Macroscopic Experiments Research Articles

Microfluidic study of surfactant flooding of heavy oil in layered porous media containing fractures

AbstractSurfactant injection is a promising method for enhanced oil recovery (EOR) due to its effective micro‐displacement mechanisms. However, understanding the interaction of a surfactant solution with heavy oil in porous media is neither straightforward nor well understood, particularly in heterogeneous systems. By enabling in‐situ real‐time monitoring of flow transport, microfluidic studies have provided novel insights into the underlying multiphase physics of flow at the pore scale. This paper examines the two‐phase displacement efficiency of a new surfactant in layered–fractured porous microfluidic patterns, a topic seldom discussed in the literature. To evaluate the performance of the proposed surfactant, we considered several heterogeneous media with varying layer and fracture geometrical characteristics, quantifying displacement efficiency for each case. Based on the analysis of pore‐scale snapshots, it was inferred that the primary mechanisms responsible for EOR during surfactant flooding into heavy oil include pore wall transportation, emulsifications, the deformation of residual oil, inter‐pore or intra‐pore bridging, and wettability alteration. Macroscopic displacement experiments revealed that the width of the swept area from surfactant injection significantly exceeded that of water injection, resulting in a substantially higher oil recovery. Furthermore, it was demonstrated that the direction of fluid flow in relation to fracture orientation plays a critical role in the dynamics of surfactant solution movement and, consequently, the ultimate oil production.

Effect of phenyl functional groups on the adsorption behaviour of dodecyl anionic emulsifiers on oxides on the aggregate surface

ABSTRACT Emulsified asphalt finds extensive application in pavement repair, addressing issues like road ruts and cracks. While the adsorption behaviour of emulsifiers on oxide surfaces (CaCO3 and SiO2) of aggregates is influenced by the presence of phenyl functional groups, the precise mechanism of this influence remains insufficiently understood. This study employs molecular dynamics models and macroscopic experiments to investigate the mechanism involving emulsifiers, sodium ions, and water at aggregate interfaces, quantifying the role of phenyl functional groups from a molecular perspective. The results reveal the following: strong electrostatic attraction between alkaline aggregates and Na+, leading to substantial Na+ adsorption. The phenyl functional groups reduce diffusion coefficient, adsorption energy, and amounts in alkaline aggregates (−34.6%, −16%, −12.5%), while increasing them in acidic aggregates (+15.9%, + 14.7%, + 27.7%). The phenyl functional groups impact hydrogen bond acceptors, TPSA, and emulsifier complexity, altering adsorption. They enhance emulsifier electrostatic potential, affecting adsorption on different surfaces. In summary, this ongoing research framework aims to fine-tune emulsifiers through the use of phenyl functional groups, enhancing adsorption strength, adsorption amount, and diffusion between emulsifiers and aggregates. This work holds great significance for optimizing emulsifier molecular structures.

Research on the propagation mechanisms and meso-mechanical responses of reflective cracking on the asphalt overlays on concrete airfield pavement by Fiber Bragg Grating sensing technology

This study evaluated the propagation mechanisms and dynamic meso-mechanical responses of reflective cracking on the asphalt overlays on concrete airfield pavement based on flexible Fiber Bragg Grating (FBG) sensors. The encapsulated FBG sensors were efficiently calibrated, possessing outstanding capability for the measurement of transverse expansion of lateral reflective cracking propagation. Virtual three-point bending test model was proposed and validated by macroscopic indoor experiments. The DEM model facilitated quantifying the proliferation of reflective cracks, unraveling the trajectory from micro-crack inception to visible macroscopic manifestation. Results indicated that the emergence and elongation of the composite structure experienced three phases: the initiation and accumulation of microcracks, the extension of reflective cracking, and the ultimate penetration. The DEM simulation and FBG sensors were recommended to establish a mutually reinforcing mechanism for nuanced validation of reflective crack formation on the composite structures of asphalt overlays on concrete airfield pavement.

