Rheological properties of slips based on polymineral clays with electrolyte additives

Abstract

The effect of various electrolytes (soda ash, water glass, sodium tripolyphosphate, coal-alkali reactant) as well as their combinations on the rheological properties and electrokinetic potential of ceramic slips for souvenir bottle production based on polymineral clays from Belarus is investigated. It is established that the maximum liquefying of ceramic suspensions is reached under the joint effect of a combination of electrolytes, due to the simultaneous impact of cation exchange and physical adsorption of anions in the system. Production of ceramics by casting is widely applied in the ceramic industry for making household and fancy majolica, porcelain, and faience products (vases, tea and coffee sets, bottles for pouring alcoholic beverages, etc.).Since majolica products are usually made from lowgrade low-melting clays that have poor liquescence, casting ceramic slip into gypsum molds encounters certain difficulties, namely, poor liquescence and, accordingly, high thickening coefficients.The rheological properties and aggregate stability of ceramic slips are responsible for their technological properties (mobility, casting rate, degree of filling of gypsum molds) and the physicomechanical properties of finished products (porosity, strength, moisture impermeability, etc.).Slips with minimum moisture should be easily transported via a slip pipeline, have good filtration properties, and at the same time should not stratify under protracted storage, or contain gas bubbles, or foam in casting [1].It is known that the rheological properties of casting slip to a large extent are determined by a number of factors: slip composition, solid phase dispersion, solid particle shape, extent of chemical interaction between the solid and liquid phases, low viscosity of the liquid phase, degree of solubility of the solid phase in the liquid one, capacity for dissolving electrolyte, etc.One of the most effective methods for controlling the rheological properties and the aggregate stability of such suspensions is using liquefying additives (electrolytes) whose effect is based on ion-exchange processes occurring on the surface of mineral particles of the slip.The most frequently used electrolytes are various sodium salts, which dissociate in the slip and affect the sorbed complex. When an electrolyte is added to a slip with prevalence of Ca 2+ in its exchange complex, Na + cations, whose adsorption energy is lower than that of Ca 2+ , replace Ca 2+ cations in the sorbed complex, initially in the diffusion layer and afterwards in the surface layer. The replacement of Ca 2+ cations by monovalent Na + increases the thickness of the diffuse shell of the micelles, the electrokinetic potential of the system, and the looseness of the slip structure [2]. Furthermore, liquescence depends not only on cations, but on anions as well, which participate in the ion-exchange processes and replace water molecules adsorbed on the surface of clay particles, which contributes to thinning the slip.The impact of electrolyte on the state of the slip can...

Effect of nanodisperse particles of silicon and aluminum oxide hydrosols on structure formation of clay minerals in aqueous medium

“…The graph shows that for the refractory clay, the increase in the fluidity on addition of SS and consecutive addition of SS and AS-1 is greater than for bentonite clay, which is also in agreement with the previous arguments. A change in the hydration shells of the clay microparticles that affects the structure of the clay suspensions can take place simultaneously [2,3].…”

“…Using different fluidizing additives whose effect is based on ion-exchange processes on the surface of the mineral particles in the slip is an effective method of regulating these properties. The system changes from freely disperse to structured at a certain ratio of disperse phase and dispersion medium in the suspensions [3,4].We know [3] that the laminar structures of clay minerals, primarily kaolinite and montmorillonite, are composed of parallel layers of silicon-oxygen tetrahedrons with aluminum, magnesium, and iron atoms basically positioned in the center. The differences in the structure of these minerals are due to the density of the crystal lattice and the distance between regularly repeating groups of ions (planes), equal to 0.72 nm for kaolinite and on average 1.5 (0.95 -1.9 nm) for montmorillonite [5].…”

“…Using different fluidizing additives whose effect is based on ion-exchange processes on the surface of the mineral particles in the slip is an effective method of regulating these properties. The system changes from freely disperse to structured at a certain ratio of disperse phase and dispersion medium in the suspensions [3,4].…”

“…We know [3] that the laminar structures of clay minerals, primarily kaolinite and montmorillonite, are composed of parallel layers of silicon-oxygen tetrahedrons with aluminum, magnesium, and iron atoms basically positioned in the center. The differences in the structure of these minerals are due to the density of the crystal lattice and the distance between regularly repeating groups of ions (planes), equal to 0.72 nm for kaolinite and on average 1.5 (0.95 -1.9 nm) for montmorillonite [5].…”

Impact of the Xanthan Gum on Rheological and Mechanical Properties of Slip of Ceramic

“…The rheological properties of slips are of great importance in ceramics manufacturing techniques such as extrusion, pressing, slip casting and glazing [3]. Various parameters such as: chemical and mineralogical composition of the raw material, particles size, their distribution and shape, density of the slurry slips, temperature, pH, extent of chemical interaction between solid and liquid and low viscosity of the liquid phase affect the rheological parameters of the slips [4,5]. The quality and strength of the final product depend on the microstructure of the cast layer.…”