Synthesis and oxidation of nanocrystalline HfB2

Creep and Oxidation of Hafnium Diboride Based Ultra High Temperature Ceramics at 1500C

“…Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of nanocrystalline HfB 2 showed an initial weight decrease from room temperature to about 400˚C, significant weight increase from 400 to 723˚C, and then slowing of the weight increase to nearly zero at 1000˚C [33]. These observations are consistent with the melting and evaporation temperatures of B 2 O 3 , but the initial weight decrease was attributed to the removal of water from the sample.…”

Mechanical activation-assisted autoclave processing and sintering of HfB2-HfO2 ceramic powders

“…It was stated that the usage of relatively mild temperatures which are high enough to trigger crystallization but still low enough to avoid excessive grain growth (ideally in the range of 500-900 °C), enables to obtain nanostructures [46]. In a previous study in which HfB 2 powders were prepared by a reaction of HfCl 4 with NaBH 4 at 600 °C in an autoclave, it was stated that the powders had small particle size range of 20-30 nm [17]. In another study in which a chemical reaction in an autoclave were utilized for the synthesis of different borides such as TiB 2 and ZrB 2 from related oxides and amorphous B in the presence of elemental Na and S, particle size of the TiB 2 and ZrB 2 products were respectively reported as 100 and 500 nm after related washing and leaching treatments [23].…”

“…The most well-known synthesis methods are borothermal and boron carbide reductions which a mixture of HfO 2 and amorphous B or B 4 C powders are reacted at elevated temperatures above 1500 °C [11,14,15]. The other production techniques employed for the synthesis of HfB 2 are self-propagating high-temperature synthesis (SHS), milling-assisted processes, sol-gel method, solvothermal synthesis, electrochemical method and chemical vapor deposition (CVD) [15][16][17][18][19][20][21]. Besides, there are only a few studies on the preparation of HfB 2 -HfO 2 ceramic powders.…”

First-principles study of the elastic and thermodynamic properties of HfB2 with AlB2 structure under high pressure

“…Because of these properties, HfB 2 has been widely investigated in literatures. Chen et al [11] and Sonber et al [12] reported the synthesis of HfB 2 in different methods. Shein and Ivanovskii [13] studied the structural and elastic properties of HfB 2 using first-principles calculations.…”