Hydration Of Oxide Research Articles

A new strategy to design the purification process of ethyl tertiary butyl ether gasoline additive via hybrid extractive-reactive distillation

Here we propose a new strategy for designing the purification process of ethyl tertiary butyl ether (ETBE) gasoline additive. Our proposal suggests replacing the last two columns of the triple-column extractive distillation process from previous work with a single reactive distillation column. This column incorporates an ethylene oxide hydration reaction, yielding ethylene glycol, which can be utilized as a solvent for extractive distillation. This replacement is able to reduce the total number of columns, the amount of solvent needed, and significantly decreases total energy consumption up to 32% compared to the original process. Furthermore, it benefits from the redistribution of energy between different steam-grade utilities, enabling significant reduction in operational costs. These advantages result in a 3−22% cost decrease compared to the original process. Overall, the proposed process exhibits significant improvements in energy efficiency and cost reduction with respect to the original process with and without heat integration from previous research.

A dual mechanism drives the enrichment of pedogenic magnetic particles derived from red beds

Iron oxides and associated magnetic properties are considered good indicators of the pedogenic environment and regional climate. However, these indicators are under debate for soils developed from sediments. The accumulation of magnetic particles derived from sediments depends not only on the formation of iron oxides but also on the existence and transformation of detrital iron oxides. To explore the formation mechanism of magnetic particles accompanied by pedogenetic processes, a toposequence consisting of six profiles derived from red beds with contrasting drainage conditions under a subtropical monsoon climate is examined. We generally observed upward magnetic enhancement but inconsistent correlations between magnetism and iron oxide phases. The magnetic enhancement in the well drained profiles was dominated by the reverse transformation of detrital hematite to fine maghemite particles, whereas in the poorly drained profiles, coarse magnetite particles formed with soil organic matter enrichment in an anaerobic way. The lower magnetism in the transition profiles is attributed to the hydration of iron oxides into goethite before the pedogenic environment became anaerobic. The different magnetic enrichment mechanisms explain the nonlinear responses of magnetism and color to climate across temporal and spatial scales. These findings also suggest that soil magnetism is promising for tracing soil moisture and ecological evolution, especially in red soils and sediments across the surfaces of the Earth.

Modeling hydration of graphene oxide (GO) – Does size matter?

The biomedical applications of graphene-based materials become one of hot scientific and technological topics in the last few years. Flake graphene oxide (GO) is considered as one of the promising materials for biomedical use due to a number of specific properties, in particular in design of advanced drug delivery systems (DDS). The key factor in the formation of non-covalently bonded complexes for drug transport is the strength of non-covalent interactions of the carrier with both the drug and the environment. In the current work, we have focused on molecular modeling of solvation of zigzag-edged graphene oxide, functionalized with hydroxyl and carboxyl substituents. The hydration was determined from the magnitude of weak intermolecular interactions of GO with one or two water molecules. Our goal was to establish the dependence of the degree and type of functionalization, as well as the size of graphene flakes and the position of hydrophilic substituents on the number and strength of H-bonds. All calculations were performed using density functional theory (DFT) at the B3LYPD3BJ/6-311++G** level. The effect of water solvent was established using an explicit (discrete) model of solvent.

Chelating agent stimulated LDH post-treatment of PEO coated AA2024

Layered double hydroxides (LDHs) are well known and broadly investigated on bare aluminum alloys, but not on PEO treated aluminum where source of aluminum ions is restricted. The additions of the chelating agents were tested in this work to stimulate the LDH formation on PEO (plasma electrolytic oxidation) coated aluminum alloy AA2024. 1,3-diamino-2-hydroxipropane-N,N,N’,N’-tetraacetic acid (DHPTA) was identified as the most effective one among tested additives. Its performance in terms of LDH growth stimulation was investigated. The DHPTA additive provides an increase of the pH of the LDH synthesis compared to previously known methods to achieve hydration of aluminum oxide from PEO as the initial stage of PEO etching, as well as the formation of soluble complex compounds of Zn-DHPTA, necessary for the formation of ZnAl LDH. The process of LDH formation was also followed by intercalation of DHPTA ions into LDH galleries. It was shown that LDH was formed both on the surface and insight the pores of parental PEO coating. Moreover, it imparted lubricating properties to the hybrid coating. Finally, PEO-LDH coating demonstrated higher corrosion resistance and long-term stability comparing to the PEO coated aluminum alloy.

