In this work, three-dimensional graphene foams (GFs) are synthesized and characterized by scanning electron micro- scope (SEM) and Raman spectroscopy. The SEM images indicate that after the growth of graphene, the...In this work, three-dimensional graphene foams (GFs) are synthesized and characterized by scanning electron micro- scope (SEM) and Raman spectroscopy. The SEM images indicate that after the growth of graphene, the graphene covers the surface of nickel (Ni) foam uniformly. Raman spectra show that the percentages of monolayer, bilayer, trilayer, and multilayer graphenes are - 58%, - 32%, - 8%, and ,.o 2%, respectively. The contact angle (CA) (-- 12°) of water droplet (3 p-L) on GF is found to be larger than that on Ni foam (,- 107°), indicating that graphenes have changed the surface wettability of the Ni foam. Meanwhile, the dynamic characteristics of CA of water droplet on GF are different from those on Ni foam. The mechanisms for different behaviors are discussed, which are attributed to volatilization and seepage of water droplets.展开更多
Membrane-based separation is a promising technology to eliminate water impurities from the oil phase.However,it remains a great challenge to separate water from highly emulsified viscous oil owing to the high stabilit...Membrane-based separation is a promising technology to eliminate water impurities from the oil phase.However,it remains a great challenge to separate water from highly emulsified viscous oil owing to the high stability of the water droplets in oil.Herein we report a surface wettability engineering on an alumina ceramic membrane to achieve an efficient separation of a water-in-oil(W/O)emulsion.Silanes with different carbon chain lengths and fluorinated status were introduced to endow the alumina membrane with different surface wettabilities.While all the modified membranes exhibited excellent separation of the W/O without Span 80(surfactant),the one with amphiphobic wettability and lowest surface energy failed to separate the Span 80 stabilized W/O.The presence of Span 80 reduced the interfacial tension of water droplets,making them easier to deform and penetrate the modified membrane with the lowest surface energy.It reveals that engineering proper surface wettability is the key to separating the oil and water phases.Besides,the modified membranes maintained decent separation performance and stability under long-term run separation of the emulsified W/O.展开更多
Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry (FTIR), 1H Nuclear magnetic resonance (1H-...Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry (FTIR), 1H Nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). The resulting copolymer was used to prepare poly(vinylidene fluoride) (PVDF) blend membranes via a phase inversion method. The effects of the copolymer on the polymorphism, surface wettability and zeta potential (0 of the blend membranes were investigated by ATR-FTIR, contact angle instrument and zeta potential analyzer. Scanning electron microscopy (SEM and SEM-EDS) was also applied to investigate the morphology and the surface element changes of the fabricated membranes. The results indicated that P(MMA-co-BVIm-Br) copolymer existed on the surface of the membrane which made the blend membrane have a positive surface during the experimental pH range. The copolymer was also in favor of the formation of βcrystal phase in PVDF membranes. The contact angle experiment indicated that P(MMA-co-BVIm-Br) copolymer could switch the wettability of the blend membranes from hydrophilic to hydrophobic by exchanging Br- anion with PF6-. Compared with pure PVDF membranes, the water flux and water recovery flux of the blend membranes were enhanced obviously. The results from the flux recovery ratio (FR) and total fouling ratio (Rt) all suggested that the blend membranes had good anti-fouling properties.展开更多
Surface wettability is important to design biointerfaces and functional biomaterials in various biological applications. However,to date, it remains some confusions about how cells would response to the surfaces with ...Surface wettability is important to design biointerfaces and functional biomaterials in various biological applications. However,to date, it remains some confusions about how cells would response to the surfaces with different wettabilities. Herein,we systematically explore the adhesive spectra of cells to the surface with wettability gradient from superhydrophilicity to superhydrophobicity, clarifying the effect of wettability on cell adhesion. We envision that this study may provide valuable information for the design of biomedical implants with controllable cell adhesion, such as neural interface devices and flexible implant.展开更多
Based on 1971-2005 monthly mean maximum/minimum temperature,wind speed,relative humidity,sunshine duration,and precipitation data at 25 stations over the Tibetan Plateau,a study of the largest potential evapotranspira...Based on 1971-2005 monthly mean maximum/minimum temperature,wind speed,relative humidity,sunshine duration,and precipitation data at 25 stations over the Tibetan Plateau,a study of the largest potential evapotranspiration(LPE) is performed by using the Penman-Monteith model.The surface wettability index(SWI) is calculated and examined,together with its space distribution,interannual and seasonal variations,as well as associated causes.The results suggest that the annual area rainfall exhibits a pronounced increasing trend at 15.0 mm per decade;the annual LPE shows a different-degree decrease at-4.6—-71.6 mm/10 yr.In the southwestern Ngari prefecture and Nyalam county,the annual SWI displays insignificant decline trends compared to increasing trends in other areas of Tibet(0.02-0.09 per decade).For Tibet,on average,the SWI experiences a noticeable rise at 0.04/10 yr,particularly in 1981-2005.On a seasonal basis,the SWI shows increasing trends,especially in summer.In the 1970s-1980s,the interannual variation is characterized mainly by lower temperature and lower humidity.From the 1990s,air temperature keeps on rising,leading to an appreciable increase in SWI,displayed as a type of warm and humid climate.The salient increases(decrease) of precipitation and relative humidity(mean temperature daily range) are the principal causes of the greatly enhanced SWI in the region.The pronounced decrease in mean wind and sunshine duration also plays an active role.展开更多
