Large Repulsion Research Articles

Pickering emulsions stabilized by cellulose nanofibers with tunable surface properties for thermal energy storage

Cellulose nanofibers (CNFs) have been widely used as a renewable emulsifier to stabilize two immiscible liquids due to their intrinsic amphiphilicity and excellent emulsifying ability. However, it remains challenging to fully understand the effects of carboxylate group content and surface charge density on the emulsifying ability of CNFs and the stability of Pickering emulsion. Herein, carboxymethylated CNFs were extracted from bleached kraft pulp using etherification reaction and high-pressure homogenization, allowing for easy surface charge density and size adjustment by changing sodium chloroacetate content and homogenization cycles. The optimizing CNFs possessed a high Zeta potential (−71.2 mV) and a suitable carboxylate group content (1.81 mmol/g), which enabled CNFs to irreversibly adsorb at the hydrophobic paraffin wax (PW) droplet surface and form interfacial steric barriers, providing large electrostatic repulsion between the PW droplets against coalescence. Thus, the CNF-stabilized PW emulsions could be stored for more than 6 months. Moreover, the phase change enthalpy of the freeze-dried emulsion is as high as 193.7 J/g, which provides the emulsion to reversibly store and release heat. This work provides a comprehensive insight into the interfacial stability mechanism of CNFs as stabilizers and facilitates the potential application in thermal energy storage.

Effect of droplet charge density on stabilization of oil‐in‐dispersion emulsions co‐stabilized by binary mixed surfactants and nanoparticles

AbstractIonic surfactant and similarly charged nanoparticles can co‐stabilize oil‐in‐dispersion (OID) emulsions at extremely low concentrations (0.001 cmc/0.001 wt%), in which particles do not adsorb at the oil/water interface but distribute in the aqueous phase forming a dispersion. In this paper, the effect of droplet charge density on stabilization of the n‐decane‐in‐water OID emulsion was examined by using a cetyl trimethyl ammonium bromide (CTAB)/C12B (dodecyl dimethyl carboxyl betaine) binary mixture at a low fixed total concentration (0.01 mM) with varying molar fractions of CTAB. A model based on the Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory is proposed to calculate interaction energies between droplets and between droplets and particles. It is found that the droplet charge density can be well compensated by particle concentration along the stabilization boundary, and the OID emulsion still follows the DLVO stabilization. Particles tend to surround droplets at large distances but may form a monolayer between approaching droplets at shorter distances, which significantly reduces the van der Waals attraction between droplets. In addition, the induced auxiliary droplet–particle repulsion is proportional to the number of particles per unit area of droplet surfaces, which together with the droplet–droplet repulsion ensures a large total repulsion preventing droplets from flocculation and coalescence. This work explains quantitatively the stabilization of OID emulsions, which have potential applications in emulsion products such as foods, cosmetics, pesticides, and various industrial emulsion systems. Moreover, the development of the OID emulsions represents an important advancement in green chemistry as it substantially reduces the required amounts of emulsifiers and their environmental impact after use.

Electrochemical Reduction of Perfluorooctanoic Acid (PFOA): An Experimental and Theoretical Approach.

Perfluorooctanoic acid (PFOA) is an artificial chemical of global concern due to its high environmental persistence and potential human health risk. Electrochemical methods are promising technologies for water treatment because they are efficient, cheap, and scalable. The electrochemical reduction of PFOA is one of the current methodologies. This process leads to defluorination of the carbon chain to hydrogenated products. Here, we describe a mechanistic study of the electrochemical reduction of PFOA in gold electrodes. By using linear sweep voltammetry (LSV), an E0' of -1.80 V vs Ag/AgCl was estimated. Using a scan rate diagnosis, we determined an electron-transfer coefficient (αexp) of 0.37, corresponding to a concerted mechanism. The strong adsorption of PFOA into the gold surface is confirmed by the Langmuir-like isotherm in the absence (KA = 1.89 × 1012 cm3 mol-1) and presence of a negative potential (KA = 3.94 × 107 cm3 mol-1, at -1.40 V vs Ag/AgCl). Based on Marcus-Hush's theory, calculations show a solvent reorganization energy (λ0) of 0.9 eV, suggesting a large electrostatic repulsion between the perfluorinated chain and water. The estimated free energy of the transition state of the electron transfer (ΔG‡ = 2.42 eV) suggests that it is thermodynamically the reaction-limiting step. 19F - 1H NMR, UV-vis, and mass spectrometry studies confirm the displacement of fluorine atoms by hydrogen. Density functional theory (DFT) calculations also support the concerted mechanism for the reductive defluorination of PFOA, in agreement with the experimental values.