On the origin of enhanced electrochemical kinetics in guest-ions pre-intercalated layered vanadium oxides: Interlayer spacing vs lattice distortion

Cathode materials of highly stable structure and high capacity are essentially required for aqueous rechargeable zinc ion batteries (ARZIBs), where layered vanadium oxide hydration (VOH) is one of the most promising cathode materials for reversible zinc ion intercalation/deintercalation. Previous studies have shown that both the interlayer spacing and the Zn-ion storage performance can be altered by the pre-intercalation of certain guest ions between the layers of VOH. In addition to previous discussions on the increase in effective Zn2+ storage as a result of the widening in interlayer spacing after guest ion pre-intercalation, there is a variation in the exposed active O sites, which are shown to be equally important. In the metal ion pre-intercalated layered vanadium oxides, there is a delicate balance between the interlayer spacing and lattice distortion, depending on the type and amount of pre-intercalated metal ions. In particular, those pre-intercalated guest ions with high electronegativity can steadily shift towards the VO layers and break the V-O bonds leading to exposed active O sites. The high electronegativity endows the combination of guest ions with newly exposed O sites. These active O sites give rise to an inhomogeneous distribution of the charge density, leading to an improvement in electrochemical performance. The present study demonstrates the complicated interplays of more than one parameter in the guest ion pre-intercalated layered vanadium oxides, going much beyond the simple widening in inter-layer spacing.

A more appropriate way to optimize the hybrid reactive-extractive distillation system

Existing studies on reactive-extractive distillation (RED) commonly misapply optimization variables by including reaction stages. Given the uncatalyzed nature of ethylene oxide (EO) hydration in RED, where it naturally occurs throughout the column, a more appropriate strategy is to optimize only the total stages, allowing the reactive stage to align accordingly. However, previous attempts to implement this approach faced challenges. Here we introduce an algorithm addressing the variable overlap issue in optimizing RED, exemplified in two case studies. In Case 1, we explored a distinct scenario where the original process designated a specific reaction zone. Adjustments were made to ensure the reaction occurred throughout the entire column but it leads to a 13 % total annual cost (TAC) increase compared to the base case. In Case 2, optimization was applied to a system where reaction were distributed throughout the column without prior optimization, yielding a marginal 3.87 % reduction in the TAC.

Fluoride leaching from tuff breccia and its removal by natural and commercial adsorbents

In Japan, the concentration of fluoride (F−) leached from rocks, such as tuff breccia, excavated in tunnel construction projects often exceeds the Japanese environmental standard of 0.8 mg/L. Because of this, proper disposal methods are necessary for managing F−-bearing excavated rocks. One effective solution based on circular economy is the use of an adsorption layer system. This system can simultaneously prevent the migration of F− released from excavated rocks and allow the recycling of this construction waste material. To determine the most suitable material for the disposal of excavated F−-bearing tuff breccia from a tunnel construction in Hokkaido, Japan, four types of natural geological materials (S-1, S-2, S-3, and S-4) obtained near the tunnel construction site, as well as three types of commercial adsorbents (calcium (Ca), magnesium (Mg), and CaMg adsorbents) were selected for evaluation. The batch adsorption test results showed that S-1 and S-4 had high adsorption capacities for F−, and the adsorption process followed the Langmuir isotherm. The adsorption of F− to the natural adsorbents was strongly influenced by the pH and the presence of bicarbonate ions (HCO3−), but unaffected by chloride (Cl−) and sulfate (SO42−). There was also a strong positive correlation between the abundance of amorphous aluminum (Al) and iron (Fe) extracted and the adsorption of F−, indicating the importance of ion exchange reactions associated with surface OH− in immobilizing F−. Meanwhile, the Mg-bearing adsorbent exhibited the highest adsorption affinity for F− among the commercial adsorbents. This was attributed to adsorption through electrostatic interactions and coprecipitation with magnesium hydroxide (Mg(OH)2) formed during the hydration of magnesium oxide (MgO). To effectively incorporate these adsorbents into the adsorption layer system, parameters such as permeability and residence time need to be determined in order to maximize the retention of F− through adsorption, ion exchange and coprecipitation reactions.

