Search Results (17)

Lithium fluoride (LiF) crystals are widely employed both as optical windows transparent in the ultraviolet spectral region and as efficient personal dosimeters, with their application scope recently expanding into lithium-ion technologies. Moreover, as an alkali halide crystal (AHC), LiF serves as a model system for studying and simulating radiation effects in solids. This work identifies radiation-induced defects formed in lithium fluoride upon irradiation with swift heavy ion beams (N, O, Kr, U) and intense pulsed electron beams, investigates their thermal stability, and performs computer modeling of annealing processes. The theoretical analysis of existing experimental kinetics for $F$-centers induced by electron and heavy ion irradiation reveals considerable differences in the activation energies for interstitial migration. A strong correlation between the activation energy $E_a$ and the pre-exponential factor $X$($E_a$) is observed; notably, $X$($E_a$) is no longer constant but closely matches the potential function Ea. Indeed, with increasing irradiation dose, both the migration energy $E_a$ and pre-exponential factor $X$ decrease simultaneously, leading to an effective increase in the defect diffusion rate. Full article

The alkali–dolomite reaction (ADR) describes the interaction between alkalis in concrete and dolomite which results in dedolomitization, leading to cracking and deterioration of the concrete. A large number of research has explored the chemical products associated with the ADR, mechanisms of expansion, and methods of identification, but our understanding of the occurrence and progression of the ADR chemical reaction is substantially limited. Key factors controlling the ADR chemical reaction are generally not understood. This paper investigates the migration process of alkali ions in dolomitic limestone and reaction process with dolomite crystals and alkali. Dolomitic limestone samples were selected for experimentation. The amount of Sodium (Na⁺) was measured as a means of assessing alkali ion migration. We measured the degree of dedolomitization using X-ray diffraction (XRD). Microstructure was evaluated using field emission scanning electron microscopy (FESEM). This research provides new insights into dedolomitization. The pore network provides the physical pathway for alkali ion migration. Concentration gradients drive the migration of alkali ions, and their interactions control the efficiency of alkali ion migration. Full article

Waterflooding, a key method for secondary hydrocarbon recovery, has been employed since the early 20th century. Over time, the role of water chemistry and ions in recovery has been studied extensively. Low-salinity water (LSW) injection, a common technique since the 1930s, improves oil recovery by altering the wettability of reservoir rocks and reducing residual oil saturation. Recent developments emphasize the integration of LSW with various recovery methods such as CO₂ injections, surfactants, alkali, polymers, and nanoparticles (NPs). This article offers a comprehensive perspective on how LSW injection is combined with these enhanced oil recovery (EOR) techniques, with a focus on improving oil displacement and recovery efficiency. Surfactants enhance the effectiveness of LSW by lowering interfacial tension (IFT) and improving wettability, while ASP flooding helps reduce surfactant loss and promotes in situ soap formation. Polymer injections boost oil recovery by increasing fluid viscosity and improving sweep efficiency. Nevertheless, challenges such as fine migration and unstable flow persist, requiring additional optimization. The combination of LSW with nanoparticles has shown potential in modifying wettability, adjusting viscosity, and stabilizing emulsions through careful concentration management to prevent or reduce formation damage. Finally, building on discussions around the underlying mechanisms involved in improved oil recovery and the challenges associated with each approach, this article highlights their prospects for future research and field implementation. By combining LSW with advanced EOR techniques, the oil industry can improve recovery efficiency while addressing both environmental and operational challenges. Full article

