Microscopic Reaction Mechanism Research Articles

High-Resolution Crossed-Beam Dynamics Studies of the D + Para-H2 → HD + H Reaction at 1.21 eV.

Understanding kinetic isotope effects is important in the study of the reaction dynamics of elementary chemical reactions, particularly those involving hydrogen atoms and molecules. As one of the isotopic variants of the hydrogen exchange reaction, the D + para-H2 reaction has attracted much attention. However, experimental studies of this reaction have been limited primarily due to its strong experimental background noise. In this study, by using the velocity map ion imaging method and the near-threshold ionization technique, together with improvements on the vacuum condition in the vicinity of the collision zone, background noise was reduced significantly, and quantum state-resolved differential cross sections (DCSs) for the D + para-H2 reaction at a collision energy of 1.21 eV were acquired in a crossed molecular beams experiment. Interestingly, clear rotational state-dependent angular distributions were noticed in the quantum state-resolved DCSs. The most intense peak's positions for HD (v', j') products shift to different scattering directions as the product's ro-vibrational quantum number increases. Two different microscopic reaction mechanisms are found to be involved in this reaction for HD products in different vibrational states. The results show a direct correlation between the scattering angle and the product's rotational quantum number, revealing that the contributions of impact parameters are strongly influenced by the corresponding centrifugal barrier.

Microscopic Chemical Reaction Mechanism and Kinetic Model of Al/PTFE

Microscopic Chemical Reaction Mechanism and Kinetic Model of Al/PTFE

Curing kinetics and plugging mechanism of high strength curable resin plugging material

Lost circulation, a recurring peril during drilling operations, entails substantial loss of drilling fluid and dire consequences upon its infiltration into the formation. As drilling depth escalates, the formation temperature and pressure intensify, imposing exacting demands on plug materials. In this study, a kind of controllable curing resin with dense cross-network structure was prepared by the method of solution stepwise ring-opening polymerization. The resin plugging material investigated in this study is a continuous phase material that offers effortless injection, robust filling capabilities, exceptional retention, and underground curing or crosslinking with high strength. Its versatility is not constrained by fracture-cavity lose channels, making it suitable for fulfilling the essential needs of various fracture-cavity combinations when plugging fracture-cavity carbonate rocks. Notably, the curing duration can be fine-tuned within the span of 3 to 7 h, catering to the plugging of drilling fluid losing of diverse fracture dimensions. Experimental scrutiny encompassed the rheological properties and curing behavior of the resin plugging system, unraveling the intricacies of the curing process and establishing a cogent kinetic model. The experimental results show that the urea-formaldehyde resin plugging material has a tight chain or network structure. When the concentration of the urea-formaldehyde resin plugging system solution remains below 30%, the viscosity clocks in at a meager 10 mPa·s. Optimum curing transpires at 60 ºC, showcasing impressive resilience to saline conditions. Remarkably, when immersed in a composite saltwater environment containing 50000 mg/L NaCl and 100000 mg/L CaCl2, the urea-formaldehyde resin consolidates into an even more compact network structure, culminating in an outstanding compressive strength of 41.5 MPa. Through resolving the correlation between conversion and the apparent activation energy of the non-isothermal DSC curing reaction parameters, the study attests to the fulfillment of the kinetic equation for the urea-formaldehyde resin plugging system. This discerning analysis illuminates the nuanced shifts in the microscopic reaction mechanism of the urea-formaldehyde resin plugging system. Furthermore, the pressure bearing plugging capacity of the resin plugging system for fractures of different sizes is also studied. It is found that the resin plugging system can effectively resident in parallel and wedge-shaped fractures of different sizes, and form high-strength consolidation under certain temperature conditions. The maximum plugging pressure of resin plugging system for parallel fractures with outlet size 3 mm can reach 9.92 MPa, and the maximum plugging pressure for wedge-shaped fractures with outlet size 5 mm can reach 9.90 MPa. Consequently, the exploration and application of urea-formaldehyde resin plugging material precipitate a paradigm shift, proffering novel concepts and methodologies in resolving the practical quandaries afflicting drilling fluid plugging.

