ICI - C-MAST | Documentos por Auto-Depósito
Permanent URI for this collection
Browse
Recent Submissions
- Sociodemographic Data and Work-Related Musculoskeletal Symptoms in the Metal Polishing Industry: A Case Study in Central PortugalPublication . Alves, Joel; Lima, Tânia M.; Gaspar, Pedro DinisThe prevalence of work-related musculoskeletal disorders is a red flag in industries and is considered an occupational health issue that affects the operator’s well-being, safety, and health. This study contributes to understanding the impact of Industry 5.0 on the workforce and emphasizes the importance of promoting a safe and healthy working environment. Thus, it focuses on the assessment of anthropometric characteristics and work-related musculoskeletal symptoms in a real industrial environment, specifically in the metal polishing sector of a metallurgical industry in Portugal. The research collected data on physical attributes, health status, and musculoskeletal symptoms using the Portuguese version of the Nordic Musculoskeletal Questionnaire, and incorporated sociodemographic data, including age, gender, and professional status, to provide a comprehensive understanding of the active workforce. The results were analyzed by gender and age clusters and revealed a prevalence of musculoskeletal symptoms, particularly in the spinal column and upper limbs, with a significant impact on the ability to perform work tasks. The need for preventive measures and ergonomic interventions to minimize the high predominance of musculoskeletal symptoms in Portuguese industries is also highlighted to improve the working conditions and enhance the well-being and health of operators.
- Assessing Psychosocial Work Conditions: Preliminary Validation of the Portuguese Short Version of the Copenhagen Psychosocial Questionnaire IIIPublication . Pinto, Ana; Carvalho, Carla; Mónico, Lisete S.; Moio, Isabel; Alves, Joel; Lima, Tânia M.The working environment is a crucial aspect to considerfor guaranteeing a sustainable life. However, workers are exposed to various health risks daily, namely, psychological risks. These risks can be due to imbalances on the part of the workers themselves or to organisational and interfunctional risk factors arising from interactions within companies and the challenges of professional responsibilities. Over the past 20 years, the Copenhagen Psychosocial Questionnaire (COPSOQ) has become one of the most prominent tools for assessing psychological and social factors at work. This study aimed to present, discuss, and evaluate aspects of the cultural adaptation and preliminary psychometric validation of the short version of COPSOQ III for a Portuguese sample. For this purpose, we used data from 361 participants employed in the industrial (30.7%) and services (69.3%) sectors across various regions of Portugal. A third-order confirmatory factor analysis (CFA) was performed using AMOS, revealing an acceptable fit. The results also demonstrate the robustness of the measurement model, confirming its reliability and validity. In light of some limitations of this preliminary study, directions for future research are proposed. Thus, a tool for assessing psychosocial risks is disseminated, making it possible to achieve more sustainable working environments where the operator’s health and well-being are prioritised.
- Evaluation of the Physicochemical Properties and Active Response of Piezoelectric Poly(vinylidene fluoride-co-trifluoroethylene) as a Function of Its MicrostructurePublication . Gonçalves, R.; Cardoso, V. F.; Pereira, Nelson; Oliveira, Juliana; Nunes-Pereira, João; Costa, C. M.; Lanceros-Mendez, SenentxuPoly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), microstructures have been produced using different solvents, including green ones, by different techniques, such as solvent casting, screen-printing, replica molding, electrospray, and electrospinning. The obtained microstructures span from simple porous and dense films to spheres, fibers, and patterned three-dimensional architectures, with no significant variation in their physicochemical and electrical properties. The simplicity, low cost, and reproducibility of the processing techniques allied to their versatility to adapt to other materials to produce controlled and tailored microstructures with specific properties demonstrate their potential in a wide range of technological applications, including biomedical, energy storage, sensors and actuators, and filtration.
- Modelling of elastic modulus of CaZrO3-MgO composites using isotropic elastic and anisotropic modelsPublication . Nunes-Pereira, João; Carneiro, Pedro; Maceiras, Alberto; Baudin, Carmen; Pereira Silva, AStarting from synthetic raw materials (CaZrO3 and MgO), microstructural and mechanical properties were optimised in order to obtain dense multiphasic ceramic, then finite element method (FEM) of an equimolar (1:1) CaZrO3-MgO composite was performed in order to obtain the effective elastic modulus. Composite presents two main phases of orthorhombic CaZrO3 (81.5 wt.%) and cubic MgO (18.5 wt.%); For 1500 °C, relative density of 99.9%, characteristic strength of 168 MPa, hardness of 7.8 MPa and toughness of 2.5 MPa.m1/2 were obtained. FEM simulation was performed using two representative volume elements (RVE’s) with edge lengths of 14 μm (933 grains) and 17 μm (1670 grains), using isotropic elastic model, and anisotropic on specific set of crystallographic planes. The results of FEM using isotropic approach for the two RVE’s are perfectly aligned with the experimental (245 GPa), while the anisotropic model shows a difference of 6.5%.