Adsorption mechanism of alkylphenol ethoxylates surfactants (APEO) on anthracite surface: A combined experimental, DFT and molecular dynamics study

The serious hazards posed by inhalable coal dust to the safety, air purity, and health of coal miners can be effectively alleviated through the use of appropriate dust suppressants. The wetting enhancement capabilities of two dust suppressants, octylphenol polyoxyethylene ether (OP-10) and nonylphenol polyoxyethylene ether (NP-10), were examined in this study through experimental and simulation methods. Macroscopic experiments (surface tension, contact angle, coal dust settling time, and water retention) indicate that the shorter the alkyl chain attached to the benzene ring in the surfactant and the lower the surface tension, the more conducive it is to improving the fluidity and suspension stability of anthracite particles in the wetting solution and further improving the interfacial properties and wetting effect between coal dust and the liquid medium. Mesoscopic experiments (laser particle size, FTIR, XPS, UV–visible spectroscopy, BET, and SEM) showed that the relevant properties of APEO-modified coals were greatly changed, especially the anthracite modified with short-chain alkyl groups of OP-10, which exhibited a stronger aggregation effect on the coal dust particles and increased the pore structure and specific surface area of the coal dust. Additionally, the hydrophilic functional groups are augmented, leading to a notable enhancement in the adsorption capacity of OP-10 on the coal surface. Microscopic simulations (Density Functional Theory calculations, Molecular Dynamics simulations) reveal that APEO surfactants with longer alkyl side chains attached to benzene rings hinder the π-π interactions between the coal's aromatic ring structures and the benzene rings in the surfactants. The surface polarity of coal modified with OP-10 is significantly enhanced, resulting in a more pronounced improvement in wetting performance and an increased water retention capability. The study systematically explores surfactant microstructure effects on anthracite wetting, laying essential groundwork for advanced dust suppression system development.

Identification of different lithofacies laminations in oil shale and their mechanical properties

Lamination can greatly enhance the anisotropy and heterogeneity of shale and plays a significant role in influencing hydraulic fracturing. The structure and mechanical difference of different lithofacies lamination are the basis to reveal the fracture propagation mechanism. In this paper, research focused on three continental oil shale with different lithofacies in Qikou sag, Bohai Bay basin, including Quartz-Feldspar dominated shale, Carbonate dominated shale and mixed-mineral shale. Scanning electron microscopy and mineral analysis are used to identify quartz-feldspar lamination and mixture lamination in Quartz-Feldspar dominated shales, as well as carbonate lamination and mixture lamination in Carbonate dominated shales. The distinct laminations with different characteristics were precisely located using FIB, which served as the guiding tool for the indentation experiment. The micromechanical properties of laminations with different lithofacies in oil shale samples are examined using the nanoindentation technique, highlighting their distinct differences. The findings demonstrate that the micromechanical properties of quartz-feldspar lamination in Quartz-Feldspar dominated shales exhibit superior strength, while the mechanical difference between laminations in Quartz-Feldspar dominated shales are significantly larger. The quartz-feldspar lamination exhibits the highest resistance when subjected to indentation force. The mechanical properties of mixture lamination in Quartz-Feldspar dominated shales and Carbonate dominated shales are comparable due to their similar mineral composition. Moreover, in conjunction with macroscopic rock mechanics experiments, it has been verified that the lamination structure facilitates the initiation and propagation of macroscopic fractures under stress loading.

Study on the physical encapsulation mechanism of heavy metals in fly ash carbonation solidification based on synthetic pellets

The physical encapsulation mechanism prevents the leaching of heavy metals by forming calcium carbonate-encapsulated fly ash through the reaction of carbon dioxide and calcium oxide. However, current research in this area primarily involves qualitative analysis, focusing on various methods to enhance the fixation effect of heavy metals. There is a lack of quantitative description regarding how physical encapsulation solidifies heavy metals, and the solidification mechanism of heavy metals is challenging to verify through macroscopic experiments. In this paper, a method for synthesizing small fly ash particles into pellets is proposed to quantitatively study the mechanism of physically encapsulating heavy metals. The data from the carbonation reaction and leaching reaction are fitted using the shrinking core model. The depth of carbonation increases with the lengthening of carbonation time, and the physical encapsulation strengthens the immobilization of heavy metals. The leaching of heavy metals after carbonation can be categorized into three stages based on the shrinking core model: external diffusion, internal diffusion, and chemical reaction control. Synthetic pellets enhance all three stages, especially the external diffusion, which is not detectable with fly ash powder. The fitting results of the experimental data for the carbonation reaction of the enlarged synthetic pellets and the shrinking core model are both above 0.9. This indicates that the primary barrier to leaching of heavy metals is the physical encapsulation formed by the carbonation reaction following the shrinking core model. The physical encapsulation serves as the primary mechanism for the solidification of heavy metals during the carbonation process.

