This may be the author’s version of a work that was submitted/accepted for publication in the following source: Zhan, Haifei, Shang, Jing, Lü, Chaofeng, & Gu, Yuantong (2021) Tensile properties of functionalized carbon nanothreads. Nano Materials Science. This file was downloaded from: https://eprints.qut.edu.au/212511/ c 2021 Chongqing University This work is covered by copyright. Unless the document is being made available under a Creative Commons Licence, you must assume that re-use is limited to personal use and that permission from the copyright owner must be obtained for all other uses. If the docu- ment is available under a Creative Commons License (or other specified license) then refer to the Licence for details of permitted re-use. It is a condition of access that users recog- nise and abide by the legal requirements associated with these rights. 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If there is any doubt, please refer to the published source. https://doi.org/10.1016/j.nanoms.2021.06.006 Nano Materials Science xxx (xxxx) xxx Contents lists available at ScienceDirect Nano Materials Science journal homepage: www.keaipublishing.com/cn/journals/nano-materials-science/ Tensile properties of functionalized carbon nanothreads Haifei Zhan a,b,c,*, Jing Shang b, Chaofeng Lü a, Yuantong Gu b,c,** a Department of Civil Engineering, Zhejiang University, Hangzhou, 310058, PR China b School of Mechanical, Medical and Process Engineering, Queensland University of Technology (QUT), Brisbane, QLD, 4001, Australia c Center for Materials Science, Queensland University of Technology (QUT), Brisbane, QLD, 4001, Australia ARTICLE INFO ABSTRACT Keywords: Low dimensional sp3 carbon nanostructures have attracted increasing attention recently, due to their unique Carbon nanothread properties and appealing applications. Based on in silico studies, this work exploits the impacts from functional Functional group groups on the tensile properties of carbon nanothreads (NTH) – a new sp3 carbon nanostructure. It is found that Tensile deformation functional groups will alter the local bond configuration and induce initial stress concentration, which signifi- Stress concentration cantly reduces the fracture strain/strength of NTH. Different functional types lead to different local bond re- Molecular dynamics simulation configurations, and introduce different impacts on NTH. Further studies reveal that the tensile properties de- creases generally when the content of functional groups increases. However, some NTHs with higher content of functional groups exhibit higher fracture strain/strength than their counterparts with lower percentage. Such observations are attributed to the synergetic effects from the sample length, self-oscillation, and distribution of functional groups. Simulations show that the tensile behaviour of NTH with the same functional percentage differs when the distribution pattern varies. Overall, ethyl groups are found to induce larger degradation on the tensile properties of NTH than methyl and phenyl groups. This study provides a comprehensive understanding of the influence from functional groups, which should be beneficial to the engineering applications of NTH. 1. Introduction diamond, which is regarded as the hardest material in nature. Recent experimental works show that a two-dimensional (2D) diamond can be Low-dimensional carbon nanostructures are ideal building blocks for prepared based on bilayer graphene [5,6], which has been predicted with a broad range of applications due to their excellent physical and chemical excellent in-plane and out-of-plane mechanical properties [7,8]. properties [1], such as next generation devices, flexible electronics, and Besides 2D diamond, the one-dimensional (1D) sp3 bonded nano- high-performance materials. Carbon possesses three different hybridi- structures also attracted great attention [9]. Earlier works prepared zation states, including sp1,sp2, and sp3 bonds, these different types of C diamond nanowire or nanorod through reactive-ion etching (RIE) tech- bonds as well as their combination enable the existences of many nique [10,11] or chemical vapor deposition (CVD) method [12]. They different carbon nanostructures, ranging from zero to three-dimensional have been shown with good electrochemical properties, excellent elec- (3D). Among them, the sp2 carbon nanostructures, including fullerene, tron field emission, mechanical properties [13], and envisioned with carbon nanotube (CNT) and graphene, have received the most intensive appealing