REVIEW
Corrosion behavior of superhydrophobic surfaces: A
review
Adel M.A.Mohamed a,b,Aboubakr M.Abdullah a,c,*,Nathalie A.Younan a
a Center for Advanced Materials,Qatar University,Doha2713,Qatar
b Department of Metallurgical and Materials Engineering,Faculty of Petroleum and Mining Engineering,
Suez University,Box43721,Suez,Egypt
c Chemistry Department,Faculty of Science,Cairo University,Giza12613,Egypt
Received18January2014;accepted7March2014
Available online24March2014
KEYWORDS Superhydrophobic; Materials; Surfaces; Corrosion; Protection Abstract Superhydrophobic surfaces have evoked great interest in researchers for both purely aca-demic pursuits and industrial applications.Metal corrosion is a serious problem,both economically and operationally,for engineering systems such as aircraft,automobiles,pipelines,and naval ves-sels.Due to the broad range of potential applications of superhydrophobic surfaces,there is a need for a deeper understanding of not only how to fabricate such surfaces using simple methods,but also how speci?c surface properties,such as morphology,roughness,and surface chemistry,affect surface wetting and stability.In this article,a comprehensive review is presented on the researches and developments related to superhydrophobicity phenomena,fabrication of superhydrophobic surface and applications.A signi?cant attention is paid to state of the art on corrosion performance of superhydrophobic coatings.
a2014King Saud University.Production and hosting by Elsevier B.V.All rights reserved.
Contents
1.Introduction (750)
2.Superhydrophobicity phenomena in nature (751)
3.The theory of superhydrophobic surfaces (752)
3.1.Contact angle and the Young equation (752)
*Corresponding author at:Chemistry Department,Faculty of
Science,Cairo University,Giza12613,Egypt.Tel.:+209744403
5672;fax:+2097444033889.
E-mail addresses:abubakr_2@https://www.doczj.com/doc/0216128227.html,,bakr@https://www.doczj.com/doc/0216128227.html,.qa
(A.M.Abdullah).
1878-5352a2014King Saud University.Production and hosting by Elsevier B.V.All rights reserved.
https://www.doczj.com/doc/0216128227.html,/10.1016/j.arabjc.2014.03.006
3.2.Rough surfaces and the Wenzel and Cassie-Baxter models (753)
4.Fabrication of superhydrophobic surfaces (754)
4.1.Sol–gel process (754)
https://www.doczj.com/doc/0216128227.html,yer-by-layer self-assembly (755)
4.3.Etching (755)
4.4.Chemical and electrochemical deposition (756)
4.5.Other techniques used (756)
5.Applications of superhydrophobic surfaces (757)
5.1.Anti-adhesion and self-cleaning (757)
5.2.Anti-biofouling applications (757)
5.3.Corrosion inhibition (757)
5.4.Drag reduction (758)
6.State-of-the-art studies on corrosion resistant coatings using superhydrophobic coatings (758)
7.The stability of the superhydrophobic surfaces (759)
7.1.Solvent stability (760)
7.2.pH stability (762)
7.3.Thermal and humidity stability (762)
7.4.UV stability (762)
References (763)
1.Introduction
Superhydrophobic surfaces have evoked great interest in researchers for both purely academic pursuits and industrial applications.Many review articles covering different aspects of superhydrophobicity have been published(Bhushan and Jung,2011;Ma and Hill,2006;Nakajima et al.,2001;Quere, 2005;Roach et al.,2008;Xue et al.,2010).Superhydrophobic surfaces(SHS)exhibit extremely high water repellency,where water drops bead up on the surface,rolling with a slight ap-plied force,and bouncing if dropped on the surface from a height.
It is well known that the degree to which a solid repels a liquid depends upon two factors:surface energy and surface morphol-ogy.When surface energy is lowered,hydrophobicity is en-hanced.Chemical compositions determine the surface free energy and thus have a great in?uence on wettability (Woodward et al.,2000).However,certain limitations are encountered and superhydrophobic surfaces cannot be obtained only by lowering the surface energy.For example,the–CF3–ter-minated surface was reported to possess the lowest free energy and the liquid droplet.Since air is an absolutely hydrophobic material with a contact angle of180°,this air trapping will amplify surface hydrophobicity(Ogihara et al.,2013;Sun et al.,2005).Hierarchical micro-and nanostructuring of the surface is thus responsible for superhydrophobicity.
Surface wetting behavior can generally be broken into4dif-ferent regimes,based on the value of water contact angle (WCA).The two most conventional regimes are the hydro-philic and hydrophobic regimes,de?ned as WCAs in the range of10°
In addition to high contact angles,superhydrophobic sur-
contact angle(CA)for a water drop placed on surfaces of different hydrophobicities
750 A.M.A.Mohamed et al.
cleaning is the joint action of small adhesion of dust particles high capillary force acting on the dust par-drop–air interface.These properties arise from the low interfacial energy and their rough Barkhudarov et al.,2008).This combination leads to contact angles (WCAs)larger than 150°with and the
self-cleaning effect.
repellency and self-cleaning,other properties incorporated in superhydrophobic surfaces transparency and color (Fig.2),anisotropy,reversibil-breathability (moisture vapor transfer)).
2.Superhydrophobicity phenomena in nature
The amazing water-repellency,superhydrophobicity,plants has received a great deal of interest.eral plants such as Nelumbo nucifera (Lotus),Fig.3,Brassica oleracea ,Colocasia esculenta as well as the wings of butter?ies (Goodwyn the legs of water striders (Gao and Jiang,hydrophobic surfaces.
Gao et al.(2004)showed that the unique ture of the water striders’legs,which are covered bers of oriented tiny hairs (microsetae)with Transparent super-hydrophobic thin ?lm with TiO 2photocatalyst (Nakajima et al.,2001).(b)Colored Ishizaki and Sakamoto,2011).
which exhibit extraordinary water repellency on their upper side.(b)Scanning prepared by ‘glycerol substitution’shows the hierarchical surface structure consisting tubules on the upper leaf side (Ensikat et al.,2011).
responsible for their water resistance.The air trapped in spaces between the microsetae and nanogrooves leads to the superhy-drophobic property of the legs,with a contact angle found to be around167°.This allows water striders to survive on water.
Bechert et al.(2000)showed that the shark skin is covered by very small individual tooth-like scales called dermal denti-cles(little skin teeth),ribbed with longitudinal grooves(aligned parallel to the local?ow direction of the water).These grooved scales reduce the formation of vortices present on a smooth surface,resulting in water moving ef?ciently over their surface.
Neinhuis and Barthlott(1997)reported the water contact angles of more than200plant species and investigated their surface morphologies.There are two different types of water-repellent plant leaves:the?rst type is hair covered leaves such as Lady’s Mantle,and the second type is macroscopically smooth leaves such as Lotus(Otten and Herminghaus, 2004).Water droplets completely run off both plants’leaves and their surfaces remain dry even after heavy rains.
Although many plants have exhibited similar contact angles (around160°),the lotus leaves have shown better stability and perfection as water repellent.These observations have led to the concept of the‘‘Lotus effect’’and made out of the Lotus plant an archetype and an ideal model for superhydrophobic-ity.Some works made it obvious that the contact angle alone is not suf?cient to compare the ef?ciency of superhydrophobic samples(Bechert et al.,2000;Ensikat et al.,2011;Neinhuis and Barthlott,1997).Many other factors interfere,such as the morphology of the epidermal structure(papillose or non-papillose surface),the nanoscopic epicuticular wax crystals of the leaves and the stability of the superhydrophobicity un-der moisture condensation conditions.Only the Lotus plant showed no signi?cant loss of the water repellency property un-der these conditions.
All in all,the unique shape of its papillae,the unique prop-erties of its epicuticular wax and its stable superhydrophobicity have made out of the Lotus leaf an outstanding model for the development of many superhydrophobic structures.
3.The theory of superhydrophobic surfaces
In this section,the theory and fundamentals of wetting of a rough surface and the equations that govern the contact angle of a liquid are presented and discussed.
