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- Green synthesis of nanoparticles from olive oil waste for environmental and health applications: A reviewPublication . Afonso, Inês Santos; Cardoso, Beatriz D.; Nobrega, Glauco; Minas, Graça; Ribeiro, J.E.; Lima, Rui A.Environmental degradation is a growing concern, driving researchers to explore eco-friendly nanoparticle (NP) synthesis, for diverse applications. Within this context, the employment of olive oil waste (OOW) as a green source for the synthesis of NPs has emerged as a viable alternative to conventional techniques. The olive industry has a significant impact in the Mediterranean region, and alongside it, comes the OOW, where most of it cannot be left untreated. In the present review, a comprehensive overview of the NPs’ green synthesis derived from OOW and its potential applications in both environmental and health areas have been assessed, outlining its major challenges and potential outcomes for future research. Both principles and methods of green NPs synthesis were also explored, focusing on the unique properties of OOW as an effective agent for reduction and stabilization, as well as the characterization techniques used for characterizing the synthesized NPs. The OOW-derived NPs can have a wide variety of environmental applications including water purification, pollutant degradation, and remediation of contaminated environments. In the health field, the OOW applications include drug delivery systems, antimicrobial activity and cancer therapy. These OOW NPs have been successfully used as efficient drug delivery vehicles to cancer cells, enhancing treatment outcomes and potentially minimizing side effects. However, it is imperative to point out the importance of performing in-depth toxicity assessments, particularly at higher concentrations of NPs.
- A Review of Novel Heat Transfer Materials and Fluids for Aerospace ApplicationsPublication . Nobrega, Glauco; Cardoso, Beatriz D.; Souza, Reinaldo Rodrigues de; Pereira, José Eduardo; Pontes, Pedro; Catarino, Susana O.; Pinho, Diana M.D; Lima, Rui A.; Moita, Ana S.The issue of thermal control for space missions has been critical since the early space missions in the late 1950s. The demands in such environments are heightened, characterized by significant temperature variations and the need to manage substantial densities of heat. The current work offers a comprehensive survey of the innovative materials and thermal fluids employed in the aerospace technological area. In this scope, the materials should exhibit enhanced reliability for facing maintenance and raw materials scarcity. The improved thermophysical properties of the nanofluids increase the efficiency of the systems, allowing the mass/volume reduction in satellites, rovers, and spacecraft. Herein are summarized the main findings from a literature review of more than one hundred works on aerospace thermal management. In this sense, relevant issues in aerospace convection cooling were reported and discussed, using heat pipes and heat exchangers, and with heat transfer ability at high velocity, low pressure, and microgravity. Among the main findings, it could be highlighted the fact that these novel materials and fluids provide enhanced thermal conductivity, stability, and insulation, enhancing the heat transfer capability and preventing the malfunctioning, overheating, and degradation over time of the systems. The resulting indicators will contribute to strategic mapping knowledge and further competence. Also, this work will identify the main scientific and technological gaps and possible challenges for integrating the materials and fluids into existing systems and for maturation and large-scale feasibility for aerospace valorization and technology transfer enhancement.
- Estudo de compósito híbrido de fibra de vidro e liga de Níquel-TitânioPublication . Nobrega, Glauco; Andrade, Carlos A.R.; Santos, Luiz Alberto dosOs materiais compósitos vêm ganhando cada vez mais destaque na indústria devido às suas excelentes propriedades químicas e mecânicas, assim como a sua combinação com ligas de memória de forma (LMF) podendo gerar materiais com características capazes de operar nas mais complexas áreas da engenharia. Nesse sentido, é importante explorar modos de fabricação bem como ser capaz de prever o seu comportamento ao se variar as quantidades de material presentes. O compósito híbrido foi fabricado de duas formas: uma com fios de LMF entre as mantas de fibra de vidro e outra com o fio entrelaçado à manta. Na abordagem experimental, A LMF foi caracterizada através da realização do ensaio de varrimento diferencial de calorimetria (DSC - Differential scanning calorimeter), ensaio de tração, espectrometria de absorção atômica por chama e análise metalográfica. O compósito híbrido, por sua vez foi submetido ao ensaio de tração. Realizaram-se ainda ciclos térmicos em ambos os materiais. Por fim, os resultados obtidos foram comparados com outros estudos, método de elemento finito e regra da mistura. Observou-se que os fios de LMF tem a capacidade de aumentar o módulo de elasticidade dos compósitos, de forma que o método que mais se aproximou dos resultados experimentais foi o de MEF. Através da comparação dos métodos de fabricação, verificou-se que é possível se produzir o compósito por um método que pode ser automatizado.
