In search of the elusive IrB2: Can mechanochemistry help?

Abstract

The previously unknown hexagonal ReB 2-type IrB 2 diboride and orthorhombic IrB monoboride phases were produced by mechanochemical syntheses. High energy ball milling of elemental Ir and B powder for 30 hours, followed by annealing of the powder at 1050 °C for 48 hours, resulted in the formation of the desired phases. Both traditional laboratory and high resolution synchrotron X-ray diffraction (XRD) analyses were used for phase identification of the synthesized powder. In addition to XRD, scanning electron microscopy and transmission

The crystal structures, phase stabilities, electronic structures and bonding features of iridium borides from first-principles calculations

“…This crystal structure search successfully reproduces the experimental structures of Pnma -IrB and P 6 3 / mmc -IrB 2 as the lowest ground state energy phases and the other theoretical ground phases of C 2/ m -Ir 3 B 2 , Fmm 2-Ir 4 B 3 , and Cm -Ir 4 B 5 , thus providing important support for the reliability of the present structure searches. 22,23,29 Negative formation enthalpy shows that the synthesis of the substance through the reference phase is an exothermic process, and the exothermic reaction is easy to occur in nature. The formation enthalpies can be calculated with the following equation:…”

“…In 2016, two groups successfully used a mechanochemical approach to synthesize two new iridium borides, namely, IrB 2 and IrB, and found that IrB and IrB 2 ceramic nanopowders may be an active catalyst material. 29,30 However, these two newly discovered borides have been proved to be metastable phases close to the convex hull curve. Previous systematic studies and synthesis of many metastable phases in Ir-B system have fully demonstrated that the study of metastable phases in Ir-B systems is very important.…”

High-Pressure Synthesis of β-Ir4B5and Determination of the Compressibility of Various Iridium Borides

“…10 In 2016, Xie et al successfully used a mechanochemical approach to synthesize two new iridium borides, namely, IrB 2 and IrB. 29 Rau et al and Latini et al investigated the hardness of Ir 4 B 5+ x (formerly IrB 1.35 ) and Ir 5 B 4+ x (formerly IrB 1.1 ) and discovered that very thin films of both phases show a high hardness of 49.8 at a load of 0.49 N for Ir 4 B 5+ x and 43 GPa at 0.49 for Ir 5 B 4+ x . 3,30 With the exception of the hardness of those phases, very little is known about other properties, such as compressibility, of the iridium borides.…”

“…Up to now, already six binary iridium borides are known, namely, Ir 4 B 5+ x (formerly IrB 1.35 ), ,− Ir 5 B 4+ x (formerly IrB 1.1 ), ,, and the high and low temperature modification of Ir 4 B 3– x (formerly IrB 0.9 ). , These phases were synthesized via high temperature syntheses by Aronsson et al , and by Rogl et al More recently, Zeiringer et al reinvestigated the chemical compositions and structures of these iridium borides and suggested a slightly different labeling for a more suitable specification of the phase width . In 2016, Xie et al successfully used a mechanochemical approach to synthesize two new iridium borides, namely, IrB 2 and IrB . Rau et al and Latini et al investigated the hardness of Ir 4 B 5+ x (formerly IrB 1.35 ) and Ir 5 B 4+ x (formerly IrB 1.1 ) and discovered that very thin films of both phases show a high hardness of 49.8 at a load of 0.49 N for Ir 4 B 5+ x and 43 GPa at 0.49 for Ir 5 B 4+ x . , With the exception of the hardness of those phases, very little is known about other properties, such as compressibility, of the iridium borides.…”

Oxygen Interaction with Hexagonal OsB2 at High Temperature

“…This significantly limited their useful applications. Recent work on the synthesis and properties of ReB 2 , OsB 2 , and IrB 2 compounds have shown them to have remarkable mechanical properties, such as high hardness and stiffness, but the stability of these compounds upon exposure to oxygen‐containing species remained uncertain . It was reported that interaction of ReB 2 with water present in air, at RT, led to the formation of perrhenic acid [Re 2 O 7 (OH 2 ) 2 ] followed by a complete degradation of the mechanical properties of the material .…”