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We have developed a Zimm-type viscometer specially designed for the simultaneous measurements of the structure factor and the viscosity of hyperswollen lyotropic liquid crystals under a very weak shear. We have investigated the shear effects on the layer undulation fluctuation in the lamellar structure and the transition from the anisotropic lamellar to the isotropic sponge phase. We have found a significant difference in the rheological properties between the lamellar and the sponge phase: The former exhibits non-Newtonian flow behavior, while the latter exhibits Newtonian behavior.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
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利用流变仪对聚偏氟乙烯(PVDF)/己内酰胺(CPL)热致相分离法(TIPS)成膜体系铸膜液的流变性能进行研究.考察了剪切频率、温度、PVDF质量分数对PVDF/CPL铸膜液体系的黏度、非牛顿性指数、黏流活化能、溶液黏弹性的影响,利用TIPS法制备PVDF膜,进一步探讨了铸膜液体系的流变性能对刮膜速率、制膜温度等成膜条件的指导作用.实验结果表明:PVDF/CPL铸膜液体系为非牛顿性流体,随着PVDF质量分数的升高,PVDF/CPL铸膜液体系的黏度增加,非牛顿性指数增加,黏流活化能升高,对应膜的结构越致密,水通量降低,截留率升高,膜的拉伸强度增强.PVDF质量分数低的铸膜液体系,制膜时对温度的灵敏度低,刮膜速率对膜的制备影响大,制膜过程需要对刮膜速率精确地控制;PVDF质量分数高的铸膜液体系,对温度的灵敏度高,可以在较宽的刮膜速度范围下制膜. 相似文献
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External influences or internal disturbances may result in phase separation instabilities which could lead to operational failure of He II space cooling systems. Possible instabilities are defined and, using the active phase separator, suitable measures for prevention and control are discussed. Experimental results with a superleak arranged in parallel to the active phase separator indicate an additional possibility for adaptation of the latter to specific demands. 相似文献
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以邻苯二甲酸二丁酯(DBP)和大豆油混合物为稀释剂,利用热致相分离(ThermallyInduced Phase Separation,TIPS)法制备了等规聚丙烯(iPP)微孔膜.结果表明,稀释剂体系中DBP和大豆油的质量比对浊点温度影响较大,而对结晶温度影响较小;随着稀释剂体系中DBP含量的增加,在固定聚合物浓度及相同的冷却条件下,多孔膜由空间网状结构逐渐转变为腔胞状结构,表面孔径也有明显的增大趋势;稀释剂的加入降低了iPP球晶的生长速率,其组成对iPP球晶生长速率也有一定影响. 相似文献
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This work discusses the classical problem of effective viscosity of a Newtonian fluid with rigid spherical particles. It argues that the simple non-interaction approximation when formulated correctly yields an effective viscosity ratio for the suspension in the form μ/μ0 = (1 − 2.5?)−1 that remains accurate at much higher volume fractions of particles ? than the usual first-order approximation μ/μ0 = 1 + 2.5?. 相似文献
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Readul Mohammad Islam Christopher Abadie Nazimuddin M. Wasiuddin 《International Journal of Pavement Engineering》2017,18(12):1122-1129
Viscosity determination of thixotropic emulsions with good repeatability has always been a major challenge. Currently, Saybolt Furol viscometer (SFV) is used to determine the viscosity of the emulsion, but the main drawback of the SFV is that it cannot simulate the behaviour of emulsion under different shear rate. Rotational viscometer (RV) can measure viscosity at different shear rates. Due to the thixotropic behaviour of the emulsions, getting repeatable results by following the hot binder specification is a problematic task. In this study, a new multiple shear step approach is used to determine the viscosity of the emulsified asphalt using RV. Three low viscous (SS-1, SS-1H and SS-1L) and two high viscous (CRS-2 and CRS-2P) emulsions were used in this study. Shear stress is gradually stepped up to different levels after certain time interval to determine the viscosity. In this manner, emulsion undergoes a known shear state and each reading is preceded by a certain repeatable shear history. It was observed that with the progression of time and simultaneous increase in shear rate, the viscosity results are much more stable and repeatable with less than 5% coefficient of variance. The final specifications proposed are 220–730 and 5–90 cP at 50 rpm and 30 °C for high and low viscous emulsions, respectively, which are based on 98% probability. Viscosity measured by this approach also showed strong correlation with water content (R2 > 0.94). The correlation between viscosity and water content is even stronger after dilution. With different dilution water content, viscosity of CRS-2 and CRS-2P exhibited R2 values of 0.97 and 0.98, respectively. 相似文献
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G. C. Straty 《Journal of research of the National Institute of Standards and Technology》1989,94(4):259-261
We report on the construction of an apparatus to allow neutron scattering measurements on fluids undergoing shear. The apparatus has been used with the cold neutron small-angle-neutron-scattering (SANS) spectrometer at the NIST research reactor and will be made available to users as a permanent part of the NIST facility. 相似文献
