Electrophoresis is the motion of a charged colloidal particle in an electrolyte under an applied electric field. The electrophoretic velocity of a spherical particle depends on the dimensionless ...electric field strength \(\beta =a^*e^*E_\infty ^*/k_B^*T^*\), defined as the ratio of the product of the applied electric field magnitude \(E_\infty ^*\) and particle radius \(a^*\), to the thermal voltage \(k_B^*T^*/e^*\), where \(k_B^*\) is Boltzmann's constant, \(T^*\) is the absolute temperature, and \(e^*\) is the charge on a proton. In this paper, we develop a spectral element algorithm to compute the electrophoretic velocity of a spherical, rigid, dielectric particle, of fixed dimensionless surface charge density \(\sigma\) over a wide range of \(\beta\). Here, \(\sigma =(e^*a^*/\epsilon ^*k_B^*T^*)\sigma ^*\), where \(\sigma ^*\) is the dimensional surface charge density, and \(\epsilon ^*\) is the permittivity of the electrolyte. For moderately charged particles (\(\sigma ={O}(1)\)), the electrophoretic velocity is linear in \(\beta\) when \(\beta \ll 1\), and its dependence on the ratio of the Debye length (\(1/\kappa ^*\)) to particle radius (denoted by \(\delta =1/(\kappa ^*a^*)\)) agrees with Henry's formula. As \(\beta\) increases, the nonlinear contribution to the electrophoretic velocity becomes prominent, and the onset of this behaviour is \(\delta\)-dependent. For \(\beta \gg 1\), the electrophoretic velocity again becomes linear in field strength, approaching the Hückel limit of electrophoresis in a dielectric medium, for all \(\delta\). For highly charged particles (\(\sigma \gg 1\)) in the thin-Debye-layer limit (\(\delta \ll 1\)), our computations are in good agreement with recent experimental and asymptotic results.
•Electric field perpendicular to oil’s flow direction can also reduce oil viscosity.•The viscosity reduction is insensitive to the field direction.•Electric field weakens the interaction between wax ...crystals.•The weakened interaction should be the primary reason for the viscosity reduction.
It has been reported that the application of a high-voltage electric field parallel to the oil flow direction or to a quiescent waxy crude oil can reduce the viscosity of the oil. In this work, an electric field perpendicular to the flow direction is applied to a flowing waxy crude oil in a rheometer equipped with in-situ electric field manipulation, and it is observed that viscosity reduction similar to that obtained with electric field parallel to the flow direction can also be achieved. This, therefore, confirms that the treatment efficacy is insensitive to the direction of the electric field compared to the oil flow direction. Moreover, the non-Newtonian characteristics of the treated crude oil become less significant, and more viscosity reduction is achieved at higher electric field strength and lower oil temperature. After the removal of the electric field, the reduced viscosity gradually recovers and the viscosity reduction disappears after about two days. Though it is found that the electric treatment causes an increase in wax crystal size and aggregation of particles to some extent, we think that weakened interaction between wax particles due to electric field exposure should be the primary reason of the viscosity reduction according to the knowledge of suspension rheology and the mechanism of waxy crude oil rheology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Large‐strain (K,Na)NbO3 (KNN) based piezoceramics are attractive for next‐generation actuators because of growing environmental concerns. However, inferior performance with poor temperature stability ...greatly hinders their industrialized procedure. Herein, a feasible strategy is proposed by introducing VK/Na′\{\rm{V}}_{{\rm{K/Na}}}^{^\prime }\‐VO..\{{\rm{V}}_{\mathop {\rm{O}}\limits^{..} }}\ defect dipoles and constructing grain orientation to enhance the strain performance and temperature stability of KNN‐based piezoceramics. This textured ceramics with 90.3% texture degree exhibit a giant strain (1.35%) and a large converse piezoelectric coefficient d33* (2700 pm V−1), outperforming most lead‐free piezoceramics and even some single crystals. Meanwhile, the strain deviation at high temperature of 100 °C–200 °C is obviously alleviated from 61% to 35% through texture engineering. From the perspective of practical applications, piezo‐actuators are commonly utilized in the form of multilayer. In order to illustrate the applicability on multilayer actuators, a stack‐type actuator consisted of 5 layers of 0.4 mm thick ceramics is fabricated. It can generate large field‐induced displacement (11.6 µm), and the promising potential in precise positioning and optical modulation are further demonstrated. This work provides a textured KNN‐based piezoceramic with temperature‐stable giant strain properties, and facilitates the lead‐free piezoceramic materials in actuator applications.
