Exposing waxy oils to an electric field may significantly improve their cold flowability.Our previous study has shown that interfacial polarization,i.e.,charged particle accumulation on the wax particle surface,is the...Exposing waxy oils to an electric field may significantly improve their cold flowability.Our previous study has shown that interfacial polarization,i.e.,charged particle accumulation on the wax particle surface,is the primary mechanism of the electrorheological behavior of waxy oils.However,the way that charged particles interact with wax particles under an electric field remains unknown.In this study,we found no viscosity and impedance change for two waxy crude oils after their exposure to a high-voltage electric field.However,the yield stresses were reduced obviously.We thus proposed that the collision of colloidal particles such as resins and asphaltenes with the wax particles could be an essential mechanism that the wax particle structure was weakened.To verify this hypothesis,a series of ad hoc experiments were carried out,i.e.,by performing electrorheological tests on model waxy oils containing additives removable under an electric field,including electrically-neutral colloidal particles(Fe3O4),charged colloidal particles(resins),and oil-soluble electrolyte(C22H14CoO4),respectively,and demonstrated that upon application of a high-voltage electric field,charged particles in a waxy oil may move and thus collide with wax particles,and consequently adhere to the wax particle surface.The particle collision results in damage to the wax particle network,and the electrostatic repulsion arising from the adhesion of the charged particle on the wax particle diminishes attraction between wax particles.This study clarifies the process of interfacial polarization.展开更多
Traditional dielectric electrorheological fluid(ER)is based on the interaction of dielectric particle polarization,and the yield stress is low,which cannot meet the application requirements.The giant ER(GER)effect is ...Traditional dielectric electrorheological fluid(ER)is based on the interaction of dielectric particle polarization,and the yield stress is low,which cannot meet the application requirements.The giant ER(GER)effect is caused by orientations and interactions of polar molecules adsorbed on the particle surfaces.Despite the high yield stress,these polar molecules are prone to wear and fall off,resulting in a continuous reduction in shear stress of GER liquid,which is also not suitable for application.Here we introduce a new type of ER fluid called induced dipole dominant ER fluid(ID-ER),of which the particles contain oxygen vacancies or conductor microclusters both prepared by high energy ball milling(HEBM)technique.In the electric field E,oxygen vacancies or conductor microclusters form induced dipoles.Because the local electric field E_(loc) in the gaps between particles can be two to three orders of magnitude larger than E,the induced dipole moments must be large.The strong interactions of these induced dipoles make the yield stress of the ID-ER fluid reaching more than 100 kPa.Since there are oxygen vacancies or conductor microclusters everywhere in the particles,the particles will not lose the function due to surface wear during use.The experimental results show that the ID-ER fluid possesses the advantages of high shear stress,low current density,short response time,good temperature stability,long service life,and anti-settlement,etc.The comprehensive performance is much better than the existing ER materials,and also the preparation method is simple and easy to repeat,thus it should be a new generation of ER fluid suitable for practical applications.展开更多
The yield stress of our newly developed electrorheological (ER) fluids consisting of dielectric nano-particles suspended in silicone oil reaches hundreds of kPa, which is orders of magnitude higher than that of conv...The yield stress of our newly developed electrorheological (ER) fluids consisting of dielectric nano-particles suspended in silicone oil reaches hundreds of kPa, which is orders of magnitude higher than that of conventional ones. We found that the polar molecules adsorbed on the particles play a decisive role in such new ER fluids. To explain this polar molecule dominated ER (PM-ER) effect a model is proposed based on the interaction of polar molecule-charge between the particles, where the local electric field is significantly enhanced and results in the polar molecules aligning in the direction of the electric field. The model can well explain the giant ER effect and a near-linear dependence of the yield stress on the electric field. The main effective factors for achieving high-performance PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher than one MPa can be expected.展开更多
We have prepared novel coated particles, with a conductor graphite core and a dielectric TiO2 coating, as the dispersed phase of electrorheological fluids. One order of magnitude enhancement in the shear stress is obt...We have prepared novel coated particles, with a conductor graphite core and a dielectric TiO2 coating, as the dispersed phase of electrorheological fluids. One order of magnitude enhancement in the shear stress is obtained by using such composite particles, when it is compared with that of TiO2 particles. The experimental results show a way to get excellent ER system.展开更多
