Effect of Electron Beam Damage on Polymer-based Materials for Additive Manufacturing

Abstract number
629
Event
European Microscopy Congress 2020
DOI
10.22443/rms.emc2020.629
Corresponding Email
[email protected]
Session
PSA.8 - Microscopy in industrial applications
Authors
Ms. L. M. Valencia (1), Ms. M. de la Mata (1), Ms. M. Herrera (1), Mrs. S. I. Molina (1)
Affiliations
1. Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, IMEYMAT, Facultad de Ciencias, Universidad de Cádiz, Campus Río San Pedro s/n, 11510
Keywords

Keywords: additive manufacturing, diffraction, EELS, polymers, radiation damage, TEM,  

Abstract text

Nowadays, Additive Manufacturing (AM) technologies find applications in a wide variety of fields including medicine or automotive [1]. AM computer controlled processes allow to build 3D customized objects by depositing the material layer-upon-layer. The continuous growth of these technologies promotes the development of materials that meet the requirements of the fabrication methods while providing advanced functionalities. Among these materials, it is worth highlighting polymers and polymer-based composites due to their versatility. The introduction of nano-additives in polymer matrices and blends has been reported to improve their functional properties, such as tensile strength, electrical conductivity or UV absorption [2]. Importantly, Transmission Electron Microscopy (TEM) techniques can play an essential role in the development of novel or improved materials for AM, as they provide relevant information at the nanometer and atomic scale to understand and correlate the material structure and its properties.

However, analyzing polymer-based materials by TEM techniques is challenging. The interaction of electrons with soft materials induces different types of damage which may generate chemical and structural changes in the specimen [3]. Consequently, the resolution limit achievable depends, among other parameters, on the total electron dose to which they can be exposed before changing [4]. Therefore, understanding the electron beam damage in these materials is essential to allow a careful study avoiding possible artifacts. 

It is well-known that the chemical changes on a specimen during TEM analyses can be monitored by using Electron Energy Loss Spectroscopy (EELS) [5]. With this technique, it is possible to observe thickness variations of the specimen due to degradation or contamination during the measurements, changes at the characteristic peaks of constituents due to alterations of the chemical structure, etc. Moreover, the polymer structural degradation can be analyzed by means of electron diffraction. Radiation damage causes the fading of diffraction rings or spots which allows studying the effect of the accumulated dose in the diffraction patterns [6].

In this work, we examine the effect of electron beam damage in different polymers by studying the electron diffraction and low-loss and core-loss EELS signals with varying exposure time and electron dose. In particular, the material of interest consists of a composite formed by an acrylic resin working as matrix and inorganic nanoparticles, such as WS2, as additive, to be used in Stereolithography (SLA), an AM technique. Preliminary studies show variations in the intensity of the diffraction rings. We evaluate the feasibility of using cross-correlated diffraction measurements to quantify the critical electron dose and exposure time thresholds preventing the material degradation. Additionally, we will present EELS experiments to analyze variations on the ᴨ to ᴨ* and (ᴨ+σ) to (ᴨ+σ)* transitions observable at the low loss region and also on the fine structure at the carbon K-edge of core-loss signal, to examine the induced beam damage [7]. 

References

References

[1]         I. Gibson, D. Rosen, and B. Stucker, Additive Manufacturing Technologies. 2019.

[2]         A. P. Kumar et al, “Nanoscale particles for polymer degradation and stabilization-Trends and future perspectives,” Prog. Polym. Sci., vol. 34, no. 6, pp. 479–515, 2009.

[3]         R. F. Egerton, “Radiation damage to organic and inorganic specimens in the TEM,” Micron, vol. 119, no. January, pp. 72–87, 2019.

[4]         N. Jiang and J. C. H. Spence, “On the dose-rate threshold of beam damage in TEM,” Ultramicroscopy, vol. 113, pp. 77–82, 2012.

[5]         P. K. Singh, B. R. Venugopal, and D. R. Nandini, “Effect of electron beam irradiation on polymers,” J. Mod. Mater., vol. 5, no. 1, pp. 24–33, 2018.

[6]         Z. J. W. A. Leijten et al, “Quantitative Analysis of Electron Beam Damage in Organic Thin Films,” J. Phys. Chem. C, vol. 121, no. 19, pp. 10552–10561, 2017.

[7]      Acknowledgments: Projects: TEC2017-86102-C2-2-R, NANOCOMP, 3DMATFUN. INNANOMAT group TEP-946. Co-funding from UE. DME-SC-ICyT-UCA.