Macroscopic emulation of microscopic magnetic particle systems

In this work we show that macroscopic experiments can be used to investigate microscopic systems. Such macroscopic experiments enable testing the assumptions and results obtained by theoretical considerations or simulations that cannot be obtained under microscope (e.g., the orientation of a spherical particle).To emulate the dynamics of a single hematite cube immersed in water and subjected to a rotating magnetic field, a cubic magnet is firmly positioned in a 3D printed superball shell. The dimensionless parameters of the microscopic and macroscopic systems can be equalized by using a glycerol-water mixture instead of water as well as by the material and infill of the 3D printed shell. The pose of the superball is tracked using ArUco stickers which act as fiducial markers.It was found that there is a qualitative agreement between the macroscopic experiments and theoretical predictions. However, the reduced thermal effects in the macroscopic experiments lead to an increase in friction between the superball and the surface, thus shifting the critical frequency of the system.Since the shell is 3D printed, the given method can be extended to any shape and magnetization orientation.

Cell geometry regulates tissue fracture

In vascular plants, the epidermal surfaces of leaves and flower petals often display cells with wavy geometries forming intricate jigsaw puzzle patterns. The prevalence and diversity of these complex epidermal patterns, originating from simple polyhedral progenitor cells, suggest adaptive significance. However, despite multiple efforts to explain the evolutionary drivers behind these geometrical features, compelling validation remains elusive. Employing a multidisciplinary approach that integrates microscopic and macroscopic fracture experiments with computational fracture mechanics, we demonstrate that wavy epidermal cells toughen the plants’ protective skin. Through a multi-scale framework, we demonstrate that this energy-efficient patterning mechanism is universally applicable for toughening biological and synthetic materials. Our findings reveal a tunable structural-mechanical strategy employed in the microscale design of plants to protect them from deleterious surface fissures while facilitating and strategically directing beneficial ones. These findings hold implications for targeted plant breeding aimed at enhancing resilience in fluctuating environmental conditions. From an engineering perspective, our work highlights the sophisticated design principles the plant kingdom offers to inspire metamaterials.

Study on the mechanism of surfactant droplet wetting and coagulation of respiratory dust: The case of AEO-9

In industrial production, spraying is the most widely used dust control method. However, the traditional pure water spray has poor dust removal effect, and the principles of droplet wetting and dust encapsulation are unclear, resulting in poor dust removal effect. In this study, based on the CLSVOF method, we investigated the dynamic wetting and coalescence process of surfactant droplets and dust particles from a microscopic perspective. By changing the size ratio between the droplets and dust particles, as well as the initial velocity of the droplets, we simulated the spreading and wetting of surfactant droplets on the dust surface and found the optimal parameter range for encapsulating respirable dust. Through the experimental determination of spray atomization characteristics, it was found that the spray pressure of 6 MPa and the use of a 1.2 mm fine atomization nozzle produced a spray field with droplet sizes ranging from 14 to 21 μm, accounting for approximately 62.4 % of the distribution. Around 60 % of the droplets had velocities between 20 and 30 m/s. Dust settling efficiency experiments were conducted under these optimal spray parameters, and the settling efficiency of respirable dust reached 84.33 % within the favorable parameter range. Numerical simulations of the dynamic wetting process of dust-fog coupling at the microscopic level, as well as macroscopic spray experiments, were carried out to validate the reliable results. This method has significant implications for the control of respirable dust.