This study investigates the long-term durability and crystallization-induced degradation mechanisms of alkali-activated slag (AAS) mortars with varying water-to-binder ratios (w/b, 0.4, 0.45, 0.5) under semi-immersion in 5 wt.% sodium sulfate solution. Through 360 d of exposure, the evolution of physical–mechanical properties (mass change, open porosity, compressive/flexural strength) and ion migration patterns (SO₄²⁻, Na⁺, Ca²⁺) were analyzed to unravel the interplay between pore structure, ion transport, and crystallization-induced deterioration. Results demonstrated that higher w/b ratios exacerbated surface crystallization and spalling due to accelerated ion transport and pore coarsening. Early-stage strength gains (up to 25.15% at 120–180 d) stemmed from pore refinement via sulfate deposition and continued slag hydration. However, prolonged exposure triggered microstructural degradation, with open porosity increasing by 58.9% and strength declining by 30.6% at 360 d for a w/b of 0.5 compared to a w/b of 0.4. This was driven by crystallization pressure and the decalcification of hydration products. Ion migration analysis revealed SO₄²⁻ enrichment in evaporation area and outward Na⁺ diffusion, establishing supersaturation gradients that aligned with crystallization damage progression. These findings provide critical insights for optimizing AAS mortar formulations to mitigate sulfate crystallization risks in semi-immersed environments. Full article

Red mud (RM) is a strongly alkaline waste residue produced during alumina production, and its high alkali and fine particle characteristics are prone to cause soil, water, and air pollution. Phosphogypsum (PG), as a by-product of the wet process phosphoric acid industry, poses a significant risk of fluorine leaching and threatens the ecological environment and human health due to its high fluorine content and strong acidic properties. In this study, RM-based cemented paste backfill (RCPB) based on the synergistic curing of PG and ordinary Portland cement (OPC) was proposed, aiming to achieve a synergistic enhancement of the material’s mechanical properties and fluorine fixation efficacy by optimizing the slurry concentration (63–69%). Experimental results demonstrated that increasing slurry concentration significantly improved unconfined compressive strength (UCS). The 67% concentration group achieved a UCS of 3.60 MPa after 28 days, while the 63%, 65%, and 69% groups reached 2.50 MPa, 3.20 MPa, and 3.40 MPa, respectively. Fluoride leaching concentrations for all groups were below the Class I groundwater standard (≤1.0 mg/L), with the 67% concentration exhibiting the lowest leaching value (0.6076 mg/L). The dual immobilization mechanism of fluoride ions was revealed by XRD, TGA, and SEM-EDS characterization: (1) Ca²⁺ and F⁻ to generate CaF₂ precipitation; (2) hydration products (C-S-H gel and calixarenes) immobilized F⁻ by physical adsorption and chemical bonding, where the alkaline component of the RM (Na₂O) further promotes the formation of sodium hexafluoroaluminate (Na₃AlF₆) precipitation. The system pH stabilized at 9.0 ± 0.3 after 28 days, mitigating alkalinity risks. High slurry concentrations (67–69%) reduced material porosity by 40–60%, enhancing mechanical performance. It was confirmed that the synergistic effect of RM and PG in the RCPB system could effectively neutralize the alkaline environment and optimize the hydration environment, and, at the same time, form CaF₂ as well as complexes encapsulating and adsorbing fluoride ions, thus significantly reducing the risk of fluorine migration. The aim is to improve the mechanical properties of materials and the fluorine-fixing efficiency by optimizing the slurry concentration (63–69%). The results provide a theoretical basis for the efficient resource utilization of PG and RM and open up a new way for the development of environmentally friendly building materials. Full article

This study utilizes the temperature–pressure reactor to simulate the real conditions of the reservoir to study rock dissolution and scale formation caused by strong and weak alkali during the ASP flooding in an oilfield in China. Mercury injection experiments showed that the porosity and permeability of rock increased by 10.3% and 15.3% under the action of strong alkali, while they increased by 7.2% and 10.1% under the action of weak alkali, indicating that both strong and weak alkali can cause rock dissolution. The structural morphology of the rock demonstrated that the clay content between the grains decreased significantly. The semi-quantitative analysis of XRD indicated that the content of kaolinite decreased from the initial 7% to 0%. The recrystallized carbonate was found, and the carbonate content increased from the initial 0% to 12%. According to the SEM, EDS, and Raman analyses of the scale, the scale formation was complex in the strong alkaline system, including silicate scale, carbonate scale, and hydroxide scale. In contrast, only carbonate scale was found in the weak alkaline system. The ICP-AES test for the liquid system revealed that the rock dissolution releases substantial Ca²⁺, Mg²⁺, Fe²⁺, SiO₃²⁻ and AlO₂⁻ ions, among which Si concentration can reach around 560 ppm. The chemical mechanism of rock dissolution and scale formation by strong and weak alkali includes the exchange of mineral cations by Na⁺ and the destruction of Si-O and Al-O bonds by OH⁻. These released ions migrate with the composite fluid, then recrystallize under the saturation state to form the scale. The dissolution of rock by strong alkali is more intense, while the dissolution of weak alkali is relatively mild. Moreover, the scale type in the weak alkaline system is simpler, which would be convenient to develop inhibitors. Full article