The chemical composition obviously affects the surface wettability of a three-dimensional(3D)graphene material apart from its surface energy and microstructure.In the hydrothermal preparation,the heteroatom doping cha...The chemical composition obviously affects the surface wettability of a three-dimensional(3D)graphene material apart from its surface energy and microstructure.In the hydrothermal preparation,the heteroatom doping changes the chemical composition and wettability of the 3D graphene material.To realize the controllable surface wettability of graphene materials,aminobenzene sulfonic acid(ABSA)was selected as a typical doping agent for the preparation of nitrogen and sulfur co-doped 3D graphene foam(SNGF)using a hydrothermal method.Different from using o-ABSA or p-ABSA as the dopant,SNGF with tunable surface wettability is obtained only when m-ABSA is used.This result indicates that the substituent position of-SO3H group in the benzene ring of ABSA is rather important for the tunable wettability.This work provides some theo retical foundations for dopant selection and some new insights in manipulating the properties of 3D graphene foams by adjusting the configuration of dopants.展开更多
Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system need...Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system needs to be designed.However,with the trend of miniaturization,the heat transfer performance of LHPs degrades rapidly due to the significant increase of working fluid backflow resistance.This work aims to propose an effective solution to this problem.In this work,the surface wettability gradient(SWG)is introduced into the ultra-thin LHP,and the influence of SWG on mass and heat transfer performance is studied comprehensively by using a transient three-dimensional numerical model.It is observed that the SWG can significantly increase the vapor-liquid circulation efficiency and improve heat transfer performance.Numerical experiments have been performed to compare the two kinds of LHPs with and without SWG.At the heat load of 4–6 W,the start-up time for LHP with SWG is shortened by 11.5%and the thermal resistance is reduced by about 44.3%,compared with the LHP without SWG.This work provides a solution for the performance-degradation problem caused by miniaturization,as a numerical reference for experiments.展开更多
Droplet controllable manipulation over a wide temperature range has promising applications in microelectronic heat dissipation, inkjet printing, and high temperature microfluidic system. However, the fabrication of a ...Droplet controllable manipulation over a wide temperature range has promising applications in microelectronic heat dissipation, inkjet printing, and high temperature microfluidic system. However, the fabrication of a platform for controllable droplet manipulation using the methods commonly used in industry remains a tremendously challenge. The popular method of controlling droplets is highly dependent on external energy input and has relatively poor controllability in terms of droplet motion behaviors and manipulation environment, such as distance, velocity, direction and a wide temperature range. Here, we report a facile and industrially applicable method for preparing Al superhydrophobic (S-phobic) surfaces, which enables controlled droplet bouncing, evaporation, and transport over a wide temperature range. Systematic mechanistic studies are also investigated. Extreme wettability surfaces were prepared on Al substrate by a composite process of electrochemical mask etching and micro-milling. To investigate the evaporation process and thermal coupling characteristics, controlled evaporation and controlled bouncing of droplet in a wide temperature range were conducted. Based on the evaporation regulation and bouncing mechanism of droplets on an extreme wettability surface, by using Laplace pressure gradients and temperature gradients, we realized controlled transport of droplets with confluence, split-flow, and gravity-resistant transport over a wide temperature range, offering a potential platform for a series of applications, such as new drug candidates and water collection.展开更多
We used silane coupling agents to improve the bonding ability between wheat straw particles and UF resin, and investigated surface properties (wettability and surface roughness) and hardness of parti-cleboard made f...We used silane coupling agents to improve the bonding ability between wheat straw particles and UF resin, and investigated surface properties (wettability and surface roughness) and hardness of parti-cleboard made from UF-bonded wheat straw (Triticum aestivum L.) combined with poplar wood as affected by silane coupling agent content and straw/poplar wood particle ratios. We manufactured one-layered particleboard panels at four different ratios of straw to poplar wood par-ticles (0%, 15%, 30% and 45% wheat straw) and silane coupling agent content at three levels of 0, 5% and 10%. Roughness measurements, average roughness (Ra), mean peak-to-valley height (Rz), and root mean square roughness (Rq) were measured on unsanded samples by using a fine stylus tracing technique. We obtained contact angle measurements by using a goniometer connected to a digital camera and computer sys-tem. Boards containing greater amounts of poplar particles had superior hardness compared to control samples and had lower wettability. Panels made with higher amounts of silane had lower Rq values.展开更多
Marine propellers are important propulsion devices for both surface ships and underwater vehicles.Increasingly severe environmental problems have required further performance enhancement for propellers.Nowadays,tradit...Marine propellers are important propulsion devices for both surface ships and underwater vehicles.Increasingly severe environmental problems have required further performance enhancement for propellers.Nowadays,traditional methods to improve propeller performances through geometrical and structural optimizations have been extensively investigated,while the underlying mechanisms of the effects of surface and interface properties on marine propellers are still far from being fully understood.This paper presented a comprehensive review of recent advances in the effects of surface and interface properties,such as surface roughness and surface wettability,on marine propellers with an emphasis on the significant improvements in both hydrodynamic and cavitation performances,hoping to arouse more in-depth investigations in the field of surface/interface science and technologies on marine propellers,and also promote the state-of-the-art technologies,such as superlubricity technology,into practical applications.展开更多
