Effect investigation of a thinning additive on the physical and mechanical properties of celsian ceramics obtained by slip casting

The article discusses the physical and mechanical regularities of ceramics formation based on the BaO—Al2O3—SiO2 system by slip casting into gypsum molds, and also investigates the rheological properties of a slip based on сelsian and the physicochemical properties of products made from it. The samples were made according to the following technology: the first stage is synthesis of celsian in a muffle furnace at a temperature of 1200 °C with a maximum temperature holding for 2 hours. The synthesis products were ground in a planetary mill to a residue on the № 0063 sieve of no more than 0.2 %. Then, slips with different moisture content without additives and with the addition of 0.10, 0.15 and 0.20 wt. % thinning additive Dolapix PC 67 were made. The second stage is to obtain samples by casting slip into gypsum molds. Firing of products took place in a muffle furnace at a temperature of 1350 °C with a two-hour holding. The optimal amount of thinning additive in the celsian slip was determined, which corresponds to 0.10 wt. %. It was found that, in the studied area of technological parameters, the material acquires the best properties at a sample firing temperature of 1350 °C and is characterized by the following indicators: water absorption — 10.20 %, apparent density — 2.15 g/cm3, open porosity — 21.04 %.

Sodium Hexametaphosphate as Deflocculation Agent for Calcium Aluminate Cements in Porcelain Body

Influence of typical ceramic deflocculant – sodium hexametaphosphate – on the rheological properties (viscosity) of calcium aluminate cement paste, porcelain raw materials mixture (casting slip), and fired porcelain body respectively, was determined. It was used two different typed of calcium aluminate cements (from two sources – producers - Istra, Almatis) with different content of Al2O3 (40 % and 70 %). Sodium hexametaphosphate decreases of water content needed to prepare slip casting with constant viscosity. Deflocculant increases the modulus of rupture MOR of dried green body and its bulk density. Sodium hexametaphosphate admixture is very suitable for the creation of porcelain body with low porosity after firing.

Influence of the Type of Dispersant on the Properties of Casting Slips of Porcelains with Soda-Lime Glass

The use of glass residues for the reduction of firing temperature of ceramic materials products has become an attractive alternative. For pressed or extruded products, such as tiles and bricks, the use of glass is sufficiently simple, since only milling and mixing to the industrial mass batch in partial substitution of conventional fluxes are necessary. However, in slip casting products, such as china and porcelains, the glass presence destabilizes the casting slip. This is the motivation of this work. Different types of dispersants and their influence on the properties of slips containing glass waste were evaluated. The experimental results showed that the use of conventional dispersant (sodium silicate) is not adequate. The stabilization of slips was possible only with organic dispersants. Therefore, the factors that determine the success or failure of dispersants were also analyzed.

Synthesis and Colloidal Processing of Nanocrystalline (Y2O3-Stabilized) ZrO2 Powders by a Surface Free Energy Controlled Process

Using the controlled growth technique, nanocrystalline ZrO2 powders have een prepared from solution. By variation of the Y-content (0-8 mol %), redispersable monoclinic, tetragonal or cubic ZrO2 powders with particle sizes between 5 and 10 mn were obtained after crystallization at elevated temperature and pressure. Nanodisperse suspensions of the powders have been used for colloidal processing techniques such as tape casting, slip casting or extrusion. The resulting green bodies with densities of 55 % and average pore sizes of 5 nm could be sintered at temperatures below 1100 °C leading to monoclinic, tetragonal or cubic ZrO2 ceramics.