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Tunable left-handed metamaterial based on electrorheological fluids

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Progress in Natural Science:Materials International 2008年第7期18卷 907-911页

作者： Yong Huang, Xiaopeng Zhao *, Liansheng Wang, Chunrong Luo Institute of electrorheological Technology, Department of Applied Physics, Northwestern Polytechnical University, Xi’an 710072, China Institute of electrorheological Technology Department of Applied Physics Northwestern Polytechnical University Xi’an 710072 China

A tunable left-handed metamaterial consisting of a periodic array of the left-handed dendritic structure units infiltrated with electro- rheological fluids is demonstrated. Experimental results show that the passband can move from the original 8.50–10.60 GHz to 7.16– 8.39 GHz after electrorheological fluids are infused. When a dc (direct current) electric field of 666 V/mm is applied, the passband moves toward lower frequency of within 7.08–8.30 GHz. This method provides one convenient way to design adaptive metamaterials.

关键词： Left-handed metamaterials Dendritic model electrorheological fluids Omnidirection

Conductivity effect in electrorheological fluids

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Science China(Physics,Mechanics & Astronomy) 2004年第Z1期47卷 59-64页

作者： TIAN Yu WEN Shizhu MENG Yonggang State Key Laboratory of Tribology Tsinghua University Beijing 100084 China State Key Laboratory of Tribology Tsinghua University Beijing 100084 China State Key Laboratory of Tribology Tsinghua University Beijing 100084 China

Based on conduction model and cubic particle model, the relationship between current density and shear yield stress of electrorheological (ER) fluids was calculated and compared with some reported experimental results. The conductivity of the insulating oils is found to have been changed by the mixed particles. Several ways to decrease insulating liquid conductivity and increase the conductivity ratio of ER fluids have been proposed to prepare ER fluids with high shear yield stresses but low current densities.

关键词： electrorheological fluids current density shear yield stress structure effect non-ohmic conductivity

A New Modified Conductivity Model for Prediction of Shear Yield Stress of electrorheological fluids Based on Face-center Square Structure

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Journal of Wuhan University of Technology(Materials Science) 2004年第4期19卷 91-94页

作者：谭柱华 Wuhan University of Technology

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.

关键词： electrorheological fluids face-center square structure equivalent cell conductivity model shear yield stress

Adjustable character of microwave attenuation in BaTiO3 electrorheological fluids

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Progress in Natural Science:Materials International 2002年第10期 35-40页

作者： FAN Jijun, ZHAO Xiaopeng , HUANG Min, GUAN Litao and WEN Lishi(1. Institute of electrorheological Technology, 141# Northwestern Polytechnical University, Xi'an710072, China 2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)

The behavior of microwave attenuation in BaTiO3 electrorheological fluids is studied when considering microwave propagation in the directions perpendicular and parallel to the particle chains, respectively. In the former case, the microwave attenuation increases with field strength when the particle concentration is low, and the increase of the particle concentration can also increase the microwave attenuation. However, when the particle concentration exceeds a critical value, the attenuation will first increase then decrease with field strength. At the same time, the higher the field strength, the greater the change of microwave attenuation. Moreover, there is a saturation field strength. When the field strength is lower than the saturated one, the change of microwave attenuation is fast. On the other hand, in the case of microwave propagation parallel to the particle chains, the microwave attenuation increases with the field strength monotonously. In addition, the variation of microwave attenuation wi

关键词： electrorheological fluids BaTiO3 microwave attenuation relaxation effect.

Instability of Taylor-Couette Flow of electrorheological Fluid

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Chinese Physics Letters 2004年第7期21卷 1388-1390页

作者： PENGJie ZHUKe-Qin DepartmentofEngineeringMechanics TsinghuaUniversityBeijing100084

A linearized instability analysis of Taylor–Couette flow between two rotating concentric cylinders of an electrorheological (ER) fluid is carried out. The ER fluid exhibits a yield stress in addition to the plastic viscosity when an extra electric-field is applied. It can be found that the yield stress plays a dual role in the flow instability. The possibility of the yield surface falling between the cylinders is analysed. Although small waves appeared on the yielded surface is considered, the yielded surface, which has been treated as a free surface, has little effect on the flow instability. The effects of axisymmetric perturbation on the flow instability are presented due to the axisymmetric of the basic flow. The parameter β in the yield stress formula of the ER fluid is shown to have distinct effects on the flow instability characteristics.