Ubiquitous light real-space pairing from long-range hopping and interactions

We systematically examine how long-range hopping and its synergy with extended interactions leads to light bound pairs. Pair properties are determined for a dilute extended Hubbard model with large on-site repulsion (U) and both near- and next-nearest neighbor hopping (t and t′) and attraction (V and V′), for cubic and tetragonal lattices. The presence of t′ and V′ promotes light pairs. For tetragonal lattices, t′<0 pairs can be lighter than non-interacting particles, and d-symmetric pairs form. Close packing transition temperatures, T⁎, are estimated for the Bose-Einstein condensation (BEC) of pairs to be kBT⁎∼0.1t‾, where t‾ is the geometric mean of the hoppings on the Cartesian axes. When pairs have d-symmetry, the condensate has d-wave character. Thus, the presence of both t′ and V′ leads ubiquitously to small strongly bound pairs with an inverse mass that is linear in hopping, which could lead to high temperature BECs.

Electrostatically Shielded Transportation Enabling Accelerated Na+ Diffusivity in High‐Performance Fluorophosphate Cathode for Sodium‐Ion Batteries

AbstractA typical polyanionic based material Na3V2(PO4)2O2F (Na3VPO2F) attracts much interest as a cathode for large‐scale sodium‐ion batteries in consideration of its stable structure and remarkable energy density. Nevertheless, the large coulombic attraction and repulsion suffered by the mobile Na+ from structural anions and surrounding Na+, respectively, result in a torpid reaction kinetics and inferior rate capability. Herein, Br−‐doped and Na+ vacancy preinstalled Na3−yVPO2−xBrxF is prepared to dilute the charges on and inside the Na+ transportation tunnel. In virtue of density functional theory analysis, Na3−yVPO2−xBrxF reveals a reduction in the bandgap and an increase in electronic conductivity. Meanwhile, the almost electrostatically shielded tunnel in Na3−yVPO2−xBrxF alleviates the coulombic hindrance imposed on Na+ during its (de)intercalation, which demonstrates a Na+ diffusivity about five times higher than that of Na3VPO2F. Consequently, the Na3−yVPO2−xBrxF cathode shows a superior rate capacity of 77.7 mAh g−1 under 50 C and great cycling property corresponding to a high capacity retention of 94.4% over 800 cycles at 10 C. The assembled Na3−yVPO2−xBrxF//hard‐carbon sodium‐ion full‐cell presents excellent specific energy/power (226 Wh kg−1@15424.2 W kg−1) as well as outstanding long‐term cyclic stability over 1000 cycles at 5 C.

Interference of holon strings in 2D Hubbard model

The 2D Hubbard model with large repulsion is an important problem in condensed matter physics. At half filling, its ground state is an antiferromagnet (AMF). The dope AMF below half filling is believed to capture the physics of high Tc superconductors. And the fermion excitation of this dope AMF is theorized as splitting up into holons and spinons that carry charge and spin separately. It is believed that these exotic holons and spinons are the origins of the unusual properties of high Tc superconductors. Despite the interests in holons and spinons, the direct observations of these excitations remain difficult in solid state experiments. Here, we show that with the rapid advances in the experimental techniques in cold atoms, the direct observation of holons is possible in quantum quench dynamic processes in cold atom settings. We show that the well-known holon-strings generated by the motion of a holon as well as their interferences can be detected by the measurements spin–spin correlations and demonstrate the presence of the Marshall phase associated with a holon string reflecting an underlying AMF background. Moreover, we show that the interferences of the holon strings make a holon propagate anisotropically, with a diffusion pattern clearly distinct from that of spinless fermions. At the same time, we show that these interferences lead to a large suppression in magnetic order in the region swept through by the strings (even to about 95% for some bond). We further demonstrate the Marshall phase of the holon-strings by comparing the dynamics of holon in the tJ model with that of the so-called σtJ -model, which is the tJ model with the Marshall phase removed. The holons in these models propagate entirely differently.

