Thermal rectification induced by Wenzel–Cassie wetting state transition on nano-structured solid–liquid interfaces

Thermal rectification refers to the phenomenon by which the magnitude of the heat flux in one direction is much larger than that in the opposite direction.In this study,we propose to implement the thermal rectification phenomenon in an asymmetric solid–liquid–solid sandwiched system with a nano-structured interface.By using the non-equilibrium molecular dynamics simulations,the thermal transport through the solid–liquid–solid system is examined,and the thermal rectification phenomenon can be observed.It is revealed that the thermal rectification effect can be attributed to the significant difference in the interfacial thermal resistance between Cassie and Wenzel states when reversing the temperature bias.In addition,effects of the liquid density,solid–liquid bonding strength and nanostructure size on the thermal rectification are examined.The findings may provide a new way for designs of certain thermal devices.

Heat transfer for Marangoni convection over a vapor-liquid interface due to an imposed temperature gradient

A similarity analysis for Marangoni convection induced flow over a vapor-liquid interface due to an imposed temperature gradient was carried out. The analysis assumes that the surface tension varies linearly with temperature but the temperature variation is a power law function of the location. The similarity solutions are presented numerically and the associated transfer characteristics are discussed.

Ultralow Interfacial Thermal Resistance of Graphene Thermal Interface Materials with Surface Metal Liquefaction

Developing advanced thermal interface materials(TIMs)to bridge heat-generating chip and heat sink for constructing an efficient heat transfer interface is the key technology to solve the thermal management issue of high-power semiconductor devices.Based on the ultra-high basal-plane thermal conductivity,graphene is an ideal candidate for preparing high-performance TIMs,preferably to form a vertically aligned structure so that the basal-plane of graphene is consistent with the heat transfer direction of TIM.However,the actual interfacial heat transfer efficiency of currently reported vertically aligned graphene TIMs is far from satisfactory.In addition to the fact that the thermal conductivity of the vertically aligned TIMs can be further improved,another critical factor is the limited actual contact area leading to relatively high contact thermal resistance(20-30 K mm^(2) W^(−1))of the“solid-solid”mating interface formed by the vertical graphene and the rough chip/heat sink.To solve this common problem faced by vertically aligned graphene,in this work,we combined mechanical orientation and surface modification strategy to construct a three-tiered TIM composed of mainly vertically aligned graphene in the middle and micrometer-thick liquid metal as a cap layer on upper and lower surfaces.Based on rational graphene orientation regulation in the middle tier,the resultant graphene-based TIM exhibited an ultra-high thermal conductivity of 176 W m^(−1) K^(−1).Additionally,we demonstrated that the liquid metal cap layer in contact with the chip/heat sink forms a“liquid-solid”mating interface,significantly increasing the effective heat transfer area and giving a low contact thermal con-ductivity of 4-6 K mm^(2) W^(−1) under packaging conditions.This finding provides valuable guidance for the design of high-performance TIMs based on two-dimensional materials and improves the possibility of their practical application in electronic thermal management.

Evolution of bonding interface in solid-liquid cast-rolling bonding of Cu/Al clad strip

Cu/Al clad strips are prepared using solid?liquid cast-rolling bonding(SLCRB)technique with a d160mm×150mm twin-roll experimental caster.The extent of interfacial reactions,composition of the reaction products,and their micro-morphology evolution in the SLCRB process are investigated with scanning electron microscope(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD).In the casting pool,initial aluminized coating is first generated on the copper strip surface,with the diffusion layer mainly consisting ofα(Al)+CuAl2and growing at high temperatures,with the maximum thickness of10μm.After sequent rolling below the kiss point,the diffusion layer is broken by severe elongation,which leads to an additional crack bond process with a fresh interface of virgin base metal.The average thickness is reduced from10to5μm.The reaction products,CuAl2,CuAl,and Cu9Al4,are dispersed along the rolling direction.Peeling and bending test results indicate that the fracture occurs in the aluminum substrate,and the morphology is a dimple pattern.No crack or separation is found at the bonding interface after90°-180°bending.The presented method provides an economical way to fabricate Cu/Al clad strip directly.

