Browsing by Author "Rahman, R"

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    Iron oxide-palladium core-shell nanospheres for ferromagnetic resonance-based hydrogen gas sensing
    (Elsevier, 2022-02-08) Khan, S; Lawler, NB; Bake, A; Rahman, R; Cortie, DL; Iyer, KS; Martyniuk, M; Kostylev, M
    Interfaces of ferromagnetic transition metals such as Iron, Cobalt, and Nickel with non-magnetic palladium are of interest due to their unique magnetic and spintronic properties. These interfaces enable ferromagnetic resonance (FMR) based sensing of hydrogen gas. In the present work, we synthesized Fe3O4–Pd core-shell nanospheres via a one-pot synthesis method using the thermal decomposition of Fe3+ acetylacetonate in the presence of a reducing agent to produce the Fe3O4 core, followed by the reduction of a Pd2+ precursor to form the pure Pd shell. We found that our in-situ synthesized core-shell nanostructure is magnetically active and shows excellent H2 gas sensing properties. The effect of reversible hydrogen gas absorption on the magnetism of Fe3O4–Pd core-shell nanospheres was investigated. The hydrogen-induced ferromagnetic-resonance (FMR) peak shift amounted to 30% of the peak linewidth for the virgin state of the sample. In addition, in the presence of hydrogen gas, we observed a fully reversible decrease in the FMR peak linewidth by about two times. This was accompanied by a nearly doubling of the FMR peak height. Response and recovery times of about 2 and 50 s, respectively, were extracted from the measurements. All the data was collected using a mix of just 3% hydrogen in a nitrogen carrier gas. © 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd.
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    Phonon engineering in thermal materials with nano-carbon dopants
    (AIP Publishing, 2024-06-01) Stamper, C; Cortie, DL; Nazrul-Islam, SMK; Rahman, R; Yu, DH; Yang, G; Al-Mamun, A; Wang, XL; Yue, ZJ
    The unique geometric and thermal properties of carbon nanoparticles (NPs)—including nanotubes, graphene, and nanodiamonds—have led to their use as additives in many composite material systems. In this review, we investigate the mechanisms behind the altered thermal conductivity (κ) of thermoelectric (TE) and other thermal materials that have been composited with carbon NPs. We provide a comprehensive overview and analysis of the relevant theoretical and applied literature, including a detailed review of the available thermal conductivity data across five common classes of TE materials (Bi2Te3 variants, skutterudites, metal–oxide, SnSe, Cu2Se) in combination with carbon additives, including graphene, nanotubes, carbon black, carbon fiber, and C60. We argue that the effectiveness of carbon NPs in reducing κ in TE composites generally arises due to a combination of the presence of the carbon NP interfaces and significant changes in the microstructure of the host material due to compositing, such as suppressed grain growth and the introduction of pores, dislocations, and strain. Carbon NPs themselves are effective phonon scatterers in TE composites due to a significant mismatch between their high-frequency phonon distribution and the lower-frequency phonon distribution of the host material. While carbon NP doping has proven itself as an effective way to increase the performance of TE materials, there is still a significant amount of work to do to precisely understand the fundamental thermal transport mechanisms at play. Rigorous material characterization of nanocomposites and spectroscopic studies of the precise lattice dynamics will greatly aid the development of a fully quantitative, self-consistent model for the thermal conductivity of carbon nanocomposites. © 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)
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    Ultra-small cobalt particles embedded in titania by ion beam synthesis: additional datasets including electron microscopy, neutron reflectometry, modelling outputs and particle size analysis
    (Elsevier, 2022-02) Bake, A; Rahman, R; Evans, PJ; Cortie, MB; Nancarrow, M; Abrudan, R; Radu, F; Khaydukov, Y; Causer, GL; Livesey, KL; Callori, SJ; Mitchell, DRG; Pastuovic, Z; Wang, XL; Cortie, DL
    This Data-in-brief article includes datasets of electron microscopy, polarised neutron reflectometry and magnetometry for ultra-small cobalt particles formed in titania thin films via ion beam synthesis. Raw data for polarised neutron reflectometry, magnetometry and the particle size distribution are included and made available on a public repository. Additional elemental maps from scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) are also presented. Data were obtained using the following types of equipment: the NREX and PLATYPUS polarised neutron reflectometers; a Quantum Design Physical Property Measurement System (14 T); a JEOL JSM-6490LV SEM, and a JEOL ARM-200F scanning transmission electron microscope (STEM). The data is provided as supporting evidence for the article in Applied Surface Science (A. Bake et al., Appl. Surf. Sci., vol. 570, p. 151068, 2021, DOI 10.1016/j.apsusc.2021.151068), where a full discussion is given. The additional supplementary reflectometry and modelling datasets are intended to assist future scientific software development of advanced fitting algorithms for magnetization gradients in thin films. Crown Copyright © 2021 - Open Access CC BY-NC-ND