3.1.Contact angle and the Young equation
Atoms or molecules at the surface of solids or liquids possess fewer bonds with neighboring atoms than those in the interior, and thus,have higher energy.This surface energy or surface tension,c,is equal to the work required to create a unit area of the surface at constant pressure and temperature,and is measured in N/m.The values of surface tension of some mate-rials at20°C,found in the literature,are listed in Table1.
As illustrated in Fig.4a,when a liquid drop is placed in contact with a solid,the equilibrium of the solid and liquid sur-faces will be established at a certain angle called the static con-tact angle CA,h0,given by the Young equation:
cos h0?
c
SA
àc SL
c
LA
e1Twhere c ,c and c are the surface energies of the solid
liquid drop on a(a)smooth solid surface(Bhushan and Jung,2011)and(b)tilted
Nosonovsky and Bhushan,2009).
752 A.M.A.Mohamed et al.
(<10°)in addition to high CA(>150°).As mentioned in the previous sections,a low CAH allows water to roll-off easily along the surface.Occurrence of contact angle hysteresis is associated with the surface defects,which could be from the surface roughness,chemical heterogeneity,or wetting state. According to the difference of contact angle hysteresis,sur-faces can perform as slippery or sticky surfaces.The pinning phenomenon during the evaporation of a droplet is an example of the contact angle hysteresis.
The Young equation was based on the concept of an ideal-ized,atomically smooth solid surface.However,all surfaces have defects and imperfections that contribute to surface roughness, and this roughness will contribute to the surface wetting behavior(Patankar,2004).In view of this roughness-induced wettability modi?cation,two well-established models have been developed to account for these effects:the Wenzel model (1936)and the Cassie-Baxter model(1944).
3.2.Rough surfaces and the Wenzel and Cassie-Baxter models On rough surfaces,the Young equation no longer applies. Wenzel(1936,1949)proposed a model to describe the contact angle,h,with a rough surface,by relating it to that with a?at surface h0.He modi?ed the Young equation as follows:
cos h?r
c SAàc SL
c LA
?r cos h0e2T
This is called the Wenzel equation,where r is the non-
The Wenzel equation is only valid for the homogeneous so-lid–liquid interface shown in Fig.5a.It no longer applies for heterogeneous surfaces.
Therefore,Cassie and Baxter(1944)proposed another mod-el for heterogeneous surfaces composed of two fractions,one with a fractional area f1and contact angle h1and the other with f2and h2,with f1+f2=1.The contact angle is thus given by: cos h?f1cos h1tf2cos h2e4T
For the case of a composite interface,shown in Fig.5b,the ?rst fraction corresponds to the solid–liquid interface (f1=f SL;h1=h0)and the second fraction to the liquid–air interface(f2=f SL=1àf SL;h2=180°).
Combining Eqs.(2)and(4)gives rise to the Cassie&Baxter equation:
cos h?rf SL cos h0à1tf SLe5T
or
cos h?r cos h0àf LAer cos h0t1Te6T
The opposite limiting case with h2=0°,corresponding to the water-on-water contact when the rough surface is covered by holes?lled with water instead of air(Fig.5c),yields the Cassie equation:
cos h?1tf SLecos h0à1Te7T
According to Eq.(6),for a hydrophobic surface(h0>90°), the contact angle increases with an increase of f LA leading thus, to a more hydrophobic surface.For a hydrophilic surface
described by(a)Wenzel equation for homogeneous interface,(b)Cassie and Baxter
Cassie equation for the homogeneous interface(Nosonovsky and Bhushan,2009).
Corrosion behavior of superhydrophobic surfaces753
state are weaker than those in the Wenzel state(Koishi et al., 2011;Lafuma and Quere,2003;Dupont and Legendre,2010; Kong and Yang,2006).For example:Lafuma and Quere (2003)compared the CAH of water droplets in the cases of both Cassie and Wenzel states on the same microtextured sur-face.For the Cassie state,the water droplet was gently dis-pensed on the surface while,in order to maintain the Wenzel state,the water droplet was condensed onto the surface.In addition to a higher advancing CA,it was shown that the CAH was signi?cantly lower in the case of the Cassie state. Koishi et al.(2011)used molecular dynamic simulations to elu-cidate the relationship between the values of the CAH and the corresponding wetting regime.They found that the CAHs,in the case of the composite Cassie state,are weaker in compar-ison with those in the homogenous wetting Wenzel state on the same structure.
It may be concluded that,the Cassie model is a more gen-eral model that can be used to predict entire wetting regimes from low extreme to high extreme,whereas the Wenzel model can predict only moderate homogenous wetting regimes be-tween the two extremes.From the Cassie model,it can be no-ticed that a reduction in the solid fraction and an increase in the air fraction would enhance the water repellency of a sur-face regardless of whether the surface is hydrophobic or hydrophilic.
4.Fabrication of superhydrophobic surfaces
A variety of materials have been used to prepare superhydro-phobic surfaces including both organic and inorganic materi-als.For polymeric materials,which are generally inherently hydrophobic,fabrication of surface roughness is the primary focus.For inorganic materials,which are generally hydro-philic,a surface hydrophobic treatment must be performed after the surface structures are fabricated.Several techniques for the preparation of superhydrophobic
investigated and reported.However,they
vided into two categories(Ma and Hill,
2008;Xu et al.,2011):
i.Making a rough surface from a
material.
ii.Modifying a rough surface with a
face energy.
Various methods are used for the
surfaces,such as mechanical stretching,
layer-by-layer assembly,etching,
electrochemical depositions and chemical
A brief description and use of some of these
niques are presented in the following
4.1.Sol–gel process
The sol–gel process is an ef?cient,
temperature/low pressure procedure and
surfaces on a variety of oxides.This approach
process for the preparation of
materials.The roughness of the surface
cess can be easily modi?ed simply by
of the reaction mixture and the protocol coatings are the most used in the sol–gel method.Sol–gel pro-cesses can produce rough surfaces on a variety of oxides such as silica,alumina,and titania(Roig et al.,2004;Tadanaga et al., 1997).This approach is a very versatile process for the prepara-tion of superhydrophobic thin?lms or bulk materials.The sol–gel process can form a?at surface coating,xerogel coating or aerogel coating depending on the process conditions;both xerogel and aerogel show rough or fractal surfaces.
Barkhudarov et al.(2008)used organo-trimethoxysilanes as starting materials to make optically transparent superhydro-phobic?lms with contact angles exceeding155°and reaching 170°.Xiu et al.(2008)generated superhydrophobic isobutyl surface groups by incorporating isobutyltrimethoxysilane (IBTMOS)into silica layers.With a TMOS/IBTMOS ratio of1:1,a contact angle of165–170°was observed.As shown in Fig.6,the obtained surface consists of globules(20–50nm in diameter)surrounding a network of pores(submicron size), which indicates a hierarchical roughness in two scales:nano-scale and submicron scale.
Latthe et al.(2009)managed to prepare superhydrophobic silica?lms on glass substrates using trimethylethoxysilane as a co-precursor.The silica?lms obtained were transparent and stable to high temperatures(up to275°C)and humidity,hav-ing a water contact angle of151°and a sliding angle of8°.
Feng et al.(2004)managed to grow superhydrophobic aligned ZnO nanorods starting from ZnO sol.Water contact angles exceeding160°were observed.These nanorod?lms exhibited a reversible behavior from superhydrophobicity to superhydrophilicity by alternation of ultraviolet irradiation and dark storage:after UV illumination for2h,the water con-tact angle drops from$160°to0°and returns to the initial va-lue after storage in the dark for7days.The reason for the reversible behavior is due to the generation of electron–hole pairs in the ZnO surface resulting from the UV irradiation, some of these holes can react with the lattice oxygen to form Figure6High resolution SEM image of a silica?lm with TMOS/IBTMOS ratio of1:1(Xiu et al.,2008).
754 A.M.A.Mohamed et al.
only the upper part of the nanorods not in contact with liquid. This effect results in a water CA of about0o(Sun et al.,2001; Bico et al.,2001).
