Browsing by Author "Zhang, SY"
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- ItemEffects of ausforming temperature on bainite transformation, microstructure and variant selection in nanobainite steel(Pergamon-Elsevier Science Ltd., 2013-06-01) Gong, W; Tomota, Y; Adachi, Y; Paradowska, AM; Kelleher, JF; Zhang, SYThe bainite transformation behavior after plastic deformation of austenite, i.e., ausforming was studied by in situ neutron diffraction and ex situ experiments, and the effects of ausforming temperature was made clear. Ausforming, at a low temperature (573 K) was found to accelerate bainite transformation and produce a characteristic microstructure, whereas at a high temperature (873 K), ausforming had little influence. The reason for the different results stems from the dislocation structure introduced in austenite; planar dislocations remaining on the active slip planes are believed to assist bainite transformation, accompanied by strong variant selection. The variant selection rule that focuses on Shockley partial dislocation was verified from electron backscatter diffraction results. © 2013, Elsevier Ltd.
- ItemThe formation of defect-pairs for highly efficient visible-light catalysts(Wiley, 2017-01-23) Sun, QB; Cortie, DL; Zhang, SY; Frankcombe, TJ; She, GW; Gao, J; Sheppard, LR; Hu, WB; Chen, H; Zhuo, SJ; Chen, DH; Withers, RL; McIntyre, GJ; Yu, DH; Shi, WS; Liu, YHighly efficient visible-light catalysts are achieved through forming defect-pairs in TiO2 nanocrystals. This study therefore proposes that fine-tuning the chemical scheme consisting of charge-compensated defect-pairs in balanced concentrations is a key missing step for realizing outstanding photocatalytic performance. This research benefits photocatalytic applications and also provides new insight into the significance of defect chemistry for functionalizing materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemHigh-resolution strain mapping through time-of-flight neutron transmission diffraction(Trans Tech Publications, 2013-11-21) Tremsin, AS; McPhate, JB; Vallerga, JV; Siegmund, OHW; Kockelmann, W; Paradowska, AM; Zhang, SY; Kelleher, JF; Steuwer, A; Feller, WBThe spatial resolution of time of flight neutron transmission diffraction was recently improved by the extension of photon/electron counting technology to imaging of thermal and cold neutrons. The development of novel neutron sensitive microchannel plates enables neutron counting with spatial resolution of ~55 um and time-of-flight accuracy of ~1 us, with efficiency as high as 70% for cold and ~40% for thermal neutrons. The combination of such a high resolution detector with a pulsed collimated neuron beam provides the opportunity to obtain a 2-dimensional map of neutron transmission spectra in one measurement. The results of our neuron transmission measurements demonstrate that maps of strains integrated along the beam propagation direction can be obtained with ~100 microstrain accuracy and spatial resolution of ~100 um providing there are sufficient neutron events collected. In this paper we describe the capabilities of the MCP neutron counting detectors and present the experimental results of 2-dimensional strain maps within austenitic steel compact tension (CT) crack samples measured at the ENGIN-X beamline of the ISIS pulsed neutron source. © 2014, Trans Tech Publications.
- ItemHighly efficient visible light catalysts driven by Ti3+-VO-2Ti4+-N3− defect clusters(Wiley, 2018-10-13) Sun, QB; Zhang, SY; Cortie, DL; Langley, J; Cox, N; Frankcombe, TJ; Gao, J; Chen, H; Withers, RL; Kremer, F; Yu, DH; Brink, F; Shi, WS; Liu, YLocal defect structures play significant roles on material properties, but they are seriously neglected in the design, synthesis, and development of highly efficient TiO2-based visible light catalysts (VLCs). Here, we take anatase TiO2 nanocrystals that contain (Ti3+, N3−) ions and have the complicated chemical formula of (Ti1-x4+Tix3+)(O2-2-y-zNy3-□z) as an example, and point out that the formation of Ti3+-VO-2Ti4+-N3− local defect clusters is a key missing step for significantly enhancing VLC properties of host TiO2 nanocrystals. Experimental and theoretical investigations also demonstrate the emergent behaviors of these intentionally introduced defect clusters for developing highly efficient VLCs. This research thus not only provides highly efficient visible light catalysts for various practical applications but also addresses the significance of local defect structures on modifying material properties. © 2019 Wiley-VCH Verlag GmbH & Co.
- ItemHighly efficient visible light catalysts driven by Ti3+‐VO‐2Ti4+‐N3− defect clusters(Wiley, 2018-10-13) Sun, QB; Zhang, SY; Cortie, DL; Langley, J; Cox, N; Frankcombe, TJ; Gao, J; Chen, H; Withers, RL; Kremer, F; Yu, DH; Brink, F; Shi, WS; Liu, YLocal defect structures play significant roles on material properties, but they are seriously neglected in the design, synthesis, and development of highly efficient TiO2‐based visible light catalysts (VLCs). Here, we take anatase TiO2 nanocrystals that contain (Ti3+, N3−) ions and have the complicated chemical formula of ()(□z) as an example, and point out that the formation of Ti3+‐VO‐2Ti4+‐N3− local defect clusters is a key missing step for significantly enhancing VLC properties of host TiO2 nanocrystals. Experimental and theoretical investigations also demonstrate the emergent behaviors of these intentionally introduced defect clusters for developing highly efficient VLCs. This research thus not only provides highly efficient visible light catalysts for various practical applications but also addresses the significance of local defect structures on modifying material properties. © 1999-2024 John Wiley & Sons, Inc or related companies.
