In this study,FTIR and XPS spectroscopy,specific surface area and pore size analyses,wetting and other experimental means have been applied to investigate respirable coal dust surface properties and wetting mechanism....In this study,FTIR and XPS spectroscopy,specific surface area and pore size analyses,wetting and other experimental means have been applied to investigate respirable coal dust surface properties and wetting mechanism.The research shows that coal dust surface structures,chemical and element compositions are changed in the refining process of coal dust.Compared with large particle coal dust,respirable coal dust is a weak hydrophilic and strong hydrophobic substance.The reason:the smaller the particle size of coal dust,the more unsaturated its surface.The absorption of air is strong and it is easy to form an air film on coal dust surfaces. Coal dust contact with water is actually a compound contact of liquid in contact with a solid and gas in contact with a solid. The smaller the particle size,the larger the pore volume and the higher the degree of surface roughness,the larger the area of gas in contact with a solid and the worse the coal dust wettability.Another reason is that the changes in the composition of atoms on the dust surface and structures affect coal dust wettability.The results of this study establish a theoretical basis for the invention of effective reduced-dust technology.展开更多
Influences of temperature and Sn-Cu droplet's composition on reactive wettings of Cu(100), Cu(110), and Cu(111) surfaces were analyzed, by using molecular dynamics(MD) calculations. As a result, the spreading on C...Influences of temperature and Sn-Cu droplet's composition on reactive wettings of Cu(100), Cu(110), and Cu(111) surfaces were analyzed, by using molecular dynamics(MD) calculations. As a result, the spreading on Cu(110)(Cu(100)) has the fastest(slowest) wetting kinetics. A higher temperature or a diluter Cu content in the Sn-Cu alloy droplet results in a higher wettability. Moreover, this work has addressed a theory for positioning the interface separating the liquidus and solidus alloys in the spreading film to confirm the hypothesis that the reactive wetting will come to the end when the interface saturates with the temperature-dependent solidus weight fraction of Cu.展开更多
The dynamic pore wetting plays an important role in the flotation of porous particle,such as coal,fly ash,gasification slag,etc.Water phase get into the pores and crevices on the surface and inside of the particles,cr...The dynamic pore wetting plays an important role in the flotation of porous particle,such as coal,fly ash,gasification slag,etc.Water phase get into the pores and crevices on the surface and inside of the particles,creating a dense water layer that covers their surface and decreases their floatability.It is important to reduce the adverse impact of dynamic pore wetting on the flotation performance of porous particles.Thus,this review is to highlight the dynamic pore wetting behavior,and its role in the porous particle flotation as well as the proposed regulation methods to weaken the pore wetting.The characterization approaches of the dynamic pore wetting are discussed including the optical method for the capillary and the nuclear magnetic resonance(NMR)method for porous particles.The surface tension and viscosity of liquid significantly affect the pore wetting degree of porous particles during the 60 min wetting process.Pre-wetting time adjustment,pore compression,pore filling,and hydrophobic modifications are introduced to decrease the wetting percentage of pores in porous particles and further improve their flotation performance.This critical review will provide some guidance for studying the dynamic wetting behavior of pores and enhancing the floatability of porous particles.展开更多
After gas drainage, the outburst seam is dry and, consequently, during subsequent mechanized mining, unwanted dust production is extensive. Because the hard dustfall typically has a small particle size it contains a h...After gas drainage, the outburst seam is dry and, consequently, during subsequent mechanized mining, unwanted dust production is extensive. Because the hard dustfall typically has a small particle size it contains a high percentage of respirable dust. Considering these factors, this paper improved the efficiency of dustfall by reducing the surface tension of the liquid used as a wetting agent, then configuring five kinds of wetting agents by adopting various doses and types of surfactants, neutral inorganic salts and chemical additives, etc. After purchasing DA-85 and SRJ-1 wetting agent, the surface tension and critical micelle concentration of seven kinds of wetting agents were measured using the capillary rise method. Wetting agent A was confirmed to have the best comprehensive effect. The experiments were optimized by measuring and comparatively analyzing contact angles of pure water, SRJ-1 wetting agent and wetting agent A on the surface of different coal samples using a contact angle measurement instrument （HARKE- SPCA）. By comparative analysis, dust-proof effects of seam, dynamic pressure water infusion and high- pressure spray in the tunneling face at the Daning coal mine using pure water, wetting agent SRJ-1 and A, it was determined that after using wetting agent A, the average dust concentration in the place of the mining machine driver, 10 m and 110 m away from the tunneling front is approximately 300 rag/ m^3, 240 mg/m^3 and 100 mg/m^3, respectively, This practice increased the dust-proof efficiency dramati- cally and achieved a good comprehensive dust-proof effect.展开更多
