Antonio Licciulli

Preparation and characterisation of titania/hydroxyapatite composite coatings obtained by sol-gel process

In the present work a titania network encapsulating a hydroxyapatite particulate phase is proposed as a bioceramic composite coating. The coating on a titanium substrate was produced starting from a sol containing a mixture of titania colloidal particles and hydroxyapatite submicron particles using the dip-coating technique. The microstructure, the morphology and the surface chemical composition of the coating were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. Adhesion tests were also performed. These analyses showed that the obtained coating was chemically clean, homogeneous, rough, porous, with a low thickness and well-defined phase composition as well as a good adhesion to the substrate.

Silver nanocrystals in silica by sol-gel processing

Abstract Silver nanocrystal doped silica films were prepared by the sol-gel process. The sol was prepared from 1:0.12:12:0.2:6:7 molar ratios of Si(OC2H5)4:AgNO3:H2O:HNO3:C3nH7OH:C4iH9OH. The glassy, highly transparent film with high dopant concentration (silver/silicon atomic ratio = 0.12) was successfully prepared by the dip-coating method. After drying in air at 60°C for 30 min, samples were heat-treated, in air, at 300, 350, 400, 450, 500 and 550°C using 30–100 min soaking periods for each step in a cumulative heating procedure. Measurements on the films were made by ultraviolet-visible and infrared spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry and transmission electron microscopy. Mechanisms of silver colloid formation in the densified silica matrix with respect to the thermal treatment are discussed. To understand the formation of silver nanocrystals from the silver silicate network, the corresponding doped bulk gel samples were analyzed by X-ray diffraction and differential scanning calorimetry.

Characterization of antibacterial silver coated yarns

Surface treatments of textile fibers and fabrics significantly increase their performances for specific biomedical applications. Nowadays, silver is the most used antibacterial agent with a number of advantages. Among them, it is worth to note the high degree of biocompatibility, an excellent resistance to sterilization conditions, antibacterial properties with respect to different bacteria associated with a long-term of antibacterial efficiency. However, there are only a few antibacterial fibres available, mainly synthetic with high production cost and limited effectiveness. Cotton yarns with antimicrobial properties are most suitable for wound healing applications and other medical treatments thanks to their excellent moisture absorbance while synthetic based fibres are most suitable for industrial applications such as automotive tapestry and air filters. The silver-coated fibers were developed applying an innovative and low cost silver deposition technique for natural and synthetic fibers or yarns. The structure and morphology of the silver nanoclusters on the fibers was observed by scanning electron microscopy (SEM), atomic force microscopy analysis (AFM) and XRD analysis, and quantitatively confirmed by thermogravimetric analysis (TGA) measurements. Good silver coating stability has been confirmed performing several industrial washing. Antimicrobial tests with Escherichia coli were performed.

The challenge of high-performance selective emitters for thermophotovoltaic applications

We present a brief survey of the most significant contributions to the study and the development of selective emitters for high-temperature applications. After a brief introduction and some necessary notes on definitions and experimental methods, this review presents the many different solutions proposed so far from the point of view of both the optimization of the functional properties of selective emitters and the fulfilment of the severe thermostructural requirements imposed by most high-temperature applications such as thermophotovoltaics.

A novel gas sensor based on SnO2/Os thin film for the detection of methane at low temperature

Abstract Osmium-doped tin oxide thin films were prepared by means of sol–gel technique. Their methane sensing properties were studied and compared to undoped SnO 2 thin films. The good sensitivity to methane at a low working temperature makes them very attracting active materials to be used in domestic CH 4 leak-detectors.

CO sensing properties of SnO2 thin films prepared by the sol-gel process

Abstract Undoped and Pd-doped SnO 2 -based thin film chemical sensors have been developed by means of the sol-gel technique. The prepared films were sensitive to CO gas as demonstrated by a change in electrical conductivity. The temperature dependence of the resistance change and response and recovery times have been measured. An improvement of the sensitivity and a lower operating temperature were observed in Pd-modified films.

Tin oxide-based gas sensors prepared by the sol–gel process

Abstract Sol–gel process was used to prepare pure and palladium-modified SnO2 thin films for gas sensors application. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques were used to analyse the structure, the chemical composition and the morphology of the prepared films. Pure tin oxide films have shown gas-sensing characteristics similar to most of the SnO2 films realized with other more expensive and more elaborate methods of preparation. Pd-doped SnO2 films have shown an improvement in the sensitivity, probably due to the Pd catalytic effect and to the induced microstructural changes.

AIR QUALITY MONITORING BY MEANS OF SOL-GEL INTEGRATED TIN OXIDE THIN FILMS

Abstract Sol–gel pure and Pd-doped SnO2 thin films on integrated substrates were developed to detect NO2 and CO. PdO particles are included in the film matrix and their presence enhances the CO gas sensitivity and response time. Measurements of electrical conductivity showed that these films have a response variation higher than 1000% for NO2 at temperatures in the range of about 200°C with a detection limit near 0.1 ppm, good for air quality monitoring. The response to CO is below 100% of the electrical variation but also in this case the sensor can detect very low concentration level.

Stereolitography of ceramic suspensions

The need of fast production of prototypes of complex shapes in very short time lead to the development in the last years of many additive rapid prototyping (RP) technologies for the production of single objects or of very limited series. The new fabrication concept allowed the construction of complex parts, starting from a 3D-CAD model, without using a mould. However, most of these additive processes produce polymeric objects and only recently the laser sintering of metal powders has been commercially introduced. In this work the production of ceramic objects by stereolithography is presented starting from the development of UV curable pre-ceramic suspensions for free form fabrication of alumino-silicate parts. The suspensions are characterized by 40%–50% by volume of powder content and by a reactivity and a viscosity compatible with their application in stereolithography. The ceramic green is built in a stereolithographic system operating with a He-Cd laser (325 nm). Then, the ceramic objects are obtained by pyrolisis of the organic binder and subsequent sintering of the green at 1600 °C. Finally, a characterisation of the mechanical properties and of the microstructure of the samples is presented.

Sol–gel derived pure and palladium activated tin oxide films for gas-sensing applications

Abstract Pure and Pd activated SnO 2 films on Corning 7059 substrates were prepared by the sol–gel dip coating method and used as active material in gas-sensing devices. SnCl 4 and Pd(CH 3 COO) 2 were used for tin and palladium sources. The SnO 2 sol was prepared from 1:3:9:4 molar ratios of SnCl 4 :H 2 O:C 3 n H 7 OH:C 4 i H 9 OH. The 5 equivalent wt% PdO-95% SnO 2 sol was prepared by mixing the required amount of Pd acetate to the pure SnO 2 sol. The dried (110°C/0.5 h) films were heat-treated in air at 600°C for 1 h. Pure SnO 2 films showed ethanol gas sensing characteristics similar to most of the commercially available tin oxide sensors. An improvement in the sensitivity towards ethanol gas at relatively low temperature was observed in case of Pd activated SnO 2 films. The improvement of sensing properties of Pd activated films was due to high surface roughness/surface area, oxygen vacancies and presence of PdO microcrystallites.