چكيده به لاتين
Decorative enamels can be applied to metals such as copper, silver, gold, and titanium. Among these metals, silver is considerable because of its bright and beautiful appearance. Enameling of precious metals in comparison to steel, cast iron, and other alloys enameling is very easy. However, it has been developed poorly in Iran due to its limitations. First, metal enameling powders mostly are entered from foreign countries like Germany and the United States, and thus they are expensive and slightly difficult to access. Second, being hard and time-consuming has made this art less interesting for enamellers who work in such ancient field. Therefore, the primary aim of this thesis is to produce a lead-free enamel which is suitable for silver made articles and applied as a single layer enamel. To reach this aim, several enamels with different chemical compositions were introduced. After applying these compositions, one of them was selected as the main composition(C) based on its apparent features namely color, smoothness, brightness, acceptable adherence to the substrate, and having no apparent defects such as cracking and peeling. Then, to estimate the thermal expansion coefficient of the main enamel, dilatometry method is used. According to its results, thermal expansion coefficient, dilatometry softening point, and glass transition temperature of main enamel were computed 17.66×〖10〗^(-6) 1⁄(°k), 531.8 ℃, and 484.9℃ respectively.
Then, the potassium nitrate is used as an oxidizing agent for dissolving of the discoloration problem in Titania enamels, which led to D composition. In this case, thermal expansion coefficient, dilatometry softening point, and glass transition temperature of enamel were calculated 18.4×〖10〗^(-6) 1⁄(°k), 523.3 ℃, and 448.6℃ respectively.
Acid resistance, thermal shock resistance, impact resistance and micro hardness are the tests that are carried out on C and D composition. These tests showed that although adding alkali oxides to the D composition results in reducing of properties quality, this reduction is not considerable. For example, losing weight as the result of an acid attack in C and D compositions were %0.87 and %1.01, and also crack resistance under thermal shock for both composition was 265℃. Required energy for pulling off the enamel in two mentioned compositions was obtained 0.319j. Finally, C and D composition micro hardness were calculated 566.09±18.31 and 515±8.9 respectively.
In the last part of the thesis, the enamel-silver interface was surveyed. According to the SEM results, it can be mentioned that the solution of silver and enamel ions are the essential reason for their bonding.
