ARC Research Hub for Graphene Enabled Industry Transformation publications
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Browsing ARC Research Hub for Graphene Enabled Industry Transformation publications by Author "Aakyiir, M."
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Item Metadata only 3D printing interface-modified PDMS/MXene nanocomposites for stretchable conductors(Elsevier, 2022) Aakyiir, M.; Tanner, B.; Yap, P.L.; Rastin, H.; Tung, T.T.; Losic, D.; Meng, Q.; Ma, J.Additive manufacturing has rapidly evolved over recent years with the advent of polymer inks and those inks containing novel nanomaterials. The compatibility of polymer inks with nanomaterial inks remains a great challenge. Simple yet effective methods for interface improvement are highly sought-after to significantly enhance the functional and mechanical properties of printed polymer nanocomposites. In this study, we developed and modified a Ti3C2 MXene ink with a siloxane surfactant to provide compatibility with a polydimethylsiloxane (PDMS) matrix. The rheology of all the inks was investigated with parameters such as complex modulus and viscosity, confirming a self-supporting ink behaviour, whilst Fourier-transform infrared spectroscopy exposed the inks’ reaction mechanisms. The modified MXene nanosheets have displayed strong interactions with PDMS over a wide strain amplitude. An electrical conductivity of 6.14 × 10−2 S cm−1 was recorded for a stretchable nanocomposite conductor containing the modified MXene ink. The nanocomposite revealed a nearly linear stress-strain relationship and a maximum stress of 0.25 MPa. Within 5% strain, the relative resistance change remained below 35% for up to 100 cycles, suggesting high flexibility, conductivity and mechanical resilience. This study creates a pathway for 3D printing conductive polymer/nanomaterial inks for multifunctional applications such as stretchable electronics and sensors.Item Metadata only A new method for preparation of functionalized graphene and its epoxy nanocomposites(Elsevier, 2020) Naeem, M.; Kuan, H.C.; Michelmore, A.; Meng, Q.; Qiu, A.; Aakyiir, M.; Losic, D.; Zhu, S.; Ma, J.Organic solvents are often used to prepare epoxy/graphene nanocomposites. In this study a graphene precursor is developed, which in epoxy at 200 °C is able to directly exfoliate into three classes of graphene platelets: large, single-layer sheets, medium sized sheets with 5.2 ± 1.95 nm in thickness, and smaller 0.5–1.0 nm thick sheets of 200–500 nm in lateral dimension, with a Raman ID/IG ratio of 0.177. The yield of single-layer graphene is 41.45%. Due to oxygen-containing groups on the surface, these sheets are named functionalized graphene platelets. Platelet films of ~10 μm in thickness have an electrical conductivity of 978.65 ± 79.44 S/cm. A percolation threshold of electrical conductivity is observed at 0.80 vol% for epoxy/graphene nanocomposites. The composites show highly improved mechanical and dynamic thermo-mechanical properties. At 1.03 vol%, the nanocomposite has a fracture energy release rate of 850.78 ± 58.00 J m−2 corresponding to an increase of 170.61% over neat epoxy.Item Metadata only Electrically and thermally conductive elastomer by using MXene nanosheets with interface modification(© 2020 Elsevier B.V. All rights reserved., 2020) Aakyiir, M.; Yu, H.; Araby, S.; Ruoyu, W.; Michelmore, A.; Meng, Q.; Losic, D.; Choudhury, N.R.; Ma, J.It is a challenge to compound hydrophilic MXene nanosheets with hydrophobic elastomers for various applications such as stretchable devices. In this work, Ti3C2Tx MXene nanosheets of 3.5 ± 1.0 nm in thickness were chemically modified by a facile method to enhance compatibility with a common elastomer, nitrile butadiene rubber (NBR). X-ray photoelectron spectroscopy showed the presence of nitrogen in the MXene through the modification by allylamine, whilst Raman spectroscopy revealed an increase in =O groups, exposing more reactive sites on the nanosheet surface. Fourier transform infrared spectroscopy indicated the disappearance of –C=C bonds in the nanocomposites as well as the breakage of –C≡N bonds, confirming that allylamine bridged MXene nanosheets with the matrix molecules. X-ray diffraction study showed the complete exfoliation of nanosheets in the elastomer matrix at 2.0 vol%, as confirmed by TEM micrographs. At 14.0 vol% MXene, the Young’s modulus, tensile strength and thermal conductivity of NBR were improved by 700, 240 and 440%, respectively. A percolation threshold of electrical conductivity was obtained at 3.9 vol% of MXene while thermal conductivity at 19.6 vol% – 1.01 W·m−1K−1 – outperformed previous elastomer nanocomposites containing boron nitride, zinc oxide, graphene nanoplatelets and alumina.Item Metadata only Maximized crystal water content and charge-shielding effect in layered vanadate render superior aqueous zinc-ion battery(Elsevier, 2021) Yu, H.; Aakyiir, M.; Xu, S.; Whittle, J.D.; Losic, D.; Ma, J.Emerging as a promising candidate for grid-scale energy storage, aqueous zinc-ion batteries are challenged by both sluggish Zn²⁺ migration kinetics and poor cyclic stability of cathode materials. Herein, a maximized crystal water content of 14.8 wt% is reported for layered Na₅V₁₂O₃₂·11.9H₂O as the new cathode material. Such a content has enlarged the lattice space up to 12.75 Å providing spacious channels for rapid Zn²⁺ migration. The charge-shielding effect of crystal water alleviates the electrostatic interactions between Zn²⁺ and the cathode framework, enhancing ionic conductivity. The density functional theory calculation reveals that the high crystal water content facilitates the electrical conductivity. These should promote the Zn²⁺ migration kinetics and cyclic stability. Through characterizations by ex situ X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure analysis, the high crystal water content is found to associate with two-electron redox reactions during Zn²⁺ (de)intercalation. As a result, the Na₅V₁₂O₃₂·11.9H₂O cathode presents a reversible capacity of 430.52 mA h/g at 0.1 A/g with 103.7% retention of initial capacity over 3,862 cycles at 1 A/g.