Alkali metal-ion capacitors (AMICs) combine the advantages of the high specific energy of alkali metal-ion batteries (AMIBs) and the high power output of supercapacitors (SCs), which are considered highly promising and efficient energy storage devices. It is found that carbon has been the most widely used electrode material of AMICs due to its advantages of low cost, a large specific surface area, and excellent electrical conductivity. However, the application of carbon is limited by its low specific capacity, finite kinetic performance, and few active sites. Doping heteroatoms in carbon materials is an effective strategy to adjust their microstructures and improve their electrochemical storage performance, which effectively helps to increase the pseudo-capacitance, enhance the wettability, and increase the ionic migration rate. Moreover, an appropriate heteroatom doping strategy can purposefully guide the design of advanced AMICs. Herein, a systematic review of advanced heteroatom (N, S, P, and B)-doped carbon, which has acted as a positrode and negatrode in AMICs (M = Li, Na, and K) in recent years, has been summarized. Moreover, emphasis is placed on the mechanism of single-element doping versus two-element doping for the enhancement in the performance of carbon positrodes and negatrodes, and an introduction to the use of doped carbon in dual-carbon alkali metal-ion capacitors (DC-AMICs) is discussed. Finally, an outlook is given to solve the problems arising when using doped carbon materials in practical applications and future development directions are presented. Full article

The widespread adoption of geopolymer concretes in the industry has been slow, mainly due to concerns over their long-term performance and durability. One of the main causes of concrete structures’ deterioration is chloride-induced corrosion of the reinforcement. The reinforcement corrosion process in concrete is composed of two main stages: the initiation phase, which is the amount of time required for chloride ions to reach the reinforcement, and the propagation phase, which is the active phase of corrosion. The inherent complexities associated with the properties of precursors and type of activators, and with the multi-physics processes, in which different transfer mechanisms (moisture, chloride, oxygen, and charge transfer) are involved and interact with each other, have been a major obstacle to predicting the durability of reinforced alkali-activated concretes in chloride environments. Alternatively, the durability of alkali-activated concretes can be assessed through testing. However, the performance-based tests that are currently available, such as the rapid chloride permeability test, the migration test or the bulk diffusion test, are only focusing on the initiation phase of the corrosion process. As a result, existing testing protocols do not capture every aspect of the material performance, which could potentially lead to misleading conclusions, particularly when involving an electrical potential to reduce the testing time. In this paper, a new performance-based test is proposed for assessing the performance of alkali-activated concretes in chloride environments, accounting for both the initiation and propagation phases of the corrosion process. The test is designed to be simple and to be completed within a reasonable time without involving any electrical potential. Full article

