Percorrer por autor "Faia, Pedro"
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- 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.
- Electrical properties and thermistor behavior of TiAlN thin films deposited by combinatorial sputteringPublication . Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, Pedro; Bondarchuk, Oleksandr; Fernandes, FilipeA combinatorial deposition was performed by direct current magnetron sputtering (DCMS) to develop Ti1-xAlxN thin films with different Ti/Al ratios and investigate the electrical response to temperature. The crystal structure as a function of the x was studied by X-ray diffraction, and sheet resistance response was measured up to 200 ◦C. From x = 0.16 to x = 0.56, the film shows an fcc phase with Al in solid solution in the TiN matrix, whilst, from x ≥ 0.69, a mixture of hcp (AlN) and fcc phases is observed. A negative temperature coefficient (NTC) thermistor behavior was found from x = 0.21 onwards, and a maximum sensitivity β of 1600 K was observed for x = 0.56 and 0.69. One fcc sample (x = 0.46) was selected to analyze the chemical states by X-ray photoelectron spectroscopy and the impedance behavior with the temperature by electrical impedance spectroscopy. The crystal structure, bond states and impedance analysis were compared with an AlN thin film. It is concluded that the conduction mechanism for x = 0.46 is based upon electron hopping, and the effect of the grain boundary is more relevant than the grain at low temperatures. We demonstrate that it is possible to use TiAlN as an NTC-thermistor with different crystal structures and chemical compositions.
- 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.
- Real-time temperature monitoring during titanium alloy machining with cutting tools integrating novel thin-film sensorsPublication . Fernandes, Filipe; Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, PedroThis study explores the integration of titanium aluminum nitride (TiAlN) and zirconium aluminum nitride (ZrAlN) thin-film sensors into cutting tools for real-time temperature monitoring during machining of Ti6Al4V titanium alloy. These sensors, integrated into a multilayer coating for electrical and wear shielding, were deposited directly onto the tool surfaces and calibrated for temperatures up to 750 °C. Due to the integration into the multilayer coating, the sensors exhibit different β sensitivities across the temperature range, ranging from 108 to 825 K for TiAlN and from 950 to 6681 K for ZrAlN. The cutting tests conducted under various cutting conditions, such as cutting speed, feed rate, depth of cut, and cooling, revealed the influence of these parameters on the cutting temperature. Our findings indicate that the sensor position in the tool’s rake face is fundamental for measuring the cutting temperature. The study introduces an innovative tool connector for integration and signal retrieval of the cutting tool in a “plug-and-play” fashion, compatible with industry standards. Additionally, implementing wireless data transmission for real-time and in-situ temperature monitoring offers a pathway for integrating smart cutting tools into modern manufacturing environments, aligning with Industry 4.0.
- Zirconium aluminum nitride thin films for temperature sensing applicationsPublication . Fernandes, Filipe; Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, Pedro; Alves, Cristiana F. Almeida; Carbo-Argibay, Enrique; Ferreira, Paulo J.This study explores the development and characterization of zirconium aluminum nitride (ZrAlN) thin films produced via magnetron sputtering for temperature sensing applications. The sensor film is integrated into a fully nitride multilayer coating and designed to work in harsh environments. The ZrAlN demonstrated stable semiconductor behavior up to 750 °C, making it suitable for high-temperature thermistors, with a β value of approximately 850 K after signal stabilization. Detailed structural characterization confirmed a mixed-phase structure of poorly crystalline cubic ZrN and orthorhombic Zr3N4. This structure is believed to be responsible for the high resistivity of 8.0 × 105 µΩ·cm observed in Zr1-xAlxN with x = 0.3. The examination of Zr0.7Al0.3N integrated into the multilayer coating revealed a columnar morphology with diffuse nanolayers, alternating between aluminum-rich and aluminum-poor zones, caused by the two-fold rotational deposition. The sensor coating was further tested on a cutting tool substrate, with the Zr0.7Al0.3N layer exhibiting a sensitivity of 800 K and demonstrating effective temperature measurements up to 400 °C. The Zr0.7Al0.3N layer inserted in a nitride-based multilayer coating, combined with Arduino® for signal acquisition, resulted in a measured error of approximately 7 %. The setup presented the potential for integration into manufacturing environments aligned with Industry 4.0.