In-situ template method to synthesize metal/non-metal doped carbon for SO2 adsorption at low concentration: DFT and experimental studies

SO2 is one of the most significant air molecular contaminants (AMC). The development of materials for capturing low-concentration SO2 at room temperature is of great importance for industrial production and environmental safety. In this study, hierarchical porous carbon materials with Zn–N–C active structures were synthesized in one step using an in-situ template method. Among them, Zn/AC-2 exhibited a high specific surface area (1143.73 m2/g) and micropore volume (0.42 cm3/g). Dynamic adsorption tests were conducted under the conditions of an inlet concentration of 90 ppm, with a temperature of 23 °C and a humidity of 50%. The results indicated that the material showed an excellent capturing performance for SO2, with a breakthrough adsorption capacity of 3.37 mmol/g. Through characterization techniques including XPS, XRD, and SEM-EDS, it was found that the metal elements were dispersed in atomic form within the carbon framework, demonstrating the effectiveness of the modification method. A comparative study of the new adsorbent and spent adsorbent proved that SO2 reacts with extremely high catalytic efficiency on the material surface to generate SO3, revealing the reaction mechanism on the material surface. Finally, based on density functional theory, the microscopic reaction mechanism of the interaction between SO2 and the prepared material surface was studied at the molecular level. The results showed that the reaction energy barrier on the material surface is only 1.01 eV, and the reaction releases 3.14 eV of energy, indicating that the reaction can spontaneously occur at room temperature.

Reaction mechanism and light gas conversion in pyrolysis and oxidation of dimethyl ether (DME): A ReaxFF molecular dynamics study

To uncover the microscopic reaction mechanisms of dimethyl ether (DME) pyrolysis and oxidation, reactive molecular dynamics simulations were employed to investigate the reaction processes under various O2/DME ratios and impurity environments at 2200 K–3200 K. The results show that DME pyrolysis begins with a decomposition reaction of CH3OCH3 → CH3O + CH3, ultimately leading to the formation of CO, H2 and PAHs. The reaction pathways of DME oxidation contain light gas conversion and combustion. In fuel rich conditions, the oxidation produces mainly H2 and CO, while in fuel lean conditions, the oxidation products tend to be H2O and CO2. The carbon components of DME are completely converted into CO2 and CO regardless of O2 content. In the presence of impurities H2O or CO2, the oxidation reaction pathway is altered, causing consumption and transformation of these impurities into active radicals such as OH, further promoting the progress of the reaction. The top three light gases produced are hydrogen, methanol and methane, and increasing H2 production in the DME oxidation process can be achieved through both oxygen subtraction and water addition. The rate of formaldehyde generation during pyrolysis is higher than that during oxidation. However, a higher oxygen content leads to increased formaldehyde production.

ReaxFF molecular dynamics simulations of methane clathrate combustion.

Understanding the ignition and dynamic processes for the combustion of hydrate is crucial for efficient energy utilization. Through reactive force field molecular dynamics simulations, we studied the high-temperature decomposition and combustion processes of methane hydrates in a pure oxygen environment. We found that at an ignition temperature of 2800K, hydrates decomposed from the interface to the interior, but the layer-by-layer manner was no longer strictly satisfied. At the beginning of combustion, water molecules reacted first to generate OH•, followed by methane oxidation. The combustion pathway of methane is CH4→CH3•→CH3O•→CH2O→HC•O→HCOO•→CO(CO2). During the combustion process, a liquid water layer was formed between melted methane and oxygen, which hindered the reaction's progress. When there is no heat resistance, oxygen will transform into radicals such as OH• and O•, which have faster diffusion rates, allowing oxygen to conveniently cross the mass transfer barrier of the liquid water layer and participate in the combustion process. Increasing the amount of OH• may cause a surge in the reaction. On the other hand, when significant heat resistance exists, OH• is difficult to react with low-temperature hydrate components, but it can transform into O• to trigger the oxidation of methane. The H• generated has a sufficient lifetime to contact high-temperature oxygen molecules, converting oxygen into radicals that easily cross the water layer to achieve mass transfer. Therefore, finding ways to convert oxygen into various radicals is the key to solving the incomplete combustion of hydrates. Finally, the reaction pathways and microscopic reaction mechanisms of each species are proposed.

