Michel Parlier

State of the art and perspectives for oxide/oxide composites☆

Abstract The analysis of the mechanical capabilities and drawbacks of the main CMCs available at the moment highlights the potential of oxide/oxide composites for applications in turbine engines as combustor walls. New processing routes based on liquid infiltration using alkoxides or reaction-bonding techniques are presented with the objective to develop non-oxidable CMCs at lower manufacturing cost than SiC/SiC composites.

Elaboration of low shrinkage mullite by active filler controlled pyrolysis of siloxanes

Abstract The active filler controlled pyrolysis of polymers has been used to synthesize mullite from Al 2 O 3 -filled, Al-filled and Al/Al 2 O 3 -filled siloxanes. Due to the presence of transition alumina and to a finer scale of mixing of the mullite precursors provided from active Al-filler, the beginning of mullitization temperature was lowered in the two last systems (1200–1250°C) in comparison to the first one (1400°C). The mullite equiaxed-grains obtained from the polymer/Al 2 O 3 (PAO) system contained a large amount of dislocations whereas in polymer/Al (PA) and polymer/Al/Al 2 O 3 (PAAO) derived samples they were primarily dislocation free. The presence of small amounts of residual glassy phase was observed as glassy pockets at triple-junctions in the whole of the materials. The improved microstructure obtained with the Al/Al 2 O 3 -filled mixture indicates that this system seems to be a good choice for a low shrinkage and low defect mullite, in comparison to mullite obtained from Al-filled and Al 2 O 3 -filled siloxanes.

Pressure Sensor via Optical Detection Based on a 1D Spin Transition Coordination Polymer

We have investigated the suitability of using the 1D spin crossover coordination polymer [Fe(4-(2′-hydroxyethyl)-1,2,4-triazole)3]I2·H2O, known to crossover around room temperature, as a pressure sensor via optical detection using various contact pressures up to 250 MPa. A dramatic persistent colour change is observed. The experimental data, obtained by calorimetric and Mössbauer measurements, have been used for a theoretical analysis, in the framework of the Ising-like model, of the thermal and pressure induced spin state switching. The pressure (P)-temperature (T) phase diagram calculated for this compound has been used to obtain the P-T bistability region.

Formation at low temperature with low shrinkage of polymer/Al/Al2O3 derived mullite

Abstract The active filler controlled pyrolysis of polymer has been used to synthesize mullite from Al/Al 2 O 3 -filled siloxane. This monolith has been compared to mullite synthesized in the same conditions from Al-filled and Al 2 O 3 -filled siloxanes. Due to the presence of transition alumina and to a finer scale of mixing of the mullite precursors provided from the active Al-filler, the initial mullitization temperature was lowered in the two first systems (1200–1250°C) in comparison to the last one (1400°C). However, the improved microstructure obtained with the Al/Al 2 O 3 -filled mixture indicates that this system has advantages of low temperature and shrinkage, and low defect mullite, in comparison to mullite obtained from Al-filled and Al 2 O 3 -filled siloxanes.

Microstructures and Interfaces in Melt-Growth Al2O3-Ln2O3 Based Eutectic Composites

Directionally solidified oxide eutectic ceramics were prepared from Al2O3, Ln2O3 and ZrO2 based binary or ternary systems. Their microstructures consist of continuous networks of single-crystal Al2O3 and oxide compounds (LnAlO3, Ln3Al5O12) which interpenetrate without grain boundaries. The outstanding stability of these microstructures gives rise to a high strength and creep resistance at high temperature. Influence of growth conditions on the morphology of the as-obtained microstructures was studied. Preferred growth directions, orientation relationships between phases and single-crystal homogeneity of specimen were revealed. Low residual stresses were measured in the binary eutectics and fracture toughness at room temperature was improved by the addition of zirconia at a eutectic composition in ternary systems.

Dilatometric study of β-alumina single crystals

Abstract Single crystals of β-alumina exhibit an important dilatometric anisotropy. The anisotropic factor is about three for βNa-alumina. Variations of this factor are followed according to the nature of the conducting ion and the stoichiometry. The dilatometric behaviour of these compounds is explained (up to 800°C) from previous structural results.

Mullite and SiC Matrix SiC Fibre Composites for High Temperature Application

This paper presents the results concerning the development of two types of Ceramic Matrix Composites (CMC’s), SiC/Mullite and SiC/SiC composites manufactured by liquid processing route involving respectively oxide and covalent polymeric precursors. After a short justification for the selection of these processing routes, it is shown how to obtain a sound and non brittle composite through a precise control of both the formulation of the precursors and the processing parameters. The mechanical properties of these new composites are discussed in close connection with the reinforcement design and the fibre-matrix interfacial shear stress measured using the micro indentation technique. Finally, the interfacial microstructure of SiC/Mullite composite is discussed at the light of TEM observations.