In this study, the photoluminescence (PL) behavior of two aluminosilicate glass series containing alkali-niobates ranging from 0.4 to 20 mol% was investigated. The glasses exhibit an intense visible emission centered at ~18,400 cm⁻¹ for the peralkaline series and at higher energies (~19,300 cm⁻¹) for the metaluminous glasses. However, the photoluminescence emission intensity varies significantly with the niobate content and the bulk chemistry. PL and fluorescence lifetime measurements indicate that the broad emission bands result from the overlap of different niobate populations, whose distribution changes with niobate content. The distinct PL behavior in the two glass series was related to the structural evolution of the niobate units upon niobium addition. An enhancement of the visible emission was observed for a higher fraction of distorted [NbO₆] units. Eu-doping was carried out as a structural probe of the glass network, and also to determine if these glasses could be used as potential rare earth element (REE) activators. The crystal field strength around Eu ions is strongly dependent on the bulk chemistry and the niobate content. Furthermore, the peralkaline series showed energy transfer from the host [NbO₆] to Eu³⁺, confirming the feasibility of exploring niobate glasses and glass-ceramics as lanthanide ion-activated luminescent materials. In addition, glass-ceramics (GCs) containing alkali-niobate phases with a perovskite-like structure were developed and studied to verify the optical performance of these materials. It was verified that the bulk chemistry influences crystallization behavior, and also the photoluminescence response. The transparent GC from the metaluminous series exhibits a quenching of the Eu³⁺ emission, whereas an enhanced emission intensity is observed for the peralkaline GC. The latter shows a strong excitation-dependent PL emission, suggesting energy transfer and migration of electronic excitation from one Eu population to another. Additionally, Eu³⁺ emissions arising from the $D_1_5^{}$ and $D_2_5^{}$ excited states were observed, highlighting the low phonon energy achievable in niobo-aluminosilicate hosts. Full article

The presence of intrinsic ion migration in metal halide perovskites (MHPs) is one of the main reasons that perovskite solar cells (PSCs) are not stable under operation. In this work, we quantify the ion migration of PSCs and MHP thin films in terms of mobile ion concentration (N_o) and ionic mobility (µ) and demonstrate that N_o has a larger impact on device stability. We study the effect of small alkali metal A-site cation additives (e.g., Na⁺, K⁺, and Rb⁺) on ion migration. We show that the influence of moisture and cation additive on N_o is less significant than the choice of top electrode in PSCs. We also show that N_o in PSCs remains constant with an increase in temperature but μ increases with temperature because the activation energy is lower than that of ion formation. This work gives design principles regarding the importance of passivation and the effects of operational conditions on ion migration. Full article

Heterointerface engineering has been verified to be an effective approach to enhance the energy density of alkali-ion batteries by resolving inherent shortcomings of single materials. However, the rational construction of heterogeneous composite with abundant heterogeneous interfaces for sodium-ion batteries (SIBs) is still a significant challenge. Herein, inspired by density functional theory calculations, interface engineering can greatly decrease the energy bandgap and migration barrier of Na ions in Sb and Na₃Sb phases, as well as enhance the mechanical properties. A porous heterointerface MOFC–Sb is fabricated by utilizing MOF-C as a support and buffer, exhibiting excellent electrochemical performances for sodium storage. The MOF-C–Sb anode with its rich heterointerface presents an improved electrochemical performance of 540.5 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹, and 515.9 mAh g⁻¹ at 1.6 A g⁻¹ in term of sodium storage, efficiently resolving the serious volume expansion issues of metal Sb. These results indicate the structural superiority of heterointerface-engineered structure and afford valuable information for the rational design and construction of Sb-based anode materials for high-performance electrochemical energy storage. Full article

To achieve a cleaner production, pesticide wastewater with concentrated NaCl can be treated by using a bipolar membrane electrodialysis (BMED) and converted to NaOH and HCl, which minimizes acid and alkali consumption in a pesticide production process. However, ion-exchange membranes (IEMs) are vulnerable to fouling by phenolic substances present in the concentrated NaCl solutions. This work aimed to understand the performance and fouling mechanism of BMED from phenol during the desalination of NaCl and explore an effective cleaning method. The results firstly showed that for the NaCl solutions with higher phenol concentrations, the selectivity of the IEMs was reduced after processing six successive batches of BMED, which led to reverse migration of ions, organics leakage, and an obvious increase in the energy consumption and the concentration of generated acid and alkali. Secondly, IEMs characterization analysis detected that the structure of the IEMs was deformed, while phenol fouling deposits were observed on the surface and interior of the IEMs, especially for the anion exchange membranes (AEMs). Then, the results of soaking tests proved that the phenol could bring about swelling-like degradation to the AEMs and 0.1 wt.% NaOH solution was studied to be the optimized cleaning agent since the performance of the fouled IEMs in the short-running process could be recovered after 5 h of in situ cleaning that removed the phenol fouling deposits efficiently. Finally, the results of a long-running BMED operation treating NaCl solution containing 10 g/L phenol concentration showed that the IEMs were severely fouled, and the fouling was firstly due to the swelling-like mechanism during the initial 12 successive batches, and then should belong to the blockage-like mechanism during the following 20 successive batches. The seriously fouled IEMs could no longer be recovered even after a deep in situ cleaning. This research proves that under appropriate pretreatment or operating conditions, the BMED process is an alternative way of treating wastewater with high salinity and the presence of phenol molecules. Full article