To improve the controllability of the wall-wetting process after the fuel spray-wall impingement in internal combustion engines,the methods of laser etching,chemical etching and surface free energy modification are us...To improve the controllability of the wall-wetting process after the fuel spray-wall impingement in internal combustion engines,the methods of laser etching,chemical etching and surface free energy modification are used to prepare biomimetic structured surfaces with different wettability.The impingement processes of diesel and n-butanol sprays on the walls under different conditions are experimentally investigated.As the surface oleophilicity increases,the spreading radius of wall-impinging sprays decreases.At about 5 s after the fuel injections,the fuel spray droplets hit the walls for the first time,and the secondary breakup and rebound occur.The mixture concentrations of different fuels hitting the various walls reach the peak value.Under a higher surface temperature,the peak value of the mixture concentration is mainly related to the heat flux to the fuel droplets in different boiling regimes from the metal surfaces.The concentration of the air–fuel mixture in the near wall region increases with increasing surface oleophilicity,increasing wall temperature and decreasing ambient pressure.Compared with diesel,n-butanol presents a higher air–fuel mixture concentration in the near wall region.展开更多
Using molecular dynamics simulations, we have revealed a novel wetting phenomenon with a droplet on composite structures formed by embedded water into(111) surface of β-cristobalite hydroxylated silica. This can be a...Using molecular dynamics simulations, we have revealed a novel wetting phenomenon with a droplet on composite structures formed by embedded water into(111) surface of β-cristobalite hydroxylated silica. This can be attributed to the formation of a composite structure composed of embedded water molecules and the surface hydroxyl(–OH) groups,which reduces the number of hydrogen bonds between the composite structure and the water droplet above the composite structure. Interestingly, a small uniform strain(±3%) applied to the crystal lattice of the hydroxylated silica surface can result in a notable change of the contact angles(> 40°) on the surface. The finding provides new insights into the correlation between the molecular-scale interfacial water structures and the macroscopic wettability of the hydroxylated silica surface.展开更多
Guar gum and its derivatives have been the most commonly used polymers to increase the viscosity of fracture fluids.Ceramic proppants are vital products for enhancing oil and gas well productivity in low-permeability ...Guar gum and its derivatives have been the most commonly used polymers to increase the viscosity of fracture fluids.Ceramic proppants are vital products for enhancing oil and gas well productivity in low-permeability reservoirs.In the last several decades,abundant studies have been found in the investigation of proppant size,shape,compositions on the fracture conductivity.However,few types of research can be found to study the proppant wettability effect on the oil and gas flow efficiency.In our research,eight experiments were conducted using traditional guar gum fracturing fluid.Results of this work indicated that ceramic proppant promotes oil flow efficiency from sandstone core samples to proppant packs and thus should promote oil well productivity.The mechanism behind this phenomenon is believed to be the formation of oil flow channels across the fracture face due to the imbibition of oil in the core onto the oil-wet surface of the proppant,promoting oil flow from the core to the fracture.After guar gum was added the results inverted,this phenomenon for water-wet proppant is believed to be increased by the viscosity of fracture fluids which increased the viscosity of water,promoting oil flow from the core to the fracture.Nevertheless,the stimulation effect of oil-wet proppant on oil flow efficiency can be reduced by the presence of guar gum solution.Inside the proppant matrix filled with guar gum fracturing fluid,oil can be blocked inside the proppant matrix as a discontinuous phase while the aqueous phase can be easily mixed with the guar gum fluid and then be transferred out.展开更多
Directional fluid transport is of significan</span><span style="font-family:Verdana;">ce</span><span style="font-family:Verdana;"> to many physical processes in nature. How ...Directional fluid transport is of significan</span><span style="font-family:Verdana;">ce</span><span style="font-family:Verdana;"> to many physical processes in nature. How to manipulate this process by man-made material is still a key challenge to scientists. In this study, Janus fabric was constructed by electrospinning a layer of polyvinylidene fluoride (PVDF) nanofibers on woven cotton or gauze. The chemical composition, morphology and surface wettability of two sides of Janus fabric were characterized by infrared spectroscopy, scanning electron microscope (SEM) and contact angle measurement. By controlling the PVDF electrospinning time, the maximum hydrostatic pressure of Janus fabric with different PVDF thickness was measured. It was found that PVDF/gauze is more favorable for unidirectional water transportation, and the moisture also can transfer from hydrophobic side to hydrophilic side. With the advantages of facile preparation, low-cost and one-way water/moisture transportation, the Janus fabric prepared in this study can be applied for water separation, humidity transfer and water collection from the air.展开更多
We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides...We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy.展开更多
