Littérature scientifique sur le sujet « Glassceramic film »

Amorphous hydrogenated carbon thin films were deposited on Si and glassceramics substrates by reactive ion-plasma magnetron sputtering. Thin films were without (a-C:H) and with Ni nanoparticles (a-C:H:Ni). Measurement of absorption coefficient in 220-850 nm spectral range using spectrophotometer and following approximation applying of Tauc method shows that obtained a-C:H thin films material has near 3.6 eV optical band gap and confirmed that this material is amorphous semiconductor. Thin films with Ni nanoparticles have a high complex permittivity ε* and permeability μ* (ε′ ≈ 1000–10000, ε′′ ≈ 100–1500, μ′ ≈ 10–70, μ′′ ≈ 0.4-10). Some magnetic parameters of thin films were determined.

AbstractCarbon fibers reinforced lithium aluminosilicate matrix composites (Cf/LAS) were prepared by slurry infiltration combined with a hot press procedure. The friction, wear behavior, and wear mechanisms of Cf/LAS composites under dry sliding conditions were investigated. The results show that the coefficient of friction (COF) initially increased with the increase in carbon fiber content, and reached the maximum value of 0.20 for the 33%Cf/LAS composite. The COF increased sharply with increasing sample temperature from RT to 300 °C. The COF remained stable in the temperature range of 300–500 °C. The two wear mechanisms of LAS glassceramics are fatigue wear and abrasive wear. The Cf/LAS composites demonstrate slight spalling and shallow scratches. These results show that carbon fibers improve the mechanical properties and wear resistance of Cf/LAS composites.

The possibility to confine the light in optical planar structures represented the milestone for the development of integrated optical devices in different application areas, such as communications and sensing. In particular, rare-earth (RE) doped planar waveguides demonstrated to be an interesting solution in the realization of integrated optical lasers and amplifiers suitable for the generation/regeneration of the signal in metropolitan and local area networks. Nowadays, although these devices are commercially available, the major contribution of the research consists in discovering and developing better combinations of materials and fabrication processes, in order to reduce the costs and increase the performance of the aforesaid devices. In this context glass-ceramic waveguides, activated by RE ions, seem to fully respond to these requests. The aim of this paper is to offer a comprehensive review on the main results obtained in our Labs in the field of glassceramics. Fabrication and characterization of different silicate glass-ceramic thin films, doped with different percentages of RE ions, will be presented and discussed. The interesting results obtained make these systems quite promising for development of high performance integrated optical amplifiers and lasers.

Prosthetic crowns are made in accordance with the principles of clinical procedures while taking into account the rules of endurance, biocompatibility, and aesthetics. Depending on the biomaterial and manufacturing technology, crown frameworks are veneered with an appropriate set of ceramics with selected thermal expansion. The veneering layers responsible for tribological cooperation in occlusal contact should properly adhere to the framework. The aim of the research is to conduct the microscopic and EDS chemical analysis to evaluate the process of shaping veneering layers on frameworks produced using new digital technologies, i.e. the technology of milling and laser sintering. The research material consists of specimens produced in perpendicular cross-sections through the layered structures of metal-ceramic, ceramic-veneered glassceramic, and zirconium crowns. The microscopic examinations were carried out using the specimens and included the elemental EDS analysis performed on the surfaces and in certain points. The structures of metal and ceramic frameworks, ceramic veneering layers, and adhesive zones were determined.

