A carregar...
Projeto de investigação
Institute of Nanostructures, Nanomodelling and Nanofabrication
Financiador
Autores
Publicações
Microstructural evolution and phase stability in Nb-containing interstitial Fe-Mn-Co-Cr-C high-entropy alloys
Publication . Moura, I. A. B.; Ribamar, G. G.; Chuang, A. C.; Nunes, T. S.; Shen, Jiajia; Zhang, Wei; Rodrigues, P. Freitas; Pereira, A. B.; Pei, Yutao; Zhang, F.; Oliveira, J. P.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Elsevier BV
The influence of Nb on phase stability and microstructural evolution in an interstitial Fe-Mn-Co-Cr-C high-entropy alloy was investigated using in-situ synchrotron X-ray diffraction (SXRD) during laser melting. Scheil-Gulliver simulations predict the formation of σ and γ-f.c.c. phases in all three alloys, along with NbC in Nb-containing compositions. SXRD confirmed the presence of most predicted phases, but the σ phase was absent. Nb promotes crystallite refinement and increases dislocation density, though excessive additions reduce refinement efficiency due to solubility limits and secondary phase formation. Furthermore, Nb addition also enhances ε-h.c.p. phase formation by reducing stacking fault energy through NbC-induced carbon depletion. Analysis of intensity peak evolution reveals that Nb alters preferred grain orientations, reducing {111}γ intensity while enhancing {220}γ, leading to a more isotropic grain distribution. Overall, Nb plays a key role in phase selection, microstructure refinement, and preferred orientation evolution, allowing the tailored microstructure of high-entropy alloys via rapid solidification.
The Potential of Shape Memory Alloys in Riveting Applications
Publication . Camacho, Edgar; Freitas Rodrigues, Patrícia; Braz Fernandes, Francisco Manuel; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI - Multidisciplinary Digital Publishing Institute
This study explores the use of shape memory alloys, specifically nickel-titanium (NiTi- Ti-rich), in plate joining processes through riveting. Through the shape memory effect (SME), SMAs offer innovative solutions for joining components, mainly in the aeronautical and aerospace fields, indicating their promising applications. This research presents several characterizations, including differential scanning calorimetry, compression dilatometry, X-ray diffraction using synchrotron radiation, and thermomechanical testing, to assess the feasibility and performance of shape memory alloy rivets. In addition, the samples were subjected to recrystallization heat treatment to evaluate their reusability. The results demonstrated that shape memory alloy rivets are effective, achieving a maximum load of 340 N for two joined components. However, their application is optimal for materials with yield strengths lower than the stress-induced SME. Moreover, the process enhances the joined components’ hardening and increases the rivet’s thermal hysteresis. This research confirms the viability of shape memory alloys for riveting processes, offering a new avenue for advanced joining techniques. The findings provide a foundation for their further development and application in various industries requiring precise and reliable joining methods.
Energy harvesting and movement tracking by polypyrrole functionalized textile for wearable IoT applications
Publication . Ferreira, Guilherme; Das, Shubham; Coelho, Guilherme; Silva, Rafael R. A.; Goswami, Sumita; Pereira, Rui N.; Pereira, Luís; Fortunato, Elvira; Martins, Rodrigo; Nandy, Suman; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; Elsevier BV
Textiles for health and sporting activity monitoring are on the rise with the advent of smart portable wearables. The intention of this work is to design wireless monitoring wearables, based on widely available textiles and low environmental impact production technologies. Herein we have developed a polymeric ink which is able to functionalize different types of textile fibers (including silver conducting fibers, cotton, and commercial textile) with polypyrrole. These fibers were weaved together with a thinner silver conducting fiber and carbon fiber to form a touch-sensitive energy harvesting system that would generate an electric output when mechanical pressure is applied to it. Different prototypes were manufactured with loom weaving accessories to simulate real textile cloths. By simple touch, the prototypes produced a maximum voltage of 244 V and a maximum power density of 2.29 W m−2. The current generated is then transformed into a digital signal, which is further utilized for human motion or gesture monitorization. The system comprises a wireless block for the Internet of Things (IoT) applicability that will be eventually extended to future remote health and sports monitoring systems.
Electrospun poly(N-vinylpyrrolidone) membranes with Ag nanoparticles for wound dressings
Publication . Pádua, Ana Sofia; Rosa, Rita Morais; Vieira, Tânia; Henriques, Célia; Silva, Jorge Carvalho; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DF – Departamento de Física; Editions de Sante
Wound dressings have long been used to promote the healing of skin injuries. In the work reported here, fibrous membranes were produced by electrospinning poly(N-vinylpyrrolidone) (PVP) solutions containing silver nitrate at varying mass ratios (1:200, 1:100 and 1:50 AgNO3:PVP). PVP solutions without AgNO3 were used as a control. The electrospun membranes were irradiated using 254 nm UV light to simultaneously photo-crosslink PVP and promote the formation of silver nanoparticles (AgNPs). The formation of AgNPs was confirmed by scanning electron microscopy and transmission electron microscopy, as well as by detecting the surface plasmon resonance peak at 420 nm in the UV–Vis spectrum during release studies. The swelling rate of fibrous membranes was lower for those containing AgNPs compared to PVP-only membranes. The Kirby-Bauer diffusion test performed against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans showed that all AgNPs-containing membranes exhibited an inhibitory effect on all microorganisms tested. The in vitro cytotoxicity assay showed that membranes with lower silver concentration were less cytotoxic. This study presents a simple route to producing a wound dressing with antimicrobial action that has a swelling behavior capable of absorbing exudates, provides controlled release of silver and has low cytotoxicity.
In-situ microstructural evolution during tensile loading of CoCrFeMnNi high entropy alloy welded joint probed by high energy synchrotron X-ray diffraction
Publication . Dias, P.; Lopes, J. G.; Curado, T.; Maawad, E.; Schell, N.; Kim, H. S.; Oliveira, J. P.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DEMI - Departamento de Engenharia Mecânica e Industrial; Maney Publishing
The research regarding high entropy alloys (HEAs) has proved them to be suitable for engineering applications. Nevertheless, assessing their processability is key for industrial deployment. Of special relevance in terms of processing techniques arised welding. In this work, Gas Tungsten Arc Welding (GTAW) was chosen as a processing method to attest for the suitability of the equiatomic CoCrFeMnNi HEA for one of the most common real-world mechanical solicitations, tensile loading. We delve into an in-situ synchrotron X-ray diffraction analysis of the mechanical behavior of a high-performing GTAW CoCrFeMnNi HEA joint. Local analysis of the microstructure evolution, considering the base material, heat affected zone and fusion zone, was performed by tracking changes in the diffracted intensity and lattice strain. Orientation-dependent evolution is highlighted by considering partial azimuthal integration detailing texture impact across the joint. Evidence of strain concentration at specific locations is correlated with the microstructure and overall macroscopic mechanical behavior.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
LA/P/0037/2020