Properties of materials of the system Al2O3-SiC-C after firing in a reducing atmosphere

Abstract

A set of studies is presented for the physicomechanical properties of corundum-graphite carbide-containing refractories. The efficiency of introducing silicon carbide as an antioxidant addition to Al 2 O 3 -SiC-C-materials is established. The structure and phase composition of corundum-graphite silicon carbide-containing refractories based on an ethyl silicate binder fired in a reducing atmosphere are studied.Under contemporary conditions the role of refractory materials with a set of valuable properties such as heat resistance, high corrosion and erosion resistance, mechanical strength, constantly increases. On one hand, as a result of the introduction of new advanced technology the overall volume of the requirement for refractory materials decreases, and on the other hand at the same time an improvement is noted in the qualitative characteristics [1 -8].One of the most important methods for improving graphite-containing refractories is development of methods for protecting carbon from oxidation, and this may be resolved by adding metals, oxygen-free compounds and other materials, that actively react with oxygen, they form a liquid phase and create a coating of the "glaze" type preventing diffusion of oxygen into the refractory. Resistance to oxidation of the material obtained depends on the nature and quality of the newly formed synthesizes secondary phases that form in the intergranular space and at boundaries, and also over the surface grains. Here additions should carry some engineering load as much as possible, for example promote an increase in ductility of the formable mix, reduce the lower temperature limit for the mix sintering range, and increase the density of the sintered material, which reduces access of oxygen to the surface of graphite flakes and reduces the oxidizing capacity of the material as a whole.Silicon carbide is added to a charge in order to give corundum-graphite articles increased heat and abrasion resistance. In addition, it forms with oxidation of articles a protective film that prevents further burning of graphite [9].Recently a study has been made of the properties of corundum-graphite silicon carbide materials, prepared by semi-dry compaction using modified ethyl silicate hydrolyzates as a binder (Fig. 1). Specimens were fired in a reducing atmosphere at 1450ºC with soaking for 3 h.Introduction into the composition of the mix of silicon carbide, that provides high erosion resistance, resistance to oxidation, fulfilling the role of an antioxidant, and also use of modified ethyl silicate binder, that satisfactorily protect graphite, give strength to the raw material, limit oxidation of graphite and are a source of amorphous SiO 2 that has a capacity to enter into reaction with a-Al 2 O 3 with formation of mullite, gives rise to the desirability of carrying out studies directed towards optimizing the composition of corundum-

Nanodispersed silica and some aspects of nanotechnology in the field of silicate materials science. Part 4

“…Properties have been reported [58] for corundumgraphite-carbide-silica refractories made by pressing with the use of binding agents based on modified hydrolyzed ethyl silicates, which raise the plasticity and increase the strength of the semifinished material. During the firing, the active silicon dioxide obtained by decomposition of the ethyl silicate accelerates the sintering.…”