A new class of electrorheological (ER) material using rare earth (RE = Y) oxide as the substrate, NaNO3- doped Y2O3 materials, were synthesized using Na2CO3 and Y(NO3)3 as starting materials. Their ER performanc...A new class of electrorheological (ER) material using rare earth (RE = Y) oxide as the substrate, NaNO3- doped Y2O3 materials, were synthesized using Na2CO3 and Y(NO3)3 as starting materials. Their ER performance, dielectric property, and crystal structure were studied. The results show that doping NaNO3 can markedly enhance the ER activity of the Y2O3 material. For the suspensions of these materials in dimethyl silicone oil, a clear dependence of the shear stress on the doping degree of NANO3 was observed, and the optimal value of Na/Y molar ratio of 0.6 in doping degree was discovered, the relative viscosity ηr( ηE/η0, E = 4.2 kV·mm^-1) of the suspensions is nine times higher than that of pure Y2O3 material. The new results of the relationship between ER effect and the microstructure were obtained, which are helpful for further understanding the mechanism of ER effect and synthesizing a good ER material.展开更多
According to the results of experiments and theoretical analysis, a phenomenon called "capture effect" is put forward, which could be used to describe the particles dynamic behavior of electrorheological (ER) susp...According to the results of experiments and theoretical analysis, a phenomenon called "capture effect" is put forward, which could be used to describe the particles dynamic behavior of electrorheological (ER) suspensions. Then a "structure-force" mathematical model is established to explain this effect based on electrostatic energy density equation. The analysis results show that the dynamic coupling process of ER suspensions under an external electric filed is the function not only of the electric intensity, but also of the dielectric properties and the structure form.展开更多
The new electrorheologicai (ER) material, a particle material composed of Y4O(OH)9(NO3) and NH4NO3, was obtained. They display better ER performance. The shear stress of the suspension of Y4O (OH)9 (NO3) ( ...The new electrorheologicai (ER) material, a particle material composed of Y4O(OH)9(NO3) and NH4NO3, was obtained. They display better ER performance. The shear stress of the suspension of Y4O (OH)9 (NO3) ( NH4NO3 )2.8 material in dimethyl silicone oil reaches 1469 Pa at an electric field strength (E) of 4.2 kV·mm^-1 and the shear rate (7) of 150 s^-1 The relative shear stress, τ E/τ0( τE and τ0 are the shear stresses at E = 4.2 and 0 kV·mm^-1 respectively), is up to 29, which is 19 times that of pure Y2O3 material. The dielectric and conductive property of the materials play important roles in the modification of the ER effect of the particle materials. The researches on these new ER materials are very useful for obtaining a better understanding on the mechanism of the ER effect and finding an ideal ER material.展开更多
By using oxalate group-modified TiO2 nanoparticles as the dispersing phase, different kinds of silicone oil with various viscosities and terminal groups(hydroxyl, hydrogen, and methyl) were used as the dispersing me...By using oxalate group-modified TiO2 nanoparticles as the dispersing phase, different kinds of silicone oil with various viscosities and terminal groups(hydroxyl, hydrogen, and methyl) were used as the dispersing media to prepare different electrorheological(ER) fluids. Their zero-field viscosity, yield stress under direct current electric fields, ER efficiency, shear stability, leakage current density, and sedimentation stability were tested to study the effect of carrier liquid on the properties of ER fluids. The results indicate that the zerofield viscosity, the yield stress, and the leakage current density increase with increasing viscosity of the silicone oils. The effects of the viscosity on the ER efficiency, the shear stability, and the sedimentation ratio depend on the competition between the viscous resistance and the aggregation of the particles. Among the three ER fluids prepared with silicone oil with different terminal groups, hydroxyl-terminated oil based sample has the highest zero-field viscosity, the highest field-induced yield stress and ER efficiency, the largest current density, and the best sedimentation stability.展开更多
Based on a modified Maxwell-Wagner model,molecular dynamics is carried out to simulate the structural changes of ER(electrorheological) suspensions in a poiseuille flow field.The simulation results show that the flow ...Based on a modified Maxwell-Wagner model,molecular dynamics is carried out to simulate the structural changes of ER(electrorheological) suspensions in a poiseuille flow field.The simulation results show that the flow assists in the collection of particles at the electrodes under a low pressure gradient,and the negative ER effect will show under a high pressure gradient.By analyzing the relationship curves of the shear stress and the pressure gradient in different relaxation time,it is found that for the same kind of ER suspensions materials,there is an optimal dielectric relaxation frequency.展开更多
