Mixed matrix carbon stainless steel (MMCSS) hollow fibres for gas separation

This work reports the preparation and investigation of novel mixed matrix carbon stainless steel (MMCSS) membranes. The study involves the production of MMCSS hollow fibres using SS particles of 6, 10, 16 and 45\ua0μm in diameter, polyetherimide as a polymeric binder and pyrolysis using a N inert atmosphere. As a result, the binder pyrolysed to carbon was retained in the hollow fibre structure, filling the voids between the SS particles. Smaller SS particles (6\ua0μm) yielded a bi-modal pore size distribution and superior mechanical properties. An interesting morphological feature was the formation of honeycomb-like carbon structures between the SS particles, attributed to the densification of the hollow fibre during pyrolysis at 1050\ua0°C. The MMCSS hollow fibres (6\ua0μm) delivered almost pure N for the separation of a synthetic flue gas composition (13% CO and 87% N). It was found that CO had a strong affinity to the surface of the MMCSS materials (isosteric heat of adsorption of 38\ua0kJ\ua0mol) whilst N was a non-absorbing gas. Therefore, CO permeation was controlled by surface diffusion whilst N was controlled by the faster Knudsen diffusion mechanism. For CO feed concentrations in excess of 13%, the CO diffusion increased as the excess CO could not adsorb on the fully saturated surface of the MMCSS hollow fibres, thus slightly reducing the N purity in the permeate stream

Where next on e-waste in Australia?

For almost two decades waste electrical and electronic equipment, WEEE or e-waste, has been considered a growing problem that has global consequences. The value of recovered materials, primarily in precious and base metals, has prompted some parts of the world to informally and inappropriately process e-waste causing serious environmental and human health issues. Efforts in tackling this issue have been limited and in many ways unsuccessful. The global rates for formal e-waste treatment are estimated to be below the 20% mark, with the majority of end-of-life (EoL) electronic devices still ending up in the landfills or processed through rudimentary means. Industrial confidentiality regarding device composition combined with insufficient reporting requirements has made the task of simply characterizing the problem difficult at a global scale. To address some of these key issues, this paper presents a critical overview of existing statistics and estimations for e-waste in an Australia context, including potential value and environmental risks associated with metals recovery. From our findings, in 2014, on average per person, Australians purchased 35 kg of electrical and electronic equipment (EEE) while disposed of 25 kg of WEEE, and possessed approximately 320 kg of EEE. The total amount of WEEE was estimated at 587 kt worth about US$ 370 million if all major metals are fully recovered. These results are presented over the period 2010–2014, detailed for major EEE product categories and metals, and followed by 2015–2024 forecast. Our future projection, with the base scenario fixing EEE sales at 35 kg per capita, predicts stabilization of e-waste generation in Australia at 28–29 kg per capita, with the total amount continuing to grow along with the population growth

The vulnerability of electric vehicle deployment to critical mineral supply

Electric vehicles are poised to play a large role in the decarbonisation of the transportation sector. World governments have pledged to bring 13 million plug-in electric vehicles on the road by 2020 and 100 million by 2030. The rapid expansion required to meet these targets, from a global stock of 5 million electric vehicles in 2018, has the potential to be constrained by material supply chains. This study has identified 7 key elements which are significant supply risks to the electric vehicle industry: battery grade natural graphite, lithium and cobalt for electric vehicle batteries, and the rare earth elements dysprosium, terbium, praseodymium and neodymium for electric vehicle motors. None of these elements are able to be substituted without (i) increasing the supply risk of the other constrained elements, or (ii) altering industry wide manufacturing processes. The inability to fully mitigate material supply risks at the required market expansion rates is a key issue for minimising carbon emissions from the transportation sector

The neck to particle ratio effect on the mechanical and morphological sintering features of porous stainless steel (SS) hollow fibers

The SS hollow fibers are prepared by extruding a mixture of SS particles and a polymeric binder in a phase inversion process followed by sintering at various temperatures (950-1100°C), resulting in the formation of void structures with a finger-like inner shell and a sponge-like outer shell. The mechanical strength increases by over 1000% as the SS particle size decreases from D=32 to 4μm, and by ≈150% as the sintering temperature increases from 950 to 1100°C. The best mechanical strength reached is 820MPa for the D=4μm SS hollow fiber sintered at 1100°C. The neck to particle (N/P) ratio proves to be a morphological measurement with good correlation with the mechanical properties of the SS hollow fibers. The mechanical strength increases by ≈44% (sintering effect) and ≈92% (particle size effect) from a N/P ratio of ≈0.8 to 0.9 for the smaller SS particle hollow fiber. At this ratio, the necks for the particles are in close contact and at the boundary of full coalescence, thus at the onset of fast mass transfer and grain formation/growth as diffusion increases significantly by six order of magnitude

Generating linked technology-socioeconomic scenarios for emerging energy transitions

The formulation and use of scenarios is now a fundamental part of national and global efforts to assess and plan for climate change. While scenario development initially focused on the technical dimensions of energy, emissions and climate response, in recent years parallel sets of shared socio-economic pathways have been developed to portray the values, motivations, and sociopolitical and institutional dimensions of these systems. However, integrating the technical and social aspects of evolving energy systems is difficult, with transitions dependent on highly uncertain technological advances, social preferences, political governance, climate urgency, and the interaction of these elements to maintain or overcome systemic inertia. A broad range of interdisciplinary knowledge is needed to structure and evaluate these processes, many of which involve a mix of qualitative and quantitative factors. To structure and facilitate the necessary linkages this paper presents an approach for generating a plausible range of scenarios for an emerging energy technology. The method considers influences among technical and social factors that can encourage or impede necessary improvements in the performance and cost of the technology, as well the processes affecting public acceptance and the establishment of governance structures necessary to support effective planning and implementation. A Bayesian network is used to capture relationships among the technological and socioeconomic factors likely to affect the probability that the technology will achieve significant penetration and adoption. The method is demonstrated for carbon capture and storage (CCS): a potential technology on the pathway to deep decarbonization. A preliminary set of expert elicitations is conducted to illustrate how relationships between these factors can be estimated. This establishes a prior or baseline network that can be subsequently analyzed by choosing either optimistic or pessimistic assumptions for respective groups of technical and social variables, identifying sets of key factors that limit or encourage successful deployment

Stainless steel hollow fibres – Sintering, morphology and mechanical properties

This work investigates the effects of the sintering conditions on the morphology and mechanical performance of stainless steel (SS) hollow fibres. It was found that the morphology of the green hollow fibre to a large extent predetermines the final morphology of the sintered hollow fibre. There is a set of conditions which produce hollow fibres with high mechanical strength over 1000 MPa such as using small SS particles (6 and 10 μm), PEI as the polymeric binder and minimal amounts of the viscosity modifier PVP (preferably close to 0 wt%), particle loadings higher than 50 wt%, and sintering temperatures between 1050 and 1100 °C. The ductility of the hollow fibres was not greatly affected by these parameters as flexural strain variations were very small, though sintering in argon resulted in the formation of a few larger pores which tended to propagate cracks, leading to lower flexural strain. The sintering process in inert gases resulted in mass transfer of residual carbon from the binder to the SS particle, leading to regions of rich and lean chromium carbides, though mechanical effects of these inclusions were not significant. Finally, the morphology played a major role as SS hollow fibres containing a higher volume of sponge-like region were mechanically stronger than the analogous fibres dominated by finger-like and macroporous regions