A new look to non-Fickian diffusion

Ferreira, J. A.; Grassi, Mario; Gudiño, E.; Oliveira, Paula de

doi:10.1016/j.apm.2014.05.030

Cited by 48 publications

(56 citation statements)

References 13 publications

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“…All these homogenization approaches may be qualified as "Fickian diffusion," delivering diffusivity quantities which relate concentration gradients to molar fluxes. Limitations of such approaches have been extensively discussed, and it is of interest to review these limitations in the context of our work: Non-Fickian diffusion induces significant, non-negligible deforma-tions in the respective porous material, because of which the mathematical description of the diffusion process needs to be extended (as compared to the classical Fick's law), in order to take into account the interaction between deformation-induced stresses and Brownian motion (Ferreira et al 2015). This is, however, not the case in the problem studied here.…”

Section: Discussionmentioning

confidence: 99%

Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

et al. 2017

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Chloride ingress into concrete is a major cause for material degradation, such as cracking due to corrosion-induced steel reinforcement expansion. Corresponding transport processes encompass diffusion, convection, and migration, and their mathematical quantification as a function of the concrete composition remains an unrevealed enigma. Approaching the problem step by step, we here concentrate on the diffusivity of cement paste, and how it follows from the microstructural features of the material and from the chloride diffusivity in the capillary pore spaces. For this purpose, we employ advanced self-consistent homogenization theory as recently used for permeability upscaling, based on the resolution of the pore space as pore channels being oriented in all space directions, resulting in a quite compact analytical relation between porosity, pore diffusivity, and the overall diffusivity of the cement paste. This relation is supported by experiments and reconfirms the pivotal role that layered water most probably plays for the reduction of the pore diffusivity, with respect to the diffusivity found under the chemical condition of a bulk solution.Keywords Diffusion · Homogenization · Chlorides · Multiscale modeling · Layered water List of Symbols Mathematical operators divDivergence operator, applied to a vector field div Divergence operator, applied to a second-order tensor field grad Gradient operator on the microscopic observation scale of pore space

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Section: Discussionmentioning

confidence: 99%

Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

et al. 2017

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“…In 2005, Bruce Duncan, Jeannie Urquhart and Simon Roberts proposed an interrelationship between factors, for example the combination of stress and chemical exposure often as a critical degradation mechanism in the service performance of polymeric structures [11]. In 2011, Mark D. Placette, Xuejun Fan described their dual-stage diffusion model based on Fickian's Law for both stages of absorption and desorption [7,10]. In 2014, J.A.…”

Section: Introductionmentioning

confidence: 99%

“…In 2000, Y. Jack Weitsman in his research about the effects of fluids in polymeric composites mentioned the problem of anomalous diffusion and the need for more precise models [9]. Later in 2004, he proposed a coupled diffusion/damage model to describe the phenomenon, excluding chemical reactions and long-term effects [10]. In 2005, Bruce Duncan, Jeannie Urquhart and Simon Roberts proposed an interrelationship between factors, for example the combination of stress and chemical exposure often as a critical degradation mechanism in the service performance of polymeric structures [11].…”

Section: Introductionmentioning

confidence: 99%

“…The main idea was a new interpretation of the non-Fickian flux which leads to the establishment of a nonlinear functional relation for the strain, the viscoelastic diffusion coefficient and the Young modulus [12]. In 2015, based on the work of Abhishek Kumar and Samit Roy a novel viscoelasticity based model has been formulated, which aims to capture the response of the two-stage moisture absorption response, incorporating the effect of time-dependent relaxation of the material [10]. In the present work, a dual stage model is proposed for characterizing the water absorption behaviour of woven glass reinforced cyanate ester composites.…”

Section: Introductionmentioning

confidence: 99%

“…Both stages have been described by classic Fickian model. The investigation based on the experimental data includes not only the theoretical data fittings, but also the separation between the regions of physical and chemical ageing through the appropriate indicators-phenomena that are observed and their explanation through the structural discontinuities of the material [7][8][9][10][11]. It is important to mention that the research based on the non-Fickian behaviour has been enriched lately with more models that can describe these phenomena.…”

Section: Introductionmentioning

confidence: 99%

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Description of Anomalous Water Absorption Behaviour of Woven Glass Reinforced Cyanate Ester Composites

Kelverkloglou¹,

Kollia²,

Vavouliotis³

et al. 2016

Plastic and Polymer Technology

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This work studies the water absorption behaviour of woven glass fibre reinforced cyanate ester composites used in the plenum of the air conditioning pack of aircraft's environmental control system. For absorption tests, samples were immersed in distilled water baths at four different temperatures: 40°C, 60°C, 75°C and 90°C. In general, the composites have shown strong nonFickian behaviour. The progression of mass absorption is described analytically using a combination of Fickian diffusion and relaxation process. Thus for the temperatures of 40°C, 60°C and 75°C a dual stage model was used. At 90°C the material exhibits extreme non-Fickian behaviour due to chemical ageing procedures which cannot be accurately modeled. From the mass control analysis, lots of information is provided for the correlation between the temperature and the diffusion coefficient or the start of the moisture equilibrium. Also, the regions of physical and chemical ageing can be clearly distinguished, giving a good profile of the material behaviour at elevated temperature. The dual stage model that is proposed precisely describes the behaviour of these materials at different temperatures up to 75°C. The chemical ageing that is taking place at 90°C creates another profile that should be investigated in a more detailed level than macro-scale.

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Physicochemical evaluation of nanocomposite hydrogels with covalently incorporated poly(vinyl alcohol) functionalized graphene oxide

Olad

Eslamzadeh

Mirmohseni

2019

J of Applied Polymer Sci

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To avoid the negative effect of graphene oxide (GO) nanosheets aggregation in aqueous solutions on physicochemical properties of GO incorporated nanocomposite hydrogels, poly(vinyl alcohol)-functionalized GO (GO-es-PVA) are synthesized and are used for preparation of nanocomposite hydrogels. By graft copolymerization of GO-es-PVA with poly(AA-co-AAm) chains, the nanocomposite hydrogel samples with covalently incorporated GO-es-PVA are achieved. FTIR spectroscopy, XRD analysis, and SEM and EDAX techniques confirm successful synthesis process. It is clear that GO-es-PVA content has significant effect on physicochemical properties of nanocomposite hydrogels, such as improvement of the water uptake properties, porosity, and gel strength. The hydrogel sample with 1:80 mass ratio of GO-es-PVA/AAm has the best physicochemical properties due to the optimum amount of GO-es-PVA, which gives the hydrogel proper viscoelasticity as well as fine porosity and water uptake rate. Interpenetration of PVA chains into the polymeric networks makes the movement of the polymer chains easier, which leads to softer polymeric networks. This phenomenon is called plasticizing effect. The plasticizing nature of PVA and its high hydrophilicity are the main reasons for the fine physicochemical properties.

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A new look to non-Fickian diffusion

Cited by 48 publications

References 13 publications

Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

Description of Anomalous Water Absorption Behaviour of Woven Glass Reinforced Cyanate Ester Composites

Physicochemical evaluation of nanocomposite hydrogels with covalently incorporated poly(vinyl alcohol) functionalized graphene oxide

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