Passivating buried interface with multifunctional novel ionic liquid containing simultaneously fluorinated anion and cation yielding stable perovskite solar cells over 23% efficiency

Interfacial defects and energy barrier would result in serious interfacial non-radiative recombination losses.In addition,the quality of perovskite films is highly dependent on deposition substrates.Consequently,there is an urgent desire to develop multifunctional interface modulators to manage the interface between electron transport layer and perovskite layer.Here,we report a multifunctional buried interface modulation strategy that 4-fluoro-phenylammonium tetrafluoroborate (FBABF_(4)) consisting of simultaneously fluorinated anion and cation is inserted between SnO_(2)layer and perovskite layer.It is uncovered by time-of-flight secondary ion mass spectroscopy that the anion and cation in modifier are mainly located at this interface,which is put down to coordination bond of the fluorine atom on BF_(4)^(-) with SnO_(2),and the hydrogen bond of the fluorine atom on FBA^(+) with formamidinium.This suggests that simultaneous fluorination of anion and cation in the ionic liquid molecule is of crucial importance to ameliorate interfacial contact through chemical linker.The interface modification approach enables the realization of interfacial defect passivation,interfacial energy band alignment modulation,and perovskite crystallization manipulation,which are translated into enhanced efficiency and stability as well as significantly suppressed hysteresis.The multiple functions of FBABF_(4) endow the modified solar cells excellent photovoltaic performance with an efficiency exceeding 23%along with appealing long-term stability.This work highlights the critical role of fluorination strategy in engineering multifunctional organic salt modulators for improving interfacial contact.

Insight into the behavior at the hygroscopicity and interface of the hydrophobic imidazolium-based ionic liquids

How to completely remove the water from ionic liquids(ILs)is difficult for researchers because of the hygroscopicity of ILs.In order to study the hygroscopicity of ILs,two kinds of ILs,1-Butyl-3-methylimidazolium hexafluorophosphate([Bmim][PF6])and 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)([Bmim][NTf_(2)])were investigated by molecular dynamics simulations.Although[Bmim][PF6]and[Bmim][NTf_(2)]are hydrophobic,both of the ILs could absorb water molecules from the vapor.In this work,the process of absorbing water from the vapor phase was studied,and the water molecules could disperse into the IL.Aggregation was observed with increasing the water concentration.Although the absorbed water increases obviously,the amount of free water and small cluster in the ILs does not change significantly and always stays at a certain level.The amount of free water and small cluster in[Bmim][PF6]is more than that in[Bmim][NTf_(2)],which is consistent with their hydrophobicity.In addition,the liquid-vacuum and liquid–liquid interfaces of the ILs were simulated and analyzed in detail.The number density distribution and angle distribution indicated that[Bmim]+cations arrangement regularly at the IL-vacuum interface.The butyl chain point to the vacuum,while the imidazlium ring is close to the IL phase region and perpendicular to the interface.While at the IL-water interface,the cations and anions are disordered.

Microstructure and Solid/Liquid Interface Evolutions of Directionally Solidified Fe-Al-Ta Eutectic Alloy

A modified Bridgman directional solidification technique was used to prepare Fe-Al-Ta eutectic in situ composites at different growth rates ranging from 6 to 80 μm/s. The directionally solidified FeAl-Ta eutectic composites are composed of two phases: Fe（Al,Ta） matrix phase, and Fe2 Ta（Al） Laves phase. Solidification microstructure is affected by solidification rate. Microstructure of the Fe-Al-Ta eutectic alloy grown at 6.0 μm/s is broken-lamellar eutectic. Eutectic colonies are formed with the increase of the solidification rate. Microstructures are mainly composed of the lamellar or fibrous eutectic at the center of the colony and coarse lamellar eutectic zone at the boundary. Meanwhile, the inter-lamellar spacing（or the inter-rod spacing） is decreased. The spacing adjustments are also observed in Fe-Al-Ta eutectic alloy. The solid/liquid interface evolves from planar interface to shallow cellular interface, then to deep cellular, and finally to shallow cellular planar with the increase of the solidification rate.

