Researcher: Fátima Zorro (IST, Lisboa)

Supervisor: Prof. Paulo Ferreira (INL, Braga)
Co – supervisor:Dr. Enrique Carbó-Argibay (INL, Braga)

Funding FCT

As the demand for developing environmentally friendly and energy efficient technologies increases, it is critical to devise processes to produce materials that match those requirements at lower costs. In this context, flash sintering (FS) can become a viable substitution to conventional sintering, leading to a reduction of the processing time from days/hours to minutes/seconds, while significantly decreasing the operation temperatures, particularly in the case of ceramic materials. Among the candidate materials suitable for flash-sintering, this project focus on yttria stabilized zirconia (YSZ), which is widely used for energy devices, such as fuel cells. More specifically, this project proposes to investigate films of YSZ by in-situ transmission electron microscopy (TEM) to simulate in real-time the flash sintering process. Under these conditions, YSZ will be subjected to different electric fields and processing temperatures inside the TEM, to fundamental, understand the kinetic and thermodynamic mechanisms that govern the flash sintering process.

To develop a fundamental understanding of the flash-sintering process, there are still various issues that are currently unanswered, in particular:

• What are the local driving forces for FS?
• What are the diffusion mechanisms involved in the process?
• What is the impact of Frenkel pairs in FS?
• What is the effect of specimen scale on the FS process?

Researcher: Rafael Ferreira (IST, Lisboa)

Supervisor: Prof. Paulo Ferreira (INL, Braga)
Co – supervisor: Dr. Sebastian Calderon

Two-dimensional (2D) materials hold much promise for the next generation of electronic devices, even for such exotic applications like quantum computing. However, the extremely complex construction and the potentially large impact of defects present in the constituent layers are challenges that must be faced to make envisioned technologies into commercially viable options.

The state of current production methods then presents a considerable obstacle to the development of 2D material-based technologies, as defects are inevitably introduced during the synthesis and transfer processes, and the production of large-area crystals is still challenging. On the other hand, some defects may give rise to effects that can be useful for certain applications and so the formation of these must be controlled. Consequently, investigating the formation and influence of defects is a critical facet of 2D materials research.

To answer these challenges, aberration‑corrected scanning transmission electron microscopy (STEM) can provide sub-angstrom spatial resolution [1] to locate and identify substitutional defects in 2D materials [2], while atomic-level characterisation of the electronic structure is made possible by employing electron energy‑loss spectroscopy (EELS) [3-5]. Yet, the functional properties of any material are fundamentally determined by the electromagnetic fields and the associated distribution of atomic charges within the structure. A direct measurement of these features would therefore grant a fundamental understanding on how localised deformations caused by defects impact material systems as a whole.

The ability to probe the charge density is therefore highly desired. In this regard, differential phase contrast (DPC) imaging [6,7], an electron microscopy technique going through a rapid development, is sensitive to the intrinsic electromagnetic fields of a sample and can make use of the atomic resolution of STEM. Additionally, for non-magnetic, weakly scattering specimens such as many 2D materials, DPC can be directly related to the projected electric field, establishing these structures as the ideal objects of study.

Thus, this work will implement the capabilities of DPC to examine the atomic charge distributions and defect-induced redistributions in 2D materials that hold potential for quantum electronics, as well as structures and devices in which they are used. This investigation will be complemented by inspection of the electronic transport properties with in‑situ STEM-DPC observations, where a bias can be applied to the specimen while changes in conductive behaviour are monitored in real time.

References

• Sawada, H., et al. Resolving 45-pm-separated Si-Si atomic columns with aberration‑corrected STEM. Microscopy 64, 213−217 (2015).
• Krivanek, O. L., et al. Atom-by-atom structural and chemical analysis by annular dark-field electron microscopy. Nature 464, 571–574 (2010).
• Zhou, W., et al. Direct determination of the chemical bonding of individual impurities in graphene. Rev. Lett. 109, 206803 (2012).
• Ramasse, Q. M., et al. Probing the bonding and electronic structure of single atom dopants in graphene with electron energy loss spectroscopy. Lett. 13, 4989–4995 (2013).
• Suenaga, K. & Koshino, M. Atom-by-atom spectroscopy at graphene edge. Nature 468, 1088–1090 (2010).
• Dekkers, N. H. & de Lang, H. Differential phase contrast in a STEM. Optik 41, 452−456 (1974).
• Shibata, N., et al. Direct Visualization of Local Electromagnetic Field Structures by Scanning Transmission Electron Microscopy. Chem. Res. 50, 1502−1512 (2017).

