Thermal stability of powdery CrB2, TiB2 HfB2 and ZrB2

DOI: 10.62564/M4-VS1634

Valentuna Sudavtsova¹, Dmytro Mishchenko², Oleksiy Bogachenko², Ihor Goncharov², Inna Neylo², Volodymyr Kudin<sup>3

1</sup>Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine
²E.O. Paton Electric Welding Institute, Ukraine
³Taras Shevchenko National University of Kyiv, Ukraine


Powdery metal borides have high hardness, so they can be used as abrasives. Thus, the goal of this study was investigation of oxidation of chrome, titanium, zirconium and hafnium borides on air in the range of temperatures 25–1000°C in non-isothermal conditions using the derivatograph Q-1500 with the heating rates 5 and 10 K/min with simultaneous differential thermal analysis. Powdery CrB2, TiB2 ZrB2, HfB2 of “pure 99% were used. The sizes of the studied powders were determined by granulometric analysis. It turned out that particles with a diameter of 5-10 microns predominate in all powders. The studied powders of compounds interact with atmospheric oxygen in different ways. It is shown that powders TiB2 and ZrB2 begin oxidized at 540, 560°C, and CrB2, HfB2 –at 508, 780°C respectively. From TG curves calculated oxidation degree ().The composition of oxidation products was determined by the X-ray method using the DRON-3 device. According to X-ray data, the following oxides are formed: MO2(M=Ti,Zr,Hf), Cr2O3 i B2O3. Using the DTA-curves, calculated the heat effects of oxidation processes. At 1000°C, the oxidation degrees of the studied borides are as follows: CrB2(0,13), TiB2(0,15), HfB2 (0,41), ZrB2(0,81). From the obtained DTA curves, the thermal effects of the studied oxidation processes MB2 were calculated. Proportionality coefficient k between the thermal effect and the peak area under the DTA curve were assessed using similar data obtained from derivatographic studies of KCl and Na2WO4, the melting enthalpies of which are known. Taking into account the degree of transformation of the studied substances, we calculated the heat that was released in the studied processes during the complete oxidation of 1 mole of MB2. These data are qualitatively with those calculated according to Hess’s law.

Keywords
thermal stability, powders, borides, derivatograph

Acknowledgments
Not provided

References
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