Water molecules could form a liquid droplet on the water monolayer on a specific solid surface, which has been referred to as ‘‘ordered water monolayer that does not completely wet water'' at room temperatur...Water molecules could form a liquid droplet on the water monolayer on a specific solid surface, which has been referred to as ‘‘ordered water monolayer that does not completely wet water'' at room temperature. In contrast to the water molecules, the family of alcohol molecules has the same OH polar head and various lengths of their hydrophobic nonpolar tail; the length of the hydrophobic tail can affect the hydrophobic effect. In this study, using molecular dynamics simulations, we investigated the wetting behaviors of methanol, ethanol, and propanol molecules adsorbed on a SiO_2 surface. The results showed that the methanol, ethanol, and propanol molecules could form an ordered monolayer on the SiO_2 surface and a droplet on top of this monolayer, with different contact angles. The differences in the contact angles were attributed to the differences in the interactions between the alcohol monolayer and droplet.展开更多
The wetting heat and contact angle of sixteen coal samples were determined and the slurry-forming ability of coal were researched. Comparing the relationship of the wetting heat and contact angle with the slurry-formi...The wetting heat and contact angle of sixteen coal samples were determined and the slurry-forming ability of coal were researched. Comparing the relationship of the wetting heat and contact angle with the slurry-forming ability or coal, the auther has found out that the slurry-forming ability of coal can be measured by the wetting heat.展开更多
Wetting film thinning measurement was introduced to clarify the wettability and floatability of solid surfaces with varying roughness. The wettability was quantified using the contact angle measurement combined with t...Wetting film thinning measurement was introduced to clarify the wettability and floatability of solid surfaces with varying roughness. The wettability was quantified using the contact angle measurement combined with the dynamic force microbalance test between solid surfaces and water droplets, while the floatability was investigated by the bubble-solid surface dynamic attachment observation and the induction time measurement. The results show that the water contact angles reduce(14.53°, 12.74°, and 6.71°)with the increase of glass surface roughness, while the water droplet-glass adhesion forces intensify(11.1, 19.1 and 19.2 μN) owing to the stable wetting film. The distortion of the contact surface and the Wenzel state are the causes. In contrast, the hydrophobized surfaces have the growing apparent contact angles(38.08°, 69.81°, and 81.01°), declining adhesion strength and shortening induction time(863, 352and 12 ms) along with the increasing surface roughness. The weak wettability and fine floatability on the rough hydrophobized surface is reflected in the fast wetting film drainage dynamics and three-phase contact formation, which may be attributed to the wetting film with short diameter on tiny rough nubs and the entrapped air in the grooves as a bridge between the bulk bubble and the solid surface.展开更多
16 samples of Chinese coal were tested for their flotation and hydropbilic properties. The two physico-chemical parameters, wetting heat and contact angle were compared as they were used in evaluating the flotability ...16 samples of Chinese coal were tested for their flotation and hydropbilic properties. The two physico-chemical parameters, wetting heat and contact angle were compared as they were used in evaluating the flotability of coal. The result shows that the wetting heat is in good accordance with flotability and is better than contact angle in reflecting the flotability. A new idea of classifying the flotability using wetting heat is put forward.展开更多
The contact angle phenomena and wetting behavior of fatty acids,alcohols and ester used as additives in lubricants onto the rolled copper foil(RCF)surface were studied by the static sessile drop method.Semi-empirical ...The contact angle phenomena and wetting behavior of fatty acids,alcohols and ester used as additives in lubricants onto the rolled copper foil(RCF)surface were studied by the static sessile drop method.Semi-empirical quantum-chemical method studies on the contact angle of these compounds onto surface using several structural parameters were carried out.Molecular refractivity as well as several structural parameters were adopted in the development of quantitative structure-property relationships(QSPR)using genetic function approximation(GFA)statistical analysis method.The results show that quantum parameters are a better choice when predicting the contact angle and wettability of lubricants onto the RCF surface.Contact angle of the compounds serves as a function of their viscosity,interfacial tension,and physicochemical parameters.Alog P,molecular refractivity,molecular flexibility,total molecular mass,solvent surface area,element count,total energy and dipole are the most sensitive ones among the major contributing parameters.Notably,studies of lubricants on the RCF surfaces allow wetting theories to be tested down to the microcosmic scale,which can bring about new insight to predict wettability of lubricants onto RCF surface.展开更多
Wetting states and processes attract plenty of interest of scientific and industrial societies. Air entrainment, i.e.,wetting failure, on smooth plate in wetting process has been investigated carefully before. Liquid ...Wetting states and processes attract plenty of interest of scientific and industrial societies. Air entrainment, i.e.,wetting failure, on smooth plate in wetting process has been investigated carefully before. Liquid bath entries of "rough"silicon wafers are studied experimentally in the present work, and the air entrainment condition is analyzed specially with the lubrication theory. The roughness effects on the moving contact lines are therefore explored. The contact line pinning is found to be the main reason for the dynamically enhanced hydrophobicity of rough surface, which implies an effective microscopic contact angle of θ_e = θ_Y + 90° where θY is the Young's contact angle of the material. Our results suggest that the solid surfaces can be considered as hydrophobic ones for a wide range of dynamic process, since they are normally rough. The work can also be considered as a starting point for investigating the high-speed advancing of moving contact line on rough surfaces.展开更多
