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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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TL;DR: In this article, the effect of stress on the diffusion of water in glassy polymers is analytically treated, and the free volume concept is established and in turn is related to the diffusion coefficient yielding the following formula: Dσ = Doe(6 to 10)σ/G where Dσ and Do are the diffusion coefficients in the presence and absence of stress respectively, G is the shear modulus, and σ is the stress.
Abstract: The effect of stress on the diffusion of water in glassy polymers is analytically treated. Utilizing the free volume concept the effect of stress on the free volume fraction is established and in turn is related to the diffusion coefficient yielding the following formula: Dσ = Doe(6 to 10)σ/G where Dσ and Do are the diffusion coefficients in the presence and absence of stress respectively, G is the shear modulus, and σ is the stress. Experiments are described which demonstrate that in a bent epoxy bar, more water is picked up at the tension side than at the compression side. Theory and experiment are discussed and compared.
92 citations
TL;DR: In this paper, the strong flame inhibition by metal compounds when added at low volume fraction is found to occur through the gas-phase catalytic cycles leading to a highly effective radical recombination in the reaction zone.
92 citations
TL;DR: In this paper, photo-cross-linked, temperature-responsive hydrogel layers in water were used to study the mechanical properties of photo cross-linkable linear polymers based on N-isopropylacrylamide and 2-(dimethylmaleimido)-N-ethyl-acryamide.
Abstract: Atomic force microscopy (AFM) was used to study the mechanical properties of photo-cross-linked, temperature-responsive hydrogel layers in water. Photo-cross-linkable linear polymers based on N-isopropylacrylamide and 2-(dimethylmaleimido)-N-ethyl-acrylamide were spin-coated to produce uniform thin films of cross-linked responsive hydrogels. These films were imaged using AFM, and force−distance curves were used to measure the temperature-dependent elastic modulus. The volume phase transition of the hydrogel layers is constrained by the presence of a fixed substrate, and the length scale of these effects is related to the modulus. These materials were also studied with surface plasmon resonance and optical waveguide spectroscopy to determine the polymer volume fraction as a function of the temperature. The modulus varies as a function of the polymer volume fraction and is in good agreement with previous measurements on bulk hydrogels. The effect of the cross-linking density and degree of ionization on the ...
92 citations
TL;DR: In this article, a three-level general factorial design was employed to evaluate the effect of parameters of temperature, volume fraction and nanoparticle diameter on thermal conductivity coefficient of MgO/water nanofluids.
92 citations
TL;DR: In this paper, a multi-scale microstructural computer model is applied to computing the chloride diffusivities of concretes with various mixture proportions and projected degrees of hydration, and a response surface design has been executed and least squares regression used to develop a simple equation for predicting chloride ion diffusivity in concrete based on these three parameters.
Abstract: The ability to predict the expected chloride diffusivity of a concrete based on its mixture proportions and field-curing conditions would be of great benefit both in predicting service life of the concrete and in developing durability-based design codes. Here, a multi-scale microstructural computer model is applied to computing the chloride diffusivities of concretes with various mixture proportions and projected degrees of hydration. A fractional factorial experimental design has been implemented to study the effects in the model of seven major variables: water-to-cement (W/C) ratio, degree of hydration, aggregate volume fraction, coarse aggregate particle size distribution, fine aggregate particle size distribution, interfacial transition zone thickness, and air content. Based on this experimental design, W/C ratio, degree of hydration, and aggregate volume fraction have been identified as the three major variables influencing concrete diffusivity in the model. Following identification of the significant variables, a response surface design has been executed and least squares regression used to develop a simple equation for predicting chloride ion diffusivity in concrete based on these three parameters. This simple equation essentially summarizes the complicated simulations involved in computing the model response. Finally, simulations have been conducted to examine the extent of the surface layer in cast-in-place concrete, where the local aggregate volume fraction near the surface is less than that to be found in the bulk of the concrete.
92 citations