Researcher: Francisco Figueiredo (Univ. of Porto)
Supervisors: Prof. Sandra Ribeiro (Univ. of Porto) and Prof. Paulo Ferreira (INL, Braga)

Funding: Portuguese Foundation for Science (FCT), PhD fellowship

Structural analysis of Ataxin-3 aggregation pathway. SDS-resistant elongated mature fibrils form by pathogenic Ataxin-3 visualized by Transmission Electron Microscopy. Cartoon representation of Ataxin-3 globular Josephin Domain (JD) involved in the first Atx3 aggregation step. JD aggregation prone region highlighted in red

Ataxin-3 (Atx3) is one of nine proteins containing an expandable polyglutamine (polyQ) repeat segment that are associated with late-onset human neurodegenerative diseases. Aggregation of the non-pathological and polyQ-expanded Atx3 is well characterized and is critically dependent on early self-assembly events modulated by its globular Josephin domain. PolyQ expansion beyond a certain threshold elicits a second (polyQ-dependent) aggregation step that is critical to mature fibril generation. Biophysical studies unveiled the Atx3 multistep aggregation pathway, but structural data on the nature of the intermediates formed is still lacking. To uncover the structural aspects of Atx3 aggregation intermediates, advanced electron microscopy and optical microscopy approaches will be used.

Researcher: Ricardo Sousa (Univ. of Porto)
Supervisors: Prof. Laura Ribeiro (Univ. of Porto) and Prof. Paulo Ferreira (INL, Braga)

Funding: Ferespe, Fundição de Ferro e Aço Lda

Cast duplex stainless steels (DSS) have been applied in highly corrosive conditions, such as marine environments (oil and gas), chemical and petrochemical industry, as well as pulp and paper industry. The superior performance of these material is achieved by a balanced microstructure, consisting of approximately equal amounts of ferrite (α) and austenite (γ) in the as-heat treated condition. In terms of mechanical properties, the balanced microstructure is beneficial to obtain high toughness and high strength, when compared to austenitic stainless steels with same corrosion resistance.

In the most severe applications, DSS grades with high Cr, Ni, Mo and N are required, to ensure the best performance in terms of pitting, stress and inter-crystalline corrosion. Among these DSS, the so-called super (SDSS) and hyper grades (HDSS) contain even higher Cr and N contents, when compared with other DSS grades. As a consequence, these grades are prone to the formation of detrimental secondary phases, in particular sigma (σ) and chi (χ). The destabilization of duplex microstructure is more pronounced on thick areas of casting components. The primary objective of this project is to characterize among several different secondary phases that may form during casting of large DSS components and to establish kinetic models for their formation, by means of correlate the information collected on optical microscopy, as well the scanning and transmission electron microscopy techniques.

BSE-SEM image of DSS containing α, γ, χ- and σ-phases, ascending ordered by brightness levels. On right side, the distribution of principal thermal residual stresses. The maximum stresses are concentrated on interfaces between α (lower coefficient of thermal expansion) and the γ, χ- and σ-phases areas.

Currently, a methodology to identify χ- from σ-phases has been presented, which allow us to measure their volume percent. Therefore, volume percent measurements are critical data to establish the kinetic models of each phase, to tailor the appropriate cooling cycle. The methodology is based on matching between different the grey levels of χ- from σ-phases on BSE-SEM images with semi-quantitative chemical analysis with aid of EDS. Therefore, the semi-quantitative analysis on SEM are compared with measurements by means of TEM-EDS. In fact, TEM plays a key role on characterization methodology, due to electron diffraction capability in order to unequivocally identify χ- and σ-phases. Finally, as the identification is complete, an image segmentation procedure can be applied to BSE-SEM images.