Texture engineering can improve the strain performance as well as temperature stability of KNSN/NiO in contrast with non‐textured piezoceramics. Outstanding d33* of 2700 pm V−1 at 50 kV cm−1 is achieved, which is remarkable in lead‐free piezoceramics and even comparable to single crystals. Excellent applicability on multilayer actuators endows this ceramic with broad application prospects.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A built‐in electric field in electrocatalyst can significantly accumulate higher concentration of NO3− ions near electrocatalyst surface region, thus facilitating mass transfer for efficient nitrate ...removal at ultra‐low concentration and electroreduction reaction (NO3RR). A model electrocatalyst is created by stacking CuCl (111) and rutile TiO2 (110) layers together, in which a built‐in electric field induced from the electron transfer from TiO2 to CuCl (CuCl_BEF) is successfully formed . This built‐in electric field effectively triggers interfacial accumulation of NO3− ions around the electrocatalyst. The electric field also raises the energy of key reaction intermediate *NO to lower the energy barrier of the rate determining step. A NH3 product selectivity of 98.6 %, a low NO2− production of <0.6 %, and mass‐specific ammonia production rate of 64.4 h−1 is achieved, which are all the best among studies reported at 100 mg L−1 of nitrate concentration to date.
An electrocatalyst is created by stacking CuCl (111) and rutile TiO2 (110) layers together. A built‐in electric field induced from the electron transfer from TiO2 to CuCl (CuCl_BEF) is thus formed, which triggers interfacial accumulation of NO3− ions around the electrocatalyst. A NH3 product selectivity of 98.6 %, a low NO2− production of <0.6 %, and mass‐specific ammonia production rate of 64.4 h−1 is achieved.
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A dual‐porphyrin heterostructure is successfully constructed by coupling tetrakis (4‐carboxyphenyl) zinc porphyrin (ZnTCPP) with tetrakis (4‐hydroxyphenyl) porphyrin (THPP). The high photocatalytic ...H2 evolution rate of 41.4 mmol h−1 g−1 is obtained for ZnTCPP/THPP under full spectrum, which is ≈5.1 and ≈17.0 times higher than that of pure ZnTCPP and THPP, respectively. The significantly enhanced activity is mainly attributed to the giant interfacial electric field formed between dual porphyrins, which greatly facilitates efficient charge separation and transfer. Meanwhile, similar conjugated structures of dual porphyrins also provide proper interface match and decrease interface defects, thus inhibiting the recombination of photoproduced carriers. By rationally combining the appropriate band structures and high‐quality interfacial contact of dual porphyrins, this work provides a fresh insight into the interfacial electric field construction to improve the photocatalytic performance.
A strong interfacial electric field is constructed through the dual‐porphyrin heterostructure of tetrakis (4‐carboxyphenyl) zinc porphyrin (ZnTCPP)/tetrakis (4‐hydroxyphenyl) porphyrin (THPP), which greatly promotes charge separation and transfer. Meanwhile, dual porphyrins possess proper interface match to reduce recombination sites of interface charge carriers. Consequently, ZnTCPP/THPP exhibits an excellent photocatalytic H2 evolution rate of 41.4 mmol h−1 g−1, exceeding most of the reported photocatalysts.
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Metal–organic frameworks (MOFs) have been intensively studied as a class of semiconductor‐like materials in photocatalysis. However, band bending, which plays a crucial role in semiconductor ...photocatalysis, has not yet been demonstrated in MOF photocatalysts. Herein, a representative MOF, MIL‐125‐NH2, is integrated with the metal oxides (MoO3 and V2O5) that feature appropriate work functions and energy levels to afford the corresponding MOF composites. Surface photovoltage results demonstrate band bending in the MOF composites, which gives rise to the built‐in electric field of MIL‐125‐NH2, boosting the charge separation. As a result, the MOF composites present 56 and 42 times higher activities, respectively, compared to the pristine MOF for photocatalytic H2 production. Upon depositing Pt onto the MOF, ∼6 times higher activity is achieved. This work illustrates band bending of MOFs for the first time, supporting their semiconductor‐like nature, which would greatly promote MOF photocatalysis.
A representative metal–organic framework (MOF), MIL‐125‐NH2, was integrated with MoO3 or V2O5. Given their suited work functions and energy levels, band bending of the MOF occurs, giving rise to improved charge separation. Accordingly, the activity of the MOF composites toward photocatalytic H2 production is considerably enhanced. This is an unprecedented report with evidence on semiconductor‐like band bending of MOFs.
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The relatively low operating voltage window is the main factor limiting the energy density of aqueous energy storage devices. The delicate design of heterostructured electrode materials can ...efficiently increase the intrinsic electrochemical performance through synergistic effects. For the first time, to broaden the voltage window of aqueous supercapacitors the synergistic effect between boroncarbonitrides (BCN) and built‐in electric field existing in heterostructures is designed to utilize. Based on this design concept, MnO/MnS@BCN electrode materials are synthesized, in which the synergistic effect can effectively strengthen the storage of electrolyte ions on the electrode surface, thus inhibiting the electrolysis of H2O and eventually broadening the voltage window of aqueous supercapacitor. In MnO/MnS@BCN‐based symmetrical supercapacitors, the voltage window of the device is extended from 1.2 V (single‐component) to 2 V, with the energy density enhanced to 75.0 W h kg−1. The strategy blazes an efficient and convenient path to broaden the intrinsic voltage window of transition metal oxide supercapacitors.
