Sol-gel Mullite Matrix-SiC and -Mullite 2D Woven Fabric Composites with or without Zirconia Containing Interphase: Elaboration and Properties
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文摘
The properties of composites made with fabrics of Nicalon® NLM202 SiC or Nextel® 440 mullite fibers are reported. The method used to make composites is a three stages sol-gel process: (i) in situ gelation of a mixture of alkoxides in a ceramic fiber fabric; (ii) the deposit of a matrix precursor onto the impregnated fabrics and (iii) hot-pressing of the stacked fabrics in a carbon mold. The composites have been studied by SEM and TEM. Three point flexural strength has been measured at room temperature and at 900°C in air. Local Young's modulus, microhardness and interfacial shear stress have been determined at RT. Micro-Raman spectra and X-ray microanalysis have been used to study the fiber-interface reactions. Using a mixture of aluminium-silicon ester and tributylborate as interface precursor, we obtained a carbon film free SiC-mullite sliding interface. The use of a complementary ZrO2-GeO2 gel interface precursor allows us to obtain dense composites at a low temperature exhibiting good mechanical properties (linear behaviour up to 180 MPa, even after annealing in air). The effects of a zirconia interphase on the mechanical properties of mullite-mullite composite are also discussed.