The remarkable optoelectronic properties of metal halide perovskites have generated intense resea... more The remarkable optoelectronic properties of metal halide perovskites have generated intense research interest over the last few years. The ability to control and manipulate the crystallisation and stoichiometry of perovskite...
New membrane-based molecular separation processes are an essential part of the strategy for susta... more New membrane-based molecular separation processes are an essential part of the strategy for sustainable chemical production. A large literature on 'hybrid' or 'mixed-matrix' membranes exists, in which nanoparticles of a higher-performance porous material are dispersed in a polymeric matrix to boost performance. We demonstrate that the hybrid membrane concept can be redefined to achieve much higher performance if the membrane matrix and the dispersed phase are both nanoporous crystalline materials, with no polymeric phase. As the first example of such a system, we find that surface-treated nanoparticles of the zeolite MFI can be incorporated in situ during growth of a polycrystalline membrane of the MOF ZIF-8. The resulting all-nanoporous hybrid membrane shows propylene/propane separation characteristics that exceed known upper-bound performance limits defined for polymers, nanoporous materials, and polymer-based hybrid membranes. This serves as a starting point for a new generation of chemical separation membranes containing interconnected nanoporous crystalline phases.
... spectrometer. Light Scattering. The 86.6-kg/mol POE and perdeuterated 59.2-kg/mol POE were an... more ... spectrometer. Light Scattering. The 86.6-kg/mol POE and perdeuterated 59.2-kg/mol POE were analyzed at 25 °C using a Wyatt DAWN EOS multi-angle light scattering detector in chromatography mode (1 mL/min). Light scattered ...
An experimental setup is described for the automated recording of sorption isotherms by NMR exper... more An experimental setup is described for the automated recording of sorption isotherms by NMR experiments at precisely defined levels of relative humidity (RH). Implementation is demonstrated for a cotton fabric; Bloch decays. T1 and T2* relaxation times were measured at predefined steps of increasing and decreasing relative humidities (RHs) so that a complete isotherm of NMR properties was obtained. Bloch decays were analyzed by fitting to relaxation functions consisting or a slow- and a fast-relaxing component. The fraction of slow-relaxing component was greater than the fraction of sorbed moisture determined from gravimetric sorption data. The excess slow-relaxing component was attributed to plasticized segments of the formerly rigid cellulose matrix. T1 and T2* sorption isotherms exhibit hysteresis similar to gravimetric sorption isotherms. However, correlating RH to moisture content (MC) reveals that both relaxation constants depend only on MC, and not on the history of moisture ...
The effect of lithium ion on the ordering of water in water-saturated nitrobenzene has been probe... more The effect of lithium ion on the ordering of water in water-saturated nitrobenzene has been probed by 2H NMR, diffusion ordered spectroscopy and neutron scattering. It was shown that increased water concentration in LiClO4/wet nitrobenzene results in the formation of a metastable solvatomer with mixed water and nitrobenzene character, Li+(W/NB). This species is shown to decay over hours to two solvatomers, one dominated by nitrobenzene Li+(NB) and the other dominated by water Li+(W). To confirm the assignment of these solvation states, diffusion ordered deuterium NMR spectroscopy has been used to elucidate the hydrodynamic radii of these solvatomers. Neutron scattering yields vibrational spectroscopy information that shows how addition of lithium to the nitrobenzene/water system results in relatively slow self-organization of the water environment (hours).
Magnetic resonance imaging (MRI) is used to characterize fluid distribution and movement in texti... more Magnetic resonance imaging (MRI) is used to characterize fluid distribution and movement in textiles. The standard spin-echo sequence commonly used in the medical field is not suitable for quantitative imaging of moisture profiles in textiles because the echo time duration allows too much time for signal loss. The signal attenuation is greater for low moisture content and less pronounced for polypropylene than it is for cotton and other materials with higher surface concentrations of water-binding functional groups. A single-point imaging (SPI) sequence, also called constant-time imaging, provides quantitative profile images on industrially relevant timescales. This is demonstrated by measuring profiles of water in wet unbacked nylon cut-pile carpet during a drying process. A comprehensive introduction to MRI is provided with special consideration of water, textiles, and the relevant chemical and physical influences on the MRI time signal and resulting image.
