High concentration Yb-Er co-doped multi-component phosphate glasses for compact eye-safe optical amplifiers

In recent years, the increasing need of airborne LIght Detection And Ranging (LIDAR) systems for environmental monitoring and surveillance has noticeably boosted the development of compact eye-safe optical amplifiers. In this scenario, multi-component phosphate glasses can be regarded as ideal candidate materials as they can be doped with a large amount of rare-earth (RE) ions without clustering, thus enabling the realization of few-cm long optical amplifier sections featured by high optical gain per unit length. In this work we will report the ongoing activities and the recent results obtained by our research group on the design, processing and characterization of a series of Yb-Er co-doped phosphate glasses to be used as active materials for the core of a waveguide amplifier. The physical, thermo-mechanical, optical and spectroscopic properties of the prepared glasses have been thoroughly investigated

Viscoelastic Characterization and Degradation Stability Investigation of Poly(butylene-adipate-co-terephthalate) - Calcium-Phosphate Glass Composites

In this work new biodegradable composite materials based on poly(butylene-adipate-co-terephthalate) (PBAT) reinforced with water-soluble calcium-phosphate glass (CPG) microparticles at different filler concentration (0, 4, 10, 20 and 40 wt%) were characterized by dynamic-mechanical analysis (DMA), aging and fragmentation tests. DMA results showed increasing storage modulus (E') values with the filler content, without a significant modification of the glass transition temperature (Tg), translating in a reinforcing effect of the filler particles with good interphase adhesion. The creep compliance decreased with the increase of the CPG content, confirming a greater resistance of the composites to deformation under constant stress. The stability to weathering agents and the degree of fragmentation in laboratory-scale composting conditions were also tested, obtaining a higher sensitivity to degradation of the PBAT-based composites with the increase of CPG content. Overall, the addition of CPG particles in a PBAT matrix produced stiffer composites, with modulation of the properties based on the filler content, enhancing at the same time their degradation rate, making them a promising and more sustainable alternative to traditional polymers

Optical Quality Resorbable Calcium-Phosphate Glasses for Biophotonic Applications

Recently developed calcium-phosphate glass formulations are proposed in this chapter as a new class of materials for biomedical optics and photonics. The glasses have been designed and carefully prepared in our laboratory to be dissolvable in biological fluids while being optically transparent, mechanically reliable both in dry and humid environments, and suitable for both preform extrusion and fiber drawing. Optical fibers have been drawn from these glasses using our custom-made induction heated drawing tower and showed attenuation loss values from one to two orders of magnitude lower than the counterpart polymeric-based bioresorbable devices reported in literature. In addition, the optical fibers have been implanted in living rats for several weeks and no clinical signs of any adverse effect have been found. Results on the inscription and characterization of different types of fiber Bragg grating-based optical filters will be also shown, together with the demonstration of the suitability of the above-mentioned bioresorbable optical fibers for time-domain diffuse optical spectroscopy

Toward the fabrication of extruded microstructured bioresorbable phosphate glass optical fibers

The steps toward the fabrication of directly extruded microstructured fiber preforms made of a bioresorbable phosphate glass are herein presented, analyzing the features of the process from the glass synthesis to the manufacturing of the fiber. The realization of these fibers leverages on three main pillars: an optically transparent bioresorbable glass, its extrusion into a preform, and the fiber drawing. The glass has been designed and carefully prepared in our laboratory to be dissolvable in a biological fluid while being optically transparent and suitable for both preform extrusion and fiber drawing. To support the production of an optimized die for the preform extrusion, a simplified laminar flow model simulation has been employed. This model is intended as a tool for a fast and reliable way to catch the complex behavior of glass flow during each extrusion and can be regarded as an effective design guide for the dies to fulfill the specific needs for preform fabrication. After die optimization, extrusion of a capillary was realized, and a stacking of extruded tubes was drawn to produce a microstructured optical fiber made of bioresorbable phosphate glass

WILSON PLOT METHOD TO OBTAIN NUSSELT NUMBER FOR A PLATE HEAT EXCHANGER

Plate heat exchangers are devices commonly used in industry due to their high efficiency and ease cleaning. Although its first use was in food sector, nowadays this equipment can be found in most industrial segments, like chemistry and oil industry. Due the facility of fabrication, the corrugated gasket plate heat exchanger is amply utilized in those segments, however, its mathematical analysis present non-agreement between the authors, because of the different plate models and operation settings. Thus, the main objective of this work is to study the application of the Wilson-Plot method to analyze the thermal behavior of an elemental plate heat exchanger, and verify if the operation temperature has significant influence in the thermal behavior of the plate heat exchanger

