PetroMat

The paper is focused on the processing of aluminum alloy chips using powder metallurgy. Chips obtained from recycled AlSi5Cu2 alloy were ball milled with the addition of silicon carbide powder with an average size of 2um. Mechanical alloying process was employed to obtain homogeneous composite powder. The effect of processing time (0 - 40h) on the homogeneity of the system was evaluated, as well as a detailed study of the microstructure of AlSi5Cu2 aluminum chips and SiC particles during MA was carried out.

The present work investigates the possibility of using powder metallurgy processing for producing a metal matrix composite. Materials were prepared from AlSi5Cu2 chips with reinforcement of 10, 15, 20 wt. % silicon carbide. Aluminum alloy chips were milled with SiC powder in a high-energy ball mill by 40 hours. Mechanical alloying process lead to obtain an uniform distribution of hard SiC particles in the metallic matrix and refine the grain size. The consolidation of composite powders was performed by vacuum hot pressing at 450°C, under pressure of 600 MPa by 10 min.

Recently, the screen printing has experimented a larger diffusion for producing microelectronic devices: resistors, conductors, humidity and gas sensors. Simplicity, versatility and low cost are the most significant reasons for its development and success. It has been applied in several high technology applications, because of its suitability to be printed on different materials; in microelectronics, various functional devices have been realised very competitive, if compared to massive materials.

Interactions between β-Al2O3 and a sodium aluminosilicate conductive glass, after thermal treatment at 900 °C, have been investigated on screen-printed gas sensors. Due to the high level of glass additions, the starting powder made of β/β″-alumina, underwent strong compositional modifications. SEM and TEM imaging, coupled with chemical analysis, evidenced the formation of nepheline and α-Al2O3 at the interface between β-Al2O3 and the glass.

Humidity sensing properties of α-Fe2O3 have been studied after doping with alkali and alkaline earth oxides precursors. Sensors were screen-printed and three different firing temperatures were investigated: 850, 900 and 950 °C. Formation of secondary phases has been investigated by means of 57Fe Mössbauer spectroscopy for K-doped hematite samples and by means of TG–DTA and XRD for all the compositions. Alkali and alkaline earth additions to hematite, except sodium ones, increased the opened porosity as evidenced by mercury porosimetry measurements onto pressed pellets.

In this paper we report the most significant results of a wide project which aimed to build up a sensor for the CO-detection with improved selectivity through catalytic activation.