The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on t...The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on the pillar sidewall,which makes the droplet highly unstable and undermines the overall hydrophobic performance of the pillar. In this work,molecular dynamics(MD) simulation of the simple liquid at a single stripe pillar edge defect is performed to characterize the droplet's critical wetting properties considering the evaporation–condensation effect. From the simulation results, the droplets slide down from the edge defect with a volume smaller than the critical value, which is attributed to the existence of the wetting layer on the stripe pillar sidewall. Besides, the analytical study of the pillar sidewall and wetting layer potential field distribution manifests the relation between the simulation parameters and the degree of the droplet pre-wetting, which agrees well with the MD simulation results.展开更多
Tile expressions of interface flee energy （IFE） of composite droplets with meniscal liquid-air interlhce in metastable state on nlicro/nano textured snrfaces were formulated. Then tile parameters to describe the men...Tile expressions of interface flee energy （IFE） of composite droplets with meniscal liquid-air interlhce in metastable state on nlicro/nano textured snrfaces were formulated. Then tile parameters to describe the meniscus were determined based on the principle of minimtun 1FE. Furthermore, the IFE barriers and the necessary and sufficient conditions of drop wetting transition fl＇om Cassie to Wenzel were analyzed and the corresponding criteria were lk^rmulated. The results show that the liquid-air interface below a composite droplet is fiat when the post pitches are relatively small, but in a shape of curved meniscus when the piteches are comparatively large and the curvature depends on structural parameters. The angle between meniscus and pillar wall is just equal to the supplementary angle of intrinsic contact angle of post material. The calculations also illustrate that Cassie droplets will transform to Wenzel state when post pitch is large enough or when drop volume is sufficiently small. The opposite transition from Wenzel to Cassie state, however, is unable to take place spontaneously because the energy barrier is always positive. Finally, the calculation results of this model are well consistent with tile experimental obserwttions in literatures for the wetting transition of droplets from Cassie to Wenzel state.展开更多
MXenes are a class of 2D nanomaterials with exceptional tailormade properties such as mechano-ceramic nature,rich chemistry,and hydrophilicity,to name a few.However,one of the most challenging issues in any composite/...MXenes are a class of 2D nanomaterials with exceptional tailormade properties such as mechano-ceramic nature,rich chemistry,and hydrophilicity,to name a few.However,one of the most challenging issues in any composite/hybrid system is the interfacial wetting.Having a superior integrity of a given composite system is a direct consequence of the proper wettability.While wetting is a fundamental feature,dictating many physical and chemical attributes,most of the common nanomaterials possesses poor affinity due to hydrophobic nature,making them hard to be easily dispersed in a given composite.Thanks to low contact angle,MXenes can offer themselves as an ideal candidate for manufacturing different nano-hybrid structures.Herein this review,it is aimed to particularly study the wettability of MXenes.In terms of the layout of the present study,MXenes are first briefly introduced,and then,the wettability phenomenon is discussed in detail.Upon reviewing the sporadic research efforts conducted to date,a particular attention is paid on the current challenges and research pitfalls to light up the future perspectives.It is strongly believed that taking the advantage of MXene’s rich hydrophilic surface may have a revolutionizing role in the fabrication of advanced materials with exceptional features.展开更多
Nanocrystalline Cu film with a mirror surface finishing is prepared by the electric brush-plating technique. The as- prepared Cu film exhibits a superhydrophilic behavior with an apparent water contact angle smaller t...Nanocrystalline Cu film with a mirror surface finishing is prepared by the electric brush-plating technique. The as- prepared Cu film exhibits a superhydrophilic behavior with an apparent water contact angle smaller than 10°. A subsequent increase in the water contact angle and a final wetting transition from inherent hydrophilicity with water contact angle smaller than 90° to apparent hydrophobicity with water contact angle larger than 90° are observed when the Cu film is subjected to natural aging. Analysis based on the measurement of hardness with nanoindentation and the theory of the bond-order-length-strength correlation reveals that this wetting variation on the Cu film is attributed to the relaxation of residual stress generated during brush-plating deposition and a surface hydrophobization role associated with the broken bond polarization induced by surface nanostructure.展开更多
Textured silicon （Si） substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanize...Textured silicon （Si） substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanized by self-assembly octadecyl- trichlorosilane （OTS） film. The systematic water contact angle （CA） measurements and micro/nanoscale hierarchical rough structure models are used to analyze the wetting behaviors of original and silanized textured Si substrates each as a function of pillar interval-to-width ratio. On the original textured Si substrate with hydrophilic pillars, the water droplet possesses a larger apparent CAs （〉 90~） and contact angle hysteresis （CAH）, induced by the hierarchical roughness of microscale pil- lar arrays and nanoscale pit-like roughness. However, the silanized textured substrate shows superhydrophobicity induced by the low free energy OTS overcoat and the hierarchical roughness of microscale pillar arrays, and nanoscale island-like roughness. The largest apparent CA on the superhydrophobic surface is 169.8~. In addition, the wetting transition of a gently deposited water droplet is observed on the original textured substrate with pillar interval-to-width ratio increasing. Furthermore, the wetting state transition is analyzed by thermodynamic approach with the consideration of the CAH effect. The results indicate that the wetting state changed from a Cassie state to a pseudo-Wenzel during the transition.展开更多