Ab Initio Density Functional Theory Calculation: Americium Hydrolysis Mechanism.

The hydrolysis mechanism of americium was calculated using density functional theory, and the detailed microscopic reaction mechanism was obtained. The results show that americium reacts with water along the octet state to produce oxides and H2, and that this reaction is exothermic. The interaction between Am and O atoms gradually changes from initially electrostatic interaction to covalent interaction, and continues to strengthen. During the reaction process, Am atoms always lose electrons, the 5f orbital is obviously involved, and there is df orbital hybridization. This study provides the necessary theoretical data support for the theoretical and experimental study of the actinide system.

First-row transition metal carbide nanosheets as high-performance cathode materials for lithium-sulfur batteries.

Despite the prodigious potential of lithium-sulfur (Li-S) batteries as future rechargeable electrochemical systems, their commercial implementation is hindered by several vital issues, including the shuttle effect and sluggish migration of lithium-polysulfides leading to rapid capacity fading. Here, we systematically investigate the potential of first-row two-dimensional transition metal carbides (TMCs) as sulfur cathodes for Li-S batteries. The adsorption strength of lithium-polysulfides on TMCs is induced by the amount of charge transfer from the former to the latter and the proposed periodic relationship between sulfur in Li2S and 3d-transition metals. Our findings show that the VC nanosheet possesses immense anchoring potential and exhibits a comparatively low migration energy barrier for lithium-ion and Li2S molecules. Additionally, we report ab initio molecular dynamics simulations for lithiated polysulfide species anchored on a TMC-based model with a liquid-electrolyte medium. The microscopic reaction mechanism, revealed by the evolution of the reaction voltage during lithiation, demonstrates that the dissolution of high-order lithium-polysulfides in the electrolytes can be prevented due to their robust interaction with TMC-based cathode materials. These appealing features suggest that TMCs present colossal performance improvements for anchoring lithium-polysulfides, stimulating the active design of sulfur cathodes for practical Li-S batteries.

Chemical looping CO2 capture and in-situ conversion: Fundamentals, process configurations, bifunctional materials, and reaction mechanisms

As an emerging and promising technology to debate the energy and environment issues raised by anthropogenic CO2 emissions, chemical looping CO2 capture and in-situ conversion (CL-ICCC) exhibits the merit of high efficiency, low cost, and high safety to achieve integrated CO2 capture and conversion (ICCC) by eliminating the purification, compression, transportation, and storage procedures. However, the interpretation and state-of-the-art of CL-ICCC are still unclear, which contribute to a harmful effect on promoting this technology for industrial applications. Herein, this work presents a timely review on CL-ICCC by giving fundamental discussions on definition, process configuration, bifunctional material, reaction mechanism and thermo-economic behavior. Based on the product distributions (syngas, CO, CH4, C2H4/C3H6), CL-ICCC systems using abundant bifunctional materials with flexible combinations of sorbents and catalysts are classified to satisfy the demand of customers. Lots of moderating strategies are proposed to enhance the activity and stability of bifunctional material, meanwhile, reaction mechanism is revealed to explain the underlying reason for superior performance. The challenges and future prospectives from the aspects of microscopic reaction mechanism, bifunctional material rational design, reaction equipment development and system integration and optimization are discussed to provide possible suggestions. This review aims to illustrate CL-ICCC more clearly and accelerate its commercial demonstration.