Segregation and domain formation in non-local multi-species aggregation equations

A system of aggregation equations describing nonlocal interaction of two species is studied. When interspecies repulsive forces dominate intra-species repulsion, phase segregation may occur. This leads to the formation of distinct phase domains, separated by moving interfaces.The one dimensional interface problem is formulated variationally, and conditions for existence and nonexistence are established. The singular limit of large and short-ranged repulsion in two dimensions is then considered, leading to a two-phase free boundary problem describing the evolution of phase interfaces. Long term dynamics are investigated computationally, demonstrating coarsening phenomenon quantitatively different from classical models of phase separation. Finally, the interplay between long-range interspecies attraction and interfacial energy is illustrated, leading to pattern formation.

P3‐Na0.45Ni0.2Mn0.8O2/Na2SeO4 Heterostructure Enabling Long‐Life and High‐Rate Sodium‐Ion Batteries

AbstractSodium‐based layered oxide cathodes are competitive candidates for commercial sodium‐ion batteries owing to their high theoretical capacities, low costs, and simple synthesis. P3‐type layered oxides with large open channels enable fast Na+ transport and hence good rate performance. However, the lower crystal symmetry of P3‐type oxides and variation of Na+ contents in the Na layer during desodiation/sodiation lead to large electrostatic repulsion changes between TMO2 slabs (TM=Transition Metal), resulting in irreversible phase transitions, and fast performance degradation. Herein, a potential Na+ conductor Na2SeO4 is first found that it can be easily in situ grown on P3‐Na0.45Ni0.2Mn0.8O2 to form a novel heterostructure P3‐Na0.45Ni0.2Mn0.8O2/Na2SeO4. The synergy between P3‐Na0.45Ni0.2Mn0.8O2 and Na2SeO4 functions in promoting Na+ diffusion and suppressing P3‐O3 phase transitions upon deep sodiation, which results in recorded high‐rate capability (68.2% capacity retention with retained 83.9 mAh g−1 capacity at 6400 mA g−1) and superior cycling stability (capacity retention 75% after 1000 cycles) among all reported P3‐type cathodes. Thus, it is believed that this novel heterostructure design opens a new pathway to promote practical applications for layered oxide cathodes in sodium‐ion batteries.

Transport and Model Calculation of Microplastics Under the Influence of Ionic Type, Strength, and Iron Oxide