Based on the fact that rubbed groove patterns also affect the anchoring of liquid crystals at substrates,a quartic coupling is included in constructing the surface energy for a liquid crystal cell.The phase diagram an...Based on the fact that rubbed groove patterns also affect the anchoring of liquid crystals at substrates,a quartic coupling is included in constructing the surface energy for a liquid crystal cell.The phase diagram and the wetting behaviors of the liquid crystal cell,bounded by surfactant-laden interfaces in a magnetic field perpendicular to the substrate are discussed by taking the quartic coupling into account.The nematic order increases at the surface while it decreases in the bulk as a result of the introduction of quartic substrate-liquid crystal coupling,indicating that the groove anchoring makes the liquid crystal molecules align more orderly near the substrate than away from it.This causes a different wetting behavior：complete wetting.展开更多
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 rectificatio...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.展开更多
Our research focused on the analy sis of concrete deterioration mechan ism under the coup ling effects of flexural load,cy clic wetting and dry ing, and sulfate. The relative dy namic modulus of elasticity of a corrod...Our research focused on the analy sis of concrete deterioration mechan ism under the coup ling effects of flexural load,cy clic wetting and dry ing, and sulfate. The relative dy namic modulus of elasticity of a corroded concrete samp le was tested, and scannin g electron microscop e was used to observe the microstructure of concrete under the coup ling effects of flexural load,cy clic wetting and dry ing, and sulf ate. Results manif ested that flexur al load and cy clic wetting and dry ing durin g the concrete service chan ged the corrosion p rocess of the sulfate mediu m in con crete and enh anced the deterioration of con crete p erforman ce.Furthermore, the influencin g p atterns of strength grade of concr ete, mass concentration of sulfate solution, and mineral admixtures on the degree of concrete deterioration were identified.展开更多
Current-voltage electrical characteristics of Er silicide/Si（001） nanocontacts are measured in situ in a scanning tunneling microscopy system. Introduced as a new technique to suppress surface leakage conduction on...Current-voltage electrical characteristics of Er silicide/Si（001） nanocontacts are measured in situ in a scanning tunneling microscopy system. Introduced as a new technique to suppress surface leakage conduction on Si（001）,a silver wetting layer is evaporated onto the substrate surface kept at room temperature with Er Si2 nanoislands already existing. The effects of the silver layer on the current-voltage characteristics of nanocontacts are discussed.Our experimental results reveal that the silver layer at coverage of 0.4–0.7 monolayer can suppress effectively the current contribution from the surface conduction path. After the surface leakage path of nanocontacts is obstructed, the ideality factor and the Schottky barrier height are determined using the thermionic emission theory, about 2 and 0.5 eV, respectively. The approach adopted here could shed light on the intrinsic transport properties of metal-semiconductor nanocontacts.展开更多
Integrated data and energy transfer(IDET)enables the electromagnetic waves to transmit wireless energy at the same time of data delivery for lowpower devices.In this paper,an energy harvesting modulation(EHM)assisted ...Integrated data and energy transfer(IDET)enables the electromagnetic waves to transmit wireless energy at the same time of data delivery for lowpower devices.In this paper,an energy harvesting modulation(EHM)assisted multi-user IDET system is studied,where all the received signals at the users are exploited for energy harvesting without the degradation of wireless data transfer(WDT)performance.The joint IDET performance is then analysed theoretically by conceiving a practical time-dependent wireless channel.With the aid of the AO based algorithm,the average effective data rate among users are maximized by ensuring the BER and the wireless energy transfer(WET)performance.Simulation results validate and evaluate the IDET performance of the EHM assisted system,which also demonstrates that the optimal number of user clusters and IDET time slots should be allocated,in order to improve the WET and WDT performance.展开更多
基金Financial support for this work,provided by the Science and Technology Project of the Education Department of Shandong Province(No.J08LC12),
文摘In this study,FTIR and XPS spectroscopy,specific surface area and pore size analyses,wetting and other experimental means have been applied to investigate respirable coal dust surface properties and wetting mechanism.The research shows that coal dust surface structures,chemical and element compositions are changed in the refining process of coal dust.Compared with large particle coal dust,respirable coal dust is a weak hydrophilic and strong hydrophobic substance.The reason:the smaller the particle size of coal dust,the more unsaturated its surface.The absorption of air is strong and it is easy to form an air film on coal dust surfaces. Coal dust contact with water is actually a compound contact of liquid in contact with a solid and gas in contact with a solid. The smaller the particle size,the larger the pore volume and the higher the degree of surface roughness,the larger the area of gas in contact with a solid and the worse the coal dust wettability.Another reason is that the changes in the composition of atoms on the dust surface and structures affect coal dust wettability.The results of this study establish a theoretical basis for the invention of effective reduced-dust technology.