Mixed-terminal MXenes react with SF6 in aqueous solution: reaction mechanism and pathway

The search for an ecofriendly treatment for the strong greenhouse gas SF6 has become a global hot issue. Herein, the mixed-terminal Ti3C2T x MXene catalyzing conversion of SF6 in aqueous solution was explored. The catalytic network on realistic Ti3C2T x was constructed. By theoretical calculations, target products and the microscopic reaction mechanism were studied. Firstly, SF6 exhibited different degrees of chemisorption on the constructed Ti3C2T x surfaces of three varying terminal proportions, with different terminals showing synergistic effects. Secondly, taking the effect of H2O and surface hydroxyl into account, the catalytic conversion system of SF6 on a Ti3C2(OH)0.66O1.33 surface was constructed, containing 25 sub-reactions with H2S as one of the final products. SF6 went through successive defluorination on the Ti3C2(OH)0.66O1.33 surface to form low-fluorine sulfide SF x (x = 5, 4, 3, 2, 1), with energy of 80.685 kcal mol−1 released during the whole process. The energy barriers of all the SF6 decomposition sub-reactions were significantly lower than that in free space. Besides, O terminals were regarded as potential hydroxyl terminals in aqueous solution, which continuously provided active hydroxyl groups for the Ti3C2(OH)0.66O1.33 surface. Thus, SF6 conversion in aqueous solution will not result in deactivation of Ti3C2T x catalyst. This work provides a theoretical basis for MXene to catalyze SF6 decomposition in an efficient way.

Peroxymonosulfate (PMS) activated by magnetic Fe3O4 doped carbon quantum dots (CQDs) for degradation of Rhodamine B (RhB) under visible light: DFT calculations and mechanism analysis

Currently, photo-assisted peroxymonosulfate (PMS) activation has received more and more attention in the degradation of wastewater pollutants. In this paper, the Fe3O4@CQDs magnetic nanocatalyst was successfully prepared by modifying α-Fe2O3, and Rhodamine B (RhB) was degraded by activating PMS under visible light. Moreover, in order to explore the reason why Fe3O4@CQDs was more beneficial to the activation of PMS than α-Fe2O3 at the microscopic level and reaction mechanism, the corresponding DFT calculations were performed. The results revealed that the degradation efficiency of RhB reached 98% in 35 min. Subsequently, the quenching experiments and EPR tests jointly verified that SO4•-, •OH, O2•- free radical pathway and 1O2, h+ non-free radical pathway participated in the degradation of RhB in the Fe3O4@CQDs + PMS + light system. The adsorption energy reached −5.247 eV with Fe3O4@CQDs adsorbed PMS by DFT calculation. The electron enrichment and charge redistribution can be apparently observed during the adsorption of PMS at Fe3O4@CQDs nanocatalyst. It was confirmed that the embedding of CQDs effectively regulated the electron transfer efficiency at the Fe3O4@CQDs interface to promote the improvement of electrical conductivity. It was more conducive to forming Fe(Ⅲ) to Fe(Ⅱ) cycles, and then the ability of the catalyst to activate PMS was improved.

Macroscopic behaviors and chemical reaction mechanism for the inhibition of NH4H2PO4 powder in hybrid methane/coal dust deflagrations

