Fluidity is a critical property of cement that significantly impacts the performance of cement paste in construction engineering. Fluidity is typically enhanced through the application of chemical additives (e.g., water-reducing agents). While chemical additives can enhance the fluidity and workability of cement, their drawbacks, such as cost and environmental impact, must be carefully considered. Most of the current research focuses on the use of chemical admixtures, while studies on physical alternatives remain limited. This study employs molecular dynamics (MD) simulation to propose an innovative strategy for improving the fluidity of cement slurry by applying an electric field, which acts as a physical water reducer. This research investigates the lubricating effect and underlying mechanism of the electric field on cement hydration product C-S-H particles at the nanoscale. This work demonstrates that increasing the electric field strength significantly reduces friction between cement particles, thereby improving fluidity when ions are present at the particle interface. Atomic-level structural analyses reveal that the electric field promotes a denser C-S-H structure and facilitates ion desorption from the C-S-H surface, which acts as a lubricant between particles. This study provides new insights into how an electric field can serve as a lubricant in cement systems, offering a promising approach to enhancing concrete fluidity without relying on chemical admixtures.

Natural gas is a critical global energy source, yet it often contains contaminants such as CO2 and H2S, which pose risks of toxicity, equipment corrosion, and reduced calorific value. Effective removal of these acidic gases is essential for economic and safety considerations. While numerous studies have focused on screening potential ionic liquids (ILs) for separation, significant limitations persist where many existing studies tend to prioritize molecular mechanism screening using quantum chemistry or machine learning without validating IL effectiveness through process simulations. Further, some existing studies focus on either H2S or CO2, neglecting the simultaneous absorption of both gases. Lastly, the dataset used in existing investigations are often limited, restricting the comprehensiveness of findings. It is therefore the purpose of this paper to address these gaps by systematically screening a large dataset of 16,470 ILs for acid gas removal, ultimately narrowing the candidates to six for process simulation in Aspen Plus, i.e., [BF4][EMPY], [BF4][EMIM], [BF4][DMPY], [BF4][NMPY], [MEET][TMEA], and [MEET][DMPY]. The results indicate that [MEET][DMPY] effectively reduced CO2 from 150 kg/h to 9.17 kg/h and H2S from 50 kg/h to 2.01 kg/h, establishing it as a promising candidate for acid gas removal processes. Overall, this study emphasizes the critical importance of assessing the effectiveness of screened solvents through process simulation, regardless of the screening methods employed.

A modified structured dry water (SCDW) was prepared by introducing sodium alginate (SA) and calcium Llactate (CL) into conventional dry water (DW) to mitigate the risks associated with methane-air explosions. The preparation parameters were optimized, yielding uniformly distributed and structurally stable particles. The results demonstrate that SCDW exhibits superior mechanical stability and water retention compared to DW. Pipeline explosion experiments evaluated the suppression performance of six sodium-and potassium-modified SCDWs. At spraying concentrations of 25-100 g/m3, all modified SCDWs significantly reduced the maximum explosion pressure and flame propagation distance, outperforming DW. Specifically, 5 wt% KCl-SCDW at 100 g/ m3 reduced the maximum explosion pressure and flame propagation distance by 38.75 % and 24.10 %, respectively, compared to DW. When the spraying concentration exceeded 200 g/m3, both parameters stabilized. A quantitative analysis of five explosion-related parameters confirmed that salt-modified SCDWs provided superior suppression performance compared to DW, with potassium-modified SCDWs exhibiting stronger effects than sodium-modified ones, and KCl-SCDW demonstrating the best suppression performance. HSC and Chemkin simulations revealed that SCDW exerts both physical and chemical suppression effects. Physically, DW particles suppress combustion through evaporative cooling, oxygen dilution, energy absorption from particle collisions, and thermal radiation blocking. Chemically, gaseous active species capture and consume H and OH free radicals, interrupting chain reactions through catalytic cycles and generating stable compounds, thereby reducing the maximum explosion pressure and flame propagation speed. Modified SCDWs offer an environmentally friendly, stable, and efficient approach to methane-air explosion suppression.