The wettability of catalyst plays an important role in regulating catalytic performance in heterogenous catalysis because the microenvironment around the catalytic sites directly determines the mass transfer process o...The wettability of catalyst plays an important role in regulating catalytic performance in heterogenous catalysis because the microenvironment around the catalytic sites directly determines the mass transfer process of reactants.Inspired by gas trapped on the surface of subaquatic spiders,amphiphilic micro-organohydrogels with tunable surface wettabilities were developed by anchoring various alkane chains onto a poly(2-(dimethylamino)ethyl methacrylate)(p(DMAEMA))hydrophilic microgel network.Palladium nanoparticles(Pd NPs)were encapsulated in amphiphilic microgels(amphiphilic Pd@M)to catalyze hydrogenation reaction,achieving higher activities than pristine monohydrophilic Pd@M composite.The underwater oleophilicity and aerophilicity of Pd@M composites were quantified by oil/gas adhesion measurements and computational simulations.The higher amphiphilic catalytic activities are attributed to the formation of a gas-oil-solid reaction interface on the catalyst surfaces,allowing rapid transport of H2 and organic substrates through water to the Pd catalytic sites.Additionally,amphiphilic Pd@M composites also exhibit more superior catalytic performance in multi-substrates reaction.展开更多
Droplet impacting on the stainless steel wire mesh is very common in chemical devices,like a rotating packed bed.Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion per...Droplet impacting on the stainless steel wire mesh is very common in chemical devices,like a rotating packed bed.Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion performance.However,the effect of surface wettability on the impaction phenomena at microscale such as liquid film is still unknown.In this work,the dynamic behavior of liquid film on the surface of wire mesh was analyzed by computational fluid dynamics simulation.The dynamic behavior of liquid film on the surface of wire mesh can be divided into the following three steps:(1)spreading step;(2)shrinkage process;(3)stabilizing or disappearing step.Effects of surface wettability,as well as operating conditions,on wetting area and liquid film thickness were studied.Compared to the hydrophilic wire mesh,the final wetting area of hydrophobic wire mesh is zero in most cases.The average liquid film thickness on the surface of hydrophilic wire mesh is 30.02–77.29μm,and that of hydrophobic wire mesh is 41.76–237.37μm.This work provided a basic understanding of liquid film flow at microscale on the surface with various surface wettabilities,which can be guiding the packing optimization and design.展开更多
Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by a...Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by artists and the paper commands very high price in the commercial market. Ink penetrates and spreads optimally in the paper and the words exhibit clear edges with small fluctuations because of the desirable wettability and wicking. These characteristics make it stand out from three Xuan paper samples. The good wettahility, verified by contact angle measurements, is an essential prerequisite to strong wicking. Attenuated total reflectance Fourier-transform infrared spectroscopy is performed to determine the chemical structure of Qianlong Xuan paper and the relatively large hydrogen bonding ratio contributes to the hydrophilicity. The microstructure investigated by scanning electron microscopy and atomic force microscopy reveals wide fibers and a uniform fiber arrangement with good connectivity, dense network, as well as rough fiber surface. These unique properties endow Qianlong Xuan paper with strong wicking to improve the ink expression.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10774032 and 90921001)the Key Knowledge Innovation Project ofthe Chinese Academy of Sciences on Water Science Research,Instrument Developing Project of the Chinese Academy of Sciences(Grant No.Y2010031)
文摘In this work, three-dimensional graphene foams (GFs) are synthesized and characterized by scanning electron micro- scope (SEM) and Raman spectroscopy. The SEM images indicate that after the growth of graphene, the graphene covers the surface of nickel (Ni) foam uniformly. Raman spectra show that the percentages of monolayer, bilayer, trilayer, and multilayer graphenes are - 58%, - 32%, - 8%, and ,.o 2%, respectively. The contact angle (CA) (-- 12°) of water droplet (3 p-L) on GF is found to be larger than that on Ni foam (,- 107°), indicating that graphenes have changed the surface wettability of the Ni foam. Meanwhile, the dynamic characteristics of CA of water droplet on GF are different from those on Ni foam. The mechanisms for different behaviors are discussed, which are attributed to volatilization and seepage of water droplets.
基金supported by the Guangzhou Science and Technology Plan(No.202102020219)National Natural Science Foundation of China(No.51908565)High-level talent research startup project of Chongqing Technology and Business University(No.2356007)。
文摘Membrane-based separation is a promising technology to eliminate water impurities from the oil phase.However,it remains a great challenge to separate water from highly emulsified viscous oil owing to the high stability of the water droplets in oil.Herein we report a surface wettability engineering on an alumina ceramic membrane to achieve an efficient separation of a water-in-oil(W/O)emulsion.Silanes with different carbon chain lengths and fluorinated status were introduced to endow the alumina membrane with different surface wettabilities.While all the modified membranes exhibited excellent separation of the W/O without Span 80(surfactant),the one with amphiphobic wettability and lowest surface energy failed to separate the Span 80 stabilized W/O.The presence of Span 80 reduced the interfacial tension of water droplets,making them easier to deform and penetrate the modified membrane with the lowest surface energy.It reveals that engineering proper surface wettability is the key to separating the oil and water phases.Besides,the modified membranes maintained decent separation performance and stability under long-term run separation of the emulsified W/O.
