Research

Rou Jun Toh

Abstract – Optimising of Surface Properties of Additive Components by using an Additive/Subtractive Machine

The Australian Research Council (ARC) Industrial Transformation Training Centre in Surface Engineering for Advanced Materials (SEAM) & their industrial partner, Romar Engineering Pty. Ltd. is investigating how the combination of both additive and subtractive manufacturing in a hybrid

machine can be used to reduce the need for post-processing of additive components. Factors such as quality of surface (i.e. roughness) and residual stress are key considerations.

Initial stages of the project will use the melt pool imaging available on the LASERTEC 65 3D machine and interpret this data with vision algorithms to provide input into machine learning. The machine learning will be used to assess if weld pool parameters can predict final project parameters.

Guang Zeng

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 irons 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 ºC) is a critical technical challenge for 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 process with no phase transitions in Ti/Ta mixture. These unique microstructures of cold sprayed coatings with discrete Ta particles enable large contacting surface area for cell attachment, which is quite distinct compared with 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 were led to better cellular biocompatibility than bare Ti-6Al-4V substrate.

Elias Salloum

Abstract - Optimising Friction Stir Welding and alloy design to ensure the durability of light weight carriages in the rail fleet

The friction stir welding (FSW) is a solid-state welding process which utilises a rotating tool with a pin and shoulder design to create a sound defect free weld by plastic deforming and mixing of the abutting surfaces (fig. 1). Limitation exist when FSW aluminium and its alloys due to thermal cycle activity and shearing resulting in, recrystallisation, grain grow, recovery, and precipitate dissolution, which leads to adversely effects mechanical property in and around the weld that can be seen in a hardness vs. distance from weld centre graph (fig. 2). Addition of grain refinement, recrystallisation retardant, and thermodynamically stable micro-alloying elements, such as scandium and zirconium, has shown to increase hardness and improve joint efficiency but altering the microstructure.

However, their effects is limited materials in the annealed state, hardened aluminium alloys still suffer a loss of mechanical property upon FSW (Fig. 2c). This study will investigate alternative micro-alloying element for possible alternatives for improved mechanical properties of post friction stir welded aluminium alloys. Other means of weld improvement include optimizing of welding parameters to control heat generation and coupling this with micro-alloy optimisation. Cold-working of aluminium and its alloys has shown to increase microhardness by increase dislocation density within the subgrain structure. Micro-alloying coupled with FSW optimization is the focus of this research.

Magdi Morks

Abstract - Properties of titanium cold spray additive components with consideration of post fabrication treatment

Cold spray process is currently used as metal spray technique in which solid powder particles (1–100 μm diameter) are accelerated to speeds above supersonic velocities (~1500 m/s) by a supersonic gas jet. The powder particles undergo significant deformation on impact with the substrate, thereby forming a coating. The quality of the coating depends on the powder and substrate types, as well as the processing parameters, such as the gas pressure and type, gas temperature, standoff distance, and particle velocity. In this project cold spray will be employed as additive manufacturing technique to fabricate complex components from CP titanium and titanium alloy feedstock. A fundamental studies will be performed to investigate the microstructure/mechanical properties relationship.

Different microscopic and analytical techniques such as SEM, TEM, OM, XRD, EDS, and BSED will be used to analyses the microstructure and grain structure. Mechanical tests such as tensile strength, fatigue, fracture toughness, and hardness will be performed. A selection of the components will be heat treated to improve properties including residual stress microstructure and porosity. Treatments will range from low temperature tempers through high temperature anneals and hot isostatic pressing. The changes in properties (local and general) after these treatments will be studied.

Mechanical strength at the joint of components will be studied.

Jiayu Ye

Abstract - In situ visual monitoring of metal powder directed energy deposition for additive manufacturing

Additive manufacturing (AM) has been widely used in aerospace, medical implant and other industry sectors in recent years due to its extraordinary capability of net-shape building of parts with complexgeometries. As a member of the AM category, laser metal deposition (LMD) is a superior technology for repair, coating and refurbishment. Following its name, the mechanism of LMD is that metal powders are heated by a laser beam and become molten, after which they are blown from a nozzle.