In the realm of eco-friendly metal pretreatment methods as a substitute for chromates, silanes have emerged as a prominent option for augmenting the adhesion of polymer coatings onto the surfaces of carbon steel. However, there exists a notable dearth of research at the nanoscale, delving into the interaction between silanes and carbon steel surfaces. To address this gap, silane coatings were applied on the carbon steel surface via an electrodeposition process. A comprehensive investigation was conducted to elucidate the interfacial bonding characteristics and corrosion inhibition mechanism between silanes and hydroxylated carbon steel surfaces using an array of analytical techniques, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations. The results revealed that the silane layer achieved stable adsorption, with a contact angle of 91.29°, forming a robust interface with the passivation layer on the carbon steel surface. The hydrogen bonding interactions between the silanol groups in the silane molecules and the hydroxyl groups within the passivation film on the carbon steel surface were identified as the primary mechanism responsible for this adsorption. This integrated approach combining experimental and computational methods provides new insights into the interfacial bonding and corrosion inhibition behavior of silane coatings, thereby offering a scientific foundation for their practical application in metal protection systems.

The characteristics of magnesium phosphate cement, such as fast setting, high early strength, and good bonding properties, have led to its wide application. However, its poor water resistance is a common drawback, often addressed by adding materials like fly ash (FA) to improve it. In magnesium phosphate cement (MPC), FA undergoes a chemical reaction, but the influence of the aluminum-silicon glass phase in its composition on MPC performance is not yet clear. In this study, two different FA/MPC composites with varying aluminum-silicon glass phase contents in the FA were prepared to investigate the effects of the aluminum-silicon glass phase in FA on the setting time, early hydration heat, mechanical strength, hydration products, water resistance, and microstructure of MPC. The study results indicate that the differences in the glass phase do not significantly affect the setting of MPC. A higher aluminum-silicon glass phase content is advantageous for promoting early hydration reactions in MPC, enhancing the formation of later-stage hydration products, improving late-stage mechanical strength, and enhancing water resistance.

The thermodynamic behavior of objective compounds plays an important role in crystallization and purification. In this work, the solubility of climbazole in nine pure solvents at (288.15-318.15 K) and in a water-ethanol mixed solution at (278.15-313.15 K) was determined by a gravimetric method. It was found that the solubility is positively related to temperature and ethanol content. Three well-known thermodynamic models (modified Apelblat equation, NRTL equation, lambda h equation) were used to correlate the experimental data, and the modified Apelblat equation showed better correlation results. Meanwhile, the thermodynamic properties of climbazole in selected solvents were investigated, and it was found that the dissolution process of climbazole is spontaneous, endothermic and entropy driven. Furthermore, the solvent effect was evaluated and discussed by Kamlet and Taft linear solvation energy relationship model (KAT-LSER) and Hansen solubility parameters (HSPs). The solvent-solvent interactions and the nonspecific dipolarity/polarizability interactions have a great influence on solubility. Additionally, the molecular surface characteristics and intermolecular interactions were studied by molecular simulation to reveal the molecular mechanism behind the solubility behavior of climbazole.

Alkali-activated materials (AAMs) offer significant benefits in the field of civil engineering, thanks to their energy-efficient and environmentally-friendly properties, as well as their exceptional strength and durability. However, the fundamental chemical reaction underlying the use of AAMs has not yet been fully understood. The process of the silicate depolymerization of the supplementary gelling materials is determined by their nano characteristics, which have certain restrictions by using experimental techniques. In this study, we utilized reactive molecular dynamics (MD) simulations to elucidate the chemical events occurring during alkali-activation in different AAMs. The sodium hydroxide (NaOH) solution selectively dissolves the silicon chains, while the aluminum chains remain intact. Furthermore, the laminar structures of silicon and aluminum in metakaolin (MK) crystal are entirely disturbed. However, the disintegration of silicon chains is negligible, and the Slag minerals maintain their layered structure. Calcium ions are crucial in stabilizing the chemical process of alkali activation. Furthermore, this study evaluates the fluctuations in their activity. Gaining insight into the minute details of this reaction provides essential theoretical foundations for developing eco-friendly and high-performing alkali-activated concrete materials.

