Tailoring of the thermal expansion of Cr2(Alx,Ge1-x)C phases
Tailoring of the thermal expansion of Cr2(Alx,Ge1-x)C phases
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DOI：
10.1016/j.jeurceramsoc.2012.10.008
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发表时间：
2013-04-01
影响因子：
5.7
通讯作者：
Barsoum, Michel W.
中科院分区：
文献类型：
--
作者：
Cabioch, Thierry;Eklund, Per;Barsoum, Michel W.
本文报道了Cr-2（Al-x，Ge_（1-x））C系中端元和固溶体化合物的热膨胀系数。研究的所有样品基本上是纯相的Cr2 AlxGe 1-xC，除了Cr2 GeC样品，其中含有相当大一部分的Cr 5Ge 3Cx。在25-800 ℃温度范围内进行的X射线衍射显示，面内热膨胀基本上保持恒定在约14 +/- 1 × 10（-6）K-1，而与Al含量无关。随着Al含量的增加，c轴的热膨胀从Cr2 GeC的17 +/- 1 × 10（-6）K-1单调降低到12 +/- 1 × 10（-6）K-1。在Cr-2（Al-0.75，Ge-0.25）C成分附近，沿两个方向的热膨胀系数沿着相等;这是使热残余应力最小化的有用性质。因此，这项研究表明，固溶体方法是一种调整物理性质，如热膨胀的途径。为了完整性，我们还包括Cr 5Ge 3Cx相的结构描述，这是以前报道过的，但没有很好的记录。其空间群为P6（3）/mcm，晶格常数a和c分别为7.14和4.88埃。我们还测量了Cr 5Ge 3Cx相的热膨胀系数。它们沿a轴和c轴分别为16.3 × 10（-6）K-1和28.4 × 10（-6）K-1（沿着）。因此，Cr 5Ge 3Cx的热膨胀系数是高度各向异性的，并且显著大于Cr-2（Al-x，Ge 1-x）C相的热膨胀系数。(C)2012爱思唯尔有限公司保留所有权利。
We report thermal expansion coefficients of the end members and solid-solution compounds in the Cr-2(Al-x,Ge1-x)C system. All samples studied were essentially phase-pure Cr2AlxGe1-xC except the Cr2GeC sample, which contained a substantial fraction of Cr5Ge3Cx. X-ray diffraction performed in the 25-800 degrees C temperature range shows that the in-plane thermal expansion remains essentially constant at about 14 +/- 1 x 10(-6) K-1 irrespective of Al content. The thermal expansion of the c axis decreases monotonically from 17 +/- 1 x 10(-6) K-1 for Cr2GeC to similar to 12 +/- 1 x 10(-6) K-1 with increasing Al content. At around the Cr-2(Al-0.75,Ge-0.25)C composition, the thermal expansion coefficients along the two directions are equal; a useful property to minimize thermal residual stresses. This study thus demonstrates that a solid-solution approach is a route for tuning a physical property like the thermal expansion. For completeness, we also include a structure description of the Cr5Ge3Cx phase, which has been reported before but is not well documented. Its space group is P6(3)/mcm and its a and c lattice parameters are 7.14 angstrom and 4.88 angstrom, respectively. We also measured the thermal expansion coefficients of the Cr5Ge3Cx phase. They are found to be 16.3 x 10(-6) K-1 and 28.4 x 10(-6) K-1 along the a and c axes, respectively. Thus, the thermal expansion coefficients of Cr5Ge3Cx are highly anisotropic and considerably larger than those of the Cr-2(Al-x,Ge1-x)C phases. (C) 2012 Elsevier Ltd. All rights reserved.