lateral stress rises with time. This process is known as stress relaxation. Simultaneously, the material undergoes vertical compression with time, a process known as creep. We interpret that these systems deform by hydrate "flowing" and displacing the pore water within the sediment. The hydrate distributes the load in all directions, and stress relaxation takes place. This viscoplastic behavior has important implications for gas hydrate production models, drilling and completing wellbores safely, and may elucidate the mechanisms for submarine landslides. Key Points: Hydrate‐bearing sandy‐silts are viscoplastic materials with a relaxation time scale on the order of hoursThe in‐situ stress state in hydrate‐bearing sandy‐silts undergoing burial may be isotropicLoad‐bearing hydrate flow viscously and redistributes the load. A spring‐dashpot model captures this behavior [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon dioxide (CO 2) reduction is an urgent challenge worldwide due to the dramatically increased CO 2 concentration and concomitant environmental problems. Geological CO 2 storage in gas hydrate in marine sediment is a promising and attractive way to mitigate CO 2 emissions owning to its huge storage capability and safety. However, the sluggish kinetics and unclear enhancing mechanisms of CO 2 hydrate formation limit the practical application of hydrate-based CO 2 storage technologies. Here, we used vermiculite nanoflakes (VMNs) and methionine (Met) to investigate the synergistic promotion of natural clay surface and organic matter on CO 2 hydrate formation kinetics. Induction time and t 90 in VMNs dispersion with Met were shorter by one to two orders of magnitude than Met solution and VMNs dispersion. Besides, CO 2 hydrate formation kinetics showed significant concentration-dependence on both Met and VMNs. The side chains of Met can promote CO 2 hydrate formation by inducing water molecules to form a clathrate-like structure. However, when Met concentration exceeded 3.0 mg/mL, the critical amount of ammonium ions from dissociated Met distorted the ordered structure of water molecules, inhibiting CO 2 hydrate formation. Negatively charged VMNs can attenuate this inhibition by adsorbing ammonium ions in VMNs dispersion. This work sheds light on the formation mechanism of CO 2 hydrate in the presence of clay and organic matter which are the indispensable constituents of marine sediments, also contributes to the practical application of hydrate-based CO 2 storage technologies. [ABSTRACT FROM AUTHOR]

Nilutamide (Nil), commercialized under the trade names Nilandron and Anandron, is a nonsteroidal antiandrogen drug used in prostate cancer treatment. The attempts to cocrystallize nilutamide with adenine (Adn) and orotic acid monohydrate (OMH) resulted in the formation of four novel solid forms of the drug, namely the [Nil + Adn] (1 : 1) cocrystal, two new polymorphs of Nil (forms IV and V), and the Nil hydrate ([Nil·H2O] (2 : 0.57)). The crystal structures of the solid forms were elucidated by single-crystal X-ray diffraction. New nilutamide polymorphic forms IV and V were found to contain multiple symmetry-independent molecules in the asymmetric unit whose Z′ = 3 (form IV) and Z′ = 2 (form V), while the three previously reported forms (form I, form II, form III) had Z′ = 1. Despite several attempts, the bulk phase-pure materials of form IV, form V, and [Nil·H2O] (2 : 0.57) could not be attained due to the concomitant crystallization of the solid forms and the poor reproducibility of the crystallization trials. Hence, only limited characterization studies were performed on these phases. In this work, structural elucidation, Hirshfeld, and conformational analysis were explored to understand the similarities and dissimilarities in the crystal packing environment for all the crystal structures. Thermal analysis reveals the phase transformation of [Nil·H2O] (2 : 0.57) to form II. Crystal structure analysis paved the way to understand the prominence of various intermolecular interactions along with the amide dimer and catemer formation. For the [Nil + Adn] (1 : 1) cocrystal, the thermodynamic solubility was evaluated using eutectic concentrations of the components and found to be higher than that of the parent Nil. The effect of hydroxypropyl methylcellulose on the dissolution behavior of the cocrystal was explored. [ABSTRACT FROM AUTHOR]