It should be stated that these superhydrophobic coatings synthesized using the sol–gel processing are usually stable due to the formation of covalent bonds between the coating and the substrate(Xue et al.,2010).The resulted coatings are robust and rough(Xiu et al.,2008).
https://www.doczj.com/doc/0216128227.html,yer-by-layer self-assembly
The layer-by-layer(LBL)assembly is a simple and cheap meth-od to construct thin-?lm coatings by depositing alternating layers,oppositely charged,with intermediate washing steps. It uses electrostatic interaction and covalent bonds to form multilayer grafts.The advantage of this technique is that it possesses a high degree of molecular control over the?lm thickness,which arises from the linear growth of?lms with re-spect to the number of bilayers.Recently,LBL method has sponds to the number of deposition cycles.The resulting super-hydrophobic coatings on steel substrate exhibited a strong repulsive force to water droplets,with contact angles greater than165°.Fig.7illustrates water droplets on the three layers of TiO2nanoparticle coated surface and shows SEM images of one to three layers of P25on the steel surfaces.Zhai et al. (2004)also prepared a polyelectrolyte multilayer surface by LBL assembly and then overcoated the surface with silica nanoparticles to mimic the hierarchical scale present on lotus leaf surfaces.Superhydrophobicity was achieved after surface ?uorination with a?uoroalkyl silane.
Amigoni et al.(2009)constructed hybrid organic/inorganic surfaces by alternating different layers of amino-functionalized silica nanoparticles and epoxy-functionalized smaller silica nanoparticles.They found out that the hydrophobicity in-creases with the number of layers and obtained a water contact angle around150°with the alternation of nine layers.
LBL assembly could be combined as well with electrode-position to make superhydrophobic coatings as described by Zhao et al.(2005).
images of different layers of TiO2nanoparticles in steel surface:(a)Water droplets on the treated steel
)*1.(c)TiO2two layers(TiO2)*2and(d)TiO2three layers(TiO2)*3(Isimjan et al.,2012).
Corrosion behavior of superhydrophobic surfaces755
on the chemical etching time.A contact angle larger than150°was achieved at an etching time of more than3min.
Pan et al.(2010)established a simple cetyltrimethylammo-nium bromide(CTAB)and ultrasonication assisted nitric acid HNO3etching technique to fabricate a rough surface on the copper substrate.A superhydrophobic coating was obtained with a contact angle around155°.
Gao et al.(2012)fabricated a rough surface on the zinc sub-strate using a glow discharge electrolysis plasma(GDEP)reac-tor to etching.This apparatus consists of a high voltage supply unit and two electrodes submerged in an electrochemical cell separated by a dielectric wall with a diaphragm.
Shiu et al.(2005)developed an approach for making tun-able superhydrophobic surfaces using oxygen plasma etching. Water contact angles up to170°were obtained.
4.4.Chemical and electrochemical deposition
Chemical and electrochemical deposition techniques have been intensively employed to prepare superhydrophobic surfaces. Darmanin et al.(2013)reviewed the most published researches showing the details of electrochemical oxidation processes, such as oxidation of metals in solution,anodization of metals or electrodeposition of conducting polymers,and reduction processes,e.g.,the electrodeposition of metals and galvanic deposition.
Ou et al.(2012)investigated the corrosion behavior in NaCl solution of superhydrophobic surfaces prepared by1H,1H, 2H,2H-per?uorooctyltrichlorosilane(PFOTS)chemically ad-sorbed onto the etched titanium substrate.It has been shown that the strong chemical interfacial bonding between PFOTS and Ti leads to a higher stability and corrosion inhibition ef?-ciency.Yin et al.(2008)also prepared a stable superhydropho-bic?lm by mystic acid chemically adsorbed onto anodized aluminum substrate.The contact angle was in the order of 154°,and corrosion in seawater was signi?cantly decreased.
Huang et al.(2013)demonstrated that the copper surface covered with copper stearate,which was formed by an electro-chemical reaction with a DC voltage of30V in stearic acid solution,showed superhydrophobic properties.Shirtcliffe et al.(2004)electrodeposited copper from acidic copper sulfate solution onto?at copper substrates to obtain superhydropho-bic surfaces of varying levels of roughness,depending on the current density during deposition.
4.5.Other techniques used
Other approaches to the fabrication of superhydrophobic sur-faces have been developed and used,these include spraying nanoparticle suspensions onto substrates(Ogihara et al., 2013),chemical vapor deposition(Ishizaki et al.,2010),elec-trospinning(Acatay et al.,2004;Ma et al.,2005),sublimation (Nakajima et al.,1999),hydrothermal synthesis(Shi et al., 2005),and wax solidi?cation(Onda et al.,1996).
Spraying is a one-step,time-saving,low-cost and repairable method for preparation of superhydrophobic surfaces.Xu et al.(2011)fabricated superhydrophobic copper meshes by evenly spraying an emulsion of n-octadecanethiol and silver ni-trate in ethanol onto the copper mesh with nitrogen gas by a spray gun.Alkanethiols contain long-chain alkyl groups that have low surface free energy.One advantage of this method is that in the case of mechanical damage of the surface,it can simply be repaired by partial spraying.In a similar way, Ogihara et al.(2013)prepared superhydrophobic paper using mixtures containing nanoparticles and ethanol,manually sprayed over paper from20cm away with a vaporizer.In this case,the surface energy and the roughness structure could be controlled by the spray-coating conditions,such as the type of nanoparticles and their size.
Electrospinning is another powerful,simple and practical one-step method to generate continuous ultrathin?bers with micrometer and sub-micrometer diameters from a variety of polymeric materials.Electrospun?bers intrinsically provide at least one length scale of roughness for superhydrophobicity because of the small?ber size.The?ber mats composed solely of uniform?bers could be obtained by electrospinning a hydrophobic material(i.e.,poly(styrene-block-dimethylsilox-ane)block copolymer)blended with homopolymer polystyrene (PS)(Ma et al.,2005).Table2shows the most important parameters controlling the electrospinning process.
Acatay et al.(2004)electrospun a thermoset?uorinated polymer onto an aluminum foil substrate,by applying an elec-trical bias from the tip of the polymer solution-?lled syringe to a grounded collection plate.The formed electrospun?lm con-sisted of a continuous web or mat of randomly aligned?bers.
After the roughening of the surfaces,most substrates still do not show superhydrophobicity.Consequently,the surface energy of such coatings should be lowered using low surface energy materials.The most common ones are?uorocarbons, silicones,and some organic materials(polyethene,polystyrene, ...).Although,inorganic materials such as ZnO and TiO2have high surface energy,the nanoparticles from these materials are easily covered by airborne organic contaminations.Due to such contaminations the surfaces modi?ed with such nanopar-ticle layers may demonstrate superhydrophobic behavior.For instance,?uoroalkylsilane(FAS)molecules were intensively used by several groups in order to modify the surface and en-hance superhydrophobicity due to their extremely low surface free energy and the simple reaction of the silane groups with
Table2Most important electrospinning parameters(Sas et al.,2012).
Materials properties Process parameters Equipment design Ambient conditions Viscosity Electrical?eld strength Needle design Relative humidity Conductivity Solution charge polarity Collector geometry Temperature
Solvent volatility Electrical signal type Surrounding medium Surface tension Tip to collector distance
Polymer MW Flow rate
Polymer type Collector take-up velocity
756 A.M.A.Mohamed et al.
the hydroxyl groups on coatings(Hu et al.,2012;Ishizaki et al.,2011;Liang et al.,2013;Song et al.,2012).
5.Applications of superhydrophobic surfaces
The impetus for the development of materials with superhydro-phobic properties is for use in practical applications.Superhy-drophobic surfaces have attracted growing interest in the past two decades because of their unique water repellency,self-clean-ing property and their importance in various applications, including self-cleaning windows,roof tiles,textiles,solar panels and applications requiring anti-biofouling and reduction of drag in?uid(micro/nanochannels)(Bhushan and Jung,2011). Some agricultural applications were also discussed,such as bio-medical applications(Xiu et al.,2007),stain resistant textiles (Satoh and Nakazumi,2003),ant-sticking of snow for antennas and windows(Kako et al.,2004)and many others.One of the most important applications for superhydrophobic surface is corrosion resistance for metals and alloys,and remains the most signi?cant goal in this review.The following section includes how superhydrophobic coatings are used to improve the perfor-mance of some applications by surface modi?cation.
