ANSTO :: Browsing by Author "Wang, J"

Browsing by Author "Wang, J"

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Anomalous time-decay in neutron depolarization by high-Tc superconductors
(Australian and New Zealand Institutes of Physics, 1994-11-09) Miles, PA; Kennedy, SJ; Taylor, KNR; Russell, GJ; Wang, J; Gu, GD; Takamara, K; Koshizuka, N
In studies of the- field and time dependence of the polarisation state of a polarised neutron beam transmitted through single crystals of YBa2Cu- (YBCO) and BI2Sr2CaCu202-6 (BSCCO), we have observed some unusual behaviour for temperatures > 60*K for YBCO and 30>T>40K. The observed results suggest that at these temperatures, after removing an external magnetic field, the trapped flux density seen by the neutrons is essentially zero for all time less than = 200msecs. With increasing tune, the sampled flux density increases in magnitude, reaching the values observed in long time (20secs) measurements only after a delay of several seconds. At this time, the trapped flux density reaches a maximum and subsequently decays logarithmically at a rate determined by the effective pinning energy U(H,T). Possible mechanisms responsible for the inverse flux decay are considered. Large anisotropy in this behaviour is observed with the effect not being observed at all with Hlab for BSCCO and no marked temperature onset with YBCO with Hlab. For both YBCO and BSCCO the Hjfc observed flux decay show this behaviour. We conclude that the observed results follow, not from a change in the magnitude of the trapped flux, but rather from a change in the flux distribution within the sample. We interpret this in terms of a domain structure in the flux lattice system which is associated with the fringing closure flux which remains once the external applied field is removed.
Arginine catabolism is essential to polymyxin dependence in Acinetobacter baumannii
(Elsevier, 2024-07) Han, ML; Alsaadi, Y; Zhao, JX; Zhu, Y; Lu, J; Jiang, X; Ma, W; Patil, NA; Dunstan, RA; Le Brun, AP; Wickremasinghe, H; Hu, X; Wu, Y; Yu, HH; Wang, J; Barlow, CK; Bergen, PJ; Shen, HH; Lithgow, T; Creek, DJ; Velkov, T; Li, J
Polymyxins are often the only effective antibiotics against the "Critical" pathogen Acinetobacter baumannii. Worryingly, highly polymyxin-resistant A. baumannii displaying dependence on polymyxins has emerged in the clinic, leading to diagnosis and treatment failures. Here, we report that arginine metabolism is essential for polymyxin-dependent A. baumannii. Specifically, the arginine degradation pathway was significantly altered in polymyxin-dependent strains compared to wild-type strains, with critical metabolites (e.g., L-arginine and L-glutamate) severely depleted and expression of the astABCDE operon significantly increased. Supplementation of arginine increased bacterial metabolic activity and suppressed polymyxin dependence. Deletion of astA, the first gene in the arginine degradation pathway, decreased phosphatidylglycerol and increased phosphatidylethanolamine levels in the outer membrane, thereby reducing the interaction with polymyxins. This study elucidates the molecular mechanism by which arginine metabolism impacts polymyxin dependence in A. baumannii, underscoring its critical role in improving diagnosis and treatment of life-threatening infections caused by "undetectable" polymyxin-dependent A. baumannii. ª 2024 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC licence
A correlated electron diffraction, in situ neutron diffraction and dielectric properties investigation of poled (1-x)Bi0.5Na0.5TiO3-xBaTiO3 ceramics
(American Institute of Physics, 2011-10-15) Wang, J; Liu, Y; Withers, RL; Studer, AJ; Li, Q; Norén, L; Guo, YP
A correlated electron diffraction, temperature-dependent in situ neutron diffraction, and temperature-dependent dielectric properties investigation of poled (1-x)Bi(0.5)Na(0.5)TiO(3)-xBaTiO(3) (BNTBT100x) (x = 0.04, 0.07, and 0.12) samples has been carried out. The results show that the depolarization temperature, T(d), of the rhombohedral BNTBT 4 sample is associated with the disappearance of G +/- 1/2 [111]*(p) satellite reflections and a(-)a(-)a(-) octahedral tilting while that of the BNTBT 12 sample is associated with a metrically tetragonal to metrically cubic or pseudo-cubic symmetry. In the case of the poled BNTBT 7 sample in the MPB region, the dielectric properties show a quite distinct two stage transition from a room temperature clearly metrically tetragonal phase again to a metrically cubic or pseudo-cubic symmetry above 150 degrees C. There is no apparent change in its average structure in vicinity of T(d) in BNTBT 7. Electron diffraction shows the presence of considerable octahedral tilt twin disorder in all three samples. (C) 2011 American Institute of Physics.