Effect of SDBS on interfacial electron transfer at the liquid/liquid interface by thin layer method

The effect of an adsorbed anionic surfactant sodium dodecyl benzene sulfonate （SDBS） on electron transfer （ET） reaction between ferricyanide aqueous solution and decamethylferrocene （DMFc） located on the adjacent organic phase was investigated for the first time by thin layer method. The adsorption of SDBS at the interface resulted in a decay in the cathodic plateau current of bimolecular reaction with increasing concentrations of SDBS in aqueous phase. However, the rate constant of electron transfer （ket） increased monotonically as the SDBS concentrations increased from 0 to 200 p, moFL. The experimental results showed that SDBS formed patches on the interface and influenced the structure of electrical double layer. 2009 Xiao Quan Lu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Unraveling abnormal buried interface anion defect passivation mechanisms depending on cation-induced steric hindrance for efficient and stable perovskite solar cells

Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal an abnormal buried interface anion defect passivation mechanism depending on cationinduced steric hindrance.The IL molecules containing the same anion([BF4]^(-))and different sizes of imidazolium cations induced by substituent size are used to manipulate buried interface.It was revealed what passivated interfacial defects is mainly anions instead of cations.Theoretical and experimental results demonstrate that the large-sized cations can weaken the ionic bond strength between anions and cations,and facilitate the interaction between anions and SnO2as well as perovskites,which is conducive to interfacial defect passivation and ameliorating interfacial contact.It can be concluded that interfacial chemical interaction strength and defect passivation effect are positively correlated with the size of cations.The discovery breaks conventional thinking that large-sized modification molecules would weaken their chemical interaction with perovskite.Compared with the control device(21.54%),the device based on 1,3-Bis(1-adamantyl)-imidazolium tetrafluoroborate(BAIMBF4)with maximum size cations achieves a significantly enhanced efficiency of 23.61%along with much increased moisture,thermal and light stabilities.

Voltammetric Studies on Heteropoly Phosphotungstovanadate Anions Across the Liquid/Liquid Interface

Electrochemical transfer behavior of V ⅤW 11 -V Ⅴ 3W 9 heteropoly anions on the water/nitrobenzene interface was investigated by means of cyclic voltammetry. The effect of the solution acidity on the transfer behavior and the stable pH range for the heteropoly anions were studied. The stability of mixed tungstovanadate decreases with increasing the number of vanadium atoms. The main transfer species within the potential window have the negative charges of 4 and the transfer process is diffusion controlled. The apparent transfer potential Δ w o Ψ 0 and the free energy Δ G 0 w→o tr for the heteropoly anions can be obtained from the experimental data. For the different anions, the Δ w o Ψ 1/2 pH relationship can be expressed as: Δ w o Ψ 1/2 =constant-53pH.

Understanding fundamentals of electrochemical reactions with tender X-rays:A new lab-based operando X-ray photoelectron spectroscopy method for probing liquid/solid and gas/solid interfaces across a variety of electrochemical systems

Electrocatalysis is key to improving energy efficiency,reducing carbon emissions,and providing a sustainable way of meeting global energy needs.Therefore,elucidating electrochemical reaction mechanisms at the electrolyte/electrode interfaces is essential for developing advanced renewable energy technologies.However,the direct probing of real-time interfacial changes,i.e.,the surface intermediates,chemical environment,and electronic structure,under operating conditions is challenging and necessitates the use of in situ methods.Herein,we present a new lab-based instrument commissioned to perform in situ chemical analysis at liquid/solid interfaces using ambient pressure X-ray photoelectron spectroscopy(APXPS).This setup takes advantage of a chromium source of tender X-rays and is designed to study liquid/solid interfaces by the“dip and pull”method.Each of the main components was carefully described,and the results of performance tests are presented.Using a three-electrode setup,the system can probe the intermediate species and potential shifts across the liquid electrolyte/solid electrode interface.In addition,we demonstrate how this system allows the study of interfacial changes at gas/solid interfaces using a case study:a sodium–oxygen model battery.However,the use of APXPS in electrochemical studies is still in the early stages,so we summarize the current challenges and some developmental frontiers.Despite the challenges,we expect that joint efforts to improve instruments and the electrochemical setup will enable us to obtain a better understanding of the composition–reactivity relationship at electrochemical interfaces under realistic reaction conditions.

