In order to explore the mechanism of improving the surface wettability of low-energy polytetrafluoroethylene(PTFE)by new extended surfactants,five kinds of extended anionic surfactants with different numbers of oxypro...In order to explore the mechanism of improving the surface wettability of low-energy polytetrafluoroethylene(PTFE)by new extended surfactants,five kinds of extended anionic surfactants with different numbers of oxypropylene(PO)and oxyethylene(EO),octadecyl-(PO)_(m)-(EO)_(n)-sodium carboxylate(C_(18)PO_(m)EO_(n)C,m=5,10,15,n=5,10,15),were studied.The surface tension and contact angle of C_(18)PO_(m)EO_(n)C solution with different concentrations were measured,and the adhesion tension,PTFE-water interfacial tension,and adhesion work were calculated.It was found that the extended surfactant molecules adsorb on the surface of the solution and the PTFE-liquid interface simultaneously when the concentration is lower than the critical micelle concentration(cmc),and there was a linear relationship between surface tension and adhesion tension.The adsorption amount of C_(18)PO_(m)EO_(n)C at the PTFE-water interface was significantly lower than that on the surface of the solution.As the concentration increases above cmc,semi-micelle aggregates on the surface of PTFE are formed by C_(18)PO_(m)EO_(n)C molecules through hydrophobic interaction,and the hydrophilic group faces the solution to modify the surface of PTFE with high efficiency.展开更多
The floatability of different crystalline structures of pyrrhotite(monoclinic and hexagonal) was studied.It is shown that the floatability of monoclinic and hexagonal has obvious difference,and that the flotation reco...The floatability of different crystalline structures of pyrrhotite(monoclinic and hexagonal) was studied.It is shown that the floatability of monoclinic and hexagonal has obvious difference,and that the flotation recovery of monoclinic pyrrhotite is larger than that of hexagonal pyrrhotite using different collectors.When butyl dithiophosphate is used as the collector,the recovery is larger than that by sodium butyl xanthate and sodium diethyl dithiocarbamate.At the pH values ranging from 6 to 9,monoclinic pyrrhotite can be floated well,and the flotation recovery is higher than 90%.Monoclinic and hexagonal pyrrhotites are more easily activated by Cu2+ in acidic conditions than in alkaline conditions.But Cu2+ cannot activate hexagonal pyrrhotite using sodium diethyldithiocarbamate as the collector.By the measurement of contact angle,it is indicated that monoclinic and hexagonal pyrrhotites float well and are easily activated by Cu2+ when dithiophosphate is used as the collector.Using sodium diethyl dithiocarbamate as a collector,the relationship between potential and pH range for pyrrhotite flotation is established.At pH 5,the optimal potential range for flotation of monoclinic pyrrhotite is about 125-580 mV(vs SHE),with the maximum flotation occurring at about 350 mV(vs SHE);the optimal potential range for flotation of hexagonal pyrrhotite is 200?580 mV(vs SHE),with the maximum flotation occurring at about 300 mV(vs SHE).展开更多
This work presents a method to solve the weak solubility of zinc chloride(ZnCl_2) in the ethanol by adding some reasonable water into an ethanol electrolyte containing ZnCl_2 and myristic acid(CH_3(CH_2)_(12)COOH).A r...This work presents a method to solve the weak solubility of zinc chloride(ZnCl_2) in the ethanol by adding some reasonable water into an ethanol electrolyte containing ZnCl_2 and myristic acid(CH_3(CH_2)_(12)COOH).A rapid one-step electrodeposition process was developed to fabricate anodic(2.5 min) and cathodic(40 s) superhydrophobic surfaces of copper substrate(contact angle more than 150°) in an aqueous ethanol electrolyte.Morphology,composition,chemical structure and superhydrophobicity of these superhydrophobic surfaces were investigated by SEM,FTIR,XRD,and contact angle measurement,respectively.The results indicate that water ratio of the electrolyte can reduce the required deposition time,superhydrophobic surface needs over 30 min with anhydrous electrolyte,while it needs only 2.5 min with electrolyte including 10 mL water,and the maximum contact angle of anodic surface is 166° and that of the cathodic surface is 168°.Two copper electrode surfaces have different reactions in the process of electrodeposition time,and the anodic copper surface covers copper myristate(Cu[CH_3(CH_2)_(12)COO]_2) and cupric chloride(CuCl);while,zinc myristate(Zn[CH_3(CH_2)_(12)COO]_2) and pure zinc(Zn) appear on the cathodic surface.展开更多