Magnetic resonance imaging (MRI) and a pilot-scale laboratory through-air dryer are used to study... more Magnetic resonance imaging (MRI) and a pilot-scale laboratory through-air dryer are used to study through-air drying of unbacked tufted nylon carpets. MRI is used to study the effect of the vacuum extraction procedure on local moisture distribution within the carpet and to measure local moisture profiles during through-air drying where airflow rate is held constant. The effects of several process and carpet construction parameters on drying are discussed.
Physica A: Statistical Mechanics and its Applications, 1993
New multidimensional NMR relaxation experiments are described. These experiments allow the measur... more New multidimensional NMR relaxation experiments are described. These experiments allow the measurement of slowly decaying relaxation functions for selected subensembles. They are applied for chain deuterated polystyrene at temperatures slightly above the caloric glass transition. The usual nonexponential loss of correlation is observed for the overall sample. However, a subensemble of slow components can be selected. An analysis of the relaxation functions in terms of the Kohlrausch-Williams-Watts function shows that the relaxation function of the selected components corresponds to a narrower distribution of correlation times than that of the entire sample. This gives clear evidence of a spatially heterogeneous distribution of correlation times and not an intrinsically nonexponential loss of correlation in a homogeneous system. For the hydrocarbon chain of polystyrene the observed nonexponential loss of correlation due to motions of the 100 Hz range (alpha-process) is linked to the nonexponential T1 relaxation observed close to Tg which is dominated by rapid motions with spectral density in the range of 100 MHz (beta-process). Hence in spatial regions where the alpha-relaxation is slow, also slow T1 relaxation is observed.
The remarkable optoelectronic properties of metal halide perovskites have generated intense resea... more The remarkable optoelectronic properties of metal halide perovskites have generated intense research interest over the last few years. The ability to control and manipulate the crystallisation and stoichiometry of perovskite...
New membrane-based molecular separation processes are an essential part of the strategy for susta... more New membrane-based molecular separation processes are an essential part of the strategy for sustainable chemical production. A large literature on 'hybrid' or 'mixed-matrix' membranes exists, in which nanoparticles of a higher-performance porous material are dispersed in a polymeric matrix to boost performance. We demonstrate that the hybrid membrane concept can be redefined to achieve much higher performance if the membrane matrix and the dispersed phase are both nanoporous crystalline materials, with no polymeric phase. As the first example of such a system, we find that surface-treated nanoparticles of the zeolite MFI can be incorporated in situ during growth of a polycrystalline membrane of the MOF ZIF-8. The resulting all-nanoporous hybrid membrane shows propylene/propane separation characteristics that exceed known upper-bound performance limits defined for polymers, nanoporous materials, and polymer-based hybrid membranes. This serves as a starting point for a new generation of chemical separation membranes containing interconnected nanoporous crystalline phases.
... spectrometer. Light Scattering. The 86.6-kg/mol POE and perdeuterated 59.2-kg/mol POE were an... more ... spectrometer. Light Scattering. The 86.6-kg/mol POE and perdeuterated 59.2-kg/mol POE were analyzed at 25 °C using a Wyatt DAWN EOS multi-angle light scattering detector in chromatography mode (1 mL/min). Light scattered ...
