CeraMat

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.

In the present work, a new humidity sensor based on nanostructured hematite deposited by a wet chemical route on a low-cost natural inorganic phylosilicate (sepiolite) powder was obtained. The nanometric character of these particles has been evaluated by X-ray diffraction, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) and transmission electron microscopy.

A screen-printed thick film was developed to be overlapped to a gas sensing device for preserving it from contamination and degradation occurring in hostile environments, and also for improving its selectivity to a single pollutant gas when exposed to a complex atmosphere. This protective layer incorporated Al2O3 doped with Cs or Ba oxides as a catalyst material for eliminating gaseous interfering species, precisely CO2, to improve sensor response to CO.

A modified gel casting procedure based on a natural gelatin for food industry and commercial polyethylene spheres as pore formers was successfully exploited to produce dense and porous ceramic bodies made of yttria stabilized tetragonal zirconia polycrystal (Y-TZP). Vickers and Knoop microhardness, elastic modulus and fracture toughness measurements on dense samples obtained by experimental investigation closely matched results found in the literature for similar materials.

Dense and cellular ceramics were produced from yttria partially stabilized zirconia powders by gel-casting, using agar as a gelling agent and polyethylene spheres (125–300 μm diameter) as volatile pore forming agent to create 50–65 vol.% spherical macropores, uniformly distributed in a microporous matrix. The mechanical properties of both dense and porous samples were investigated at the microscale by nanoindentation testing.