Porous graphite fabricated by liquid metal dealloying of silicon carbide
Porous graphite fabricated by liquid metal dealloying of silicon carbide
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DOI：
10.1016/j.carbon.2020.04.028
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发表时间：
2020-09-15
期刊：
影响因子：
10.9
通讯作者：
Erlebacher, J.
中科院分区：
文献类型：
--
作者：
Greenidge, G.;Erlebacher, J.
采用SiC在锗熔体中脱合金，然后挖掘Ge相的方法制备多孔石墨。去合金化是一种技术，通过从均匀合金中选择性溶解一种或多种组分来生产纳米多孔材料。在这里，液态金属脱合金（LMD）过程中扩展到非金属前体，表明碳化物衍生的碳（CDC）可以通过该过程制造。脱合金深度，浓度分布和长度尺度的脱合金组织进行了检查，因为它们随浸泡时间和温度的变化。脱合金深度随时间的变化而变化，脱合金界面附近锗中Si浓度增加。这些观察结果与在移动界面的液体锗侧中的速率限制的动力学是一致的。然而，所测量的2.4-2.8 eV的活化势垒太高，与液相中的扩散不一致，因此我们提出了一种机制，其中Si扩散受到脱合金界面附近的不饱和碳键的阻碍。多孔石墨表现出三维连通性和高结晶度，在最高温度下脱合金的样品的I（D）/I（G）比为0.3。
Porous graphite was prepared by dealloying SiC in molten germanium, and then excavating the Ge phase. Dealloying is a technique whereby nanoporous materials are produced via the selective dissolution of one or more components from a homogeneous alloy. Here, the liquid metal dealloying (LMD) process was extended to non-metal precursors, demonstrating that carbide-derived carbons (CDCs) can be fabricated by this process. The dealloying depth, concentration profile and length scale of the dealloyed microstructure were examined as they varied with immersion times and temperatures. The dealloying depthhvaried with time ash ∼ t1/2and we also observed a build-up of Si concentration in the germanium near the dealloying interface. These observations are consistent with kinetics that are rate-limiting in the liquid germanium side of the moving interface. However, the measured activation barrier of 2.4–2.8 eV was too high to be consistent with diffusion in the liquid phase, so instead we propose a mechanism in which Si diffusion is impeded by unsaturated carbon bonds near the dealloying interface. The porous graphite exhibited three-dimensional connectivity and a high degree of crystallinity, with an I(D)/I(G) ratio of 0.3 for samples dealloyed at the highest temperatures.