The use of polymer materials as electrical insulators on transmission and distribution lines has been increasing such as epoxy resin.Several advantages of using epoxy resin as an insulating material are its low densit...The use of polymer materials as electrical insulators on transmission and distribution lines has been increasing such as epoxy resin.Several advantages of using epoxy resin as an insulating material are its low density,better dielectric properties,and epoxy resin has higher volume resistivity than that of the glass and porcelain.However,epoxy resin has some disadvantages when it is used in tropical areas concerning with the humidity,high ultraviolet radiation, acid rain and effects of contaminants.Consequently,insulator surface will be easily damaged due to electrical tracking,which is indicated by the surface tracking.In this paper,the surface tracking on epoxy resin compound with silicon rubber has been investigated.The test was done based on the method of Inclined-Planed Tracking(IPT) IEC 587:1984 with NH_4C1 as contaminant.The test materials used were epoxy resins based on Diglycidyl Ether of Bisphenol A(DGEBA) and Methaphenylene Diamine(MPDA) compound with silicon rubber(SiR) with the dimensions of 50 mm×120 mm and the thickness of 6 mm.The flow rate of contaminant was 0.3 mL/min.The 3.5 kV AC high voltage 50 Hz was applied to the top electrodes.The experimental results show that the contact angle of hydrophobic was affected by compound of silicon rubber.The surface tracking,time to tracking and discharge current were affected by applied voltage,contamination and contact angle.By using micro-cameras,the surface damage was detected. The severest damaged sample surface on a sample had small contact angle.On the other hand,samples with the greatest contact angle needed longer time to have surface damage in the surface discharge.This shows that it is more difficult for large contact angle samples or more hydrophobic to have surface discharge.Epoxy resin compound with silicon rubber has contact angle of hydrophobic greater than epoxy resin without silicon rubber.展开更多
Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dyna...Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dynamics and lattice Boltzmalm method （LBM）. By taking the effect of molecule force in droplet and the wall surface on liquid film into account, the changing law of contact angle with different surface tensions was analyzed on glass and aluminum foil surfaces. Compared with experimental results, the standard deviation by using LBM is less than 0.5°, which validates the feasibility of LBM simulation on the dynamic process of liquid film spreading. In addition, oscillations are discovered both at the initial and end phases. The phenomenon of retraction is also found and the maximum retraction angle is 7.58°. The obtained result shows that the retraction is proved to be correlative with precursor film by tracking the volume change of liquid film contour. Furthermore, non-dimensional coefficient 2 is introduced to measure the liquid film retraction capacity.展开更多
Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study th...Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study the effect ofb on the wettability of the rough surface, the effects of apparent contact angle （CA） and sliding angle （a） of the droplet on the rough surface were measured with the contact angle meter. The results show that the experimental values of CA well agree with the classical wetting theory and a decreases with the increase of b. Two drop shapes exist on the samples＇ surface, corresponding to the Cassie state and the Wenzel state respectively. The contact state in which a drop would settle depends typically on the size of b. On the role of gravitation, the irreversible transition of a drop from Cassie state to Wenzel state should occur at a certain space of the square pillars. Since the transition has implications on the application of super-hydrophobic rough surfaces, theoretically, the prediction of wetting state transition on square pillar array micro-structured surfaces provides an intuitionistic guidance for the design of steady superhydrophobic surfaces.展开更多
Electrokinetic and contact angle measurements were used to discuss the interfacial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobacillus ferrooxidans were obtained...Electrokinetic and contact angle measurements were used to discuss the interfacial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobacillus ferrooxidans were obtained by calculating according to formula of Young＇s equation and contact angle measurements. The results show that surface energy of thiobacillus ferrooxidans is much higher than that of pyrite mineral, and the reaction of pyrite mineral with thiobacillus ferrooxidans causes the reduction of the pyrite surface energy. The interfacial interaction energies between pyrite mineral and thiobaciUus ferrooxidans were also obtained based on polar interfacial interaction theory and electrokinetic and contact angle measurements. The thermodynamics approach only considering Lifshitz-van der Waals and Lewis acid-base interaction fails to explain the adhesion behavior of the bacteria, but the extended Derjaguin-Landan-Verwey-Overbeek theory concerning Lifshitz-van der Waals and Lewis acid-base and the electrostatic can exactly predict interfacial interaction.展开更多