The purpose of this study was to investigate the properties of hardened alkali-activated concrete, which is considered an eco-friendly alternative to Portland cement concrete. In this paper, the precursors for alkali-activated concrete preparations are blends of fly ash and ground-granulated blast-furnace slag in three slag proportions: 5%, 20%, and 35%, expressed as a percentage of fly ash mass. Thus, three concretes were designed and cast, denominated as AAC5, AAC20, and AAC35. Their physical and mechanical characteristics were investigated at 28 and 180 days, as well as their properties of chloride ion transport. The modified NT BUILD 492 migration test was applied to determine the chloride ions’ penetration of the alkali-activated concretes. Improvement of mechanical strength and resistance to chloride aggression was observed with ground-granulated blast-furnace slag content increase in the compositions of the tested concretes. Mercury intrusion porosimetry tests provided insight into the open pore structures of concretes. A significant decrease in the total pore volume of the concrete and a change in the nature of the pore diameter distribution due to the addition of ground granulated blast furnace slag were demonstrated. Full article

Red mud is a strong alkaline solid waste pollutant produced in the process of aluminum smelting, which causes great pollution to the regional groundwater environment due to its high content of fluorine and aluminum and high concentration of strong alkali. In this study, fluoride ion was selected as the model contaminant, and a numerical model of the groundwater flow field and solute transport was developed using GMS software to simulate and analyze the migration patterns of fluoride contaminants caused by the red mud pit for the fractured karst geohydrological conditions. The results demonstrated that the groundwater model and flow pattern were mainly controlled by atmospheric precipitation recharge, given flow boundary conditions and leakage of rivers and drains. When the concentration of fluorine pollutants in the red mud yard was 60.0 mg/L, the maximum migration distance of F⁻ in the groundwater of the ordovician limestone aquifer was 473, 1160, 1595 and 1750 m after 1, 5, 10 and 15 years of bottom leakage, and the additional transport distances were 687, 435 and 155 m every 5 years, respectively. The range of F⁻ pollution plume was 0.37 km², 1.15 km², 1.95 km² and 2.14 km², respectively and the range of newly added pollution plume was 0.78 km², 0.80 km² and 0.19 km², respectively, every five years. Both indicated that with the extension of time, the migration and diffusion rate of pollutants slow down, and the diffusion volume increased first and then decreased. The F⁻ pollution plume spread from the red mud pit to the northeast, which was consistent with the flow of groundwater. The high-concentration pollution plume was mainly distributed in the Ordovician limestone fractured aquifer in the northeast. This study revealed the migration law of red mud pollutants, and provided a scientific decision-making basis for the prevention and control of red mud groundwater pollution in the future. Full article

The alkali metal pyroxenes of the AVSi₂O₆ (A = Li and Na) family have attracted considerable interest as cathode materials for the application in Li and Na batteries. Computer modelling was carried out to determine the dominant intrinsic defects, Li and Na ion diffusion pathways and promising dopants for experimental verification. The results show that the lowest energy intrinsic defect is the V–Si anti-site in both LiVSi₂O₆ and NaVSi₂O₆. Li or Na ion migration is slow, with activation energies of 3.31 eV and 3.95 eV, respectively, indicating the necessity of tailoring these materials before application. Here, we suggest that Al on the Si site can increase the amount of Li and Na in LiVSi₂O₆ and NaVSi₂O₆, respectively. This strategy can also be applied to create oxygen vacancies in both materials. The most favourable isovalent dopants on the V and Si sites are Ga and Ge, respectively. Full article