CO2-assisted hydration of propylene oxide to produce propylene glycol: Accessing high selectivity using a jet loop reactor

The synthesis of glycols from the CO2-assisted hydration of epoxides is highly significant in terms of both CO2 utilization and the production of fine chemicals. Significant effort has been devoted to designing effective catalysts. However, the gas–liquid mass transfer of this process, which is critical for the efficiency of the transformation, has received less attention. In this study, propylene glycol (PG) was synthesized with high efficiency through the CO2-assisted hydration of propylene oxide (PO) using a jet loop reactor (JLR). A systemic investigation of the influence of the reaction conditions was carried out with respect to reaction temperature, CO2 pressure, and catalyst concentration. Under optimal reaction conditions, the CO2-assisted hydration of PO proceeded efficiently with a low H2O:PO molar ratio of 1:1, producing PG with a high selectivity of 99% and full conversion of PO. Notably, the JLR exhibited higher efficiency and product selectivity than a stirred-tank reactor, demonstrating its superior advantage in facilitating gas–liquid mass transfer.

Structure of polyethylene glycol/water mixtures as a separation medium of aqueous two-phase extraction systems studied by equilibrium analysis of thiocyanato complexation of Cobalt(II)

Aqueous two-phase systems (ATPS) utilizing polyethylene glycol (PEG) have been successfully used for the separation of various organic and inorganic compounds as an environmentally benign extraction method. However, a fundamental understanding of the role of the hydration structures around PEG chains in solute partitioning in ATPS remains elusive although it has been considered that PEG molecules are involved in separation. In the present work, the equilibria of Co(II) thiocyanate complexation reaction in aqueous PEG solutions were studied by spectrophotometry with varying ethylene oxide chain length and concentration of PEG. From the formation constants of the tetrahedral and octahedral Co(II) thiocyanate complexes obtained, a microheterogeneous structure consisting of pseudo phases formed by hydration of ethylene oxide (EO) chain and terminal hydroxyl (OH) groups in the PEG molecule in addition to the bulk water phase was estimated. It was revealed that the formation of tetrahedral Co(NCS)42− complex proceeds in the EO pseudo phase by the involvement of hydrophobic ethylene groups, while the OH phase and the bulk phase inhibit the progress of the reaction. This indicates that Co(NCS)42− is stable in hydrophobic hydration structure of water around the EO moiety. The EO phase imparts hydrophobicity to aqueous PEG solutions and plays a predominant role in partition of solute molecules in PEG-based ATPS.

Pathway modulation and substrate partitioning for CO2-assisted hydration of ethylene oxide catalyzed by swelling poly(ionic liquid)s