To reveal the potential effect of surfactant on improving surface wettability of copper ore,the droplet spreading behavior of sulfuric acid solution contained surfactant was visualized using high-speed camera and an i...To reveal the potential effect of surfactant on improving surface wettability of copper ore,the droplet spreading behavior of sulfuric acid solution contained surfactant was visualized using high-speed camera and an image processing method,and the solid-liquid interaction was discussed in this study.The results show that liquid surface tension and ore surface roughness are the main factors affecting surface wettability.The effect of sulfuric acid solution concentration and surfactants on the surface wettability of ore is revealed via quantitative spreading area,spreading coefficient,and contact angle.The results of droplet spreading experiment show that the higher concentration of surfactant and sulfuric acid solution result in improving the wettability of ore,spreading coefficient,and decreasing contact angle.The“leaching reaction coefficient”and“surface activity coefficient”are introduced to modify the mathematical expression of the equilibrium contact angle.展开更多
The effects of surface energy on phase change of water vapor at initial stage of frost growth were studied to find an effective method of restraining frost growth.The mechanism of restraining frost growth by low energ...The effects of surface energy on phase change of water vapor at initial stage of frost growth were studied to find an effective method of restraining frost growth.The mechanism of restraining frost growth by low energy surface(bigger contact angle) was analyzed based on crystal growth theory.Then,the phase change of water vapor and the process of frost growth on the copper and wax energy surfaces were observed using microscope.The results indicate that it is difficult for wax surface(low energy surface),on which there are still water droplets at 100 s,to form critical embryo,so frost growth can be restrained in a way.Water formation,droplet growth,ice formation and dendritic ice growth processes happen on both surfaces,ordinally.But the ice beads,with larger average diameter and sparse distribution on the wax surface,form later(at about 300 s) than that on the copper surface,and the dendritic ice also appears later.All of these support that ice crystal formation and dendritic crystal growth at initial stage of frost growth can be retarded on the low energy surface.展开更多
In order to improve the surface hydrophobicity, silicone rubber （SIR） samples were exposed to CF4 radio frequency （RF） capacitively coupled plasma （CCP）. Attenuated total reflection Fourier transform infrared （...In order to improve the surface hydrophobicity, silicone rubber （SIR） samples were exposed to CF4 radio frequency （RF） capacitively coupled plasma （CCP）. Attenuated total reflection Fourier transform infrared （ATR-FTIR） spectrum and X-ray photoelectron spectroscopy （XPS） were used to observe the variation of the functional groups of the modified SIR. Static contact angle （SCA） was employed to estimate the change of hydrophobicity of the modified SIR. The surface energy of SIR is reduced largely from 27.37 mJ/m^2 of original SIR sample to 2.94 mJ/m^2 of SIR sample treated by CF4 CCP modification at RF power of 200 W for a treatment time of 5 rnin. According to the XPS, ATR-FTIR and surface energy analysis, it is suggested that the improvement of hydrophobicity on the modified SIR surface is mainly ascribed to the decrease of surface energy, which is caused by the cooperation of the fluosilicic structure of Si--F or Si--F2 and the fluoric groups of C--CFn induced by the methyl replacement reaction and residual methyl groups of SIR surface.展开更多
文摘In order to explore the mechanism of improving the surface wettability of low-energy polytetrafluoroethylene(PTFE)by new extended surfactants,five kinds of extended anionic surfactants with different numbers of oxypropylene(PO)and oxyethylene(EO),octadecyl-(PO)_(m)-(EO)_(n)-sodium carboxylate(C_(18)PO_(m)EO_(n)C,m=5,10,15,n=5,10,15),were studied.The surface tension and contact angle of C_(18)PO_(m)EO_(n)C solution with different concentrations were measured,and the adhesion tension,PTFE-water interfacial tension,and adhesion work were calculated.It was found that the extended surfactant molecules adsorb on the surface of the solution and the PTFE-liquid interface simultaneously when the concentration is lower than the critical micelle concentration(cmc),and there was a linear relationship between surface tension and adhesion tension.The adsorption amount of C_(18)PO_(m)EO_(n)C at the PTFE-water interface was significantly lower than that on the surface of the solution.As the concentration increases above cmc,semi-micelle aggregates on the surface of PTFE are formed by C_(18)PO_(m)EO_(n)C molecules through hydrophobic interaction,and the hydrophilic group faces the solution to modify the surface of PTFE with high efficiency.
