Protective-decorative coatings for construction ceramics based on West Siberian natural raw material

Abstract

The results of using wollastonite rocks in engobe coating compositions for finishing construction ceramics with improved decorative and performance properties in comparison to existing analogs are reported; this allows expanding the raw material base of enterprises in the domestic construction materials industry.Construction materials made of traditional ceramic materials are not always resistant to environmental factors. In exposure to temperature and aggressive gases, their physicochemical properties irreversibly change and as a consequence, they gradually deteriorate, losing their external esthetic appearance. One method of prolonging the lifetime of construction ceramics is to apply surface protective-decorative coatings; engobes are such coatings.Strong adhesion of the face layer with the ceramic base, uniform thickness and color are the basic requirements for decorated construction ceramics. The degree of adhesion of the coating to the article is a function of optimum selection of their compositions based on air and firing shrinkage indexes, which should be close -a maximum difference of 1 -1.5% (the version where the total shrinkage of the engobe layer is 0.5 -0.7% higher than the overall shrinkage of the basic mass is best) and the correspondence of their TCLE: the difference between them should not be greater than 8 -10%.Incorporation of different additives in the engobe allows correcting its properties (RF Patent No. 2052434) [1, 2] and the combining ability with the ceramic base. However, in many cases, it is not always possible to ensure the required strength of adhesion of the coating with the ceramic matrix, which limits the lifetime of engobed articles in real conditions.Two varieties of raw materials -clay and nonplasticare traditionally used in engobe coatings. Quartz sand, cullet, etc., are usually used as the nonplastic components (RF Patent No. 2257364). We used wollastonite rock as the nonplastic additive, selected because of the needle shape of the crystals in the rock-forming mineral (wollastonite), which allows predicting the potentially possible good covering power of the coating and reliable adhesion of the coating with the ceramic base of the article.Wollastonite rock from the Sinyukhinskoe deposit in the Altai Krai was used for the study in the form of finely milled polydisperse white powder of the following granulometric composition: 10% 160 -100 mm, 32% 100 -60 mm, 43% 60 -20 mm, 15% less than 20 mm. 2 Evaluation of the wollastonite rock with respect to the chemical (Table 1) and mineral compositions showed that it

Development of the technology for obtaining engobed construction articles with the "antiquity" effect

“…In papers [9][10][11], the influence of the compositions of engobes and some technological factors on the properties of coatings were investigated. Thus, the influence of the content of refractory clay, kaolin and bentonite in the charge on the rheological properties of slips and the strength of adhesion of engobes with ceramic base were studied in article [9].…”

“…It was found that the differences in the properties of the studied engobes relate to different crystalline lattice of clay minerals. The results on the improvement of decorative and operating properties of engobe ceramic coatings for the construction ceramics by introducing wollastonite to the composition of the engobe charge were obtained in [10]. The rate of sintering and the mechanism of the mass transfer in ceramic engobes were also studied in [11].…”

Macromodel of interfacial transition layer in ceramic matrix composites

“…Off-spec silica raw materials and industrial mineral waste can be used as additional raw material source [1][2][3][4][5]. At the same time, slow development of technogenic deposits for ceramic products manufacturing is connected with insufficient previous studies on physico-chemical processes that occur while burning such raw materials [6][7][8][9][10].…”