基金financially supported by the National Natural Science Foundation of China(Nos.51103130 and 21004051)Qianjiang Talents Project of Technology Office in Zhejiang Province(No.2013R10070)
文摘Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry (FTIR), 1H Nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). The resulting copolymer was used to prepare poly(vinylidene fluoride) (PVDF) blend membranes via a phase inversion method. The effects of the copolymer on the polymorphism, surface wettability and zeta potential (0 of the blend membranes were investigated by ATR-FTIR, contact angle instrument and zeta potential analyzer. Scanning electron microscopy (SEM and SEM-EDS) was also applied to investigate the morphology and the surface element changes of the fabricated membranes. The results indicated that P(MMA-co-BVIm-Br) copolymer existed on the surface of the membrane which made the blend membrane have a positive surface during the experimental pH range. The copolymer was also in favor of the formation of βcrystal phase in PVDF membranes. The contact angle experiment indicated that P(MMA-co-BVIm-Br) copolymer could switch the wettability of the blend membranes from hydrophilic to hydrophobic by exchanging Br- anion with PF6-. Compared with pure PVDF membranes, the water flux and water recovery flux of the blend membranes were enhanced obviously. The results from the flux recovery ratio (FR) and total fouling ratio (Rt) all suggested that the blend membranes had good anti-fouling properties.
基金supported by the National Natural Science Foundation of China(21425314,21501184,21434009,21421061,21504098)the Key Research Program of the Chinese Academy of Sciences(KJZD-EW-M01)+2 种基金Ministry of Science and Technology(2013YQ190467)the Top-Notch Young Talents Program of ChinaBeijing Municipal Science&Technology Commission(Z161100000116037)
文摘Surface wettability is important to design biointerfaces and functional biomaterials in various biological applications. However,to date, it remains some confusions about how cells would response to the surfaces with different wettabilities. Herein,we systematically explore the adhesive spectra of cells to the surface with wettability gradient from superhydrophilicity to superhydrophobicity, clarifying the effect of wettability on cell adhesion. We envision that this study may provide valuable information for the design of biomedical implants with controllable cell adhesion, such as neural interface devices and flexible implant.
基金Supported by the National Natural Science Foundation of China under Grant No. 40865008the CMA Chengdu Institute of Plateau Meteorology under Grant No. LPM2008010
文摘Based on 1971-2005 monthly mean maximum/minimum temperature,wind speed,relative humidity,sunshine duration,and precipitation data at 25 stations over the Tibetan Plateau,a study of the largest potential evapotranspiration(LPE) is performed by using the Penman-Monteith model.The surface wettability index(SWI) is calculated and examined,together with its space distribution,interannual and seasonal variations,as well as associated causes.The results suggest that the annual area rainfall exhibits a pronounced increasing trend at 15.0 mm per decade;the annual LPE shows a different-degree decrease at-4.6—-71.6 mm/10 yr.In the southwestern Ngari prefecture and Nyalam county,the annual SWI displays insignificant decline trends compared to increasing trends in other areas of Tibet(0.02-0.09 per decade).For Tibet,on average,the SWI experiences a noticeable rise at 0.04/10 yr,particularly in 1981-2005.On a seasonal basis,the SWI shows increasing trends,especially in summer.In the 1970s-1980s,the interannual variation is characterized mainly by lower temperature and lower humidity.From the 1990s,air temperature keeps on rising,leading to an appreciable increase in SWI,displayed as a type of warm and humid climate.The salient increases(decrease) of precipitation and relative humidity(mean temperature daily range) are the principal causes of the greatly enhanced SWI in the region.The pronounced decrease in mean wind and sunshine duration also plays an active role.
基金the National Natural Science Foundation of China(No.21675133)。
文摘The chemical composition obviously affects the surface wettability of a three-dimensional(3D)graphene material apart from its surface energy and microstructure.In the hydrothermal preparation,the heteroatom doping changes the chemical composition and wettability of the 3D graphene material.To realize the controllable surface wettability of graphene materials,aminobenzene sulfonic acid(ABSA)was selected as a typical doping agent for the preparation of nitrogen and sulfur co-doped 3D graphene foam(SNGF)using a hydrothermal method.Different from using o-ABSA or p-ABSA as the dopant,SNGF with tunable surface wettability is obtained only when m-ABSA is used.This result indicates that the substituent position of-SO3H group in the benzene ring of ABSA is rather important for the tunable wettability.This work provides some theo retical foundations for dopant selection and some new insights in manipulating the properties of 3D graphene foams by adjusting the configuration of dopants.
基金financial supports from the Science and Technology Innovation Commission of Shenzhen(Grant No.JCYJ20190809154007586)National Key Research and Development Program of China(Grant No.2017YFE0120800)+1 种基金National Natural Science Foundation of China(Grant No.U20A20241 and No.51702277)Science and Technology Development Fund of the Macao Special Administrative Region(Grant No.FDCT/013/2017/AMJ)。
文摘Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system needs to be designed.However,with the trend of miniaturization,the heat transfer performance of LHPs degrades rapidly due to the significant increase of working fluid backflow resistance.This work aims to propose an effective solution to this problem.In this work,the surface wettability gradient(SWG)is introduced into the ultra-thin LHP,and the influence of SWG on mass and heat transfer performance is studied comprehensively by using a transient three-dimensional numerical model.It is observed that the SWG can significantly increase the vapor-liquid circulation efficiency and improve heat transfer performance.Numerical experiments have been performed to compare the two kinds of LHPs with and without SWG.At the heat load of 4–6 W,the start-up time for LHP with SWG is shortened by 11.5%and the thermal resistance is reduced by about 44.3%,compared with the LHP without SWG.This work provides a solution for the performance-degradation problem caused by miniaturization,as a numerical reference for experiments.
