Computational Fluid Dynamics (CFD), Fluid-Structure Interaction (FSI), 3D Printing (Stereolithography, PolyJet), Selective Laser Melting, Modelling Process, Direct Laser Metal Deposition, Fused Deposition Modelling, Object printing
Abstract - Novel fast manufacturing approaches for biocompatible Ti-Ta structures
Titanium (Ti) and its alloys are widely used as load-bearing implants. However, slow but continuing release of toxic metal ions and wear debris may incur undesirable side effects. Tantalum (Ta), an emerging metallic biomaterial, exhibits high corrosion and wear resistance in vivo, but the extremely high melting temperature of Ta (3017°C) is a critical technical challenge to manufacturing fully dense structures through conventional processing approaches. As such, new and feasible manufacturing techniques for Ta-based implant materials are highly desired. Cold spray, a new additive manufacturing technology, provides a promising solution to depositing metallic coatings on Ti implants with a variety of benefits, including low-temperature and solid-state processing with no phase transitions in the Ti/Ta mixture. These unique microstructures of cold sprayed coatings with discrete Ta particles enable large contact surface area for cell attachment, which is distinct from bulk Ti-Ta alloys. In this study, uniform and dense Ti-Ta composite coatings (pure Ta and Ti+30 wt.% Ta) were developed on Ti-based substrates (Ti-6Al-4V) using cold spray. The unique microstructures of cold sprayed coatings led to better cellular biocompatibility than bare Ti-6Al-4V substrate.
Figure 1. A commercial impact system by Impact Innovations
Abstract - Optimising Friction Stir Welding and alloy design to ensure the durability of light weight carriages in the rail fleet
Friction stir welding (FSW) is a solid-state welding process that uses a rotating tool with a pin-and-shoulder design to create a sound, defect-free weld by plastic deformation and mixing of the abutting surfaces (Figure 1). Limitations exist for FSW aluminium and its alloys due to thermal cycle activity and shearing resulting in recrystallisation, grain growth, recovery, and precipitate dissolution, which promote adverse effects on mechanical properties in and around the weld. These can be seen in a plot of hardness vs. distance from weld centre (Figure 2). Addition of grain refiners, recrystallisation retardants, and thermodynamically stable micro-alloying elements such as scandium and zirconium have been shown to increase hardness and improve joint efficiency. However, these also alter the alloy’s microstructure, which generally affects materials in the annealed state. However, hardened aluminium alloys still suffer a loss of mechanical properties upon FSW (Figure 2c). This study will investigate alternative micro-alloying elements for improved mechanical properties of post-friction stir welded aluminium alloys. Other means of weld improvement include optimizing welding parameters to control heat generation and coupling this with micro-alloy optimisation. Cold-working of aluminium and its alloys has also been shown to increase microhardness by increasing dislocation density within the sub-grain structure. Micro-alloying coupled with FSW optimization is the focus of this research.
Figure 1. FSW process (The, Goddin and Whitaker, 2011)
Abstract - Properties of titanium cold spray additive components with consideration of post fabrication treatment
The cold spray process is currently involves accelerating solid powder particles (1–100 mm diameter) to supersonic speeds (~1500 m/s) using a supersonic gas jet. The particles undergo significant deformation upon impact with the substrate, thereby forming a coating. The quality of the coating depends upon the powder and substrate types and the process parameters, such as the gas pressure and type, gas temperature, standoff distance, and particle velocity. In this project, cold spray will be employed as an additive manufacturing technique to fabricate complex components from commercially pure (CP) titanium and titanium alloy feedstock. A fundamental study to investigate the microstructure/mechanical properties relationship will be undertaken. Different microscopic and analytical techniques, such as SEM, TEM, OM, XRD, EDS, and BSED, will be used to analyse the microstructure. Mechanical tests will be conducted to measure tensile strength, fatigue behaviour, fracture toughness, and hardness. Some components will be heat treated to improve properties including residual stress microstructure and porosity. Treatments will range from low-temperature tempers through to high-temperature anneals and hot isostatic pressing. The changes in the properties, both local and general, after these treatments will be studied. Mechanical strength at the joint of components will also be studied.