Silane coupling agents (SCAs) are utilized to enhance the impermeability of concrete surfaces, whose adhesion force is affected by the interfacial interactions in between that remain unclear. In this study, we probe the adsorption tendencies of ethyltriethoxysilane (ETES) onto C-S-H surfaces by employing density functional theory (DFT) calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations. Results suggest that significant chemisorption occurs at the CaOH(1.5), SiOH(1.0), Ca(1.0) sites C-S-H surfaces. Electronic structures analysis proved that the chemisorption of hydroxyl sites arises from the overlap of H and O atomic orbitals, resulting in the formation of hydrogen bonds. The chemisorption of the Ca(1.0) site is caused by electrostatic adsorption between calcium and oxygen. Adsorption energy results show: ECaOH(1.5) > ECa(1.0) > ESiOH(1.0). Moreover, ETES remains transverse adsorption on low Ca/Si C-S-H surfaces, while displaying longitudinal adsorption on high. Interaction analysis illustrates the configuration discrepancy arising from the absence of bridge silicon-oxygen tetrahedrons which possess vdW interactions with ethyl. Notably, transverse adsorption covers a wider area on the C-S-H surface thereby enhancing the hydrophobic effect. In summary, the utilization of ETES presents notable advantages within the context of low Ca/Si ratio cement. This study contributes valuable insights into the design and application of silane coatings.

Polycarboxylate superplasticizers (PCEs) are the most commonly used admixture in the concrete industry. Their premise for work is often considered to be the adsorption of the cement particles through the anchoring groups. Here we suggest a nanoscale perspective to understand the effects of anchoring groups on the adsorption of PCEs by employing the density functional theory (DFT) method. The electronic structural analyses consider various typically anchoring groups of (COO−, PO42−, PO32−, Silanol, and SO3−). The findings indicate that anchoring adsorption predominantly occurs at apex calcium and silicon hydroxyl (Si–OH) sites on the C–S–H surface. Specifically, PCEs containing the PO32− groups exhibit the highest degree of chemical adsorption at the apex cacium site, whereas those with COO− groups show the most pronounced chemical adsorption affinity at the Si–OH site. This observation suggests that varying calcium content in cementitious materials may necessitate the use of different anchoring groups for optimal PCE performance. Further analyses of the Reduced Density Gradient (RDG) indicate that PCE with the COO− and PO32− groups demonstrate the most robust adsorption with the corresponding site. Furthermore, quantitative examination of the peak value at the intersection of the electron localization function (ELF) curve derived an inference that aligns with the findings from the RDG analysis. This study provides a robust framework for understanding the adsorption mechanisms of PCEs with various anchoring groups and offers valuable insights for evaluating the performance of PCEs in more complex cementitious systems.

Concrete infrastructure within the salt spray zone is subject to corrosion triggered by sulfate, resulting in the deterioration of durability. Nevertheless, the atomic interface of Ca(OH)2/sulfate remains incompletely understood. In the present study, the adsorption behavior (chemical or physical) of gas sulfate was firstly determined by density functional theory approach, followed by a deep investigation on physical adsorption mechanism of Ca(OH)2/sulfate interface through classical molecular dynamics (MD) simulations, and presenting detailed conformations of sulfate hydration layer via quantum chemistry (QC) calculations. Results suggested: The chemical adsorption activity between sulfur gas and Ca(OH)2 surface is negligible, with the primary role of SO2/SO3 being to act as a donor of sulfate ions in the corrosion process. Large-scale MD simulations reveal that the diffusion of sulfate ions to the CH surface requires the formation of a complete first hydration layer. Therefore, in high-concentration droplets, the competitive effect between sulfate ions and water molecules leads to agglomeration. The conformations of the three most probable types of hydrated layers of sulfate ions at room temperature were determined using the Boltzmann distribution calculated via QC methods, and corresponding strength of hydrogen bonding within these hydrated layers was evaluated.