Amine-functionalized swellable poly(ionic liquid)s (poly[BAVIm]Br-DVIm-n%) were synthesized by free radical copolymerization of amine-functional vinyl imidazolium ionic liquids and ionic cross-linker 1,8-triethylene glycoldiyl-3,3́-divinylimidazolium (DVIm). Poly[BAVIm]Br-DVIm-n% exhibited excellent swelling ability in the water, ethylene carbonate (EC), and ethylene glycol (MEG), and the swelling ratio (Q) decreased with the increase of the content of the crosslinker. The swollen state of poly[BAVIm]Br-DVIm-2.5% in water observed by cryogenic scanning electron microscopy (cryo-SEM) presented densely packed and interconnected pores (0.2–11 μm). Poly[BAVIm]Br-DVIm-n% were used to catalyze CO2-assisted hydration of ethylene oxide (EO) at a low H2O/EO ratio of 1:1, in which poly[BAVIm]Br-DVIm-2.5% with the highest Q in water gave the highest yield (87%) and selectivity (97%) of MEG. Moreover, EC was produced and subsequently disappeared during the process of CO2-assisted hydration of EO. A cascade reaction including the cycloaddition of CO2 with EO (EO + CO2 → EC) and the hydrolysis of the resulting EC (EC + H2O → MEG + CO2) in situ was elaborated. Poly[BAVIm]Br-DVIm-n% containing amine group and imidazolium ionic liquid synergistically catalyzed this cascade reaction, exhibiting a bifunctional effect. Poly[BAVIm]Br-DVIm-2.5% with the H2O, EC, and MEG enrichment ability in H2O/EO, EC/EO, and MEG/EO could spatially isolate EO and H2O, EC, MEG. The substrate partitioning of poly[BAVIm]Br-DVIm-2.5% could promote the two sequential reactions to be orthogonal and inhibit the side-reactions between MEG and EO, thus resulting in a higher reaction rate of poly[BAVIm]Br-DVIm-2.5% (0.0141 h−1) than that of homogeneous catalyst ([BAVIm]Br) (0.0074 h−1). Furthermore, poly[BAVIm]Br-DVIm-n% had good generality and could be reused effectively at least seven times without a significant decrease of its initial activity.

Impact of recovered silicon particles incorporation on tribo-characteristics of a poly ether ether ketone polymer composite

The tribological behaviour of polyether ether ketone (PEEK) polymer filled with various concentrations of recovered silicon particles (0, 1, 3, 5, and 10 wt%) fabricated by the hot press technique was investigated in this research work. The hardness and wear properties of the prepared composite materials were evaluated through the Shore D hardness and the pin-on-disc methods. The Shore D hardness of the PEEK composite containing 10% silicon was about 95. This was due to the silicon's better dispersion influencing hardness enhancement. The current study found that adding 10% recycled silicon to PEEK decreased the rate of wear to 0.77*10−6 mm3/Nm and the coefficient of friction (COF) to 0.06. PEEK composites are filled with 10% silicon particles. Silicon particles were responsible for elevating wear resistance and anti-friction behaviour compared to pure virgin PEEK. The wear-behaviour of the PEEK/Silicon composite was greatly influenced by the formation of a transfer film, which avoids direct contact between countersurface steel asperities and the composite. The lubricity effect was obtained by incorporating silicon particles in the PEEK matrix as sliding surfaces with a steel counter surface that tend to form iron oxide and passive hydration mixed transfer films, decreasing COF and wear considerably. The tribofilm firmly adheres to the counter disc through the mechanical interlocking of silicon particles, enabling higher tribofilm bond strength.

Microstructure and micromechanical properties of magnesium phosphate cement

This paper presents a systematic study on the evolution of phase composition, microstructure and micromechanical properties of magnesium phosphate cement (MPC) and their relations to macroscopic mechanical properties. The results indicate that the microstructure of MPC is mainly composed of a crystal region of potassium magnesium phosphate hexahydrate (MKP) and a hybrid region of magnesium oxide and amorphous hydration products. The elastic modulus and hardness of MKP crystals are 20.18 GPa and 1.15 GPa, respectively. Amorphous hydration products may consist of MgKPO4 and Mg3 (PO4)2. The elastic modulus of amorphous MgKPO4 drops gradually from 51.4 GPa to 29.2 GPa with increasing curing age towards the elastic modulus of crystalline MKP, while the elastic moduli of amorphous Mg3(PO4)2 and unreacted MgO are approximately 160 GPa and 300 GPa, respectively. The macroscopic strength of MPC is mainly dependent on its pore structure rather than the micromechanical properties of hydration products.

