THE PRODUCTION OF β - SIALON BY CARBOTHERMAL REDUCTION AND NITRIDATION OF KANKARA CLAY

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Department of Engineering

ABSTRACT
The production of (β-sialon - a ceramic material that can be used in the production of refractory articles for use in the iron and steel industries, chemical and process industries, non ferrous metallurgical industries etc, from local1y avai1able rawmaterials using locally assembled production facility has been attempted, p- Sialon can be prepared from natural aluminosi1icate raw materials by carbothermal reduction and nitridation at high temperatures (> 1100°C). To produce β-sialon from locally available aluminosi1icate raw materials, Kankara clay which is a good local kaolinitic clay was chosen. Carbothermal reduction of Kankara kaolinitic clay was therefore carried out in this study, with Onyeama Coal serving as the carbon source for the reduction reaction in nitrogen gas atmosphere. Proximate analysis on the Onyeama Coal has shown that, the coal is rich in the amount of fixed carbon (85.9 wt.%), less ash content (5.1 wt.%) and moderate volatile matter (8.91 wt.%). A local production facility to carry out the carbothermal reaction has been set up. A reaction chamber from locally available raw materials was designed and fabricated using investment casting technique. An existing gas-fired furnace design partially constructed, was completed, assembled and tested. From the experimental results, the furnace can be operated up to 1060°C without incorporating a blower for about seven hours. The bulk nitrogen analysis of the sialon product formed has shown that very small concentrations of β-sialon were obtained using the production facility under the operating conditions achieved. At nitrogen flowrate of 72.4 ml/s, a peak temperature of 1360°C was achieved during the first production run which lasted for about 13 hours resulting in about 2.97 wt% (β-sialon. Similarly for the second production run which lasted for about five hours at nitrogen flowrate of 143.68 ml/s, a peak temperature of 1260°C was achieved resulting in about 3.32 wt.% β-sialon. During the third production run which lasted for about four hours at nitrogen flowrate of 102.23 ml/s. a peak temperature of 1315°C was achieved resulting in about 3.23 wt.% β-sialon.