Zinc borate(ZB)particles dispersed in silicone oil(SO)at concentrations of φ=5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength,time,and mechanism.Results revealed that all vi...Zinc borate(ZB)particles dispersed in silicone oil(SO)at concentrations of φ=5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength,time,and mechanism.Results revealed that all virgin dispersions lacked polarization.Triton X-100,a non-ionic surfactant,was added to ZB/SO dispersions to enhance the polarizability of ZB particles.The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions,and the 15vol% ZB/SO system provided the highest dielectric difference Δε′(the difference in ε′values at zero and infinite frequency,Δε′=ε0–ε∝)of 3.64.The electrorheological(ER)activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test,and viscoelastic behaviors were investigated via oscillation tests.A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.展开更多
Graphite/TiO2 composite particles were obtained by sol-gel technique in this paper. The structure and characteristic of the composite particles are analyzed by XRD, SEM and TG-DTA. The electrorheological properties of...Graphite/TiO2 composite particles were obtained by sol-gel technique in this paper. The structure and characteristic of the composite particles are analyzed by XRD, SEM and TG-DTA. The electrorheological properties of the ER fluid containing the particles were measured by a Couette-type rheometer under shear rates of 1-136 s-1 and AC electric fields of 0-3 kV/mm. The experimental results show that the leaking current density of the ER fluid is higher than that of pure titanium dioxide particles dispersed in damping oil. The shear yield stress of the ER fluid increases with increasing electric field and exhibits a typical Bingham flow behavior. The suspension demonstrates an excellent ER performance (τ/τo=1200) compared with conventional ER fluids (τ/τ0 ≤500). The sedimentation of the ER fluid is improved obviously due to the coating effect of the particles.展开更多
The electric conductivity, dynamic modulus and yield stress of the developed electrorheolo-gical fluid (ERF) are measured at different volume fraction and different electric field strengthusing a modified Rheometrics ...The electric conductivity, dynamic modulus and yield stress of the developed electrorheolo-gical fluid (ERF) are measured at different volume fraction and different electric field strengthusing a modified Rheometrics Mechanical Spectrometer (Model 605). The percolation theory isintroduced to explain electrorheological effect and found that the ERF′s have the similarpercolated network structure as that of other ordinary suspensions with a critical volume fractionvalue independent of electric field strength. A master curve of dimensionless modulus againstdimensionless volume fraction is obtained. which shows that the essence of ER phenomenonactually is one kind of the second ofder phase transition.展开更多
A new modified conductivity model was established to predict the shear yield stress of electrorheological fluids (ERF). By using a cell equivalent method, the present model can deal with the face-center square structu...A new modified conductivity model was established to predict the shear yield stress of electrorheological fluids (ERF). By using a cell equivalent method, the present model can deal with the face-center square structure of ERF. Combining the scheme of the classical conductivity model for the single-chain structure, a new formula for the prediction of the shear yield stress of ERF was set up. The influences of the separation distance of the particles, the volume fraction of the particles and the applied electric field on the shear yield stress were investigated.展开更多
Using palygorskite(PAL)as template,the PAL/TiO_(2)/PANI nano-rods were synthesized by heterogeneous precipitation and in-situ polymerization.The synthesized PAL/TiO_(2)/PANI nanorods were used as a novel electrorheolo...Using palygorskite(PAL)as template,the PAL/TiO_(2)/PANI nano-rods were synthesized by heterogeneous precipitation and in-situ polymerization.The synthesized PAL/TiO_(2)/PANI nanorods were used as a novel electrorheological(ER)fluid by mixing with silicone oil,which showed excellent ER effect.The yield stress of the PAL/TiO_(2)/PANI based ER fluid(15 vol%)reached 8.8 kPa under 4 kV mm^(−1) electric field.The dynamic shear stress of the PAL/TiO_(2)/PANI based ER fluid could maintain a stable level in the shear rate range of 0.1–100 s^(−1).Furthermore,the PAL/TiO_(2)/PANI ER fluid exhibited excellent suspension stability.展开更多
The electrorheological (ER) fluids are colloidal suspension of highly polarizable particles in a non-conducting solvent. Chains of submicron-sized particles formed along an applied DC electric field by the so-called e...The electrorheological (ER) fluids are colloidal suspension of highly polarizable particles in a non-conducting solvent. Chains of submicron-sized particles formed along an applied DC electric field by the so-called electrorheological effect. According to the obvious change of transmittance of the ER fluids in a DC electric field when the polarized particles arranged along the field, the model of smart window was proposed by sandwiching the ER fluids based on titania particles coated with silica between a pair of In-Sn oxide (ITO) coated glasses. The solar transmittance change as much as 48.0% was obtained with the wavelength of 500 nm at the maximum on applying and removing the electric field of 500 V/mm.展开更多