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《Materials Science & Technology》2013,29(6):576-580
The microstructures of high entropy alloys of the system CoCrCuFexNi and CoCrCuFeNix (where x indicates the molar ratio, which, where not specified, is 1) have been investigated. Many Cu rich spheres were evident in the microstructure of CoCrCuFe0.5Ni and CoCrCuFeNi0.5 alloys, which indicates that liquid phase separation had occurred before solidification. During liquid phase separation, the original liquids separated into two liquids: Cu rich and Cu depleted. In contrast, in other alloys (x?=?1.0, 1.5 and 2.0), typical dendritic and interdendritic structures are obtained. Cu and/or Cr rich precipitates, with various morphologies, can be seen in the interdendritic region. Additionally, Cu rich nanoparticles and Cr rich bird shaped structures can be observed in the Cu rich spheres. Sluggish cooperative diffusion causes the element segregation and formation of nanoprecipitates in the microstructures. The calculated positive mixing enthalpies of CoCrCuFe0.5Ni and CoCrCuFeNi0.5 alloys are likely reasons for their liquid phase separation. 相似文献
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Storage stability and phase separation behaviour of four styrene-butadiene-styrene (SBS) polymer-modified bitumen (PMB) binders are investigated by conventional binder tests and fluorescence microscopy in this paper. Since no separation happened in the stable PMBs, research focus was placed on capturing and analysing the phase separation process in the unstable PMBs. A phase inversion phenomenon was observed in one unstable PMB during the phase separation, showing the possible viscoelastic effects. Furthermore, it is indicated that criteria only based on compositional parameters can give misleading predictions of PMB storage stability. New criteria still need to be defined. The potential approaches to PMB phase behaviour prediction are reviewed and exploratively discussed in the context of the four investigated PMBs. This leads to a further discussion on the possibility of having a thermodynamic approach to PMB phase behaviour prediction by looking into the free energy of PMB. The Flory–Huggins theory provides a way to do this, upon the consideration of PMB as a pseudo-binary blend and some made assumptions. Free energy curves have the strength of giving more information like the equilibrium phase composition. In addition, some more aspects should be also considered for PMB phase behaviour prediction towards an applicable criterion. 相似文献
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J. Penfold E. Staples A. Khan Lhodi I. Tucker 《International Journal of Thermophysics》1995,16(5):1109-1117
The development of Couette shear-flow cells for use with small-angle neutron scattering (SANS) has provided the opportunity for the morphology of solutions of anisotropically shaped surfactant micelles to be probed in more detail and for the effects of shear on such structures to be explored. The effects of finite concentration (hindered rotation and interactions), flexibility, and shear-induced changes/structures are described for elongated micelles in their dilute phase (for a range of ionic, nonionic, and mixed ionic-nonionic micelles). Some recent measurements on nonionic and mixed ionic-nonionic micelles demonstrate that SANS can provide a vital insight into the rheological properties and morphology of micellar solutions over a wider region of their complex phase diagrams.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, USA. 相似文献
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Ojala A Bürckstümmer H Stolte M Sens R Reichelt H Erk P Hwang J Hertel D Meerholz K Würthner F 《Advanced materials (Deerfield Beach, Fla.)》2011,23(45):5398-5403
Thermal co-evaporation of C(60) fullerene and two merocyanine dyes affords bulk heterojunction solar cells with improved short-circuit currents and power conversion efficiencies in comparison with the respective single donor cells. These results are rationalized by the formation of three distinct subphases driven by differences in molecular shape and electrostatic interactions. 相似文献
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Nonequilibrium molecular dynamics calculations of the shear viscosity of supercritical carbon dioxide along the 313 K isotherm are reported. Three different intermolecular potential models of increasing complexity are considered: a spherically symmetric Lennard-Jones potential, a two-site Lennard-Jones potential, and a three-site potential which includes a quadrupole-quadrupole moment. Results for the three potentials are compared with experimental data.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
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