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High Temperature Materials

Modelling of TBC system failure: Stress distribution as a function of TGO thickness and thermal expansion mismatch

Advances in gas turbine technology place an increasing demand on thermal protection systems of nickel-base superalloys in turbine blades. Current strategies for performance improvements are focused on thermal barrier coatings (TBC).

High catalytic activity of SCS-synthesized ceria towards diesel soot combustion

Nano-sized particles of ceria with high surface area were processed by solution combustion synthesis (SCS) and their catalytic activity towards combustion of carbonaceous materials was compared with that obtained by simple thermal decomposition of cerium nitrate, exhibiting the same specific surface area.

New ceramic heat exchangers with enhanced heat transfer properties for recuperative gas burners

Heat recovery from waste gas is a major key process for increasing efficiency of thermal processes. The aim of the present work is to increase heat transfer coefficients of ceramic heat exchangers of recuperative burners using highly structured surface elements created from a textile precursor. The paper describes the chosen geometries and their thermal behavior, the ceramization process and the preliminary design of the new recuperative burners.

Exploring composites based on PPO blend as ablative thermal protection systems – Part II: The role of equiaxial fillers

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.

Exploring composites based on PPO blend as ablative thermal protection systems – Part I: The role of layered fillers

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.

Influence of ceramic particle features on the thermal behavior of PPO-matrix composites

Thermoplastic poly(phenylene oxide) (PPO)-matrix composites were prepared and characterized in order to evaluate the effect of different ceramic fillers on the thermal and combustion behavior of the matrix. In particular, ceramic particles having three different shapes were exploited as fillers, particles showing a platelet-like, a needle-like or an equiaxial morphology. The composite materials were produced through a melt blending method, which yielded a homogeneous distribution of the ceramic particles in the organic matrix.

Combustion synthesis of lanthanum chromite starting from water solutions: Investigation of process mechanism by DTA–TGA–MS

The mechanism of combustion synthesis of lanthanum chromite was investigated by carrying out simultaneous differential thermal analysis (DTA), thermal-gravimetric analysis (TGA) and quadrupole mass spectrometry measurements (MS). The whole process was found to involve several phenomena: urea and nitrates thermal decomposition, exothermal reactions occurring directly between nitrates and urea as well as between their decomposition products, final reaction between solid oxides.

Catalyzed traps for diesel soot abatement: In situ processing and deposition of perovskite catalyst

The present paper deals with the preparation of catalytic filters for Diesel particulate removal by developing an in situ solution combustion synthesis method. Lanthanum chromite perovskite catalyst has been deposited on silicon carbide and cordierite honeycombs with the aim to investigate the influence of the starting solution containing catalyst precursors on the coating characteristics. SEM, XRD and EDX analyses have been carried out in order to evaluate the homogeneity and the thickness of the catalyst layer.