Istituto Nazionale di Ricerca Metrologica
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Picosecond Laser Processing of Hierarchical Micro–Nanostructures on Titanium Alloy upon Pre‐ and Postanodization: Morphological, Structural, and Chemical Effects
No full textRecent publications indicate that the order of electrochemical anodization (before or after the laser processing step) plays an important role for the response of bone-forming osteoblasts—an effect that can be utilized for improving permanent dental or removable bone implants. For exploring these different surface functionalities, multimethod morphological, structural, and chemical characterizations are performed in combination with electrochemical pre- and postanodization for two different characteristic microspikes covered by nanometric laser-induced periodic surface structures on Ti–6Al–4V upon irradiation with near-infrared ps-laser pulses (1030 nm wavelength, ≈1 ps pulse duration, 67 and 80 kHz pulse repetition frequency) at two distinct sets of laser fluence and beam scanning parameters. This work involves morphological and topographical investigations by scanning electron microscopy and white light interference microscopy, structural material examinations via X-ray diffraction, and micro-Raman spectroscopy, as well as near-surface chemical analyses by X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The results allow to qualify the mean laser ablation depth, assess the spike geometry and surface roughness parameters, and provide new detailed insights into the near-surface oxidation that may affect the different cell growth behavior for pre- or postanodized medical implants.Recent publications indicate that the order of electrochemical anodization (before or after the laser processing step) plays an important role for the response of bone-forming osteoblasts—an effect that can be utilized for improving permanent dental or removable bone implants. For exploring these different surface functionalities, multimethod morphological, structural, and chemical characterizations are performed in combination with electrochemical pre- and postanodization for two different characteristic microspikes covered by nanometric laser-induced periodic surface structures on Ti–6Al–4V upon irradiation with near-infrared ps-laser pulses (1030 nm wavelength, ≈1 ps pulse duration, 67 and 80 kHz pulse repetition frequency) at two distinct sets of laser fluence and beam scanning parameters. This work involves morphological and topographical investigations by scanning electron microscopy and white light interference microscopy, structural material examinations via X-ray diffraction, and micro-Raman spectroscopy, as well as near-surface chemical analyses by X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The results allow to qualify the mean laser ablation depth, assess the spike geometry and surface roughness parameters, and provide new detailed insights into the near-surface oxidation that may affect the different cell growth behavior for pre- or postanodized medical implants
Ultrafast (≈10 GHz) mid-IR modulator based on ultrafast electrical switching of the light-matter coupling
No full textWe demonstrate a free-space amplitude modulator for mid-infrared radiation (λ ≈ 9.6 μm) that operates at room temperature up to at least 20 GHz (above the −3 dB cutoff frequency measured at 8.2 GHz). The device relies on the ultrafast transition between weak- and strong-coupling regimes induced by the variation of the applied bias voltage. Such transition induces a modulation of the device reflectivity. It is made of a semiconductor heterostructure enclosed in a judiciously designed array of metal-metal optical resonators, that—all-together—behave as an electrically tunable surface. At negative bias, it operates in the weak light-matter coupling regime. Upon application of an appropriate positive bias, the quantum wells populate with electrons, and the device transitions to the strong-coupling regime. The modulator transmission remains linear with input radio frequency power in the 0-9 dBm range. The increase in optical powers up to 25 mW exhibit a weak beginning of saturation a little bit below
Validation and traceability of miniaturized multi-parameter cluster radiosondes used for atmospheric observations
No full textIn this work we designed and developed a cluster of light expendable radiosondes that can float passively inside warm clouds to study their micro-physical processes. This involves the tracking of both saturated and unsaturated turbulent air parcels. The aim of this new kind of observation system is to obtain Lagrangian statistics of the intense turbulence inside warm clouds and of the lower intensity turbulence that is typical of the air surrounding such clouds. Each radiosonde in a cluster includes an electronic board, which is mounted onto a small, biodegradable balloon filled with a mixture of helium and air. The cluster is able to float inside clouds for a few hours and to measure air temperature, pressure, humidity and the associated position, velocity, acceleration and magnetic field readings of each radiosonde along their trajectory
CTS for Time Metrology - first experimental results at INRIM and possible perspectives for timing with muons
No full textBoundary conditions for micromagnetism with spin currents