In this research, the inhibition effect and microscopic mechanism of NH4H2PO4 on the macroscopic deflagration characteristics of methane (9.5 vol%) mixed with three coal samples were studied. Experimental results show that the higher the concentration of added NH4H2PO4, the more pronounced the inhibition effect on the deflagration of three coal samples mixed with methane. When the mass concentration of NH4H2PO4 reached 90%, the deflagration pressures of anthracite/methane hybrids, coking coal/methane hybrids, and long-flame coal/methane hybrids decreased by 50.80%, 45.59%, and 39.06%, respectively. The time for the flame front to reach the height of 300 mm extended by 39 ms, 30 ms, and 63 ms, respectively. In addition, the microscopic reaction mechanism of NH4H2PO4 inhibiting the methane/coal dust deflagration was revealed using a reaction kinetics model. We found that phosphorus-containing substances mainly absorbed explosive active free radicals through cyclic reactions HOPO2 = PO2 and HOPO = PO2. Through ROP analysis, we found that with an increase in inhibitor concentration, the HOPO radical, which had a better scavenging effect on oxidizer free radicals, was gradually replaced by HOPO2, resulting in a saturation effect. Sensitivity analysis showed that the inhibitory effect of NH4H2PO4 mainly depended on phosphorous substances and free radicals HOPO, HOPO2, and PO2.

Study on the microcosmic mechanism of inhibition of coal spontaneous combustion by antioxidant diphenylamine

Diphenylamine has been applied to suppress coal spontaneous combustion with good results, but its microscopic reaction mechanism is not clear. In this paper, the free radical reaction process of coal spontaneous combustion is calculated more systematically, and the quantum chemical method is applied to analyze in detail the process of diphenylamine depletion of reactive free radicals in coal from three perspectives: hydrogen atom transfer, direct radical capture, and regeneration cycle chain. By destroying the molecular structure of coal to generate free radicals as the initial condition of coal spontaneous combustion, the oxidation process of the free radical chain reaction was analyzed, the thermodynamic data of all reactions were calculated, the microscopic mechanism of free radical capture by diphenylamine was revealed, and the transition state structure model of the reaction process was given. The active sites of each reactant were determined by quantitative molecular surface analysis, the spontaneity of the reaction was measured by the free energy change, and the interaction relationship between different conformations was graphically represented by applying the IRI (interaction region indicator) method. The results show that most of the free radical reactions during the spontaneous combustion of coal are exothermic, and they provide heat for the spontaneous combustion of coal, which can react directly with oxygen when accumulated to a certain temperature. Diphenylamine can break the N-H bond, allowing hydroxyl radicals and carbon radicals to obtain hydrogen atoms to form stable compounds, and the generated diphenylamine radicals can reduce the content of free radicals in coal by direct capture. In addition, the process of diphenylamine inhibition of coal spontaneous combustion has a circular regeneration chain, which can indeed effectively reduce the content of reactive radicals and inhibit the spontaneous combustion of coal, which is reflected in the macroscopic level of reducing the generation of coal spontaneous combustion indicator gas, which is consistent with the experimental results.

Reactive behaviors and mechanisms of cellulose in chemical looping combustions with iron-based oxygen carriers: An experimental combined with ReaxFF MD study

Biomass energy is one of the important and feasible renewable energy resources. Chemical looping combustion (CLC) can meet the requirements of efficient CO2 capture with low energy consumption. The combination of the two factors is intuitive and important for realizing carbon neutral energy processing and conversion. Cellulose is the component with the highest content in biomass. However, there is still a lack of clear understanding of the thermal conversion behavior and microscopic reaction mechanism of cellulose in CLC. In this work, the behaviors and mechanisms of cellulose in CLC with iron-based OCs were studied systematically based on the comprehensive technics of thermo-gravimetric analysis (TGA) experiments, kinetic models and molecular dynamic simulations. The reaction behaviors, kinetic mechanism, and complex reactive networks of cellulose under complex environmental interface conditions of CLC were revealed. Three different stages were revealed for thermal weight loss and reaction behavior of cellulose in CLC via TGA. The effects of different conversion rates and reaction stages on activation energy during CLC were described based on two model-free integration methods. The dynamic evolution of the CLC process was discussed by ReaxFF MD (reactive force field molecular dynamics) simulations. A complex reaction network of cellulose depolymerization and CO2 release in CLC was obtained.