Disorder-induced spin-liquid-like behavior in kagome-lattice compounds
(American Physical Society (APS), 2020-12-15) Ma, Z; Dong, ZY; Wu, S; Zhu, Y; Bao, S; Cai, Z; Wang, W; Shangguan, Y; Wang, J; Ran, K; Yu, DH; Deng, GC; Mole, RA; Li, HF; Yu, SL; Li, JX; Wen, JS
Quantum spin liquids (QSLs) are an exotic state of matter that is subject to extensive research. However, the relationship between the ubiquitous disorder and the QSL behaviors is still unclear. Here, by performing comparative experimental studies on two kagomé-lattice QSL candidates, Tm3Sb3Zn2O14 and Tm3Sb3Mg2O14, which are isostructural to each other but with strong and weak structural disorder, respectively, we show unambiguously that the disorder can induce spin-liquid-like features. In particular, both compounds show dominant antiferromagnetic interactions with a Curie-Weiss temperature of -17.4 and -28.7 K for Tm3Sb3Zn2O14 and Tm3Sb3Mg2O14, respectively, but remain disordered down to about 0.05 K. Specific-heat results suggest the presence of gapless magnetic excitations characterized by a residual linear term. Magnetic excitation spectra obtained by inelastic neutron scattering (INS) at low temperatures display broad continua. All these observations are consistent with those of a QSL. However, we find in Tm3Sb3Zn2O14, which has strong disorder resulting from the random mixing of the magnetic Tm3+ and nonmagnetic Zn2+, that the low-energy magnetic excitations observed in the specific-heat and INS measurements are substantially enhanced compared to those of Tm3Sb3Mg2O14, which has much less disorder. We believe that the effective spins of the Tm3+ ions in the Zn2+/Mg2+ sites give rise to the low-energy magnetic excitations, and the amount of the occupancy determines the excitation strength. These results provide direct evidence of the mimicry of a QSL caused by disorder. ©2020 American Physical Society.
Effect of electric field and temperature on average structure and domain wall motion in 0.93Bi(0.5)Na(0.5)TiO(3)-0.07BaTiO(3) ceramic
(Hindawi Publishing Corporation, 2013-06-24) Wang, J; Liu, Y; Studer, AJ; Norén, L; Withers, RL
In situ neutron powder diffraction patterns and dielectric spectra of 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 ceramic were investigated under different electrical fields and temperatures. An electric-field-induced phase transition from metrically cubic to metrically tetragonal, associated with strong domain wall motion, occurs. Such induced phase and domain wall motion are unchanged until the high-temperature phase transition occurs from metrically tetragonal to metrically cubic. All these changes are irrelevant to the observed depolarization temperature (75°C). The depolarization behaviour is thus suggested to be associated with the local structure caused by the octahedral tilt twinning disorder. © 2013, Jian Wang et al.
Evaluation on nuclear emergency response strategies in the Asia-Pacific region
(Elsevier B. V., 2021-09) Li, F; Wang, J; Li, H; Hu, Q; Dan, WX; Ge, LQ; Cohen, DD
The safe use of nuclear energy has always been one of the vital factors hindering the development of nuclear energy. Especially after the Chernobyl Disaster in 1986 and the Fukushima nuclear power plant accident in 2011, the attitude of the government and the public towards the safe handling of nuclear power has become increasingly negative. International discussions on the emergency decision of nuclear accidents have never ceased, and the process of dealing with the accidents’ aftermath is still difficult. Therefore, it is worth researching on the trend, effectiveness and perfection of the nuclear emergency response strategies issued by the government. This article selected the Asia-Pacific region as the research object, deeply reviewed the optimization policy and management of Australia, China, Thailand, Russia and other countries since 1953. With the constantly innovation of nuclear technology, this work is of great significance to formulate relevant policies and to improve the global nuclear emergency response strategies in the future. © 2021 Elsevier B.V.
Investigation into heat treatment and residual stress in laser clad AA7075 powder on AA7075 substrate
(Springer US, 2013-06-04) Cottam, R; Luzin, V; Liu, Q; Wong, YC; Wang, J; Brandt, M
The laser cladding of AA7075 powder onto a AA7075 substrate was conducted to evaluate the effect of heat treatment and to measure residual stress between the clad layer and substrate to better understand the effect of laser cladding. The microstructure formed in the clad region was characteristic of a high cooling rate, which is typical for laser cladding. The heat-affected zone (HAZ) showed coarser precipitates when compared with the substrate and was attributed to the heating from the laser. A solution heat treatment followed by aging was employed to restore the strength in the HAZ. Nanohardness traverses of the clad and substrate was performed and it was shown the hardness in the 7075 clad layer was lower than the substrate both pre- and post-heat treatment and was attributed to the vaporization of zinc and magnesium. Neutron diffraction was employed to measure the residual stress both before and after heat treatment. The residual stresses formed in the clad layer were tensile and about 50 MPa in magnitude; heat treatment increased the stress level to approximately 100 MPa. © 2013, Springer.
