New triazine-based linker used to cross-link PEI into an unsupported adsorbent with high CO₂ uptake at ambient temperature.

Novel joining methods are crucial for the aerospace industry to repair components damaged in the high stress, high cycle environment of the jet turbine engine. Powder interlayer bonding (PIB) is a novel joining technique that is being explored for use in the aerospace industry. PIB involves the use of a powder interlayer between two faying surfaces alongside a localised temperature gradient and compressive force to produce one joined workpiece. The use of a localised temperature gradient not only reduces the heat affected zone (HAZ) but also reduces the energy requirements for the process as only a small area of the component needs to be elevated in temperature. Nickel-based superalloys are commonly used in the gas turbine engine due to their superior mechanical properties that are maintained even under the most elevated temperatures experienced in the jet turbine engine. It is therefore essential these alloys can be easily repaired. Conventional joining methods such as friction welding have proved difficult for new generation nickel-based superalloys; therefore, there is much interest in PIB as an alternative repair technology. This study shows the potential of PIB to join dissimilar nickel-based superalloys: bonds with very little porosity were observed after only a short processing time.

Cultivating microalgae requires a nitrogen and phosphorous feed source. Anaerobic digestion waste (digestate) provides a cheap sustainable feedstock for these materials. Previous studies have successfully demonstrated the feasibility of nutrient recovery and subsequent algae growth. There is now a need to fully characterise digestate filtration to improve our understanding of this process prior to its commercialisation. In this work, digestate filtration is characterised at bench scale using frontal (dead-end) filtration and a 100 kDa MWCO ultrafiltration membrane. Our experiments demonstrated rapid cake formation causing significant flux decline. The steady-state permeate flux for digestate was 2.4 to 4.8 L m⁻² h⁻¹, a reduction of ~90% compared to clean water flux. The specific cake resistance was ~1015 m kg⁻¹ and the compressibility index 1.07. A series of four filtration and cleaning cycles showed 90% flux recovery following a clean water wash. Digestate filtration was then evaluated at a commercial scale using crossflow and the KOCH ABCOR^® tubular membrane (100 kDa MWCO). The results were similar to those at the bench scale, i.e., rapid initial fouling leading to a period of steady-state flux (approximately 7 L m⁻² h⁻¹). The commercial membrane was flushed with water and diluted bleach after each use, and a digestate permeate flux decline of only 4.8% over a 12-month active use period was observed. The present research provides bench scale characterisation and demonstrates the commercial scale operation of anaerobic digestate filtration using ultrafiltration. The overall filtration performance was excellent, and the process can now be scaled to any operational capacity.

Advanced High Strength Steels (AHSS) are seeing a dramatic usage increase in order to achieve the reduction in weight required for automotive vehicles to adhere to new legislation on emissions. This has resulted in the increase of use of Calcium (Ca), as a means of both oxide and sulphide-based inclusion control. However, this process is not well understood, with no definitive answer on the level of Ca required to obtain adequate modification of the inclusion population within the steel. As a result, this thesis studied the level of Ca addition applied to the dual-phase steel grade, FB590, by analysing its Calcium Sulphur Ratio (Ca:S). This allowed for the level of modification needed to obtain the required mechanical properties to be studied. It was discovered that even at the low Ca:S of 0.23, sufficient modification of the inclusions was achieved to obtain these properties. Samples across the entire Ca:S range obtained a substantial increase in the number of ‘globular’ inclusions when compared to non-Calcium treated samples. The second aspect of this project was to automate the process of analysing the inclusion populations within the steel. Typically, this is done manually and is very time consuming. The resulting automated process analysed a stitched image of the entire sample surface (200mm2) taken at a typical magnification (100x) and was conducted as closely as possible to the BS EN 10247 and ASTM E45 standards. A custom macro was written that allowed this image to be broken up into fields, each of which were analysed individually, for both inclusion population and size. This method proved significantly less time consuming while generating a vast amount of data that would be unavailable utilising standard analysis techniques. The key problem with the technique, however, is that it did not include the ‘grouped’ inclusions stated in the standards. Nevertheless, EDS analysis proved that a significant proportion of these inclusions were in fact distinct globular inclusions and therefore not the inclusions separated by the polishing process that the standard assumes. A suggestion has been made to conduct all future inclusion analysis on FB590 at 500x magnification so as to reduce the negative effects of pixel size. A series of different regions would then be analysed to better ensure the accuracy of the results.