文摘Fluoroalkyl end-capped vinyltrimethoxysilane-<i><span style="font-family:Verdana;">N</span></i><span><span style="font-family:Verdana;">,</span><i><span style="font-family:Verdana;">N</span></i></span><span style="font-family:Verdana;">-dimethylacrylamide cooli</span><span style="font-family:;" "=""><span style="font-family:Verdana;">gomer [R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(CH</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">-CHSi(OMe)</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">x</span></sub></i><span style="font-family:Verdana;">-(CH</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">-CHC(=O)NMe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">y</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">;R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;"> = CF(CF</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)OC</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">7</span></sub><span style="font-family:Verdana;">:</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;"> R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM)</span><i><sub><span style="font-family:Verdana;">x</span></sub></i><span style="font-family:Verdana;">-(DMAA)</span><i><sub><span style="font-family:Verdana;">y</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">] was synthesized by reaction of fluoroalkanoyl peroxide [R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-C(=O)O-O(O=)C-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">] with vinyltrimethoxysilane (VM) and </span><i><span style="font-family:Verdana;">N</span></i><span><span style="font-family:Verdana;">,</span><i><span style="font-family:Verdana;">N</span></i></span><span style="font-family:Verdana;">-</span></span><span style="font-family:Verdana;">dimethylacrylamide (DMAA). The modified glass surface treated with the</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> cooligomeric nanoparticles [R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">x</span></sub></i><span style="font-family:Verdana;">-(DMAA)</span><i><sub><span style="font-family:Verdana;">y</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">] prepared under the sol-gel reaction of the cooligomer under alkaline conditions was found to exhibit an oleophobic/superhydrophilic property, although the corresponding fluorinated homooligomeric nanoparticles [R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">] afforded an </span><span style="font-family:Verdana;">oleophobic/hydrophobic property on the modified surface under similar </span><span style="font-family:Verdana;">con</span><span><span style="font-family:Verdana;">ditions. R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">x</span></sub></i><span style="font-family:Verdana;">-(DMAA)</span><i><sub><span style="font-family:Verdana;">y</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/</span><b><i><span style="font-family:Verdana;">PSt</span></i></b><span style="font-family:Verdana;"> (micro-sized</span></span> <span style="font-family:Verdana;">polystyrene particles) composites, which were prepared by the sol-gel reac</span><span style="font-family:Verdana;">tions of the corresponding homooligomer and cooligomer in the presence of </span><b><i><span style="font-family:Verdana;">PSt </span></i></b><span style="font-family:Verdana;">particle under alkaline conditions, provided an oleophobic/superhydrophilic </span><span style="font-family:Verdana;">property on the modified surface. However, it was demonstrated that the</span><span><span style="font-family:Verdana;"> surface wettability on the modified surface treated with the R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-</span></span><span><span style="font-family:Verdana;">SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-</span></span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">x</span></sub></i><span style="font-family:Verdana;">-(DMAA)</span><i><sub><span style="font-family:Verdana;">y</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/</span><b><i><span style="font-family:Verdana;">PSt</span></i></b><span style="font-family:Verdana;"> composites changes dramatically from oleophobic/superhydrophilic to superoleophilic/superhydrophilic </span><span style="font-family:Verdana;">and superoleophilic/superhydrophobic characteristics, increasing with </span><span style="font-family:Verdana;">greater </span><span><span style="font-family:Verdana;">feed ratios (mg/mg) of the R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;"> homooligomer in homooligo</span></span><span style="font-family:Verdana;">mer/cooligo</span></span><span style="font-family:Verdana;">mer from 0 to 100 in the preparation of the composites. Such controlled surfac</span>
基金supported by the National Key R&D Program of China(Grant No.2017YFE0116900)the National Natural Science Foundation of China(NSFC,Grant Nos.52275420 and 52130503)+1 种基金the Science and Technology Planning Project of Hunan Province(Grant No.2020WK2011)Postgraduate Scientific Research Innovation Project of Hunan Province(Grant No.CX20200409).
文摘Droplet controllable manipulation over a wide temperature range has promising applications in microelectronic heat dissipation, inkjet printing, and high temperature microfluidic system. However, the fabrication of a platform for controllable droplet manipulation using the methods commonly used in industry remains a tremendously challenge. The popular method of controlling droplets is highly dependent on external energy input and has relatively poor controllability in terms of droplet motion behaviors and manipulation environment, such as distance, velocity, direction and a wide temperature range. Here, we report a facile and industrially applicable method for preparing Al superhydrophobic (S-phobic) surfaces, which enables controlled droplet bouncing, evaporation, and transport over a wide temperature range. Systematic mechanistic studies are also investigated. Extreme wettability surfaces were prepared on Al substrate by a composite process of electrochemical mask etching and micro-milling. To investigate the evaporation process and thermal coupling characteristics, controlled evaporation and controlled bouncing of droplet in a wide temperature range were conducted. Based on the evaporation regulation and bouncing mechanism of droplets on an extreme wettability surface, by using Laplace pressure gradients and temperature gradients, we realized controlled transport of droplets with confluence, split-flow, and gravity-resistant transport over a wide temperature range, offering a potential platform for a series of applications, such as new drug candidates and water collection.
