Valence Of Ions Research Articles

Flow dynamics and theoretical modeling of monolayer ionic solutions confined within Ångstrom-scale channels.

Comprehending the flow dynamics of ionic solutions within nanoconfined spaces is imperative for diverse applications encompassing desalination, nanofiltration, energy storage, and electrochemical devices. When the confinement space is further reduced to 1nm (Ångstrom scale), monolayer ionic solutions will emerge. In this regime, ions not only have the ability to influence water properties such as viscosity but also primarily modify the interactions and corresponding slip length (or friction coefficient) between the solution and wall. Notably, ion effects on water flow dynamics at Ångstrom scale exhibit unique characteristics compared to those at nanoscale and macroscale levels. In this study, we investigate the pressure-driven transport of monolayer ionic solution confined within two-dimensional graphene channels and explore the influences of ionic type, concentration, and valency on the flow rate of water via molecular dynamic simulations. Our findings reveal that divalent ions (e.g., Mg2+ and Ca2+) considerably reduce water flow rates due to enhanced viscosity and fluid-solid interface interaction compared to monovalent ions (e.g., Na+ and K+). Subsequently, we develop a theoretical model based on the Hagen-Poiseuille (HP) equation that incorporates modifications for ion-specific viscosity and slip length at the Ångstrom-scale level. By incorporating self-calculated values for water viscosity and friction coefficient/slip length at the graphene-water interface into our modified HP equation, water flow rate is basically predicted while emphasizing the critical role of ion-water interactions in Ångstrom-scale fluid transport.

Auxiliary electrodialysis realizes over 50 times concentration of nuclide ions from liquid effluents of nuclear power plants

Rapid and highly effective enrichment of nuclides containing liquid effluent is crucial for online monitoring of radioactive trace elements from nuclear power plants (NPPs). In this study, auxiliary electrodialysis (AED) was proposed for high enrichment of trace ions in the liquid effluents of NPPs. The effects of the auxiliary ion type and concentration and the operating voltage on the AED concentration performance were investigated. When the volume ratio of the solution was 140: 1 with 0.03 mol/L HNO3 as the auxiliary electrolyte, most of the nuclide ions were concentrated more than 50 times after the two-stage electrodialysis experiment. In the first-stage electrodialysis, the concentration of most ions, with the exception of the higher valence ions (Ru3+ and Zr4+), tends to increase with increasing operating voltage. The diluate stream volume could be minimized to 98.8% with a total energy consumption of 9.5 kWh/m3. By considering the impact of boron in the liquid effluents, more than 52 times concentrations could still be achieved by extending the running time of the first-stage ED (increasing the ion removal rate). The transmembrane fluxes of various cations decreased in the order of Cs+ > Sr2+ > Zn2+ > Co2+ ≈ Ni2+ ≈ Mn2+ > Fe3+ > Cr3+ > Ru3+ > Zr4+, which is attributed to the experimental operating parameters and ionic properties. This research provided a viable technique for rapid and highly effective enrichment of nuclides containing liquid effluents for both radioactive element monitoring and wastewater volume reduction.

Surface oxygen vacancy regulation strategy enhances the electrochemical catalytic activity of CoFe2O4 cathode for solid oxide fuel cells

Oxygen vacancies are crucial for enhancing oxygen ion transport in solid-state materials. Therefore, an approach was established to efficiently adjust the surface oxygen vacancy concentration in the solid oxide fuel cell (SOFC) cathodes. This method employs NaBH4 solution to capture lattice oxygen on the cathode surface, enabling precise control over both the surface oxygen vacancy concentration and the transition metal ion valence states in spinel CoFe2O4 (CFO) by modulating the NaBH4 treatment duration. The results indicate that CFO-10, treated with NaBH4 solution for 10 min, exhibits optimal electrochemical catalytic activity. This enhancement is primarily attributed to the improved oxygen adsorption-dissociation and charge transfer processes. At 750 °C, CFO-10 shows a polarization resistance (Rp) of 0.032Ω cm2, representing a reduction of 42.8 % compared to CFO. Additionally, CFO-10 achieves a peak power density (PPD) of 923 mW·cm−2, representing a 78.5 % increase compared to CFO. This study provides new insights for optimizing SOFC spinel oxide cathode performance and opens a promising avenue for the development of other high-performance catalytic materials.