- Characterization of a Functionally Gradient Ceramic Based on CaZrO3 – MgOPublication . Babo, Débora Rafaela Telha de; Nunes-Pereira, João; Silva, Pedro D.; Pena, Pilar; Baudin, Carmen; Pereira Silva, AIn the case, where the structure is exposed to severe conditions of operation, such as high strength, wear and high-temperature gradients (e.g. engine components, insulation system, thermal barrier and thermal shield) must be applied. In this work, it was developed and characterized a functional gradient ceramic coating. A ceramic composite based in CaZrO3 – MgO was used in order to design a material with successive layers of molar composition 2:3, 1:1 and 1:3 of CaZrO3:MgO, respectively. A dense material was obtained by sintering assisted reaction (Figure 1). Thermal conductivity at room temperature, hardness, fracture toughness, surface energy, and microstructure were characterized.The results show for monolithic specimens of 2:3 CZ, 1:1 CZ and 1:3 CZ a H of 9,9 GPa, 9,8 GPa and 10,1GPa; a Kc of 1,6 MPa.m1/2, 1,7 MPa.m1/ and 2,1 MPa.m1/2; a k of 0,59 W/mK; 0,76 W/mK and 0,79 W/mK; and a surface energy (SE) of 43,27 mN/m, 51,39 mN/m and 46,55 mN/m, respectively. The functional gradient ceramic shows a H of 10,7 GPa, a Kc of 1,97 MPa.m1/2; a k of 0,82 W/mK and SE of 53,98 mN/m. The individual composition and the functional gradient ceramic show a similar relative density of 4,3 g/cm3 and a porosity of 0,2%. This design methodology has the advantage of allowing the properties of the same material to suit different substrates.
- Development and characterization of ceramic composites based on CaZrO3-MgOPublication . Nunes-Pereira, João; Pena, Pilar; Baudin, Carmen; Pereira Silva, AAdvanced materials for severe environment conditions, such as high temperature, wear and high erosion and corrosion, are of growing interest, namely for transport and energy industries. Particularly, in aerospace industry the increase of working temperature of engines and turbines combined with weight reduction will give rise to higher thrust and lower fuel consumption and consequently less emissions. In this sense, new ceramic multiphasic composites based on calcium zirconate (CaZrO3) and magnesium oxide (MgO) are being proposed with suitable thermal, mechanical and chemical properties for severe conditions application. In the present work, an equimolar composition of CaZrO3-MgO, processed from easily and accessible synthetic raw materials, have been developed and the particle size distribution optimized by milling under controlled conditions. CaZrO3-MgO ceramic composites uniaxially pressed disks have been produced by rate controlled sintering during 2 hours at 1400, 1450 and 1500 ºC, respectively. The physical, microstructural and mechanical properties, have been assessed to evaluate the performance and suitability of the processed materials for high responsibility applications. A homogeneous microstructure was obtained for all sintering temperature samples with porosities ranging between ~10 %, for samples sintered at 1400 ºC, to ~100 % theoretical density for samples sintered at 1500 ºC. Diametral compression strength follows the Weibull distribution with characteristic strengths between ~50 and 170 MPa, Vickers hardness reach values above 8 GPa, while the facture toughness present values between 2 and 3 MPa.m1/2, for 1400 and 1500 ºC respectively. These results show that the ceramic composites based on CaZrO3-MgO sintering at 1500 ºC proved to be a suitable alternative to high responsibility applications.
- Recent Progress on Piezoelectric, Pyroelectric, and Magnetoelectric Polymer‐Based Energy‐Harvesting DevicesPublication . Costa, Pedro; Nunes-Pereira, João; Pereira, Nelson; Castro, Nélson; Gonçalves, Sérgio; Lanceros-Mendez, SenentxuEnergy harvesting from the environment based on electroactive polymers has been increasing in recent years. Ferroelectric polymers are used as mechanical-to-electrical energy transducers in a wide range of applications, scavenging the surrounding energy to power low-power devices. These energy-harvesting systems operate by taking advantage of the piezoelectric, pyroelectric, and magnetoelectric properties of the polymers, harvesting wasted environmental energy and converting it mainly into electrical energy. There have been developed different nano- and micro-scale power harvesters with an increasing interest for powering mobile electronics and low-power devices, including applications in remote access areas. Novel electronic devices are developed based on low-power solutions, and therefore, polymer-based materials represent a suitable solution to power these devices. Among the different polymers, the most widely used in the device application is the poly(vinylidene fluoride) (PVDF) family, due to its higher output performance.