基金Project(50774094) supported by the National Natural Science Foundation of China
文摘The floatability of different crystalline structures of pyrrhotite(monoclinic and hexagonal) was studied.It is shown that the floatability of monoclinic and hexagonal has obvious difference,and that the flotation recovery of monoclinic pyrrhotite is larger than that of hexagonal pyrrhotite using different collectors.When butyl dithiophosphate is used as the collector,the recovery is larger than that by sodium butyl xanthate and sodium diethyl dithiocarbamate.At the pH values ranging from 6 to 9,monoclinic pyrrhotite can be floated well,and the flotation recovery is higher than 90%.Monoclinic and hexagonal pyrrhotites are more easily activated by Cu2+ in acidic conditions than in alkaline conditions.But Cu2+ cannot activate hexagonal pyrrhotite using sodium diethyldithiocarbamate as the collector.By the measurement of contact angle,it is indicated that monoclinic and hexagonal pyrrhotites float well and are easily activated by Cu2+ when dithiophosphate is used as the collector.Using sodium diethyl dithiocarbamate as a collector,the relationship between potential and pH range for pyrrhotite flotation is established.At pH 5,the optimal potential range for flotation of monoclinic pyrrhotite is about 125-580 mV(vs SHE),with the maximum flotation occurring at about 350 mV(vs SHE);the optimal potential range for flotation of hexagonal pyrrhotite is 200?580 mV(vs SHE),with the maximum flotation occurring at about 300 mV(vs SHE).
基金Projects(11304243,11102164)supported by the National Natural Science Foundation of ChinaProject(2014JQ1039)supported by the Natural Science Foundation of Shannxi Province,China+3 种基金Project(12JK0966)supported by the Shaanxi Provincial Education Department,ChinaProject(2013QDJ037)supported by the Xi’an University of Science and Technology Dr Scientific Research Fund,ChinaProject(3102016ZY027)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(13GH014602)supported by the Program of New Staff and Research Area Project of NPU,China
文摘This work presents a method to solve the weak solubility of zinc chloride(ZnCl_2) in the ethanol by adding some reasonable water into an ethanol electrolyte containing ZnCl_2 and myristic acid(CH_3(CH_2)_(12)COOH).A rapid one-step electrodeposition process was developed to fabricate anodic(2.5 min) and cathodic(40 s) superhydrophobic surfaces of copper substrate(contact angle more than 150°) in an aqueous ethanol electrolyte.Morphology,composition,chemical structure and superhydrophobicity of these superhydrophobic surfaces were investigated by SEM,FTIR,XRD,and contact angle measurement,respectively.The results indicate that water ratio of the electrolyte can reduce the required deposition time,superhydrophobic surface needs over 30 min with anhydrous electrolyte,while it needs only 2.5 min with electrolyte including 10 mL water,and the maximum contact angle of anodic surface is 166° and that of the cathodic surface is 168°.Two copper electrode surfaces have different reactions in the process of electrodeposition time,and the anodic copper surface covers copper myristate(Cu[CH_3(CH_2)_(12)COO]_2) and cupric chloride(CuCl);while,zinc myristate(Zn[CH_3(CH_2)_(12)COO]_2) and pure zinc(Zn) appear on the cathodic surface.
