CeraMat

Silicon carbide multilayer composites containing short carbon fibres (Csf/SiC) were prepared by tape casting and pressureless sintering. C fibres were dispersed in solvents and then mixed with SiC slurry to make green Csf/SiC tape. Triton X-100 was found to be the best one for Toho Tenax HTC124 fibres (with water soluble coating) among BYK-163, BYK-410, BYK-2150, BYK-9076, BYK-9077 and Triton X-100 dispersants. Csf/SiC multilayer composites containing 5 vol.% fibre (mean fibre length of 3, 4.5, and 6 mm) were obtained.

Si–SiC–ZrB2 are produced by the reactive infiltration with molten silicon in porous SiC–C–ZrB2 preforms. It is observed that oxidized Si–SiC–ZrB2 ceramics present a layered structure composed of an outer layer of silica and a borosilicate glass intermediate layer with ZrO2 particles and the unoxidized bulk material. The graphs show that the passivation is very effective already after 5 min of oxidation. The thermograms do not vary significantly when the oxidation times are increased.

The reactive penetration of Al based alloys in massive silica glass and sintered preforms (made of silica, silica plus silicon carbide or silica plus aluminium nitride) was investigated. The reactions occurring during preform sintering and reactive metal penetration were preliminarily studied by Differential Thermal Analysis. Square bars of co-continuous composites were then processed by using this reactive metal penetration (RMP) method.

As an alternative to previously developed catalytic FeCrAlloy fibre mat burners based on perovskite catalysts, new catalytic burners have been developed based on Pd catalyst on lantana-stabilised Al2O3 and different fibre structures (NIT100A, NIT100S and NIT200S by ACOTECH NV).

Combustion synthesis has been applied to LaMnO3 production with a view to boosting its activity towards natural gas combustion by enhancing its specific surface area. With a highly exothermic and self-sustaining reaction, this oxide can be quickly prepared from an aqueous solution of metal nitrates (oxidisers) and urea (fuel). The favourable conditions for LaMnO3 formation were sought: only fuel-rich mixtures are effective, but carbonaceous deposits are formed when too much urea is used.

Co-continuous ceramic-metal composites (C4) were prepared by reactive metal penetration of cordierite-based ceramics used as oven refractory. A compositional and physical characterisation of both precursors and composites was carried out to understand how the choice of the starting material affects the reactive metal penetration. Mechanical behaviour was then compared with that of composites obtained from silica glass or fully sintered cordierite ceramics.

Co-continuous metal–ceramic composites synthesised by the reactive metal penetration method, starting from silica preforms and a 99.5% pure aluminium alloy, were characterised in high cycle tension–compression fatigue. The tests were performed at ambient temperature, in load control and with R = −1; the fracture surfaces were observed in a scanning electron microscope. The Wöhler curve is rather flat, suggesting that these composites behave similarly to ceramics, and the fatigue limit at 107 cycles is 91 MPa.

Nanostructured zirconia toughened alumina composite has been prepared by solution combustion synthesis. Urea has been used as sacrificial fuel and metal nitrates as precursor reagents. A traditional composition for the final ceramic–ceramic composite has been chosen: 20 vol.% of t-zirconia partially stabilized with 3 mol% of yttria dispersed in alumina matrix.

With the aim of reducing the overall cost of the process, co-continuous metal–ceramic composites were obtained by reactive metal penetration, starting from very low cost cordierite preforms. It was investigated how the preform porosity influences both the residual porosity left in the composites after infiltration and the mechanical properties.