Existing soft ionic conductors fall into two distinct categories: liquid‐rich ionic conductors containing large amounts of liquid electrolytes (≈70–90 wt.% water for hydrogels and ≈20–80 wt.% ionic liquids for ionogels), and liquid‐free ionic conductors that do not contain liquid components (e.g., ionic conductive elastomers). However, they are often plagued by dehydration, leakage of toxic ionic liquids, and air aging. Here, using hydrophobic polymer networks and hydrophilic salt hydrates, ionic conductive elastomers (s‐ICEs for short) containing only a tiny amount of bound water (≈1–5 wt.% are synthesized). Thanks to the small embedded water content, the s‐ICEs are advantageous over liquid‐rich ionic conductors in terms of enhanced mechanical/electrical stabilities and safety; they also outperform previously reported liquid‐free ionic conductors by avoiding air‐aging issues. The s‐ICEs introduced here also show excellent stretchability, good elasticity, high fracture resistance, desirable optical transparency and ionic conductivity, which are comparable to those of state‐of‐the‐art liquid‐rich and liquid‐free ionic conductors. With all the above advantages, the s‐ICE represents an ideal material for practical applications of soft ionotronics in ambient conditions. [ABSTRACT FROM AUTHOR]

Isotopic fractionation of methane between gas and solid hydrate phases provides data regarding hydrate-forming environments, but the effect of pressure on isotopic fractionation is not well understood. In this study, methane hydrates were synthesized in a pressure cell, and the hydrogen isotope compositions of the residual and hydrate-bound gases were determined. The δ2H of hydrate-bound methane formed below the freezing point of water was 5.7–10.3‰ lower than that of residual methane, indicating that methane hydrate generally encapsulates lighter molecules (CH4) instead of CH32H. The fractionation factors αH-V of the gas and hydrate phases were in the range 0.9881–0.9932 at a temperature and pressure of 223.3–268.2 K and 1.7–19.5 MPa, respectively. Furthermore, αH-V increased with increasing formation pressure, suggesting that the difference in the hydrogen isotopes of the hydrate-bound methane and surrounding methane yields data regarding the formation pressure. Although the differences in the hydrogen isotopes observed in this study are insignificant, precise analyses of the isotopes of natural hydrates in the same area enable the determination of the pressure during hydrate formation. [ABSTRACT FROM AUTHOR]

In this paper, the influence of process parameters on the morphological properties of fine precipitated hydrate was examined. The research was conducted with the aim of synthesizing fine precipitated aluminum hydroxide from the aluminate solution obtained by the Bayer process. Fine precipitated hydrates obtained in this way are mostly used in the non-metallurgical industry. The synthesized fine precipitated hydrate should comply with certain quality requirements such as granulometry (average particle diameter), purity, specific surface area, whiteness, etc. This paper shows the influence of certain technological parameters, namely the initial precipitation temperature, the amount and specific surface area of the seed, the influence of the NaOH/Al(OH)3 molar ratio on the characteristics of the synthesized fine precipitated hydrate in terms of the specific surface area, mean diameter and morphology of the obtained particles. [ABSTRACT FROM AUTHOR]

The experimental testing and analysis of strength and deformation characteristics of hydrate reservoirs is an integral part of natural gas hydrate exploitation. However, studies so far have failed to deeply explore samples from the South China Sea. Especially, there is a lack of a simple and applicable method to estimate their mechanical behaviors. Thus, based on test data, an improved Duncan-Chang model is established in this paper to characterize the strength and deformation of reconstituted samples with various hydrate saturation and stress states from this area. This model can accurately describe the strainhardening characteristics, and failure strength is estimated by the improved Drucker-Prager criterion with high fitting accuracy. The initial elastic modulus and failure ratio are given by the proposed empirical models, which are obtained from experimental data and fitting methods. Generally, this model has several advantages including simple structure, favorable performances, and a limited number of model parameters. Therefore, it could be widely used in strength and deformation analysis. This study can support the prevention and control of geological risks during natural gas hydrate exploitation in the South China Sea. [ABSTRACT FROM AUTHOR]

