Browsing by Author "Zhao, Gang"

Now showing 1 - 6 of 6
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    Advanced Bearing System for Ultra Precision Plastic Electronics Production Systems
    (Cranfield University, 2014-09) Zhao, Gang; Shore, Paul; Morantz, Paul
    The aims of this MSc research project are to investigate the application of aluminium for the main components of an ultra-precision spindle defined for use in R2R production systems and to produce a reel to reel rotary aluminium hydrostatic bearing system of high accuracy to meet the demand of manufacturing the flexible displays with an effective production capability for this special kind of film-based product. The original concept design was already finished to manufacture the bearing components and the objective of this project was to test the functionality of this new hydrostatic bearing system. Firstly, theoretical were performed to work out the output responses, including temperature rise, flow rate, load capacity etc., of the hydrostatic bearing system under different input design parameters, including supply pressure, fluid viscosity, the rotational speed etc. Then ANSYS software was used to build a FEA model to simulate the actual working conditions of the hydrostatic bearing system and to obtain the theoretical output parameters, especially the deflection conditions of the bearing shaft. Finally the experimental validation tests were conducted to verify the actual output responses to check correlation with the modelled results.
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    A comparative study of additively manufactured thin wall and block structure with Al-6.3% Cu alloy using cold metal transfer process
    (MDPI, 2017-03-10) Cong, Baoqiang; Qi, Zewu; Qi, Bojin; Sun, Hongye; Zhao, Gang; Ding, Jialuo
    In order to build a better understanding of the relationship between depositing mode and porosity, microstructure, and properties in wire + arc additive manufacturing (WAAM) 2319-Al components, several Al-6.3%Cu deposits were produced by WAAM technique with cold metal transfer (CMT) variants, pulsed CMT (CMT-P) and advanced CMT (CMT-ADV). Thin walls and blocks were selected as the depositing paths to make WAAM samples. Porosity, microstructure and micro hardness of these WAAM samples were investigated. Compared with CMT-P and thin wall mode, CMT-ADV and block process can effectively reduce the pores in WAAM aluminum alloy. The microstructure varied with different depositing paths and CMT variants. The micro hardness value of thin wall samples was around 75 HV from the bottom to the middle, and gradually decreased toward the top. Meanwhile, the micro hardness value ranged around 72–77 HV, and varied periodically in block samples. The variation in micro hardness is consistent with standard microstructure characteristics.
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    Label-free analysis of protein biomarkers using pattern-optimized graphene-nanopyramid SERS for rapid diagnosis of Alzheimer’s disease
    (American Chemical Society, 2024-04-05) Wu, Heping; Duan, Yan; Jiang, Luyue; Cao, Xinhao; Xie, Zhen; Quan, Yi; Ren, Matthew Xinhu; Wu, Shengli; Zhang, Nan; Yang, Zhugen; Zhao, Libo; Jiang, Zhuangde; Zhao, Gang; Ren, Wei; Niu, Gang
    The quantitative and highly sensitive detection of biomarkers such as Tau proteins and Aβ polypeptides is considered one of the most effective methods for the early diagnosis of Alzheimer’s disease (AD). Surface-enhanced Raman spectroscopy (SERS) detection is a promising method that faces, however, challenges like insufficient sensitivity due to the non-optimized nanostructures for specialized analyte sizes and insufficient control of the location of SERS hot spots. Thus, the SERS detection of AD biomarkers is restricted. We reported here an in-depth study of the analytical Raman enhancement factor (EF) of the wafer-scale graphene-Au nanopyramid hybrid SERS substrates using a combination of both theoretical calculation and experimental measurements. Experimental results show that larger nanopyramids and smaller gap spacing lead to a larger SERS EF, with an optimized analytical EF up to 1.1 × 1010. The hybrid SERS substrate exhibited detection limits of 10–15 M for Tau and phospho-Tau (P-Tau) proteins and 10–14 M for Aβ polypeptides, respectively. Principal component analysis correctly categorized the SERS spectra of different biomarkers at ultralow concentrations (10–13 M) using the optimized substrate. Amide III bands at 1200–1300 cm–1 reflect different structural conformations of proteins or polypeptides. Tau and P-Tau proteins are inherently disordered with a few α-helix residuals. The structure of Aβ42 polypeptides transitioned from the α-helix to the β-sheet as the concentration increased. These results demonstrate that the hybrid SERS method could be a simple and effective way for the label-free detection of protein biomarkers to enable the rapid early diagnosis of AD and other diseases.