No full textIn this paper we show how the spin current in insulating ferromagnets can be treated in the micromagnetic framework by generalizing the boundary conditions in order to allow for the transport of magnetic moment and energy at the interface with other spin carrying media. As specific examples we demonstrate the spin Hall torque and spin pumping effects for a ferromagnetic layer in contact with a spin Hall metallic layer. In particular we show how by this method we can reproduce the known literature result in the case of thin films and make predictive examples for thick ferromagnets
Traceability for AC Ripple Over DC Current
No full textDirect current (dc) is experiencing a new renaissance. The consolidated high-voltage direct current (HVdc), together with new medium voltage direct current (MVdc), and low-voltage direct current (LVdc) are more and more present in research and development projects. One of the relevant topics, associated with the usage of dc, is the ac ripple that unavoidably accompanies the dc signals. The interest in the measurement of this quantity is linked with the determination of the performance of dc energy meters for billing purposes. The on-line power quality (PQ) analysis, the verification of the capabilities of the filtering systems, and the accurate determination of losses associated with the transmission, distribution, and conversion of the electric energy by dc systems require accurate determination of the ac ripple. National metrology institutes (NMIs) provide traceability only for pure ac or pure dc current signals. To guarantee a high-quality standard for such measurements, the article proposes a novel methodology, named ALFO, for the traceable calibration of measuring systems with signals composed by dc with superimposed ac ripple. The calibration setup is based on a decoupling transformer (DeT) which has been specifically designed by a numerical tool. A detailed analysis and quantification of the systematic errors affecting the measurement and of uncertainty budget have been performed. The setup can calibrate current measuring systems up to 100 A (dc) with ac ripple up to 1% of the dc in the frequency range 300 Hz-150 kHz. Preliminary evaluation of the standard uncertainty, performed at maximum 40 A dc and 1 A ac up to 250 mu text{A} /A in the range of 300 Hz-150 kHz
Brain-inspired computing with self-assembled networks of nano-objects
No full textMajor efforts to reproduce functionalities and energy efficiency of the brain have been focused on the development of artificial neuromorphic systems based on crossbar arrays of memristive devices fabricated by top-down lithographic technologies. Although very powerful, this approach does not emulate the topology and the emergent behavior of biological neuronal circuits, where the principle of self-organization regulates both structure and function. In materia computing has been proposed as an alternative exploiting the complexity and collective phenomena originating from various classes of physical substrates composed of a large number of non-linear nanoscale junctions. Systems obtained by the self-assembling of nano-objects like nanoparticles and nanowires show spatio-temporal correlations in their electrical activity and functional synaptic connectivity with nonlinear dynamics. The development of design-less networks offers powerful brain-inspired computing capabilities and the possibility of investigating critical dynamics in complex adaptive systems. Here we review and discuss the relevant aspects concerning the fabrication, characterization, modeling, and implementation of networks of nanostructures for data processing and computing applications. Different nanoscale electrical conduction mechanisms and their influence on the meso- and macroscopic functional properties of the systems are considered. Criticality, avalanche effects, edge-of-chaos, emergent behavior, synaptic functionalities are discussed in detail together with applications for unconventional computing. Finally, we discuss the challenges related to the integration of nanostructured networks and with standard microelectronics architectures
Effect of Size and Morphology of Different ZnO Nanostructures on the Performance of Dye-Sensitized Solar Cells
Full text linkIn this study, the influence of zinc oxide (ZnO) nanostructures with various morphologies
on the performance of dye-sensitized solar cells (DSSCs) was investigated. Photo-electrodes were fabricated incorporating ZnO transport layers of distinct nanoscale morphologies—namely nanoparticles, microballs, spiky microballs, belts, and triangles—and their respective current–voltage characteristics were evaluated. It was observed that the DSSCs employing the triangular ZnO nanostructures, with a side length of approximately 30 nm, achieved the highest power conversion efficiency of 2.62%. This was closely followed by the DSSCs using spherical nanoparticles with an average diameter of approximately 20 nm, yielding an efficiency of 2.54%. In contrast, the efficiencies of DSSCs with microball and spiky microball ZnO nanostructures were significantly lower, measuring 0.31 and 1.79%, respectively. The reduction in efficiency for the microball-based DSSCs is attributed to the formation of micro-cracks within the thin film during the fabrication process. All DSSC configurations maintained a uniform active area of 4 mm2. Remarkably, the highest fill factor of 59.88% was recorded for DSSCs utilizing the triangular ZnO morphology, with the spherical nanoparticles attaining a marginally lower fill factor of 59.38%. This investigation corroborates the hypothesis that reduced particle size in the transport layer correlates with enhanced DSSC performance, which is further amplified when the nanoparticles possess pointed geometries that induce strong electric fields due to elevated charge concentrations