Coated-PMMA microspheres consisting of poly (methyl methacrylate)(PMMA) core and barium titanate (BaTiO3) shell were synthesized by the modified sol-gel processing and then adopted as an electrorheological (ER...Coated-PMMA microspheres consisting of poly (methyl methacrylate)(PMMA) core and barium titanate (BaTiO3) shell were synthesized by the modified sol-gel processing and then adopted as an electrorheological (ER) materials. The structure and morphology of coated powders were chyfecterized by SEM and FT-IR; the shear stress of the suspensions of coated-PMMA particles and pure PMMA particles in silicone oil with a 20 vol% were investigated. The results show that the BaTiO3 coated PMMA microspheres based suspension in silicone oil exhibited typical ER behavior and stronger ER effects.展开更多
The smart properties of homogeneous electrorheological fluid (HERF) containing side-chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced.A mechanical m...The smart properties of homogeneous electrorheological fluid (HERF) containing side-chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced.A mechanical model of the HERF smart damper was established on the basis of experiment and theoretical analysis.Then a controlled equation of SDOF structure by HERF damper was derived and a semi active control strategy based on optimal sliding displacement of damper was presented.The simulation results for a single story frame structure indicate that HERF,which may avoid some defects of common particles suspended ER fluids,is an excellent smart material with better stability.Using the semi active control strategy presented,HERF smart damper controlled could effectively reduce seismic responses of structures and keeps the control stable at all times.展开更多
In this study, electrorheological (ER) behavior of suspensions prepared from 3.0 and 9.0 μm diatomite particulate, dispersed in insulating silicone oil (SO) medium was investigated. Sedimentation stabilities of s...In this study, electrorheological (ER) behavior of suspensions prepared from 3.0 and 9.0 μm diatomite particulate, dispersed in insulating silicone oil (SO) medium was investigated. Sedimentation stabilities of suspensions (c = 5 wt%) prepared using these diatomite powders were determined to be 32 days (d = 3 μm) and 24 days (d = 9 μm), respectively. ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. Shear stress of diatomite suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and particle size, showing a typical shear thinning non-Newtonian visco-elastic behavior. Effects of high temperature and polar promoter onto ER activity ofdiatomite/SO system were also investigated.展开更多
In this study, the electrorheological (ER) behavior of suspensions prepared from d50 = 2.4 lam talc powder, dispersed in insulating silicone oil (SO) medium was investigated. Sedimentation stabilities of suspensio...In this study, the electrorheological (ER) behavior of suspensions prepared from d50 = 2.4 lam talc powder, dispersed in insulating silicone oil (SO) medium was investigated. Sedimentation stabilities of suspensions (c = 5 wt%) prepared using these talc powder powders were determined to be 78 days. The ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. The shear stress of talc powder suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and showed a typical shear thinning non-Newtonian visco-elastic behavior. Effects of frequency on the ER activity of talc powder/SO system were also investigated.展开更多
基金financial support from the National Natural Science Foundation of China(No.52174066,No.51534007).
文摘Exposing waxy oils to an electric field may significantly improve their cold flowability.Our previous study has shown that interfacial polarization,i.e.,charged particle accumulation on the wax particle surface,is the primary mechanism of the electrorheological behavior of waxy oils.However,the way that charged particles interact with wax particles under an electric field remains unknown.In this study,we found no viscosity and impedance change for two waxy crude oils after their exposure to a high-voltage electric field.However,the yield stresses were reduced obviously.We thus proposed that the collision of colloidal particles such as resins and asphaltenes with the wax particles could be an essential mechanism that the wax particle structure was weakened.To verify this hypothesis,a series of ad hoc experiments were carried out,i.e.,by performing electrorheological tests on model waxy oils containing additives removable under an electric field,including electrically-neutral colloidal particles(Fe3O4),charged colloidal particles(resins),and oil-soluble electrolyte(C22H14CoO4),respectively,and demonstrated that upon application of a high-voltage electric field,charged particles in a waxy oil may move and thus collide with wax particles,and consequently adhere to the wax particle surface.The particle collision results in damage to the wax particle network,and the electrostatic repulsion arising from the adhesion of the charged particle on the wax particle diminishes attraction between wax particles.This study clarifies the process of interfacial polarization.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0403000)the National Natural Science Foundation of China(Grant No.11874430).