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    Large-area and clean graphene transfer on gold-nanopyramid-structured substrates: implications for surface-enhanced Raman scattering detection
    (American Chemical Society, 2022-03-16) Wu, Heping; Niu, Gang; Ren, Wei; Yang, Zhugen; Xu, Qihang; Dai, Liyan; Jiang, Luyue; Zhai, Shijie; Zhao, Jinyan; Zhang, Nan; Zhao, Libo; Jiang, Zhuangde; Zhao, Gang
    The transfer of large-area and clean graphene to arbitrary substrates, especially to those with raised nanostructures, represents a great challenge. Polymer-based supporting layers generally lead to organic residues, while graphene transfer using alternative supporting materials like paraffin suffers from breaking and thus limits the transfer area. We demonstrated an improved poly(methyl methacrylate) (PMMA)/paraffin double layer, enabling the large-area transfer of graphene with high cleanliness and high coverage (81%) onto gold nanopyramid (AuNP)-structured substrates. The impact of supporting layers including single PMMA or paraffin and mixed PMMA/paraffin was clarified. The properties of graphene on AuNPs were theoretically and experimentally examined in detail. Raman spectra show a polarization-dependent D peak due to the folding of large-curvature graphene. The graphene on AuNPs shows a slightly tensile strain and provides extra surface-enhanced Raman scattering (SERS) with an enhancement factor of ∼20 times. These findings open a pathway to extend the applications of transferred graphene on raised nanostructures in many fields, such as SERS detection, catalysis, biosensors, light-emitting diodes, solar cells, and advanced transparent conductors.
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    Microstructure and mechanical properties of double-wire + arc additively manufactured Al-Cu-Mg alloys
    (Elsevier, 2017-12-16) Qi, Zewu; Cong, Baoqiang; Qi, Bojin; Sun, Hongye; Zhao, Gang; Ding, Jialuo
    As the properties of wire + arc additively manufactured Al-6.3Cu alloy cannot meet the applying requirements, a double-wire + arc additive manufacturing system was built to add magnesium into Al-Cu deposits for higher mechanical properties. Two commercial binary wires aluminum-copper ER2319 and aluminum-magnesium ER5087 were chosen as the filler metal to build Al-Cu-Mg components with different compositions by adjusting the wire feed speed. The microstructure and morphology of thin wall samples were characterized by optical micrographs (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Vickers hardness and tensile properties were investigated. The microstructure of Al-Cu-Mg deposits was mainly composed of coarse columnar grains and fine equiaxed grains with non-uniformly distributing characteristics. With higher Cu but lower Mg content, the strengthen phase turned to Al2Cu + Al2CuMg from Al2CuMg, and the micro hardness presented an increasing trend. The isotropic characteristics of ultimate tensile strength (UTS), yield strength (YS) and elongation were revealed in these samples. The UTS was about 280 ± 5 MPa both in horizontal and vertical directions for all samples. The YS showed an increasing trend from 156 MPa to 187 MPa with the same content trend, while elongation decreased from 8.2% to 6%. The fractographs exhibited typical brittle fracture characteristics.
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    Microstructure and mechanical properties of wire + arc additively manufactured 2024 aluminum alloy components: As-deposited and post heat-treated
    (Elsevier, 2019-03-09) Qi, Zewu; Qi, Bojin; Cong, Baoqiang; Sun, Hongye; Zhao, Gang; Ding, Jialuo
    Restricted by the type of commercial aluminum wire, 2024 aluminum alloy cannot be built through conventional single wire + arc additive manufacturing technology. By simultaneously feeding two wires (ER2319 and ER5087) and adjusting the wire feed speed, 2024 aluminum alloy deposits can be achieved with double - wire + arc additive manufacturing process. Heat treatment procedures (solution + natural/artificial aging) were conducted for further improving the properties. The microstructure and mechanical properties of as-deposited and heat-treated 2024 aluminum alloy deposits were tested and analyzed. The microstructure differed in different conditions. Obvious dendrite morphology in as-deposited condition disappeared after heat treatment, and the phases turned to be α-Al + Al2Cu from α-Al + Al2Cu + Al2CuMg. After heat treatment, layer distributing characteristics of the phases became obvious. Post-deposition heat treatment can improve the micro hardness, strength and horizontal elongation of WAAM 2024 aluminum alloy deposits. The elongation along vertical direction decreased.