The molten metal drops are then directly deposited and solidified onto the surface of the substrate along the laser scanning path, which builds the part layer by layer. However, this technology still faces many challenges despite its inherent advantages. System inputs such as heat input rate and scanning speed are usually set empirically. If they are set inappropriately, defects (e.g. porosity and cracking) will occur and cause failure of the part and material wastage. In recent years, many researchers are focusing on in-situ monitoring of the process signatures (e.g. melt pool temperature and size) to characterise the impacts of the chosen values for the system inputs. But after measuring these signatures, what do they mean for final product qualities? Are there enough signatures to be monitored? This unclear relationship between the process signatures and the final product qualities is the most challenging problem in AM. Therefore, the aims of my research are to (i) determine if there is other process information that relates to product quality, and (ii) build the bridge between the family of process signatures and the final product qualities using a data-driven method.

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 healing process. The project will establish theunderstanding 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 and can bring significant patient benefits. The project will forge new and important collaborations and provide an output for biomedical technology locally and internationally.

Abstract - Next Generation Corrosion Inhibitors for Protection of Galvanised Steel and Cold Rolled Steel

Corrosion has a significant economic impact with losses in the magnitude of billions of USD annually in transportation, manufacturing and infrastructure. In this project, new corrosion inhibitors for galvanised and cold rolled steel are being screened experimentally and quantum chemically described using density functional theory and classical methods. A database is generated for computational model building to identify lead structures for the development of new highly effective inhibitors.

Abstract – Developing Functional Coating Systems for Bio-metal for Orthopaedic Implants

The desirable mechanical properties and superior biocompatibility of magnesium (Mg) and its alloys has placed them in the research frontier in materials for biomedical applications. However, their clinical applications are significantly restricted by the high degradation rate in physiological environment. In order to tackle such a limitation, functional polymeric coating systems will be developed to address rapid degradation as well as to reduce other clinical issues such as wear resistance, infection and low bone-inductivity.

Abstract – Development of a Robotic Electrochemical Testing Facility

Corrosion poses significant challenges to the transportation, manufacturing and infrastructure sectors. For this reason, it is imperative to prevent and control corrosion using corrosion inhibitors. A corrosion inhibitor protects a metal by restricting cathodic or anodic activity on the metal surface. Its exact performance depends on its exact molecular chemistry. Due to this dependence on molecular structure, there are literally tens of thousands of possible inhibitors so high throughput screening methods are required to select the best. In this work, a fully electrochemical robotic system will be developed for the purpose to select and design the best performing corrosion inhibitors. The Robotic facility will carry out more than 100 electrochemical tests per day.  

Kai Rui Wang

Abstract - Expanding the Capabilities of a Semi-Solid Agar Based Test System for Studies into the Microbiologically Influenced Corrosion of Steel Pipes in a Soil Environment

Risks of leakage and contamination are incurred by the corrosion of buried steel water pipelines, which cause health and safety hazards to the communities that potable water is delivered to. As much of the corrosion originates from the outer surface of the pipe, monitoring soil-to-steel interactions is crucial to understanding the physical and chemical mechanisms that cause corrosion. It was found that semi-solid agar could be a good analogue for simulating the physical structure of clay-based soil conditions for corrosion testing; however, a more systematic study needs to be carried out to investigate the metal-bacteria-environment interactions present in microbiologically influenced corrosion (MIC) situations. Detailed studies are currently being performed to analyse such interactions in the 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 for pipelines buried underground.