Corrosion behavior of magnesium in aqueous sulfate-containing electrolytes

Studies have been conducted on the corrosive behavior of magnesium in aqueous sulfate electrolytes (0.5 mol/L MgSO4; 0.5 mol/L Na2SO4; 0.5 mol/L MgSO4 + 0.5 mol/L Na2SO4).The composition structure and morphology of the surface of the samples were studied using scanning electron microscopy in combination with X-ray spectral microanalysis. The results of the experiments showed the formation of a surface film inhomogeneous in its structure and composition with the main components Mg(OH)2 and MgO. An increase in the exposure time of the electrode in solution led to the formation of microcracks on the main film caused by internal stress because of hydration of magnesium oxide produced during corrosion. The salt composition of the electrolyte determines the morphology and thickness of corrosion films due to differences in the solubility of the products formed during the hydrolysis of magnesium oxide and the kinetics of this process.Applying the methods of scanning electron microscopy X-ray electron analysis gravimetry and voltammetry it has been established that at various stages of magnesium corrosion in different electrolytes the growth rates of corrosion films are determined by the kinetics of magnesium oxide formation its hydration and dissolution followed by crystallization in the form of a brucite phase of loose sediments on the surface.

Construction and technical properties of vermiculite concrete and fibro vermiculite concrete with volcanic pumice under the influence of elevated temperatures

Objective. Development of compositions of vermiculite concrete and fibro vermiculite concrete with volcanic pumice. Investigation of the construction and technical properties of the developed compositions of vermiculite concrete and fibrovermiculite concrete with volcanic pumice under the influence of elevated temperatures.Method. Methods of increasing the fire resistance of reinforced concrete structures are considered. The research is aimed at the development of vermiculite concrete and fibro vermiculite concrete with volcanic pumice for fire protection of building structures and the manufacture of heat-resistant products and structures. To reduce the cost of vermiculite concrete, its partial replacement with volcanic pumice is proposed. For the study of vermiculite concrete with volcanic pumice reinforced with basalt fiber, a rotatable plan of the second order of the regular hexagon type was used.Result. Replacing a part of an expensive aggregate (expanded vermiculite) with pumice leads to a slight increase in the average density of the composite, while the bending and compressive strength increases. In addition, the heat-resistant properties of vermiculite concrete with pumice are increased. This is due to the fact that volcanic pumice, being a hydraulically active additive, is able to react hydration with cement components, eliminating the harmful effect of secondary hydration of free calcium oxide. The influence of the heating temperature on the change in the construction and technical properties of vermiculite concrete and fibrovermiculic concrete, including with the addition of pumice, has been studied. It was found that dispersed reinforcement with basalt fibers reduces shrinkage deformations, when heated to t = 800, the shrinkage decreases from 0.7 to 0.5% compared to the original concrete matrix.Conclusion. The dependence "compressive strength = f (average concrete density)" significantly depends on the presence and ratio of pumice in the composition of vermiculite concrete, while an increase in the holding temperature to 600 oC or 800 oC leads to a decrease in the compressive strength from 15 to 25%, and the main decrease occurs when heated to 600 oC, further the increase in temperature has a negligible effect. The dependence of the bending strength on the compressive strength is generally maintained regardless of the heating temperature, and the heating of concrete does not reduce the relative bending strength, i.e. the ratio of bending strength / compressive strength is not reduced. Dispersed fiber reinforcement increases the relative bending strength by about 70% regardless of the heating temperature.

Bi-functional phosphonium poly(ionic liquid)s catalyzed CO2-promoted hydration of ethylene oxide