Figure 1. Cold spray-coated samples
Abstract - Multifunctional coatings for biomedical Mg alloys
Magnesium (Mg) and its alloys are emerging materials for biomedical applications, owing to their desirable mechanical and biological properties. However, their clinical applications are significantly restricted by the rapid and uncontrollable degradation progress, which generates hydrogen gas, deteriorates mechanical strength, and drives dramatic changes in local pH in chloride-rich physiological environments. A comprehensive understanding of biocompatibility is essential for design and employment of biomedical Mg implants. In particular, implant-related infections caused by pathogen colonies and implant degradation products must be prevented. Existing research focuses either on the corrosion or pathogenic issues of Mg-based implants. It is a pressing requirement to discover a feasible solution to these two key issues simultaneously. This project aims to develop a series of gallium (Ga) based multifunctional coatings, which not only suppress the initial degradation but also reduce the risk of implant-associated infections through sustainable release of antibacterial agents from the coating. Though Ga is a recognised broad-spectrum antibacterial element, its use as coating materials for Mg alloys has yet to be assessed. In this study, protective coatings containing Ga ions as an antimicrobial agent will be prepared via a cost-effective technique. Physical, chemical, electrochemical and antibacterial features will be characterised by SEM-EDX, FIB-TEM, XRD, XPS, potentiodynamic polarisation curves, EIS, and in vitro cell and bacterial cultures. It is anticipated that such a new series of coatings will generate new possibilities for clinical application of biodegradable Mg alloys.
Figure 1. Multifunctional Ga based coatings with MAO and RF sputtering process
Abstract - In situ visual monitoring of metal powder directed energy deposition for additive manufacturing
Additive manufacturing has developed rapidly due to its extraordinary advantages when building parts with complex shapes, and for almost 100% use ratio of raw materials, particularly in terms of powder directed energy deposition (DED). It can also be used for surface repair and coating. However, almost all industrial AM machines are open-looped and underequipped with sensors. Input parameters are always set at the beginning of the build process and are not adjustable. It is difficult to keep the path uniform during building without feedback control. Once the defect or non-uniformity occurs in one tracking path, it will then be overlaid due to the layer-wise manufacturing processing. Therefore, it is necessary to monitor the build process, i.e. the shape and temperature of the melt pool, in real time. The aim of my project is to develop a feedback system to maintain the uniformity of each track during building. The first and the most important step towards my aim is to build an effective monitoring system to measure the width, height, and temperature of the melt pool as accurately as possible. Secondly, experiments will be conducted to determine the influence of input parameters on the process parameters as well as the finished part quality. Then the feedback control system can be built. Finally, the validation experiments will be performed, and the uniformity of the finished part geometry will be predicted.
Abstract - Expanding the capabilities of a semi-solid agar-based test system for studies of the microbiologically influenced corrosion of steel pipes in a soil environment
Corrosion of buried steel water pipelines risks leakage and contamination, which cause health and safety hazards to the communities that the potable water is delivered to. As much of the corrosion originates from the outer surface of the pipe, monitoring soil-steel interactions is crucial to understanding the physical and chemical mechanisms that cause corrosion. Semi-solid agar may be an appropriate analogue for the physical structure of clay-based soil for corrosion testing. However, a more systematic study must be carried out to investigate the metal-bacteria-environment interactions present during microbiologically influenced corrosion (MIC). Currently, detailed studies are being performed to analyse such interactions in a novel semi-solid agar system. The system as an analogue of soil, if validated, would allow significant advancements to laboratory-based research of corrosion in a soil environment, thus allowing the scientific community to better combat MIC of pipelines buried underground.
SEM image of HA1 steel, post corrosion in semi-solid agar medium
Abstract - Novel photocatalysts for CO2 hydrogenation to chemical fuels
Photocatalytic CO2 reduction, driven by solar energy, is a renewable reaction to convert atmospheric CO2 into chemical fuels. Semiconductors are commonly used as photocatalysts. However, poor selectivity and low efficiency of light absorption yet restrict large-scale production. Therefore, it is critical to control the structural properties of photocatalysts and investigate reaction mechanisms for improving selectivity. This project aims to develop novel SnO2-based nanostructures for improved photocatalytic performance of CO2 hydrogenation. A library of catalysts will be synthesised and characterised using high-throughput methods. Synchrotron X-ray diffraction will be used to analyse the crystal structures, and neutron diffraction will be used to determine the concentration of oxygen defects. The success of this project will lead to opportunities for solar-driven, carbon-neutral fuel production. Consequently, developing nanostructures of photocatalysts may be a sustainable approach to decrease fossil fuel usage and CO2 emissions.