With the rapid pace of urbanization, global demand for concrete is increasing, shifting focus from construction to repair and maintenance. Traditional cement-based repair materials generally suffer from brittleness and poor durability, failing to meet the growing demand for durable repair solutions. We developed a water-oil gradient composite epoxy resin (CEP) modified cement-based repair mortar (MCEP) using self-synthesized water-based epoxy resin (WEP) and oil-based epoxy resin (EP). Durability tests showed that CEP-modified cement mortar exhibited improved resistance to solution penetration, shrinkage, acid corrosion, and freeze-thaw cycles, with increased CEP content positively affecting mortar durability. Notably, the addition of CEP not only enhanced the interface bonding strength between MCEP and old concrete but also maintained good bonding stability under moisture erosion. X-CT and SEM microstructural tests revealed that CEP is evenly distributed in the cement paste, forming a cement-polymer interpenetrating network structure, which improves crack resistance and reduces solution penetration in MCEP. Molecular dynamics simulations explored the adsorption of CEP on calcium aluminate hydrate (AFt), a key cement hydration product, and the moisture transport mechanisms in AFt and CEP-modified AFt nanopores. Results indicated that CEP molecules adsorb onto AFt via ionic and hydrogen bonds, demonstrating good stability. During moisture penetration, CEP reduced water transport efficiency in the nanopores. CEP modification improved the crack resistance and durability of cement repair mortars, providing valuable insights into molecular-scale enhancements in water permeability resistance. This study aims to contribute to the design and practical application of water-oil gradient epoxy resins and other polymer-modified cement-based repair materials.

The humid environment of the air conditioning system promotes the growth of microorganisms on the filter media. Using filter media with antibacterial properties can solve this problem. As a photocatalytic material, TiO2 is often added to certain products as an antimicrobial. Chitosan (CS) is an antibacterial substance that can be processed into fibers, so it can be considered as a substitute for polypropylene (PP) fiber, which is currently commonly used as a filter medium. Unlike previous studies, this study used an air duct experiment system to simulate the operating conditions of air conditioning systems, and TiO2 was supported by CS and PP fiber, respectively. Results show that TiO2/CS exhibited better filtration and antibacterial properties at a 3% TiO2 impregnation concentration. When the basic weight of CS is 190 g/m2, the filtration efficiency can reach 96.8% with only 6 W ultraviolet, but the pressure drop is only 28 Pa. At the same time, the survival of bacteria on CS filter media is about 60% lower than that on PP and bacterial shedding is decreased by more than 35%. Due to the excellent filtration and antibacterial properties of TiO2/CS composite, its use in air conditioning systems will be of interest.

Covalent organic frameworks (COFs) are a class of ordered organic network materials with permanent pore structures. The physical and chemical properties of COFs such as porosity, fluorescence, and acid-base stability can be tuned through the topological, linkage, and building block regulation. These features make COFs promising candidates in various applications and especially for detection originating from their diverse functionality. This review summarize the binding styles of COFs for ions, and their application in ions detection. Finally, the research directions for promoting COFs to become excellent sensors for ions detection are prospected.

Previous research into designing CO 2 -philic surfactants has certain limitations, necessitating the exploration of effective design concepts for hydrocarbon surfactants, which are far less expensive and less toxic than fluorocarbon surfactants.

Calcium-aluminosilicate-hydrates (C-A-S-H) is the major hydration product of sustainable concrete that incorporates industrial waste as a partial substitute for cement. Although C-A-S-H is considered a durable material, it's susceptible to sulfate attack. To better understand this phenomenon, the atomic process of sulfate attack on C-A-S-H was studied using semi-empirical quantum chemical methods. The results showed that sulfate attacks can be broken down into several subprocesses: adsorption, vibration, and breaking. The underlying causes of these processes were revealed through electronic structures, in which the weak AlO bond and strong electronegativity are the main factors leading to Al-Si breaking. The Atom in Molecular theory revealed that the weak electron localization of the [AlO4] tetrahedron leads to a lower water-assisted bond dissociated energy for breaking the AlO bond (18.3KJ/mol) than the SiO bond (109.4KJ/mol). This study provides valuable insights into the sulfate attack on C-A-S-H and its implications for improving the durability of sustainable concrete.