Chathumini Samarawickrama

Abstract - Study of mechanisms of film forming behaviour of corrosion inhibitors for commercial grade aluminium alloys

In today’s society, corrosion protection of structural aluminium alloys for aerospace, automotive and marine applications, is of paramount importance. This is commonly achieved through the use of corrosion inhibiting compounds. Constraints such as potential 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 carried out on evaluating inhibitor performance and associated mechanisms, limited studies have been done on understanding the film-forming characteristics of inhibitors and their role in providing corrosion protection. Therefore, 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 and the test methods used to evaluate the inhibitor induced films in neutral chloride solution. Film formation was investigated and characterised by means of various electrochemical corrosion testing methods, to include linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS) amongst others and selected surface analysis techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS).

A major focus of this study is to draw correlations from the electrochemical data and surface analysis results in terms of understanding film forming behaviour and in particular, the persistency of the inhibitor-induced film once it has been developed over the metal surface.

Jakeria Mohd. Rafiuddin

Abstract 

Figure 1 shows the polarisation curve of an aluminium 6022 sample in NaCl aqueous solution with and without an organic inhibitor. A lower I_corr value and a shift of the corrosion potential (E_corr) towards more negative direction for the inhibited sample is shown when compared to the uninhibited sample, which indicates the efficiency of corrosion inhibition. Figure 2 represents the scanning electron microscope image of an as-received aluminium alloy 6022 surface before any mechanical treatment such as grinding and polishing. The grey flake-like structures represent the uneven cutting edges of the as-received sample. A cross-sectional SEM image of` the same sample by Focussed Ion Beam (FIB) milling is presented in Figure 3. An aluminium oxide layer (Al₂O₃) has been observed over the as-received sample, and the quantitative analysis from Energy-Dispersive X‑ray Spectroscopy (EDS) spectra (Figure 4) reveals that the principal elements present over the alloy surface are Al, Mg, Si, and O.

Qiushi Deng

Abstract 

Great momentum has been gained in the development of corrosion inhibitor technologies to mitigate corrosion of metallic materials, in particular for zinc and galvanised steel. Corrosion inhibitors are for instance crucial to ensure, i.e. integrity, durability and safety. The use of metallic salts as corrosion inhibitors was broadly explored since the early stage owning to their ability to passivate the metal surface and generate protective films.

However, the increasing environmental concern and the pursuit of more cost-efficient techniques shifted the focus toward organic alternatives due to many advantages exhibited by such organic compounds such as, i) cost effectiveness, ii) pronounced inhibiting effect, and iii) flexibility to different applications with non-toxic nature. Unfortunately, challenges have been encountered in the context that the candidate molecules acting as effective corrosion inhibitors are rich in diversity of chemistry and structural complexity.

In addition, the inhibition behaviour is not only related to the particular molecular configurations but also depends on the existing form of molecules (i.e. de/protonation) and the surface condition of the metal (i.e. surface charge and the presence of oxides). Given such, this project aims to design a sound strategy to explore the feasible organic inhibitors from a large variety of molecular candidature, in an attempt to reveal the inhibition mechanism from the viewpoint of inhibitor structural change, molecular evolution, and the metal charge at the interface.

The expected findings of this project will develop a further understanding of the protection mechanism of organic inhibitors from a molecular viewpoint and will form a concrete basis to design and prepare new inhibitor molecules for engineering relevance.

Milan Patel

Abstract

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 & 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 dayalan.gunasegaram@csiro.au.

Omid Bafkar

Abstract - Study on the Airflow Phenomena on the Human Respiratory System

Obstructive Sleep Apnoea (OSA) is a common disorder, and continuous positive airway pressure (CPAP) is usually the therapy of choice. CPAP is known to have problems with adherence with many patients eventually abandoning the device. However, the development of an optimal OSA treatment for a specific patient requires a thorough understanding of the responses of the patient to the tailored OSA treatments which in turn need numerously costly clinical trials and measurements.

Therefore, accurate predictions of the responses of the patient to the tailored OSA treatments are highly desired. We implement numerical modelling methods and techniques to understand airflow behaviour in various sleeping positions and conditions.

This aims to provide a technique that can help specialists provide better treatment solutions to their patients. 