5.1.Anti-adhesion and self-cleaning
As previously mentioned,the high water contact angle(above 150°)and the low contact angle hysteresis of superhydropho-bic surfaces characterize them with low adhesion and self-cleaning properties that are extremely useful for practical applications such as self-cleaning window glasses.
In a natural environment,surfaces get contaminated very easily and frequently.Cleaning them requires effort,time and money.Thus,the creation of substrates that are self-clean-ing and that have low-adhesion to contaminants has been a hot topic of research for several decades.As illustrated in Fig.8,when a water droplet rolls off a superhydrophobic sur-SiO2nanoparticles onto the etched?lm.They showed that much of the red powder was still spread on the uncoated sur-face after cleaning with water droplets as compared to the superhydrophobic surface,which was much cleaner.More-over,dust particles were heavily sprinkled on the coated sur-face and were simply removed by?ipping it,showing the anti-adhesion property for contaminants of such?lms.
Superhydrophobic surfaces with self-cleaning property also have many applications in the textile industry.For example, self-cleaning textile shirts,blouses,skirts and trousers,which are stain-proof,have already been synthesized(Xue et al., 2010).Furthermore,the self-cleaning effect is used in optical applications,such as solar panels,lenses and mirrors that have to stay clean(Nosonovsky and Bhushan,2009).
5.2.Anti-biofouling applications
Biofouling of underwater structures and ships’hulls,in partic-ular,increases operational and maintenance costs(Gudipati et al.,2005;Townsin,2003).It can be reduced through under-water superhydrophobicity,i.e.,forming a hydrophobic rough surface that supports an air?lm between itself and the water (Marmur,2006).The reduction of the wetted area minimizes the probability that biological organisms encounter a solid sur-face.The design of such surfaces should involve optimization between mechanical stability and minimal wetted area.The anti-biofouling properties of superhydrophobic coatings have been investigated(Zhang et al.,2005).Compared to normal substrates,which fouled within a day,almost no micro-organ-isms attached to the superhydrophobic surfaces in the?rst week after immersion.
5.3.Corrosion inhibition
The concept of preparing surfaces that repel water creates huge opportunities in the area of corrosion inhibition for metals and alloys.Given their water repellency,superhydrophobic coat-
rolling off substrates with a normal hydrophobic surface(left)and a self-cleaning
particles(Xue et al.,2010).
Corrosion behavior of superhydrophobic surfaces757
5.4.Drag reduction
Turbulent?ows of a liquid along a surface experience fric-tional drag,a macroscopic phenomenon that affects the speed and ef?ciency of marine vessels,the cost of pumping oil through a pipeline,and countless other engineering parame-ters.The drag arises from shear stress,the rate per unit area of momentum transfer from the?ow to the surface.Superhy-drophobic surfaces can be fabricated in order to reduce the drag based on its highly water repellent property and capable of forming a thin air?lm over an underwater surface which stops the surface from becoming wet.The air?lm formed over the surface has the property of being able to take in air sup-plied from outside because of the surface tension of water. The superhydrophobic surfaces to reduce frictional drag have been used in ships.When air is supplied from the bow section to a ship’s hull with superhydrophobic coatings,it becomes at-tached to the superhydrophobic surface and forms an air?lm on it.The frictional drag can thus be reduced by an air lubri-cant effect.
6.State-of-the-art studies on corrosion resistant coatings using superhydrophobic coatings
Corrosion is the decaying or destruction of a material due to chemical reactions with its surroundings.In other words,cor-rosion is the wearing away of metals due to a chemical reac-tion.Superhydrophobic coatings on metallic substrates have shown,during the past two decades,remarkable corrosion resistance in highly aggressive media.Many techniques of pre-paring such surfaces,as well as various methods of character-ization and analysis were applied,but the conclusion was the same and it states that superhydrophobic coatings prevent metallic substrates from corrosion.The air retained on such superhydrophobic surface can prevent corrosive processes, e.g.,chloride ions in seawater from attacking the metal surface, offering a new ef?cient mechanism for anti-corrosion(Fig.9) (Jeong,2013;Liu et al.,2007;Yin et al.,2008;Zhang et al., 2008).Table3summarizes the current state-of-the-art studies on anti-corrosion using superhydrophobic coatings.Although the idea of using the air retained on the superhydrophobic surface as a passivation layer is promising as a new ef?cient the structural dimensions and shapes has been a critical draw-back,precluding the systematic understanding of the effect of superhydrophobic surface parameters on the corrosion resistance as well as the practical applications in a controllable way.
Ning et al.(2011)managed to form a stable superhydro-phobic surface on zinc substrates by means of one-step platinum replacement deposition process without any further modi?cation,simply by immersing the zinc in PtCl4solution. The structure of the surface exhibited high roughness and porosity which led to high corrosion resistance with contact angles>150°,in different corrosive media,as compared to unprotected zinc plates.The effect of the superhydrophobic ?lm on the corrosion behavior of zinc was investigated using linear sweep voltammetry(LSV).The results showed that,in the presence of the superhydrophobic surface,the anodic corrosion potential is shifted toward more noble values and the anodic and cathodic corrosion currents are signi?cantly reduced.Furthermore,the prepared surface was proven to be stable in sodium hydroxide solution,hydrochloric acid solu-tion and toluene solvent,maintaining all its superhydrophobic characteristics.
Similar results have been obtained by Yuan et al.(2011) who investigated the corrosion behavior of?uoropolymer ?lms on copper substrates,in NaCl solution,by the measure-ments of Tafel polarization curves and electrochemical imped-ance spectroscopy(EIS)spectra.They also found that the corrosion potential undergoes a positive shift toward more no-ble values.Furthermore,the magnitude of the corrosion cur-rent was lower by about12-fold as compared to the bare copper,after21days of exposure in the NaCl(3.5%)solution.
Yin et al.(2008)studied the corrosion inhibition,in seawa-ter,of superhydrophobic?lms prepared by chemical adsorp-tion of myristic acid onto anodized aluminum substrate.The polarization curves showed the same results concerning the corrosion potential and corrosion currents.The corrosion inhi-bition ef?ciency was also calculated and yielded an increase from61%to96%,for the uncoated and coated anodized alu-minum surfaces,respectively.
Scanning electron microscope(SEM)and measurements of the water contact angles can also be useful to predict the anti-corrosion ability of superhydrophobic coatings.Kang et al. (2011)investigated the corrosion resistance of porous polyvi-
concept of anti-corrosion using a superhydrophobic surface.The micro-or nano-structured superhydrophobic interface with water by retaining air on the surface.The composite interface minimizes the
preventing chloride ions,which is a major corrosive constituent in seawater,from invading the metal
758 A.M.A.Mohamed et al.
As de?ned by Piron (1991),in his book entitled ‘‘The elec-trochemistry of corrosion’’,corrosion is the destruction of a metal by chemical or electrochemical reactions between the me-tal and its environment.This de?nition includes electrochemi-cal corrosion in aqueous media,molten salts,or in other environments where two simultaneous reactions involve elec-tron transfers.Oxidation of the metal liberates electrons,which are accepted by the reduction of another substance such as hydrogen ions or oxygen.This de?nition also includes the destruction of metals by oxidation at high temperatures in a so-lid–gas reaction,which is considered to be a chemical reaction.All active metals such as aluminum,zinc,iron,...,and their alloys are prone to corrosion in contact with water,especially in aggressive and corrosive environments such as in alkaline or acidic media,or in strongly saline aqueous solutions.There-fore,it is necessary to enhance their corrosion resistance prop-erty in corrosive environment which will greatly extend their industrial applications (Yu et al.,2013).