Figure 1 (a) The illustration of photocatalytic CO2 reduction; (b) High-throughput photocatalytic reactor
Abstract - Development of nanomaterials as optical sensors for copper contaminants in soil
Heavy metal species are non-biodegradable, potentially toxic molecules. Due to the health hazards and environmental damage heavy metals can cause, this means that detection, monitoring and ultimately remediation of heavy metals now attract significant attention. Optical sensing methods have been developed for the sensing of heavy metals, which are facilitated by small organic molecular sensors or nanomaterials. These sensors permit the detection of trace amounts of analytes within relatively small samples. The aim of our project is, firstly, to develop and assess a range of small organic molecules for their Cu2+ sensing performance in aqueous soil-extracting solution. This is to understand the structural requirements of sensing molecules, and to therefore achieve optimal selectivity and sensitivity. These results can then be applied to sensing of other metal ions. The potential use of non-toxic nanoparticles, such as quantum dots (QDs) and SiO2 nanoparticles, for the optical sensing of Cu2+ will be evaluated to enhance sensor sensitivity and stability due to the large specific surface area available. These materials, due to their unique photophysical properties and versatile surface chemistry, offer the possibility for encapsulation or surface attachment of optimised functional materials. By combining the small organic molecular sensors and the nanoparticles for the sensing of Cu2+, composite materials with improved sensing performance towards Cu2+ will be identified. Finally, the goal is to integrate sensing materials on a platform (polymer, hydrogel or glass) with possible deployment to the site of the sample with minimal sample preparation required. In particular, the soil extracting solution would be prepared on site.
Abstract - Study of mechanisms of film-forming behaviour of corrosion inhibitors for commercial grade aluminium alloys
Corrosion protection of structural aluminium alloys for aerospace, automotive and marine applications is now of paramount importance. This is commonly achieved via corrosion-inhibiting compounds. Constraints, such as health issues associated with exposure to conventional chromate-based corrosion inhibitors, has led to the development of low-toxicity corrosion inhibitors for a wide range of industries. Although numerous studies have been conducted to evaluate inhibitor performance and associated mechanisms, limited studies have been performed to understand the film-forming characteristics of inhibitors and their role in providing corrosion protection. This study presents key aspects of the film-forming behaviour of selected inhibitors that are known for their high corrosion inhibition efficiency for the protection of aluminium AA2024‑T3 alloy. The test methods used to evaluate the inhibitor-induced films in neutral chloride solution will also be assessed. Film formation will be investigated and characterised by means of various electrochemical corrosion test methods. These will include linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS), amongst others, as well as surface analysis techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). A major focus of this study is to draw correlations between the electrochemical data and surface analyses’ results to understand film forming behaviour, and in particular, the persistency of the inhibitor-induced film after it develops on the metal surface.
Abstract - Next generation corrosion inhibitors for protection of galvanised steel and cold rolled steel
Corrosion has a significant economic impact with annual losses running into billions of USD for the transportation, manufacturing and infrastructure sectors. In this project, new corrosion inhibitors for galvanised and cold-rolled steel are experimentally screened and quantum chemically described using density functional theory and classical methods. A database is being generated for computational model building to identify leading structures for the development of new, highly effective inhibitors.
Abstract - Multiscale modelling of SLM additive manufacturing – melt pool & microstructure
RMIT is participating in a CSIRO-NTU Singapore-led project to develop cutting-edge simulation models of additive manufacturing, specifically the Selective Laser Melting process. This project will combine high-definition continuum fluid dynamics at the part scale, which models powder melting & melt pool tracking, with phase-field modelling at the grain scale that predicts solidification rate and finished-part microstructure. ‘Live’, bidirectional data exchange between these two sub-models permits the most accurate predictions of both the behaviour of the SLM process and the microstructure of the finished part to be obtained from one simulation platform.