Effect of Al/Mg Ratio on the Microstructure and Phase Distribution of Zn-Al-Mg Coatings

In contrast with studies such as those on the effect of a single elemental variable on Zn-Al-Mg coatings, Mg/Al is considered a variable parameter for evaluating the microstructure of Zn-Al-Mg coatings in this work, and the combined effect of the two elements is also taken into account. The Mg/Al ratios in the continuous hot-dip plating of low-alumina Zn-Al-Mg coatings were 0.63, 0.75, 1.00, 1.25, and 1.63. respectively, and the microstructures of the different coatings were observed using scanning electron microscopy (SEM). The surface elemental distributions of the coatings were analyzed with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis to understand the phase distributions of the coatings, which mainly consisted of a zinc monomeric phase, a binary eutectic phase (Zn/MgZn2), and a ternary eutectic phase (Zn/Al/MgZn2). Statistical calculations of the phase distributions in colored SEM images were performed using ImageJ-win64 software, comparative analysis of the solidification simulation results was carried out with thermodynamic simulation software (PANDAT-2023), and evaluation of the corrosion resistance of the platings was performed using macroscopic cyclic immersion corrosion experiments. The results show that with the increase in the Mg/Al ratio, the binary eutectic phase in the coatings gradually increased, the variation trend of the ternary eutectic phase was not obvious, and the corrosion resistance of the coatings gradually improved.

Selective and efficient removal of ciprofloxacin from water by bimetallic MOF beads: Mechanism quantitative analysis and dynamic adsorption

MOFs play an important role in the adsorption of antibiotics, but the drawbacks of MOF powders limit their practical applications. Moreover, the dominant adsorption mechanism and the quantitative assessment of MOF powders are less studied. Herein, bimetallic ZIF particles were embedded in chitosan beads via an in-situ growth process (ZnCo-ZIF@CS beads), which could selectively remove ciprofloxacin (CIP) from a complex environment. The maximum adsorption capacity was 348.90 mg/g, superior to that of other advanced adsorbents. ZnCo-ZIF@CS performed efficiently in various actual water samples and showed excellent anti-interference and recycling abilities (only a decrease of 12.74 % after 9 cycles). CIP adsorption could still reach 85.30 % after continuous flow treatment for 600 min. Interestingly, ZnCo-ZIF@CS had a good protective effect on rice seedling growth and alleviated CIP stress in rice seedlings due to the low metal leaching at pH 4.0–11.0. Macroscopic experiments, XPS, 2D-FTIR-COS and DFT results revealed that hydrogen bonding (HB), complexation (CB), electrostatic attraction (EA) and π-π interactions were involved in CIP adsorption. Different interactions dominated CIP adsorption in different pH regions. At pH < 5.0, EA and CB were the main driving forces, accounting for 42–52 % and 27–57 % of the total adsorption; at 5.0 < pH < 9.0, the contribution of EA decreased to < 15 % while CB was still dominant, accounting for ∼ 50 % of the total adsorption, and other effects (HB and π-π) increased to approximately 29–39 %; at pH > 9.0, EA, CB, HB together with π-π caused 1–27 %, 9–31 % and 66–72 % of the total adsorption, respectively. The reaction sequence of functional groups in different CIP solutions and at various pH values was also probed by 2D-FTIR-COS. This study further provides clear evidence for developing robust MOF-based adsorbents and for the mechanism quantitative analysis of pollutant adsorption by MOFs.

Molecular dynamics study on the effect of inorganic salts on the wettability of surfactants on bituminous coal: Sodium dodecyl sulfate and sodium chloride as representatives

