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Porous refractory articles were prepared at the Magnesite Combine using fused periclase grains (uniform granules) of fractions of 1-0.5 mm and granules of the laminated structure with the applied layer consisting of 97% MgO and 3% ZrO 2. The pressing pressure was 10 MPa. The articles were fired in a tunnel kiln at 1080~ It is clear from Table 3 that the articles made from the laminated granules are significantly stronger than those made from the continuous granules. The thermal-shock resistance and the open porosity are also higher. CONCLUSIONSIt is shown that it is possible to produce strong granules of a laminated structure based on dense periclase grains and active finely dispersed materials.The optimum production parameters have been determined. Some features of the structure and phase composition of the laminated granules obtained on the basis of periclase materials activated by additions of ZrO 2, AI203, La203, and mixtures of these are described.It is established that a characteristic feature of the structure of laminated granules is the formation on the surface layer of minerals whose presence can intensify the sintering of the masses and consequently direct the structure-formation processes in the production of an industrial ceramic.

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Figure 3 shows relationship (i0) and the region of the optimum compositions of the =oncrete articles (striated) corresponding to the condition D ~ 0.37, In 1986 the Khristoforovsk refractory block factory is proposing to make a test batch a f SiC-containing refractories (concrete articles) of the newly developed composition for the wall frames of soaking pits. CONCLUS IONSUsing the simplex-lattice planning method and the generalized preference function we located the optimum region of compositions for silicon-carbide concretes with predetermined properties and the minimum cost, It is proposed to make a trial batch of goods. l* 2. 4.5.

Stabilization of the structure of the 8-alumina ceramics that is accompanied by the formation of the ion-conducting phases S"-AI203 and 8-A120 ~ based on sodium polyalumina/es is ensured by the oxide additives such as Li20, MgO, ZrO 2 and ZrO 2 [i].A search for new additives continues in view of the occurrence of the dehydration processes in the structure of the B-alumina ceramics owing to the volatility of sodium oxide at high temperatures [21. Among the less studied additives, tantalum oxide Ta20 s deserves attention. It activates the sintering process by forming a liquid phase and facilitates uniform crystallization of the ceramic [3]. In this case, of particular importance are the processes of phase transformations and structural changes that have not been studied in detail up to now. A study of these processes is essential for obtaining S-alumina based ceramics having a high ionic conductivity.This paper deals with a study of the effect of the Ta20 s additive on the phase formation of the B-alumina ceramics at different stages of their synthesis and sintering. Comparative studies were conducted on sodium polyaluminate of stoichiometric composition (Na20"SAI20 ~) that was obtained under identical conditions. The degree of dispersion of the powders was determined on the basis of the specific surface measured according to the method of low-temperature adsorption in argon (error • and the phase composition of the synthesized powders and the sintered specimens was determined using a DRON-0.5 diffractometer and Cu Ks-radiation.Powders were prepared from the homogeneous mixtures of aqueous and alcohol solutions of sodium salts and aluminum hydroxide after recalculating with respect to sodium polyaluminate Na20-5AI203, The Ta20 s additive was introduced into the mixture in the form of metallic tantalum powder or as a freshly prepared oxide powder. The additive content amounted to 1 and 5% (weight contents). The mixtures with and without Ta205 were subjected to drying and multiple sieving (through the No. 046 sieve) and were subsequently heat treated in air in the I000-1300~ range (maintaining steps of 100~ in this case, the duration of holding at the maximum temperature amounted to 5-25 h. The dispersion and the phase composition were controlled at 5-h intervals during synthesis. Disk-shaped specimens (measuring 20 mm in diameter and 2-3 mm in height) were compacted using the synthesized powders of a specific phase composition. The specimens were sintered at 1500-1700~ in corundum crucibles having closed lids in order to decrease the sublimation of sodium oxide.