applications in biomedical fields. However, the ineffectiveness interests from academic and engineering communities in past decades. and challenges of the REI or CVD method have greatly impeded their The sp2 bonded carbon nanostructures normally have supreme in-plane research. Recently, researchers successfully synthesized an ultra-thin sp3 mechanical properties, for example, carbon nanotube or graphene is re- bonded 1D nanostructure, named as carbon nanothread (NTH), through ported with a Young's modulus up to 1 TPa [2,3]. However, their high-pressure (20 GPa) solid-state reaction of benzene at room temper- out-of-plane mechanical properties frequently fail the real engineering ature [14]. NTH is reported with a diameter less than 0.5 nm, such small requirements. For instance, the thin-wall carbon nanotube (CNT) suffers diameter leads to significant challenges for structural characterization from lateral flattening (or buckling), and the graphene layer can hardly [15,16]. Despite that, potential configuration of NTHs have been sys- maintain a flat configuration in experiments [4]. These circumstances tematically enumerated based on first principles calculations, including drive researchers to revisit the typical sp3 bonded carbon structure – the fully saturated (or degree-6) and partially saturated (or degree-4) * Corresponding author. Department of Civil Engineering, Zhejiang University, Hangzhou, 310058, PR China. ** Corresponding author. School of Mechanical, Medical and Process Engineering, Queensland University of Technology (QUT), Brisbane, QLD, 4001, Australia. E-mail addresses: [email protected] (H. Zhan), [email protected] (Y.–M.P.Q.-T.S.Issue.....-.N.response.K.X.accordingly.–>u. Gu). https://doi.org/10.1016/j.nanoms.2021.06.006 Received 8 May 2021; Accepted 15 June 2021 Available online xxxx 2589-9651/© 2021 Chongqing University. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. Please cite this article as: H. Zhan et al., Tensile properties of functionalized carbon nanothreads, Nano Materials Science , https://doi.org/10.1016/ j.nanoms.2021.06.006 H. Zhan et al. Nano Materials Science xxx (xxxx) xxx Fig. 1. Schematic view of the model. (a) The pristine NTH; (b) The NTH with randomly dispersed ethyl functional groups; (c) Comparisons of the radial distribution function gðrÞ for NTH with and without ethyl functional groups; (d) The potential energy trajectory during the relaxation for the NTH with different percentages of ethyl functional groups. structures [17,18]. Preliminary works report that NTH has tunable me- functionalization percentage is defined as the ratio between the number chanical properties [19–21] and thermal transport properties [22,23]. Its of the replaced H atoms (or the number of functional groups) and the non-smooth surface is shown to be beneficial for the applications as re- total H atoms. The C–C and C–H atomic interactions were described by inforcements for polymer nanocomposites [24] and carbon nanofibers the commonly used intermolecular reactive empirical bond order (AIR- [25–27], due to the high interfacial load transfer efficiency. EBO) potential, which was established based on different hydrocarbon Functionalization is one of the effective ways to improve the inter- configurations [30,31]. This potential has been shown to well reproduce facial load transfer efficiency for low dimensional nanostructures used in the thermal and mechanical properties of different carbon nanostructures composite structures. One of the advantages of NTH over CNT is that [32–34]. Recent works show that AIREBO potential can well predict the NTH possesses a fully hydrogenated surface, which enables a further mechanical properties NTHs compared with the density functional the- functionalization without introducing additional defects to the backbone ory calculations [35] or other NTHs with similar configuration [36]. To structure. It is commonly reported that functionalization will signifi- avoid the spurious high stress at high bond strain, the cut-off distance of cantly deteriorate the mechanical properties of CNT due to the C bond the AIREBO potential was chosen as 2.0 Å [37–39]. The NTH with and change from sp2 to sp3. In comparison, no such bond change will occur without ethyl groups share a similar radial distribution function profile for the NTH with functionalization, i.e., the C bonds remain as sp3. (Fig. 1c), suggesting that there is no obvious structural change in the Previous density functional theory calculations suggest that the NTH functionalized NTH. The stability