关键词： electrorheological fluids

Characteristics of electrorheological Fluid Flow in Journal Bearings

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Chinese Physics Letters 2002年第2期19卷 273-275页

作者：张准朱克勤 DepartmentofEngineeringMechanics TsinghuaUniversityBeijing100084

Under the influence of an applied electric field, the variation of apparent viscosity of electrorheological (ER) fluid flow causes ER effects. According to the Bingham model, which is widely used for describing the rheological properties of ER fluids, this variation should be very weak at high shear rates. To clarify the ER effects in ER journal bearings at high shear rate, a numerical study is presented. It is found that under the influence of the applied electric field, ER effects in ER journal bearings can be affected by not only the apparent viscosity of ER fluids but also the movement of yield surface in the clearance of ER journal bearing. In the case of low shear rate, both are effective on the lubricant film pressure of ER journal bearings. In the case of high shear rates, the main factor is the extension of non-yield region in the bearing clearance.

关键词： electrorheological fluids

electrorheological PROPERTIES OF TALC POWDER/SILICONE OIL SUSPENSIONS UNDER DC FIELDS

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Chinese Journal of Polymer Science 2007年第3期25卷 245-252页

作者： Hasim Yilmaz Ummihan Yilmaz Chemistry Department Sciences FacultyHarran University63190 OsmanbeySanliurfaTurkey Chemistry Department Sciences FacultyGazi University06500 TeknikokullarAnkaraTurkey

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.

关键词： electrorheological fluids Talc powder/silicone oil suspensions Shear stress

electrorheological PROPERTIES OF DIATOMITE/SILICONE OIL SUSPENSIONS UNDER DC FIELDS

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Chinese Journal of Polymer Science 2006年第5期24卷 463-471页

作者： Hasim Yilmaz Chemistry Department Sciences FacultyHarran University63190 OsmanbeySanliurfaTurkey

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.

关键词： electrorheological fluids Diatomite/silicone oil suspensions Shear stress.

Supramolecular complex formation of β-cyclodextrin polymer with substituted salicylic acid or 3-hydroxy-2-naphthoic acid and their electrorheological behaviors

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Science China Chemistry 2004年第4期47卷 340-348页

作者： GAO Ziwei ZHAO Xiaopeng SUN Ping SI Gang Institute of electrorheological Technology141# Department of Applied PhysicsNorthwestern Polytechnical UniversityXian 710072China Department of Chemistry School of Chemistry and Material ScienceShaanxi Normal UniversityXi’an 710062China

According to the chemical design, electrorheological properties of supramolecular complex from β-cyclodextrin polymer (β -CDP) were discussed. Six supramolecular complexes of β-cyclodextrin polymer with substituted salicylic acid and 3-hydroxy-2-naphthoic acid were synthesized by the solid-phase self-assembly method, and their component and structure were characterized by NMR, FT-IR, UV-vis and the fluorescence analysis. Then the electrorheological properties of their suspensions in silicone oil were investigated under DC electric fields. It was found that the yield stresses of these supramolecular complex ER fluids were 7.3–9.8 kPa at 4 kV/mm in DC electric field, which were enhanced by 34%–72% compared with that of pure β-CDP. Among them, that of β-CDP/3-hydroxy-2-naphthoic acid ER fluid was the highest. It was also found that the ER effect of supramolecular complexes can be controlled by changing different guests. When the substituted group is at phenyl ring, ER behavior can be slightly adjusted by the different substituted groups, their number as well as their position at phenyl ring. This can be proved by the measurement of dielectric properties.

关键词： electrorheological fluids β-cyclodextrin crosslinking polymer substituted salicylic acid 3-hydroxy-2-naphthoic acid supramolecular complex