Apart from the kinetics description of secondary phases formation, being able to detect and identify all the phases that may be present on DSS castings allows us to study how their distribution can affect the magnitude and gradient of thermal residual stresses. A finite element method has been used, where BSE-SEM images are inputs and it is possible to assign the elastic properties (Young’s modulus and Poisson’s ration) and coefficient of thermal expansion to individual phases. The application of a thermal gradient, the software calculates maps of distribution of principle stresses. In fact, due to significant differences in terms of coefficient of thermal expansion, thermal residual stresses arise and interfaces acts as concentration areas of stresses.

Researcher: Postdoc (to be hired)
Supervisors: Prof. Paulo Ferreira

Partners: INL, GALP, FEUP, FCT-NOVA
Funding: PT – 2020

The valorisation of natural gas through Gas-to-Liquids technology plays an essential role in the transport industry. This project combines catalyst development and reactor design to efficiently produce synthetic fuels of superior quality using a continuous Fischer-Tropsch process.

Researcher: Dr. Alec LaGrow
Supervisors: Dr. Andrea Capasso (INL) and Prof. Paulo Ferreira (INL)

Partners: INL, Graphnest, University of Minho, UT-Austin
Funding: PT – 2020

Electromagnetic interference (EMI) is an interesting phenomenon that affects all electronic devices working in an environment surrounded by external sources of radiated signals and electromagnetic radiation, such as antennas and other electronic devices. Within the context of electromagnetic compatibility, EMI is considered a potential and major source of operating problems to electronic devices and a cause of the performance and lifetime reduction, especially in a world where electronic devices are increasingly ubiquitous. In this context, current shielding materials used to protect electronic devices from EMI are based on heavy, brittle, and expensive metals. At the same time, the major EMI applications have a huge demand for flexible, additive, light, and inexpensive materials. This is of crucial importance, for instance, for several vehicles industries, from hybrid and electrical cars to airplanes, where weight reduction is imperative to increase autonomy and reduce carbon footprint. Graphene and related materials are considered the most promising and effective candidates for effective EMI shielding because of their excellent electrical properties, extremely high specific surface area, and unprecedented strength to weight ratio. The GEMIS project aims to develop versatile EMI shielding solutions based on graphene materials and technology and make a significant impact in several applications and sectors that require highly versatile shielding solutions able to comply with various production processes. To achieve this, the project proposes developing a universal formulation for a liquid dispersion of graphene materials with highly effective EMI shielding and the consequent production of two EMI shielding composites based on polymers and epoxies. Finally, custom-made equipment will be designed and fabricated to specifically apply the developed EMI shielding solutions on electric wires in the automotive industry.

Researcher: Dr. Cristiana Alves
Supervisors: Sandra Carvalho (University of Coimbra) and Paulo Ferreira (INL)

Partners: University of Minho, DENTAL VERDE – CLÍNICA MÉDICA E DENTÁRIA, LDA
Funding: PT – 2020

The project will develop a new concept of dental implants. A novel surface with graded functional treatments will give a solution for the main problems of dental implants used nowadays: poor bioactivity that delays osseointegration, and periimplantitis, an inflammatory disease due to bacterial infection. The strategy to achieve this novel design will be accomplished through the development of a bioactive surface based on the synergetic effect of anodic tantalum oxide with multilevel porosity (nano to micro), as well as the development of an antimicrobial delivery system based on Ag or ZnO nanoparticles deposited by magnetron sputtering onto the anodic tantalum oxide (micro+nano) structured surface.

Researcher: Ricardo Sousa
Supervisors: Laura Ribeiro (University of Porto) and Paulo Ferreira (INL)