Local microstructure evolution of local microstructure evolution of bismuth sodium titanate-based lead-free piezoelectric systems across the morphotropic phase boundary region
(World Scientific Publishing Co, 2012-09-12) Liu, Y; Withers, RL; Wang, J; Norén, L; Studer, AJ; Li, YX
Morphotropic phase boundary (MPB) containing piezoelectric systems generally exhibit enhanced piezoelectric performance at compositions within, or close to, the MPB region. The mechanism/s underlying such enhancement, however, are still contentious due to complex micro/nanostructure and apparently inherent local structural variability associated with octahedral tilt disorder/platelet precipitates in such piezoelectric materials. This paper reviews some recent structural analysis results from Bi0.5Na0.5TiO3 (BNT) and other binary, lead-free, piezoelectric materials systems derived from it via electron diffraction and in situ neutron diffraction. The results suggest that intrinsically existing local microstructure (LMS) in BNT essentially continues across the MPB region. The LMS, originating from inherent octahedral tilt disorder, is strongly temperature-, electric field-, pressure- and chemical composition-dependent, and may help to explain a series of phenomena observed in BNT-based binary materials systems, including the enhanced piezoelectric effect in the region of the MPB. © 2012 World Scientific Publishing Co.
Phase behaviour and aggregate structures of the surface-active ionic liquid [BMIm][AOT] in water
(Elsevier B.V., 2023-12-15) Zhang, YX; Marlow, JB; Wood, K; Wang, J; Warr, GG; Li, H; Atkin, R
Hypothesis: The surface-active ionic liquid, 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate ([BMIm][AOT]), has a sponge-like bulk nanostructure consisting of percolating polar and apolar domains formed by the ion charge groups and alkyl chains, respectively. We hypothesise that added water will swell the polar domains and change the liquid nanostructure. Experiments: Small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and polarizing optical microscopy (POM) were used to investigate the nanostructure of [BMIm][AOT] as a function of water content. Differential scanning calorimetry (DSC) was employed to probe the thermal transitions of [BMIm][AOT]-water mixtures and the mobility of water molecules. Findings: SAXS, SANS and POM show that at lower water contents, [BMIm][AOT]-water mixtures have a sponge-like nanostructure similar to the pure SAIL, at medium water contents a lamellar phase forms, and at high water contents vesicles form. DSC results reveal that water molecules are supercooled in the lamellar phase. For the first time, results reveal a series of transitions from inverse sponge, to lamellar then to vesicles, for [BMIm][AOT] upon dilution with water. © 2023 Elsevier Inc.
Residual stress measurements of lean duplex stainless steel welded sections
(Elsevier, 2021-08-08) Li, DX; Paradowska, AM; Uy, B; Wang, J; Proust, G; Azad, SK; Huang, YR
Lean duplex stainless steel (LDSS) has been increasingly utilised in engineering applications due to its excellent durability, corrosion resistance, as well as superior structural and economic benefits. Moreover, compared to cold-form sections, welded members have significant structural advantages, and thus, have been widely used in many engineering practices. However, as one of the key factors affecting the performance of structural components, residual stresses of LDSS welded sections have not been sufficiently investigated. Therefore, square and H-shaped LDSS welded sections were considered in the present experimental programme. Accurate measurements of the tensile and compressive residual stresses were conducted through the non-destructive neutron diffraction method. As LDSS is a dual-phase material, neutron diffraction measurement was repeated twice for each specimen to obtain the individual phase residual stresses (ferrite-phase, α and austenite-phase, γ). Hardness analysis, as well as microstructural characterisation using optical microscopy and electron backscatter diffraction (EBSD) were thereafter performed to ascertain the volume fraction of each phase, based on which the residual stresses along the direction of interest were successfully converted. According to the obtained experimental results, the authors recommended analytical models for the LDSS fabricated square sections and proposed new models for the H-sections, through which the residual stress distributions for welded LDSS sections can be accurately predicted. In addition, the recommended/proposed analytical models for LDSS sections were further compared with their counterparts previously developed for high-strength steel (HSS) and ultra-high-strength steel (UHSS) welded sections. © 2021 Elsevier Ltd
Residual stresses of box and I-shaped columns fabricated from S960 ultra-high-strength steel
