Papers by Author: Daniela Herman

Abstract: The crystallisation mechanism of glass-ceramic materials from a CMAS group Al0.37B0.34Fe0.01Mg0.02Zn0.29Ca0.05Si0.78O3 was tested under non-isothermal conditions by the DTA method. Glass-ceramic material of two-phase composition with precipitation of crystallites from islet silicates Zn2SiO4 and a crystalline phase from a spinel group, gahnite ZnAl2O4 was obtained in the system under investigation. Activation energy of a crystallization process Ea was determined and a crystal growth morphology parameter n was computed. It was revealed that in the test material from a CMAS group one could obtain the crystalline phase in the form of ghanite as a result of a controlled process of crystallization. The occurrence of a spinel phase caused the obtained glass-ceramic material had higher fracture toughness (KIC) than material from a CMAS group, containing pyroxene crystalline phases typical for this system.

Abstract: A new type of ceramic abrasive tools prepared of aluminium oxide (alumina), designed to realise the one-pass process of inside diameter grinding. Distinctive feature of these tools is the gradient distribution of the abrasive grain zones with different sizes and structure which enables to carry out the rough (efficient) and finishing grinding in one pass. An influence of the grinding speed vS and the quantities of the working engagement ae on the worksurface roughness and the grinding power were determined.

Abstract: The paper presents results of investigations on the application of glass-ceramic to bonding the CBN grains into abrasive composite. The application of the glass with specific chemical composition makes it possible to generate the designed crystalline phase in it. A type of crystalline phase has a significant influence on the elastic modulus E.