文摘Influences of temperature and Sn-Cu droplet's composition on reactive wettings of Cu(100), Cu(110), and Cu(111) surfaces were analyzed, by using molecular dynamics(MD) calculations. As a result, the spreading on Cu(110)(Cu(100)) has the fastest(slowest) wetting kinetics. A higher temperature or a diluter Cu content in the Sn-Cu alloy droplet results in a higher wettability. Moreover, this work has addressed a theory for positioning the interface separating the liquidus and solidus alloys in the spreading film to confirm the hypothesis that the reactive wetting will come to the end when the interface saturates with the temperature-dependent solidus weight fraction of Cu.
基金supported by the National Natural Science Foundation of China(No.U2003125)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX21_2400)the Future Scientists Program of China University of Mining and Technology(No.2021WLKXJ034).
文摘The dynamic pore wetting plays an important role in the flotation of porous particle,such as coal,fly ash,gasification slag,etc.Water phase get into the pores and crevices on the surface and inside of the particles,creating a dense water layer that covers their surface and decreases their floatability.It is important to reduce the adverse impact of dynamic pore wetting on the flotation performance of porous particles.Thus,this review is to highlight the dynamic pore wetting behavior,and its role in the porous particle flotation as well as the proposed regulation methods to weaken the pore wetting.The characterization approaches of the dynamic pore wetting are discussed including the optical method for the capillary and the nuclear magnetic resonance(NMR)method for porous particles.The surface tension and viscosity of liquid significantly affect the pore wetting degree of porous particles during the 60 min wetting process.Pre-wetting time adjustment,pore compression,pore filling,and hydrophobic modifications are introduced to decrease the wetting percentage of pores in porous particles and further improve their flotation performance.This critical review will provide some guidance for studying the dynamic wetting behavior of pores and enhancing the floatability of porous particles.
基金partly supported by the National Natural Science Foundation of China (No.51404263)the National Natural Science Foundation of Jiangsu Province (No.BK20130203)+3 种基金the Coal Mine Joint Funds of the National Natural Science Foundation of China (No.51134023)the State Key Laboratory Cultivation Base for Gas Geology and Gas Control (No.WS2013A05)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)the independent study for State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology (No.SKLCRSM09X04)
文摘After gas drainage, the outburst seam is dry and, consequently, during subsequent mechanized mining, unwanted dust production is extensive. Because the hard dustfall typically has a small particle size it contains a high percentage of respirable dust. Considering these factors, this paper improved the efficiency of dustfall by reducing the surface tension of the liquid used as a wetting agent, then configuring five kinds of wetting agents by adopting various doses and types of surfactants, neutral inorganic salts and chemical additives, etc. After purchasing DA-85 and SRJ-1 wetting agent, the surface tension and critical micelle concentration of seven kinds of wetting agents were measured using the capillary rise method. Wetting agent A was confirmed to have the best comprehensive effect. The experiments were optimized by measuring and comparatively analyzing contact angles of pure water, SRJ-1 wetting agent and wetting agent A on the surface of different coal samples using a contact angle measurement instrument （HARKE- SPCA）. By comparative analysis, dust-proof effects of seam, dynamic pressure water infusion and high- pressure spray in the tunneling face at the Daning coal mine using pure water, wetting agent SRJ-1 and A, it was determined that after using wetting agent A, the average dust concentration in the place of the mining machine driver, 10 m and 110 m away from the tunneling front is approximately 300 rag/ m^3, 240 mg/m^3 and 100 mg/m^3, respectively, This practice increased the dust-proof efficiency dramati- cally and achieved a good comprehensive dust-proof effect.
