Oxidation behavior of electrically conductive α/β SiAlON composites with segregated network of TiCN |
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| Authors: | Ali Çelik Erhan Ayas Etem Halil Alpagut Kara |
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| Affiliation: | 1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland;2. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Materials Processing, Feuerwerkstrasse 39, CH-3602 Thun, Switzerland;1. Anadolu University, Department of Materials Science and Engineering, Iki Eylul Campus, 26480 Eskisehir, Turkey;2. MDA Advanced Ceramics Ltd., TR-26110 Eskisehir, Turkey;1. International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), PO Balapur, Hyderabad 500 005, India;2. School of Engineering Sciences and Technology, University of Hyderabad, Gachibowli, Hyderabad 500 046, India;1. Thermal Energy Research Centre, Shenyang Aerospace University, Shenyang 110136, PR China;2. Chemical Engineering, University of Newcastle, Callaghan, NSW 2308, Australia |
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| Abstract: | The oxidation behavior of novel electrically conductive α/β SiAlON composites with a continuous network of 2.5–10 vol% TiCN particulates was investigated. Composites, produced by coating spray dried granules with nano TiCN particles by a simple blending method, were gas pressure sintered at 1990 °C for 1 h under 10 MPa N2 pressure. Oxidation tests were carried out between 800 °C and 1200 °C in air for 2 and 48 h in atmosphere of dry air. Below 1000 °C, the formation of TiO2 crystals on the surfaces of TiCN particles was observed. Before the glass transition temperature of intergranular phase (Tg < 1000 °C), it was revealed that oxidation is controlled by the diffusion of oxygen into pre-formed TiO2 particles. Above Tg, liquid glass dissolves the intergranular phase elements such as Ti, Y, and Si at the interface between TiCN and SiAlON particles. Migration of Ti towards the (opening point of the TiCN network) surface was found to be the main reason for the formation of subsurface porosity that slows down Ti diffusion through the surface. Moreover, it was detected that at high temperatures surface porosity filled by the intergranular glassy phase. Consequently, the oxidation rate was found to be decreased due to the slower oxygen diffusion. |
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