Termo-kimyasal yöntemle alon, MgAlON ve MgAl2O4 toz üretimi

Due to their major importance in the field of armor and transparent infrared windows, aluminum oxynitride (AlON), magnesium aluminate, also known as spinel (MgAl2O4) and magnesium aluminum oxynitride (MgAlON) have always been subject to research due to the limitations of their manufacturing processes. The interest of synthesizing fine powders of these ceramics at intermediate temperatures, aims to decrease the high cost of the final products, as well as, providing promising commercial methods to produce their powders. AlON powders are commercially unavailable and can only be found as a ready to use products, produced via direct sintering of submicron aluminum oxide (Al2O3) and aluminum nitride (AlN) at temperatures exceeding 1850°C.This process has the disadvantage of raising the cost of the product together with the fact that many companies whose arsenal of equipment allows them to design their own parts, will not have the flexibility of purchasing aluminum oxynitride powders and manufacturing their own products. Unlike AlON, spinel can be found commercially as powder and has already been manufactured and sold worldwide but a limited number of companies. Nevertheless, the production process as well as the cost of production are still major issues that cause a significant increase in the price of the product to provide spinel powders with high purity and fine particles. MgAlON has been presenting itself as an intriguing technical ceramic since it perfectly mimics AlON with properties as close as its parent phase. This is due to the that magnesium aluminum oxynitride is considered as a magnesium stabilized AlON with a slightly lower stability temperature without a major loss in the mechanical and optical properties of aluminum oxynitride. With that in hand, there has always been an interest in investigating the synthesis of these ceramics via different methods to optimize their synthesis processes or even providing novel approaches to obtain their powders. In the last years, an innovative approach that can be considered as a modified carbothermal reduction nitridation (CRN) has been investigated in the synthesis of technical ceramics and has been deemed effective in providing powders that can be readily used in their as-synthesized form. "Dynamic / Thermochemical Method" (DTM) is the denomination used to describe this approach. In this process, the reduction and nitridation reactions take a place in a moving system that provides constent motion to the synthesis allowing the reaction to proceed and be accomplished in a relatively shorter time then usually needed in the convention CRN method as well as the massive advantage of relatively lowering the reaction temperature. In this PhD thesis, the optimization of these technical ceramics' synthesis has been investigated via the DTM process. The obtained results showed that a temperature of 1500°C was sufficient to fully synthesize MgAlON powders from aluminum and magnesium hydroxides (Al(OH)3 and Mg(Al)2, respectively) in gas mixtures, without any solid carbon added. It has also been found that more than 50% conversion to AlON could be achieved at an unpreceded temperature of 1500°C with submicron particles. Conversely, AlON and MgAlON whose syntheses via the dynamic thermochemical method was successful, MgAl2O4 had better results in the static synthesis comparing to its dynamic counterpart. The obtained results were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and particle size distribution. The obtained results were explained and some recommendations for further investigation and optimization of the results we provided.