Effects of Ion Valence States and Radii on the Performance of Solid-State PEDOT:PSS Electrochromic Devices.

Ion transport is a critical factor influencing the performance of electrochromic devices (ECDs). In this work, the effects of the valence state and ionic radius of six cations, Li+, Na+, K+, Mg2+, Zn2+, and Al3+, on the performance of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS)-based ECDs are investigated. Both ion migration and diffusion are discussed as processes that were analyzed, with results indicating that the primary contributor to the response of ECDs is ion migration. The response time decreases with increasing ionic valence and ionic radius, with the valence state having the predominant effect on response speed. Multivalent ions, due to strong electric field forces, migrate more rapidly and intercalate fewer ions at equivalent reaction charges, thereby facilitating a faster response. ECDs with larger-radius ions, which exhibit slower diffusion rates, also achieve faster response speeds. Among the tested ECDs with various electrolytes, the Al3+-based ECD demonstrates the fastest colored/bleached response time of 0.36/0.4 s. In addition, ions with larger radii introduce greater steric hindrance and structural damage during insertion and extraction, leading to ion retention issues and reduced cycling stability. After 500 cycles (2025 s) under a square wave voltage of ±1.5 V, the peak current of ECDs with Li+ (0.60 Å) electrolyte decreased by only 5.07/5.66%, whereas for K+ (1.33 Å) electrolyte, the decrease was 11.55/12.37%. ECDs utilizing small-radius, higher-valence ions, such as Al3+, achieved both fast response and high cycling stability, with peak current reductions of only 6.98/5.01%. Additionally, the charge storage dynamics were examined by analyzing the contributions from surface-controlled and diffusion-controlled charges, further confirming that ion migration dominates in ECDs. The high contribution of surface-controlled charges (80%) supports the fast response of ECDs and contributes to the high coloration efficiency (592.6 cm2/C for Al3+-based devices).

Effect of background ions and physicochemical factors on the cotransport of microplastics with Cu2+ in saturated porous media

Microplastics (MPs) in subsurface environments are migratory and can carry heavy metals, increasing the extent of MP and heavy metal pollution. This study used quartz sand-filled column experiments to investigate the adsorption and cotransport behaviours of PS-MPs, O3, UV-aged PS-MPs, and Cu2+ at different MP concentrations, ionic strengths, and ionic valences in a saturated porous medium. The results showed that when MPs migrate alone in the absence of an ionic background, higher concentrations have increased mobility. In contrast, an increase in the background ion concentration or ion valence inhibits the individual transport capacity of PS-MPs. An increase in the concentration of background ions or elevation in the valence state promotes Cu2+ transport because of the action of the double electric layer on the surface of the colloid and the electrostatic repulsive forces combined with the background ions. The adsorption capacity of aged PS-MPs was stronger than that of PS-MPs because of the binding of the aged PS-MPs to Cu2+ through complexation and electrostatic attraction. In the binary system of PS-MPs/Cu2+, PS-MPs promoted Cu2+ transport and the mobility of Cu2+ loaded by PS-MPs decreased with increasing background ion concentration. The cotransport results showed that MPs promote Cu2+ transport in the following order: O3-aged Ps > UV-aged Ps > Ps, as the increasing cation concentration in the MPs and Cu2+ occupies the PS surface adsorption sites. Overall, PS is an effective carrier for Cu2+. These findings offer fresh exploration concepts for the joint migration of MPs and heavy metals in underground settings.