Microscopic oxidation reaction mechanism of methanol in H2O/CO2 impurities: A ReaxFF molecular dynamics study

In this study, the ReaxFF molecular dynamics (MD) simulations were performed to investigate the dynamic evolution of reactants and intermediates in the oxidation reaction of methanol, the oxidation reaction path was determined, and the effects of O2/methanol ratio and H2O/CO2 impurity on the oxidation were explored. The results indicate the consumption rate of methanol is significantly higher than that of O2, and the preferred product of the reaction are H2O, H2, CO and CO2. With the increase of reaction temperature, the consumption rate of reactants increases, which promotes the formation of intermediate products in advance, resulting in the increase of products. The amount of final products of H2O, H2, CO and CO2 at 3000 K under fuel rich condition is 1.59, 4.07, 4.36 and 3.20 times that at 2400 K, respectively. The presence of H2O/CO2 impurities promote the initial dissociation of methanol, and inhibits the consumption of O2 and the generation of H2O. The presence of CO2 impurities can promote the generation of CO. The activation energy is lowest in the CO2 impurity environment. This study provides a microscopic insight into the oxidation mechanism of methanol in various environment.

Mechanism study on direct synthesis of glycerol carbonate from CO2 and glycerol over shaped CeO2 model catalysts

Direct synthesis of glycerol carbonate (GC) from CO2 and glycerol (a byproduct of biodiesel production) is a route to obtain a high-value chemical from waste and low-cost byproducts but has not yet industrialized due to the lack of efficient catalysts. Ceria (CeO2) exhibits the highest catalytic activity and GC selectivity among the heterogeneous catalysts studied so far. However, the mechanism of this reaction over CeO2 catalysts has not been studied in detail. Herein, we synthesized CeO2 nanocrystals with different morphologies as model catalysts that can predominantly expose {111}, {110}, and {100} facets, and their surface acid-base properties were characterized using high-sensitivity temperature-programmed desorption of NH3 and CO2 with quadrupole mass spectrometry as detector (NH3-TPD-QMS and CO2-TPD-QMS). We found that the catalytic performance (GC formation rate) is strictly linearly dependent on the density of basic sites, which is relevant to the adsorption and activation of CO2. In addition, to illustrate a more microscopic reaction mechanisms underlying the formation of GC from CO2 and glycerol on all three low-index surfaces (111), (110) and (100), we also performed comprehensive first principles calculations. A three-step Langmuir–Hinshelwood (LH) mechanism was identified in which the annulation reaction is the rate-limiting step. The CeO2 (111) surface exhibits the lowest overall activation energy, which agrees well with the catalytic performance that the CeO2 nano-octahedra, predominantly exposing {111} facets, have the highest GC formation rate. This work is the first to combine experiments on shaped CeO2 model catalysts with first-principles calculations to gain insight into the mechanism of direct synthesis of GC from CO2 and glycerol, and will aid in the development of catalysts with improved performance.

Noncovalent interactions on the electrocatalytic oxidation of ethanol on a Pt/C electrocatalyst

AbstractDue to their environmentally friendly nature and high energy density, direct ethanol fuel cells have attracted extensive research attention in recent decades. However, the actual Faraday efficiency of the ethanol oxidation reaction (EOR) is much lower than its theoretical value and the reaction kinetics of the EOR is sluggish due to insufficient active sites on the electrocatalyst surface. Pt/C is recognized as one of the most promising electrocatalysts for the EOR. Thus, the microscopic interfacial reaction mechanisms of the EOR on Pt/C were systematically studied in this work. In metal hydroxide solutions, hydrated alkali cations were found to bind with OHad through noncovalent interactions to form clusters and occupy the active sites on the Pt/C electrocatalyst surface, thus resulting in low Faraday efficiency and sluggish kinetics of the EOR. To reduce the negative effect of the noncovalent interactions on the EOR, a shield was made on the electrocatalyst surface using 4‐trifluoromethylphenyl, resulting in twice the EOR catalytic reactivity of Pt/C.