In dry environments,metals and alloys usually develop a thin oxide layer onto their surface.This oxide layer protects the metal from further corrosion.However,in aqueous,salty and other aggressive environments,the oxide layer is pene-trated and can no longer inhibit further corrosion.Given the properties mentioned above,especially the water repellency,superhydrophobic coatings form an important and successful method to slow down the breaking of the oxide layer and thus prevent the metal surface underneath from further corrosion.Zhang et al.(2011)explained the mechanism of anti-corrosion of superhydrophobic coated titania/titanium surface by suggesting that the ?lm is suf?ciently densely packed to pre-vent the diffusion of oxygen to the substrate.They attributed the excellent anti-corrosion property of the ?lm to the air trapped in the nanopores,which prevents in?ltration of water into the substrate and limits the concentration of corrosive species in the titania/titanium holes.
Yu et al.(2013)studied the corrosion behavior of Ni-P,TiO 2and octadecyltrimethoxysilane (ODS)superhydrophobic composite coating on carbon steel.They reported that the three-layer composite coating on C-steel improves the corro-sion resistant in sterilized seawater,as seen in Fig.10.
The corrosion resistance mechanism of superhydrophobic surfaces proceeds as follows:when exposed to a corrosive med-ium,superhydrophobic coatings,made of hierarchical rough structures can easily trap a large amount of air within the val-leys between the rough structures (Xu et al.,2011).These ‘‘air valleys’’prevent the in?ltration of corrosive ions,such as Cl à,as illustrated in the simulated model in Fig.11.
Another important reason why the modi?ed surface can improve the anticorrosion of metals is ‘capillarity’,which was introduced by Liu et al.(2007).They showed that,for con-tact angles higher than 150°,the water transport against grav-ity is easy in the porous structure of the superhydrophobic surfaces.As a result,the seawater can be pushed out from the pores by the Laplace pressure and thus,the substrate could be perfectly protected from corrosion in the seawater.7.The stability of the superhydrophobic surfaces
For engineering applications of superhydrophobic surfaces,the stable behavior under various conditions needs to be investigated.Stability issues in solvents including organic
T a b l e 3
S t a t e -o f -t h e -a r t s t u d i e s o n a n t i -c o r r o s i o n u s i n g s u p e r h y d r o p h o b i c c o a t i n g s .
R e f e r e n c e s
S u b s t r a t e m a t e r i a l s
S u r f a c e t r e a t m e n t
T e s t s o l u t i o n
T e s t m e t h o d
M a i n r e s u l t s a n d i s s u e s
S h c h u k i n e t a l .(2006)
A l u m i n u m a l l o y
L a y e r -b y -l a y e r (L b L )
5%N a C l
E l e c t r o c h e m i c a l i m p e d a n c e s p e c t r o s c o p y (E I S )
T h e n a n o r e s e r v o i r s i n c r e a s e l o n g -t e r m c o r r o s i o n p r o t e c t i o n o f t h e s u b s t r a t e a n d p r o v i d e e ?e c t i v e i n h i b i t o r s t o r a g e a n d i t s p r o l o n g e d r e l e a s e o n d e m a n d L i u e t a l .(2007)
C o p p e r
M y r i s t i c a c i d
S e a w a t e r
P o l a r i z a t i o n ,E I S
T h e c o r r o s i o n r e s i s t a n c e o f t h e m a t e r i a l w a s i m p r o v e d r e m a r k a b l y Y i n e t a l .(2008)A l u m i n u m M y r i s t i c a c i d S e a w a t e r P o l a r i z a t i o n ,E I S F i l m s t a b i l i t y s h o u l d b e i m p r o v e d f u r t h e r B a r k h u d a r o v e t a l .(2008)
A l u m i n u m
O r g a n o s i l i c a a e r o g e l c o a t i n g
5%N a C l
N e u t r o n R e ?e c t i v i t y
T h e s u r f a c e p r e v e n t s i n ?l t r a t i o n o f w a t e r i n t o t h e s u p e r h y d r o p h o b i c p o r o u s ?l m a n d l i m i t s t h e e x p o s u r e o f c o r r o s i v e e l e m e n t s t o t h e m e t a l s u r f a c e Z h a n g e t a l .(2008)
A l u m i n u m
H y d r o x i d e ?l m s
3.5%N a C l
O p e n -C i r c u i t P o t e n t i a l P o l a r i z a t i o n G o o d ?l m a d h e s i o n a n d m e c h a n i c a l s t a b i l i t y
L i u e t a l .(2007)Z i n c P F T S 3%N a C l P o l a r i z a t i o n H i g h e r c o r r o s i o n r e s i s t a n c e p r o p e r t i e s I s h i z a k i e t a l .(2011)
M a g n e s i u m a l l o y
F A S
5%N a C l
P o l a r i z a t i o n ,E I S
S u p e r h y d r o p h o b i c s u r f a c e w o u l d b e a n e ?e c t i v e s t r a t e g y f o r i m p r o v i n g t h e a n t i c o r r o s i o n p e e r p e r f o r m a n c e o f v a r i o u s e n g i n e e r i n g m a t e r i a l s d e L e o n e t a l .(2012)
S t e e l P o l y t h i o p h e n e 3.5%N a C l
P o l a r i z a t i o n
F a b r i c a t i o n o f t h e d u a l p r o p e r t i e s o f s u p e r h y d r o p h o b i c a n t i c o r r o s i o n n a n o s t r u c t u r e d c o n d u c t i n g p o l y m e r c o a t i n g f o l l o w s a t w o -s t e p c o a t i n g p r o c e d u r e t h a t i s v e r y s i m p l e a n d c a n b e u s e d t o c o a t a n y m e t a l l i c s u r f a c e
Corrosion behavior of superhydrophobic surfaces
759
and aqueous,basic and acidic solutions,thermal stability,as well as the in?uence of humidity and UV radiation will be dis-cussed in this section.In general,high chloride concentration, high temperature and low pH represent the main reasons responsible for damaging the surfaces.7.1.Solvent stability
Many works have been carried out in order to study the stabil-ity and durability of superhydrophobic coatings on different metallic substrates,in water and various organic solvents.
Figure10Nyquist(a–b)and bode(c–F)plots of the composite coatings from the electrochemical impedance spectroscopy(EIS) al.,2013)where,CS:carbon steel;NP:Ni-P;TZ:TiO2/ZnO;ODS:octadecyltrimethoxysilane.
For instance,Isimjan et al.(2012)investigated the effect of water,chloroform and decane on the contact angles of TiO2/SiO2coated steel substrates measured after every24h for a period of eight days.It was shown that the contact angles remained constant and the surfaces were stable even after 8days.In another work,coated zinc substrates were immersed in toluene for24h at room temperature(Ning et al.,2011).The resulting contact angles had no
good stability of the surface.
The stability of superhydrophobic
substrates in seawater was also intensively
the conservation of superhydrophobicity
duration exposure(He et al.,2009;
Yin et al.,2008;Yu et al.,2013).Zhu
a superhydrophobic?lm by using electroless
coating on carbon steels.The superhydrophobic
stability in the air at room temperature
resistance in5wt%NaCl solution,
and water erosion test.Boinovich et
the corrosion behavior of highly hydrophobic
phobic coatings for low C-steel steel under
tions and aggressive media.Their results
durable protection against corrosion is
tion of multilayer coatings which contain superhydrophobic layer in combination
potentiodynamic polarization curves
solution for low-carbon steel samples
layers are shown in Fig.12.
Boinovich et al.(2013)also investigated
ent corrosive active media on the Mg–Mn–Ce nanocomposite syperhydrophobic materials.
that the preliminary plasma electrolytic oxidation of alloy im-proves the adhesion and water repelling properties of the coat-ings and consequently increases the corrosion resistance of Mg alloy.Xu et al.(2011)fabricated the superhydrophobic coating for Mg alloy using a facile electrochemical machining process. Their results showed that the superhydrophobic Mg alloy sur-face has excellent corrosion resistance in acidic,alkaline and salt solutions.Table4presents the corrosion potential(E corr)
interface between superhydrophobic surface and corrosive seawater.The Clàions
valleys’(Liu et al.,2007).
Figure12Polarization curves in0.5M NaCl aqueous solution
for low-carbon steel samples with different surface layers:(1)
Native oxide;(2)MC-1+NSC(MC-1:Magnetite coatings
formed at98°C and at high stirring,NSC:nanocomposite
superhydrophobic coatings);(3)MC-2+NSC(MC-2:Magnetite
coatings formed at92°C);(4)PEO+NSC(Boinovich et al.,
2012).