Tailoring breakdown strength and energy-storage performance of silicon-integrated lead-free epitaxial BZT thin films through multi-element B-site substitutions

Developing high-temperature dielectric thin films with high-performance energy-storage properties for harsh environment applications has received increased attention. Herein, a multi-element co-doping strategy is proposed to enhance the breakdown strength and energy storage properties of lead-free BaTiO3-based thin films, which were deposited on silicon substrates using pulsed laser deposition. Due to the difference in ionic radii and valence states between the multi-dopants and host Ti-cations, the local lattice distortion and local charged defects are induced, which results in the reduction in the size of polar nanoregions (PNRs) and weakened coupling interactions between these PNRs, thus achieving stronger breakdown strength (EBD). Accordingly, owing to an enhanced EBD of 7.8 MV/cm and a delayed polarization saturation, a superior recoverable energy-storage density (Ur) of 140.8 J/cm3 along with an excellent energy efficiency (η) of 93.2 % were achieved at room temperature in the multi-element doped Ba(Zr0.2Ti0.2Mn0.2Nb0.2Sm0.2)O3 (BZTMNS) thin film. Moreover, the BZTMNS thin film also exhibits an excellent Ur of 102.6 J/cm3, a good η of 86.4 %, and a high EBD of 6.6 MV/cm at an operating temperature of 200 °C. Additionally, a small fluctuation of Ur (-6.1 %) and η (-11.7 %) values can also be observed in BZTMNS thin film in high cycling endurance, up to 1010 cycles, even when operated at an elevated temperature of 200 °C. These findings in the BZTMNS thin film demonstrate a feasible way to design high-temperature capacitors for modern electronic devices for hybrid vehicles and underground oil/gas explorations.

Oxygen Vacancy Sites Enable Efficient Photocatalytic Oxidation of Nitric Oxide: The Role of W/Mo Valence Transition in Bi2W(Mo)O6‐x

AbstractOxygen vacancy (Ov) sites play a critical role in the activation and deep oxidation of nitric oxide (NO). However, controlling the concentration and type of Ov remains a significant challenge. In this study, Bi2W(Mo)O6‐x is investigated as a model system and demonstrates that increasing the concentration of Ov substantially enhances the efficiency of air NO removal. Increasing the Ov concentrations in Bi2WO6‐x and Bi2MoO6‐x improves NO removal efficiency ≈12‐ and 11‐fold, respectively, compared to their low‐Ov counterparts. This enhancement is attributed to improved adsorption and activation of NO/O2 molecules, better separation and transfer of photogenerated carriers, and increased visible light absorption. Notably, Bi2WO6‐x remains highly stable over ten recycling tests for continuous air NO deep photooxidation, while Bi2MoO6‐x shows a 43.5% decrease in efficiency after ten runs. This sustained performance is attributed to stable Ovs without changes in metal ion valence, unlike Bi2MoO6‐x, where instability arises from the reduction of Mo6+ to Mo4+. In situ DRIFTS reveals possible pathways for the deep photooxidation of NO to nitrate (NO3−). This study provides valuable insights into designing high‐performance, durable catalysts by effectively controlling Ov concentration and type, paving the way for efficient photocatalytic air purification technologies.

Exploration of electrical conduction mechanisms via modulating sintering period of La0.67Ca0.33MnO3 films in various phase regions

Perovskite manganese oxide films have garnered significant attention due to their unique and diverse physical properties. In this work, La0.67Ca0.33MnO3 (LCMO) films are prepared on LaAlO3 (00l) substrates using the sol−gel spin coating method with varying sintering period (Ps). By optimizing Ps, improvements were observed in the films’ structure, morphology, ionic valence, and temperature−dependent resistivity. The reduction in Mn−O bond length and the increase in Mn−O−Mn bond angle change the degree of MnO6 distortion, resulting in an increased eg bandwidth. As Ps increased, the LCMO films exhibited better crystalline quality. The improved Mn4+/Mn3+ ratio strengthened the double exchange effect, facilitating the carrier hopping of the eg electrons. Analyses of various electrical conduction mechanisms showed that optimized electron scattering behavior, reduced hopping distance, energy and theoretical Curie temperature collectively enhance the temperature coefficient of resistivity (TCR) of LCMO films under optimal Ps. The TCR of the LCMO films reached a maximum value (31.64 % K−1) at Ps = 18 min. These findings offer valuable insights into the main electrical conduction mechanisms in both metallic and semiconducting phases, providing a deeper understanding of the underlying physical processes and offering experimental guidance for optimizing the electrical transport properties of perovskite films.

