İremnur CEYLAN, B.Sc.
Yildiz Technical University
Department of Metallurgical and Materials Engineering
Material Science Student Society
Supervisory Board Member
Development of Low Temperature Sintering Glass-Ceramics Coating on Glass via Pad Printing
Glass ceramic coatings used to improve various mechanical, physical and chemical properties of materials are used for purposes of obtaining decorative surfaces on glass substrates, providing washing resistance, providing superior mechanical and chemical resistance etc. Glass-ceramic coating can applied to substrate by various type of processes. Pad printing process, is one the most significant printing process, offers various opportunities such as applicability of coating material to all kinds of surfaces; It replaces many printing processes such as screen printing, labelling and hot stamping. Most of the items we use in our daily lives are decorated with pad printing such as automotive, medical, apparel, and electronic objects, as well as electronic appliances, toys and sports equipment. In this study, it has been made on the development of pad printing glass-ceramic coating to be used for decorative purposes of glass and especially glass cookware. This study primarily involves the formation and production of a low temperature sintering glass-ceramic composition, followed by production of low temperature enameled glass-ceramic coating. In this study, while glass-ceramic coating contains 40-60% of liquid medium and additives, it has 40-60% of frit and pigment powder content. The proportions of glass-ceramic and pigment inputs can be explained as 80-95% frit and 5-20% pigment. The temperature of enameling, which normally occurs in the 600-700 °C range, was reduced to 550-650 °C range with this study by regulating raw materials and oxide compositions of glass-ceramic.
Migration Behaviours and Health Effects of Food Contact Glass-Ceramics
Vitreous enamel is part of everyday life and it is used as coating materials on kitchen surfaces including cookers, cookware, saucepans etc. A wide variety of cookware and utensils are metallic surfaces such as cast iron, steel and aluminum due to the high mechanical and thermal properties of them. During contact between vitreous coating on metallic surface and food; chemical constituents can be migrated into the food from the surface due to the pH of the food, high temperature applications and contact time. Vitreous also called porcelain enamel coatings are inorganic coatings containing mainly oxides such as Si02, B2O3, Al2O3, Na2O, K2O, Li2O and smaller amounts of BaO, SrO, CaO, CuO, MgO, CoO, NiO, TiO2, ZrO2 oxides etc. In the enamel coatings, hazardous compounds can be present which comes from the oxide components of frit. In this study, the elements passing from the glass-ceramic surface composition to the food and the effects of the elements entering the human body with the food as a result of this migration exceeding certain limits were investigated.
Low Temperature Synthesis of Titanium Diboride
Titanium diboride (TiB2) is an important advanced ceramic material with many superior properties due to these outstanding properties, Titanium diboride is a material developed for use in a variety of engineering applications such as cutting tools, cathode for aluminum electrolysis cells, high temperature coatings, abrasion resistant composites and impact resistant armor and finally solar thermal absorbers. The various methods for titanium diboride production in the literature are as follows: Direct elemental reaction by self-propagating synthesis at high temperature, reaction with high-energy ball milling method, reaction in a sodium borate solution, carbothermic / borothermic reduction method, metallothermic reduction or bulk combustion synthesis, hydrothermal method, electrolysis of molten salt, laser-induced vapor phase reaction, aluminum melt reaction. These techniques have several disadvantages, such as expensive raw materials, the necessity of special reaction vessels, high process temperature and long process time etc. Due to these disadvantages, among the methods for mass production of titanium diboride, carbothermal reduction method is preferred because of its simplicity of operation and cheap raw materials. However, the main problems in this process are that the reduction requires high temperatures up to 1900 °C, the presence of free carbon and undesirable stable phases. In this study, synthesis of high purity (99.8-99.9%) and low grain sizes (3-5 µm) titanium diboride is aimed via carbothermic reduction combined with the mechanical activation method at temperatures between 1300-1500 °C. The industry-oriented output and widespread effect of this study is to increase the energy efficiency by reducing the process temperature and to achieve high purity in the products by sintering process with atmosphere controlled furnace.