Near-surface structure and residual stress in as-machined synthetic graphite
Near-surface structure and residual stress in as-machined synthetic graphite
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DOI：
10.1016/j.matdes.2018.08.041
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发表时间：
2018-12
影响因子：
8.4
通讯作者：
B. März;K. Jolley;Roger Smith;Houzheng Wu
中科院分区：
文献类型：
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作者：
B. März;K. Jolley;Roger Smith;Houzheng Wu
我们已经使用光学和电子显微镜和拉曼光谱研究的结构变化和残余应力引起的典型的工业机械加工和实验室抛光的合成石墨。在机加工和抛光表面上形成厚度高达35 nm的磨损层，给出相同的ID/IG比，证明石墨晶体细化从Laof ~110 nm下降到平均21 nm，但具有不同的残余压缩水平。对于抛光样品，结构变化仅限于近表面区域。在机加工的表面下，大孔填充有破碎的材料;石墨晶体被分裂成多层石墨烯单元，这些单元通过扭结重新排列。在35-40 μm的深度范围内，用La测量的亚表面区域石墨晶体细化与深度（z）呈指数关系。拉曼光谱中G带的正向位移表明，残余压缩伴随着顶部最高平均值约为2.5 GPa的细化，随后在细化区域内呈指数衰减;超过该深度，压缩线性下降至约200 μm的深度。原子模型的支持下，讨论了细化和残余压缩机制。
We have used optical and electron microscopy and Raman spectroscopy to study the structural changes and residual stress induced by typical industrial machining and laboratory polishing of a synthetic graphite. An abrasion layer of up to 35 nm in thickness formed on both machined and polished surfaces, giving the same ID/IGratios evidencing graphite crystal refinement from an Laof ~110 nm down to an average of 21 nm, but with different residual compression levels. For the as-polished sample, structural change was limited to the near surface region. Underneath the as-machined surface, large pores were filled with crushed material; graphite crystals were split into multi-layered graphene units that were rearranged through kinking. Graphite crystal refinement in the sub-surface region, measured byLa, showed an exponential relationship with depth (z) to a depth of 35–40 μm. The positive shift of the G band in the Raman spectrum indicates a residual compression accompanied by refinement with the highest average of ~2.5 GPa on top, followed by an exponential decay inside the refined region; beyond that depth, the compression decreased linearly down to a depth of ~200 μm. Mechanisms for the refinement and residual compression are discussed with the support of atomistic modelling.