Papers by Author: Monica Ferraris

Abstract: Bacterial issues in ophthalmic applications, with particular reference to postoperative infection of ocular implants, cause significant problems that often require additional, stressful and expensive treatments for the patients. In this work we applied silver-containing antibacterial costings on two kinds of polymeric ocular devices, i.e. silicone scleral buckles for retinal detachment surgery and poly(methyl methacrylate) artificial eyes for enucleated patients. The coatings (thickness around 50 nm), constituted by silver nanoclusters embedded in a silica matrix, were produced by RF co-sputtering and investigated by SEM and EDS. The antibacterial effect of the coating was confirmed by the in vitro formation of an inhibition halo against Staphylococcus aureus, which is one of the most common pathogens involved in ocular infections. The approach proposed in this study for treating implant-related ocular infections can have a significant impact in the field of ophthalmic biomaterials, suggesting a valuable alternative to the administration of antibiotics that may become ineffective towards resistant bacterial strains.

Abstract: Microwave has been applied to ignite the Self-propagating High-temperature Synthesis (SHS) of compacted Ni-Al mixtures, having 1:1 atomic ratio, in order to join Chemical Vapor Deposition (CVD) SiC ceramics and SiC/SiC composites. The average joint thickness of CVD SiC joint is about 200 μm and the Coefficient of Thermal Expansion (CTE) mismatch between CVD SiC and Ni-Al intermetallic compounds results in a interface bond strength inferior to that of the substrate and joining material; on the other hand, for the SiC/SiC composite joints, as a result of the porosity of SiC/SiC composites, the SHS products readily infiltrated into the pore spaces of the composite, leading to an increased porosity of the joint area and a better lower interface than the upper one. The mechanical strength of the joints has been evaluated by Single-Lap (SL) shear test at room temperature; neither of the ceramic joints nor the composites joint gave satisfactory results, but the ceramic joints reaching a maximum shear strength value of 56MPa exhibited a positive aspect for further experiments.

Abstract: Surface treatment before glass bonding is an important and critical issue for glass-based lab-on-chip fabrication. In the present article we verified five different activation methods for obtaining sound thermal assisted direct bonding (TADB) on glasses. Glass surface has been investigated by means of water contact angle, X-ray photoelectron spectroscopy (XPS). The optimum surface activation method for TADB on glasses was found to be H₂SO₄:H₂O₂ (3:1 by volume) followed by HNO₃. By using the TADB optimized activation method, the glass bonding strength higher than 32MPa was obtained with a glass the roughness of 50 nm.

Abstract: Microwaves (MW) at the ISM frequency of 2.45 GHz have been used to ignite the Combustion Synthesis (CS) of pressed ceramic and metallic powders mixtures, using a single-mode applicator (TE103). This experimental apparatus allows to study the separate effect of prevalent electric or magnetic field on the selective heating of the reactive powders compacts, while transferring energy and not heat before and after CS. Microwave activated combustion syntheses (MACS) of TiC-40 wt%Fe and FeAl intermetallic compounds were performed in the two different field configurations (maximum of the electric field (E) and maximum of magnetic field (H)) in order to investigate any possible difference in the reaction mechanism and in the final microstructure of the products. MACS in the maximum of E has also been applied to high temperature materials joining, with the application of a moderate pressure during the irradiation with electromagnetic waves, to promote adhesion and to reduce the newly formed compounds porosity.

Abstract: An overview of the last 16 years of activity on joining of advanced ceramics, glasses and ceramic matrix composites at Politecnico di Torino (Italy) will be presented. Results on thermal assisted direct bonding (TADB) of glasses for lab-on-chip devices, C/C composites to Cu-alloys for nuclear fusion components (ITER), SiC and SiC/SiC joints for nuclear components (fusion and fission), glass joining of foam glass, C/C joints for aerospace applications, ceramics to stainless steels for Solid Oxide Fuel Cells (SOFC), will be shown. Mechanical tests on joined components will be discussed, in particular, the results of an experimental campaign on carbon/carbon and ceramic joints tested in pure and apparent shear by nine different configurations.