Microplastics (MPs) in soil have attracted extensive attention as an emerging pollutant, and the transport of MPs is affected by their own physical and chemical properties, the chemical composition of soil solutions, and soil minerals. However, in the presence of oxides, the underlying mechanism for the transport of MPs in different ionic types and ionic strengths is still not fully understood. In this study, the effects of ionic type, ionic strength, and iron oxide on the transport of polystyrene microplastics (PSMPs) with different functional groups were investigated through stability experiments and transport experiments. The colloid transport model, CD-MUSIC model, and DLVO theory were used to explore the transport mechanism. The results showed that normalized concentrations (c/c0) of PSMPs were 0.99 in the NaH2PO4 background and 0.94 in the CaCl2 background, respectively, which indicated that the strongest stability of PSMPs was observed in the former and the weakest in the latter. Different ionic types had different effects on the transport of PSMPs. For the cations Na+ and Ca2+, Ca2+ strongly inhibited PSMPs transport in pure quartz sand because of the bridging effect and strong charge neutralization effect; the recovery rate of the PSMPs in the effluent was (43.83±1.71)%, and a first-order retention coefficient on the second kinetic Site-2 (k2a) was 1.54 min-1. The presence of iron oxide enhanced the inhibition, the recovery rate of the PSMPs in the effluent decreased to (6.04±0.40)%, and k2a increased to 5.33 min-1. For the anions Cl- and PO43-, the transport of PSMPs in pure quartz sand was dominated by surface electronegativity of PSMPs, and PSMPs exhibited lower electronegativity under Cl- background and thus showed higher recovery[(92.95±0.63)%] and lower k2a (0.19 min-1). However, in the presence of iron oxides, the Zeta potential of the quartz sand surface was the controlling factor for PSMPs transport. According to results of the CD-MUSIC model, PO43- could be easily adsorbed on the iron oxide surface to form innersphere complexes, which reduced the surface electronegativity of the iron-loaded quartz sand and enhanced the transport of PSMPs, higher recovery[(76.22±1.39)%], and lower k2a (0.66 min-1). Moreover, the species of the formed innersphere complex was controlled by the PO43- concentration, and different species of innersphere complexes had distinct negative surface charges. Higher surface electronegativity of the iron-loaded quartz sand was observed under higher PO43- concentration, which was not conducive to the transport of PSMPs. Further, the transport ability of PSMPs decreased with the increase in ionic strength. Finally, the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was used to calculate the variation in the primary barrier between PSMPs and the collector under the conducted experimental conditions, which helped better elucidate the transport behavior of PSMPs. The variation in the primary barrier was consistent with the transport ability of PSMPs, and a higher primary barrier indicated a larger repulsion between PSMPs and the collector, which was in favor of PSMPs transport.

Functionalization of pine kernel protein by pH-shifting combined with ultrasound treatments: Further improvement with increasing acidity

As a novel plant protein, developing various aspects of pine kernel protein (PKP) functionality is essential to meet the demand for protein-rich foods. To achieve this, the PKP was functionalized by a combination of pH-shifting and ultrasound techniques. The solubility, emulsification and droplet stability of the PKP in the pH range suitable to food (pH 3 to 7) were further investigated. The pH 12-shifting was an effective strategy to increase the solubility of PKP under extreme acidic and neutral conditions, characterized by a higher content of β-sheets and random coils, a greater exposure of free sulfhydryl and hydrophobic groups. Furthermore, appropriate ultrasonic power (250 W) further improved the solubility of PKPs by disrupting intermolecular hydrogen and hydrophobic bonds. As the ambient acidity increased, the emulsions exhibited higher viscoelasticity and stronger protein interactions. Especially at pH 3, the oil droplets stabilized by U250-PKP-12 (PKP treated with 250 W ultrasound-assisted pH 12-shifting) were homogeneously dispersed and surrounded by dense protein, maintaining small particle size and large electrostatic repulsion, and there was no apparent creaming or phase separation in the emulsions after 10 days of storage. Thus, the functionality of PKP after pH-shifting combined with ultrasonic treatments is further enhanced by increasing the environmental acidity.

Exact one-particle density matrix for SU(N) fermionic matter-waves in the strong repulsive limit

We consider a gas of repulsive NN-component fermions confined in a ring-shaped potential, subjected to an effective magnetic field. For large repulsion strengths, we work out a Bethe ansatz scheme to compute the two-point correlation matrix and then the one-particle density matrix. Our results hold in the mesoscopic regime of finite but sufficiently large number of particles and system size that are not accessible by numerics. We access the momentum distribution of the system and analyse its specific dependence of interaction, magnetic field and number of components NN. In the context of cold atoms, the exact computation of the correlation matrix to determine the interference patterns that are produced by releasing cold atoms from ring traps is carried out.

