Boridene: Two-dimensional Mo4/3B2-x with ordered metal vacancies obtained by chemical exfoliation

Extensive research has been invested in two-dimensional (2D) materials, typically synthesized by exfoliation of van der Waals solids. One exception is MXenes, derived from the etching of constituent layers in transition metal carbides and nitrides. We report the experimental realization of boridene in the form of single-layer 2D molybdenum boride sheets with ordered metal vacancies, Mo4/3B2-xTz (where Tz is fluorine, oxygen, or hydroxide surface terminations), produced by selective etching of aluminum and yttrium or scandium atoms from 3D in-plane chemically ordered (Mo2/3Y1/3)2AlB2 and (Mo2/3Sc1/3)2AlB2 in aqueous hydrofluoric acid. The discovery of a 2D transition metal boride suggests a wealth of future 2D materials that can be obtained through the chemical exfoliation of laminated compounds.

Study on Low Cycle Fatigue and Tensile Behavior of Al 5083/CNT/MoB/Ni Hybrid Composite

The paper is on low cycle fatigue and tensile behavior of hybrid composite with Al5083 alloy as matrix material and different weight percentages of multi-walled carbon nanotube (CNT), molybdenum boride (MoB), and nickel (Ni) as reinforcements. Low cycle fatigue test is conducted loading with a stress ratio of 0.1 and maximum load of 50 kN. Both tensile properties and fatigue life for the composites are found to be increasing initially with increase in percentage weight of reinforcements up to a CNT weight percentage of 0.75. When the percentage of reinforcement further increases the properties show a decreasing trend. The scanning electron microscopy (SEM) of the ruptured fatigue specimen indicates that the increase in properties is due to grain size refinement and the decreasing trend is because of CNT cluster formation.

Study of Dry Sliding Wear and Immersion Corrosion on Al 5083 Reinforced With MWCNT, MoB, and Ni

Dry sliding wear and immersion corrosion behaviors of Al 5083-based hybrid composite reinforced with multiwalled carbon nanotube (MWCNT), Molybdenum boride (MoB) and nickel (Ni) are studied with different weight percentages. The reinforcement weight percentages of MWCNT ranges from 0 to 1.5, that of MoB from 1 to 4 and for Ni from 2 to 8. Dry sliding wear behavior at room temperature is studied using Pin on Disc by varying the sliding distances from 500 to 2000m, load from 10 to 40 N and sliding velocity from 0.25 to 1.75m/s. The wear studies revealed that there is a considerable decrease in wear rate for composites than the alloy material with increase in %wt of reinforcements for all test parameters. The worn surface analysis revealed that there are two types of wear mechanisms namely abrasive and adhesive. The uniform immersion corrosion tests also showed decreasing rate with increase in reinforcements.

Study of solidification pathway of a MoSiBTiC alloy by optical thermal analysis and in-situ observation with electromagnetic levitation

MoSiBTiC alloys are promising candidates for next-generation ultrahigh-temperature materials. However, the phase diagram of these alloys has been unknown. We have developed an ultrahigh-temperature thermal analyser based on blackbody radiation that can be used to analyse the melting and solidification of the alloy 67.5Mo–5Si–10B–8.75Ti–8.75 C (mol%). Furthermore, electromagnetic levitation (EML) was used for in-situ observation of solidification and microstructural study of the alloy. On the basis of the results, the following solidification pathway is proposed: Mo solid solution (Moss) begins to crystallize out as a primary phase at 1955 °C (2228 K) from a liquid state, which is followed by a (Moss+TiC) eutectic reaction starting at 1900 °C (2173 K). Molybdenum boride (Mo2B) phase precipitates from the liquid after the eutectic reaction; however, the Mo2B phase may react with the remaining liquid to form Moss and Mo5SiB2 (T2) as solidification proceeds. In addition, T2 also precipitates as a single phase from the liquid. The remaining liquid reaches the (Moss + T2 + TiC) ternary eutectic point at 1880 °C (2153 K), and the (Moss + T2 + Mo2C) eutectic reaction finally occurs at 1720 °C (1993 K). This completes the solidification of the MoSiBTiC alloy.

Prediction of phonon-mediated superconductivity in two-dimensional Mo2B2

We predict two new molybdenum boride monolayers as phonon-mediated superconductors with superconducting transition temperatures of 3.9 and 0.2 K.