Istituto Nazionale di Ricerca Metrologica
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Passive daytime radiative cooling
Get PDFWith average global temperatures constantly increasing, the emerging field of passive daytime radiative cooling holds promise to alleviate our growing cooling needs and protect the environment by providing us with electricity-free cooling power. Here, we briefly revise the principles behind this rapidly expanding field, its main material platforms and implementations, and its outstanding challenges in terms of scalability and durability against weathering agents
Magnetic Behavior of NO Fe-Si Sheets Under Tensile and Compressive Stresses
Get PDFThe stress dependence of the magnetic properties of non-oriented (NO) Fe Si steel sheets has been investigated by measurement and analysis of hysteresis loop, magnetization curve, and energy losses taken at different peak polarization values J p (0.5 1.5 T) between dc and f = 400 Hz. The salient feature of the material response to the stress lies in the monotonic deterioration of the soft magnetic properties, across the whole (J p -f) domain, on passing from the maximum tensile stress (σ = +30 MPa) to the maximum compression (σ = -30 MPa). This is understood in terms of stress-induced redistribution of the domains between easy axes, making magnetic hardening by compression directly related to unfavorably directed domains and 90° domain-wall-mediated magnetization transitions. The loss decomposition is carried out across the whole investigated frequency range, taking into account the skin effect at the highest frequencies. Quasi-static and dynamic losses follow similar behaviors, both monotonically increasing on passing from the tensile to the compressive stress limits, according to the theoretically expected relationship existing between the hysteresis and the excess loss components
Light-Controlled Magnetic Properties: An Energy-Efficient Opto-Mechanical Control over Magnetic Films by Liquid Crystalline Networks
Get PDFMagnetostrictive materials are essential components in sensors, actuators, and energy-storage devices due to their ability to convert mechanical stress into changes in magnetic properties and vice-versa. However, their operation typically requires physical contact to apply stress or relies on magnetic field sources to control magnetic properties. This poses significant limitations to devices miniaturization and their integration into contactless technologies. This work reports on an approach that overcomes these limitations by using light to transfer mechanical stress to a magnetostrictive device, thereby achieving non-contact and reversible opto-mechanical control of its magnetic and electrical properties. The proposed solution combines a magnetostrictive Fe70Ga30 thin film with a photo-responsive Liquid Crystalline Network (LCN). Magnetic properties are modulated by changing the light wavelength and illumination time. Remarkably, the stable shape change of the LCN induced by ultraviolet (UV) light leads to the retention of magnetic properties even after the light is switched off, resulting in a magnetic memory effect with an energy consumption advantage over the use of conventional magnetic field applicators. The memory effect is erased by visible light, which releases the mechanical stress in the photoresponsive layer. Therefore, this new composite material creates a fully reconfigurable magnetic system controlled by light.Control on the magnetic properties and resistance of a FeGa thin film is obtained by coupling it with a photoresponsive Liquid Crystalline Network. The photo-induced stress of the polymeric substrate is able to efficiently modulate the properties of the metallic layer in a reversible way. imag
Static, continuous and dynamic calibration of force transducers: A comparative study on a low-force strain-gauge measuring device
Get PDFCurrent ISO 376 standard focuses on static calibration of force transducers, overlooking time and frequency influences, crucial in real-world applications such as automotive, aerospace, and healthcare, where mechanical and materials testing is essential for product quality and safety. As a result, novel calibration guidelines have been proposed to extend calibration to continuous and dynamic loading conditions. The paper examines the calibration results of a 200 N high-precision strain-gauge force transducer under static, continuous, and dynamic conditions. While sensitivities across these conditions are generally compatible, uncertainties in continuous and dynamic calibrations are notably higher, which could impact material testing and related applications. If continuous and dynamic sensitivity uncertainties dropped to the static uncertainty level, compatibility would be compromised because of significant differences between the three. It's unclear whether these discrepancies arise mainly from the intrinsic characteristics of the transducer in continuous dynamic conditions or from the inability to reach the transducer capacity force values during dynamic calibration
Relating laser powder bed fusion process parameters to (micro)structure and to soft magnetic behaviour in a Fe-based bulk metallic glass
Get PDFThis work aims to establish fundamental processing-(micro)structure-property links in a commercial Fe-based Kuamet6B2 bulk metallic glass (BMG) processed by laser powder bed fusion (LPBF). With that purpose, amorphous powders were processed using a pulsed-wave system and a simple meander strategy. The laser power, the scan speed, and the hatch distance were varied over wide intervals within the conduction regime. The processability window leading to samples with good dimensional accuracy and mechanical stability was determined. Within this window, the manufactured samples were crystalline/amorphous composites and the crystalline regions were formed by equiaxed ultrafine and nanograins with random orientations. Processing parameters yielding the densest prints caused severe crystallization while, conversely, parameter sets allowing the material to retain a high amorphous fraction led to significant lack-of-fusion defects and residual cracking along directions perpendicular to crystalline/amorphous interfaces. Comparatively, for a fixed hatch distance, the scanning speed had a stronger effect than the laser power in the resulting amorphous fraction due to its stronger influence on the melt pool size and, in turn, on the corresponding HAZ volume. The saturation magnetization and the coercive field were inversely related to the amorphous fraction. This work allows to derive fundamental guidelines for the successful additive manufacturing of soft magnetic Fe-based bulk metallic glasses (BMGs) by laser powder bed fusion (LPBF)