The role of multivalent cations in determining the cross-linking affinity of alginate hydrogels: A combined experimental and modeling study

This study explores the development of a comprehensive mathematical model to predict the cross-link density of alginate hydrogels using varying concentrations of divalent and trivalent ions. By systematically investigating the effects of Ca²⁺, Ba²⁺, Cu²⁺, Sr²⁺, Mg²⁺, Fe3⁺ and Al³⁺, the research describes the relationship between ion concentration and cross-link density. Experimental data reveals that the type and concentration of these ions critically influence the mechanical properties of the resulting hydrogels, with trivalent ions such as Fe³⁺ forming stronger, triple cross-links that significantly enhance the hydrogel's mechanical strength. Among the divalent ions, the trend in binding affinity is as follows: Ba²⁺ with the highest affinity followed by Sr²⁺, Ca²⁺ and Cu²⁺, while Mg²⁺ stands out with the lowest affinity, significantly differing from the others. The deviation of Cu²⁺ (transition metal ion) from the expected trend in ion interactions suggests that coordination chemistry, along with ionic radius, valence, and cation coordination abilities, plays a significant role in determining interaction strength with alginate. The proposed model, enhanced with fitting parameters k1 and k2 to account for ion-specific effects, leverages the unique binding affinities and coordination chemistry of each ion to tailor alginate hydrogels for specific applications. The parameter k1 reflects the affinity of the ions for the alginate chains, while k2 captures the coordination abilities and cross-linking efficiency. This work not only advances the understanding of ion-mediated cross-linking in alginate systems but also offers a valuable tool for the design and optimization of hydrogels with precise mechanical properties governed by various applications.

Microstructural Evaluation and Linkage to the Engineering Properties of Metal-Ion-Contaminated Clay.

The rapid progress of urbanization and industrialization has led to the accumulation of large amounts of metal ions in the environment. These metal ions are adsorbed onto the negatively charged surfaces of clay particles, altering the total surface charge, double-layer thickness, and chemical bonds between the particles, which in turn affects the interactions between them. This causes changes in the microstructure, such as particle rearrangement and pore morphology adjustments, ultimately altering the mechanical behavior of the soil and reducing its stability. This study explores the effects of four common metal ions, including monovalent alkali metal ions (Na+, K+) and divalent heavy metal ions (Pb2+, Zn2+), with a focus on how ion valence and concentration impact the soil's microstructure and mechanical properties. Microstructural tests show that metal ion incorporation reduces particle size, increases clay content, and transforms the structure from layered to honeycomb-like. Small pores decrease while large pores dominate, reducing the specific surface area and pore volume, while the average pore size increases. Although cation exchange capacity decreases, cation adsorption density per unit surface area increases. Monovalent ions primarily disperse the soil structure, while divalent ions induce coagulation. Macro-mechanical tests reveal that metal ion contamination reduces porosity under loading, with compressibility rises as the ion concentration increases. Soils contaminated with alkali metal ions shows higher compression coefficients at all loads, while heavy metal ions cause higher compression under lower loads. Shear strength, the internal friction angle, and cohesion in metal-ion-contaminated clay decrease compared to uncontaminated field-state clay, with greater declines at higher ion concentrations. The Micropore Morphology Index and hydro-pore structural parameter effectively characterize both micro- and macrostructural properties, establishing a quantitative relationship between HPSP and the engineering properties of metal-ion-contaminated clay.

Superactivity of Bimetallic CuFeO2 Submicron Particles towards Selective Proteolysis, Depending on their Surface Hydroxyls.

Nano bimetallic oxides as nanoproteases have the great advantages in the heterogeneous hydrolysis of proteins. Here, we report that bimetallic delafossite CuFeO2 submicron particles (CuFeO2 SMPs) display a high protease activity towards selective cleavage of peptide bond involving hydrophobic residue at 25 °C. CuFeO2 SMPs have excellent regeneration performance with high structural stability. The strong Lewis acidity of Fe3+ and the strong nucleophilicity of Cu+ bound hydroxyl groups are both necessary for the high protease activity of CuFeO2 SMPs. Low-valent metal ion has a great advantage in that low-valent Cu+ bound hydroxyl has strong nucleophilicity, resulting in promotion of protein hydrolysis via high-efficient bimetallic catalysis. This study provides evidence that the protease activity of CuFeO2 SMPs depends on metal ion-bound hydroxyls on their surface. Our findings highlight that the valence of metal ions in artificial protease and their surface hydroxyls are two important factors that determine their catalytic efficiency.

