Ceramics Practicum

The book presents all the methods of testing ceramic raw materials and products made from ceramic materials: first of all, the methods of testing of the properties of clay are discussed; further, determination of its chemical and mineral composition is described followed by methods for testing the key characteristics of a ceramic body and slurry, and, finally, a detailed description of methodologies for determining the performance of construction and fine ceramic products is presented. This textbook is primarily intended for English-speaking students studying the modules Chemical Technology of Ceramic Materials, Synthesis of High-Temperature Materials, Building and Fine Ceramics and Refractory and Modern Ceramics at KTU Faculty of Chemical Technology. It will also be beneficial to students of other KTU faculties or any other universities whose programs deal with the production and processing of building materials.

Micro-Machining Characteristics in High-Speed Magnetic Abrasive Finishing for Fine Ceramic Bar

The research aims to describe the micro-machining characteristics in a high-speed magnetic abrasive finishing, which is applicable for achieving the high surface accuracy and dimensional accuracy of fine ceramic bars that are typically characterized by strong hardness and brittle susceptibility. In this paper, the high-speed magnetic abrasive finishing was applied to investigate how the finishing parameters would have effects on such output parameters as surface roughness, variation of diameters, roundness, and removed weight. The results showed that, under variants of diamond abrasives sizing between (1, 3 and 9 µm), 1 µm showed comparatively good values as for surface roughness and roundness within shortest processing time. When the optimal condition was used, the surface roughness Ra and roundness (LSC) were improved to 0.01 µm and 0.14 µm, respectively. The tendency of diameter change could be categorized into two regions—stable and unstable. The finding from the study was that the performance of ultra-precision processing linear controlling was possibly achievable for the stable region of diameter change, while linearly controlling diameters in the workpiece.

Microstructure of Coatings on Nickel and Steel Platelets Obtained by Co-Milling with NiAl and CrB2 Powders

Metal matrix composite coatings are developed to protect parts made from materials susceptible to wear, like nickel alloys or stainless steel. The industry-established deposition method is presently an atmospheric plasma spraying method since it allows the production of both well-adhering and thick coatings. Alternatively, similar coatings could be produced by co-milling of ceramic and alloyed powders together with metallic plates serving as substrates. It results in mechanical embedding of the powder particles into exposed metallic surfaces required coatings. The present experiment was aimed at the analysis of microstructure of such coatings obtained using NiAl and CrB2 powders. They were loaded together with nickel and stainless steel platelets into ball mill vials and rotated at 350 rpm for up to 32 h. This helped to produce coatings of a thickness up to ~40 µm. The optical, scanning, and transmission electron microscopy observations of the coatings led to conclusion that the higher the rotation speed of vials, the wider the intermixing zone between the coating and the substrate. Simultaneously, it was established that the total thickness of the coating deposited at specified conditions is limited by the brittleness of its nanocrystalline matrix. An increase in the hardness of the substrate results in a decrease of the intermixing zone. The above results indicate that even as the method based on mechanical embedding could so far produce thinner coatings than the plasma spraying, in the former case they are characterized by a more uniform nanocrystalline matrix with homogenously distributed fine ceramic particles.

The effect of mechanical activation of the reaction mixture on the formation of the microstructure of ZrB2‒CrB composites obtained by electrothermal explosion under pressure

Composites ZrB2‒CrB with a ceramic bond content of 80 wt. % and relative density 0,85‒0,90 were obtained by the method of electrothermal explosion (ETЕ) under pressure. It is shown that mechanical activation (MA) of the initial powder mixture reduces its heterogeneity and increases its reactivity. A fine ceramic composite with a homogeneous microstructure was obtained containing needle-like ZrB2 grains. Ill. 5. Ref. 13.