The reaction mechanism of Al NPs/PVDF high energy fuel: A ReaxFF MD and DFT study meshing together laser-ignition experimental verification

Aluminum nanoparticles (Al NPs) with the high energy can be used in rocket propulsion, but the propellant performance will be limited by the easy agglomeration property. The surface modification of Al NPs by polyvinylidene fluoride (PVDF) can inhibit their agglomeration and improve their combustion efficiency. However, there is a lack of essential understanding of the microscopic reaction mechanism of PVDF to promote the combustion of Al NPs. Hence, the oxidation and combustion processes of Al NPs/PVDF were investigated by using reactive molecular dynamics (RMD) simulations and density functional theory (DFT) calculations. Moreover, the combustion performance of Al NPs/PVDF was examined by laser ignition experiments. In the oxidation of Al NPs/PVDF, the PVDF is decomposed by the catalytic action of Al NPs. The dissociated F atoms react with the oxide shell to form AlxOyFz species, which elucidates the mechanism of the pre-ignition reaction of Al NPs with PVDF at the microscopic level. In the combustion of Al NPs/PVDF, the increase in PVDF content and temperature is favorable to the consumption of Al NPs. The experimental results also verify that the addition of PVDF can significantly enhance the combustion performance of Al NPs. These results reveal the promotion effects of PVDF on Al NPs in the ignition and combustion process at the atomic level and the macroscopic perspective, and lay the theoretical foundation for the early application of Al NPs/PVDF in propellants.

Preparation of controlled low-strength materials from alkali-excited red mud-slag-iron tailings sand and a study of the reaction mechanism.

To address the low utilization of fines in iron tailings sand (IOTs), a controlled low-strength material (CLSM) was prepared from a combination of fine IOTs and red mud (RM) slag. The 7-day unconfined compressive strength (7-d UCS), slump and cost were used as evaluation indicators, and 16 sets of tests were designed with the Box-Behnken design (BBD) response surface method. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS) were used to study the microscopic morphology and reaction mechanism of the CLSM samples made with the optimal ratios. The results show that the best matching ratio for the alkali-activated RM-slag-IOTs CLSM was a sand ratio of 0.797, an NaOH dose of 3.667% and a mass concentration of 80.657%, and the 7d-UCS, slump and cost indicators verified the feasibility of applying the CLSM to the base course of pavement. Alkali activation of the CLSM also showed that the RM-slag cementation system produced new substances. Internal calcium-silicate-hydrogel (C-S-H) and calcium-aluminosilicate-hydrogel (C-A-S-H) agglomerates were the main sources of strength, and hydration products were interwoven to form a dense structure with crystals as the framework and gels as fillers.

Unraveling Atomic-Scale Origins of Selective Ionic Transport Pathways and Sodium-Ion Storage Mechanism in Bi2 S3 Anodes.

It is a major challenge to achieve a high-performance anode for sodium-ion batteries (SIBs) with high specific capacity, high rate capability, and cycling stability. Bismuth sulfide, which features a high theoretical specific capacity, tailorable morphology, and low cost, has been considered as a promising anode for SIBs. Nevertheless, due to a lack of direct atomistic observation, the detailed understanding of fundamental intercalation behavior and Bi2 S3 's (de)sodiation mechanisms remains unclear. Here, by employing in situ high-resolution transmission electron microscopy, consecutive electron diffraction coupled with theoretical calculations, it is not only for the first time identified that Bi2 S3 exhibits specific ionic transport pathways preferred to diffuse along the (110) direction instead of the (200) plane, but also tracks their real-time phase transformations (de)sodiation involving multi-step crystallographic tuning. The finite-element analysis further disclosed multi-reaction induced deformation and the relevant stress evolution originating from the combined effect of the mechanical and electrochemical interaction. These discoveries not only deepen the understanding of fundamental science about the microscopic reaction mechanism of metal chalcogenide anodes but also provide important implications for performance optimization.