| 1. |
- MacGregor-Ramiasa, M., et al.
(författare)
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Magnetic alignment of nontronite dispersions
- 2015
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Ingår i: Applied Clay Science. - : Elsevier BV. - 0169-1317. ; 116-117, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- The time dependent alignment of exfoliated nontronite dispersions subjected to moderate magnetic field strengths (B.
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| 2. |
- Röding, Magnus, et al.
(författare)
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The power of heterogeneity : Parameter relationships from distributions
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Complex scientific data is becoming the norm, many disciplines are growing immensely data-rich, and higher-dimensional measurements are performed to resolve complex relationships between parameters. Inherently multi-dimensional measurements can directly provide information on both the distributions of individual parameters and the relationships between them, such as in nuclear magnetic resonance and optical spectroscopy. However, when data originates from different measurements and comes in different forms, resolving parameter relationships is a matter of data analysis rather than experiment. We present a method for resolving relationships between parameters that are distributed individually and also correlated. In two case studies, we model the relationships between diameter and luminescence properties of quantum dots and the relationship between molecular weight and diffusion coefficient for polymers. Although it is expected that resolving complicated correlated relationships require inherently multi-dimensional measurements, our method constitutes a useful contribution to the modelling of quantitative relationships between correlated parameters and measurements. We emphasise the general applicability of the method in fields where heterogeneity and complex distributions of parameters are obstacles to scientific insight.
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| 3. |
- Williamson, Nathan H., et al.
(författare)
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Obtaining T1-T2 distribution functions from 1-dimensional T1 and T2 measurements : The pseudo 2-D relaxation model
- 2016
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Ingår i: Journal of magnetic resonance. - : Elsevier BV. - 1090-7807 .- 1096-0856. ; 269, s. 186-195
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Tidskriftsartikel (refereegranskat)abstract
- We present the pseudo 2-D relaxation model (P2DRM), a method to estimate multidimensional probability distributions of material parameters from independent 1-D measurements. We illustrate its use on 1-D T1 and T2 relaxation measurements of saturated rock and evaluate it on both simulated and experimental T1-T2 correlation measurement data sets. Results were in excellent agreement with the actual, known 2-D distribution in the case of the simulated data set. In both the simulated and experimental case, the functional relationships between T1 and T2 were in good agreement with the T1-T2 correlation maps from the 2-D inverse Laplace transform of the full 2-D data sets. When a 1-D CPMG experiment is combined with a rapid T1 measurement, the P2DRM provides a double-shot method for obtaining a T1-T2 relationship, with significantly decreased experimental time in comparison to the full T1-T2 correlation measurement.
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| 4. |
- Williamson, Nathan H., et al.
(författare)
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Scaling exponent and dispersity of polymers in solution by diffusion NMR
- 2017
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 493, s. 393-397
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Tidskriftsartikel (refereegranskat)abstract
- Molecular mass distribution measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) spectroscopy currently require prior knowledge of scaling parameters to convert from polymer self-diffusion coefficient to molecular mass. Reversing the problem, we utilize the scaling relation as prior knowledge to uncover the scaling exponent from within the PGSE data. Thus, the scaling exponent—a measure of polymer conformation and solvent quality—and the dispersity (Mw/Mn) are obtainable from one simple PGSE experiment. The method utilizes constraints and parametric distribution models in a two-step fitting routine involving first the mass-weighted signal and second the number-weighted signal. The method is developed using lognormal and gamma distribution models and tested on experimental PGSE attenuation of the terminal methylene signal and on the sum of all methylene signals of polyethylene glycol in D2O. Scaling exponent and dispersity estimates agree with known values in the majority of instances, leading to the potential application of the method to polymers for which characterization is not possible with alternative techniques.
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| 5. |
- Williamson, Nathan H., et al.
(författare)
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The lognormal and gamma distribution models for estimating molecular weight distributions of polymers using PGSE NMR
- 2016
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Ingår i: Journal of magnetic resonance. - : Academic Press. - 1090-7807 .- 1096-0856. ; 267, s. 54-62
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Tidskriftsartikel (refereegranskat)abstract
- We present comprehensive derivations for the statistical models and methods for the use of pulsed gradient spin echo (PGSE) NMR to characterize the molecular weight distribution of polymers via the well-known scaling law relating diffusion coefficients and molecular weights. We cover the lognormal and gamma distribution models and linear combinations of these distributions. Although the focus is on methodology, we illustrate the use experimentally with three polystyrene samples, comparing the NMR results to gel permeation chromatography (GPC) measurements, test the accuracy and noise-sensitivity on simulated data, and provide code for implementation.
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| 6. |
- Williamson, Nathan H., et al.
(författare)
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The pseudo 2-D relaxation model for obtaining T1-T2 relationships from 1-D T1 and T2 measurements of fluid in porous media
- 2018
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 269, s. 191-194
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Tidskriftsartikel (refereegranskat)abstract
- NMR spin-lattice (T1) and spin-spin (T2) relaxation times and their inter-relation possess information on fluid behaviour in porous media. To elicit this information we utilize the pseudo 2-D relaxation model (P2DRM), which deduces the T1-T2 functional relationship from independent 1-D T1 and T2 measurements. Through model simulations we show empirically that the P2DRM accurately estimates T1-T2 relationships even when the marginal distributions of the true joint T1-T2 distribution are unknown or cannot be modeled. Estimates of the T1:. T2 ratio for fluid interacting with pore surfaces remain robust when the P2DRM is applied to simulations of rapidly acquired data. Therefore, the P2DRM can be useful in situations where experimental time is limited.