In questa tesi presento il lavoro da me svolto durante il mio dottorato su film vetro-ceramici nanostrutturati contenenti ossido di gallio riguardo alla possibile uso di questa classe di materiali in geometria planare all’interno di dispositivi optoelettronici. Negli ultimi tre anni, le mie ricerche sono state rivolte alla comprensione della relazione fra la presenza delle nanostrutture – analizzate attraverso uno studio strutturale dettagliato grazie a diverse tecniche di microscopia e diffrazione in funzione delle condizioni di deposizioni e trattamenti successivi – e i meccanismi fisici di trasporto di carica e polarizzazione che accadono all’interno di film di ossidi-in-ossidi. Il materiale studiato è stato preparato tramite sputtering a radiofrequenze a partire da un precursore vetroso contenente ossidi di Li, Na, Si, Ga e Ge. Come conseguenza del processo di deposizione abbiamo ottenuto un materiale parzialmente cristallino con nanocristalli ricchi in Ga incorporati nel resto della matrice amorfa. Attraverso la microscopia a forza atomica, la riflessione dei raggi x, la diffrazione 2D dei raggi x, la dispersione 2D dei raggi x a piccoli angoli – anche usando luce di sincrotrone – abbiamo completamente caratterizzato i film nanostutturati a diverse scale di grandezza, da pochi nm a qualche micron. L’analisi dettagliata dei risultati mostra la formazione di molteplici nanocristalli anisotropi di spinello di ossido di gallio con dimensioni di 3 nm, che formano aggregati lenticolari di dimensioni maggiori con differenze significative nelle dimensioni nel piano e fuori dal piano. Come risultato dell’indagine di campioni trattati differentemente, lo studio ha inoltre mostrato che la distribuzione e la morfologia di nanostrutture può essere controllata dalle condizioni della deposizione, dalla durata e dalla temperatura del trattamento termico seguente. Partendo dalla conoscenza delle caratteristiche strutturali, l’attività di ricerca è stata indirizzata verso l’approfondita comprensione delle proprietà di trasporto di carica risultanti dalla natura nanostrutturata del materiale, inclusa la nanofase in Ga2O3 semiconduttore e la matrice ospite dielettrica. La risposta elettrica – analizzata con l’aiuto della spettroscopia di impedenza complessa – si è rivelata essere la risultante di molteplici meccanismi di trasporto e di carica dovuti a matrice e nanofase, incluse le interfacce interne. I dati suggeriscono che il trasporto di carica è supportato da una combinazione di meccanismi attivati termicamente per hopping e per effetto tunnel mediati da un percorso di percolazione costruito dalle caratteristiche nanostrutturali del materiale. Curiosamente, la risposta nel suo complesso ha fornito indizi preliminari di plasticità elettrica, rendendo i film sottili nano-vetroceramici dei promettenti candidati come sistemi chiave in dispositivi avanzati per memorie completamente inorganiche ossido-in-ossido ispirate al cervello umano.
In this thesis I present the work I have carried out during my PhD on Ga-oxide containing nanostructured glass-ceramic films as a potential breakthrough for the implementation of this class of material in planar geometry for applications in the field of optoelectronics. In the last three years, my investigations have been aimed at understanding the relationship between the occurrence of nanostructuring – analysed through a detailed structural studies by means of different microscopy and diffractometric techniques as a function of deposition conditions and post-deposition treatments – and the physical mechanisms of charge transport and polarization taking place in oxide-in-oxide films. The studied material was produced by RF sputtering deposition starting from a glass target of Li, Na, Si, Ga and Ge mixed oxide. As a consequence of the deposition process we have obtained partially crystallized material with Ga-rich nanocrystals incorporated in the remaining amorphous matrix. Through atomic force microscopy, x-ray reflectivity, 2D-x-ray diffraction, 2D-small angle x-ray scattering - also employing synchrotron radiation facilities - we have fully characterized the nanostructured films at different length scales, from few nm to few microns. The detailed analysis of the results shows the formation of multiple anisotropic spinel Ga-oxide nanocrystals with size of about 3 nm, forming larger lenticular aggregates with significant differences between the in-plane and the out-of-plane dimensions. As a result of the investigation of differently treated samples, the study also shows that size distribution and morphology of the nanostructures can be controlled by deposition conditions, duration and temperature of post-deposition thermal treatments. Starting from the knowledge of the structural features, the research activity has been directed to the deep understanding of the charge transport properties resulting from the nanostructured nature of the material, including the Ga2O3 semiconductor nanophase and the dielectric host matrix. The electrical response – analysed with the aid of complex impedance spectroscopy – turns out to be the results of multiple contributions to transport and charging mechanisms by the matrix and the nanophase, including the effects of the internal interfaces. The data suggest that the charge transport is sustained by a combination of thermally activated hopping and tunnelling mechanisms mediated by the percolation path built up by the nanostructured features of the material. Interestingly, the overall response gives preliminary evidences of electrical plasticity, making nano-glassceramic thin films potential candidates as key systems in advanced devices for brain-inspired oxide-in-oxide fully inorganic memories.