Browsing by Author "Zhang, W"

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    Phase transition enhanced thermoelectric performance in Cu2Se
    (Australian Institute of Physics, 2014-02-06) Liu, H; Shi, X; Zhang, W; Chen, L; Danilkin, SA
    Worldwide efforts to searching for good thermoelectric materials are frequently focusing on normal phases in crystalline semiconductors. The material’s thermoelectric performance is described the parameter of figure of merit, zT, which is around unity around room temperature and above 1.5 at high temperatures. In the Cu2Se with anti-fluorite structure above 400K, Se atoms form a rigid face-centred cubic lattice, while the copper ions are highly disordered or moving around the tetrahedral voids with liquid-like mobility, resulting in an extraordinarily low lattice thermal conductivity, which enables zT up to 1.5 at 1,000K. Here, we report significantly enhanced thermoelectric performance during the phase transitions in Cu2Se and iodine doped Cu2Se. It is showed that the critical electron and phonon scattering greatly improve the thermopower and strongly reduce the thermal coductivity, leading to the improvement in the figure of merit more than 3-7 times compared to the normal phases, and achieving zT value of 2.3 at 400K. This mechanism pave a new way to increase the figure of merit of thermoelectric materials, and expend the utility of thermoelectrics in electronic cooling industry.z
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    Phase-oriented surface segregation in an aluminium casting alloy
    (Elsevier, 2009-02-15) Nguyen, CL; Atanacio, AJ; Zhang, W; Prince, KE; Hyland, MM; Metson, JB
    There have been many reports of the surface segregation of minor elements, especially Mg, into surface layers and oxide films on the surface of Al alloys. LM6 casting alloy (Al–12%Si) represents a challenging system to examine such segregation as the alloy features a particularly inhomogeneous phase structure. The very low but mobile Mg content (approximately 0.001 wt.%), and the surface segregation of modifiers such as Na, mean the surface composition responds in a complex manner to thermal treatment conditions. X-ray photoelectron spectroscopy (XPS) has been used to determine the distribution of these elements within the oxide film. Further investigation by dynamic secondary ion mass spectrometry (DSIMS) confirmed a strong alignment of segregated Na and Mg into distinct phases of the structure. © 2009, Elsevier Ltd.
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    Transforming spirulina maxima biomass into ultrathin bioactive coatings using an atmospheric plasma jet: a new approach to healing of infected wounds
    (Wiley, 2023-09-15) Pham, T; Nguyen, TT; Nguyen, NH; Hayles, A; Li, WS; Pham, DQ; Nguyen, CK; Nguyen, T; Vongsvivut, JP; Ninan, N; Sabri, YM; Zhang, W; Vasiliev, K; Truong, VK
    The challenge of wound healing, particularly in patients with comorbidities such as diabetes, is intensified by wound infection and the accelerating problem of bacterial resistance to current remedies such as antibiotics and silver. One promising approach harnesses the bioactive and antibacterial compound C-phycocyanin from the microalga Spirulina maxima. However, the current processes of extracting this compound and developing coatings are unsustainable and difficult to achieve. To circumvent these obstacles, a novel, sustainable argon atmospheric plasma jet (Ar-APJ) technology that transforms S. maxima biomass into bioactive coatings is presented. This Ar-APJ can selectively disrupt the cell walls of S. maxima, converting them into bioactive ultrathin coatings, which are found to be durable under aqueous conditions. The findings demonstrate that Ar-APJ-transformed bioactive coatings show better antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, these coatings exhibit compatibility with macrophages, induce an anti-inflammatory response by reducing interleukin 6 production, and promote cell migration in keratinocytes. This study offers an innovative, single-step, sustainable technology for transforming microalgae into bioactive coatings. The approach reported here has immense potential for the generation of bioactive coatings for combating wound infections and may offer a significant advance in wound care research and application. © 2023 The Authors. Small published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License.
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    Vortex fluidic induced mass transfer across immiscible phases
    (Royal Society of Chemistry, 2022-01-31) Jellicoe, M; Igder, A; Chuah, C; Jones, DB; Luo, X; Stubbs, KA; Crawley, EM; Pye, SJ; Joseph, N; Vimalananthan, K; Gardner, Z; Harvey, DP; Chen, XJ; Salvemini, F; He, S; Zhang, W; Chalker, JM; Quinton, JS; Tang, YH; Raston, CL
    Mixing immiscible liquids typically requires the use of auxiliary substances including phase transfer catalysts, microgels, surfactants, complex polymers and nano-particles and/or micromixers. Centrifugally separated immiscible liquids of different densities in a 45° tilted rotating tube offer scope for avoiding their use. Micron to submicron size topological flow regimes in the thin films induce high inter-phase mass transfer depending on the nature of the two liquids. A hemispherical base tube creates a Coriolis force as a ‘spinning top’ (ST) topological fluid flow in the less dense liquid which penetrates the denser layer of liquid, delivering liquid from the upper layer through the lower layer to the surface of the tube with the thickness of the layers determined using neutron imaging. Similarly, double helical (DH) topological flow in the less dense liquid, arising from Faraday wave eddy currents twisted by Coriolis forces, impact through the less dense liquid onto the surface of the tube. The lateral dimensions of these topological flows have been determined using ‘molecular drilling’ impacting on a thin layer of polysulfone on the surface of the tube and self-assembly of nanoparticles at the interface of the two liquids. At high rotation speeds, DH flow also occurs in the denser layer, with a critical rotational speed reached resulting in rapid phase demixing of preformed emulsions of two immiscible liquids. ST flow is perturbed relative to double helical flow by changing the shape of the base of the tube while maintaining high mass transfer between phases as demonstrated by circumventing the need for phase transfer catalysts. The findings presented here have implications for overcoming mass transfer limitations at interfaces of liquids, and provide new methods for extractions and separation science, and avoiding the formation of emulsions. © 2022 The Author(s). Published by the Royal Society of Chemistry. Open Access CC BY.