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- Expanding the applications of the wear-resistant titanium aluminum nitride thin-film to include temperature sensingPublication . Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, Pedro; Zorro, Fátima; Carbo-Argibay, Enrique; FGerreira, Paulo J.; Fernandes, Filipe; Fernandes, FilipeThis study investigates an approach to temperature sensing by integrating Titanium Aluminum Nitride (TiAlN), originally engineered for wear and corrosion applications, as a temperature sensor within a multilayered thin film system. A nitride multilayer system was developed by physical vapor deposition (PVD) using a single four-target magnetron sputtering chamber; intermediate vacuum interruption steps were employed for masking procedures. The multilayer architecture design aimed to provide the sensor layer with mechanical protection and electrical shielding. Structural and electrical characterization of the TiAlN single layer revealed semiconductor behavior and stable electrical resistance up to 750 °C, with minimal signal stabilization requirements. Despite the higher Al content, the TiAlN temperature sensor exhibited a cubic crystal structure characterized by diffuse nanolayers, resulting from a two-fold rotational deposition and target configuration. A detailed examination of the multilayer system cross-section containing the TiAlN sensor was conducted using scanning transmission electron microscopy (STEM). The analysis revealed its columnar morphology with the presence of typical PVD growth defects, including voids and droplets. While the presence of these defects may impact the electrical characteristics of the sensor, the selected experimental conditions effectively maintained the structural integrity of the multilayer system despite the vacuum interruptions caused by masking procedures. Validation experiments confirmed the functionality of the multilayer system for temperature measurements up to 400 °C. The signal acquisition system addressed room temperature resistance variations and low sensitivity (thermistor coefficient ∼100 K), resulting in a measured error of approximately 6%. This study demonstrates promising results of TiAlN as a temperature sensor within a multilayered system, expanding its range of potential applications.
- Tribological Comparison of Coatings Produced by PVD Sputtering for Application on Combustion Piston RingsPublication . Ferreira, Ney Francisco; Neis, Patric Daniel; Fernandes, Filipe; Poletto, Jean Carlos; Yaqub, Talha Bin; Cavaleiro, Albano; Vilhena, Luís; Ramalho, AmílcarThis article compares the tribological performance of coatings produced by PVD sputtering. Transition metal dichalcogenide (TMD) coatings doped with carbon (WSC and MoSeC) and nitrogen (WSN and MoSeN) and a conventional diamond-like carbon (DLC) coating are compared. The tribological evaluation was oriented towards the use of coatings on piston rings. Block-on-ring tests in a condition lubricated with an additive-free polyalphaolefin (PAO 8) and at temperatures of 30, 60, and 100 °C were carried out to evaluate the coatings in boundary lubrication conditions. A load scanner test was used to evaluate dry friction and scuffing propensity. In addition to WSN, all other TMD coatings (WSC, MoSeC, and MoSeN) exhibited lower friction than DLC in dry and lubricated conditions. The study reveals that WSC, among TMD coatings, offers promising results, with significantly lower friction levels than DLC, while demonstrating reduced wear and a lower risk of metal adhesion. These findings suggest that WSC may be a viable alternative to DLC in piston rings, with potential benefits for reducing fuel consumption and increasing engine durability.
- Comparative investigation of friction stir welds reinforced with graphene nanoplatelets and copper in AA6082-T6 alloyPublication . Biradar, Rahul; Patil, Sachinkumar; Sharma, Priyaranjan; Fernandes, Filipe; Fernandes, FilipeFriction stir welding (FSW)represents a solid-state welding method renowned for producing highquality joints, particularly in aluminum alloys. This study focuses on enhancing weld strength in the aerospace alloy AA6082-T6. The research involved conducting experiments to create FSW joints in AA6082-T6 by incorporating graphene nanoplatelets(GNPs) and copper as filler materials. Various characteristics of the joints, including microhardness, tensile strength, wear resistance, and corrosion behavior, were meticulously investigated. The experimental findings demonstrated that AA6082-T6 joints reinforced with GNPs exhibited significantly higher weld strength than conventional joints. This improvement can be attributed to the superior bonding and reinforcing effects of GNPs within the aluminum matrix. Furthermore, the GNPs incorporated joints displayed enhanced electrochemical and wear properties. This innovative approach in FSW presents a promising avenue for enhancing weld strength across diverse alloys through the integration of different reinforcement materials.
