It is generally accepted that inducing molecular alignment in a polymer precursor via mechanical stresses influences its graphitization during pyrolysis. However, our understanding of how variations of the imposed mechanics can influence pyrolytic carbon microstructure and functionality is inadequate. Developing such insight is consequential for different aspects of carbon MEMS manufacturing and applicability, as pyrolytic carbons are the main building blocks of MEMS devices. Herein, we study the outcomes of contrasting routes of stress-induced graphitization by providing a comparative analysis of the effects of compressive stress versus standard tensile treatment of PAN-based carbon precursors. The results of different materials characterizations (including scanning electron microscopy, Raman and X-ray photoelectron spectroscopies, as well as high-resolution transmission electron microscopy) reveal that while subjecting precursor molecules to both types of mechanical stresses will induce graphitization in the resulting pyrolytic carbon, this effect is more pronounced in the case of compressive stress. We also evaluated the mechanical behavior of three carbon types, namely compression-induced (CIPC), tension-induced (TIPC), and untreated pyrolytic carbon (PC) by Dynamic Mechanical Analysis (DMA) of carbon samples in their as-synthesized mat format. Using DMA, the elastic modulus, ultimate tensile strength, and ductility of CIPC and TIPC films are determined and compared with untreated pyrolytic carbon. Both stress-induced carbons exhibit enhanced stiffness and strength properties over untreated carbons. The compression-induced films reveal remarkably larger mechanical enhancement with the elastic modulus 26 times higher and tensile strength 2.85 times higher for CIPC compared to untreated pyrolytic carbon. However, these improvements come at the expense of lowered ductility for compression-treated carbon, while tension-treated carbon does not show any loss of ductility. The results provided by this report point to the ways that the carbon MEMS industry can improve and revise the current standard strategies for manufacturing and implementing carbon-based micro-devices.

中文翻译：

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拉伸和压缩应力在碳纳米纤维石墨化和性能中的不同作用

人们普遍认为，通过机械应力在聚合物前体中诱导分子排列会影响其在热解过程中的石墨化。然而，我们对强加力学的变化如何影响热解碳的微观结构和功能的理解是不够的。开发这种洞察力对于碳 MEMS 制造和适用性的不同方面具有重要意义，因为热解碳是 MEMS 设备的主要构建块。在此，我们通过对 PAN 基碳前驱体的压缩应力与标准拉伸处理的影响进行比较分析，研究了应力诱导石墨化的对比路线的结果。不同材料表征的结果（包括扫描电子显微镜、拉曼和 X 射线光电子光谱、以及高分辨率透射电子显微镜）表明，虽然使前体分子承受两种类型的机械应力会导致所得热解碳中的石墨化，但这种影响在压缩应力的情况下更为明显。我们还通过动态力学分析 (DMA) 评估了三种碳类型的机械行为，即压缩诱导 (CIPC)、张力诱导 (TIPC) 和未处理的热解碳 (PC) 的碳样品在其合成垫形式. 使用 DMA，确定了 CIPC 和 TIPC 薄膜的弹性模量、极限拉伸强度和延展性，并与未处理的热解碳进行比较。与未处理的碳相比，两种应力诱导碳都表现出增强的刚度和强度特性。与未处理的热解碳相比，CIPC 的压缩诱导薄膜显示出显着更大的机械增强，弹性模量高 26 倍，拉伸强度高 2.85 倍。然而，这些改进的代价是压缩处理碳的延展性降低，而拉伸处理的碳没有表现出任何延展性损失。本报告提供的结果指出了碳 MEMS 行业可以改进和修订当前用于制造和实施碳基微器件的标准策略的方法。而经过张力处理的碳没有显示出任何延展性损失。本报告提供的结果指出了碳 MEMS 行业可以改进和修订当前用于制造和实施碳基微器件的标准策略的方法。而经过张力处理的碳没有显示出任何延展性损失。本报告提供的结果指出了碳 MEMS 行业可以改进和修订当前用于制造和实施碳基微器件的标准策略的方法。