Adam Truskewycz

Abstract

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 metal concentrations which are unidentified due to the extensive cost associated with site sampling and expensive analytical measurements requiring trained scientific staff. On site detection of heavy metal contamination which is user friendly, cheap and rapid is therefore sought after to map out areas 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 for detecting low concentrations of pollutants (including heavy metals). This approach for pollution detection relies on a nanomaterial support which has fluorescent chemical functional groups attached to it which selectively bind the pollutant of interest. Upon binding, the fluorescence profile of the composite changes and can be measured. The concentration of heavy metal can be accurately associated with the amount of fluorescence output and heavy metal concentrations can be quantitatively determined. 

Bin Qian

Abstract - Development of coumarins and their composites as optical sensors for Cu²⁺ as contaminants in water and soil

Copper contamination in soil and water is a major concern due to its direct impact on human health when present in excessive/inadequate amounts^[1,2] and form complexes with ligand, such as protein, molecules, enzymes, which possess electron rich centres to donate electrons, such as N, O, P and S. Thus, the development of rapid and reliable sensing methods that are selective and sensitive to metals ions of interest, and that can be utilized in aqueous media is essential in allowing for rapid and readily available management of both nutrient- and contaminant-levels. By inviting molecular design and materials engineering, a series of fluorescent coumarin derivatives were designed, synthesized, and evaluated for their Cu²⁺ sensing performance in aqueous media to gain fundamental understanding of the structural requirements towards such molecular probes (Figure 1) using NMR, IR and MS, single crystal X-ray study of the probes and their Cu²⁺ complexes resulted in the insight understanding of the essential heteroatom ratio and configuration, and the optimum relative distances among the molecular moieties, rigidity of the structure and electron density with selective sensing^[1].

Meanwhile, aimed at the improvement of sensitivity and water solubility of previously developed Cu2+-selective coumarin probes, SiO2-coumarin nanohybrid was formulated via electrostatic attraction with negatively charged SiO2 nanoparticles (SiO2 NPs) and the selected coumarin in aqueous media at certain pH value. This material possessed the identical Cu2+ selectivity of the coumarin with lowered limit of detection and an extended linear detection range. The coumarin nanohybrids were also applied to determine Cu2+ concentration in aqueous soil extracts with >94 % recovery rates when compared to standard soil analysis method - inductively coupled plasma-mass spectrometry (ICP-MS).

References:

[1] Clemens, S.; Ma, J. F., Annual review of plant biology 2016, 67, 489-512.

[2] Giripunje, M. D.;  Fulke, A. B.; Meshram, P. U. Clean-Soil, Air, Water 2015, 43 (9), 1350-1354.

[3] Qian, B.; Váradi, L.; Trinchi, A.; Reichman, S.; Bao, L.; Lan, M.; Wei, G.; Cole, I. S.. Molecules 2019, 24 (19), 3569.

Sabrina Beker

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 material 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 any adverse environmental impacts.

Jiajia Zhao

Abstract - Novel photocatalysts for CO 2 hydrogenation to chemical fuels

Photocatalytic CO 2 reduction, driven by solar energy, is a renewable reaction to convert atmospheric CO 2 into chemical fuels. Semiconductors are commonly used as photocatalysts, however poor selectivity and low- efficiency for light absorption still restrict large-scale production. Therefore, it’s critical to control the structure properties of photocatalysts and investigate reaction mechanisms for improving product selectivity. This project aims to develop novel SnO 2 -based nanostructures for improved photocatalytic performance of CO 2 hydrogenation. A library of catalysts will be synthesised and characterized using high-throughput methods.

Synchrotron X-ray diffraction will be used to analyse crystal structures, and neutron diffraction will be used to determine oxygen defect concentration. The success of this project can lead to opportunities for solar-driven carbon-neutral fuels production. Consequently, developing nanostructures of photocatalysts may be a sustainable approach to decrease fossil fuels usage and CO 2 emissions.