文摘Traditional dielectric electrorheological fluid(ER)is based on the interaction of dielectric particle polarization,and the yield stress is low,which cannot meet the application requirements.The giant ER(GER)effect is caused by orientations and interactions of polar molecules adsorbed on the particle surfaces.Despite the high yield stress,these polar molecules are prone to wear and fall off,resulting in a continuous reduction in shear stress of GER liquid,which is also not suitable for application.Here we introduce a new type of ER fluid called induced dipole dominant ER fluid(ID-ER),of which the particles contain oxygen vacancies or conductor microclusters both prepared by high energy ball milling(HEBM)technique.In the electric field E,oxygen vacancies or conductor microclusters form induced dipoles.Because the local electric field E_(loc) in the gaps between particles can be two to three orders of magnitude larger than E,the induced dipole moments must be large.The strong interactions of these induced dipoles make the yield stress of the ID-ER fluid reaching more than 100 kPa.Since there are oxygen vacancies or conductor microclusters everywhere in the particles,the particles will not lose the function due to surface wear during use.The experimental results show that the ID-ER fluid possesses the advantages of high shear stress,low current density,short response time,good temperature stability,long service life,and anti-settlement,etc.The comprehensive performance is much better than the existing ER materials,and also the preparation method is simple and easy to repeat,thus it should be a new generation of ER fluid suitable for practical applications.
文摘The yield stress of our newly developed electrorheological (ER) fluids consisting of dielectric nano-particles suspended in silicone oil reaches hundreds of kPa, which is orders of magnitude higher than that of conventional ones. We found that the polar molecules adsorbed on the particles play a decisive role in such new ER fluids. To explain this polar molecule dominated ER (PM-ER) effect a model is proposed based on the interaction of polar molecule-charge between the particles, where the local electric field is significantly enhanced and results in the polar molecules aligning in the direction of the electric field. The model can well explain the giant ER effect and a near-linear dependence of the yield stress on the electric field. The main effective factors for achieving high-performance PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher than one MPa can be expected.
基金the National Natural Science Foundation of China! (No.19834020).
文摘We have prepared novel coated particles, with a conductor graphite core and a dielectric TiO2 coating, as the dispersed phase of electrorheological fluids. One order of magnitude enhancement in the shear stress is obtained by using such composite particles, when it is compared with that of TiO2 particles. The experimental results show a way to get excellent ER system.
文摘A new class of electrorheological (ER) material using rare earth (RE = Y) oxide as the substrate, NaNO3- doped Y2O3 materials, were synthesized using Na2CO3 and Y(NO3)3 as starting materials. Their ER performance, dielectric property, and crystal structure were studied. The results show that doping NaNO3 can markedly enhance the ER activity of the Y2O3 material. For the suspensions of these materials in dimethyl silicone oil, a clear dependence of the shear stress on the doping degree of NANO3 was observed, and the optimal value of Na/Y molar ratio of 0.6 in doping degree was discovered, the relative viscosity ηr( ηE/η0, E = 4.2 kV·mm^-1) of the suspensions is nine times higher than that of pure Y2O3 material. The new results of the relationship between ER effect and the microstructure were obtained, which are helpful for further understanding the mechanism of ER effect and synthesizing a good ER material.
文摘According to the results of experiments and theoretical analysis, a phenomenon called "capture effect" is put forward, which could be used to describe the particles dynamic behavior of electrorheological (ER) suspensions. Then a "structure-force" mathematical model is established to explain this effect based on electrostatic energy density equation. The analysis results show that the dynamic coupling process of ER suspensions under an external electric filed is the function not only of the electric intensity, but also of the dielectric properties and the structure form.