Preferential Binding of Cations Modulates Electrostatically Driven Protein Aggregation and Disaggregation.

Protein aggregation resulting in either ordered amyloids or amorphous aggregates is not only restricted to deadly human diseases but also associated with biotechnological challenges encountered in the therapeutic and food industries. Elucidating the key structural determinants of protein aggregation is important to devise targeted inhibitory strategies, but it still remains a formidable task owing to the underlying hierarchy, stochasticity, and complexity associated with the self-assembly processes. Additionally, alterations in solution pH, salt types, and ionic strength modulate various noncovalent interactions, thus affecting the protein aggregation propensity and the aggregation kinetics. However, the molecular origin and a detailed understanding of the effects of weakly and strongly hydrated salts on protein aggregation and their plausible roles in the dissolution of aggregates remain elusive. In this study, using fluorescence and circular dichroism spectroscopy in combination with electron microscopy and light scattering techniques, we show that the ionic size, valency, and extent of hydration of cations play a crucial role in regulating the protein aggregation and disaggregation processes, which may elicit unique methods for governing the balance between protein self-assembly and disassembly.

Ta doping effect on microstructure and microwave dielectric properties of CoNb2O6‐based ceramics and mechanism study

AbstractAs communication technology continues to evolve, 5G technology is becoming more mature, and 6G technology is steadily advancing. Microwave equipment is moving toward high frequency, miniaturization, low loss and high temperature stability, and microwave dielectric ceramics have been deeply applied in this field. To elevate the Q × f value of CoNb2O6 system, Ta5+ was introduced into CoNb2O6, and CoNb2‐xTaxO6 (0.0 ≤ x ≤ 0.8) ceramics were prepared by the traditional solid‐phase method. By X‐ray diffraction, it was observed that at x = 0.8, in addition to a single niobium ferrite phase, information of tantalate phase also appeared. Raman spectral detection and group theory analysis indicate that Ag(2) and Ag(3) modes are the dominant Raman vibrations at ≈873 cm−1. Furthermore, the polarization rate affects the εr value, and the bond energy of Nb/Ta‐O and the recovery force characterized by the average deformation of the [Nb/TaO6] octahedron are the key elements influencing the temperature coefficient of the resonance frequency (τf). The internal strain, ordered induced size, and chemical bonding valence of ionic valence states are the key factors that can increase the Q × f value. Moreover, the introduction of ions with lower electronegativity leads to an enhanced electronic compensation of oxygen vacancies, which also reduces the dielectric loss. This paper enriches the theory related to low dielectric loss and shows that CoNb1.8Ta0.2O6 (εr = 21.4832, Q × f = 100723 GHz, τf = ‐61.38 ppm/°C) ceramics with superior microwave dielectric properties are expected to be used in wireless communication devices.

Enhanced activation of sulfite by CoFe2O4-loaded with WS2 nanosheet with smooth surface for elimination and detoxification of metronidazole

