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Volume fraction

About: Volume fraction is a research topic. Over the lifetime, 16312 publications have been published within this topic receiving 374181 citations.


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Journal ArticleDOI
TL;DR: The experimentally measurable alpha relaxation time is found to be very similar to the theoretically defined mean reaction time for escape from the barrier-dominated regime, and time-volume fraction superposition holds quite well, despite the presence of stretching and volume fraction dependent decoupling associated with the stochastic barrier hopping process.
Abstract: Single particle Brownian dynamics simulation methods are employed to establish the full trajectory level predictions of our nonlinear stochastic Langevin equation theory of activated hopping dynamics in glassy hard sphere suspensions and fluids. The consequences of thermal noise driven mobility fluctuations associated with the barrier hopping process are determined for various ensemble-averaged properties and their distributions. The predicted mean square displacements show classic signatures of transient trapping and anomalous diffusion on intermediate time and length scales. A crossover to a stronger volume fraction dependence of the apparent nondiffusive exponent occurs when the entropic barrier is of order the thermal energy. The volume fraction dependences of various mean relaxation times and rates can be fitted by empirical critical power laws with parameters consistent with ideal mode-coupling theory. However, the results of our divergence-free theory are largely a consequence of activated dynamics. The experimentally measurable alpha relaxation time is found to be very similar to the theoretically defined mean reaction time for escape from the barrier-dominated regime. Various measures of decoupling have been studied. For fluid states with small or nonexistent barriers, relaxation times obey a simple log-normal distribution, while for high volume fractions the relaxation time distributions become Poissonian. The product of the self-diffusion constant and mean alpha relaxation time increases roughly as a logarithmic function of the alpha relaxation time. The cage scale incoherent dynamic structure factor exhibits nonexponential decay with a modest degree of stretching. A nearly universal collapse of the different volume fraction results occurs if time is scaled by the mean alpha relaxation time. Hence, time-volume fraction superposition holds quite well, despite the presence of stretching and volume fraction dependent decoupling associated with the stochastic barrier hopping process. The relevance of other origins of dynamic heterogeneity (e.g., mesoscopic domains), and comparison of our results with experiments, simulations, and alternative theories, is discussed.

91 citations

Journal ArticleDOI
19 Apr 2007-Langmuir
TL;DR: An interfacial layer, competing with Brownian motion as a corresponding mechanism, is conceptually connected with the surface-charge-induced electrical double layer by applying colloidal science, and the first explicit equations for the thickness and thermal conductivity of the layer are obtained.
Abstract: Although recent experiments have revealed that nanofluids have superior thermal conductivities to base fluids, the inherent physics are not fully understood. In this study, an interfacial layer, competing with Brownian motion as a corresponding mechanism, is conceptually connected with the surface-charge-induced electrical double layer. By applying colloidal science, the first explicit equations for the thickness and thermal conductivity of the layer are obtained. A fractal model including the new concept of the layer is developed. The model predictions are compared with experimental data for effects of pH, temperature, volume fraction, and primary particle size of CuO-water nanofluids.

91 citations

Book ChapterDOI
01 Jan 2008
TL;DR: The Cahn-Hilliard equation has been used to model many other phenomena, such as the evolution of intergalactic material, the dynamics of two populations, the biomathematical modeling of a bacterial film, and certain thin film problems.
Abstract: Publisher Summary This chapter focuses on the Cahn–Hilliard equation. In the context of the Cahn–Hilliard equation, the two components could refer, for example, to a system with two metallic components, or two polymer components, or say, two glassy components. Frequently in materials science literature, concentration is given in terms of mole fraction or equivalently number fraction, rather than in terms of volume fraction or mass fraction. A mole refers to 6.02252×1023 molecules (Avogadro's number of molecules), and the mole fraction of component A refers to the number of A molecules per mole of the two component system, locally evaluated. Mole fraction of number fraction is equivalent to volume fraction if the molar volume (the volume occupied by one mole) is independent of composition, which is rarely strictly correct. The Cahn–Hilliard equation also appears in modeling many other phenomena. These include the evolution of two components of intergalactic material, the dynamics of two populations, the biomathematical modeling of a bacterial film, and certain thin film problems.

91 citations

Journal ArticleDOI
TL;DR: In this article, volume strain measurements were carried out on PP composites containing different CaCO3 fillers and a volume increase was detected which could be divided into two linear sections as a function of elongation.
Abstract: Volume strain measurements were carried out on PP composites containing different CaCO3 fillers. During deformation, a volume increase was detected which could be divided into two linear sections as a function of elongation. Comparison of data with existing theories has shown that in the first part, mostly elastic deformation takes place and the slope can be related to the Poisson's ratio of the composite. Scanning electron microscopy revealed that in the second stage, the dominating micromechanical deformation process is debonding. Void formation is initiated at a certain stress which approximately corresponds to the yield stress of the composites, but data in the literature and model calculations indicate that separation of the matrix/filler interface may start at lower stresses. Initiation stress depends on the particle size of the filler and on interfacial interactions. The rate of volume increase has non-linear dependence on the volume fraction of the filler. Volume strain measurements reflect micromechanical deformations well, but further study is needed to explain contradictions between experimental results and theoretical predictions.

91 citations

Journal ArticleDOI
TL;DR: In this paper, a new model for density of nanofluids, which includes nanolayer, was developed, based on the experimental data, which was also found that the amount of the void in the nanolayers is more sensitive to nanoparticle size and not to base fluids or nanoparticles material.

91 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023965
20222,020
2021744
2020736
2019786
2018696