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Papers by Kathryn Waldron

Road Materials and Pavement Design, 2012

ABSTRACT The phase morphology of SBS polymer modified binders was studied using a fluorescence mi... more ABSTRACT The phase morphology of SBS polymer modified binders was studied using a fluorescence microscope and dynamic shear rheometer (DSR). The morphology at high temperature was determined by rapidly cooling small samples, and thus ‘freezing’ the morphology in microscope slides and in DSR samples. As SBS binders are cooled from their manufacturing temperature there is an increasing tendency for a single phase structure (if one is present) to become a two-phase structure with irregular globules of SBS distributed in an asphaltene-rich phase. The morphology of field samples of asphalts and sprayed seals was also studied and shown to be determined, in the case of asphalt, by the relatively slow cooling rate of the binder during transport and compaction. On the other hand, sprayed seal binders cool rapidly and their morphology reflects that present in the binder at spraying temperatures. Thus the same binder may have different properties when used in an asphalt and a seal. It is, therefore, desirable to ensure that the morphology in specification test samples is the same as that in the field application of a binder. This may mean modifying sample preparation procedures. The compatibility of the bitumen used to manufacture an SBS binder had an important effect on morphology, with incompatible bitumens forming globular particles but binders made with compatible bitumens retaining a homogeneous appearance. Morphology appeared to have little effect on viscosity but could have a major effect on elasticity. Rutting performance is unlikely to be influenced by morphology since it has been shown to be related to binder viscosity. Fatigue testing of asphalt beams with different morphology binders suggested that morphology might affect fatigue life.

Journal of industrial microbiology & biotechnology, 2011

Hematopoietic stem cells (HSCs) are extremely useful in treating a wide range of diseases and hav... more Hematopoietic stem cells (HSCs) are extremely useful in treating a wide range of diseases and have a variety of useful research applications. However, the routinely generated low in vitro concentrations of HSCs from current bioreactor manufacturing systems has been a hindrance to the full-scale application of these essential cellular materials. This has made the search for novel bioreactor systems for high-concentration HSC production a major research endeavour. This review addresses process challenges in relation to bioreactor development and optimisation for high-density HSC production under effective monitoring of essential culture parameters, such as pH, dissolved oxygen and nutrient uptake. It discusses different process strategies and bioreactor configurations for HSCs production from a commercial viability perspective, and also discusses recent advances in the field.

Chemical Engineering Science, 2015

ABSTRACT Spray dried mesoporous silica microspheres have the potential to be used in a vast numbe... more ABSTRACT Spray dried mesoporous silica microspheres have the potential to be used in a vast number of applications. However, the highly ordered mesostructure is often rendered inaccessible by the presence of a thin skin on the particle formed by spray drying. Here we post-treated these silica microspheres hydrothermally to increase the pore size of the mesostructures, as well as to open up the skin. The hydrothermal treatment also improved the long-range ordering of some disordered regions that were formed due to the rapid nature of self-assembly in spray-drying, as evidenced by the SAXS patterns after treatment. Increasing the hydrothermal treatment temperature above 100 °C increased the pore size, while surface area, wall thickness, and the micropore volume decreased as a result of the densification of the silica walls. The effect of time on the hydrothermal treatment (6–24 h) was less pronounced on the long-range ordering and pore size. Instead the treatment time had a more significant impact to reduce the micropore volume, indicating that the long-range ordering is improved within 6 h. While the densification of the pore walls and hence reduction of the micropore volume occurs at a slower rate over a period of 24 h. To compare the performance of hydrothermally treated and untreated particles, both materials were used for static and packed bed adsorption of lysozyme. The treated particles significantly out-performed (>260% capacity) the untreated particles, demonstrating a faster adsorption in the packed bed, whereas almost no adsorption was observed for the untreated material due to the barrier presented by the skin.

J. Mater. Chem. A, 2014

ABSTRACT The effects of inlet drying temperature, initial solute content, hydrolysis time of the ... more ABSTRACT The effects of inlet drying temperature, initial solute content, hydrolysis time of the precursor, and the choice of solvent were analysed in the synthesis of large (~ 50 µm) and uniform SBA-15 microspheres via spray drying. Higher temperatures led to microspheres with larger particles sizes due to a faster evaporation rate. Meanwhile, particle size was proportional to the solute content, thus SBA-15 microspheres with tuneable particle size over a wide range were obtained. Highly ordered mesostructures were assembled for SBA-15 microspheres obtained from initial solute contents between 5 and 12 wt%. Solute contents of lower than 5 wt% or higher than 12 wt% lead to less ordered mesostructures. Increasing hydrolysis time of the precursor solution from 1 hour to 2 hours allowed more cross-linking of silica, thus increasing surface tension forces and resulting in hollow, “bowl-like” particles. Notably, highly oriented mesopores were developed in the “bowl-like” particles. The use of water instead of ethanol as a solvent resulted in disordered “worm-like” mesostructure, with “bowl-like” particles due to the slower evaporation rate. The unique set up of our spray dryer enabled the collection of particles immediately after spray drying. Analyses via SAXS and TEM indicated that the mesostructures were still mobile immediately after spray drying, confirming the so-called “wet-pocket” phenomenon that determined the final mesostructures.

