G. Smalakys “Peculiarities of tobermorite and xonotlite synthesis from natural rocks, their properties and applications” doctoral dissertation defence

Thesis Defense

Author, Institution: Giedrius Smalakys, Kaunas University of Technology

Science area, field of science: Technological Sciences, Chemical Engineering, T005

Scientific Supervisor: Prof. dr. Raimundas Šiaučiūnas (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005)

 Dissertation Defence Board of Chemical Engineering Science Field:
Prof. Dr. Kęstutis Baltakys (Kaunas University of Technology, Chemical Engineering, T005) – chairman
Assoc. Prof. Dr. Anatolijus Eisinas (Kaunas University of Technology, Chemical Engineering, T005)
Prof. Dr. Habil. Aivaras Kareiva (Vilnius University, Natural Sciences, Chemistry, N003)
Dr.-Ing. Liudvikas Urbonas (Technical University of Munich, Germany, Technological Sciences, Materials Engineering, T008)
Prof. Dr. Eugenijus Valatka (Kaunas University of Technology, Chemical Engineering, T005)

The dissertation defence takes place online.

The doctoral dissertation is available at the library of Kaunas University of Technology (K. Donelaičio g. 20, Kaunas).

Annotation:

The main measure to reduce energy losses is the usage of insulating materials. One of the efficient types of energy-saving products with an operating temperature of 1050 °C is calcium silicate materials (1.13 nm tobermorite or xonotlite). Moreover, xonotlite features the lowest content of crystalline water, is the most heat-resistant and the most thermally stable (its decomposition temperature is 1050–1100 ℃) of all calcium silicate hydrates. However, its synthesis processes are complex and highly dependent on the properties of the raw materials, the amount of impurities and the parameters of the hydrothermal treatment. Given that changing one of the synthesis conditions can unpredictably change the whole process of compounds formation, this dissertation investigated the influence of raw material, mixture composition and hydrothermal synthesis parameters on 1.13 nm tobermorite and xonotlite formation, crystallite size, dispersity, thermal stability. The suitability of materials with various modifications of SiO2 (quartz, cristobalite, tridymite, amorphous SiO2) were compared, the technological parameters of fast and economically attractive synthesis of 1.13 nm tobermorite and xonothlite were proposed, also the intervals for the formation and stability of intermediates were determined. The most important characteristics of xonotlite were investigated: its specific surface area, pore diameter and volume, the model of predominant pores, and assessed suitability for insulating materials. It was determined that carbonate opoka is suitable for production of xonotlite based heat-resistant (up to 1000 °C) thermal insulation product and presented principal technological scheme of production.

 

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