- Country of manufactureRussia
PYROPHYLLITE OF THE URALS - NEW FIRE-RESISTANT AND CERAMIC RAW MATERIALS OF RUSSIA
Results of complex studying of material structure and properties of pyrophyllite of the Chis-togorovsky field are given. Suitability of raw materials for production of ogneupor and ceramics is established. High resistance of pyrophyllitic samples to fusions of cryolitas and metal aluminum is revealed. The organization of production of pyrophyllitic ogneupor for an aluminum igneous metallurgy is recommended.
|For production alyumosilikatny an ogneupo-ditch and ceramics abroad (the USA, Japan, China, etc.) in considerable volumes use the pyrophyllite representing itself a natural mineral from a class of aluminosilicates. Chemical formula Al2O3∙4SiO2∙H2O, kristallokhimichesky structural formula Al2[Si4O10] ∙ [OH]2. Theoretical structure of a mineral, Mas. %: A12O3 28,3, SiO2 66,7, H2O 5,0. Settlement temperature of melting is about 1740 °C. Physical and chemical properties of pyrophyllite and its next kristallokhimichesky analog — talc are given in tab. 1 .|
Due to the analogy of crystal structure of pyrophyllite and talc their many physical and chemical properties are identical: a perfect spaynost on (001), very low hardness (~ 1,0 on Moosa), a lamellar form of mineral individuals, density of 2,8-2,9 g/cm3, a monoklinny singoniya. When heating water of constitution is removed completely in an interval of 700-900 °C. A product of full dehydration is Al2O3∙4SiO2 metapyrophyllite. At 1150 °C metapyrophyllite decays with formation of mullite and a kristobalit. The general sequence of phase transformations of pyrophyllite when heating: Al2O3∙4SiO2∙H2O → → Al2O3∙4SiO2 → 3Al2O3∙2SiO2 + 4SiO2. The final products of high-temperature transformations are fire-resistant connections — mullite and kristobalit, typical for all burned aluminosilicates: kaolinite, cyanite, andalusite, sillimante, topaz, etc. Due to the features of a crystal chemistry unlike other natural aluminosilicates pyrophyllite has a number of valuable physical and chemical and technological properties that provides it abroad broad application in various industries: satisfactory
fire resistance, high thermal resistance, the facilitated drobimost and izmelchayemost in connection with low hardness, chemical inertness of the natural and burned mineral to effect of various acids and salts, rather low heat conductivity, low coefficient of friction, lack of shrinkage when roasting, essential increase of hardness (to 7,5 on Moos's scale) agglomeration products at moderate temperatures (1300-1400 °C).
Especially it should be noted a possibility of use of pyrophyllite in a natural (neobo-zhzhenny) state as substitute of semi-sour chamotte fire resistance of 1650-1700 °C. When roasting the mechanical durability of pyrophyllite increases almost much and reaches 210 MPas .
In Russia and the CIS countries more than 15 fields of pyrophyllitic raw materials are known. The largest reconnoitered deposits of pyrophyllite are available in Ukraine (Ovruchsky district), Kazakhstan, in the Urals and the Far East. In Russia use of pyrophyllite as fire-resistant material began in 1867 at Spassky copper-smelting plant . Last century the main industrial extraction of pyrophyllite in the USSR was concentrated on fields of Ukraine (Kuryanovsky, Na-goryansky, etc.). In 1936 in UKRNIIO researches of pyrophyllitic slates of these fields which results showed that "slates represent very valuable raw materials for production of high-quality semi-sour products"  are executed. In 1933 L. V. Ominin established a possibility of use of the Ukrainian pyrophyllite as high-quality raw materials for production of porcelain and faience .