Front Cover: Association of Pyramidal Boron Lewis Superacids with Pyridines: Bending 2,4,6‐Collidine with the 10‐Sulfonium‐9‐boratriptycene (Z. Anorg. Allg. Chem. 9‐10/2023)

This cover picture shows a Lewis adduct between a pyramidal boron Lewis superacid and a bulky pyridine. Due to the high Lewis acidity and pyramidalization at the boron atom, the boron-nitrogen bond is shorter than that in other Lewis adducts. This induces large steric repulsions resulting in the deformation of the collidine Lewis base. This fundamental observation illustrating the importance of the structural reorganization of Lewis bases in a process of association with a bulky Lewis acid is relevant to the field of frustrated Lewis pairs chemistry (DOI: 10.1002/zaac.202300009).

Stability and structure of multiply occupied sII CO2 clathrate hydrates: A possibility for carbon capturing

The hydrate method is an important technology that has been widely studied for carbon dioxide (CO2) capture, utilization and storage (CCUS). Improving the gas reserves per unit volume is the key goal for this technology. Therefore, the occurrence behaviors of large CO2 hydrate cages, the structure II, occupied with 1–5 gas molecules were investigated via molecular dynamics (MD) in this study. The occupancy rate, stability and decomposition laws of CO2 hydrate were systematically analyzed. The results indicate that the large hydrate cages occupied with 4–5 molecules were directly broken due to excessively large intermolecular repulsion. In contrast, the large hydrate cages occupied with 3 molecules showed an obvious four-rupture-stage: (1) a small part of cages rupturing; (2) metastable cages formation along with the escape of CO2 molecules, and the cages do not continue to break until all the CO2 molecules escape; (3) pure residual cages rupturing, with no CO2 gas existing in cages in this stage; and (4) complete decomposition of the CO2 hydrate. It is interesting that the large hydrate cages occupied with 2 gas molecules are stable, and 2 is the maximum occupancy number. The pressure is more important for improving the stability of the double-occupancy hydrate, and a higher pressure (20 MPa) strengthens the stability of the CO2 hydrate structure. The findings in this study indicate that the sII CO2 hydrate under sufficiently high pressure can maximally increase the storage efficiency by 36.5 wt%.

Polyethylene glycol regulated carnallite decomposition-crystallization: Experimental and theoretical analysis

Currently, the “crystallization-flotation” process is widely used for the industrial production of KCl. However, the significant aggregation of KCl and NaCl in the decomposition-crystallization stage of carnallite leads to inefficient separation of the two particles in the flotation stage, which restricts the production of high-grade KCl. In this study, environmentally friendly polyethylene glycol (PEG) was used to regulate the decomposition-crystallization of carnallite for the first time, and the high-grade KCl was successfully prepared by reducing the degree of crystal aggregation. The crystals were characterized by SEM-EDS, FT-IR, XRD and AFM, and it was found that PEG which average Mn 800 (PEG 800) could adsorb on the crystal surface and effectively disperse NaCl and KCl. It was also found that there are two mechanisms by which PEG 800 achieves dispersion. On the one hand, PEG 800 micelles contain polyoxyethylene chains with large steric repulsion, which can prevent the adhesion of particles. On the other hand, PEG 800 can weaken the electric potential on the surface of KCl and NaCl and reduce the electrostatic interaction force between the particles. Finally, the behavior of Na, K, and Cl before and after the addition was simulated by molecular dynamics, and molecular dynamics calculations showed that PEG 800 could weaken the effect of NaCl on KCl.

Comparison of cellulose and chitin nanofibers on Pickering emulsion stability—Investigation of size and surface wettability contribution

