CoatMat

The first stages of the development of a catalytic trap for diesel particulate removal from vehicle exhaust gases are addressed, ranging from catalytic trap preparation (a ceramic foam is deposited with catalysts, suitable for soot combustion, based on mixtures of KCl and different vanadates) to catalytic trap testing in a specific pilot plant (an acetylene burner is used to produce a soot laden flue gas which is then treated by the apparatus while the pressure drop buildup throughout the trap and the trap collection efficiency is measured).

This paper concerns the development of catalytic traps for diesel particulate removal from the exhaust gases of light-duty vehicles. The studied traps were realised with ceramic (ZTA and mullite) foam structure, on which two different kinds of catalysts, one based on caesium metavanadates and the other on pyrovanadates, were deposited.

The oxidation behaviour of a FeCrAl alloy with little rare earth content (Y = 0.01 wt.%) was investigated. Specimens of this alloy were submitted to long-term oxidation treatments (up to 30 days) at 900 and 1200 °C, under gaseous atmospheres containing 21, 10 and 2 vol.% of O2. The weight gain for unit area was measured vs. oxidation time. The alumina scale growth was found to occur, at least during the first days of treatment, according to Wagner's parabolic law. Afterwards, the layer rate growth decreases down to that expected on the basis of this law.

The thermal stability of a 2D-Nicalon/C/SiC composite was studied through the variation of both mechanical properties and microstructure occurring during heat treating. The composite was processed by infiltration of SiC preforms according to SICFILL® method. The material toughness was enhanced by a carbon interphase put between the fibers and the matrix. In order to improve the thermal stability a CVI layer was deposited on the carbon interphase and the specimen surfaces were CVD covered by an external SiC seal coating about 165 μm thick.

Three kinds of turbine blades (made by casting Renè 77, Renè 80 and CMSX-4 nickel based alloys) were submitted to an above pack aluminizing treatment. The suitability of this surface coating for preventing high temperature oxidation and hot salt corrosion was investigated. Oxidation tests were performed in air at 1050°C for 500 and 1000 h; salt corrosion at 950°C was studied by using a NaCl+Na2SO4 mixture. The microstructure of aluminized blades before and after these tests was compared by X-ray diffraction, scanning electron microscopy and electron probe microanalysis.

The preparation of highly pure MgB2 powder is here presented. The two steps preparation method, together with an ad hoc projected reactor, permits us to obtain the desired stoichiometric phase without MgO impurities and other degradation compounds, which depress the superconductive properties. The formation of a liquid phase during the first step of the preparation leads to small grain size particles. New techniques of film preparation (Electrophoretic deposition) have also been approached.

A wide series of carbon nanostructures (ranging from fullerenes, through carbon nanotubes, up to carbon nanofibers) promise to change several fields in material science, but a real industrial implementation depends on their availability at reasonable prices with affordable and reproducible degrees of purity. In this study we propose simple instrumental approaches to efficiently characterize different commercial samples, particularly for qualitative evaluation of impurities, the discrimination of their respective spectral features and, when possible, for quantitative determination.

Similarly to the activity described in Part I, the PPO-based composites were studied in view of their pre-screening as potential candidates in innovative ablative shields. In this case equiaxial, oxide and non-oxide powders, precisely magnesium aluminate spinel, aluminum hydroxide (boehmite), δ- and α-alumina, silicon carbide, silicon nitride and molybdenum disilicide, were used as fillers. Nanometric and micrometric α-alumina and silicon carbide powders were exploited to investigate the effect of the particle size. The alumina-based composites presented the most promising behavior.

An ablative Thermal Protection System (TPS) is a sacrificial shield able to insulate aerospace vehicles during atmospheric re-entry. In this paper, PPO-based composites were investigated in view of their potential exploitation as innovative ablative TPS. Their ability to degrade undergoing endothermic reactions and yielding a char layer was evaluated by means of thermal analyses and cone calorimeter tests. This first part discusses composites containing layered particles, in particular a cationically modified clay, a hydrotalcite and a sepiolite.