Table4E corr and I corr of the untreated and superhydrophobic Mg alloy surfaces in different corrosive solutions(Xu et al.,2011). Sample NaCl solution Na2SO4NaClO3NaNO3
E corr I corr E corr I corr E corr I corr E corr I corr Untreated Mg alloy Surfaceà1.5859.96·10à5à1.616 4.71·10à7à1.5258.58·10à7à1.403 1.15·10à7 Superhydrophobic Mg alloy surfaceà1.4229.68·10à8à1.5107.62·10à8à1.5307.37·10à10à1.285 3.51·10à9
and corrosion current density(I corr)of untreated and superhy-drophobic Mg alloy in different corrosive media.
Barkhudarov et al.(2008)investigated the behavior of superhydrophobic coatings as corrosion inhibitors.They con-cluded that the extreme case of a superhydrophobic coating with a contact angle of>160°decreases the rate of corrosion roughly tenfold compared to the unprotected aluminum. Fig.13shows the changes in aluminum thickness after the test with different surface conditions.
Liu et al.(2009)successfully created a superhydrophobic surface on aluminum surface by an anodization process and chemical modi?cation using myristic acid.Their results showed that,the superhydrophobic surface signi?cantly im-proves the corrosion resistance of aluminum in sterile seawa-ter.The superhydrophobic surface affects mainly the aluminum anodic reaction,whose currents(I corr)are reduced by about three orders of magnitude,the corrosion potential (E corr)shifts positively by0.2V when the anodized aluminum is covered with the myristic acid.The signi?cant point of this research is the possibility of applying this method to a large scale production of superhydrophobic engineering materials for ocean industrial applications.In another research,Liu et al.(2009)studied the use of superhydrophobic surfaces on aluminum as a method for inhibition of microbially in?uenced corrosion.Their study showed that the superhydrophobic?lm does not only decrease the corrosion current densities,but also microbially in?uencing corrosion acceleration inhibition due to preventing colonization of microorganisms.
7.2.pH stability
The stability of superhydrophobic surfaces over a wide pH-range is crucial for their use as engineering materials in several industrial applications.Guo et al.(2005)investigated the sta-bility of coated aluminum alloy,over the pH range from1 to14.All the measured contact angles were around160°to drophobicity.The contact angle decreased with increasing temperature and the contact angle hysteresis increased.How-ever,when the as-prepared silica?lms were modi?ed with?uo-roalkyl silanes,the thermal stability was signi?cantly improved:at a temperature of400°C,the surface remained stable.Further heating resulted in a decrease of contact angle and when the temperature reached500°C,the?lm was no longer hydrophobic(contact angle almost became0°).
Latthe et al.(2009)studied the in?uence of temperature on silica coatings by putting the samples in a furnace for5h.It was found that the?lms retained their superhydrophic prop-erty up to a temperature of275°C.Above this value,the?lms became superhydrophilic with contact angles smaller than5°.
Furthermore,the in?uence of humidity was also investi-gated.The silica?lms were exposed to a relative humidity of 85%,at30°C for a duration of60days.The results showed a strong stability and durability against humidity.
Similar results were obtained by Rao et al.(2011)who investigated the effect of humidity on the wetting properties of silica?lms on copper substrate.The experiment was carried out at a relative humidity of95%at35°C for a period of 90days.No signi?cant change in the superhydrophobicity of the?lms was observed,showing the durability and resistance of such surfaces against humidity.
7.4.UV stability
The stability of superhydrophobic?lms against UV irradiation is extremely important,especially for outdoor surfaces that are exposed to UV light.Feng et al.(2004)obtained superhydro-phobic ZnO nanorod?lms that lost their superhydrophobicity under UV illumination for2h:the water contact angle dropped from160°to0°.
On the other hand,the results obtained by Isimjan et al. (2012)revealed that the TiO2/SiO2coated steel surfaces strongly resist against UV radiation:the contact angles remain constant even after a period of5h UV exposure.This was ex-plained by the fact that in the presence of SiO2nanoparticles,
Figure13The change in aluminum thickness versus time for samples protected by?lms of varying contact angle and a sample with only native Al203layer.The superhydrophobic?lms improved corrosion resistance by a factor of six compared to unprotected aluminum surface(Barkhudarov et al.,2008).
the high energy electrons generated by TiO2under UV cannot diffuse to the surface and thus,no hydroxyl radicals can be formed and no oxidation will occur.
Xiu et al.(2008)managed to fabricate one of the most stable superhydrophobic silica surfaces treated with?uoroalkyl si-lanes,which showed resistance after5500h UV irradiation without degradation of either contact angle or contact angle hysteresis.The fact that the C A F bonds are much stronger than the C A H bonds was the reason of this improved UV stability. References
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Uncivilized behavior of Chinese tourists “You see, it’s common, most people didn’t care”said by one female tourist who is just throwing trash on the San Ya beach which has already been reduced to a dumping ground. When the beautiful island meets holiday crowd, under the hustling and bustling scene, we absolutely startled by the carving “Dao ci yi you”, dumbling beer bottles, spilling peels and half-burned branches. These facts are still far from enough.Uncivilized behavior makes headlines in the National Day holidays. At the memorable flag-raising ceremony at Tiananmen Square on October 1, over 120,000 participants left five tons of trash behind after showing their respect to the country. Sometimes, you could not find a place to sit –men take up all the benches in the park, lying full-length and blissfully snoring the afternoon away.Spitting, talking loudly and random littering are frequent scenes in tourist attractions. Countless visitors allow their children to use the city streets as a toilet, even though there is a toilet nearby. Newsstand and bookshop proprietors also suffer from bad-mannered people who tear the wrappers off magazines and read the contents without buying them. Bookstore visitors ignore the signs of asking them to rest only in designated areas instead of sitting on the stairwell. Similar stories are testing the tolerance of public opinion almost every day. We could be denied those undesirable manner. Nevertheless, it will be more persuasive to point out that China's tourism industry is not developing in a gradual way, but in a blowout manner. Growing wealth enables more Chinese people to seek leisure and fulfillment from traveling. Considering China's large population, some problems and challenges must emerge at the same time.We might be disappointed but not be desperate. Objectively speaking, before the national holiday, civilized traveling aroused surges of attention such as Wechat hot debate, media focus, screen exposure, which is beyond the past several years.Under the supervision of public opinion, the index of civilized golden week presents positive improvement. However,it’s still a serious short board that reflects on Chinese social moral deficiency. Not only should we take it seriously, but also wake up the consciousness of citizen responsibility and turn it in to action to make up. Forming harmonious social morality as if human’s maturation. We need time. I do believe the enlightened public moral education combined with perfected facilities will take several generations to nurture civilized behavior and display a positive image of Chinese tourists.