As one of the most important processes in the process of crystallization, nucleation determines the physicochemical properties of the crystal products. The mechanism of nucleation has not been sufficiently understood due to the complexity of the molecular assembly process. In this work, a rigid molecule of 3,5-dinitrobenzoic acid (DNBA) was selected as the model compound to investigate the connection between nucleation kinetics and solution chemistry and to investigate the mechanism of nucleation. The nucleation induction period was determined by the nonrandom method, and the parameters including interfacial energy γ and collision frequency f0C0 were calculated. FTIR, NMR, and MS were used to analyze the existing form of DNBA molecules in solutions. It was found that the solute exists in the form of monomer, multimers, and solvates in different solvents. Besides, molecular simulation and calculation were also used to investigate the intermolecular interactions of DNBA in different solvents, and the relationship between the molecular existing form and the nucleation kinetics was revealed. Finally, a possible nucleation mechanism of DNBA molecules in solution was proposed.

In recent years, micro grippers have been widely used in the micro/nanomanufacturing industry. However, during their application, the end face of the micro gripper pincer tends to adsorb impurities, making it difficult to release small objects during the gripping process, which affects their processing efficiency. To overcome these drawbacks and improve the performance of micro grippers, this study utilizes laser ablation micro/nano composite structures combined with fluorosilane chemical modification to rapidly prepare superhydrophobic surfaces with special wetting properties at the end of the micro gripper pincer, and the water contact angle (WCAs) at the pincer body reaches 156. 2 ± 2.0°, and the rolling angle (RAs) reaches 2. 2 ± 0.6°. The surface of this type of micro gripper effectively suppresses the adsorption of impurities at the gripping end and enhances the release performance of the gripper for microparticles. Additionally, this study systematically investigates the formation mechanism of the superhydrophobic surface on the pincer end of micro gripper by the analysis of three-dimensional surface topography and surface chemical composition, providing a foundation for the rapid preparation of superhydrophobic functional surfaces on gripper ends.

It is difficult to study the nucleation process of crystals intuitively due to the limitations of the current methods.

The deposition of corrosion products on the surface of the steel is a key step for understanding the generation of corrosion products. To clarify the molecular mechanism for corrosion product deposition, the reactive molecular dynamics were utilized to study the deposition process of ferric hydroxide (Fe(OH)3) on iron and passivation film substrates. It is shown that the deposition phenomenon mainly occurs on the iron surface, while the surface of the passivation film cannot adsorb Fe(OH)3. Further analysis indicates that the interaction between hydroxyl groups in γ-FeOOH and Fe(OH)3 is very weak, which is unfavorable to the deposition of Fe(OH)3. Moreover, the degree of ordered water in the two systems is affected slightly by deposition but the oxygen in water corrodes Fe(OH)3, breaking its Fe-O bonds, which is more obvious in the Fe system due to its instability. This work has revealed the nanoscale deposition process of corrosion products on the passivation film in a solution environment by reproducing the bonding and breaking of atoms at the molecular level, which is a case in point to the conclusion of the protection of steel bars by passivation film.

The solubility of 3,5-dinitrobenzoic acid in 13 solvents (methanol, ethanol, n-propanol, i-propanol, n-butanol, 2-butanol, i-butanol, n-pentanol, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, and acetonitrile) was tested by gravimetry from 283.15 to 323.15 K under atmospheric pressure. The results showed that the solubility of 3,5-dinitrobenzoic acid increased with the increasing temperature in all pure solvents. Besides, the experimental solubility results of 3,5-dinitrobenzoic acid was fitted with thermodynamic equations like modified Apelblat equation, van't Hoff equation, lambda h equation and the nonrandom two liquid equation. The results of average relative deviation, root-mean-square deviation, and coefficient of determination showed that the modified Apelblat equation correlates best of all models. Moreover, solvent effects and density functional theory (DFT) were introduced to demonstrate the dissolution properties of 3,5-dinitrobenzoic acid in the above solvents. At last, the dissolution process of 3,5-dinitrobenzoic acid in selected solvents was spontaneous according to the results of the mixing Gibbs free energy change (Delta(mix)G).