文摘We used silane coupling agents to improve the bonding ability between wheat straw particles and UF resin, and investigated surface properties (wettability and surface roughness) and hardness of parti-cleboard made from UF-bonded wheat straw (Triticum aestivum L.) combined with poplar wood as affected by silane coupling agent content and straw/poplar wood particle ratios. We manufactured one-layered particleboard panels at four different ratios of straw to poplar wood par-ticles (0%, 15%, 30% and 45% wheat straw) and silane coupling agent content at three levels of 0, 5% and 10%. Roughness measurements, average roughness (Ra), mean peak-to-valley height (Rz), and root mean square roughness (Rq) were measured on unsanded samples by using a fine stylus tracing technique. We obtained contact angle measurements by using a goniometer connected to a digital camera and computer sys-tem. Boards containing greater amounts of poplar particles had superior hardness compared to control samples and had lower wettability. Panels made with higher amounts of silane had lower Rq values.
基金financially supported by the National Natural Science Foundation of China(No.51922058).
文摘Marine propellers are important propulsion devices for both surface ships and underwater vehicles.Increasingly severe environmental problems have required further performance enhancement for propellers.Nowadays,traditional methods to improve propeller performances through geometrical and structural optimizations have been extensively investigated,while the underlying mechanisms of the effects of surface and interface properties on marine propellers are still far from being fully understood.This paper presented a comprehensive review of recent advances in the effects of surface and interface properties,such as surface roughness and surface wettability,on marine propellers with an emphasis on the significant improvements in both hydrodynamic and cavitation performances,hoping to arouse more in-depth investigations in the field of surface/interface science and technologies on marine propellers,and also promote the state-of-the-art technologies,such as superlubricity technology,into practical applications.
基金the financial support from the Natural Science Foundation of Jilin Province(Project code:20220101212JC)Jilin Province Specific Project of Industrial Technology Research&Development(Project code:2020C025-2)+2 种基金Free Exploration Project of Changsha Automotive Innovation Research Institute of Jilin University(Project code:CAIRIZT20220202)2021"Interdisciplinary Integration and Innovation"Project of Jilin University(Project code:XJRCYB07)Horizon 2020 MSCA(Project code:H2020-MSCA-RISE-778104-ThermaSMART).
文摘To improve the controllability of the wall-wetting process after the fuel spray-wall impingement in internal combustion engines,the methods of laser etching,chemical etching and surface free energy modification are used to prepare biomimetic structured surfaces with different wettability.The impingement processes of diesel and n-butanol sprays on the walls under different conditions are experimentally investigated.As the surface oleophilicity increases,the spreading radius of wall-impinging sprays decreases.At about 5 s after the fuel injections,the fuel spray droplets hit the walls for the first time,and the secondary breakup and rebound occur.The mixture concentrations of different fuels hitting the various walls reach the peak value.Under a higher surface temperature,the peak value of the mixture concentration is mainly related to the heat flux to the fuel droplets in different boiling regimes from the metal surfaces.The concentration of the air–fuel mixture in the near wall region increases with increasing surface oleophilicity,increasing wall temperature and decreasing ambient pressure.Compared with diesel,n-butanol presents a higher air–fuel mixture concentration in the near wall region.
基金Project supported by the National Natural Science Foundation of China (Grant No.11674345)the Key Research Program of Chinese Academy of Sciences(Grant No. QYZDJ-SSW-SLH019)the Fundamental Research Funds for the Central Universities,China。
文摘Using molecular dynamics simulations, we have revealed a novel wetting phenomenon with a droplet on composite structures formed by embedded water into(111) surface of β-cristobalite hydroxylated silica. This can be attributed to the formation of a composite structure composed of embedded water molecules and the surface hydroxyl(–OH) groups,which reduces the number of hydrogen bonds between the composite structure and the water droplet above the composite structure. Interestingly, a small uniform strain(±3%) applied to the crystal lattice of the hydroxylated silica surface can result in a notable change of the contact angles(> 40°) on the surface. The finding provides new insights into the correlation between the molecular-scale interfacial water structures and the macroscopic wettability of the hydroxylated silica surface.
文摘Guar gum and its derivatives have been the most commonly used polymers to increase the viscosity of fracture fluids.Ceramic proppants are vital products for enhancing oil and gas well productivity in low-permeability reservoirs.In the last several decades,abundant studies have been found in the investigation of proppant size,shape,compositions on the fracture conductivity.However,few types of research can be found to study the proppant wettability effect on the oil and gas flow efficiency.In our research,eight experiments were conducted using traditional guar gum fracturing fluid.Results of this work indicated that ceramic proppant promotes oil flow efficiency from sandstone core samples to proppant packs and thus should promote oil well productivity.The mechanism behind this phenomenon is believed to be the formation of oil flow channels across the fracture face due to the imbibition of oil in the core onto the oil-wet surface of the proppant,promoting oil flow from the core to the fracture.After guar gum was added the results inverted,this phenomenon for water-wet proppant is believed to be increased by the viscosity of fracture fluids which increased the viscosity of water,promoting oil flow from the core to the fracture.Nevertheless,the stimulation effect of oil-wet proppant on oil flow efficiency can be reduced by the presence of guar gum solution.Inside the proppant matrix filled with guar gum fracturing fluid,oil can be blocked inside the proppant matrix as a discontinuous phase while the aqueous phase can be easily mixed with the guar gum fluid and then be transferred out.