Listen to part of a lecture in a biology class. The class is discussing animal behavior. Okay Ok , the next kind of animal behavior I want to talk about might be familiar to you. You may have seen, for example, a bird that's in a the middle of a mating ritual. and suddenly it stops and prines preens . You know, takes a few moments to straight straighten its feathers. and then returns to the mating ritual. This kind of behavior, this doing something that seems completely out of place. It's is what we call a displacement activity. Displacement activities are activities that animals engaged animal's engaging in when they have conflicting drives. If we take our example for from a minute ago if the bird is afraid of its mate, it's conflicted. It wants to mate, but it's also afraid and wants to run away. So instead, it starts grooming itself. So the displacement activity the grooming, the straightening of its feathers seems to be an irrelevant behavior. So what do you think another example of the a displacement activity might be? How about an animal that , um, instead of fighting its enemy or running away, it attacks a plant or a bush. That's a really good suggestion, Carol Karl . But that's called redirecting. The animal is redirecting its behavior to another object. In this case, the plant or the bush. But that's not an irrelevant or inappropriate behavior. The behavior makes sense. it's appropriate under the circumstances, but what doesn't make sense is the object behaviors direct the behavior's directed towards. Okay Ok , who else? Carol? I think I've read in another class about an experiment were where an object that the animal was afraid of was put next to its food. next to the animal's food. And the animal, it was conflicted between confronting the object and eating the food, so instead
Public Behavior Thanks to years of huge effort, China is getting stronger and stronger. However, when the bright side is showing, something bad arises too ——terrible public behavior. When we are watching TV, it is normal to hear some bad behavior that happened. But the most common one in our daily life should be breaking traffic rules, or more accurately, running the red light. Large numbers of passengers, motorists, or even car drivers, ignoring the red light which means stop, continued on their way, abandoning their morality as well as lives. Tragedies that had happened seem to be unable to arouse their vigilance. As a result, more and more tragedies are going on. Others may value their lives indeed, but do not pay the same attention to the environment as they should, which makes spitting and littering a common but terrible phenomenon. When asked about the behavior, most of the public will surely admit that it is not right. And yet what force one to do the things he thinks is wrong? Just because of the need of convenience, or more deeply, the superficial understanding of environmental consciousness. And furthermore, the third bad behavior, as the least intolerable one, is the problem of queuing. Though there is an old saying: first come, first served, public seems not willing to obey it. Jumping the queue is widely seen everywhere. Worse still, sometimes there is even no queue but a noisy crowd, pushing and jostling as if they were enemies. It is sad that bad public behavior is far more than these. But I am strongly assured it will get better. All we need is time and education. Root the correct idea into public’s mind is particularly important. The Audience is not only the present generation, but the generation to come. 工信1409 叶欣
Organizational Behavior Part1: Introduction to Organizational Behavior Chapter1:organizational behavior overview Organizational behavior (OB) is a field of study devoted to understanding, explaining, and ultimately improving the attitudes and behaviors of individuals and groups in organizations. OB source: 1.Industrial and organizational psychology 2. Social psychology 3. Sociology 4. Anthropology 5. Economics Integrative model of organizational behavior 1.Individual outcomes: Job performance;Organizational commitment 2.Individual mechanisms: Job satisfaction; stress; motivation; trust,justice and ethics; Learning and decision making Individual characteristics: Personality; cultural values; ability Group mechanisms: Teams; leaderships
behavior的用法和辨析 今天和大家一起学习一下behavior的用法，快来一起学习吧，下面就和大家分享，来欣赏一下吧。 词汇精选：behavior的用法和辨析 一、详细释义： n. 行为;举止;态度[U] 例句： Their behavior towards me shows that they do not like me. 他们对我的举止说明他们不喜欢我。 例句： His strange behavior made the police suspicious. 他不寻常的举止引起了警察的怀疑。 (机器等的)运转状态，性能[U]
例句： The aircrafts behavior was satisfactory on its first test flight. 那架飞机在第一次试飞时运转情况令人满意。 (事物的)反应，变化;作用[U] 二、词义辨析： behavior,conduct,manner 这些名词均含有“行为，举止”之意。behavior普通用词，侧重指某人在特定场合对他人或在他人面前的行为、举止。conduct较正式用词，泛指某人的行动。侧重根据社会道德标准和责任感。manner主要用来指人的习惯行为。 三、相关短语： behavior therapy 行为疗法 behavior modification 行为修正 四、参考例句： Her behavior enraged him.
她的行为激怒了他。 Your behavior frenzied me. 你的行为使我愤怒。 Her odd behavior defies understanding. 她的古怪行为无法理解。 Her behavior alienated her friends. 她的行为使自己跟朋友们疏远了。His behavior borders upon madness. 他的行为几乎算得上疯狂。 My behavior is above reproach. 我的做法无可厚非。 Her behavior was beyond reproach. 她的行为无可指责。 She has a spontaneous behavior . 她的举止很自然。 His behavior was beyond bearing.
International customer behavior Abstract: Consumer buying behavior refers to the people to meet the needs and desires and looking for, select, purchase, use, evaluation and disposal of products, services, the process of intervention activities, including consumer's subjective psychological activities and objective material activity two aspects. Consumers' purchasing behavior is composed of a series of links, element complete process. In this process, the purchase decision in the central position; Decisions correctly or not directly decided to purchase behavior, pointing to the way and the size of the utility. Keywords: behavior, consumer, purchase, process Consumer buying behavior refers to the people in order to meet the person, family life need or enterprise in order to meet the needs of production, when buying a hobby products or services of all kinds of behavior, and the purchase decision process. Consumer buying behavior, diversity, dynamic and interactive volatility, impulsivity, trading, etc. Strictly speaking, the customer purchasing behavior is composed of a series of links, namely customer purchasing behavior is derived from the purchase decision-making process in the system, and under the influence of internal and external factors. Customer purchase behavior of complex, puts forward more on sales staff, a higher challenge. For excellent sales staff, to master the customer buying decision process and understand the factors that affect the customer to make a buying decision and so on all aspects, such as critical. Procurement is the buyer in accordance with the requirements, in a reasonable time, with the most reasonable price to buy the best goods; We can learn that in the process of buyers to purchase, there are a few points are requires consideration of sales people; Is first buyers demand, that is to say, you should be very good to know the requirement of the buyer; Secondly, time, time is a limited resource, you need to ensure a good delivery date; Third: the prices or costs. In flooded with goods, can you guarantee to the buyer to provide a competitive price, if you can't, so if you can provide other high additional value? Buyers in the purchase process, which can be roughly divided into two kinds: one kind is looking for a particular product; Is a kind of choice to cooperation supplier; Your cooperation buyers is to belong to that kind of situation? A type of buyer you are looking for that? How to make the targeted sales, these are worth each export friends thinking about;