Orientation and Structure of Ionic Liquid Cation at Air/[bmim][BF4] Aqueous Solution Interface

The watermiscible room temperature ionic liquid 1butyl3methylimidazolium tetrafluorob orate （[bmim] [BF4]） is a model system for studying the interactions between ionic liquid and water molecules. In this work the orientational structure of the low concentrated aqueous solution of [bmim] [BF4] at the air/liquid interface was investigated by sum frequency gener ation vibrational spectroscopy. It has been found that at very low concentrations, the butyl chain exhibited a significant gauche defect, indicating a disordered conformation; and the cation ring oriented with a fairly small tilting angle at the surface. When the concentration increased, the cation ring tended to lie flat at the surface, and the gauche defects of the butyl chain decreased due to the intermolecular chainchain interactions and the consequent more ordered interfacial molecular arrangement. Additionally, the antisymmetric stretching mode in the PPP and SPS spectra exhibited a peak shift, showing that there exists more than one kind of orientation or chemical environment for the butyl CH3 group. These results may shed new light on understanding the surface behavior of watermiscible ionic liquids as well as the imidazolium based surfactants.

An APXPS endstation for gas–solid and liquid–solid interface studies at SSRF

In the past few decades, various surface analysis techniques find wide applications in studies of interfacial phenomena ranging from fundamental surface science,catalysis, environmental science and energy materials.With the help of bright synchrotron sources, many of these techniques have been further advanced into novel in-situ/operando tools at synchrotron user facilities, providing molecular level understanding of chemical/electrochemical processes in-situ at gas–solid and liquid–solid interfaces.Designing a proper endstation for a dedicated beamline is one of the challenges in utilizing these techniques efficiently for a variety of user's requests. Many factors,including pressure differential, geometry and energy of the photon source, sample and analyzer, need to be optimized for the system of interest. In this paper, we discuss the design and performance of a new endstation at beamline02 B at the Shanghai Synchrotron Radiation Facility for ambient pressure X-ray photoelectron spectroscopy studies.This system, equipped with the newly developed hightransmission HiPP-3 analyzer, is demonstrated to be capable of efficiently collecting photoelectrons up to 1500 eV from ultrahigh vacuum to ambient pressure of 20 mbar.The spectromicroscopy mode of HiPP-3 analyzer also enables detection of photoelectron spatial distribution with resolution of 2.8 ± 0.3 lm in one dimension. In addition,the designing strategies of systems that allow investigations in phenomena at gas–solid interface and liquid–solid interface will be highlighted through our discussion.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.

Mathematical Modelling of Particle Movement Ahead of the Solid-liquid Interface in Continuous Casting

Whether the particle will be trapped by the solid-liquid interface or not is dependent on its moving behavior ahead of the interface, so a mathematical model has been developed to investigate the movement of the particle ahead of the solid-liquid interface. Based on the theory for the boundary layer, the fluid velocity field near the solid-liquid interface was obtained, and the trajectories of particles were calculated by the equations of motion for particles. In this model, the drag force, the added mass force, the buoyance force, the gravitational force, the Saffman force and the Basset history force are considered. The results show that the behavior of the particle ahead of the solid-liquid interface is affected by the physical property of the particle and fluid flow. And in the continuous casting process, if it moves in the stream directed upward or downward near vertical solid-liquid interface or in the horizontal flow under the solid-liquid interface, the particle with the diameter from 5 um to 60um can reach the solid-liquid interface. But if it moves in horizontal flow above the solid-liquid interface, only the particle with the diameter from 5 um to 10 um can reach the solid-liquid interface.