Partners: INL, INEGI, FEUP
Funding: PT – 2020

In this project a multiscale study of multiphase stainless steels will be addressed. These advanced materials belong to the new generation of steels with increasing applications due to their high strength, toughness, and corrosion properties. Their applications and potential are wide as they can be processed in many different ways ranging from casting to bulk and sheet metal forming. The microstructure of these steels, which is complex and depend on the alloying and thermal processing, affects their behaviour during the processing stages and eventually during their final application. How does the microstructure affects the final properties, how it affects ductility, how it affects damage and fracture mechanisms during processing are the subjects to be researched. The team from INEGI has a strong experience on material modelling of large deformations on metal forming applications. Its expertise ranges from numerical and material constitutive modelling and experimental development. The team from the Department of Metallurgy and Materials of FEUP has a strong experience on processing and microstructural and mechanical characterization of metallic and intermetallic materials, including nanomaterials. This expertise is complemented by the relevant expertise of INL team in advanced TEM for investigations at the atomic scale of nanomaterials. Their common interest and competence on material constitutive behaviour are focused on two approaches at three different scales, nano, micro and macro. The project will bring together the various competences by building a coupled multiscale model, anchored on a robust numerical model and thorough experimental studies on microstructures.

Researcher: Dr. Rúben Santos and Bruno Oliveira
Supervisors: Manuel Vieira (University of Porto) and Paulo Ferreira (INL)

Partners: INL, FEUP
Funding: PT – 2020

The ongoing miniaturization of integrated circuits (IC) and the small dimensions of IC components present significant challenges in terms of performance and reliability. In more advanced IC, such as the 14 nm node technology, the nanoscale of interconnects raises problems that are scale dependent, such as dewetting of thin films during production or electromigration during normal use. In addition, the current processing methodologies employed by the semiconductor industry face considerable challenges during the annealing stage, due to the detachment of the deposited copper layers. Miniaturization also requires that the thickness of the diffusion barrier be scaled down accordingly. This thinning imposes the substitution of the Ta/TaN barrier commonly used to inhibit copper diffusion into the dielectric. In this project, we propose to study the factors involved in dewetting and electromigration phenomena of thin copper films deposited over different substrates (which simulate the diffusion barrier layers), and evaluate the mechanisms which trigger the formation of defects by varying the processing parameters. The deposition conditions, the substrate composition and the copper film thickness are three factors that will be considered in this study. These factors have a strong influence on grain size, twin density and texture, thus conditioning the response of the copper film. Copper films will be deposited in substrate materials simulating the most common diffusion barrier, Ta/TaN films, and also in advanced diffusion barriers, namely, CoW, RuW and RuMn. Structural characterization of the films will be performed by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, electron energy-loss spectroscopy and electron back-scattered diffraction. In situ observations will also be carried out in both scanning and transmission electron microscopies. Developing interconnects with great electrical conductivity remains the main objective of the microelectronic industry. Thus, electrical tests will be conducted on the materials that mitigate dewetting and electromigration after the annealing treatments. The development of this project will produce advances in understanding how thin copper films behave under different thermal and electrical responses, and how the substrate-film interfaces react to the various dewetting stages.

Researcher: Dr. Saha Sabyasachi
Supervisors: Leonard Francis (INL) and Paulo Ferreira (INL)

Partners: INL, University of Aveiro, University Nova de Lisboa
Funding: PT – 2020

Piezoelectrics as Potassium-Sodium-Niobate (KNN) have currently an emerging importance due to its lead-free nature and wide range of high-tech applications as sensors, actuators, energy harvesters, biosensors, etc. However, monophasic dense KNN products are yet difficult to obtain. This project proposes a new method to densify materials abruptly above a threshold condition using FLASH sintering, where the transition occurs by a combination of furnace temperature and electrical field directly applied to the specimen. There are several proposed mechanisms for FLASH: Joule heating is the most reported one, but a defect avalanche in the form of precipitated Frenkel pairs which ionize into charge neutral defects and electron-hole pairs, is being defended as well. Defects enhance diffusion while electron-hole pairs induce high conductivity and photoemission. A clear understanding of the phenomena does not exist yet. The present work aims to exploit FLASH for sintering KNN in different dimensionalities (bulk, films, nanoparticles) and study the science behind FLASH sintering with the following objectives: (i) To investigate the dependence of FLASH on the KNN dimensionality; (ii) To identify the densification mechanisms involved in FLASH sintering of KNN and to overcome possible deleterious effects of the presence of electrical fields; (iii) To contribute to the development of alternative sintering techniques for functional oxides aiming to decrease the thermal budget, ultimately towards room temperature processing (iv) To prove the concept for low temperature sintering of bidimensional KNN (thin films on flexible substrates), not yet explored by FLASH, and extend it to other lead free oxides.

