High-temperature oxidation of AlB12-Al composite material

DOI: 10.62564/M4-VS1403

Aleksandr Umanskyi¹, Valery Muratov¹, Vladimir Sheludko¹, Tatiana Khomko¹, Valery Kremenitsky², Aleksandra Pertko³, Marina Vasilkovskaya¹, Vladimir Povazhnyi<sup>3

1</sup>Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine
²Technical Center of NASU, Ukraine
³V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry, Ukraine


The study of high-temperature oxidation is urgent from theoretical and practical points of view [1]. The object of the study is the AlB12-Al composite material consisting of a porous ceramic frame of AlB12 infiltrated with molten Al in a vacuum at a temperature of 1100 °C. The oxidation of samples was studied by TGA and DSC, as well as by holding them for 1 hour in the temperature range from 500 to 1000 °C. The activation energy of oxidation Еа, the pre-exponential factor k0 and the order of the chemical reaction n were calculated by the method of non-isothermal kinetics with software implementation. X-ray analysis of the composites was carried out on a DRON-3M diffractometer in CuKα-filtered radiation. The structure was studied using a JEOL JSM-6490 LV scanning electron microscope. The most characteristic oxidation intervals can be distinguished: at temperatures from 20 to 225 °C there is a sharp increase in weight gain with low activation energy. With a subsequent increase in temperature, the rate of weight gain slows down. In the range of 450-570 °C, a melt of B2O3 is formed, at 655 °C Al melts, which is accompanied by cracking of the oxide layer. In the temperature range of 800-1000 °C, Al borates (Al4B2O9, Al8B2O15, Al18B4O33) are formed, which also prevent oxidation. At T = 646 °C crystallization of the Al melt occurs, as evidenced by the exo-peak at this temperature. Reaction order values range from 0 to 1. Under isothermal heating conditions, starting from 500 °C, there is a gradual weight gain with increasing scale thickness (at T = 1000 °C to 142 μm), with the exception of T = 900 °C, at which the scale thickness is 38.4 μm due to a decrease in the weight gain at this temperature. B2O3 and Al melts fill pores, cracks and smooth the surface, reducing roughness (Ra = 12 nm) and oxidation surface area. Thus, we can conclude that the AlB12-Al composite material is resistant to high-temperature oxidation up to T = 1000 °C.

Keywords
High-temperature oxidation, AlB12-Al, TGA, structure

Acknowledgments
Not provided

References
[1] A.S. Khanna, Fundamentals of High Temperature Oxidation/Corrosion, High-Temperature Corrosion. Ed. by A.S. Khanna. – World Scientific, New Jersey, USA, 2016.– PP.1-31.