文摘Directional fluid transport is of significan</span><span style="font-family:Verdana;">ce</span><span style="font-family:Verdana;"> to many physical processes in nature. How to manipulate this process by man-made material is still a key challenge to scientists. In this study, Janus fabric was constructed by electrospinning a layer of polyvinylidene fluoride (PVDF) nanofibers on woven cotton or gauze. The chemical composition, morphology and surface wettability of two sides of Janus fabric were characterized by infrared spectroscopy, scanning electron microscope (SEM) and contact angle measurement. By controlling the PVDF electrospinning time, the maximum hydrostatic pressure of Janus fabric with different PVDF thickness was measured. It was found that PVDF/gauze is more favorable for unidirectional water transportation, and the moisture also can transfer from hydrophobic side to hydrophilic side. With the advantages of facile preparation, low-cost and one-way water/moisture transportation, the Janus fabric prepared in this study can be applied for water separation, humidity transfer and water collection from the air.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 61178024 and 11374316)partially supported by the National Basic Research Program of China (Grant No.2011CB808103)
文摘We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy.
基金We acknowledge the National Natural Science Funds for Distinguished Young Scholar(No.21725401)the National Key Technologies R&D Program of China(No.2017YFA0207800)+2 种基金the China Scholarship Council(CSC,No.201606025097),the 111 project(No.B14009)the Chinese Postdoctoral Science Foundation(Nos.2017M620012 and 2019M650434)the Fundamental Research Funds for the Central Universities.
文摘The wettability of catalyst plays an important role in regulating catalytic performance in heterogenous catalysis because the microenvironment around the catalytic sites directly determines the mass transfer process of reactants.Inspired by gas trapped on the surface of subaquatic spiders,amphiphilic micro-organohydrogels with tunable surface wettabilities were developed by anchoring various alkane chains onto a poly(2-(dimethylamino)ethyl methacrylate)(p(DMAEMA))hydrophilic microgel network.Palladium nanoparticles(Pd NPs)were encapsulated in amphiphilic microgels(amphiphilic Pd@M)to catalyze hydrogenation reaction,achieving higher activities than pristine monohydrophilic Pd@M composite.The underwater oleophilicity and aerophilicity of Pd@M composites were quantified by oil/gas adhesion measurements and computational simulations.The higher amphiphilic catalytic activities are attributed to the formation of a gas-oil-solid reaction interface on the catalyst surfaces,allowing rapid transport of H2 and organic substrates through water to the Pd catalytic sites.Additionally,amphiphilic Pd@M composites also exhibit more superior catalytic performance in multi-substrates reaction.
基金This work was supported by the National Natural Science Foundation of China(Grant No.22022802).
文摘Droplet impacting on the stainless steel wire mesh is very common in chemical devices,like a rotating packed bed.Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion performance.However,the effect of surface wettability on the impaction phenomena at microscale such as liquid film is still unknown.In this work,the dynamic behavior of liquid film on the surface of wire mesh was analyzed by computational fluid dynamics simulation.The dynamic behavior of liquid film on the surface of wire mesh can be divided into the following three steps:(1)spreading step;(2)shrinkage process;(3)stabilizing or disappearing step.Effects of surface wettability,as well as operating conditions,on wetting area and liquid film thickness were studied.Compared to the hydrophilic wire mesh,the final wetting area of hydrophobic wire mesh is zero in most cases.The average liquid film thickness on the surface of hydrophilic wire mesh is 30.02–77.29μm,and that of hydrophobic wire mesh is 41.76–237.37μm.This work provided a basic understanding of liquid film flow at microscale on the surface with various surface wettabilities,which can be guiding the packing optimization and design.
基金supported by the National Basic Research Programs of China (No. 2011CB922102)the National Natural Science Foundation of China (No. 11374141)the City University of Hong Kong Strategic Research Grant (SRG, No. 7004188)
文摘Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by artists and the paper commands very high price in the commercial market. Ink penetrates and spreads optimally in the paper and the words exhibit clear edges with small fluctuations because of the desirable wettability and wicking. These characteristics make it stand out from three Xuan paper samples. The good wettahility, verified by contact angle measurements, is an essential prerequisite to strong wicking. Attenuated total reflectance Fourier-transform infrared spectroscopy is performed to determine the chemical structure of Qianlong Xuan paper and the relatively large hydrogen bonding ratio contributes to the hydrophilicity. The microstructure investigated by scanning electron microscopy and atomic force microscopy reveals wide fibers and a uniform fiber arrangement with good connectivity, dense network, as well as rough fiber surface. These unique properties endow Qianlong Xuan paper with strong wicking to improve the ink expression.