Intermolecular interactions of substituted benzenes on multi-walled carbon nanotubes grafted on HPLC silica microspheres and interaction study through artificial neural networks

Purified multi-walled carbon nanotubes (MWCNTs) grafted onto silica microspheres by gamma-radiation were applied as a HPLC stationary phase for investigating the intermolecular interactions between MWCNTs and substituted benzenes. The synthetic route, simple and not requiring CNTs derivatization, involved no alteration of the nanotube original morphology and physical–chemical properties. The affinity of a set of substituted benzenes for the MWCNTs was studied by correlating the capacity factor (k′) of each probe to its physico-chemical characteristics (calculated by Density Functional Theory). The correlation was found through a theoretical approach based on feedforward neural networks. This strategy was adopted because today these calculations are easily affordable for small molecules (like the analytes), and many critical parameters needed are not known. This might increase the applicability of the proposed method to other cases of study. Moreover, it was seen that the normal linear fit does not provide a good model. The interaction on the MWCNT phase was compared to that of an octadecyl (C18) reversed phase, under the same elution conditions. Results from trained neural networks indicated that the main role in the interactions between the analytes and the stationary phases is due to dipole moment, polarizability and LUMO energy. As expected for the C18 stationary phase correlation, is due to dipole moment and polarizability, while for the MWCNT stationary phase primarily to LUMO energy followed by polarizability, evidence for a specific interaction between MWCNTs and analytes. The CNT-based hybrid material proved to be not only a chromatographic phase but also a useful tool to investigate the MWCNT-molecular interactions with variously substituted benzenes

Novel PBAT-Based Biocomposites Reinforced with Bioresorbable Phosphate Glass Microparticles

Biocomposites based on poly(butylene adipate terephthalate) (PBAT) and reinforced with micro-particles of inorganic biodegradable phosphate glass (PG) at 2, 10, and 40 wt% are prepared and characterized from a mechanical and morphological point of view. Scanning electron microscope (SEM) images show a good dispersion of the PG micro-grains, even at high concentrations, in the PBAT matrix, resulting in homogeneous composites. Tensile and dynamic-mechanical tests, respectively, indicate that Young's and storage moduli increase with PG concentration. The reinforcement of PBAT aims at modifying and tailoring the mechanical and viscoelastic properties of the material to expand its application field especially in the food and agricultural packaging sector, thanks to the similarity of PBAT performance with polyethylene

Design and manufacturing of a Nd-doped phosphate glass-based jewel

This paper reports the results of the designing, manufacturing and characterization of a jewel obtained by means of coupling the dogmas of industrial design to the analytical engineering approach. The key role in the design of the jewel was played by an in-house synthesized Neodymium (Nd)-doped phosphate glass, selected due to its easy handling and capability to change color according to the incident light wavelength. The glass core was covered by a metal alloy to mitigate its relatively high fragility and sensitivity to thermal shock and, at the same time, to highlight and preserve its beauty. The selection of the proper metal alloy, having thermo-mechanical properties compatible with those exhibited by the glass, was carried out by means of Ashby's maps, a powerful tool commonly adopted in the field of industrial design

Investigating femtosecond laser interaction with tellurite glass family

Focusing ultrafast laser pulses induce localized permanent structural modifications on the surface or in transparent materials, that are of particular interest for photonic applications. Among the materials of interest, the tellurite glass family is attractive for near-infrared and photonics applications due to its broad-transparency window and high optical nonlinearity. Here, we systematically investigate structural changes occurring in various TeO2-based glasses exposed to femtosecond laser with various laser parameters. Remarkably, in a regime where heat accumulated after successive pulses, we observed the formation of polarization-controlled self-organized patterns expanding well beyond the focal volume, suggesting the presence of an evanescent coupling mechanism enhancing the self-organization. In addition, our results, obtained with compositional elemental analysis coupled with Raman spectra suggest different ion migration mechanisms in the laser affected zone at the surface and inside the glass. The formation of crystalline tellurium (t-Te) from glass structural units due to photo-induced elemental dissociation was observed only at the surface. The formation of ultrathin layer of crystalline tellurium offers the possibility to explore structural transitions in two-dimensional (2D) glasses by observing changes in the short- and medium- range structural orders, induced by spatial confinement

Multifunctional bioresorbable phosphate glass optical fibers for theranostics

We report on the design and development of microstructured phosphate glass optical fibers for minimally invasive diagnosis and therapy. We discuss preliminary results of fiber drawing and characterization