PROCESSING OF NITRIDE POROUS CERAMIC COMPOSITES VIA HYBRID PRECURSOR SYSTEM CHEMICAL VAPOR DEPOSITION (HYSYCVD)/DIRECT NITRIDATION (DN)

摘要

The synthesis of different kinds of composites via hybrid precursor system chemical vapor deposition/direct nitridation (HYSYCVD/DN) in a multi-step approach was investigated. Ceramic porous performs (SiC and Si3N4) were used as substrates and infiltrated in successive stages (Sl-1, S1-2 and S2) varying processing conditions (type and flow rate of nitrogen atmosphere, temperature, and time). The composites were characterized by XRD and SEM. Also, some physical properties were determined by means of He picnometry, volume-measurement approach and immersion in Hg. Moreover, the thermodynamic feasibility of the possible reactions within the reaction systems was calculated using the FactSage? software and databases. The results show that the synthesis of nitride porous composites was influenced by test conditions at each stage of processing. Likewise, the effect of ceramic substrate type was important on the formation of nitrides and their microstructural characteristics (morphology, size and distribution), as well as on their physical properties.