- ItemInvestigation of microstructure within metal welds by energy resolved neutron imaging(IOP Publishing, 2016-01-01) Tremsin, AS; Kockelmann, W; Paradowska, AM; Zhang, SY; Korsunsky, AM; Shinohara, T; Feller, WB; Lehmann, EHThe recent development of bright pulsed neutron sources and high resolution neutron counting detectors enables simultaneous acquisition of a neutron transmission spectrum for each pixel of the image. These spectra can be used to reconstruct microstructure parameters within welds, such as strain, texture and phase composition through Bragg edge analysis, and in some cases elemental composition through resonance absorption analysis. In this paper we demonstrate the potential of energy-resolved neutron imaging to study the microstructures of two steel welds, where the spatial distribution of residual strain within the welds, as well as some information on the texture, are obtained with sub-mm spatial resolution. A friction stir weld of two steel plates and a conventional weld of two steel pipes were studied at pulsed neutron facilities, where a Δλ/λ resolution as low as 0.2% can be attained over a wide range of neutron wavelengths ranging from 0.5 Å to 8 Å. Creative Commons Attribution 3.0 licence © Copyright 2021 IOP Publishing
- ItemMechanical properties of tungsten copper composites: direct measurement by neutron diffraction(Australian Institute of Physics, 2014-02-04) Mignone, PJ; Finlayson, TR; Kabra, S; Zhang, SY; Franks, GV; Riley, DPThe composite W-10 wt%Cu (19.35% by volume, assuming negligible porosity) has been studied using the ENGIN-X beamline at the ISIS pulsed neutron source at the Rutherford Appleton Laboratory. An as-machined, compression sample was initially measured in order to check for the presence of residual stresses in the composite, using a mixed powder sample of the same elemental weight fractions as the “zero stress” comparison. Then a series of mechanical tests were carried out on the composite for applied compressive loads up to 250 MPa at both room temperature and 100ºC and compared with similar tests carried out on pure tungsten and copper samples. Residual stress values of -280 MPa (for the tungsten matrix) and 480 MPa (for the copper particulate phase) were measured for the as-machined sample. This is a surprising result, given that the yield stress for copper is typically less than 100 MPa but is not inconsistent with residual stresses reported in the literature for W-Cu composites. The mechanical properties for the composite have also been determined from the results of these in-situ, mechanical tests and compared with finite element calculations based on microstructural models for the composite material.
- ItemModern and historical engineering components investigated by neutron diffractionon ENGIN-X(Japan Society of Mechanical Engineers, 2012-06-29) Paradowska, AM; Tremsin, AS; Kelleher, JF; Zhang, SY; Paddea, S; Burca, G; James, JA; Ahmed, R; Faisal, NH; Festa, G; Andreani, C; Civita, F; Bouchard, PJ; Krockelman, W; Fitzpatrick, ME; Grazzi, FThe ENGIN-X beamline is mainly used to determine residual strains/stresses deep within the interior of bulk engineering components. It is mainly used by scientists and engineers for the development of modern engineering processes and structural integrity investigations. ENGIN-X diffraction and transmission mode can be a very useful tool to measure strain, phase transitions, texture and material composition in spatial resolution in historical or archaeological artifacts and modern materials. The complexity of the shapes and sizes of the samples measured on ENGIN-X varies significantly between experiments, and this required the development of better planning, simulation and control software, SScanSS. In this paper an overview of recent developments in strain scanning on ENGIN-X and a highlight of current scientific research are presented. © 2012 The Japan Society of Mechanical Engineers
- ItemValidation of predicted residual stresses within direct chill cast magnesium alloy slab(Springer, 2012-05-01) Turski, M; Paradowska, AM; Zhang, SY; Mortensen, D; Fjaer, H; Grandfield, J; Davis, B; DeLorme, RA significant level of cold cracking has been observed within direct chill (DC) cast, high-strength magnesium alloy Elektron WE43. These cracks have been attributed to the formation of significant residual stresses during casting. A finite-element modeling (FEM) code, which is called ALSIM, has been used to predict the residual stress within the DC-cast slab. Verification of the predicted residual stress field within an 870 × 315-mm sized slab has been carried out using neutron diffraction measurements. Given that measurements in such large-scale components using diffraction measurements are particularly challenging and expensive, the efficient use of neutron diffraction measurements is emphasized. This has included the use of sectioning, allowing the residual stress within the slab to be mapped in detail. © 2012, Springer.