Synthesis and characterization of the atomic laminate Mn2AlB2
Synthesis and characterization of the atomic laminate Mn2AlB2
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DOI：
10.1016/j.jeurceramsoc.2018.07.051
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发表时间：
2018-12
影响因子：
5.7
通讯作者：
S. Kota;Yexiao Chen;Jiayi Wang;S. May;M. Radovic;M. Barsoum
中科院分区：
文献类型：
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作者：
S. Kota;Yexiao Chen;Jiayi Wang;S. May;M. Radovic;M. Barsoum
在此，我们通过在真空下对锰、铝和硼粉末混合物进行反应热压，合成了致密、主要是单相多晶的 Mn2AlB2 三元化合物样品。 Mn2AlB2 的维氏硬度为 8.7GPa，对于过渡金属硼化物来说相对较软，并且压痕拐角处没有主要裂纹。 300°K 时的杨氏模量和剪切模量分别为 243 GPa 和 102 GPa，具有相当的刚性。泊松比经计算为 0.19。考虑到晶粒尺寸（1-15μm），样品的抗压强度为 1.24±0.1GPa，相当坚固。 300 K 时的电阻率约为 5 μΩm，并在冷却时线性下降。在0.0036 K−1时，电阻率温度系数与MoAlB相比相对较高。还发现，从 298 到 1173 K，平均线性热膨胀系数相对较高，为 18.6 × 10-6K−1。Mn2AlB2 在 ∼1379 K 以上时不稳定。虽然 Mn2AlB2 无法用传统刀具加工，但有趣的是，高速硬质合金刀具很容易穿透表面，而不会出现裂纹或碎裂。几毫米——然后停下来。
Herein, we synthesize dense, predominantly single-phase polycrystalline samples of the Mn2AlB2ternary compound, using reactive hot-pressing of manganese, aluminum, and boron powder mixtures under vacuum. With a Vickers hardness of 8.7 GPa, Mn2AlB2is relatively soft for a transition metal boride and lacked dominant cracks at the corners of the indentations. With Young’s and shear moduli of 243 GPa and 102 GPa at 300 K, respectively, it is reasonably stiff. The Poisson’s ratio is calculated to be 0.19. With compressive strengths of 1.24 ± 0.1 GPa, the samples were quite strong considering the grain size (1–15 μm). The electrical resistivity at 300 K was ∼5 μΩm and decreased linearly upon cooling. At 0.0036 K−1, the temperature coefficient of resistivity was relatively high compared to MoAlB. The average linear thermal expansion coefficient was also found to be relatively high at 18.6 × 10-6K−1from 298 to 1173 K. Mn2AlB2was not thermally stable above ∼1379 K. While Mn2AlB2was not machinable with conventional tooling, intriguingly, high-speed carbide tools bits readily penetrate the surface – with no cracking or chipping for a few millimeters – before stopping.