title: Synthesis and Characterization of an Alumina Forming Nanolaminated Boride: MoAlB.
abstract: The 'MAlB' phases are nanolaminated, ternary transition metal borides that consist of a transition metal boride sublattice interleaved by monolayers or bilayers of pure aluminum. However, their synthesis and properties remain largely unexplored. Herein, we synthesized dense, predominantly single-phase samples of one such compound, MoAlB, using a reactive hot pressing method. High-resolution scanning transmission electron microscopy confirmed the presence of two Al layers in between a Mo-B sublattice. Unique among the transition metal borides, MoAlB forms a dense, mostly amorphous, alumina scale when heated in air. Like other alumina formers, the oxidation kinetics follow a cubic time-dependence. At room temperature, its resistivity is low (0.36-0.49 μΩm) and - like a metal - drops linearly with decreasing temperatures. It is also a good thermal conductor (35 Wm(-1)K(-1) at 26 °C). In the 25-1300 °C temperature range, its thermal expansion coefficient is 9.5 × 10(-6 )K(-1). Preliminary results suggest the compound is stable to at least 1400 °C in inert atmospheres. Moderately low Vickers hardness values of 10.6 ± 0.3 GPa, compared to other transition metal borides, and ultimate compressive strengths up to 1940 ± 103 MPa were measured at room temperature. These results are encouraging and warrant further study of this compound for potential use at high temperatures.
authors.affiliation: Drexel University, Department of Materials Science &Engineering, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Sankalp
authors.initials: S
authors.lastname: Kota
authors.affiliation: Centre for Nuclear Engineering, Department of Materials, Imperial College London, London, SW7 2AZ, United Kingdom.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Zapata-Solvas
authors.affiliation: Drexel University, Department of Mechanical Engineering and Mechanics, Philadelphia, 19104, United States.
authors.forename: Alexander
authors.initials: A
authors.lastname: Ly
authors.affiliation: Linköping University, Department of Physics, Chemistry and Biology (IFM), Linköping, SE-58183, Sweden.
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.affiliation: Drexel University, Department of Materials Science &Engineering, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Omar
authors.initials: O
authors.lastname: Elkassabany
authors.affiliation: Drexel University, Department of Materials Science &Engineering, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Amanda
authors.initials: A
authors.lastname: Huon
authors.affiliation: Centre for Nuclear Engineering, Department of Materials, Imperial College London, London, SW7 2AZ, United Kingdom.
authors.forename: William E
authors.initials: WE
authors.lastname: Lee
authors.affiliation: Linköping University, Department of Physics, Chemistry and Biology (IFM), Linköping, SE-58183, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Hultman
authors.affiliation: Drexel University, Department of Materials Science &Engineering, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Steve J
authors.initials: SJ
authors.lastname: May
authors.affiliation: Drexel University, Department of Materials Science &Engineering, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Michel W
authors.initials: MW
authors.lastname: Barsoum