The Absolute Gravity Reference Network of Italy
Get PDFThe project for realizing the reference network for absolute gravity in the Italian area is presented. This fundamental infrastructure is the general frame for all the scientific and technological activities related to the gravity field in Italy. The project is in line with the actions promoted by the International Association of Geodesy that during its 2015 General Assembly approved a resolution on the establishment of the new global gravity network the so-called International Terrestrial Gravity Reference System/Frame that will replace IGSN71.The selection of the absolute gravity station sites in Italy has been performed either taking into account the existing absolute gravity stations and to have a homogeneous distribution of points. An initial set of 30 stations has been defined over the peninsular part of Italy and the two islands of Sicily and Sardinia. Particularly, the GGOS core station of Matera (the Agenzia Spaziale Italiana Center for Space Geodesy "Bepi" Colombo) is one of the network points as required in the documents of the GGOS-Bureau of Networks and Observations. Thus, this station will provide one link between the Italian national absolute gravity network and the GGOS observation system of IAG.The project is now ongoing and will close at the beginning of 2025.As required by the international standards on gravity measurements (https://www.bipm.org/documents/20126/41442296/CCM++IAG+Strategy+for+Metrology+in+Absolute+Gravimetry/7f9bc651-a2b6-08cc-7bba-f63b0a7e9765), the absolute gravimeters used in the measurements have been compared with absolute gravimeters that participated into international comparison campaigns in order to ensure the measurements traceability.Furthermore, absolute gravity measurements have been supplemented with direct measurements of the local value of the vertical gravity gradient, in order to reduce to the ground reference level the absolute values measured by different instruments at different heights. The gravity field campaigns will be assisted by topographic survey campaigns. This will allow a precise georeferencing (of the order of 12 cm) of the gravity stations that will be so framed to the current ITRF.The collected data will be then validated and reduced following the internationally accepted standards and finally published through a dedicate web page of the project. These data will also be sent for storage to the absolute gravity database maintained by the Bureau Gravimétrique International/Bundesamt fuer Kartographie und Geodaesie where the absolute gravity data that will contribute to the new global absolute gravity reference system are collected
Nanostructured Cu/Zn/Al-based oxide as a new sensing material for NO2 detection
No full textThe gas sensing properties of a ternary mixed-metal oxide (CuO/ZnO/Al2O3, CZA) are here reported. The CZA-based powder was prepared by co-precipitation synthesis technique. Then, the sensing material was screen-printed onto alumina substrates with interdigitated platinum electrodes and calcined at 350 °C for 1 h. The sensors were first tested under 25 ppm NO2 at different temperatures, ranging between 24 up to 200 °C. The best compromise between the sensor response and the recovery times was achieved at 100 °C. Then, the investigated concentration range was varied from 250 ppb up to 25 ppm and a maximum response of about 95 % was measured under 25 ppm of the target gas. Response times were reasonably fast while, on the contrary, recovery times were quite long. In addition, the CZA sensor was also able to detect from 3 up to 300 ppm of NH3 at a working temperature of 200 °C. Interferences were also studied with NO2-humid air and in the presence of CO2-dried gas
3D GPU-based implementation of the contrast source inversion for breast lesion detection
No full textMicrofluidic Detection of SPIONs and Co-Ferrite Ferrofluid Using Amorphous Wire Magneto-Impedance Sensor
Get PDFThe detection of magnetic nanoparticles in a liquid medium and the quantification of their concentration have the potential to improve the efficiency of several relevant applications in different fields, including medicine, environmental remediation, and mechanical engineering. To this end, sensors based on the magneto-impedance effect have attracted much attention due to their high sensitivity to the stray magnetic field generated by magnetic nanoparticles, their simple fabrication process, and their relatively low cost. To improve the sensitivity of these sensors, a multidisciplinary approach is required to study a wide range of soft magnetic materials as sensing elements and to customize the magnetic properties of nanoparticles. The combination of magneto-impedance sensors with ad hoc microfluidic systems favors the design of integrated portable devices with high specificity towards magnetic ferrofluids, allowing the use of very small sample volumes and making measurements faster and more reliable. In this work, a magneto-impedance sensor based on an amorphous Fe73.5Nb3Cu1Si13.5B9 wire as the sensing element is integrated into a customized millifluidic chip. The sensor detects the presence of magnetic nanoparticles in the ferrofluid and distinguishes the different stray fields generated by single-domain superparamagnetic iron oxide nanoparticles or magnetically blocked Co-ferrite nanoparticles