文摘The use of polymer materials as electrical insulators on transmission and distribution lines has been increasing such as epoxy resin.Several advantages of using epoxy resin as an insulating material are its low density,better dielectric properties,and epoxy resin has higher volume resistivity than that of the glass and porcelain.However,epoxy resin has some disadvantages when it is used in tropical areas concerning with the humidity,high ultraviolet radiation, acid rain and effects of contaminants.Consequently,insulator surface will be easily damaged due to electrical tracking,which is indicated by the surface tracking.In this paper,the surface tracking on epoxy resin compound with silicon rubber has been investigated.The test was done based on the method of Inclined-Planed Tracking(IPT) IEC 587:1984 with NH_4C1 as contaminant.The test materials used were epoxy resins based on Diglycidyl Ether of Bisphenol A(DGEBA) and Methaphenylene Diamine(MPDA) compound with silicon rubber(SiR) with the dimensions of 50 mm×120 mm and the thickness of 6 mm.The flow rate of contaminant was 0.3 mL/min.The 3.5 kV AC high voltage 50 Hz was applied to the top electrodes.The experimental results show that the contact angle of hydrophobic was affected by compound of silicon rubber.The surface tracking,time to tracking and discharge current were affected by applied voltage,contamination and contact angle.By using micro-cameras,the surface damage was detected. The severest damaged sample surface on a sample had small contact angle.On the other hand,samples with the greatest contact angle needed longer time to have surface damage in the surface discharge.This shows that it is more difficult for large contact angle samples or more hydrophobic to have surface discharge.Epoxy resin compound with silicon rubber has contact angle of hydrophobic greater than epoxy resin without silicon rubber.
基金Project(U1261107)supported by the National Natural Science Foundation of China
文摘Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dynamics and lattice Boltzmalm method （LBM）. By taking the effect of molecule force in droplet and the wall surface on liquid film into account, the changing law of contact angle with different surface tensions was analyzed on glass and aluminum foil surfaces. Compared with experimental results, the standard deviation by using LBM is less than 0.5°, which validates the feasibility of LBM simulation on the dynamic process of liquid film spreading. In addition, oscillations are discovered both at the initial and end phases. The phenomenon of retraction is also found and the maximum retraction angle is 7.58°. The obtained result shows that the retraction is proved to be correlative with precursor film by tracking the volume change of liquid film contour. Furthermore, non-dimensional coefficient 2 is introduced to measure the liquid film retraction capacity.
基金Project(50435030) supported by the National Natural Science foundation of ChinaProject supported by the Program for New Century Excellent Talents in Chinese University Project(GZ080010) supported by the Open Research Fund Program of Jiangsu Province Key Laboratory for Photon Manufacturing Science and Technology
文摘Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study the effect ofb on the wettability of the rough surface, the effects of apparent contact angle （CA） and sliding angle （a） of the droplet on the rough surface were measured with the contact angle meter. The results show that the experimental values of CA well agree with the classical wetting theory and a decreases with the increase of b. Two drop shapes exist on the samples＇ surface, corresponding to the Cassie state and the Wenzel state respectively. The contact state in which a drop would settle depends typically on the size of b. On the role of gravitation, the irreversible transition of a drop from Cassie state to Wenzel state should occur at a certain space of the square pillars. Since the transition has implications on the application of super-hydrophobic rough surfaces, theoretically, the prediction of wetting state transition on square pillar array micro-structured surfaces provides an intuitionistic guidance for the design of steady superhydrophobic surfaces.