组织行为学 题型剖析： 选择题（15*1=15）、多选题（5*2=10）名词解释（5*3=15）、简答题（5*6=30）、论述题（10*1=10）、案例分析（20*1=20） 知识点： 1、如何利用工作团队来增强团队的互动？ 【解析】工作团队：是由一些知识技能互补、彼此承诺完成一项共同目标或是一系列绩效目标的成员组成的特殊群体，每个成员都负有共同的责任。 高效团队：是指成熟的团队，发展目标明确，完成任务前后对比效果明显增加，团队成员在有效的领导下相互信任、沟通良好、积极协同工作的团队。 高效团队的特征：①共同目标②相关技能③相互信任④一直承诺⑤良好的沟通⑥高效的领导高效团队的建设途径和技巧：①制定共同的团队目标②确定不同能力的成员③创建互信的环境（坚持的原则：公开、公正、公平；有效的沟通；不能任人为亲。）④改进领导方式和团队结构 ⑤正确的绩效评估和薪酬体系。 2、如何运用决策提高领导的有效性？ 【解析】领导决策是领导者的基本职能和首要任务，是指领导者为实现领导活动目标，组织制定多种决策方案，从中选择并执行最佳方案的全部活动过程。 领导决策具有预测性、目的性、选择性、关键性、风险性等特点。 决策领导的基本原则：①信息准确性原则②可行性原则③系统分析原则④对比分析原则 ⑤集体决策原则 领导决策的基本程序：①发现问题②确定目标③拟定方案④评估方案⑤方案优选⑥组织实施 ⑦追踪反馈 群体决策的方法：①头脑风暴法②德尔菲法③案例提前分析法④提喻法 决策的民主化的条件和途径：领导者要具备民主作风和素质、建立起决策参与民主机制、实现决策制定程序和执行程序民主化、建立决策监督机制接受群众监督决策。 3、组织设计应遵循的原则？ 【解析】原则：①专业化分工原则②统一指挥原则③控制幅度原则④权责对等原则⑤柔性经济原则 4、内聚力的定义，作用，影响因素？ 【解析】定义：群体凝聚力又称群体内聚力，它是群体成员施加各种影响，使之在群体内积极活动和拒绝离开群体的全部力量的总和，是群体对个体的吸引力 作用：①内聚力和工作绩效的关系②内聚力与员工满意度的关系③内聚力与员工个人的成长1、如果群体目标与组织大目标一致，且群体成员对组织大目标持支持态度时，凝聚力高的群体比凝聚力低的群体更为有效。 2、如果群体目标与组织大目标不相一致，且群体成员们又不支持组织大目标时，则群体的凝聚力越高，完成组织大目标的工作效率就会越低。 影响：①成员一致性②群体规模地位③与外部的关系④成员对群体的依赖⑤奖酬体制 ⑥群体的绩效⑦信息沟通⑧领导方式 5、期望理论有什么作用？ 【解析】期望理论：（人的固定要求决定了他的行为以及行为方式）只有当人们认为存在实现预期目标的可能性，并且实现这种目标又是非常重要的时候，他们的激励程度或动机水平才会最大。也就是说决定行为动机的因素有两个，即期望与效价。用公式表示为：激励强度=期望值×效价。 作用：总的来讲：具有一定的导向作用。期望值越高，表明人们对努力与绩效之间关系的相信程度越大，人越容易做出努力的决断，反之同理。有利于提高员工的工作绩效。
《Consumer Behavior》课程教学大纲 一、课程基本信息 课程代码：050873 课程名称：消费者行为学（全英） 英文名称：Consumer Behavior 课程类别：专业课 学时：48 学分：3 适用对象:金融学（“2+2”实验班）本科生 考核方式：考试 先修课程：宏观经济学 二、课程简介 消费者行为学是研究个人或组织选择、购买、使用或淘汰产品、服务、思想或经验以满足其需求的整个过程的学科。具体而言，本课程介绍消费者行为学的有关基本理论，包括消费者个人的认知、学习和记忆、动机、情境、价值观、自我等。同时对消费者决策过程、影响消费者决策和行为的各种因素包括态度、组织、社会媒体、社会阶层和生活方式等进行了分析和探讨。 Consumer behavior is the study of the processes involved when individuals or groups select,purchase,use,or dispose of products,services,ideas,or experiences to satisfy needs and desires.Specifically,this course introduces the basic theories of perception,learning and memory,motivation,global values and the self of consumers as individuals.It also deals with the process of decision making,how different factors including attitudes,groups,social media,social class and lifestyls affect decision making and consumer behavior. 三、课程性质与教学目的 消费者行为学是金融学（“2+2”实验班）本科生的专业必修课。通过课程学习，让学生能够掌握消费者行为学的基本理论，包括消费者个体的自我、知觉、学习和记忆、动机和价值观，消费者的决策过程、购买与处置行为，消费者决策如何受到自身态度、外部群体、社会化媒体、生活方式及文化等因素的影响等，并能够将理论与中国的实际相结合。 四、教学内容及要求 Chapter1Buying,Having,and Being:An Introduction to Consumer Behavior （一）目的与要求
Composites复合任务 Sequence顺序任务/序列任务 The Sequence task is similar to an "and" operation. It will return Failure as soon as one of its child tasks return Failure. If a child task returns Success then it will sequentially run the next task. If all child tasks return Success then it will return Success. Sequence任务类似于“and”操作。一旦其子任务之一返回Failure，它将返回Failure。如果子任务返回Success，那么它将按顺序执行下一个任务。如果所有子任务返回Success，那么它将返回Success。 Selector选择任务 The Selector task is similar to an "or" operation. It will return Success as soon as one of its child tasks return Success. If a child task returns Failure then it will sequentially run the next task. If no child task returns Success then it will return Failure. Selector任务类似于“or”操作。一旦其子任务之一返回Success，它将返回Success。如果子任务返回Failure，则它将按顺序执行下一个任务。如果没有子任务返回Success，则它将返回Failure。 Parallel并行任务 Similar to the Sequence task, the Parallel task will run each child task until a child task returns Failure. The difference is that the Parallel task will run all of its children tasks simultaneously versus running each task one at a time. Like the Sequence class, the Parallel task will return Success once all of its children tasks have return Success. If one tasks returns Failure the Parallel task will end all of the child tasks and return Failure. 与Sequence任务类似，Parallel任务将运行每个子任务，直到子任务返回Failure。不同的是，并行任务将同时运行其所有子任务，而不是每次运行一个任务。像Sequence任务一样，当所有的子任务都返回Success时，Parallel任务将返回Success。如果一个任务返回Failure，Parallel任务将结束所有子任务并返回Failure。 Parallel Selector 并行选择任务 Similar to the Selector task, the Parallel Selector task will return Success as soon as a child task returns Success. The difference is that the Parallel Selector task will run all of its children tasks
大学生英语演讲 Civilized behavior 大学生英语演讲范文：Civilized behavior A man will not render good services to his country if he can do nothing civilized ,for in proportion as he respect himself while he respects his country. The civilized behavior is the birthplace of true patriotism. It is the secret of social welfare and national greatness .It’s the basis and origin of civilization. Civilized behavior is not a matter of boast or the quality of imagination; it’s the matter of down –to- earth principle. It’s the freshness of the deep springs of life. Civilized behavior means a temperamental predominance of responsibility over superficiality, of the appetite for initiation over the love of conformity. We do not choose to be born. We do not choose our parents. We do not choose our historical epoch, the country of our birth or the immediate circumstances of our upbringing. We do not, most of us, choose to die; nor do we choose the time or conditions of our death. But within all
Part 1 Introduction Chapter 1 Introduction 1. Which of the following decision should be considered legitimate topics of concern in the study of consumer behavior: (a). selecting a college (b). purchasing a life insurance policy (c). Smoking a cigarette (d).selecting a church to join (e).selecting a dentist (f).visiting an auto showroom to see new models (g).purchasing a college textbook 2. Consumption behavior begins with the step of: (a). purchasing process (b). Information search and evaluation (c). Problem recognition (d). Postpurchasing behavior 3. ____occurs when an individual perceives a difference between an ideal state of affairs and the actual state at any given moment. (a). Problem recognition (b).search (c).alternative evaluation (d).choice (e).outcome 4. The research scope of consumer behavior includes: (a). Psychological characteristics of consumer such as needs, motives, personality, attitudes and general effect of such psychological process as perception and learning on consumer behavior (b).Application of psychology research accomplishments on marketing strategies such as influences of such factors as brand, package, price, advertisement on consumer behavior (c). Family, social group, social class, culture, subculture influences on consumer purchasing 5. From which of the following we can see the research of consumer behavior is being widened? (a). From the past research of “customer” to present “consumer” (b). From the simple describe of the relationship of variables to the study of the cause and effect relationship, and performing laboratory research of many problems (c).The work abstract level improved Many consumer theory models are put forward. (d).From static concept to dynamic concept 6. What are the two parts psychology includes: (a). Psychology process (b). Psychology characteristic (c).recognition and perception (d).personality consciousness
Immoral Behavior in Public Write a composition entitled Immoral Behavior in Public. You should write at least 120 words according to the outline given below in Chiness. 1.我们经常在公共场合见到各种不文明的行为； 2.这些不文明的行为会有哪些影响； 3.我们应该怎样改善这种现象。 英语四级作文写作步骤构思： 步骤1： 审题：这是一篇以公共文明为主题的说明文。 步骤2： 引入话题：指出不文明现象在社会的广泛存在； 展开话题：阐述不文明现象两方面的主要影响； 话题结论：如何改变这种情况，并提出自己的观点。 Immoral Behavior in Public Immoral behaviors in public are everywhere. One can find people spitting on overpasses, picking flowers in parks and jumping e queue while waiting in banks. 公众场合的不文明行为比比皆是。你会发现，人们在天桥上随地吐痰，在公园里摘花，在银行排队等候时插队。引入话题:指出不文明现象在社会的广泛存在； Immoral behaviors in public bring about a series of problems. First of all, one of the most serious ones is that it may exert a negative impact on our sense of social responsibility. ln addition, if we keep turning a blind eye to the other people's feelings, we, in turn, will be disrespected someday. 公众场合的不文明行为会造成一连串的问题。首先，最严重的问题就是会降低我们的社会责任感。此外，如果我们继续忽视他人的感受，终有一天我们自己也会失去他人的尊重。 To get rid of this phenomenon is certainly not easy. I propose that we should punish those people who fail to respect the common good. What's more, stricter policies for this should be made to correct this phenomenon as soon as possible. (121words) 消除这种现象绝非一件容易的事。我的建议是，我们应该严惩那些不尊重大众利益的人。此外，需采取更严格的政策，尽快消除这种不良的风气。