MASS TRANSFER TO LIQUID-LIQUID INTERFACE

Experiments have been done on mass transfer to a liquid-liquid interface on which inert gas bubbles are sparged.To simulate the pyrometallurgy system of melten slag-metal(or matte),aqueous solution-mercury(or zinc amalgam) system was used.The mass transfer coefficients of indicator ions as a function of bubble parameters have been determined.The experimental results show satisfactory agreement with the mass transfer model proposed Previously.

Liquid metal as an efficient protective layer for lithium metal anodes in all-solid-state batteries

Lithium metal batteries with inorganic solid-state electrolytes have emerged as strong and attractive candidates for electrochemical energy storage devices because of their high-energy content and safety.Nonetheless,inherent challenges of deleterious lithium dendrite growth and poor interfacial stability hinder their commercial application.Herein,we report a liquid metal-coated lithium metal(LM@Li)anode strategy to improve the contact between lithium metal and a Li6PS5Cl inorganic electrolyte.The LM@Li symmetric cell shows over 1000 h of stable lithium plating/stripping cycles at 2mA cm^(-2) and a significantly higher critical current density of 9.8 mAcm^(-2) at 25°C.In addition,a full battery assembled with a high-capacity composite LiNbO3@-LiNi_(0.7)Co_(0.2)Mn_(0.1)O_(2)(LNO@NCM721)cathode shows stable cycling performance.Experimental and computational results have demonstrated that dendrite growth tolerance and physical contact in solid-state batteries can be reinforced by using LM interlayers for interfacial modification.

Investigation of the Lipophilicity of 2-Benzoylpyridine-Thiosemicarbazone Based on the Ion Transfer across the Liquid/Liquid Interface

The ion transfer reaction of 2-benzoylpyridine-thiosemicarbazone (HL), which has antimicrobial and antifungal properties and anticancer activity, has been studied to determine its lipophilicity by cyclic voltammetry at the water/1,2-dichloroethane (1,2-DCE) interface. The physicochemical parameters such as standard partition coefficient (lgPI)andthestandardGibbsenergyoftransfer("G0tr,,wI "o)oftheprotonatedformoftheligandwere measured asa function of pH in aqueous phase. The protonated form of the ligand exhibited reversible or quasi-reversible voltammograms at the1,2-DCEintherangeofpH1-5.Theprotonationconstantsoftheligand,pKa1andpKa2,weredeterminedspectrophotometrically and were found to be 12.14 and 3.24, respectively. The standard Gibbs energy of transfer ("G0tr,,wN" o) and the partition coefficient of neutral species (lgPN) were also determined by the shake-flask method. The standard Gibbs energy of transfer of this compound across the water/1,2-DCE interface was evaluated as the quantitative measure of its lipophilicity. The difference between lgPI and lgPN was related to the degree of charge delocalization and was used to evaluate qualitatively the lipophilicity of the ligand.

Investigation of the oxidation of hydroquinone at the liquid/liquid interface

The oxidation of hydroquinone(QH_2) was investigated for the first time at liquid/liquid(L/L) interface by scanning electrochemical microscopy(SECM).In this study,electron transfer(ET) from QH_2 in aqueous to ferrocene(Fc) in nitrobenzene (NB) was probed.The apparent heterogeneous rate constants for ET reactions were obtained by fitting the experimental approach curves to the theoretical values.The results showed that the rate constants for oxidation reaction of QH_2 were sensitive to the changes of the dri...

Fractal Description of the Solid/Liquid Interface of a Directionally Solidified Superalloy with Different Phosphorus Content

The solid/liquid interface of a directionally solidified Ni-base superalloy with different phosphorus contents was quantitatively described by means of fractat method.When the solidification rate was fixed,the relationship between the fractal dimensionality of the solid/liquid interface and the phos- phorus content of the test alloy was given.Combined the thermodynamics and fractal theory,the ef- fect mechanism of phosphorus content on fractal dimensionality of the solid/liquid interface was discussed.