- Ti-Zr-Nb-(V) refractory alloy coatings deposited by highpower impulse magnetron sputtering: Structure, mechanical properties, oxidation resistance, and thermal stabilityPublication . Fraile, A.; Cavaleiro, D.; Bondarev, A.; Middleburgh, S.C.; Lee, W.E.; Fernandes, F.; Fernandes, FilipeA series of TiZrNb(V) high entropy alloy-based metallic coatings have been deposited using high-power impulse magnetron sputtering (HiPIMS), with variable V concentrations and constant ratios among the other metals. The coatings were analyzed regarding their composition, surface and cross-sectional morphologies, microstructure, roughness, mechanical properties, oxidation resistance, and thermal stability. The structure of the deposited coatings reveals a transition from the bcc crystal structure to an amorphous phase as the V concentration increases. The addition of V also led to a decrease in roughness Ra and an improvement in adhesion, while it did not affect hardness, which remained at ∼10–11 GPa for all samples. Annealing under a protective atmosphere at 400 °C caused structural ordering, which was followed by an increase in mechanical properties. The purpose of the present paper is, therefore, to present a study on the deposition of TiZrNb coatings with increasing V concentration prepared by HiPIMS and to understand the role of V concentration on their structure, chemical composition, mechanical properties, and oxidation resistance. Comparison of the results with those achieved for a reference TiZrNb coating is presented too.
- Comparative analysis of microstructural, compositional, and grazing incidence characteristics of oxide scale on 316L steel: SLM vs. wrought conditionsPublication . Sehat, Alireza; Hadi, Morteza; Isfahani, Taghi; Fernandes, Filipe; Fernandes, FilipeThe aim of this research is to compare the oxidation behavior and characteristics of oxide scale of 316L steel produced by two methods: selective laser melting (SLM) and conventional casting and forming (wrought). To this end, the initial composition and microstructure of samples produced by those methods were first studied. Thermogravimetric analysis (TGA) and long-term isothermal oxidation tests were carried out on the samples and the oxidation kinetics were compared. The oxidized samples were then examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and grazing incidence X-ray diffraction (GIXRD). The results indicated that in the temperature range of 600 °C–900 °C, the oxidation resistance of the SLM alloy is lower than that of the wrought alloy, especially at 800 °C. This is attributed to the combined effect of: i) smaller grain size due to the rapid solidification in the SLM alloy that increases the paths of oxygen penetration, ii) lower presence of chromium and manganese elements in the oxide layer and iii) preferential growth of iron oxide in the form of hillocks on the surface. Surface and cross-section analysis of the oxide layers show that iron oxide is dominant on the surface of the SLM sample at temperatures of 600 °C and 800 °C, and at 800 °C its extended hilly growth leads to significant spallation of the oxide scale and an exponential increase in the oxidation rate. However, at 900 °C, with the formation of a continuous oxide layer containing Fe2MnO4 and CrMnO4, the oxidation rate significantly decreases in both alloys.
- Multi-target neuroprotective effects of herbal medicines for Alzheimer's diseasePublication . Fernandes, Filipe; Barroso, M. Fátima; De Simone, Angela; Emriková, Eliška; Dias-Teixeira, Mónica; Pereira, José Paulo; Chlebek, Jakub; Fernandes, Virgínia Cruz; Rodrigues, Francisca; Andrisano, Vincenza; Delerue-Matos, Cristina; Grosso, ClaraEthnopharmacological relevance Alzheimer's disease is the most common form of dementia, but its treatment options remain few and ineffective. To find new therapeutic strategies, natural products have gained interest due to their neuroprotective potential, being able to target different pathological hallmarks associated with this disorder. Several plant species are traditionally used due to their empirical neuroprotective effects and it is worth to explore their mechanism of action. Aim of the study This study intended to explore the neuroprotective potential of seven traditional medicinal plants, namely Scutellaria baicalensis, Ginkgo biloba, Hypericum perforatum, Curcuma longa, Lavandula angustifolia, Trigonella foenum-graecum and Rosmarinus officinalis. The safety assessment with reference to pesticides residues was also aimed. Materials and methods Decoctions prepared from these species were chemically characterized by HPLC-DAD and screened for their ability to scavenge four different free radicals (DPPH•, ABTS•+, O2•‒ and •NO) and to inhibit enzymes related to neurodegeneration (cholinesterases and glycogen synthase kinase-3β). Cell viability through MTT assay was also evaluated in two different brain cell lines, namely non-tumorigenic D3 human brain endothelial cells (hCMEC/D3) and NSC-34 motor neurons. Furthermore, and using GC, 21 pesticides residues were screened. Results Regarding chemical composition, chromatographic analysis revealed the presence of several flavonoids, phenolic acids, curcuminoids, phenolic diterpenoids, one alkaloid and one naphthodianthrone in the seven decoctions. All extracts were able to scavenge free radicals and were moderate glycogen synthase kinase-3β inhibitors; however, they displayed weak to moderate acetylcholinesterase and butyrylcholinesterase inhibition. G. biloba and L. angustifolia decoctions were the less cytotoxic to hCMEC/D3 and NSC-34 cell lines. No pesticides residues were detected. Conclusions The results extend the knowledge on the potential use of plant extracts to combat multifactorial disorders, giving new insights into therapeutic avenues for Alzheimer's disease.