To further enhance the wetting ability of surfactants to coal, the mechanism of improving the wetting performance of SDS to bituminous coal by the addition of inorganic salt NaCl was studied through a combination of molecular dynamics (MD) simulation with experimental measurements. In the experiment part, the surface tensions of the mixed NaCl-SDS solutions and the contact angles on the bituminous coal surface were measured. Furthermore, MD simulations were conducted to investigate the adsorption characteristics and wetting mechanism of a mixed NaCl-SDS solution on the coal surface at the atomic scale. In this process, the static potentials of the H2O molecule, coal molecule and SDS molecule were calculated, and the number of hydrogen bonds (H-bonds) formed throughout the whole simulation process, the average H-bond length, the relative concentration distribution (RCD) curve and the mean square displacement (MSD) curve were obtained. The experimental results showed that the surface tension and contact angle were both decreased by the addition of sodium chloride in mixed solutions. When 0.6 mol/L NaCl was added, the surface tension and contact angle reached the minima of 30.45 mN/m and 13.01°, respectively. The MD simulation results showed that, after the addition of NaCl, diffusion and migration of H2O molecules were limited, the number of H-bonds increases, the average bond length decreased, the sorption between H2O molecules and coal molecules was enhanced, and the hydrophilicity of coal surface was improved, which meant that the wetting ability of SDS solution to bituminous coal was enhanced by adding NaCl. The effect of the added NaCl in improving the wettability of SDS on coal was explored from two perspectives with macroscopic experiments and microcosmic simulations, and the added NaCl improved the effects of dust suppressants, and played a key role in preventing dust hazards in coal mines.

Surfactants effects on the self-healing properties of asphalt mixtures in a water environment

Under a certain temperature, cracks in asphalt mixtures can heal themselves, but water in the cracks will reduce the self-healing performance of the asphalt mixture. In this study, surfactants were added to asphalt mixtures. In the presence of water, the characteristics of amphiphilic surfactants are used to promote the adsorption between asphalt and aggregates; In this paper, the ability of surfactants to promote the formation of adsorption of asphalt on the crystal surface is verified using a combination of molecular simulations and macroscopic experiments. Molecular simulation results show that the adsorption energies of asphalt and surfactants, surfactants and silica, and asphalt and silica are all negative. Adsorption can occur between the three interfaces, and the surfactants effectively pulls the asphalt molecules onto the silica molecules, achieving adsorption similar to that between asphalt organic polymers and crystals. Macroscopic experiments show that in asphalt mixtures with active agents added, the active agent can be adsorbed on the surface of the aggregate, part of the asphalt is adsorbed on the surface of the active agent, and part is directly adsorbed on the gravel. Some asphalt is also adsorbed on the aggregate under the action of pure water, but the total adsorption capacity is lower than that of asphalt mixtures containing surfactants.

Deterioration mechanism of coral reef sand concrete under scouring and abrasion environment and its performance modulation

In complex marine environment, coral reef sand concrete structures such as breakwaters are subjected to abrasion by sand-containing currents, which seriously shortens the service life and cycle of structures. Therefore, this paper investigates the health status of on-site breakwaters, moreover, reveals the damage mechanism of coral reef sand concrete (CRSC) under scour and abrasion environments in combination with indoor macroscopic and microscopic experiments. In addition, the effects of fly ash (FA) and silica fume (SF) on the mechanics and durability, hydration and hydration products of CRSC are investigated so that corresponding measures can be proposed to improve the service performance of breakwaters. The results demonstrate the indentation hardness of coral aggregate is greater than that of ITZ and cement stone matrix. Therefore, the ITZ and cement stone matrix with lower hardness are scoured and abraded by water flow containing coral reef blocks with high hardness, resulting in abrasion failure of CRSC. FA and SF prolong the induction period of cement, and reduce the hydration rate and accumulated heat of the accelerated period and second peak. The hydration reaction between the supplementary cementitious material and Ca(OH)2 occurred within 20–40 h, resulting in the third exothermic peak of the system. The hydration process of the admixture-cement system goes through three stages: crystallization nucleation and crystal growth (NG), phase boundary reaction (I) and diffusion (D). FA mainly plays a physical filling role in the early stage, and it reduces the early C-S-H polymerization degree and the total volume of C-S-H phase, but slightly increases C-S-H polymerization degree in later stage. However, SF is involved in hydration reaction in the early stage, and increases the C-S-H polymerization degree and total volume of C-S-H phase.