An experimental setup is described for the automated recording of sorption isotherms by NMR exper... more An experimental setup is described for the automated recording of sorption isotherms by NMR experiments at precisely defined levels of relative humidity (RH). Implementation is demonstrated for a cotton fabric; Bloch decays. T1 and T2* relaxation times were measured at predefined steps of increasing and decreasing relative humidities (RHs) so that a complete isotherm of NMR properties was obtained. Bloch decays were analyzed by fitting to relaxation functions consisting or a slow- and a fast-relaxing component. The fraction of slow-relaxing component was greater than the fraction of sorbed moisture determined from gravimetric sorption data. The excess slow-relaxing component was attributed to plasticized segments of the formerly rigid cellulose matrix. T1 and T2* sorption isotherms exhibit hysteresis similar to gravimetric sorption isotherms. However, correlating RH to moisture content (MC) reveals that both relaxation constants depend only on MC, and not on the history of moisture ...
The effect of lithium ion on the ordering of water in water-saturated nitrobenzene has been probe... more The effect of lithium ion on the ordering of water in water-saturated nitrobenzene has been probed by 2H NMR, diffusion ordered spectroscopy and neutron scattering. It was shown that increased water concentration in LiClO4/wet nitrobenzene results in the formation of a metastable solvatomer with mixed water and nitrobenzene character, Li+(W/NB). This species is shown to decay over hours to two solvatomers, one dominated by nitrobenzene Li+(NB) and the other dominated by water Li+(W). To confirm the assignment of these solvation states, diffusion ordered deuterium NMR spectroscopy has been used to elucidate the hydrodynamic radii of these solvatomers. Neutron scattering yields vibrational spectroscopy information that shows how addition of lithium to the nitrobenzene/water system results in relatively slow self-organization of the water environment (hours).
Magnetic resonance imaging (MRI) is used to characterize fluid distribution and movement in texti... more Magnetic resonance imaging (MRI) is used to characterize fluid distribution and movement in textiles. The standard spin-echo sequence commonly used in the medical field is not suitable for quantitative imaging of moisture profiles in textiles because the echo time duration allows too much time for signal loss. The signal attenuation is greater for low moisture content and less pronounced for polypropylene than it is for cotton and other materials with higher surface concentrations of water-binding functional groups. A single-point imaging (SPI) sequence, also called constant-time imaging, provides quantitative profile images on industrially relevant timescales. This is demonstrated by measuring profiles of water in wet unbacked nylon cut-pile carpet during a drying process. A comprehensive introduction to MRI is provided with special consideration of water, textiles, and the relevant chemical and physical influences on the MRI time signal and resulting image.
Magnetic resonance imaging (MRI) and a pilot-scale laboratory through-air dryer are used to study... more Magnetic resonance imaging (MRI) and a pilot-scale laboratory through-air dryer are used to study through-air drying of unbacked tufted nylon carpets. MRI is used to study the effect of the vacuum extraction procedure on local moisture distribution within the carpet and to measure local moisture profiles during through-air drying where airflow rate is held constant. The effects of several process and carpet construction parameters on drying are discussed.
Physica A: Statistical Mechanics and its Applications, 1993
New multidimensional NMR relaxation experiments are described. These experiments allow the measur... more New multidimensional NMR relaxation experiments are described. These experiments allow the measurement of slowly decaying relaxation functions for selected subensembles. They are applied for chain deuterated polystyrene at temperatures slightly above the caloric glass transition. The usual nonexponential loss of correlation is observed for the overall sample. However, a subensemble of slow components can be selected. An analysis of the relaxation functions in terms of the Kohlrausch-Williams-Watts function shows that the relaxation function of the selected components corresponds to a narrower distribution of correlation times than that of the entire sample. This gives clear evidence of a spatially heterogeneous distribution of correlation times and not an intrinsically nonexponential loss of correlation in a homogeneous system. For the hydrocarbon chain of polystyrene the observed nonexponential loss of correlation due to motions of the 100 Hz range (alpha-process) is linked to the nonexponential T1 relaxation observed close to Tg which is dominated by rapid motions with spectral density in the range of 100 MHz (beta-process). Hence in spatial regions where the alpha-relaxation is slow, also slow T1 relaxation is observed.
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