The highly selective production of monoethylene glycol (MEG) from ethylene oxide (EO) is desirable at low H2O/EO molar ratio, however, the development of an efficient heterogeneous catalyst for the reaction is a challenge. Herein, a series of bi-functional poly(ionic liquid)s (BF-PILs) were successfully synthesized by radical copolymerization of polymerizable phosphonium/ammonium ionic liquids, N-vinyl imidazole and cross-linker divinylbenzene (DVB). The structure and thermal stability of BF-PILs were characterized by NMR, FT-IR, elemental analysis and TGA. These BF-PILs could be swollen in the H2O and MEG mixture and the swelling ratio (Q) increased with the increase of the MEG mole fraction. Under swelling in the H2O and MEG mixture (1:1), BF-PILs presented an irregular channel structure with the diameter of 1–20 μm observed by the cryo-scanning electron microscope (cryo-SEM). BF-PILs were applied to catalyze the CO2-promoted hydration of EO at a low H2O/EO ratio of 1.5:1. The catalytic activities of phosphonium BF-PILs were superior to ammonium BF-PILs, and poly[(Ph)3VBPBr-VIm] with the greatest Q in the H2O and MEG mixture (1:1) gave highest yield (96.1%) and selectivity (97.3%) of MEG. The CO2-promoted hydration of EO involved the cycloaddition of EO with CO2 to produce ethylene carbonate (EC), and followed by the hydrolysis of EC to produce MEG. Kinetic experiments confirmed that phosphonium ionic liquid species mainly catalyzed CO2 cycloaddition and imidazole catalyzed hydrolysis of EC. Furthermore, poly[(Ph)3VBPBr-VIm] exhibited good generality and could be reused up to eight times without significant decrease of its initial activity.

Synergistic effect of K+and PANI in vanadium oxide hydration by interlayer engineering boosts the ammonium ion storage

AbstractAqueous ammonium‐ion (NH4+) hybrid supercapacitor (AA‐HSC), as a new type of energy storage device with great potential, is in the initial stage of rapid development. Based on its special energy storage mechanism, exploiting novel NH4+‐hosting materials is still a great challenge. Herein, vanadium oxide hydration (VOH) tuned by interlayer engineering of K+/PANI co‐intercalation, named KVO/PANI, is designed for AA‐HSC. Intercalated PANI can shield interaction between NH4+and V–O layers to some extent and enlarge interlayer space, which improves the efficiency of reversible NH4+(de)insertion. However, K+enhances redox activity and electronic conductivity. The synergistic effect of co‐intercalation optimizes intercalation pseudocapacitive behavior during the (de)ammonization process, which is reported in NH4+storage for the first time. Theoretical calculations reveal that the lowered electron transport barrier and enhanced electronic conductivity improve NH4+kinetics and exhibit high capacitance for charge storage. The KVO/PANI can deliver the specific capacitance of 340 F g−1at 0.5 A g−1and retain 177 F g−1at 10 A g−1. Pairing with activated carbon, the AA‐HSC can achieve a decent energy density of 31.8 Wh kg−1. This work gives inorganic/organic co‐intercalation that can enhance the NH4+storage of VOH by interlayer engineering. The strategy can be used to design other materials for aqueous energy storage systems.

Fabrication of Swellable Organic-Inorganic Hybrid Polymers for CO2-Assisted Hydration of Propylene Epoxide.

Swelling is a very common phenomenon in organic substances. However, the swelling behaviors of inorganic substances had rarely been reported. In this study, a new type of swellable organic-inorganic hybrid polymer (PIL@CHT) was designed and successfully synthesized through free-radical copolymerization of polymerizable phosphonium ionic liquid monomer and vinyl-functionalized hydrotalcite (CHT). The swelling behaviors of PIL@CHT in various solvents with a wide range of Hansen solubility parameters (δT) were investigated, and PIL@CHT exhibited excellent swellable capacity in the solvents with δT > 24.4 MPa1/2. The swollen state of the hybrid PIL@CHT in water presented a network structure with a diameter of approximately 8-12 μm, and CHT particles were well dispersed to the channel of PIL. PIL@CHT was applied to catalyze the CO2-assisted hydration of propylene oxide (PO), in which a cascade reaction including the cycloaddition of CO2 and PO and the subsequent hydrolysis of propylene carbonate (PC) occurred. PIL@CHT, combining the active sites of PIL and CHT, synergistically catalyzed this cascade reaction and achieved a high yield (93.0%) and selectivity (98.2%) of 1,2-propanediol (1,2-MPG) under a low H2O/PO ratio of 1.5/1. Moreover, the catalyst could be recycled seven times without any significant loss of catalytic activities and had good substrate generality.

Tin Active Sites Confined in Zeolite Framework as a Promising Shape-Selective Catalyst for Ethylene Oxide Hydration.