Journal of Colloid and Interface Science, 2014

Road Materials and Pavement Design, 2012

ABSTRACT The phase morphology of SBS polymer modified binders was studied using a fluorescence mi... more ABSTRACT The phase morphology of SBS polymer modified binders was studied using a fluorescence microscope and dynamic shear rheometer (DSR). The morphology at high temperature was determined by rapidly cooling small samples, and thus ‘freezing’ the morphology in microscope slides and in DSR samples. As SBS binders are cooled from their manufacturing temperature there is an increasing tendency for a single phase structure (if one is present) to become a two-phase structure with irregular globules of SBS distributed in an asphaltene-rich phase. The morphology of field samples of asphalts and sprayed seals was also studied and shown to be determined, in the case of asphalt, by the relatively slow cooling rate of the binder during transport and compaction. On the other hand, sprayed seal binders cool rapidly and their morphology reflects that present in the binder at spraying temperatures. Thus the same binder may have different properties when used in an asphalt and a seal. It is, therefore, desirable to ensure that the morphology in specification test samples is the same as that in the field application of a binder. This may mean modifying sample preparation procedures. The compatibility of the bitumen used to manufacture an SBS binder had an important effect on morphology, with incompatible bitumens forming globular particles but binders made with compatible bitumens retaining a homogeneous appearance. Morphology appeared to have little effect on viscosity but could have a major effect on elasticity. Rutting performance is unlikely to be influenced by morphology since it has been shown to be related to binder viscosity. Fatigue testing of asphalt beams with different morphology binders suggested that morphology might affect fatigue life.

Journal of industrial microbiology & biotechnology, 2011

Hematopoietic stem cells (HSCs) are extremely useful in treating a wide range of diseases and hav... more Hematopoietic stem cells (HSCs) are extremely useful in treating a wide range of diseases and have a variety of useful research applications. However, the routinely generated low in vitro concentrations of HSCs from current bioreactor manufacturing systems has been a hindrance to the full-scale application of these essential cellular materials. This has made the search for novel bioreactor systems for high-concentration HSC production a major research endeavour. This review addresses process challenges in relation to bioreactor development and optimisation for high-density HSC production under effective monitoring of essential culture parameters, such as pH, dissolved oxygen and nutrient uptake. It discusses different process strategies and bioreactor configurations for HSCs production from a commercial viability perspective, and also discusses recent advances in the field.

Chemical Engineering Science, 2015

ABSTRACT Spray dried mesoporous silica microspheres have the potential to be used in a vast numbe... more ABSTRACT Spray dried mesoporous silica microspheres have the potential to be used in a vast number of applications. However, the highly ordered mesostructure is often rendered inaccessible by the presence of a thin skin on the particle formed by spray drying. Here we post-treated these silica microspheres hydrothermally to increase the pore size of the mesostructures, as well as to open up the skin. The hydrothermal treatment also improved the long-range ordering of some disordered regions that were formed due to the rapid nature of self-assembly in spray-drying, as evidenced by the SAXS patterns after treatment. Increasing the hydrothermal treatment temperature above 100 °C increased the pore size, while surface area, wall thickness, and the micropore volume decreased as a result of the densification of the silica walls. The effect of time on the hydrothermal treatment (6–24 h) was less pronounced on the long-range ordering and pore size. Instead the treatment time had a more significant impact to reduce the micropore volume, indicating that the long-range ordering is improved within 6 h. While the densification of the pore walls and hence reduction of the micropore volume occurs at a slower rate over a period of 24 h. To compare the performance of hydrothermally treated and untreated particles, both materials were used for static and packed bed adsorption of lysozyme. The treated particles significantly out-performed (>260% capacity) the untreated particles, demonstrating a faster adsorption in the packed bed, whereas almost no adsorption was observed for the untreated material due to the barrier presented by the skin.

J. Mater. Chem. A, 2014

ABSTRACT The effects of inlet drying temperature, initial solute content, hydrolysis time of the ... more ABSTRACT The effects of inlet drying temperature, initial solute content, hydrolysis time of the precursor, and the choice of solvent were analysed in the synthesis of large (~ 50 µm) and uniform SBA-15 microspheres via spray drying. Higher temperatures led to microspheres with larger particles sizes due to a faster evaporation rate. Meanwhile, particle size was proportional to the solute content, thus SBA-15 microspheres with tuneable particle size over a wide range were obtained. Highly ordered mesostructures were assembled for SBA-15 microspheres obtained from initial solute contents between 5 and 12 wt%. Solute contents of lower than 5 wt% or higher than 12 wt% lead to less ordered mesostructures. Increasing hydrolysis time of the precursor solution from 1 hour to 2 hours allowed more cross-linking of silica, thus increasing surface tension forces and resulting in hollow, “bowl-like” particles. Notably, highly oriented mesopores were developed in the “bowl-like” particles. The use of water instead of ethanol as a solvent resulted in disordered “worm-like” mesostructure, with “bowl-like” particles due to the slower evaporation rate. The unique set up of our spray dryer enabled the collection of particles immediately after spray drying. Analyses via SAXS and TEM indicated that the mesostructures were still mobile immediately after spray drying, confirming the so-called “wet-pocket” phenomenon that determined the final mesostructures.

Journal of Colloid and Interface Science, 2014