In this study, cobalt ferrite-loaded tungsten disulfide (CoFe2O4@WS2) with different loading ratios was prepared by coprecipitation as a catalyst for activating sulfite in the degradation of metronidazole (MNZ) for the first time. Characterization analysis revealed that the heterogeneous catalyst possesses favorable surface properties and catalytic stability. The CoFe2O4@WS2/Na2SO3 (2:1) system exhibited the best catalytic performance under optimal conditions, achieving an impressive MNZ degradation efficiency of up to 95 % within 20 min. Quenching experiments and electron paramagnetic resonance tests indicated that oxysulfur radicals (SO3•−, SO4•− and SO5•−),1O2, •O2− and •OH generated during Na2SO3 activation and participates in the degradation of MNZ to varying degrees, while the redox cycles of Co2+/Co3+ and Fe2+/Fe3+ on the catalyst surface facilitated electron transfer, thereby promoting radical generation. Importantly, the synergistic effect between highly active W (Ⅳ) sites and unsaturated S on the catalyst surface effectively enhanced ion valence state recycling among various metal ions, ensuring continuous decomposition of sulfite, thereby facilitating sustained generation of ROS and the degradation of MNZ, confirming that WS2 played an excellent co-catalysis role. MNZ was degraded into various intermediates through three distinct pathways before ultimately mineralizing into inorganic small molecules. Toxicity analysis results indicated that the intermediate toxicity diminished with the reaction, reducing potential risks to aquatic ecosystem. Furthermore, findings demonstrated that the catalyst has excellent anti-interference ability, recyclability and low ion leaching rate. This study provides a novel approach for the efficient degradation of multiple organic pollutants using sulfites with promising application in practical water treatment.

IMPACT OF Ca DOPING ON THE STRUCTURAL CHARACTERISTICS OF La1-XCaXFe0.5Mn0.5O3

A series of perovskite compounds La1-xCaxFe0.5Mn0.5O3 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9) were synthesized using the conventional ceramic method. The influence of the Ca-doping on the crystal structure of these compounds was studied using was investigated through X-ray diffraction (XRD) and Raman scattering spectroscopy. XRD analysis revealed that all the samples crystallize in an orthorhombic structure with the Pbnm space group. The variation in lattice parameters, bond lengths and bond angles created by the difference in valence state and ion size due to the Ca-doping leads to the distortion and tilt of octahedra in the samples.

Crystal structure and spectral tuning of Eu2+/Eu3+ co-activated Na2Ba1-xSrxCa(PO4)2 phosphors with high thermal stability

The coupling of UV LED chips with phosphors to produce white or color-tunable light is still a challenge. In this work, we propose a simple rare earth occupation site engineering method to adjust the valence of doped Eu ions. Based on the Ba2+ substituted by Sr2+, new Eu2+/Eu3+ co-activated Na2Ba1-xSrxCa(PO4)2 (NB1-xSxCP) phosphors were designed and successfully synthesized. In NB1-xSxCP, the Ba2+/Sr2+ site is occupied by Eu2+, while the Ca2+ site is occupied by Eu3+. The coupled broad blue 448 nm and sharp red 619 nm luminescence under 321 nm excitation has demonstrated the coexistence of Eu2+ and Eu3+. This double emission phenomenon is studied in terms of the fluorescence lifetime as well as lattice distortion induced by the substitution ions. With the increased substitution of Sr, the luminescence of NB1-xSxCP:0.03Eu2+/3+ can be tuned from blue to red crossing the warm-white region. When x = 0.3, the chromaticity coordinates is located at (0.3779, 0.2495). The integrated intensity of Na2Ba0.7Sr0.3Ca(PO4)2:0.03Eu2+/3+ at 150℃ remains 90.9 % of that at room temperature, while the chromaticity shift (ΔE) can be calculated as 15 ×10−3. The Eu2+/Eu3+ co-activated NB1-xSxCP is a potential candidate for single-phase color-tunable phosphors used for light-tunable applications due to the combining contributions from both Eu3+ and Eu2+ ions.

Controlled Sol-Gel Transitions of Metal-Organic Membrane-Enveloped Cellulose Nanofibrils via Metal Coordination in Aqueous Media.

We report a metal coordination-driven sol-gel transition system where cellulose nanofibrils are enveloped by a rationally designed metal-organic membrane (MOM) in an aqueous medium. Specifically, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (TOBC) is encapsulated within an MOM comprising Zn2+ and the chelator phytic acid (PA), denoted TOBCMOM. Using the DLVO theory, we elucidate how tuning the metal ion valence in TOBCMOM modulates the sol-gel transition by controlling interfibrillar attractive forces. Notably, TOBCMOM fluids exhibit relaxation times consistent with the Kohlrausch-Williams-Watts (KWW) function. Significantly, we demonstrate reversible, sustainable sol-gel transitions in TOBCMOM under stepwise mechanical strain. This facile approach enables rheological tailoring of aqueous media, promising for the development of advanced stimuli-responsive smart fluids for applications in cosmetics, food science, and pharmaceutical formulations.

