The raw materials composition usually contains clay, sand and additives. Clay minerals ensure plasticity, densification through a firing process at high temperature, and a product durability.
Sand and some other additives cause the clay recipe to become more open, resulting in the wet shaped product being easier to dry and fire.
Additives are also used, for example, to modify the colour of the fired product, or engobes and glazes are used in the surface finishing of products.
In order to obtain an understanding of the behaviour to be expected of clay recipees, we can for example determine the particle size distribution, the specific surface area, the chemical composition or the thermal behaviour.
Particle size distribution is of great importance in gaining insight into the expected shaping behaviour, drying behaviour and firing behaviour of clay raw materials. This concerns particles that can be separated by using sieves and particles of which the size can be determined based on their sedimentation speed in water.
For example, a particle size distribution is determined at 45, 63, 125, 250 micrometers and 0.5, 1, 2 and 4 mm. The sedimentation analysis detects particles of 2, 10 and 16 micrometers. The fraction smaller than 10 micrometers is referred to as the loam fraction.
TCKI uses a unique and to a great extend automated measuring method, for large quantities of raw materials with guaranteed quality.
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The chemical composition of clay raw materials provides insight into the types of minerals contained in the raw material. We can determine the quantity of a single chemical element, or examine many chemical elements simultaneously. These chemical elements may be present in the solid substance or in water-soluble salts.
We are able to put on a broad range of measuring techniques and analytical chemical measuring equipment, such as X-ray fluorescence (XRF), X-ray diffraction (XRD), inductively coupled plasma AES (ICP-OES), TOC-carbon measuring equipment, ion- chromatography (IC), ion-selective measurements and potentiometric measurements.
Thermal analyses provide insight into the expansion and shrinking behaviour of a material when it is heated or cooled. We measure this using a contact dilatometer or an optical dilatometer.
In addition, we also use an optical flex meter, which allows us to determine flex behaviour as a function of temperature (as a measure for thermal stability), or the compression and tension forces in a two-layer or multi-layer system (as in glazes attached to a clay base).
We use thermogravimetric analysis (TGA) to determine the weight loss of a material as a function of temperature. Differential scanning calorimetry (DSC) is used to determine the endothermic and exothermic reactions associated with temperature increase.