- Experimental evaluation of green nanofluids in heat exchanger made oF PDMSPublication . Nobrega, Glauco; Souza, Reinaldo Rodrigues de; Cardoso, Beatriz D.; Afonso, Inês Santos; Pereira, José Eduardo; Cardoso, Elaine; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.Conventional methods for synthesizing metallic nanoparticles face challenges such as instability and environmental concerns. Therefore, new, simpler, and more eco-friendly methods are being explored. In this context, the study reports a green synthesis process to produce magnetic iron oxide nanoparticles using an aqueous extract of the alga Chlorella vulgaris. This process leverages natural resources to create a sustainable nanofluid known as green nanofluid. To evaluate the characteristics of this nanofluid, experimental measurements of wettability, viscosity, thermal conductivity, and qualitative stability analysis were conducted. An experimental setup consisting of a heat exchanger made of polydimethylsiloxane (PDMS) was used to assess the thermal performance and the results were compared to theoretical equations and numerical simulation. Additionally, thermographic imaging of temperature gradients as the fluids passed over the heated surface of the serpentine channel were made. The main findings confirmed that the nanofluid was more stable than that obtained by traditional methods and had a more uniform temperature distribution over the heat exchanger. The higher concentration exhibited superior thermal performance compared to DI-Water. Moreover, the green nanofluid was used at a weight concentration of 0.1 wt%, provided thermal performance results of nearly 4.5% superior to those estimated by the numerical model and 6.4% higher than those experimentally obtained with the base fluid, respectively. Finally, the results obtained for the nanofluid also showed an average increase of around 5% in the viscosity of the base fluid, with a more significant sedimentation at a concentration of 0.1 wt%.
- Conventional and recent advances of vegetable oils as metalworking fluids (MWFs): a reviewPublication . Afonso, Inês Santos; Nobrega, Glauco; Lima, Rui A.; Gomes, José R.; Ribeiro, J.E.Vegetable oils have been used as metalworking fluids (MWFs) for many years, particularly in small-scale metalworking operations and in industries where environmental regulations are strict. Before the development of modern MWFs, vegetable oils were one of the most common lubricants used for metalworking tools. The use of vegetable oils can be traced back to ancient civilizations such as Egypt, Greece, and Rome, where olive oil was commonly used to lubricate metal tools and weapons. Today, vegetable oils are used as MWFs in a variety of applications. They are often combined with additives or nanoparticles to enhance their performance, such as improving the lubricity, cooling properties, and stability of the oil, as well as reducing friction and wear on the cutting tool. Additives, such as antioxidants, anti-wear agents, and extreme pressure (EP) additives, can be used to improve the performance of vegetable oils as cutting fluids. Compared to standard MWFs, vegetable oils are generally more biodegradable and environmentally friendly, and can be more cost-effective. However, MWFs may offer superior performance in certain areas, such as lubrication and cooling. Ultimately, the choice of MWFs will depend on the specific requirements of the metalworking operation and the balance between performance, cost, and environmental considerations. As the demand for sustainability and environmental responsibility continues, the use of vegetable oils as MWFs is likely to become even more popular in the future. Overall, vegetable oils offer a viable and potentially attractive alternative to standard MWFs in certain applications. This review highlights both conventional and most recent advances in vegetal oils frequently used as lubricant fluids in manufacturing processes.
- Cooling performance of an acrylic serpentine with a rectangular cross sectionPublication . Nobrega, Glauco; Barbosa, F.M.; Soares, Filipe de Almeida da Silva; Ralha, R.; Souza, Reinaldo Rodrigues de; Ribeiro, J.E.; Moita, Ana S.; Lima, Rui A.In recent years, photovoltaic panels have been established as one of the main sources of electricity considered to be clean. Its efficiency and lifetime are greatly influenced by the operating temperature. Active cooling using cylindrical copper serpentines is one of the most common methods for many systems. However, due to the cylindrical geometry of the tubes, the contact with the plate is a point and its area tends to be zero. In this way, serpentines that provide a bigger contact area between the heat removal system and the solar panel board are desired. Serpentines manufactured by machining acrylic plates in CNC milling machines allow the construction of a channel with a rectangular cross-section with a considerable area of contact between the channel and the plate. The obtained results show that there was a significant improvement in the heat exchange between the plate and the thermofluid when the acrylic serpentine with a rectangular section was used.