Shape-selective stannosilicates have been post-synthesized for the hydration of epoxide to diols. A simple acid treatment has been employed to remove extensively the interlayer double four ring units, converting the three-dimensional (3D) UTL germanosilicate into a 2D layered IPC-1P intermediate. Isomorphous incorporation of tetrahedrally coordinated Sn active centers was realized via solid-liquid treatment of IPC-1P with diammonium hexachlorostannate aqueous solution, which was accompanied by the spontaneous condensation of neighboring silica-rich cfi layers upon calcination and structural construction of a 3D PCR structure. Sn-PCR stannosilicates with tunable Sn contents were thus prepared. With Sn-derived robust Lewis acidity confined in the intersecting 10- and 8-ring channels, the Sn-PCR (Si/Sn molar ratio of 77) catalyst served as a shape-selective nanoreactor for the hydration of ethylene oxide (EO) into ethylene glycol (EG), exhibiting a remarkable EO conversion (99.5 %) as well as a steady EG selectivity (>98.4 %) at greatly reduced H2 O/EO molar ratio and near-ambient reaction temperature.

Effect of Hydration Products on the Interfacial Bonding Properties between Asphalt Binder and Steel Slag Coarse Aggregate

Steel slag needs aging treatment before being used for the coarse aggregate of asphalt mixtures because it has volumetric instability due to the hydration of calcium oxide. This paper investigates the effect of hydration products on the bonding properties between asphalt binder and steel slag coarse aggregates subjected to natural aging treatment. A scanning electron microscope, a fluorescence microscope, and X-ray diffraction testing were used to study the surface morphology, microstructure, and mineral phase of the hydration product layer generated on the aggregate surface of steel slag. A modified water boiling test was conducted to evaluate the water stripping resistance of asphalt film with different boiling times. Pull-off testing on real steel slag aggregates was performed to investigate the effect of the hydration product layer and surface treatment on the bonding strength and interface failure mode. Test results indicated that the hydration products exhibited a loose and porous structure and formed an interlayer to prevent the asphalt film from directly adhering to the aggregate surface of steel slag. The hydration product layer could improve the initial stripping resistance but impair the long-term stripping resistance with increased boiling time. The interlayer of hydration products tended to be the weakest link between asphalt film and steel slag aggregate when subjected to pull-off strength damage. The bonding strength showed a negative linear relation with the stripping rate of asphalt film. After steel slag surface treatment with water-based capillary inorganic waterproofer, the pull-off failure of hydration product layer was avoided and thus improved the bonding strength between asphalt film and steel slag aggregate. The bonding strength and failure mode between asphalt-slag adhesion could be well examined by using pull-off tests. Better insights into asphalt–slag adhesion are useful to design durable asphalt mixtures containing steel slag aggregate.

Temperature-resolved nanoscale hydration of a layered manganese oxide.

Water films captured in the interlayer region of birnessite (MnO2) nanosheets can play important roles in biogeochemical cycling, catalysis, energy storage, and even atmospheric water harvesting. Understanding the temperature-dependent loadings and properties of these interlayer films is crucial to comprehend birnessite reactivity when exposed to moist air and temperature gradients. Using vibrational spectroscopy we show that birnessite intercalates one water (1W) monolayer at up to ∼40 °C, but that loadings decrease by half at up to 85 °C. Our results also show that the vibrational properties of intercalated water are unaffected by temperature, implying that the hydrogen bonding network of water remains intact. Using molecular simulations, we found that the lowered water storage capacity at high temperatures cannot be explained by variations in hydrogen bond numbers or in the solvation environments of interlayer K+ ions initially present in the interlayer region. It can instead be explained by the compounded effects of larger evolved heat, as inferred from immersion energies, and by the larger temperature-driven mobility of water over that of K+ ions, which are electrostatically bound to birnessite basal oxygens. By shedding new light on the temperature-driven intercalation of water in a nanolayered mineral, this study can guide future efforts to understand the (geo)chemical reactivity of related materials in natural and technological settings.