Clays and kaolins from Stul’nevskoe deposit

Four samples of clays containing 28–33% Al₂O₃ (in the calcined substance) and two samples of kaolins containing 41–42% Al₂O₃ were studied. It was shown that all the raw materials can be used for the production of chamotte articles for both ordinary and special applications. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 27–29, April, 1997.     

Refractory Clays of the Toretskoe Deposit

Refractory clays of the Toretskoe deposit (Donetsk Region) are described. These clays are white-burning clays and can be used in the production of high-quality porcelain and ceramics for various destinations.     

Specifics of Clays from the Andreevskoe Deposit

Clay from the Andreevskoe deposit (Ukraine) is a high-quality material suitable for the ceramic industry for manufacturing a wide range of articles, from sewage pipes to high-strength insulators.     

Clays for polymeric nanocomposites

We discuss test methods and results for determining individual clay platelets shape, size, size distribution, elemental composition, and impurities. Commercial sodium salt varieties of natural, semisynthetic and synthetic clay (Cloisite®‐Na⁺, Somasif ME‐100, and Topy‐Na⁺, respectively) were analyzed. In this international collaboration, eight laboratories on three continents carried out the work within the VAMAS TWA‐33 activities. There are large differences between the three nanofillers as far as: (1) the platelet orthogonal dimensions, (2) chemical composition, and (3) contaminants (their diversity and quantity) are concerned. Elaborate purification of natural clays leaves behind 2–5 wt% of organic and mineral impurities, whose nature, shape, size, and chemistry depend on the clay origin. These contaminants affect nanocomposite performance, thus controlling their composition and quantity is essential. The article describes the developed methods, summarizes the preliminary results, discusses the encountered difficulties, and proposes methods for solving them. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Pillared Clays as Catalysts

Clays have long been used as catalysts [1] and they retain a continuing important role since they constitute the matrix of many industrial catalysts based on zeolites. Intercalated clays are a new class of materials, in which an homogeneous distribution of micropores can be obtained with pore openings varying from 4 Å to 18 Å according to the type of pillars. These solids are then attractive because they can adsorb and convert large molecules.     

Washing Effect on the Synthesis of Silica-Pillared Clays

Silica-pillared clays were prepared by two methods: conventional and microwave irradiated. Preparation time of the conventional intercalating solution took about two days but only 15 minutes when it was microwave irradiated. Washing extent determined the size and the amount of intercalated silica pillars.The surface areas of the compounds obtained by these two different methods are comparable within error range, but the pillaring mechanism must be different as in the conventionally intercalated samples calcium is preferentially exchanged, instead in the microwave irradiated samples sodium is preferred.     

Sinterability of Low-Melting Illite-Bearing Clays

A sintered ceramic materials with water absorption below 6% is obtained on the basis of low-melting illite-bearing clays with a finely dispersed glass additive. The dependence of the properties of sintered ceramic mixtures on the quantitative ratio of raw material to the finely disperse additive is established. The process of crystallization of minerals in firing ceramic mixtures is investigated.     

Concentrations of Ions at the Surfaces of Clays

Equations based on the theory of the structure of the electrical double layer developed at a charged plane surface are used to calculate the concentrations of ions at the surfaces of clays suspended in various electrolyte solutions. The results indicate that in clays where the surface density of charge is high the conditions close to the surface are independent of the outer electrolyte concentration provided that this is not too high. The treatment is applied to the problem of the conditions present at the surfaces of clays suspended in dilute acid, and the effect of the addition of neutral salts on the acidity at the surface is discussed.     

Surface Conductivity in Sodium Clays

The formalism for describing the electrical conductivity of clay-water systems in terms of a Formation Factor and a surface conductivity is reexamined. Surface conductivity values obtained on this basis, are tabulated for five Na-clays: two montmorillonites, two kaolinites and an illite. They vary from about 4 · 10^?9 Mhos for kaolinite to 2 · 10^?9 for montmorillonite. Using the double layer approach to surface conductivity, it is shown that these values are very useful for estimating the potential at the slipping plane. Except for montmorillonite at low salt concentration ( < 0.01 N), the zeta potentials obtained from surface conductivity are consistent with a slipping plane at 4–7 Å from the clay surface.     

Structure-Controlled Reactions in Kaolinite-Diaspore-Boehmite Clays

Clays containing kaolinite, diaspore, and boehmite are analyzed chemically and mineralogically and their high-temperature reactions in the range 1000° to 1500°C are followed quantitatively by X-ray diffraction measurements. It is shown that the development of mullite progresses toward the equilibrium value as the temperature approaches 1500°C. When considered in detail, the reactions reflect the source of the alumina. Diaspore and boehmite first form corundum at widely different temperatures which results in the reactivity of the corundum from boehmite being greater than that from diaspore, and, in consequence, mullite develops more readily from the boehmite-containing clays. Relative expansions of clays rich in diaspore or boehmite when fired in the range 1200° to 1400°C are correlated with the manner in which mullite forms in this temperature range.     

Areas of Application of Clays of the Latnenskoe Deposit

A detailed characterization of clays recovered at the Belyi Kolodets, Strelitsa Blizhnyaya, and Srednii quarries of the Latnenskoe deposit is given. Industrial and commercial uses of these clays are discussed.     

Reactive Hot-Pressing of Clays and Alumina

The temperature, pressure, and time dependence of bulk density and the compressive strength of clay and boehmite compacts subjected to reactive hot-pressing were determined. The strength and the bulk density are linearly related to the extent of the dehydroxylation reaction which occurs during reactive hot-pressing. In decomposition reactions the reactivity (for interparticle bond formation) and mobility (for densification) may result from the broken bonds and resultant unsatisfied valence links produced by the reaction. On the basis of this postulation, the following empirical relation, correlating the functional relation between strength or density and temperature and pressure was obtained: Application of this equation to the data obtained experimentally produced energy values, for both densification and interparticle bonding, which are much less than that of the activation energy or the enthalpy of the reaction involved. The different energy values for interparticle bonding and densification are believed to indicate different controlling modes for these processes.     

A Thermal Study of Polymineral Clays of the Gzhel' Deposit

A thermal analysis of clays of the Gzhel' deposit is performed and their mineral composition is established. The effect of various admixtures and minerals and the dispersity on the behavior of the clays during heating is described.     

多矿物粘土基陶瓷地砖

以易熔粘土为基，并引入难熔粘土和熔剂成分，合成了地砖坯料。经研究确定，只要遵循一定的条件，是可以用上述原料生产出优质产品的。指出了制品结构和相组成的形成特点。