文摘The new electrorheologicai (ER) material, a particle material composed of Y4O(OH)9(NO3) and NH4NO3, was obtained. They display better ER performance. The shear stress of the suspension of Y4O (OH)9 (NO3) ( NH4NO3 )2.8 material in dimethyl silicone oil reaches 1469 Pa at an electric field strength (E) of 4.2 kV·mm^-1 and the shear rate (7) of 150 s^-1 The relative shear stress, τ E/τ0( τE and τ0 are the shear stresses at E = 4.2 and 0 kV·mm^-1 respectively), is up to 29, which is 19 times that of pure Y2O3 material. The dielectric and conductive property of the materials play important roles in the modification of the ER effect of the particle materials. The researches on these new ER materials are very useful for obtaining a better understanding on the mechanism of the ER effect and finding an ideal ER material.
基金Funded by the National Natural Science Foundation of China(51478088)
文摘By using oxalate group-modified TiO2 nanoparticles as the dispersing phase, different kinds of silicone oil with various viscosities and terminal groups(hydroxyl, hydrogen, and methyl) were used as the dispersing media to prepare different electrorheological(ER) fluids. Their zero-field viscosity, yield stress under direct current electric fields, ER efficiency, shear stability, leakage current density, and sedimentation stability were tested to study the effect of carrier liquid on the properties of ER fluids. The results indicate that the zerofield viscosity, the yield stress, and the leakage current density increase with increasing viscosity of the silicone oils. The effects of the viscosity on the ER efficiency, the shear stability, and the sedimentation ratio depend on the competition between the viscous resistance and the aggregation of the particles. Among the three ER fluids prepared with silicone oil with different terminal groups, hydroxyl-terminated oil based sample has the highest zero-field viscosity, the highest field-induced yield stress and ER efficiency, the largest current density, and the best sedimentation stability.
基金Project (50771089) supported by the National Natural Science Foundation of China
文摘Based on a modified Maxwell-Wagner model,molecular dynamics is carried out to simulate the structural changes of ER(electrorheological) suspensions in a poiseuille flow field.The simulation results show that the flow assists in the collection of particles at the electrodes under a low pressure gradient,and the negative ER effect will show under a high pressure gradient.By analyzing the relationship curves of the shear stress and the pressure gradient in different relaxation time,it is found that for the same kind of ER suspensions materials,there is an optimal dielectric relaxation frequency.
基金Turkish Scientific and Technological Research Council for the financial support of this work (Project No: 112T811)
文摘Zinc borate(ZB)particles dispersed in silicone oil(SO)at concentrations of φ=5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength,time,and mechanism.Results revealed that all virgin dispersions lacked polarization.Triton X-100,a non-ionic surfactant,was added to ZB/SO dispersions to enhance the polarizability of ZB particles.The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions,and the 15vol% ZB/SO system provided the highest dielectric difference Δε′(the difference in ε′values at zero and infinite frequency,Δε′=ε0–ε∝)of 3.64.The electrorheological(ER)activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test,and viscoelastic behaviors were investigated via oscillation tests.A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.
基金The authors are thankful to the support of the National Natural Science Foundation of China(Grant No.50135030).
文摘Graphite/TiO2 composite particles were obtained by sol-gel technique in this paper. The structure and characteristic of the composite particles are analyzed by XRD, SEM and TG-DTA. The electrorheological properties of the ER fluid containing the particles were measured by a Couette-type rheometer under shear rates of 1-136 s-1 and AC electric fields of 0-3 kV/mm. The experimental results show that the leaking current density of the ER fluid is higher than that of pure titanium dioxide particles dispersed in damping oil. The shear yield stress of the ER fluid increases with increasing electric field and exhibits a typical Bingham flow behavior. The suspension demonstrates an excellent ER performance (τ/τo=1200) compared with conventional ER fluids (τ/τ0 ≤500). The sedimentation of the ER fluid is improved obviously due to the coating effect of the particles.
文摘The electric conductivity, dynamic modulus and yield stress of the developed electrorheolo-gical fluid (ERF) are measured at different volume fraction and different electric field strengthusing a modified Rheometrics Mechanical Spectrometer (Model 605). The percolation theory isintroduced to explain electrorheological effect and found that the ERF′s have the similarpercolated network structure as that of other ordinary suspensions with a critical volume fractionvalue independent of electric field strength. A master curve of dimensionless modulus againstdimensionless volume fraction is obtained. which shows that the essence of ER phenomenonactually is one kind of the second ofder phase transition.