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| 7. |
- Abrahamsson, Christoffer, 1984, et al.
(författare)
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Magnetic orientation of nontronite clay in aqueous dispersions and its effect on water diffusion
- 2015
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 437, s. 205-210
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Tidskriftsartikel (refereegranskat)abstract
- The diffusion rate of water in dilute clay dispersions depends on particle concentration, size, shape, aggregation and water-particle interactions. As nontronite clay particles magnetically align parallel to the magnetic field, directional self-diffusion anisotropy can be created within such dispersion. Here we study water diffusion in exfoliated nontronite clay dispersions by diffusion NMR and time-dependant 1H-NMR-imaging profiles. The dispersion clay concentration was varied between 0.3 and 0.7 vol%. After magnetic alignment of the clay particles in these dispersions a maximum difference of 20% was measured between the parallel and perpendicular self-diffusion coefficients in the dispersion with 0.7 vol% clay. A method was developed to measure water diffusion within the dispersion in the absence of a magnetic field (random clay orientation) as this is not possible with standard diffusion NMR. However, no significant difference in self-diffusion coefficient between random and aligned dispersions could be observed.
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| 8. |
- Andersson Trojer, Markus, 1981, et al.
(författare)
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Use of microcapsules as controlled release devices for coatings
- 2015
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Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 0001-8686. ; 222, s. 18-43
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Tidskriftsartikel (refereegranskat)abstract
- Biofouling of surfaces is a considerable problem in many industrial sectors and for the public community in general. The problem is usually approached by the use of functional coatings and most of such antifouling coatings rely on the effect of biocides. However, a substantial drawback is the poor control over the release of the biocide as well as its degradation in the paint. Encapsulation of the biocides in microcapsules is a promising approach that may overcome some of the problems associated with the more traditional ways of incorporating the antifouling agent into the formulation. In this review, we summarize more than a decade of microcapsule research from our lab as well as from other groups working on this topic. Focus will be on two coacervation-based encapsulation techniques; the internal phase separation method and the double emulsion method, which together enable the encapsulation of a broad spectrum of biocides with different physicochemical properties. The release of the biocide from core-shell particles and from encapsulated biocides in coatings is treated in detail. The release behaviour is interpreted in terms of the physicochemical properties of the core-shell particle and the coating matrix. In addition, special attention is given to the experimental release methodology and the implementation of proper diffusion models to describe the release. At the end of the review examples of antifouling properties of some coatings against common biofoulers are presented.
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| 9. |
- Hamngren Blomqvist, Charlotte, 1984, et al.
(författare)
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Pore size effects on convective flow and diffusion through nanoporous silica gels
- 2015
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 484, s. 288-296
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Tidskriftsartikel (refereegranskat)abstract
- Material structure has great impact on mass transport properties, a relationship that needs to be understood on several length scales. Describing and controlling the properties of flow through soft materials are both challenges concerning the industrial use of gel structures. This paper reports on how the porous structure in nanoporous materials affects the water transport through them. We used three different silica gels with large differences in the pore sizes but of equal silica concentration. Particle morphology and gel structure were studied using high-resolution transmission electron microscopy and image analysis to estimate the pore size distribution and intrinsic surface area of each gel. The mass transport was studied using a flow measurement setup and nuclear magnetic resonance diffusometry. The average pore size ranged from approximately 500. nm down to approximately 40. nm. An acknowledged limit for convective flow to occur is in the pore size range between 100 and 200. nm. The results verified the existence of a non-linear relationship between pore size and liquid flow at length scales below 500. nm, experimentally. A factor of 4.3 in flow speed separated the coarser gel from the other two, which presented almost identical flow speed data despite a factor 3 in pore size difference. In the setup, the mass transport in the gel with the largest pores was flow dominated, while the mass transport in the finer gels was diffusion dominated. Besides providing new insights into mass transport as a function of pore sizes, we conclude that three-dimensional analysis of the structures is needed for a comprehensive understanding of the correlation between structure and mass transport properties.
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| 10. |
- Kaur, Simarpreet Pal, et al.
(författare)
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Unhindered copper uptake by glutaraldehyde-polyethyleneimine coatings in an artificial seawater model system with adsorbed swollen polysaccharides and competing ligand EDTA
- 2017
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Ingår i: Biofouling (Print). - : Taylor and Francis Ltd.. - 0892-7014 .- 1029-2454. ; 33:2, s. 184-194
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Tidskriftsartikel (refereegranskat)abstract
- Shortly after a surface is submerged in the sea, a conditioning film is generally formed by adsorption of organic molecules, such as polysaccharides. This could affect transport of molecules and ions between the seawater and the surface. An artificial seawater model system was developed to understand how adsorbed polysaccharides impact copper binding by glutaraldehyde-crosslinked polyethyleneimine coatings. Coating performance was also determined when competed against copper-chelating EDTA. Polysaccharide adsorption and copper binding and distribution were investigated using advanced analytical techniques, including depth-resolved time-of-flight secondary ion mass spectroscopy, grazing incidence X-ray absorption near-edge spectroscopy, quartz crystal microbalance with dissipation monitoring and X-ray photoelectron spectroscopy. In artificial seawater, the polysaccharides adsorbed in a swollen state that copper readily penetrated and the glutaraldehyde-polyethyleneimine coatings outcompeted EDTA for copper binding. Furthermore, the depth distribution of copper species was determined with nanometre precision. The results are highly relevant for copper-binding and copper-releasing materials in seawater.
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