基金supported by the National Natural Science Foundation of China(Nos.U1532260,11674345,and 11504032)Key Research Program of Chinese Academy of Sciences(Nos.KJZD-EW-M03 and QYZDJ-SSW-SLH019)+3 种基金Youth Innovation Promotion Association CAS(Grant Number 2014233)Shanghai Supercomputer Center of ChinaComputer Network Information Center of Chinese Academy of SciencesSpecial Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund
文摘Water molecules could form a liquid droplet on the water monolayer on a specific solid surface, which has been referred to as ‘‘ordered water monolayer that does not completely wet water'' at room temperature. In contrast to the water molecules, the family of alcohol molecules has the same OH polar head and various lengths of their hydrophobic nonpolar tail; the length of the hydrophobic tail can affect the hydrophobic effect. In this study, using molecular dynamics simulations, we investigated the wetting behaviors of methanol, ethanol, and propanol molecules adsorbed on a SiO_2 surface. The results showed that the methanol, ethanol, and propanol molecules could form an ordered monolayer on the SiO_2 surface and a droplet on top of this monolayer, with different contact angles. The differences in the contact angles were attributed to the differences in the interactions between the alcohol monolayer and droplet.
文摘The wetting heat and contact angle of sixteen coal samples were determined and the slurry-forming ability of coal were researched. Comparing the relationship of the wetting heat and contact angle with the slurry-forming ability or coal, the auther has found out that the slurry-forming ability of coal can be measured by the wetting heat.
基金supported by the National Nature Science Foundation of China(Nos.51904300,21978318,51920105007,and 52274278)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX21_2403).
文摘Wetting film thinning measurement was introduced to clarify the wettability and floatability of solid surfaces with varying roughness. The wettability was quantified using the contact angle measurement combined with the dynamic force microbalance test between solid surfaces and water droplets, while the floatability was investigated by the bubble-solid surface dynamic attachment observation and the induction time measurement. The results show that the water contact angles reduce(14.53°, 12.74°, and 6.71°)with the increase of glass surface roughness, while the water droplet-glass adhesion forces intensify(11.1, 19.1 and 19.2 μN) owing to the stable wetting film. The distortion of the contact surface and the Wenzel state are the causes. In contrast, the hydrophobized surfaces have the growing apparent contact angles(38.08°, 69.81°, and 81.01°), declining adhesion strength and shortening induction time(863, 352and 12 ms) along with the increasing surface roughness. The weak wettability and fine floatability on the rough hydrophobized surface is reflected in the fast wetting film drainage dynamics and three-phase contact formation, which may be attributed to the wetting film with short diameter on tiny rough nubs and the entrapped air in the grooves as a bridge between the bulk bubble and the solid surface.
文摘16 samples of Chinese coal were tested for their flotation and hydropbilic properties. The two physico-chemical parameters, wetting heat and contact angle were compared as they were used in evaluating the flotability of coal. The result shows that the wetting heat is in good accordance with flotability and is better than contact angle in reflecting the flotability. A new idea of classifying the flotability using wetting heat is put forward.
基金the financial assistance provided by the Introducing the Talent Research Start-up Fund(No.YKJ201706)the National Natural Science Foundation of China(No.51474025)
文摘The contact angle phenomena and wetting behavior of fatty acids,alcohols and ester used as additives in lubricants onto the rolled copper foil(RCF)surface were studied by the static sessile drop method.Semi-empirical quantum-chemical method studies on the contact angle of these compounds onto surface using several structural parameters were carried out.Molecular refractivity as well as several structural parameters were adopted in the development of quantitative structure-property relationships(QSPR)using genetic function approximation(GFA)statistical analysis method.The results show that quantum parameters are a better choice when predicting the contact angle and wettability of lubricants onto the RCF surface.Contact angle of the compounds serves as a function of their viscosity,interfacial tension,and physicochemical parameters.Alog P,molecular refractivity,molecular flexibility,total molecular mass,solvent surface area,element count,total energy and dipole are the most sensitive ones among the major contributing parameters.Notably,studies of lubricants on the RCF surfaces allow wetting theories to be tested down to the microcosmic scale,which can bring about new insight to predict wettability of lubricants onto RCF surface.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11472220 and 11872315)
文摘Wetting states and processes attract plenty of interest of scientific and industrial societies. Air entrainment, i.e.,wetting failure, on smooth plate in wetting process has been investigated carefully before. Liquid bath entries of "rough"silicon wafers are studied experimentally in the present work, and the air entrainment condition is analyzed specially with the lubrication theory. The roughness effects on the moving contact lines are therefore explored. The contact line pinning is found to be the main reason for the dynamically enhanced hydrophobicity of rough surface, which implies an effective microscopic contact angle of θ_e = θ_Y + 90° where θY is the Young's contact angle of the material. Our results suggest that the solid surfaces can be considered as hydrophobic ones for a wide range of dynamic process, since they are normally rough. The work can also be considered as a starting point for investigating the high-speed advancing of moving contact line on rough surfaces.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0202401)the National Natural Science Foundation of China(Grant No.61705066)the Fundamental Research Funds for the Central Universities,China(Grant No.2017MS028)
文摘The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on the pillar sidewall,which makes the droplet highly unstable and undermines the overall hydrophobic performance of the pillar. In this work,molecular dynamics(MD) simulation of the simple liquid at a single stripe pillar edge defect is performed to characterize the droplet's critical wetting properties considering the evaporation–condensation effect. From the simulation results, the droplets slide down from the edge defect with a volume smaller than the critical value, which is attributed to the existence of the wetting layer on the stripe pillar sidewall. Besides, the analytical study of the pillar sidewall and wetting layer potential field distribution manifests the relation between the simulation parameters and the degree of the droplet pre-wetting, which agrees well with the MD simulation results.