[Display omitted] The precipitation and dissolution of aluminum-bearing mineral phases in aqueous systems often proceed via changes in both aluminum coordination number and connectivity, complicating molecular-scale interpretation of the transformation mechanism. Here, the thermally induced transformation of crystalline sodium aluminum salt hydrate, a phase comprised of monomeric octahedrally coordinated aluminate which is of relevance to industrial aluminum processing, has been studied. Because intermediate aluminum coordination states during melting have not previously been detected, it is hypothesized that the transition to lower coordinated aluminum ions occurs within a highly disordered quasi-two-dimensional phase at the solid-solution interface. In situ X-ray diffraction (XRD), Raman and 27Al nuclear magnetic resonance (NMR) spectroscopy were used to monitor the melting transition of nonasodium aluminate hydrate (NSA, Na 9 [Al(OH) 6 ] 2 ·3(OH)·6H 2 O). A mechanistic interpretation was developed based on complementary classical molecular dynamics (CMD) simulations including enhanced sampling. A reactive forcefield was developed to bridge speciation in the solution and in the solid phase. In contrast to classical dissolution, aluminum coordination change proceeds through a dynamically stabilized ensemble of intermediate states in a disordered layer at the solid-solution interface. In both melting and dissolution of NSA, octahedral, monomeric aluminum transition through an intermediate of pentahedral coordination. The intermediate dehydroxylates to form tetrahedral aluminate (Al(OH) 4 −) in the liquid phase. This coordination change is concomitant with a breaking of the ionic aluminate-sodium ion linkages. The solution phase Al(OH) 4 − ions subsequently polymerize into polynuclear aluminate ions. However, there are some differences between bulk melting and interfacial dissolution, with the onset of the surface-controlled process occurring at a lower temperature (∼30 °C) and the coordination change taking place more gradually as a function of temperature. This work to determine the local structure and dynamics of aluminum in the disordered layer provides a new basis to understand mechanisms controlling aluminum phase transformations in highly alkaline solutions. [ABSTRACT FROM AUTHOR]

We computed the phase diagram of CO2 hydrates at high pressure (HP), from 0.3 to 20 kbar, by means of molecular dynamics simulations. The two CO2 hydrates known to occur in this pressure range are the cubic structure I (sI) clathrate and the HP hydrate, whose water framework is the recently discovered ice XVII. We investigated the stability of both hydrates upon heating (melting) as well as the phase changes upon compression. The CO2-filled ice XVII is found to be more stable than the sI clathrate and than the mixture of ice VI and dry ice at pressure values ranging from 6 to 18 kbar and in a wide temperature range, although a phenomenological correction suggests that the stability should more realistically range from 6.5 to 13.5 kbar. Our simulation results support the current hypothesis that the HP hydrate is stable at temperatures above the melting curve of ice VI. [ABSTRACT FROM AUTHOR]

Recently, a new gas hydrate structure has been discovered. This structure, sX, is unique in a sense that it is so far the only gas hydrate with chiral channels. It is formed by hydrogen-water or carbon dioxide-water mixtures at pressures above 0.300 GPa, and it has been shown that it is the only clathrate hydrate that is refillable with hydrogen. This property makes it a possible storage material for gases. By analyzing neutron diffraction data and calculations based on density-functional theory, we show that sX is also refillable with nitrogen; the guest:host ratio will be shown to be 2.6(3). Furthermore, we report sX's decomposition behavior and give evidence that it undergoes several transitions into the exotic hydrates sH and sIII that have not been observed at these pressure and temperature conditions—before forming the stable nitrogen hydrate sII. [ABSTRACT FROM AUTHOR]