- Mesoporous poly(vinylidene fluoride-co-trifluoroethylene) membranes for lithium-ion battery separatorsPublication . Costa, C. M.; Kundu, Manab; Dias, J. C.; Nunes-Pereira, João; Botelho, Gabriela; Silva, M. M.; Lanceros-Mendez, SenentxuMesoporous separator membranes based on poly(vinylidene fluoride-co-trifluoroethylene), PVDF-TrFE, were prepared through the removal of ZnO nanoparticles from the polymer matrix composite. Different filler concentrations were used, and the evaluation of the morphology, mechanical properties, uptake and ionic conductivity of the membranes were demonstrated that they depend on initial ZnO content in the composite. On the other hand, the vibration peaks characteristics of PVDF-TrFE and the thermal properties are independent on initial filler content. The membrane with the best ionic conductivity, 1.6 mS/cm, is the one prepared after 70 wt.% ZnO removal. The separator membranes were assembled in Li/C-LiFePO4 half-cells exhibiting good rate capability and cycling performance, the best battery performance being obtained for the PVDF-TrFE after 70 wt.% ZnO removal. The good performance of the developed separators was also demonstrated in full battery cells. Thus, a way to tailor membrane mesoporosity is presented and it is shown that the obtained membranes represent suitable separators for lithium-ion battery applications.
- Surface wettability modification of poly(vinylidene fluoride) and copolymer films and membranes by plasma treatmentPublication . Correia, Daniela M.; Nunes-Pereira, João; Alikin, Denis; Kholkin; Carabineiro, S.A.C.; Rebouta, Luis; Rodrigues, Marco S.; Vaz, F.; Costa, C. M.; Lanceros-Mendez, SenentxuThis manuscript reports on the modification of the surface wettability of poly (vinylidene fluoride) (PVDF) and PVDF copolymer films and membranes by plasma treatments at different conditions, under oxygen and argon atmospheres. It is shown that a more pronounced decrease of the contact angle after O2 plasma treatments is obtained, with a decrease of ∼20-30° for PVDF and its copolymers films, leading also to superhydrophilic membranes. This effect is related to a defluorination process, followed by the incorporation of oxygen atoms onto the surface of membranes that occurs during the surface modification. The influence of plasma treatments on surface morphology and topography was studied by atomic force microscopy, showing a decrease in the mean surface roughness with the plasma treatments, being more noticeable for Ar treatments. Finally, it is also shown that plasma treatments under Ar and O2 did not induce modifications in the physicochemical and thermal properties of PVDF and PVDF copolymers. The chemical reaction mechanism after plasma treatment is proposed for the different copolymers.
- Development of a Background-Oriented Schlieren (BOS) System for Thermal Characterization of Flow Induced by Plasma ActuatorsPublication . Moreira, Miguel; Rodrigues, Frederico; Cândido, Sílvio; Santos, Guilherme; Pascoa, JoséCold climate regions have great potential for wind power generation. The available wind energy in these regions is about 10% higher than in other regions due to higher wind speeds and increased air density. However, these regions usually have favorable icing conditions that lead to ice accumulation on the wind turbine blades, which in turn increases the weight of the blades and disrupts local airflow, resulting in a reduction in wind turbine performance. Considering this problem, plasma actuators have been proposed as devices for simultaneous flow control and deicing. These devices transfer momentum to the local airflow, improving the aerodynamic performances of the turbine blades while producing significant thermal effects that can be used to prevent ice formation. Considering the potential application of plasma actuators for simultaneous flow control and deicing, it is very important to investigate the thermal effects induced by these devices. However, due to the significant electromagnetic interference generated by the operation of these devices, there is a lack of experimental techniques that can be used to analyze them. In the current work, a background-oriented Schlieren system was developed and is presented as a new experimental technique for the thermal characterization of the plasma-induced flow. For the first time, the induced flow temperatures are characterized for plasma actuators with different dielectric materials and different dielectric thicknesses. The results demonstrate that, due to the plasma discharge, the temperature of the plasma-induced flow increases with the increase of the applied voltage and may achieve temperatures five times higher than the room temperature, which proves the potential of plasma actuators for deicing applications. The results are presented and discussed with respect to the potential application of plasma actuators for simultaneous flow control and deicing of wind turbine blades.