Effects of step hole geometry and spray-wall interactions on spray atomization in LPDI injector

The study aims to analyze the spray atomization of liquefied petroleum gas direct injection (LPDI) injector based on the macroscopic and microscopic experiments. Two experimental injectors were used in the presence and absence of step hole, and the experimental fuels used n-heptane and n-butane.The macroscopic and microscopic spray characteristics as function of the application of step hole were analyzed using two experimental injectors and n-heptane fuel. The macroscopic spray experiments analyzed the initial spray, after the end of injection and nozzle tip wetting using near-field visualization, and microscopic spray experiment analyzed fuel–air atomization phenomenon as function of the application of step hole using PDPA equipment.In addition, macroscopic and microscopic spray characteristics were analyzed for two experimental fuels and spray-wall impingement using the presence of step hole injector. The macroscopic spray experiment analyzed the spray evaporation characteristics for the two experimental fuels and spray-wall impingement using the schlieren visualization, and microscopic spray experiment analyzed the fuel–air atomization phenomenon as function of the two experimental fuels and spray-wall impingement using PDPA equipment.It was found that the presence of step hole injector showed better atomization results than those of the absence of step hole injector. But, the tip wetting of the presence of step hole injector was poor than that of the absence of step hole injector. Furthermore, based on the schlieren experiment, a comparison of free and flat sprays with the two fuels found that the spray width and area of n-heptane in free spray exceeded those of n-butane owing to the vapor pressure of n-butane. However, in the flat spray, the spray width and area of n-butane were exceeded those of n-heptane. It was found that the atomization was promoted after the spray-wall impingement.

EVA/KH560 synergistically modified recycled concrete mechanical properties - Experiment and molecular dynamics simulations

Considering the long-term working performance of recycled concrete (RC) members, there is a need to compensate for the performance deficiencies of RC. In this study, the mechanical properties of RC were improved by two different modification methods, and the reinforcement effects of RC modified by Silane Coupling Agent (KH560)/Ethylene vinyl acetate copolymer (EVA) and RC modified by EVA alone were compared and analyzed. The effects of separate modification and co-modification on RC were analyzed through multi-scale methods in terms of macro-mechanical properties, microstructure, chemical composition and molecular mechanism, respectively. The results of macroscopic mechanical experiments showed that the compressive and shear strength of EVA/KH560 synergistic modification is higher than that of EVA alone. Scanning Electron Microscope (SEM) data showed that the surface density of the old and new concrete interfaces was higher under EVA/KH560 co-modification. X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) data showed that more cement gel will be produced under EVA/KH560 synergistic modification. Molecular dynamics (MD) simulations show that EVA single modification can produce hydrogen and ionic bonds at the interface of old and new concrete, while EVA/KH560 synergistic modification not only produces them, but also forms a stable Si-O-Si chemical bond.

Modeling study of mesoscale magnetic treatment influencing factors through dynamic softening analysis

In this paper, a new concept of “dynamic softening” is proposed to explain the mechanism of residual stress reduction through “cold” treatment. The impact of grain size, grain boundary width, and grain orientation on the reduction was studied through experimental characterization. To further investigate the relationship between these factors and residual stress reduction, mesoscopic grain, and grain boundary stress reduction were simulated using COMSOL software. The simulation results were validated through macroscopic experiments. The study demonstrates that grain size, grain boundary width, and grain orientation significantly affect residual stress reduction. Specifically, larger grain sizes and narrower grain boundaries are more effective in reducing residual stress within a certain range.

Effective removal of arsenite from water using polylactic acid ZIF-8 biocomposite nanofiber

