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118 results on '"Aslam, Zabeada"'

4. A nano-carbon route to rare earth free permanent magnetism

Author

Moorsom, Timothy, Alghamdi, Shoug, Stansill, Sean, Poli, Emiliano, Teobaldi, Gilberto, Beg, Marijan, Fangohr, Hans, Rogers, Matt, Aslam, Zabeada, Ali, Mannan, Hickey, Bryan J, and Cespedes, Oscar

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

High coercivity magnets are an important resource for renewable energy, electric vehicles and memory technologies. Most hard magnetic materials incorporate rare-earths such as neodymium and samarium, but the concerns about the environmental impact and supply stability of these materials is prompting research into alternatives. Here, we present a hybrid bilayer of cobalt and the nano-carbon molecule C60 which exhibits significantly enhanced coercivity with minimal reduction in magnetisation. We demonstrate how this anisotropy enhancing effect cannot be described by existing models of molecule-metal magnetic interfaces. We outline a new form of magnetic anisotropy, arising from asymmetric magneto-electric coupling in the metal-molecule interface. Because this phenomenon arises from pi-d hybrid orbitals, we propose calling this effect pi-anisotropy. While the critical temperature of this effect is currently limited by the rotational degree of freedom of the chosen molecule, C60, we describe how surface functionalisation would allow for the design of room-temperature, carbon based hard magnetic films., Comment: 16 pages, 4 figures

Published
2019
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6. Helical magnetic structure and the anomalous and topological Hall effects in epitaxial B20 Fe$_{1-y}$Co$_y$Ge films

Author

Spencer, Charles S., Gayles, Jacob, Porter, Nicholas A., Sugimoto, Satoshi, Aslam, Zabeada, Kinane, Christian J., Charlton, Timothy R., Freimuth, Frank, Chadov, Stanislav, Langridge, Sean, Sinova, Jairo, Felser, Claudia, Blügel, Stefan, Mokrousov, Yuriy, and Marrows, Christopher H.

Subjects
Condensed Matter - Materials Science
Abstract

Epitaxial films of the B20-structure alloy Fe$_{1-y}$Co$_y$Ge were grown by molecular beam epitaxy on Si (111) substrates. The magnetization varied smoothly from the bulk-like values of one Bohr magneton per Fe atom for FeGe to zero for non-magnetic CoGe. The chiral lattice structure leads to a Dzyaloshinskii-Moriya interaction (DMI), and the films' helical magnetic ground state was confirmed using polarized neutron reflectometry measurements. The pitch of the spin helix, measured by this method, varies with Co content $y$ and diverges at $y \sim 0.45$. This indicates a zero-crossing of the DMI, which we reproduced in calculations using first principle methods. We also measured the longitudinal and Hall resistivity of our films as a function of magnetic field, temperature, and Co content $y$. The Hall resistivity is expected to contain contributions from the ordinary, anomalous, and topological Hall effects. Both the anomalous and topological Hall resistivities show peaks around $y \sim 0.5$. Our first principles calculations show a peak in the topological Hall constant at this value of $y$, related to the strong spin-polarisation predicted for intermediate values of $y$. Half-metallicity is predicted for $y = 0.6$, consistent with the experimentally observed linear magnetoresistance at this composition. Whilst it is possible to reconcile theory with experiment for the various Hall effects for FeGe, the large topological Hall resistivities for $y \sim 0.5$ are much larger then expected when the very small emergent fields associated with the divergence in the DMI are taken into account.

Published
2018
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19. Electron transparent nanotubes reveal crystallization pathways in confinement

Author

Galloway, Johanna M., primary, Aslam, Zabeada P., additional, Yeandel, Stephen R., additional, Kulak, Alexander, additional, Ilett, Martha A., additional, Kim, Yi-Yeoun, additional, Bejarano-Villafuerte, Angela, additional, Pokroy, Boaz, additional, Drummond-Brydson, Rik M., additional, Freeman, Colin L., additional, Harding, John H., additional, Kapur, Nikil, additional, and Meldrum, Fiona C., additional

Published
2023
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25. Polyamines Promote Aragonite Nucleation and Generate Biomimetic Structures.

Author

Nahi, Ouassef, Kulak, Alexander N., Zhang, Shuheng, He, Xuefeng, Aslam, Zabeada, Ilett, Martha A., Ford, Ian J., Darkins, Robert, and Meldrum, Fiona C.