The voltage window of a MnO/MnS@BCN symmetrical supercapacitor is broadened to 2.0 V through the synergistic effect between boroncarbonitrides and the MnO/MnS heterostructure, which doubles the single‐component devices.
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Zn metal as one of promising anode materials for aqueous batteries but suffers from disreputable dendrite growth, grievous hydrogen evolution and corrosion. Here, a polycation additive, polydiallyl ...dimethylammonium chloride (PDD), is introduced to achieve long‐term and highly reversible Zn plating/stripping. Specifically, the PDD can simultaneously regulate the electric fields of electrolyte and Zn/electrolyte interface to improve Zn2+ migration behaviors and guide dominant Zn (002) deposition, which is veritably detected by Zeta potential, Kelvin probe force microscopy and scanning electrochemical microscopy. Moreover, PDD also creates a positive charge‐rich protective outer layer and a N‐rich hybrid inner layer, which accelerates the Zn2+ desolvation during plating process and blocks the direct contact between water molecules and Zn anode. Thereby, the reversibility and long‐term stability of Zn anodes are substantially improved, as certified by a higher average coulombic efficiency of 99.7 % for Zn||Cu cells and 22 times longer life for Zn||Zn cells compared with that of PDD‐free electrolyte.
A polycation additive is introduced to simultaneously regulate the electric fields of electrolyte and Zn/electrolyte interface, which improves Zn2+ migration behaviors and guides dominant Zn (002) deposition, thereby facilitating homogeneous Zn nucleation and growth concomitantly, and blocking the parasitic side reactions derived from water.
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Constructed through relatively weak noncovalent forces, the stability of organic supramolecular materials has shown to be a challenge. Herein, the designing of a linear conjugated polymer is proposed ...through creating a chain polymer connected via bridging covalent bonds in one direction and retaining π‐stacked aromatic columns in its orthogonal direction. Specifically, three analogs of linear conjugated polymers through tuning the aromatic core and its covalently linked moiety (bridging group) within the building block monomer are prepared. Cooperatively supported by strong π–π stacking interactions from the extended aromatic core of perylene and favorable dipole–dipole interactions from the bridging group, the as‐expected high crystallinity, wide light absorption, and increased stability are successfully achieved for Oxamide‐PDI (perylene diimide) through ordered molecular arrangement, and present a remarkable full‐spectrum oxygen evolution rate of 5110.25 µmol g−1 h−1 without any cocatalyst. Notably, experimental and theoretical studies reveal that large internal dipole moments within Oxamide‐PDI together with its ordered crystalline structure enable a robust built‐in electric field for efficient charge carrier migration and separation. Moreover, density functional theory (DFT) calculations also reveal oxidative sites located at carbon atoms next to imide bonds and inner bay positions based on proven spatially separated photogenerated electrons and holes, thus resulting in highly efficient water photolysis into oxygen.
Three PDI‐based linear conjugated polymers are synthesized for highly effective and long‐term photocatalytic oxygen evolution through rational design. Bicarbonyl embedded Oxamide‐PDI exhibits 5110.25 µmol g−1 h−1 under full spectrum irradiation without any co‐catalyst exceeding most reported organic polymer photocatalysts, characterization, and DFT calculation reveals the ordered stacking, robust build‐in electric field, and low exciton binding energy contribute greatly.
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Pulsed electric field (PEF) is an attractive and efficient non-thermal technology that can advance functionality, extractability, and retrieval of nutritionally beneficial compounds. For industrial ...PEF food processing, high electric field consistency is of importance for continuous operation and an economical return-of-investment within a short period.
The technology uptake at an industrial scale is still low due to the shortage of reliable and more practical electrical systems. Therefore, designing an application-specific and cost-effective electrical system is essential for commercial use of this novel technology. This review describes the requirements and developments of the electrical systems employed in PEF food processing.
The process parameters and control variables of the PEF system are not only critical for the designing of the electrical systems but also for the experts of the food sciences. Inadequate or insufficient description of different engineering aspects of experimental procedures is a hindrance in allowing the work to be reproduced in other laboratories. This review describes the critical process parameters and the designing methodology of the specialized equipment required in food processing as a guide for the designers and the researchers of this technology.
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∙PEF is an efficient non-thermal technology for food processing.∙The engineering aspects of this technology to promote industrial usage has studied.∙This review discuss the electrical system of PEF in food processing.∙The complexity of PEF obstructs the upscaling from pilot-scale to industrial scale.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