There is an increasing concern about developing biobased colloid particles for Pickering stabilization due to the environment-friendliness and health-safety needs. In this study, Pickering emulsions were formed by using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidized cellulose nanofibers (TOCN) and chitin nanofibers prepared by TEMPO-mediated oxidation (TOChN) or partial deacetylation (DEChN). The physicochemical characterizations of Pickering emulsions demonstrated that the higher cellulose or chitin nanofiber concentrations, surface wettability, and zeta-potential, the higher effectiveness in Pickering stabilization. Specifically, even though DEChN was at a shorter size (with a length of 254 ± 72 nm) as compared to TOCN (with a length of 3050 ± 1832 nm), it showed an excellent stabilization effect on emulsions at the concentration of 0.6 wt% due to its higher affinity to soybean oil (water contact angle of 84.38 ± 0.08°) and large electrostatic repulsion between oil particles. Meanwhile, when the concentration was 0.6 wt%, long TOCN (water contact angle of 43.06 ± 0.08°) formed a three-dimensional network in the aqueous phase, which produced a superstable Pickering emulsion resulting from the limited moving of droplets. These results provided important information on the formulation of Pickering emulsions stabilized by polysaccharide nanofibers with suitable concentration, size and surface wettability.

Dynamical Gibbs–non-Gibbs transitions in Widom–Rowlinson models on trees

We consider the soft-core Widom-Rowlinson model for particles with spins and holes, on a Cayley tree of order $d$ (which has $d + 1$ nearest neighbours), depending on repulsion strength $\beta$ between particles of different signs and on an activity parameter $\lambda$ for particles. We analyse Gibbsian properties of the time-evolved intermediate Gibbs measure of the static model, under a spin-flip time evolution, in a regime of large repulsion strength $\beta$. We first show that there is a dynamical transition, in which the measure becomes non-Gibbsian at large times, independently of the particle activity, for any $d \geq 2$. In our second and main result, we also show that for large $\beta$ and at large times, the measure of the set of bad configurations (discontinuity points) changes from zero to one as the particle activity $\lambda$ increases, assuming that $d \geq 4$. Our proof relies on a general zero-one law for bad configurations on the tree, and the introduction of a set of uniformly bad configurations given in terms of subtree percolation, which we show to become typical at high particle activity.

Micelle Formation of Dodecanoic Acid with Alkali Metal Counterions.

Alkali series with different atomic numbers affect the physicochemical properties of aqueous solutions. The micellar properties of aqueous solutions of dodecanoate as surfactants were measured by changing the counterions (C12-Na, C12-K, C12-Rb, and C12-Cs). A plot of Krafft temperature vs. alkali metal atomic number showed a downward convex curve, with its minimum temperature (20°C) in the C12-K system. By contrast, a plot of the critical micelle concentration (CMC) vs. alkali metal atomic number exhibited an upward convex curve with the maximum CMC (25.6 mmol L-1) at C12-K. Furthermore, the minimum surface tension (γ min ) of the solution at the CMC increased with increasing atomic number (C12-Na ≈ C12-K < C12-Rb < C12-Cs). The size of the dodecanoate micelles decreased with increasing atomic number. The ionization degree of the micelles also increased with increasing atomic number of the alkali metal. Small-angle X-ray scattering (SAXS) measurements revealed that alkali dodecanoate micelles formed spherical to ellipsoidal structures. In addition, micelles from the shell region showed large electrostatic repulsion, judging from the shape of the spectrum in the higher Q -1 region. From the measurement results of the solubilization of naphthalene into the micelles, the size of the micelles corresponded to the maximum solubilization quantity of naphthalene.

Stabilizing hydrogen-mediated sextuple bonds by quintuple superatomic bonding and a bond.

Multiple bond orders of four and five are frequently obtained for d-block elements. However, compounds with sextuple bonding (2σ, 2π, and 2δ), for instance, Cr2, Mo2 and W2, are less stable and trapped only in the gas phase or inert matrices, probably resulting from large repulsion of two σ-type (σs and ) orbitals within the same zone. Herein, a superatomic bonding model is proposed to describe experimentally synthesized bridging hydride compounds. We theoretically predicted four unprecedented quintuple bridging hydride species with large EHL values, among which [(Cp)2Sc2(μ-H)5]- and [(Cp)2Mn2(μ-H)5]- (Cp = cyclopentadienyl) contain quintuple superatomic bonding (σ, 2π, and 2δ). In particular, two other species, [(Cp)2Ti2(μ-H)5]- and [(Cp)2V2(μ-H)5]+, were found to feature stable hydrogen-mediated sextuple bonding comprising a quintuple superatomic delocalized bond and an extra localized bond. Thereinto, the superatomic σs bond disperses to the outer space for better overlap with the orbitals of bridging H atoms, thus leaving the inner regions with low electron densities and providing adequate space for the bond. These two quintuple bridging hydride compounds are verified to have thermal stability by molecular dynamics simulations and expected to provide an effective strategy to synthesize molecules with stable hydrogen-mediated sextuple bonding under normal experimental conditions.