Clathrate hydrates are crystalline compounds consisting of water molecules forming cages (so-called "host") inside of which "guest" molecules are encapsulated depending on the thermodynamic conditions of formation (systems stable at low temperature and high pressure). These icelike systems are naturally abundant on Earth and are generally expected to exist on icy celestial bodies. Carbon monoxide hydrate might be considered an important component of the carbon cycle in the solar system since CO gas is one of the predominant forms of carbon. Intriguing fundamental properties have also been reported: the CO hydrate initially forms in the sI structure (kinetically favored) and transforms into the sII structure (thermodynamically stable). Understanding and predicting the gas hydrate structural stability then become essential. The aim of this work is, thereby, to study the structural and energetic properties of the CO hydrate using density functional theory (DFT) calculations together with neutron diffraction measurements. In addition to the comparison of DFT-derived structural properties with those from experimental neutron diffraction, the originality of this work lies in the DFT-derived energy calculations performed on a complete unit cell (sI and sII) and not only by considering guest molecules confined in an isolated water cage (as usually performed for extracting the binding energies). Interestingly, an excellent agreement (within less than 1% error) is found between the measured and DFT-derived unit cell parameters by considering the Perdew-Burke-Ernzerhof (denoted PBE) functional. Moreover, a strategy is proposed for evaluating the hydrate structural stability on the basis of potential energy analysis of the total nonbonding energies (i.e., binding energy and water substructure nonbonding energy). It is found that the sII structure is the thermodynamically stable hydrate phase. In addition, increasing the CO content in the large cages has a stabilizing effect on the sII structure, while it destabilizes the sI structure. Such findings are in agreement with the recent experimental results evidencing the structural metastability of the CO hydrate. [ABSTRACT FROM AUTHOR]

In order to realize the synergistic utilization of calcium silicon slag, fly ash and blast-furnace slag, this paper researched on hydration mechanism of calcium silicon slag composite geopolymer through preparation experiments of the calcium silicon slag composite geopolymer under different ratio of fly ash / blast-furnace slag.The results show that the calcium silicate slag base geopolymer is a binary composite cementitious material mainly composed of C—S—H and C(N)—A—S—H, which is formed by the hydration of β-calcium silicate itself and alkali-activated hydration.Compared with crystalline minerals, glass minerals are more prone to reaction with Ca(OH)2 and sodium silicate, resulting in a large amount of unreacted mullite remaining in the hydrates of 7 d when the fly ash / blast-furnace slag ratio is more than 0.5, but the mullite will continue to hydrate with the extension of curing time, and worm-like tetranatrolite and strip-like beidellite will be formed at 28 d.At the same time, when fly ash / blast-furnace slag ratio is 1.0, micromorphology of calcium silicate slag composite geopolymer is the most evenly distributed and dense, and its 28 d compressive strength reaches maximum 37.9 MPa.So, it indicates that the best synergistic effect among calcium silicon slag, fly ash and blast-furnace slag can be released under this condition.

Metal‐organic frameworks (MOFs) are porous, crystalline materials constructed from organic linkers and inorganic nodes with myriad potential applications in chemical separations, catalysis, and drug delivery. A major barrier to the application of MOFs is their poor scalability, as most frameworks are prepared under highly dilute solvothermal conditions using toxic organic solvents. Herein, we demonstrate that combining a range of linkers with low‐melting metal halide (hydrate) salts leads directly to high‐quality MOFs without added solvent. Frameworks prepared under these ionothermal conditions possess porosities comparable to those prepared under traditional solvothermal conditions. In addition, we report the ionothermal syntheses of two frameworks that cannot be prepared directly under solvothermal conditions. Overall, the user‐friendly method reported herein should be broadly applicable to the discovery and synthesis of stable metal‐organic materials. [ABSTRACT FROM AUTHOR]