基金Project supported by the National Natural Science Foundation of China(Grant No.21676041)
文摘Tile expressions of interface flee energy （IFE） of composite droplets with meniscal liquid-air interlhce in metastable state on nlicro/nano textured snrfaces were formulated. Then tile parameters to describe the meniscus were determined based on the principle of minimtun 1FE. Furthermore, the IFE barriers and the necessary and sufficient conditions of drop wetting transition fl＇om Cassie to Wenzel were analyzed and the corresponding criteria were lk^rmulated. The results show that the liquid-air interface below a composite droplet is fiat when the post pitches are relatively small, but in a shape of curved meniscus when the piteches are comparatively large and the curvature depends on structural parameters. The angle between meniscus and pillar wall is just equal to the supplementary angle of intrinsic contact angle of post material. The calculations also illustrate that Cassie droplets will transform to Wenzel state when post pitch is large enough or when drop volume is sufficiently small. The opposite transition from Wenzel to Cassie state, however, is unable to take place spontaneously because the energy barrier is always positive. Finally, the calculation results of this model are well consistent with tile experimental obserwttions in literatures for the wetting transition of droplets from Cassie to Wenzel state.
文摘MXenes are a class of 2D nanomaterials with exceptional tailormade properties such as mechano-ceramic nature,rich chemistry,and hydrophilicity,to name a few.However,one of the most challenging issues in any composite/hybrid system is the interfacial wetting.Having a superior integrity of a given composite system is a direct consequence of the proper wettability.While wetting is a fundamental feature,dictating many physical and chemical attributes,most of the common nanomaterials possesses poor affinity due to hydrophobic nature,making them hard to be easily dispersed in a given composite.Thanks to low contact angle,MXenes can offer themselves as an ideal candidate for manufacturing different nano-hybrid structures.Herein this review,it is aimed to particularly study the wettability of MXenes.In terms of the layout of the present study,MXenes are first briefly introduced,and then,the wettability phenomenon is discussed in detail.Upon reviewing the sporadic research efforts conducted to date,a particular attention is paid on the current challenges and research pitfalls to light up the future perspectives.It is strongly believed that taking the advantage of MXene’s rich hydrophilic surface may have a revolutionizing role in the fabrication of advanced materials with exceptional features.
基金Project supported by the National Natural Science Foundations of China(Grant No.51371089)the Foundation of National Key Basic Research and Development Program of China(Grant No.2010CB 631001)
文摘Nanocrystalline Cu film with a mirror surface finishing is prepared by the electric brush-plating technique. The as- prepared Cu film exhibits a superhydrophilic behavior with an apparent water contact angle smaller than 10°. A subsequent increase in the water contact angle and a final wetting transition from inherent hydrophilicity with water contact angle smaller than 90° to apparent hydrophobicity with water contact angle larger than 90° are observed when the Cu film is subjected to natural aging. Analysis based on the measurement of hardness with nanoindentation and the theory of the bond-order-length-strength correlation reveals that this wetting variation on the Cu film is attributed to the relaxation of residual stress generated during brush-plating deposition and a surface hydrophobization role associated with the broken bond polarization induced by surface nanostructure.
