ISEP – DEM – Artigos
Permanent URI for this collection
Browse
Browsing ISEP – DEM – Artigos by Sustainable Development Goals (SDG) "09:Indústria, Inovação e Infraestruturas"
Now showing 1 - 10 of 19
Results Per Page
Sort Options
- Can ZrAlN thin films be used as thermistor sensors for temperature assessment?Publication . Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, Pedro; Bondarchuk, Oleksandr; Fernandes, FilipeThe electrical characteristics and conduction mechanisms of ZrAlN thin films for their potential use as thermistor sensors were assessed. Various compositions of Zr1-xAlxN were synthesized by sputtering and studied up to 200 °C to understand their sensitivity and applicability. Among the compositions studied, the ones with x = 0.34 and x = 0.46 showed the highest sensitivities, reaching values close to 3000 K. However, the thermo-resistive properties exhibited by these compositions limited their utilization above 100 °C. Zr1-xAlxN film compositions with x higher than 0.46 showed amorphous structures and were found to be insulative. Composition with x = 0.26, within the cubic phase, showed the most promising electrical properties regarding temperature sensing in the studied range. XPS analysis of this composition confirmed the presence of Zr-N and Al-N bonds, with a Zr3+ oxidation state, which suggests the availability of a free electron contributing to the electrical conduction. Impedance measurements performed at different temperatures for this composition revealed the dominant role of the grain boundaries in the conduction mechanism, based upon electron hopping between grains, overcoming the energy barrier imposed by the grain boundaries. ZrAlN thin films demonstrate negative temperature coefficient (NTC) thermistor behavior, expanding their applications beyond protective coatings to temperature monitoring.
- 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.
- 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.
- Deciphering the mechanical strengthening mechanism: Soft metal doping in ceramic matrices: A case study of TiN-Ag filmsPublication . Luan, Jing; Kong, Fanlin; Xu, Junhua; Fernandes, Filipe; Evaristo, Manuel; Dong, Songtao; Cavaleiro, Albano; Ju, Hongbo; Fernandes, FilipeSoft metals have been widely added into ceramic-based films for fully meeting the demanding requirements of green tribological applications. However, the resulting considerable increase of the mechanical strength by adding a soft metal below 5 at.%, which reversed the rule-of-mixture, was still not fully revealed. In this paper, a case study of TiN-Ag films was carried out to investigate the strengthening mechanism induced by adding soft metal in TiN-Ag composite/multilayered films deposited by magnetron sputtering. The results showed that dual-phases of fcc-TiN and fcc-Ag co-existed in the composite films with the Ag particles embedded in the matrix. In some areas of the Ag particles, with a size below 4 nm, epitaxial growth with the TiN template was detected, which obliged the lattice to be distorted and shrunken. Consequently, both hardness and elastic modulus were enhanced from 21 and 236 GPa, for the reference TiN film, to 26 and 323 GPa for the TiN-Ag composite film with 2.4 at.% Ag. The possibility of having the epitaxial growth of Ag within TiN were also confirmed by designing a TiN/Ag multilayered film with an Ag layer thickness of ∼3 nm.
- Design and development of porous CoCrFeNiMn high entropy alloy Cantor alloy with outstanding electrochemical propertiesPublication . Abid, Talha; Akram, M. Aftab; Karim, M. Ramzan Abdul; Fernandes, Filipe; Fernandes, Filipe; Zafar, Muhammad Farooq; Yaqoob, KhurramCoCrFeNiMn high entropy alloys are among the most well-studied high entropy alloys that exhibit reasonable strength and outstanding ductility. In the present study, porous CoCrFeNiMn foams have been developed by the addition of copper in the base high entropy alloy by arc melting followed by its removal through an electrochemical dealloying process. Microstructure characterization of the as-cast samples confirmed limited solubility of copper in the matrix while the majority of the copper was found to segregate to interdendritic areas. Removal of copper from the interdendritic areas was successfully carried out by an electrochemical dealloying process which resulted in the development of foams with interconnected porosity. CoCrFeNiMn foams with different levels of porosities were successfully developed by varying the amount of added copper in the base HEA and its removal by a dealloying process. The electrochemical performance of the developed foams was assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). One of the developed foams was found to exhibit an areal capacitance of 1.56 F cm 2 at 2 mA cm 2 which is more than 2x times higher than the value reported for recently developed porous AlCoCrFeNi high entropy foam. Developed foam, besides showing excellent values of areal capacitance, demonstrated capacitance retention of 114.6% after 5000 cycles at 8 mA cm 2. The excellent electrochemical performance of the developed high entropy foams exhibits their potential to be used as electrode materials for supercapacitor applications and was attributed to the insertion of interconnected porosity in the base HEA.