Water purification from As(III)-contaminated groundwater is difficult but highly needed. Herein, a new polylactic acid ZIF-8 biocomposite nanofiber mat (ZIF-8@PLA/NFM) was fabricated using an electrospinning technique for As(III) decontamination. The active component, ZIF-8 nanoparticles, are uniformly embedded in sustainable PLA fibers and can be rapidly contacted by As(III), achieving fast kinetics and high utilization of nanoparticles. The removal experiments show that the ZIF-8@PLA/NFM can effectively remove As(III), especially in combination with H2O2. The 50%-ZIF-8@PLA/NFM with 1 mM H2O2 reduced 1000 μg/L As(III) to less than 10 μg/L in just 5 min through the synergy of oxidation and adsorption. The maximum sorption capacity for As(III) on 50-ZIF-8@PLA/NFM was 11.61 ± 0.99 mg/g, which increased to 39.25 ± 3.84 mg/g with the addition of H2O2. It performed well in the pH range of 4–9. The combination of H2O2 broadened its effective pH operating range (3–10) as well as enhanced interference resistance, enabling deep removal of As(III) across a wide range of water environments. The As(III)-spiked natural water (100 μg/L) could be purified to drinking standard level by ZIF-8@PLA/NFM within 60 min. In combination with H2O2, the removal efficiency was reduced by only 1.5% at the fifth reuse. Macroscopic experiments and microscopic characterization suggest that the adsorption follows the inner-sphere complexes mechanism. The study provides a novel approach for the fabrication of efficient, easy-to-use, and sustainable MOFs-based biocomposite for As(III) decontamination.

Determination of single crystal thermal expansion in Uranium-6wt%Niobium shape memory alloy using in-situ diffraction and modeling of textured polycrystalline samples

In-situ neutron diffraction and ex-situ dilatometry experiments were performed on a chemically banded, quenched uranium-6wt% niobium shape memory alloy to study the impact of deformation-(detwinning-) induced texture on the evolution of thermally induced strains (and associated stresses). Thermal heating and cooling cycles between 5K and 473K were performed in-situ with neutron diffraction, and the lattice strain evolution is reported for the observed monoclinic α″ phase. Comparisons between the measured diffraction strains and macroscopic dilatometry experiments reveal relationships between micro- and macro-level thermal expansion. Softening of the texture during heating suggests that twin boundary motion can accommodate the large internal thermal strains which are approximately 2% greater than that typically observed during the 175K heating interval used to age more randomly oriented polycrystalline material. Assuming weak constraint of neighboring grains in randomly textured polycrystals, the single crystal thermal expansion tensor is extracted from measurements of lattice strains over the range 5K to 473K. Predictions of polycrystalline thermal expansion, based upon this single crystal thermal expansion tensor, are shown to compare favorably with bulk thermal expansion observations of the as quenched microstructure. However, such a lower-bound estimate is insufficient to explain all aspects of the behavior of the textured material, where the matrix is not isotropic. It is hypothesized that relaxation processes which occur within the quenched microstructure during heating are responsible for the distinct thermal expansion behavior observed during the initial heating cycle compared to cooling and subsequent cycling.

Adsorption Mechanisms of Glyphosate on Ferrihydrite: Effects of Al Substitution and Aggregation State.

Ferrihydrite is one of the most reactive iron (Fe) (oxyhydr)oxides in soils, but the adsorption mechanisms of glyphosate, the most widely used herbicide, on ferrihydrite remain unknown. Here, we determined the adsorption mechanisms of glyphosate on pristine and Al-substituted ferrihydrites with aggregated and dispersed states using macroscopic adsorption experiments, zeta potential, phosphorus K-edge X-ray absorption near-edge structure spectroscopy, in situ attenuated total reflectance Fourier transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy, and multivariate curve resolution analyses. Aggregation of ferrihydrite decreases the glyphosate adsorption capacity. The partial substitution of Al in ferrihydrite inhibits glyphosate adsorption on aggregated ferrihydrite due to the decrease of external specific surface area, while it promotes glyphosate adsorption on dispersed ferrihydrite, which is ascribed to the increase of surface positive charge. Glyphosate predominately forms protonated and deprotonated, depending on the sorption pH, monodentate-mononuclear complexes (MMH1/MMH0, 77-90%) on ferrihydrites, besides minor deprotonated bidentate-binuclear complexes (BBH0, 23-10%). Both Al incorporation and a low pH favor the formation of the BB complex. The adsorbed glyphosate preferentially forms the MM complex on ferrihydrite and preferentially bonds with the Al-OH sites on Al-substituted ferrihydrite. These new insights are expected to be useful in predicting the environmental fate of glyphosate in ferrihydrite-rich environments.