Combustion Synthesis of NbB2–Spinel MgAl2O4 Composites from MgO-Added Thermite-Based Reactants with Excess Boron

Crystals

Yin-Chien Chen¹  Chun-Liang Yeh¹ 

[1] Department of Aerospace and Systems Engineering, Feng Chia University, Taichung 40724, Taiwan;

关键词: boride nbb₂;    spinel mgal₂o₄;    combustion synthesis;    microstructure;    thermite;   

DOI  :  10.3390/cryst10030210

来源: DOAJ

【 摘 要 】

The formation of NbB₂−MgAl₂O₄ composites from the MgO-added thermite-based reaction systems was investigated by self-propagating high-temperature synthesis (SHS). Two thermite mixtures, Nb₂O₅/B₂O₃/Al and Nb₂O₅/Al, were, respectively, adopted in Reactions (1) and (2). The XRD analysis confirmed the combination of Al₂O₃ with MgO to form MgAl₂O₄ during the SHS process and that excess boron of 30 atom.% was required to yield NbB₂−MgAl₂O₄ composites with negligible NbB and Nb₃B₄. The microstructure of the composite reveals that rod-shaped MgAl₂O₄ crystals are closely interlocked and granular NbB₂ are embedded in or scattered over MgAl₂O₄. With the addition of MgAl₂O₄, the fracture toughness (K_IC) of 4.37−4.82 MPa m^1/2 was obtained for the composites. The activation energies E_a = 219.5 ± 16 and 167.9 ± 13 kJ/mol for Reactions (1) and (2) were determined from combustion wave kinetics.

【 授权许可】

Unknown