基金Project supported by the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No.NCET-09-0211)the Fundamental Research Funds for the Central Universities (Grant Nos.2012YJS105 and M13JB00240)
文摘Textured silicon （Si） substrates decorated with regular microscale square pillar arrays of nearly the same side length, height, but different intervals are fabricated by inductively coupled plasma, and then silanized by self-assembly octadecyl- trichlorosilane （OTS） film. The systematic water contact angle （CA） measurements and micro/nanoscale hierarchical rough structure models are used to analyze the wetting behaviors of original and silanized textured Si substrates each as a function of pillar interval-to-width ratio. On the original textured Si substrate with hydrophilic pillars, the water droplet possesses a larger apparent CAs （〉 90~） and contact angle hysteresis （CAH）, induced by the hierarchical roughness of microscale pil- lar arrays and nanoscale pit-like roughness. However, the silanized textured substrate shows superhydrophobicity induced by the low free energy OTS overcoat and the hierarchical roughness of microscale pillar arrays, and nanoscale island-like roughness. The largest apparent CA on the superhydrophobic surface is 169.8~. In addition, the wetting transition of a gently deposited water droplet is observed on the original textured substrate with pillar interval-to-width ratio increasing. Furthermore, the wetting state transition is analyzed by thermodynamic approach with the consideration of the CAH effect. The results indicate that the wetting state changed from a Cassie state to a pseudo-Wenzel during the transition.
基金supported by the National Natural Science Foundation of China(Grant No.11374243)
文摘Based on the fact that rubbed groove patterns also affect the anchoring of liquid crystals at substrates,a quartic coupling is included in constructing the surface energy for a liquid crystal cell.The phase diagram and the wetting behaviors of the liquid crystal cell,bounded by surfactant-laden interfaces in a magnetic field perpendicular to the substrate are discussed by taking the quartic coupling into account.The nematic order increases at the surface while it decreases in the bulk as a result of the introduction of quartic substrate-liquid crystal coupling,indicating that the groove anchoring makes the liquid crystal molecules align more orderly near the substrate than away from it.This causes a different wetting behavior：complete wetting.
基金the National Natural Science Foundation of China(Grant No.51976002)the Beijing Nova Program of Science and Technology(Grant No.Z191100001119033)。
文摘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.
基金Funded by Fujian Education Department(Nos.JA11329 and JA12412)Quanzhou(Fujian)Techno logy Research and Development Program(Nos.2013Z158,2013Z47,and 2010G7)
文摘Our research focused on the analy sis of concrete deterioration mechan ism under the coup ling effects of flexural load,cy clic wetting and dry ing, and sulfate. The relative dy namic modulus of elasticity of a corroded concrete samp le was tested, and scannin g electron microscop e was used to observe the microstructure of concrete under the coup ling effects of flexural load,cy clic wetting and dry ing, and sulf ate. Results manif ested that flexur al load and cy clic wetting and dry ing durin g the concrete service chan ged the corrosion p rocess of the sulfate mediu m in con crete and enh anced the deterioration of con crete p erforman ce.Furthermore, the influencin g p atterns of strength grade of concr ete, mass concentration of sulfate solution, and mineral admixtures on the degree of concrete deterioration were identified.
基金Supported by the National Natural Science Foundation of China under Grant No 11374058
文摘Current-voltage electrical characteristics of Er silicide/Si（001） nanocontacts are measured in situ in a scanning tunneling microscopy system. Introduced as a new technique to suppress surface leakage conduction on Si（001）,a silver wetting layer is evaporated onto the substrate surface kept at room temperature with Er Si2 nanoislands already existing. The effects of the silver layer on the current-voltage characteristics of nanocontacts are discussed.Our experimental results reveal that the silver layer at coverage of 0.4–0.7 monolayer can suppress effectively the current contribution from the surface conduction path. After the surface leakage path of nanocontacts is obstructed, the ideality factor and the Schottky barrier height are determined using the thermionic emission theory, about 2 and 0.5 eV, respectively. The approach adopted here could shed light on the intrinsic transport properties of metal-semiconductor nanocontacts.
基金supported in part by the MOST Major Research and Development Project(Grant No.2021YFB2900204)the National Natural Science Foundation of China(NSFC)(Grant No.62201123,No.62132004,No.61971102)+3 种基金China Postdoctoral Science Foundation(Grant No.2022TQ0056)in part by the financial support of the Sichuan Science and Technology Program(Grant No.2022YFH0022)Sichuan Major R&D Project(Grant No.22QYCX0168)the Municipal Government of Quzhou(Grant No.2022D031)。
文摘Integrated data and energy transfer(IDET)enables the electromagnetic waves to transmit wireless energy at the same time of data delivery for lowpower devices.In this paper,an energy harvesting modulation(EHM)assisted multi-user IDET system is studied,where all the received signals at the users are exploited for energy harvesting without the degradation of wireless data transfer(WDT)performance.The joint IDET performance is then analysed theoretically by conceiving a practical time-dependent wireless channel.With the aid of the AO based algorithm,the average effective data rate among users are maximized by ensuring the BER and the wireless energy transfer(WET)performance.Simulation results validate and evaluate the IDET performance of the EHM assisted system,which also demonstrates that the optimal number of user clusters and IDET time slots should be allocated,in order to improve the WET and WDT performance.