Researcher: Dr. Enrique Carbó-Argibay
Supervisors: Prof. Paulo Ferreira

Partners: TEandM – Tecnologia, Engenharia e Materiais S.A, Instituto Pedro Nunes – Associação para a Inovação e Desenvolvimento em Ciência e Tecnologia, INL, UT Austin
Funding: COMPETE; FCT

The measuring devices available in the market for manufacturing processes are many times not able to accurately evaluate important process parameters due to positioning problems or deficient signal acquisition and transfer. The Soft4Sense project will create software able to supply the necessary information for depositing thin film device without mechanical/electrical integrity problems
There is a bottleneck that has impeded the commercial application of thin-film devices, not just in Portugal but worldwide: their mechanical integrity. The construction of these films is based on the stacking of layers, each one with a specific role, requiring a suitable matching between them. The mechanical/electrical integrity of the thin film device has to be improved and optimized to allow their reliable and reproducible production in order to be offered to the industrial market. Sputtering is an excellent technique to develop/optimize/adapt new materials, being the perfect solution for optimizing layers matching in stacking.
The software will guide the deposition of the multilayer stacking with the appropriate conditions to achieve a reliable/reproducible product. Although this is only a simple program which, from the information about the required characteristics of the stacking layers (e.g. residual stress level, defects density, electrical characteristics, hardness, Young’s modulus), supplies the deposition conditions for the stacks fabrication, each input information results from a complex task where simulation and experimental work is required in a closed-loop approach.

Researcher: Dr. Enrique Carbó-Argibay
Supervisors: Dr. Lorena Diéguez

Partners: Stemmatters, Biotecnologia e Medicina Regenerativa S.A., INL, ICVS – Life and Health Sciences Research Institute, 2CA – Clinic Academic Center and University of Texas at Austin (UTA)
Funding: POFC – COMPETE; FCT

Cancer, when identified early, is likely to respond more effectively to treatment, resulting in a greater probability of survival, generating less morbidity and reducing the cost of treatment. Early diagnosis focuses on the identification of symptomatic cancer cases at the earliest possible stage as compared to screening that seeks asymptomatic cancer or pre-cancerous lesions. Due to limitations, it is not yet possible to use extensively screening to prevent cancer (primary prevention). Screening can over-diagnose cancer conditions, implying that premalignant lesions for which medical intervention is not advisable neither desirable receive treatment generating co-morbidities that would be otherwise avoidable. This situation has resulted in the recent past in an epidemic of cancers such as prostate cancer and ductal carcinoma in situ.

Remote patient monitoring (RPM) of cancer diseases can be potentially used to increase current predictive rates while contributing to a more cost-effective and accessible diagnosis and treatment. Patients at high risk of cancer recurrence would constitute an ideal population for such improved cancer monitoring tools. These novel tools should have the ability to remotely generate personalized patient data, which should be used to detect disease onset or progression. While RPM has been predominantly applied for the monitorization of vital signs, the extension of such a concept to monitorization of high-risk profile patients would constitute a significant jump forward in the prevention and early diagnosis of cancer patients.

SENTINEL project proposes the innovative development of remote monitoring tools for high-risk profile cancer patients. Such technology aims to increase the positive predictive value (PPV) of cancer screening while facilitating the remote and ubiquitous monitoring of patients on large scale. The main objective of the SENTINEL project is to develop a minimally invasive and biocompatible implantable biosensor to be used in the early tumor surveillance in post-operative prostate cancer patients, supported by the following accomplishments:

• To develop novel biocompatible and injectable formulations able to assure low foreign body reaction after implantation;
• To establish encapsulation protocols for novel plasmonic particles using hydrogel-based formulations;
• To develop simple, affordable and low-risk implantation procedures able to be implemented in a clinical setting;
• To acquire transdermal Raman signals based on implanted biosensor using a handheld Raman device;
• To test the system’s signaling using in vitro, ex vivo and in vivo protocols that model physiologically disease-relevant conditions;
• To process and classify acquired data using machine learning algorithms;
• To develop computational predictive diagnostic protocols using acquired biosensor spectra.