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Mechanical properties and the evolution of matrix molecules in PTFE upon irradiation with MeV alpha particles

机译：MeVα粒子辐照后PTFE中的力学性能和基体分子的演变

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The morphology, chemical composition, and mechanical properties in the surface region of alpha-irradiated polytetrafluoroethylene (PTFE) have been examined and compared to unirradiated specimens. Samples were irradiated with 5.5 MeV He-4(2+) ions from a tandem accelerator to doses between 1 x 10(6) and 5 x 10(10) Rad. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS), using a 20 keV C-60(+) source, was employed to probe chemical changes as a function of a dose. Chemical images and high resolution spectra were collected and analyzed to reveal the effects of a particle radiation on the chemical structure. Residual gas analysis (RGA) was utilized to monitor the evolution of volatile species during vacuum irradiation of the samples. Scanning electron microscopy (SEM) was used to observe the morphological variation of samples with increasing a particle dose, and nanoindentation was engaged to determine the hardness and elastic modulus as a function of alpha dose. The data show that PTFE nominally retains its innate chemical structure and morphology at alpha doses < 10(9) Rad. At alpha doses >= 10(9) Rad the polymer matrix experiences increased chemical degradation and morphological roughening which are accompanied by increased hardness and declining elasticity. At alpha doses > 10(10) Rad the polymer matrix suffers severe chemical degradation and material loss. Chemical degradation is observed in ToF-SIMS by detection of ions that are indicative of fragmentation, unsaturation, and functionalization of molecules in the PTFE matrix. The mass spectra also expose the subtle trends of crosslinking within the alpha-irradiated polymer matrix. ToF-SIMS images support the assertion that chemical degradation is the result of alpha particle irradiation and show morphological roughening of the sample with increased a dose. High resolution SEM images more clearly illustrate the morphological roughening and the mass loss that accompanies high doses of alpha particles. RGA confirms the supposition that the outcome of chemical degradation in the PTFE matrix with continuing irradiation is evolution of volatile species resulting in morphological roughening and mass loss. Finally, we reveal and discuss relationships between chemical structure and mechanical properties such as hardness and elastic modulus. (c) 2006 Elsevier B.V. All rights reserved.
机译：已经检查了α-辐照的聚四氟乙烯（PTFE）表面区域的形态，化学成分和机械性能，并将其与未辐照的样品进行了比较。用串联加速器的5.5 MeV He-4（2+）离子辐照样品，剂量为1 x 10（6）和5 x 10（10）Rad之间。静态飞行时间二次离子质谱（ToF-SIMS），使用20 keV C-60（+）离子源，用于探测化学变化与剂量的关系。收集并分析了化学图像和高分辨率光谱，以揭示粒子辐射对化学结构的影响。残留气体分析（RGA）用于监测样品在真空照射过程中挥发性物质的释放。使用扫描电子显微镜（SEM）观察样品随颗粒剂量的增加而发生的形态变化，并采用纳米压痕确定硬度和弹性模量与α剂量的关系。数据显示，PTFE在<10（9）Rad的alpha剂量下名义上仍保留其固有的化学结构和形态。当alpha剂量> = 10（9）Rad时，聚合物基体经历增加的化学降解和形态粗糙，同时伴随着硬度增加和弹性下降。当alpha剂量> 10（10）Rad时，聚合物基体遭受严重的化学降解和材料损失。在ToF-SIMS中，通过检测表示PTFE基质中分子的断裂，不饱和和功能化的离子，观察到化学降解。质谱也暴露了在α-辐照的聚合物基质中交联的细微趋势。 ToF-SIMS图像支持以下观点：化学降解是α粒子辐照的结果，并显示了随着剂量增加样品的形态变粗糙。高分辨率SEM图像更清楚地说明了高剂量的α粒子伴随的形态粗糙和质量损失。 RGA证实了这样一种假设，即在连续照射下PTFE基质中化学降解的结果是挥发性物质的释放，导致形态变粗糙和质量损失。最后，我们揭示并讨论了化学结构与机械性能（例如硬度和弹性模量）之间的关系。 （c）2006 Elsevier B.V.保留所有权利。

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