All coding is performed using open source platforms, allowing for rapid technology transfer to industry partners. Enquiries should be addressed to firstname.lastname@example.org.
Abstract - Study of airflow phenomena in the human respiratory system
Obstructive Sleep Apnoea (OSA) is a common disorder, which frequently leads to unpleasant side effects such as snoring. Continuous positive airway pressure (CPAP) is usually the therapy of choice but has problems with adherence with many patients eventually abandoning their therapeutic devices. The development of an optimal OSA treatment for a patient requires an understanding of the patient’s responses to tailored OSA treatments, which in turn requires costly clinical trials and numerous measurements. Therefore, accurate prediction of patient response to tailored OSA treatments are desired. We implement numerical modelling methods to understand airflow behaviour for various sleeping positions and conditions. This will help specialists provide better treatment solutions to their patients.
Figure 1. Airflow behaviour on the nasal cavities during the short inhalation.
Abstract - Nanoparticle synthesis using phytochemical precursors – instilling beneficial properties using green methodologies for pollution remediation
Release of heavy metals into the environment from industrial processes results in severe adverse social, environmental and human health problems. Many terrestrial and aquatic ecosystems contain persistent and undetected heavy metals at unidentified concentrations due to the extensive cost associated with site sampling and expensive analytical measurements requiring trained scientific staff. On-site detection of heavy metals that is user friendly, cheap and rapid is therefore sought to map regions of concern and provide communities with information relating to the toxicity and suitability of their land and water resources for agricultural, potable and recreational use. Nano-sensing of environmental pollutants is an emerging field of research possessing outstanding capacity to detect low concentrations of pollutants including heavy metals. This approach to pollution detection relies on a nanomaterial support that has fluorescent chemical functional groups attached to it that selectively bind the pollutant of interest. Upon binding, the changes to the fluorescence profile of the composite can be measured. The concentration of a heavy metal can be accurately associated with the amount of fluorescence output.
Abstract - Functional strontium phosphate-coated magnesium alloys for orthopaedic use
This project aims to develop a functional strontium (Sr)-release surface upon magnesium-based orthopaedic implants, to suppress the rapid degradation rate of Mg, facilitate new bone formation and ultimately shorten the healing process. The project will establish understanding of the formation mechanisms of Sr-releasing coatings, and determine the critical release rate of Sr to activate bone cell responses. The project is significant for the development of practical, bone-favourable and degradation-inhibiting surfaces for magnesium implants, which are in demand due to their significant patient benefits. The project will forge major new collaborations and provide an output for biomedical technology both locally and globally.
Abstract - Green synthesis of carbon dots from natural resources as potential candidates for nanobioremediation of emerging pollutants
A wide range of new & emerging pollutants (EPs) have been released into water bodies, mainly by human activities. Many of these EPs have been shown to be deleterious to the environment, with some threatening the aquatic ecosystem. Significant research & development is underway to develop new remediation technologies aimed at alleviating the environmental issues associated with Eps. However, the complete removal and efficient treatment of aquatic contaminants remains a huge challenge for water resource management. Advanced nanotechnology provides a promising alternative for increasing water treatment efficiency, especially carbon dots (CDs). CDs, which are fluorescent nanostructures in the size range of 2-10 nm, have attracted significant attention for their excellent physicochemical properties, low toxicity, chemical inertness, tunable fluorescence, good water solubility, and potential applications in several fields of science and technology, particularly with respect to the environment. Recently, the conversion of natural resources into carbon-based dots has attracted major attention due to the environmental sustainability of the associated simple, economical, and green synthesis. Therefore, this research aims to synthesise CDs from green materials and test them for their degradation of EPs in water. In particular, their ability to degrade industrial dyes and per- and poly-fluoroalkyl substances (PFAS) will be tested using the nanobioremediation technique developed in this study. In order to conduct a proper evaluation of the proposed nanobioremediation, an assessment of the impact of the CQDs on freshwater microbial community structure and the ecotoxicity of the CQDs will be conducted to minimise adverse environmental impacts.
Figure 2: Studies on dye degradation using CDs made of Prickly Pear extract