Asphaltene-Silica Interactions in Salinity Water and Their Ion Dependence

Summary The adsorption of asphaltene on the pore surface not only forms a dense adsorption film but also induces a transition in sandstone wettability to more hydrophobic, which poses challenges to oil displacement, especially in unconventional reservoirs. The asphaltene adsorption exhibits a strong ion dependence, especially toward high ion concentration and high-valence cations, and the mechanism is not yet entirely understood. In this work, atomic force microscopy (AFM), coreflooding experiments, and the self-priming rate method were used to investigate the impacts of ion concentration and types in connate water on the adsorption of asphaltene. Enhanced asphaltene adsorption is observed in the presence of ions, leading to a more pronounced hydrophobic character in the cores saturated by high-salinity water. Then, we proceed with a consideration of the attraction force law between asphaltene and rock. The attraction showed an exponential decay with respect to distance and is in accordance with the hydrated ion bridge interaction. Furthermore, the attraction intensified notably in CaCl2 solution compared to that in NaCl solution and was enhanced progressively with increasing ionic concentration. Therefore, the adsorption amount of asphaltene and ultimately the wettability of the rock are affected by ion concentration and valence in formation water. Our findings hold significant implications for enhancing oil recovery in unconventional reservoirs under high-salinity conditions.

Glass ceramics with different colours from granite wastes prepared by changing crystallisation temperature: Crystallisation and properties

Granite is a popular natural decorative material, and its production generates large amounts of waste. Therefore, researchers have paid close attention to the utilization of granite waste as a resource. In this work, glass-ceramic containing the same concentration of copper oxide were prepared from granite waste using a melting technique. The effects of different crystallisation temperatures on the valence of copper ions and the crystallisation of the glass-ceramics were carefully examined. The glass-ceramics crystallised at 724 °C, 783 °C, and 904 °C contained copper oxide (CuO), diopside (CaMgSi2O6), and clinoenstatite (MgSiO3). Meanwhile, those crystallised at 987 °C and 1080 °C contained richterite ((Na, F)syn (Na(Na, Ca)Mg5Si8O22F2)) and cuprite (Cu2O). The crystallisation temperature influenced the valence state of copper ions in the glass-ceramics, as demonstrated by X-ray photoelectron spectroscopy (XPS). Not only was the Cu+ content heterogeneous among samples crystallised at the different temperatures heterogeneous, but the samples also exhibited dissimilar colours. The atomic percentage of Cu+ ions (ACu+) in the sample crystallised at 987 °C was higher than that in the other samples. The mechanical properties of the sample crystallised at 1080 °C included a bending strength of 127.14 MPa and a Vickers hardness of 8.16 GPa.

The effect of MnO2 additive on the microstructure and mechanical properties of magnesium aluminate spinel

AbstractIn this study, varying amounts of MnO2 up to 5 wt.% were added to magnesium aluminate spinel (MA) bodies using a solid‐state sintering method at 1200–1600°C. The effect of MnO2 addition on the phase composition, microstructure, distribution of elements, and ionic valence of MA was investigated via X‐ray diffraction, scanning electron microscopy, energy‐dispersive spectroscopy, and X‐ray photoelectron spectroscopy, respectively. The results showed that Mg2+ ions in MA crystals were replaced by Mn2+ ions, resulting in the formation of the (Mg1‐xMnx)Al2O4 solid solution. The distorted crystal structures promoted the sintering reactions, and the mechanical characteristics of MA were greatly improved by the solid solution strengthening process. When the additive amount of MnO2 was 5 wt.% and the sintered temperature reached at 1600°C, excess manganese ions hardly dissolved into the lattice of MA. And these ions were only distributed at the grain boundaries of MgAl2O4, forming a “barrier” that hindered the migration and diffusion of particles, thereby suppressing the sintering process and weakening the mechanical strength of MA.