Subjects
CALCIUM carbonate, CALCITE, ARAGONITE, SMALL molecules, POLYAMINES, MAGNESIUM ions, VATERITE
Abstract

Calcium carbonate biomineralization is remarkable for the ability of organisms to produce calcite or aragonite with perfect fidelity, where this is commonly attributed to specific anionic biomacromolecules. However, it is proven difficult to mimic this behavior using synthetic or biogenic anionic organic molecules. Here, it is shown that cationic polyamines ranging from small molecules to large polyelectrolytes can exert exceptional control over calcium carbonate polymorph, promoting aragonite nucleation at extremely low concentrations but suppressing its growth at high concentrations, such that calcite or vaterite form. The aragonite crystals form via particle assembly, giving nanoparticulate structures analogous to biogenic aragonite, and subsequent growth yields stacked aragonite platelets comparable to structures seen in developing nacre. This mechanism of polymorph selectivity is captured in a theoretical model based on these competing nucleation and growth effects and is completely distinct from the activity of magnesium ions, which generate aragonite by inhibiting calcite. Profiting from these contrasting mechanisms, it is then demonstrated that polyamines and magnesium ions can be combined to give unprecedented control over aragonite formation. These results give insight into calcite/aragonite polymorphism and raise the possibility that organisms may exploit both amine‐rich organic molecules and magnesium ions in controlling calcium carbonate polymorph. [ABSTRACT FROM AUTHOR]

Published
2023
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30. Exploring High Aspect Ratio Gold Nanotubes as Cytosolic Agents: Structural Engineering and Uptake into Mesothelioma Cells

Author

Ye, Sunjie, primary, Azad, Arsalan A., additional, Chambers, Joseph E., additional, Beckett, Alison J., additional, Roach, Lucien, additional, Moorcroft, Samuel C. T., additional, Aslam, Zabeada, additional, Prior, Ian A., additional, Markham, Alexander F., additional, Coletta, P. Louise, additional, Marciniak, Stefan J., additional, and Evans, Stephen D., additional

Published
2020
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31. One‐Step Preparation of Biocompatible Gold Nanoplates with Controlled Thickness and Adjustable Optical Properties for Plasmon‐Based Applications

Author

Ye, Sunjie, primary, Connell, Simon D., additional, McLaughlan, James R., additional, Roach, Lucien, additional, Aslam, Zabeada, additional, Chankhunthod, Navadecho, additional, Brown, Andy P., additional, Brydson, Rik, additional, Bushby, Richard J., additional, Critchley, Kevin, additional, Coletta, P. Louise, additional, Markham, Alexander F., additional, and Evans, Stephen D., additional

Published
2020
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32. π -anisotropy: A nanocarbon route to hard magnetism

Author

Moorsom, Timothy, primary, Alghamdi, Shoug, additional, Stansill, Sean, additional, Poli, Emiliano, additional, Teobaldi, Gilberto, additional, Beg, Marijan, additional, Fangohr, Hans, additional, Rogers, Matt, additional, Aslam, Zabeada, additional, Ali, Mannan, additional, Hickey, B. J., additional, and Cespedes, Oscar, additional

Published
2020
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34. Fe–N-Doped Mesoporous Carbon with Dual Active Sites Loaded on Reduced Graphene Oxides for Efficient Oxygen Reduction Catalysts

Author

Zhang, Chao, Liu, Jun, Ye, Yixing, Aslam, Zabeada, Brydson, Rik, and Liang, Changhao

Abstract

Transition metal/nitrogen/carbon (M-N/C) catalysts are considered as one of the most promising candidates to replace Pt/C catalysts for oxygen reduction reactions (ORRs). Here, we have designed novel reduced graphene oxide (rGO)-supported Fe–N-doped carbon (Fe–N–C/rGO) catalysts via simple pyrolysis of polypyrrole (Ppy)–FeO–GO composites. The as-prepared catalysts induced an onset potential of 0.94 V and a half-wave potential of 0.81 V in alkaline solutions, which is much better than those of the counterpart N–C and N–C/rGO catalysts and comparable to that of Pt/C catalysts. Moreover, the Fe–N–C/rGO catalysts showed improved durability and higher tolerance against methanol crossover than Pt/C in alkaline solutions. This superior ORR performance can be ascribed to the combined catalytic effect of both Fe-based nanoparticles (Fe3O4, Fe4C) and Fe–Nxsites, as well as fast mass transfer and accessible active sites benefiting from the mesoporous structure and high specific surface area. This work provides new insight for synthesis of a more promising nonplatinum electrocatalyst for metal–air batteries and fuel-cell applications.