- Characterization techniques of a shape memory nickel titanium alloyPublication . Andrade, Carlos A.R.; Soares, Filipe de Almeida da Silva; Nobrega, Glauco; Hilário, Jean César; Santos, LuizThis paper presents a characterization processes study of metallic alloys, more specifically the shape memory alloys (SMA) composed by Nickel and Titanium (NiTinol). Two different wire suppliers were studied, starting with metallographic analysis until observe the contours of the grain wires. Differential scanning calorimetry (DSC) test was also performed to obtain phase transformation temperatures of the NiTinol alloys. Finally, after several tensile tests, some results were obtained for stresses, strains, elasticity modules and maximum rupture deformation.
- Exploring heat exchange in space: Recent advances in two-phase fluid experiments in microgravityPublication . Nobrega, Glauco; Afonso, Inês Santos; Cardoso, Beatriz D.; Souza, Reinaldo Rodrigues de; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.Thermal regulation has assumed a central role in space expeditions ever since the inception of Sputnik-1 in 1957. Throughout the years, numerous techniques have been developed to regulate temperatures in spacecraft and space habitats. Initially, passive systems like heat shields and thermal linings were employed, while newer missions embrace active cooling using fluids like ammonia and water. With significant advancements in lunar exploration, thermal management systems have been integrated to ensure effective heat protection and dissipation. Experiments carried out in drop towers, parabolic flights, sounding rockets, and aboard the International Space Station (ISS) have yielded valuable insights into the physics of fluids, pool boiling, boiling in two-phase flow, and cooling phenomena. However, conducting tests in microgravity conditions can lead to lower performances, and accurate numerical simulations remain a challenge. At present, various organizations are conducting research to drive progress in thermal management and enhance the technology of space devices. This review describes the most recent advances in two-phase fluid experiments in microgravity. Furthermore, the major challenges that persist in this field are presented and discussed, along with observations on trends and possibilities for the future of thermal control in space. This review attempts to be a relevant guide for future research and developments on thermal control in space.
- Parametric optimization of the GMAW welding process in thin thickness of austenitic stainless steel by Taguchi methodPublication . Nobrega, Glauco; Souza, Maria Sabrina; Rodríguez-Martín, Manuel; Rodríguez-Gonzálvez, Pablo; Ribeiro, J.E.In the present work, an analysis of different welding parameters was carried out on the welding of stainless-steel thin thickness tubes by the Gas Metal Arc Welding (GMAW) process. The influence of three main parameters, welding voltage, movement angle, and welding current in the quality of the welds, was studied through a specifically designed experimental process based on the establishment of three different levels of values for each of these parameters. Weld quality is evaluated using destructive testing (macrographic analysis). Specifically, the width and root penetration of the weld bead were measured; however, some samples have been disregarded due to welding defects outside the permissible range or caused by excessive melting of the base metals. Data are interpreted, discussed, and analyzed using the Taguchi method and ANOVA analysis. From the analysis of variance, it was possible to identify the most influential parameter, the welding voltage, with a contribution of 43.55% for the welding penetration and 75.26% for the bead width, which should be considered in the designs of automatic welding processes to improve the quality of final welds.
- Experimental Investigation of Green Nanofluids: Assessment of Wettability, Viscosity and Thermal ConductivityPublication . Nobrega, Glauco; Cardoso, Beatriz D.; Barbosa, Filipe; Pinho, Diana; Abreu, Cristiano; Souza, Reinaldo Rodrigues de; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.Metallic nanoparticles are a type of nanomaterial synthesized from metallic precursors. Due to their unique physiochemical, electrical, and optical properties, metallic nanoparticles are widely studied and applied in various areas such as medicine, electronics, and heat transfer systems. However, conventional synthesis methods to produce metallic nanoparticles face challenges such as instability and environmental concerns, prompting the exploration of greener synthesis methods. Green synthesis uses natural resources like plants and algae as reducing agents, offering a more environmentally friendly approach for the synthesis of metallic nanoparticles. These green-synthesized metallic nanoparticles can enhance heat transfer by becoming part of nanofluids (NFs), which are colloidal mixtures of NPs in a fluid base. NFs, employed for heat transfer. As a result, it is essential to characterize the NFs regarding wettability, viscosity, and thermal conductivity. The results of the spectrophotometer confirmed the green synthesis of NPs, and it was observed that the increase in NP concentration impacted the contact angle, improving the ability to wet. The thermal conductivity is also modified, with an improvement of 11.3% compared to distilled water, without a significant increase in fluid viscosity.