(Elsevier B. V., 2019-12-24) Li, DX; Paradowska, AM; Uy, B; Wang, J; Khan, M
Ultra-high-strength steel (UHSS) with a nominal yield stress of 960 MPa is of significant interest for the design of heavily loaded compressive members, such as high-rise buildings, long-span bridges and large-scale infrastructure. However, the residual stresses induced by the fabrication process can be detrimental to the structural members. In particular, compressive residual stresses can result in premature buckling and the ultimate strength of fabricated columns will be reduced. To date, research pertaining to the distribution of the residual stresses for UHSS column is limited. An experimental program about the measurements of residual stress distributions for UHSS box and I-shaped columns is therefore presented herein. Measurements of residual stress were undertaken on two box and two I-shaped columns having various width-to-thickness ratios by using the non-destructive neutron diffraction method. The distributions of residual stress in three orthogonal directions for each specimen was measured. The influences of column width-to-thickness ratio on residual stress distributions were investigated and discussed. In addition, simplified analytical models for the box and I-shaped column were established to facilitate the buckling analysis for such UHSS columns. Comparisons of the residual stress distributions between the experimental results and analytical model demonstrated a good agreement and this model can be safely used for the fabricated high-strength-steel (HSS) and UHSS column. Crown Copyright © 2019 Published by Elsevier Ltd
The role of microstructural characteristics in the cavitation erosion behaviour of laser melted and laser processed nickel–aluminium bronze
(Elsevier, 2014-09-01) Cottam, R; Luzin, V; Moody, H; Edwards, DP; Majumdar, A; Wong, YC; Wang, J; Brandt, M
In this study two types of laser surface treatment, laser surface melting and laser processing, were used to treat the surface of as cast Nickel–Aluminium Bronze. The two treatments were then subjected to cavitation erosion testing and were compared against as-cast Nickel–Aluminium Bronze. While the cavitation performance of the two types of laser surface treatment was equivalent, the morphology of the eroded surfaces was different. Several materials characterisation techniques including neutron diffraction for residual stress measurements and SEM were used to explain why the two eroded surfaces were different. It was found that the tensile residual stresses in the laser melted sample weakened the sample, which negated its superior strength when compared with the laser processed sample. It was also observed that the erosion and pitting in the laser melted sample were deeper and they were attributed to the tensile residual stresses accelerating the attack at grain boundaries. © 2014, Elsevier B.V.
The role of microstructure in the stress relaxation and tempering of laser clad Ti–6Al–4V
(Elsevier, 2014-04-17) Cottam, R; Luzin, V; Liu, Q; Mayes, E; Wong, YC; Wang, J; Brandt, M
In this work a heat treatment procedure was performed on laser clad Ti–6Al–4V, which resulted in a reduction of tensile residual stresses in the clad samples as well and a decrease in the hardness of the clad layer with an increasing heat treatment time. The reduction in the residual stress was attributed to inter-phase stress relaxation brought about by the growth of the β phase. The reduction in hardness was attributed to an increase in the volume fraction of the soft β phase. Both the reduction in residual stress and hardness due to this heat treatment makes it an attractive method to heat treat both laser clad and additively manufactured Ti–6Al–4V components for improved mechanical properties.© 2014, Elsevier B.V.
Structural transitions in [001]/[111]-oriented 0.26Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals probed via neutron diffraction and electrical characterization
(AIP Publishing LLC, 2013-04-19) Li, Q; Liu, Y; Wang, J; Studer, AJ; Withers, RL; Li, ZR; Xu, Z
We report changes in the metric symmetry of unpoled and electrically poled single crystals of 0.26Pb(In1/2 Nb 1/2)O3-0.46Pb(Mg1/3 Nb 2/3)O3-0.28PbTiO3, as revealed by neutron diffraction in conjunction with electrical measurements. The unpoled crystals show relaxor characteristics and an average rhombohedral symmetry that persists from ambient temperature up to the Curie temperature of ∼165 °C. Poling along a [111] direction enhances the rhombohedral distortion away from cubic metric symmetry but appears not to induce any monoclinic phases. By contrast, the poled [001]-oriented crystal has orthorhombic (or monoclinic MC ) metric symmetry at 25 °C. An intermediate transition to a metrically tetragonal phase around 120 °C is confirmed for both poled crystals. © 2013, AIP Publishing LLC.

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