文摘A new modified conductivity model was established to predict the shear yield stress of electrorheological fluids (ERF). By using a cell equivalent method, the present model can deal with the face-center square structure of ERF. Combining the scheme of the classical conductivity model for the single-chain structure, a new formula for the prediction of the shear yield stress of ERF was set up. The influences of the separation distance of the particles, the volume fraction of the particles and the applied electric field on the shear yield stress were investigated.
基金support by the Jiangsu Key R&D program(BE2019072)the Ningbo Natural Science Foundation(2018A610167,2018A610322).
文摘Using palygorskite(PAL)as template,the PAL/TiO_(2)/PANI nano-rods were synthesized by heterogeneous precipitation and in-situ polymerization.The synthesized PAL/TiO_(2)/PANI nanorods were used as a novel electrorheological(ER)fluid by mixing with silicone oil,which showed excellent ER effect.The yield stress of the PAL/TiO_(2)/PANI based ER fluid(15 vol%)reached 8.8 kPa under 4 kV mm^(−1) electric field.The dynamic shear stress of the PAL/TiO_(2)/PANI based ER fluid could maintain a stable level in the shear rate range of 0.1–100 s^(−1).Furthermore,the PAL/TiO_(2)/PANI ER fluid exhibited excellent suspension stability.
基金The authors greatly appreciated financial support from the National Natural Science Foundation of China mostly under projecl No.59672011 the Foundation for the Youth Faculty at UEST of China partially.
文摘The electrorheological (ER) fluids are colloidal suspension of highly polarizable particles in a non-conducting solvent. Chains of submicron-sized particles formed along an applied DC electric field by the so-called electrorheological effect. According to the obvious change of transmittance of the ER fluids in a DC electric field when the polarized particles arranged along the field, the model of smart window was proposed by sandwiching the ER fluids based on titania particles coated with silica between a pair of In-Sn oxide (ITO) coated glasses. The solar transmittance change as much as 48.0% was obtained with the wavelength of 500 nm at the maximum on applying and removing the electric field of 500 V/mm.
基金Funded by the National Natural Science Foundation of China (Nos. 10418014 and 10474074).
文摘Coated-PMMA microspheres consisting of poly (methyl methacrylate)(PMMA) core and barium titanate (BaTiO3) shell were synthesized by the modified sol-gel processing and then adopted as an electrorheological (ER) materials. The structure and morphology of coated powders were chyfecterized by SEM and FT-IR; the shear stress of the suspensions of coated-PMMA particles and pure PMMA particles in silicone oil with a 20 vol% were investigated. The results show that the BaTiO3 coated PMMA microspheres based suspension in silicone oil exhibited typical ER behavior and stronger ER effects.
文摘The smart properties of homogeneous electrorheological fluid (HERF) containing side-chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced.A mechanical model of the HERF smart damper was established on the basis of experiment and theoretical analysis.Then a controlled equation of SDOF structure by HERF damper was derived and a semi active control strategy based on optimal sliding displacement of damper was presented.The simulation results for a single story frame structure indicate that HERF,which may avoid some defects of common particles suspended ER fluids,is an excellent smart material with better stability.Using the semi active control strategy presented,HERF smart damper controlled could effectively reduce seismic responses of structures and keeps the control stable at all times.
文摘In this study, electrorheological (ER) behavior of suspensions prepared from 3.0 and 9.0 μm diatomite particulate, dispersed in insulating silicone oil (SO) medium was investigated. Sedimentation stabilities of suspensions (c = 5 wt%) prepared using these diatomite powders were determined to be 32 days (d = 3 μm) and 24 days (d = 9 μm), respectively. ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. Shear stress of diatomite suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and particle size, showing a typical shear thinning non-Newtonian visco-elastic behavior. Effects of high temperature and polar promoter onto ER activity ofdiatomite/SO system were also investigated.
基金This work was supported by the Omya Mining Co of Istanbul and Harran University.
文摘In this study, the electrorheological (ER) behavior of suspensions prepared from d50 = 2.4 lam talc powder, dispersed in insulating silicone oil (SO) medium was investigated. Sedimentation stabilities of suspensions (c = 5 wt%) prepared using these talc powder powders were determined to be 78 days. The ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. The shear stress of talc powder suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and showed a typical shear thinning non-Newtonian visco-elastic behavior. Effects of frequency on the ER activity of talc powder/SO system were also investigated.