Published
2024
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35. Helical magnetic structure and the anomalous and topological Hall effects in epitaxial B20 Fe1−yCoyGe films

Author

Spencer, Charles S., primary, Gayles, Jacob, additional, Porter, Nicholas A., additional, Sugimoto, Satoshi, additional, Aslam, Zabeada, additional, Kinane, Christian J., additional, Charlton, Timothy R., additional, Freimuth, Frank, additional, Chadov, Stanislav, additional, Langridge, Sean, additional, Sinova, Jairo, additional, Felser, Claudia, additional, Blügel, Stefan, additional, Mokrousov, Yuriy, additional, and Marrows, Christopher H., additional

Published
2018
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42. Boron-Mediated Nanotube Morphologies

Author

Nicholls, Rebecca J., primary, Aslam, Zabeada, additional, Sarahan, Michael C., additional, Koós, Antal, additional, Yates, Jonathan R., additional, Nellist, Peter D., additional, and Grobert, Nicole, additional

Published
2012
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47. Facile, fast, and inexpensive synthesis of monodisperse amorphous Nickel-Phosphide nanoparticles of predefined size

Author

Mandel, Karl, primary, Dillon, Frank, additional, Koos, Antal A., additional, Aslam, Zabeada, additional, Jurkschat, Kerstin, additional, Cullen, Frank, additional, Crossley, Alison, additional, Bishop, Hugh, additional, Moh, Karsten, additional, Cavelius, Christian, additional, Arzt, Eduard, additional, and Grobert, Nicole, additional

Published
2011
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48. A facile route to self-assembled Hg//MoSI nanowire networks

Author

Nicolosi, Valeria, primary, Aslam, Zabeada, additional, Sader, Kasim, additional, Hughes, Gareth M., additional, Vengust, Damjan, additional, Young, Neil P., additional, Doole, Ron, additional, Mihailovic, Dragan, additional, Bleloch, Andrew L., additional, Kirkland, Angus I., additional, Grobert, Nicole, additional, and Nellist, Peter D., additional

Published
2010
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49. CLOSE-COUPLED GAS ATOMIZATION: HIGH-FRAME-RATE ANALYSIS OF SPRAY-CONE GEOMETRY.

Author

Mullis, Andrew M., Adkins, Nicholas J. E., Aslam, Zabeada, McCarthy, I., and Cochrane, Robert F.

Subjects
ATOMIZATION, ATOMIZERS, SPRAYING, SPRAY nozzles, DIGITAL video, RADIATION
Abstract

The geometry of the spray cone during atomization of Ni31.5 Al68.5 in a close-coupled gas atomizer operating with a generic die and nozzle design has been studied utilizing high-speed digital video techniques. Details of the region extending 5 cm from the spray nozzle at frame rates of up to 18.000 frames/s were recorded. The material was sprayed at a temperature ~1.830 K (corresponding to a superheat ~200 K), wherein sufficient thermal radiation was emitted for images to be recorded without any additional lighting. In order to quantitatively analyze the large number of still frames that result (up to 65,536), image processing routines capable of automating this process have been developed and used to measure the optical brightness and the position of the optical-intensity maximum of the material passing though a narrow window at a fixed distance from the nozzle tip. The results of this analysis show that the spray cone consists of a jet that processes around the center axis of the atomizer in a regular manner at a frequency ~360 Hz. In order to understand the origin of this motion, further experiments were conducted with a laboratory-scale analogue atomizer which atomizes a water jet. It was found that the frequency of precession is essentially independent of the atomizing-gas pressure, but does depend upon the geometry of both the die and nozzle. [ABSTRACT FROM AUTHOR]

Published
2008

50. Structural, Spectroscopic, and Excitonic Dynamic Characterization in Atomically Thin Yb3+‐Doped MoS2, Fabricated by Femtosecond Pulsed Laser Deposition.

Author

Maddi, Chiranjeevi, Aswin, Jyothilakshmi Ravi, Scott, Andrew, Aslam, Zabeada, Willneff, Elizabeth, Adarsh, Kumaran Nair Vasala Devi, and Jha, Animesh

Subjects
PULSED laser deposition, FEMTOSECOND lasers, OPTICAL measurements, OPTICAL devices, X-ray photoelectron spectroscopy, FUSED silica
Abstract

The large area deposition and synthesis of 10 mm × 10 mm atomically thin Yb3+‐doped MoS2 films by femtosecond pulsed laser deposition on a silica glass optical platform for device applications are demonstrated for the first time. The presence of Yb3+‐ion doping is confirmed using photoluminescence (PL), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The Yb3+‐doped MoS2 films, when excited with a 976 nm laser, exhibit room temperature PL with a peak at 1002 nm. The XPS and Raman spectroscopic analyses of the Yb3+‐doped and undoped films show that the deposited films are a mixture of 2H‐ and 1T‐MoS2 after postdeposition annealing at 500 °C. The density functional theory analysis shows that the 1T phase is metastable by +77 kJ (≈0.8 eV) mol‐1, when compared with the 2H state at 0 K. Ultrafast transient nonlinear optical spectroscopic measurements prove that the saturable absorption of undoped MoS2 is significantly modified after Yb3+‐ion doping, by displaying dopant‐host structure charge transfer. The complex transient absorption line shape shows a combination of bleach (negative) signals at the A (670 nm) and B (630 nm) exciton energies, and a strong induced absorption below the A exciton level. The results presented herein provide critical insight in designing novel rare‐earth‐ion doped 2D materials and devices. [ABSTRACT FROM AUTHOR]

Published
2019
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