Effect of Mo addition on hydrogen segregation at α-Fe grain boundaries: A first-principles investigation of the mechanism by which Mo addition improves hydrogen embrittlement resistance in high-strength steels

The development of high-strength steels is essential for realizing a decarbonized society; however, to achieve this, the problem of hydrogen embrittlement must be solved. The effectiveness of adding Mo has been demonstrated to address this issue, but its underlying mechanism has not yet been clarified. To investigate this mechanism, we developed a calculation method to evaluate the effect of adding alloying elements on the grain boundary segregation of H using parameters calculated via first-principles calculations. Accordingly, the segregation energies of H with and without Mo segregation near the grain boundary were calculated. Based on the obtained segregation energies, the concentration of H at the grain boundary was calculated for a given amount of Mo under the heat treatment conditions normally assumed. The results showed that a small amount of Mo segregates to α-Fe grain boundaries and significantly reduces the grain boundary concentration of H owing to repulsive interactions between Mo and H. This indicates that Mo addition improves the resistance to hydrogen embrittlement by reducing the grain boundary H concentration. The physical origin of these repulsive interactions was further investigated by decomposing them into mechanical and chemical contributions; we found that these repulsive interactions are mainly caused by the chemical contribution. Furthermore, the crystal orbital Hamiltonian population indicated that the chemical contribution can be attributed to the large core repulsion between Mo–H at α-Fe grain boundaries (in comparison to that between Fe–H) owing to the larger atomic orbital of Mo. The proposed calculation method as well as the information obtained from our evaluations can help in the development of high-strength steels with excellent resistance to hydrogen embrittlement and in the improvement the resistance to hydrogen embrittlement of various metallic materials.

Synthesis and performance of a novel bio-oil-based dispersant as coal water slurry

With pyrolytic bio-oil as raw material, an efficient bio-oil-based dispersant (BOBD) applied to coal water slurry (CWS) has been synthesized successfully by grafting polymerization of the organic fractions from the bio-oil and acrylic acid (AA) in the mild condition. As a comparison, two commercial dispersants, namely poly (styrene sulfonic acid) sodium (PSS) and sodium lignosulfonate (SL) were employed. The structures and properties of the synthesized BOBD were characterized by using FTIR, 1H NMR, GC/MS, GPC, zeta potential, contact angle, and surface tension. The results showed the molecular weight of the BOBD was concentrated at 832 g/mol and 1954 g/mol. The surface tension and contact angle of BOBD aqueous solution were 47.71mN/m−1 and 60.8° respectively. The zeta potential of the suspension prepared from BOBD-water-coal was −67.1 mV. Using BOBD as a dispersant, the apparent viscosity of CWS loading 66 wt% coal dropped to 288 mPa·s at 0.3 wt% BOBD, and the maximum coal content reached 72 wt%. BOBD exhibited better viscosity reduction and stability enhancement capabilities than PSS and SL. The excellent dispersion performance of BOBD was due to the large electrostatic repulsion and steric hindrance derived from the grafted acrylic polymer, which effectively dispersed the coal particles uniformly. The rheological behavior of CWS with BOBD belonged to pseudoplastic fluid. The synthesized BOBD not only had an excellent dispersion performance but also could overcome the shortcomings of secondary pollution caused by PSS and SL containing element sulfur as dispersants in combustion. In addition, the synthetic route possessed simple, environmentally friendly and sustainable characteristics. The research opened up a new way for the utilization of bio-oil.