The motion of the ion pairs under the applied electric field is an important phenomenon in the storage properties of the capacitive devices. In this study, two different molecules, 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt hydrate (P4) and tetra-alkyl ammonium bromide (TAAB), were used as ionic groups in the PVA gel electrolytes. The counter ions of P4 and TAAB are Na+ and Br – and their masses (about 23 and 80 g/mole) are much smaller than the masses of their host molecules P 4 - 4 and TAAB+1 (about 524 and 322 g/mole). Three different PVA gel electrolytes in slab configurations were synthesized and characterized: PVA gel electrolyte including only P4, only TAAB, and mixture of these ionic groups. The binary system was obtained by putting the gel electrolyte including TAAB on the gel electrolyte including P4. cyclic voltammetry (CV), and galvanostatic charge discharge (GCD) techniques were used to characterize the electrolytes. The results of the proposed binary gel polymer electrolyte were compared with single and mixture electrolytes. It was observed that since P4 and TAAB host molecules are highly massive, they can shield some part of the counter ions when an electric field was applied. In addition, the agglomeration of the TAAB molecules in the PVA matrix causes trapping the counter ions in the dense regions and prevents the motion of the counter ions under the applied field and then induces the increasing internal resistance. Therefore, the effective mass of TAAB molecules increases considerably, and when an electric field is applied, they move slowly. [ABSTRACT FROM AUTHOR]

Thermal stimulation is an important method to promote gas production and to avoid secondary hydrate formation during hydrate exploitation, but low thermal efficiency hinders its application. In this work, hydrate dissociation was carried out in synthesized hydrate-bearing sediments with 30% hydrate saturation at 6.9 MPa and 9 °C. Ionic liquids, such as 1-butyl-3-methylimidazolium chloride (BMIM-Cl) and tetramethylammonium chloride (TMACl), were injected as heat carriers, and the promotion effects were compared with the injection of hot water and brine. The results showed that the injection of brine and ionic liquids can produce higher thermal efficiencies compared to hot water. Thermodynamic hydrate inhibitors, such as NaCl, BMIM-Cl, and TMACl, were found to impair the stability of CH4 hydrate, which was conducive to hydrate dissociation. By increasing the NaCl concentration from 3.5 to 20 wt%, the thermal efficiency increased from 37.6 to 44.0%, but the thermal efficiencies experienced a fall as the concentration of either BMIM-Cl or TMACl grew from 10 to 20 wt%. In addition, increasing the injection temperature from 30 to 50 °C was found to bring a sharp decrease in thermal efficiency, which was unfavorable for the economics of gas production. Suitable running conditions for ionic liquids injection should control the concentration of ionic liquids under 10 wt% and the injection temperature should be around 10 °C, which is conducive to exerting the weakening effect of ionic liquids on hydrate stability. [ABSTRACT FROM AUTHOR]

Recent years have seen increasing attention to TCES technology owing to its potentially high energy density and suitability for long-duration storage with negligible loss, and it benefits the deployment of future net-zero energy systems. This paper provides a review of salt hydrate adsorption material-based TCES for space heating applications at ~150 °C. The incorporation of salt hydrates into a porous matrix to form composite materials provides the best avenue to overcome some challenges such as mass transport limitation and lower thermal conductivity. Therefore, a systematic classification of the host matrix is given, and the most promising host matrix, MIL-101(Cr)(MOFs), which is especially suitable for loading hygroscopic salt, is screened from the perspective of hydrothermal stability, mechanical strength, and water uptake. Higher salt content clogs pores and, conversely, reduces adsorption performance; thus, a balance between salt content and adsorption/desorption performance should be sought. MgCl2/rGOA is obtained with the highest salt loading of 97.3 wt.%, and the optimal adsorption capacity and energy density of 1.6 g·g−1 and 2225.71 kJ·kg−1, respectively. In general, larger pores approximately 8–10 nm inside the matrix are more favorable for salt dispersion. However, for some salts (MgSO4-based composites), a host matrix with smaller pores (2–3 nm) is beneficial for faster reaction kinetics. Water molecule migration behavior, and the phase transition path on the surface or interior of the composite particles, should be identified in the future. Moreover, it is essential to construct a micromechanical experimental model of the interface. [ABSTRACT FROM AUTHOR]