and L. N. SemykinaThe possibilities for improving the technical properties and performance of ceramics using traditional methods are almost exhausted. The strength factors obtained by conventional firing of ceramics are below theoretical levels and ceramic structures are incapable of adapting to various conditions of service, such as thermal shock, chemical corrosion, etc. This results in premature failure of ceramic articles and constructions.In principle the latest ceramic technology should provide the formation of a quasistable structure capable of changing readily with varying schedules, and of maintaining volume constancy during operations [ i ].Such ceramics should possess adequate initial strength capable of ensuring the integrity of the design elements in furnaces.A model of the structure reflecting our ideas about the combination of volume constancy with a transformation capacity may consist of a densely packed spatial lattice of a crystal at the points of which, instead of atoms, particles of solid phase are situated. The bond between these particles should be effected by the formation on their surfaces of an amorphous layer of inorganic compounds, capable of entering into polycondensation reactions, with the formation of strong , spatial polymers. The volume constancy of such a structure should be provided by using solid particles, for example, grains of fused oxides of the highest refractories.The necessary condition for realizing this model is the formation on the solid particles' surfaces of an amorphized layer, consisting mainly of the chemical elements of the solid phase, and implanted ions. These ions form compounds with a great capacity for polymerization [2].
No abstract
Composite refractories and heat insulation materials of corundum, aluminosilicate and carbide ceramic compositions with improved operating properties have been prepared by modifying dispersed binder materials at different levels.
Information is provided for preparing high-alumina ceramic concretes based on a combined silicate-phosphate binder. Features are revealed for structure formation of the ceramic concrete developed during hardening, drying and firing; probable chemical reactions that occur are indicated.Recently considerable attention has been devoted to developing and studying composite binders that improve the properties of both ceramic concrete mixes and objects based on them. Composite HCBS binders in the mullite -periclase system [1], and also compacted ceramic concretes of high-alumina composition based on them, have high strength indices, low porosity and improved volumetric constancy during operation [2]. Proceeding from this, the aim of this work is to study the thermomechanical properties of corundum unfired objects, prepared on the basis of both high-alumina cement (HAC) and a composite silicate-phosphate binder developed by us for determining their production properties and development of recommendations for their application.The starting raw material for these studies was electrocorundum ÉB according to TU 2-036-0224450-022-90, highalumina cement according to TU 5739-001-20664498-93, sodium polyphosphate according to GOST 20291, sodium silicate (anhydrous) soluble according to GOST 13079, and fuzed periclase grade PPPBS-96.5 according to TU 14-8234-77.The charge composition of the test corundum unfired objects is provide in Table 1. Grading of unfired objects and naming their components are provided in accordance with recommendations [3].The composite silicate-phosphate binder for ceramic concrete KBV-521 was prepared by technology of mechanochemical binding [4]. Combined grinding of the original binder components, taken in the required ratio (see Table 1), was carried out in a laboratory porcelain mill with a volume of 8 dm 3 to preparation of fractions with a residue on a screen No. 0063 of 0.5 -1.0%. The milling bodies were uralite spheres with a density of 3.2 g/cm 3 . The ratio (by weight) of material -spheres was 1:1.5.In order to study the physicomechanical properties of refractory concrete KBV-611 and ceramic concrete KBV-521 cubic specimens were prepared with a side of 50 mm. The filler and binder for refractory concretes were mixed to visual homogeneity, then the mixture obtained with continuous stirring was moistened with the required amount of water and laid on a plastic mold. Specimens were compacted manually by ramming to total setting of the concrete mix and appearance of cement milk at the surface. Hardening of refractory concrete KBV-611 was carried out first in a moist atmosphere for 24 h in molds, and after extraction from a mold for
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