- Design and magnetron sputtering of nanomultilayered W2N/Ag-SiNx films: Microstructural insights and optimized self-lubricant properties from room temperature to 500 ◦CPublication . Luan, Jing; Kong, Fanlin; Evaristo, Manuel; Fernandes, Filipe; Zhou, Yazhou; Cavaleiro, Albano; Ju, Hongbo; Fernandes, FilipeNovel multilayered films were engineered by integrating W2N and Ag-SiNx layers in a multilayer structure to obtain improved hardness and tribological properties. The films were fabricated by alternating magnetron sputtering, depositing 40 nm layers of W2N with varying thickness of Ag-SiNx layers varying in thickness from 4 to 20 nm. The effect of the increase thickness of the Ag-SiNx layers in the films microstructure and tribological properties were accessed. Tribological experiments were conducted at room temperature (RT), 500 °C, and RT-500 °C cycling conditions. The results revealed the production of a multilayered structure comprising single fcc-W2N layers interspersed with dual-phase layers consisting of fcc-Ag and amorphous SiNx phases. Tribological results indicated an improvement in the tribological performance with increase thickness of the Ag-SiNx layer up to 12 nm. The tribo-synergistic/combined action of both W2N and Ag-SiNx layers, along with the presence of layered lubricant tribo-phases of WO3 and Ag2WO4, showcased the pivot role in reducing friction and enhancing wear resistance. The optimized multilayered film, featuring a 12 nm Ag-SiNx layer, demonstrated exceptional tribological properties under temperature-cycling from RT to 500 °C.
- Effect of binder on oxidation properties of tungsten carbides: A review by a Conceptual Classification ApproachPublication . Fathipour, Zahra; Hadi, Morteza; Maleki, Mohammad Reza; Fernandes, Filipe; Fernandes, FilipeThis study presents a conceptual classification scheme to review the literature on improving the oxidation resistance of tungsten carbide by modifying the binder. The first parts of the article are dedicated to the specification of the databases, the search method, and the description of the criteria chosen to classify the articles. Then, the data collected are presented in statistical graphs according to the proposed classification scheme. The data analyzed show that most of the significant improvements in oxidation resistance are achieved with advanced production processes, especially HIP and SPS, which eliminate porosity to a very high degree. In addition, statistical studies showed that the use of new replacement binders, Ni3Al, Fe–based alloys, FeAl, and Al2O3, improved the oxidation properties in 75–100% of cases. Meanwhile, the use of high–entropy alloys (HEAs) as cermet binders may be the subject of future research for oxidation, given the recently published results of good mechanical properties.
- Effect of carburizing time treatment on microstructure and mechanical properties of low alloy gear steelsPublication . Boumediri, Haithem; Touati, Sofiane; Debbah, Younes; Selami, Salim; Chitour, Mourad; Khelifa, Mansouri; Kahaleras, Mohamed said; Boumediri, Khaled; Zemmouri, Amina; Athmani, Moussa; Fernandes, FilipeGas carburizing significantly enhances the surface properties of low-alloy gear steels, resulting in superior micro-hardness, layer thickness, carbon content, and overall mechanical properties. Unlike other thermochemical processes such as nitriding and carbonitriding, which have limitations in core properties and hardening depth, gas carburizing offers unmatched surface hardness, wear resistance, and mechanical strength. This makes it ideal for demanding applications in the automotive, aerospace, and manufacturing industries. In this research, samples were gas-carburized for 4, 6, or 8 h. The results showed significant improvements: micro-hardness increased from approximately 140 HV to over 819 HV, and the surface layer thickness grew by more than 41%, from 1166 μm to 1576 μm. Additionally, the carbon content in the surface layer increased by over 450%, reaching up to 0.94 wt%. Clear correlations were observed between the duration of heating and the mechanical properties. Longer heating times, particularly after 8 h, raised ultimate tensile strength from 427.29 MPa to 778.33 MPa, while simultaneously decreasing elongation from 26.07% to 2.88% and resilience from 180 J cm−2 to 6.66 J cm−2. This optimization not only enhances surface hardness and durability but also improves key mechanical properties such as tensile strength, stiffness, resilience, and overall mechanical performance.
- 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.
- Exploring tribological characteristics of ZrN-MoSN composite films fabricated via RF magnetron sputtering: Insights from microstructure and performance analysisPublication . Luan, Jing; Lu, Hongying; Xu, Junhua; Fernandes, Filipe; Fernandes, Filipe; Evaristo, Manuel; Ma, Bingyang; Xie, Fuxiang; Cavaleiro, Albano; Ju, HongboAchieving the stringent demands of sustainable tribological industrial applications poses a significant challenge, particular in optimizing the self-lubricant performance of nitride-based films. This paper tackled this challenge by designing and depositing a series of ZrN-MoSN composite films with varying (Mo + S)/Zr ratios, employing RF magnetron sputtering, aimed to enhance the tribological properties through utilizing the high loading capacity of the ZrN matrix and the exceptional self-lubricating attributes of Mo-S-N additives. After conducting thorough investigations on the microstructure, and tribological properties, the results revealed that the dense columnar structured ZrN-MoSN composite films displayed a polycrystalline composition comprising fcc-ZrN and hcp-MoS2 phases, intertwined with amorphous phases of Mo(SN)x and MoS2(N2). (Mo + S)/Zr ratios below 1.08 exhibited a minor impact on the room temperature (RT) tribological properties, while higher ratios led to degradation on RT average friction coefficient (COF) and wear rate (WR). However, the synergistic effect of ZrN matrix and the tribo-phases of layered MoO3 and hard ZrO2 contributed to the significant enhanced 500 °C tribological properties, particularly with an optimized (Mo + S)/Zr ratio of 0.43.