基金Project(2004CB619204) supported by the National Basic Research Program of ChinaProject(2002) supported by the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions, China
文摘Electrokinetic and contact angle measurements were used to discuss the interfacial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobacillus ferrooxidans were obtained by calculating according to formula of Young＇s equation and contact angle measurements. The results show that surface energy of thiobacillus ferrooxidans is much higher than that of pyrite mineral, and the reaction of pyrite mineral with thiobacillus ferrooxidans causes the reduction of the pyrite surface energy. The interfacial interaction energies between pyrite mineral and thiobaciUus ferrooxidans were also obtained based on polar interfacial interaction theory and electrokinetic and contact angle measurements. The thermodynamics approach only considering Lifshitz-van der Waals and Lewis acid-base interaction fails to explain the adhesion behavior of the bacteria, but the extended Derjaguin-Landan-Verwey-Overbeek theory concerning Lifshitz-van der Waals and Lewis acid-base and the electrostatic can exactly predict interfacial interaction.
基金Project(LJ2020JCL002)supported by Education Commission of Liaoning Province,ChinaProject(51604138)supported by the National Natural Science Foundation of China。
文摘To reveal the potential effect of surfactant on improving surface wettability of copper ore,the droplet spreading behavior of sulfuric acid solution contained surfactant was visualized using high-speed camera and an image processing method,and the solid-liquid interaction was discussed in this study.The results show that liquid surface tension and ore surface roughness are the main factors affecting surface wettability.The effect of sulfuric acid solution concentration and surfactants on the surface wettability of ore is revealed via quantitative spreading area,spreading coefficient,and contact angle.The results of droplet spreading experiment show that the higher concentration of surfactant and sulfuric acid solution result in improving the wettability of ore,spreading coefficient,and decreasing contact angle.The“leaching reaction coefficient”and“surface activity coefficient”are introduced to modify the mathematical expression of the equilibrium contact angle.
基金Project(50376052) supported by the National Natural Science Foundation of ChinaProject(307013) supported by the Key Project of Chinese Ministry of EducationProject(2008BAJ12B02) supported by the National Science and Technology Pillar Program in the 11th Five-Year Plan Period
文摘The effects of surface energy on phase change of water vapor at initial stage of frost growth were studied to find an effective method of restraining frost growth.The mechanism of restraining frost growth by low energy surface(bigger contact angle) was analyzed based on crystal growth theory.Then,the phase change of water vapor and the process of frost growth on the copper and wax energy surfaces were observed using microscope.The results indicate that it is difficult for wax surface(low energy surface),on which there are still water droplets at 100 s,to form critical embryo,so frost growth can be restrained in a way.Water formation,droplet growth,ice formation and dendritic ice growth processes happen on both surfaces,ordinally.But the ice beads,with larger average diameter and sparse distribution on the wax surface,form later(at about 300 s) than that on the copper surface,and the dendritic ice also appears later.All of these support that ice crystal formation and dendritic crystal growth at initial stage of frost growth can be retarded on the low energy surface.
基金Project(05JT1034) supported by the Plan of Science and Technology Bureau of Hunan Province,China
文摘In order to improve the surface hydrophobicity, silicone rubber （SIR） samples were exposed to CF4 radio frequency （RF） capacitively coupled plasma （CCP）. Attenuated total reflection Fourier transform infrared （ATR-FTIR） spectrum and X-ray photoelectron spectroscopy （XPS） were used to observe the variation of the functional groups of the modified SIR. Static contact angle （SCA） was employed to estimate the change of hydrophobicity of the modified SIR. The surface energy of SIR is reduced largely from 27.37 mJ/m^2 of original SIR sample to 2.94 mJ/m^2 of SIR sample treated by CF4 CCP modification at RF power of 200 W for a treatment time of 5 rnin. According to the XPS, ATR-FTIR and surface energy analysis, it is suggested that the improvement of hydrophobicity on the modified SIR surface is mainly ascribed to the decrease of surface energy, which is caused by the cooperation of the fluosilicic structure of Si--F or Si--F2 and the fluoric groups of C--CFn induced by the methyl replacement reaction and residual methyl groups of SIR surface.
